Patent Publication Number: US-9413251-B2

Title: Power delivery device, AC adapter, electronic apparatus and power delivery system, having variable function of output voltage value and available output current capacity

Description:
CROSS REFERENCE TO RELATED APPLICATIONS AND INCORPORATION BY REFERENCE 
     This application is based upon and claims the benefit of priority from prior Japanese Patent Application Nos. P2013-004909 filed on Jan. 15, 2013, P2013-034509 filed on Feb. 25, 2013, and P2013-035321 filed on Feb. 26, 2013, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to a Power Delivery (PD) device, an Alternating-Current (AC) adapter, an electronic apparatus, and a Power Delivery (PD) system. The present invention relates in particular to a PD device, an AC adapter, an electronic apparatus, and a PD system each which have a variable function of an output voltage value and an available output current capacity (MAX value). 
     BACKGROUND ART 
     Conventionally, there have been provided Direct Current (DC) power sockets which can intercommunicate between terminal devices and power line carrier communication networks supporting telecommunications standards with a power delivery (Refer to Patent Literature 1, for example.). 
     There are Power over Ethernet (PoE) technology and Universal Serial Bus (USB) technology as a power delivery technology using data lines (Refer to Non Patent Literature 1, for example.). 
     As the USB technologies, there are USB 2.0 Standard up to maximum supply power of 2.5 W, USB 3.0 Standard up to maximum supply power of 4.5 W, and Battery Charging Standard (BCS) Revision 1.2 up to maximum supply power of 7.5 W according to the power delivery level. 
     A USB Power Delivery (USB PD) Specification Revision 1.0 is compatible with existing cables and existing connectors, and coexists also with the USB 2.0 Standard, the USB 3.0 Standard, and the USB Battery Charging Standard (BCS) Revision 1.2. In such a standard, values of the charging current and voltage is selectable within a range of voltage 5V-12V-20V and a range of current 1.5 A-2 A-3 A-5 A, and the USB electric charging and power transmission can be achieved to be 10 W, 18 W, 36 W, 65 W, and the maximum of 100 W. 
     DC/DC converters have been used as a power source for achieving such a power delivery. There are a diode rectification system and a synchronous rectification method in the DC/DC converters. 
     CITATION LIST 
     
         
         Patent Literature 1: Japanese Patent Application Laying-Open Publication No. 2011-82802 
         Non-Patent Literature 1: “Special Edition: Power Delivery with Data Lines”, Nikkei Electronics, Oct. 9, 2012, pp. 23-40 
       
    
     SUMMARY OF THE INVENTION 
     Technical Problem 
     The object of the present invention is to provide a PD device, an AC adapter, an electronic apparatus, and a PD system each which can control a variable function of an output voltage value and an available output current capacity (MAX value). 
     Solution to Problem 
     According to one aspect of the present invention, there is provided a power delivery device comprising: a DC/DC converter disposed between an input and an output; a primary-side controller configured to control an input current of the DC/DC converter; and a secondary-side controller connected with AC coupling to the output, the secondary-side controller configured to feed back electric power information of the output to the primary-side controller, wherein the primary-side controller varies an output voltage value and an available output current capacity of the DC/DC converter by controlling the input current on the basis of the electric power information fed back from the secondary-side controller. 
     According to another aspect of the present invention, there is provided a power delivery device comprising: a DC/DC converter disposed between an input and an output; a primary-side controller configured to control an input current of the DC/DC converter; an AC coupling capacitor connected to the output; and an insulation circuit connected to the output through the AC coupling capacitor, the insulation circuit configured to feed back the electric power information of the output to the primary-side controller, wherein the primary-side controller varies an output voltage value and an available output current capacity of the DC/DC converter by controlling the input current on the basis of the electric power information fed back from the insulation circuit. 
     According to still another aspect of the present invention, there is provided an AC Adapter comprising the above-mentioned power delivery device. 
     According to still another aspect of the present invention, there is provided an electronic apparatus comprising any one of the above-mentioned power delivery devices. 
     According to still another aspect of the present invention, there is provided a power delivery system comprising any one of the above-mentioned power delivery devices. 
     Advantageous Effects of Invention 
     According to the present invention, there can be provided the PD device, the AC adapter, the electronic apparatus, and the PD system each which can control the variable function of the output voltage value and the available output current capacity (MAX value). 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic circuit block configuration diagram showing a first Power Delivery (PD) device according to basic technology. 
         FIG. 2  is a schematic circuit block configuration diagram showing a second PD device according to basic technology. 
         FIG. 3A  is a schematic diagram showing a relationship of an output voltage and an output current obtained using the second PD device according to the basic technology, which is an example of a rectangular shape showing a Constant Voltage Constant Current (CVCC). 
         FIG. 3B  is a schematic diagram showing the relationship of the output voltage and the output current obtained using the second PD device according to the basic technology, which is an example of a fold-back shape of an inverted trapezium. 
         FIG. 3C  is a schematic diagram showing the relationship of the output voltage and the output current obtained using the second PD device according to the basic technology, which is an example of a fold-back shape of an inverted triangle. 
         FIG. 3D  is a schematic diagram showing the relationship of the output voltage and the output current obtained using the second PD device according to the basic technology, which is an example of a trapezoidal shape. 
         FIG. 3E  is a schematic diagram showing the relationship of the output voltage and the output current obtained using the second PD device according to the basic technology, which is an example of a pentagon shape. 
         FIG. 4  is a schematic circuit block configuration diagram showing a third PD device according to the basic technology. 
         FIG. 5  is a schematic circuit block configuration diagram showing a fourth PD device according to the basic technology. 
         FIG. 6  is a schematic circuit block configuration diagram showing a PD device according to a first embodiment. 
         FIG. 7  is a schematic circuit block configuration diagram showing a PD device according to a second embodiment. 
         FIG. 8  is a schematic circuit block configuration diagram showing a PD device according to a third embodiment. 
         FIG. 9  is a schematic circuit block configuration diagram showing a PD device according to a fourth embodiment. 
         FIG. 10  is a schematic circuit block configuration diagram showing a PD device according to a fifth embodiment. 
         FIG. 11  shows a structural example of an insulating bidirectional circuit in the PD device according to the fifth embodiment. 
         FIG. 12  is a schematic circuit block configuration diagram showing a PD device according to a sixth embodiment. 
         FIG. 13A  shows an example of wire connection in which a plug connectable to a power socket is connected to an AC adapter using a cable, and shows in particular an example in which a PD device in the AC adapter is connected to an external USB PD device using the cable. 
         FIG. 13B  shows the example of wire connection in which the plug connectable to the power socket is connected to the AC adapter using the cable, and shows in particular an example in which a USB PD device is included in the AC adapter. 
         FIG. 13 c    shows the example of wire connection in which the plug connectable to the power socket is connected to the AC adapter using the cable, and shows in particular an example in which the USB PD device included in the AC adapter is connected to the external USB PD device using a USB PD cable. 
         FIG. 14A  shows an example of wire connection in which the plug connectable to the power socket is connected to the AC adapter using a USB PD cable, and shows in particular an example in which the PD device in the AC adapter is connected to the external USB PD device using the cable. 
         FIG. 14B  shows an example of wire connection in which the plug connectable to the power socket is connected to the AC adapter using the USB PD cable, and shows in particular an example in which a USB PD device is included in the AC adapter. 
         FIG. 14 c    shows the example of wire connection in which the plug connectable to the power socket is connected to the AC adapter using the USB PD cable, and shows in particular an example in which the USB PD device included in the AC adapter is connected to the external USB PD device using a USB PD device cable. 
         FIG. 15A  shows an example of wire connection in which the plug connectable to the power socket is included in the AC adapter, and is connected the AC adapter using the connecting means other than the cable, and shows in particular an example in which the PD device in the AC adapter is connected to the external USB PD device using the cable. 
         FIG. 15B  shows the example of wire connection in which the plug connectable to the power socket is included in the AC adapter, and is connected the AC adapter using the connecting means other than the cable, and shows in particular an example in which the USB PD device is included in the AC adapter. 
         FIG. 15C  shows the example of wire connection in which the plug connectable to the power socket is included in the AC adapter, and is connected the AC adapter using the connecting means other than the cable, and shows in particular an example in which the USB PD device included in the AC adapter is connected to the external USB PD device using the USB PD device cable. 
         FIG. 16A  shows an example of wire connection in which the plug connectable to the power socket is included in the AC adapter, and is connected the AC adapter using a connecting means other than the cable, having a plurality of USB ports, and shows in particular an example in which a plurality of the PD devices in the AC adapter is connected to a plurality of the external USB PD devices using the cable. 
         FIG. 16B  shows the example of wire connection in which the plug connectable to the power socket is included in the AC adapter, and is connected the AC adapter using the connecting means other than the cable, having the plurality of the USB ports, and shows in particular an example in which the plurality of the USB PD devices is included in the AC adapter. 
         FIG. 16C  shows the example of wire connection in which the plug connectable to the power socket is included in the AC adapter, and is connected the AC adapter using a connecting means other than the cable, having a plurality of USE ports, and shows in particular an example in which the plurality of the USB PD devices included in the AC adapter is connected to a plurality of the external USB PD devices using a plurality of the USB PD cables. 
         FIG. 17A  shows an example of wire connection in which the electronic apparatus is connected to the plug connectable to the power socket using the cable, and shows in particular an example in which a plurality of internal circuits which include the USB PD device therein are included in an electronic apparatus, having a plurality of signals using the USB PD device. 
         FIG. 17B  shows the example of wire connection in which the electronic apparatus is connected to the plug connectable to the power socket using the cable, and shows in particular an example in which the plug connectable to the power socket is included in the electronic apparatus, the plurality of the internal circuits which include the USB PD device therein are included in the electronic apparatus, having the plurality of the signals using the USB PD device. 
         FIG. 18A  shows the example in which the plug connectable to the power socket is included in the electronic apparatus, the plurality of the internal circuits which include the USB PD device therein are included in the electronic apparatus, having the plurality of the signals using the USB PD device, and shows in particular an example in which a USB PD device connected to the outside is included in one internal circuit. 
         FIG. 18B  shows the example in which the plug connectable to the power socket is included in the electronic apparatus, the plurality of the internal circuits which include the USB PD device therein are included in the electronic apparatus, having the plurality of the signals using the USB PD device, and shows in particular an example in which a plurality of the USB PD devices connected to the outside is included in one internal circuit. 
         FIG. 19A  is an explanatory diagram of a protection function of the USB PD device according to the first to sixth embodiments in the case where a smart phone is used as a connecting target. 
         FIG. 19B  is an explanatory diagram of a protection function of the USB PD device according to the first to sixth embodiments in the case where a laptop Personal Computer (PC) is used as a connecting target. 
         FIG. 20  shows a schematic bird&#39;s-eye view structure example of a plug applicable to the USB PD device according to the first to sixth embodiments. 
         FIG. 21  shows a schematic bird&#39;s-eye view structure example of alternative plug applicable to the USB PD device according to the first to sixth embodiments. 
         FIG. 22  shows a schematic bird&#39;s-eye view structure example of still alternative plug applicable to the USB PD device according to the first to sixth embodiments. 
         FIG. 23  shows a schematic bird&#39;s-eye view structure example of yet alternative plug applicable to the USB PD device according to the first to sixth embodiments. 
         FIG. 24A  is a schematic block configuration diagram illustrating a USB data communication and power delivery between a battery charger system and a laptop PC, in a Power Delivery (PD) system to which the PD devices according to the first to sixth embodiments can be applied. 
         FIG. 24B  is a schematic block configuration diagram illustrating the USB data communication and the power delivery between a smart phone and the laptop PC, in the PD system to which the PD devices according to the first to sixth embodiments can be applied. 
         FIG. 25A  is a schematic block configuration diagram illustrating the USB data communication and the power delivery between two PCs, in the PD system to which the PD devices according to the first to sixth embodiments can be applied. 
         FIG. 25B  is schematic diagram of a waveform in which one-directional AC information AC 1  is superposed on DC power in the PD system to which the PD devices according to the first to sixth embodiments can be applied. 
         FIG. 25C  is schematic diagram of a waveform in which reverse directional AC information AC 2  is superposed on DC power in the PD system to which the PD devices according to the first to sixth embodiments can be applied. 
         FIG. 26A  is a schematic block configuration diagram illustrating the USB data communication and the power delivery between two units, in the PD system to which the PD devices according to the first to sixth embodiments can be applied. 
         FIG. 26B  is schematic diagram of a waveform in which bidirectional control signal is superposed on DC power in the PD system to which the PD devices according to the first to sixth embodiments can be applied. 
         FIG. 27  is a schematic block configuration diagram of the PD system to which the PD devices according to the first to sixth embodiments can be applied composed of an AC adapter and a smart phone each which include the USB PD device therein. 
         FIG. 28  is a schematic block configuration diagram of the PD system to which the PD devices according to the first to sixth embodiments can be applied composed of two units each which include the USB PD device therein. 
         FIG. 29A  is a schematic block configuration diagram of the PD system to which the PD devices according to the first to sixth embodiments can be applied composed of alternative two units. 
         FIG. 29B  is a schematic diagram illustrating a transmission direction of USB data and electric power transmitted through the USB PD cable, in the PD system to which the PD devices according to the first to sixth embodiments. 
         FIG. 30  is a first schematic block configuration diagram of the PD system to which the PD devices according to the first to sixth embodiments. 
         FIG. 31  is a second schematic block configuration diagram of the PD system to which the PD devices according to the first to sixth embodiments. 
         FIG. 32  is a third schematic block configuration diagram of the PD system to which the PD devices according to the first to sixth embodiments. 
         FIG. 33  is a forth schematic block configuration diagram of the PD system to which the PD devices according to the first to sixth embodiments. 
         FIG. 34  shows a usage example of a USB PD-IC applicable to the PD devices according to the first to sixth embodiments. 
         FIG. 35  shows a usage example of the USB PD-IC applicable to the PD devices according to the first to sixth embodiments. 
         FIG. 36  shows a usage example of the USB PD-IC applicable to the PD devices according to the first to sixth embodiments. 
         FIG. 37  shows a usage example of the USB PD-IC applicable to the PD devices according to the first to sixth embodiments. 
         FIG. 38  shows a usage example of the USB PD-IC applicable to the PD devices according to the first to sixth embodiments. 
         FIG. 39A  is a schematic circuit block configuration diagram showing a PD device according to a seventh embodiment. 
         FIG. 39B  shows a structural example of an insulating bidirectional circuit applicable to the PD device according to the seventh embodiment. 
         FIG. 40  is a schematic circuit block configuration diagram showing a PD device according to an eighth embodiment. 
         FIG. 41  is a schematic circuit block configuration diagram showing a PD device according to a ninth embodiment. 
         FIG. 42  is a schematic circuit block configuration diagram showing a PD device according to a tenth embodiment. 
         FIG. 43  is a schematic circuit block configuration diagram showing a PD device according to an eleventh embodiment. 
         FIG. 44  is a schematic circuit block configuration diagram showing a PD device according to a twelfth embodiment 
         FIG. 45  is a schematic circuit block configuration diagram showing a PD device according to a thirteenth embodiment. 
         FIG. 46  is a schematic circuit block configuration diagram showing a PD device according to a fourteenth embodiment. 
         FIG. 47  is a schematic circuit block configuration diagram illustrating an aspect for achieving DC feedback and AC signal common in the fourteenth embodiment. 
         FIG. 48A  is a schematic circuit block configuration diagram of an insulating bidirectional circuit applicable to the PD device according to the fourteenth embodiment. 
         FIG. 48B  is a schematic circuit block configuration diagram of an alternative insulating bidirectional circuit applicable to the PD device according to the fourteenth embodiment. 
         FIG. 48C  is a schematic circuit block configuration diagram of still alternative insulating bidirectional circuit applicable to the PD device according to the fourteenth embodiment. 
         FIG. 49  is a schematic circuit block configuration diagram showing a PD device according to a fifteenth embodiment. 
         FIG. 50  is a schematic circuit block configuration diagram showing a PD device according to a sixteenth embodiment. 
         FIG. 51  is a schematic circuit block configuration diagram showing a PD device according to a seventeenth embodiment. 
         FIG. 52  is a schematic circuit block configuration diagram showing a PD device according to an eighteenth embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     There will be described embodiments of the present invention, with reference to the drawings. In the following drawings, same blocks or elements are designated by same reference characters to eliminate redundancy and for simplicity. However, it should be known about that the drawings are schematic and are differ from an actual thing. Of course, the part from which the relation and ratio of a mutual size differ also in mutually drawings is included. 
     The embodiments to be described hereinafter exemplify the apparatus and method for a technical concept or spirit of the present invention; and do not specify dispositions, etc. of each component part as examples mentioned below. The embodiments of the present invention may be changed without departing from the spirit or scope of claims. 
     [Basic Technology] 
     As shown in  FIG. 1 , a first PD device  4  according to a basic technology includes: a DC/DC converter  13  disposed between an input and an output, and composed of a transformer  15 , a diode D 1 , a capacitor. C 1 , and a MOS transistor Q 1  connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential, and a resistor RS; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a power source supply circuit  10  connected between the input and the primary-side controller  30 , and configured to supply a power source to the primary-side controller  30 ; an error amplifier  21  for error compensation connected to the output; and an insulation circuit  20  connected to the error amplifier  21  and configured to feed back output information to the primary-side controller  30 . 
     In the first PD device  4  according to the basic technology, the voltage is fed back from the output. More specifically, the electric power information is fed back from the output (secondary) side to the input (primary) side, and ON/OFF of MOS transistor Q 1  is controlled by the primary-side controller  30 , thereby stabilizing the output voltage. The amount of current conducted to the primary-side inductance L 1  in the transformer  15  is detected by the current sensing resistor RS, and the amount of current of the primary-side overcurrent is controlled in the primary-side controller  30 . 
     As shown in  FIG. 2 , a second PD device  4  according to the basic technology includes: a current sensing resistor RL connected to in series between a secondary-side inductance L 2  of the transformer  15  and the ground potential, and a power amplifier  19  connected to the both terminals of the resistor RL. The power amplifier  19  transmits AC current information detected in the resistor RL to the error amplifier  21 . Other configurations are the same as those of the first PD device  4  shown in  FIG. 1 . 
     According to the second PD device  4  according to the basic technology, the current sensing circuit (RL) is disposed with respect to the secondary-side inductance L 2  in the transformer  15 , and the amount of current in the secondary side is detected and fed back to the primary-side controller  30  through the error amplifier  21  and the insulation circuit  20 . Also the a second PD device  4  according to the basic technology, the electric power information is fed back from the output (secondary) side to the input (primary) side, and ON/OFF of MOS transistor Q 1  is controlled by the primary-side controller  30 , thereby stabilizing the output voltage. 
     The second PD device  4  according to the basic technology can control the amount of current in the secondary side. Accordingly, the various relationships between the output voltage V o  and the output currents I o  can be selected in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the second PD device  4  according to the basic technology, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , a fold-back shape of inverted trapezium as shown in  FIG. 3B , a fold-back shape of inverted triangle as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . For example, the rectangular shape shown in  FIG. 3A  is an example of Constant Voltage Constant Current (CVCC). 
     As shown in  FIG. 4 , a third PD device  4  according to the basic technology includes: a current sensing resistor RL connected in series between the diode D 1  which composes the DC/DC converter  13 , and the output, and a power amplifier  19  connected to the both terminals of the resistor RL. The power amplifier  19  can transmit DC current information to the error amplifier  21 . Other configurations are the same as those of the first PD device  4  shown in  FIG. 1 . 
     The third PD device  4  according to the basic technology can also control the amount of current in the secondary side. Accordingly, As shown in  FIGS. 3A, 3B, 3C, 3D and 3E , the various relationships between the output voltage V o  and the output currents I o  can be selected in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As shown in  FIG. 5 , a fourth PD device  4  according to the basic technology includes: an auxiliary inductance L 11  composed of primary-side auxiliary winding in the transformer  15 , and resistors Rf 1 , Rf 2  for feedback connected in parallel to the auxiliary inductance L 11 . A detected voltage detected in the resistors Rf 1 , Rf 2  for feedback is fed back to the primary-side controller  30  through the error amplifier  21  disposed in the primary side. Other configurations are the same as those of the first PD device  4  shown in  FIG. 1 . 
     According to the second PD device  4  according to the basic technology, the amount of power is recognized in the primary side by the auxiliary inductance L 11  connected to the primary-side inductance L 1  in the transformer  15  and the resistors Rf 1 , Rf 2  for feedback, and then is fed back to the primary-side controller  30 , and ON/OFF of the MOS transistor Q 1  is controlled by the primary-side controller  30 , thereby stabilizing the output voltage. 
     The second PD device  4  according to the basic technology is applicable to mobile phones, tablet PCs, etc. which can operate, for example, at approximately 10 W. 
     First Embodiment 
     As shown in  FIG. 6 , a PD device  4 A according to a first embodiment includes: a DC/DC converter  13  disposed between an input and an output, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a power source supply circuit  10  connected between the input and the primary-side controller  30 , and configured to supply a power source to the primary-side controller  30 ; a secondary-side controller (PD CHIP)  16  which is connected to the output through the capacitor C 2 , and can control an output voltage V o  and an output current I o ; an error amplifier  18  connected to the output of DC/DC converter  13  and the secondary-side controller  16 , and used for error compensation; and an insulation circuit  20  connected to the error amplifier  18  and configured to feed back output information to the primary-side controller  30 . 
     An inductance L 3  is a separating inductance. More specifically, a filter circuit composed of the inductance L 3  and a capacitor CF separates a control signal from the DC/DC converter so that the control signal from the output is not input into the DC/DC converter. 
     A capacitor, a photo coupler, a transformer, etc. is applicable to the insulation circuit  20 . As usage, a bidirectional transformer having an insulated driver, a bilateral device, etc. may also be applied thereto. 
     In the PD device  4 A according to the first embodiment, the voltage is fed back from the output. Moreover, the PD device  4 A according to the first embodiment has an output voltage variable function. 
     In the PD device  4 A according to the first embodiment, an AC signal is superposed on and input into the output terminal from the outside. 
     In the PD device  4 A according to the first embodiment, the control signal is input into the secondary-side controller  16  through the capacitor C 2  from the output, and the electric power information in the output side is fed back to the primary-side controller  30  through the error amplifier  18  and the insulation circuit  20 . The primary-side controller  30  controls ON/OFF of the MOS transistor Q 1 , thereby stabilizing the output voltage. 
     Moreover, in the PD device  4 A according to the first embodiment, the amount of current conducted to the primary-side inductance L 1  is detected by the current sensing resistor RS, and the amount of current, e.g. a primary-side overcurrent, is controlled in the primary-side controller  30 . 
     As a consequence, the PD device  4 A according to the first embodiment has a variable function of an output voltage value and available output current capacity (MAX value). 
     In the PD device  4 A according to the first embodiment, control information is transmitted to the primary-side controller  30  through the insulation circuit  20  from the secondary-side controller  16 , and thereby the output voltage and the available output current capacity (MAX value) can be varied. 
     A voltage-current control circuit for controlling the output voltage V o  and the output current I o  is included in the secondary-side controller (PD CHIP)  16 . 
     In the PD device  4 A according to the first embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the first embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the first embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13  achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . 
     In the PD device  4 A according to the first embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the first embodiment can be called a USB Power Delivery (USB PD) device. 
     Second Embodiment 
     As shown in  FIG. 7 , a PD device  4 A according to a second embodiment includes: a DC/DC converter  13  disposed between an input and an output, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a power source supply circuit  10  configured to supply a power source to the primary-side controller  30 ; an error amplifier  18  connected to the output of the DC/DC converter  13 , and also connected to the output through the capacitor C 2 ; and an insulation circuit  20  connected to the error amplifier  18  and configured to feed back output information to the primary-side controller  30 . Other configurations are the same as those of the first embodiment. 
     In the PD device  4 A according to the second embodiment, the AC signal is superposed on and input into the output terminal from the outside. 
     In the PD device  4 A according to the second embodiment, there is no secondary-side controller  16  as provided in the first embodiment. 
     In the PD device  4 A according to the second embodiment, the control signal is input directly into the error amplifier  18  and the insulation circuit  20  through the capacitor C 2  from the output, and the electric power information in the output side is fed back, to the primary-side controller  30  through the error amplifier  18  and the insulation circuit  20 . The primary-side controller  30  controls ON/OFF of the MOS transistor Q 1 , thereby stabilizing the output voltage. 
     In the PD device  4 A according to the second embodiment, the amount of current conducted to the primary-side inductance L 1  is detected by the current sensing resistor RS, and the amount of current, e.g. a primary-side overcurrent, is controlled in the primary-side controller  30 . 
     As a consequence, the PD device  4 A according to the second embodiment has a variable function of an output voltage value and available output current capacity (MAX value). 
     In the PD device  4 A according to the second embodiment, the control information is transmitted to the primary-side controller  30  through the insulation circuit  20  and the capacitor C 2  from the outside, and thereby the output voltage and the available output current capacity (MAX value) can be varied. 
     According to the second embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control to the primary-side controller  30  through the capacitor C 2  and the insulation circuit  20  from the outside. Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the second embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the second embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13  achieved by the feedback control to the primary-side controller  30  through the capacitor C 2  and the insulation circuit  20  from the outside. 
     The PD device  4 A according to the second embodiment can be called merely a power delivery (PD) device since the secondary-side controller (PD CHIP)  16  can be omitted. 
     Third Embodiment 
     As shown in  FIG. 8 , a PD device  4 A according to a third embodiment includes an AC/DC converter connected to the AC input and composed of a fuse  11 , a choke coil  12 , a diode rectification bridge  14 , capacitors C 5 , C 6 , C 3 , etc., instead of the power source supply circuit  10  as in the first embodiment. 
     Moreover, an auxiliary inductance L 4  composed of the primary-side auxiliary winding in the transformer  15 , and a diode D 2  and a capacitor C 4  connected in parallel to the auxiliary inductance L 4  are provided therein, and the DC voltage VCC is supplied from the capacitor C 4  to the primary-side controller  30 . 
     Furthermore, as shown in  FIG. 8 , the PD device  4 A according to the third embodiment includes: a DC/DC converter  13  disposed between an output of AC/DC converter and an output, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a secondary-side controller (PD CHIP)  16  which is connected to the output through the capacitor C 2 , and can control an output voltage V o  and an output current I o ; an error amplifier  18  connected to the output of DC/DC converter  13  and the secondary-side controller  16 , and used for error compensation; and an insulation circuit  20  connected to the error amplifier  18  and configured to feed back output information to the primary-side controller  30 . Other configurations are the same as those of the first embodiment. 
     In the PD device  4 A according to the third embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the third embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the third embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13  achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . 
     In the PD device  4 A according to the third embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the third embodiment can be called a USB Power Delivery (USB PD) device having the AC/DC converter function (AC/DC+USB PD). 
     Fourth Embodiment 
     As shown in  FIG. 9 , a PD device  4 A according to a fourth embodiment includes an AC/DC converter connected to an AC input and composed of a fuse  11 , a choke coil  12 , a diode rectification bridge  14 , capacitors C 5 , C 6 , C 3 , etc., instead of the power source supply circuit  10  as in the first embodiment, in the same manner as the third embodiment. 
     As shown in  FIG. 9 , the PD device  4 A according to the fourth embodiment includes an independent DC/DC converter  24  which is connected to the output of the step-down (buck) type DC/DC converter  13  and which includes the secondary-side controller (PD CHIP)  16  therein. 
     The synchronous rectification type DC/DC converter  24  is composed of the MOS transistor Q 2 , the inductance L 7 , and the secondary-side controller (PD CHIP)  16 . The secondary-side controller (PD CHIP)  16  is connected to the gate of the MOS transistor Q 2 , and the secondary-side controller (PD CHIP)  16  controls ON/OFF of the MOS transistor Q 2 . The inductance L 7  is an inductance used for the DC/DC converter  24 . 
     An inductance L 8  is a PD separating inductance. More specifically, a filter circuit composed of the inductance L 8  and a capacitor C 5  separates a control signal from the DC/DC converter so that the control signal from the output side is not input into the DC/DC converter. 
     Furthermore, as shown in  FIG. 9 , the PD device  4 A according to the fourth embodiment includes: ADC/DC converter  13  disposed between the output of the AC/DC converter and the output of the DC/DC converter, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a secondary-side controller (PD CHIP)  16  which is connected to the output through the capacitor C 2 , and can control an output voltage V o  and an output current I o ; an error amplifier  44  connected to the output of the DC/DC converter  13 ; and an insulation circuit  20  connected to the error amplifier  44  and configured to feed back output information to the primary-side controller  30 . Furthermore, the secondary-side controller (PD CHIP)  16  may be connected to the error amplifier  44  in the same manner as the third embodiment. Other configurations are the same as those of the third embodiment. 
     In the PD device  4 A according to the fourth embodiment, the voltage is fed back from the output of the DC/DC converter  13 . More specifically, the electric power information is fed back from the output of the DC/DC converter  13  (secondary) side to the input (primary) side, and ON/OFF of MOS transistor Q 1  is controlled by the primary-side controller  30 , thereby stabilizing the output voltage. The amount of current conducted to the primary-side inductance L 1  in the transformer  15  is detected by the current sensing resistor RS, and the amount of current of the primary-side overcurrent is controlled in the primary-side controller  30 . 
     Moreover, in the PD device  4 A according to the fourth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the synchronous rectification type DC/DC converter  24  is achieved by the secondary-side controller (PD CHIP)  16  included in the synchronous rectification type DC/DC converter  24 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the fourth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the fourth embodiment, the output voltage of diode rectification and step-down (buck) type DC/DC converter  13  is stabilized by the feedback control from the output of step-down (buck) type DC/DC converter to the primary-side controller  30 , and the variable function of the output voltage value and the available output current capacity (MAX value) of the synchronous rectification type DC/DC converter  24  connected to the DC/DC converter  13  is achieved by the secondary-side controller (PD CHIP)  16  included in the synchronous rectification type DC/DC converter  24 . 
     As a consequence, according to the fourth embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13 . 
     In the PD device  4 A according to the fourth embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the fourth embodiment can be called a USB Power Delivery (USB PD) device having the AC/DC converter function (AC/DC+USB PD). 
     Fifth Embodiment 
     As shown in  FIG. 10 , a PD device  4 A according to a firth embodiment includes: a DC/DC converter  13  disposed between an input and an output, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a power source supply circuit  10  connected between the input and the primary-side controller  30 , and configured to supply a power source to the primary-side controller  30 ; an insulating bidirectional circuit  28  connected to the output of the DC/DC converter  13 , and also connected to the output terminal through the capacitor C 2 ; and a DC/AC component separating circuit  26  which is connected to the insulating bidirectional circuit  28  and which feeds back the electric power information in the output side to the primary-side controller  30 . 
     The DC/AC component separating circuit  26  includes a Low Pass Filter (LPF)  29  and a DC component eliminating circuit  27 , in the PD device  4 A according to the firth embodiment. 
     The DC information of the output of DC/DC converter is input into the DC component eliminating circuit  27  and the LPF  29  in the DC/AC component separating circuit  26  through the insulating bidirectional circuit  28 . The input AC information of the output terminal is also input into the DC component eliminating circuit  27  and the LPF  29  in the DC/AC component separating circuit  26  through the capacitor C 2  and the insulating bidirectional circuit  28  from the output terminal. 
     The DC output of LPF  29  is fed back directly to the primary-side controller  30  as DC information (FBD). The DC information (DC component) of the output of DC/DC converter is removed in the DC component eliminating circuit  27 , and only the input AC information is fed back to the primary-side controller  30  (FBA 1 ). The input control signal from the outside of the output terminal is AC-superposed on the input AC information. 
     Furthermore, the output AC information (FBA 2 ) is fed back from the primary-side controller  30  to the output terminal through the insulating bidirectional circuit  28  and the capacitor C 2 . In the present embodiment, the output control signal is superposed on the output AC information (FBA 2 ) fed back to the output terminal from the primary-side controller  30 . 
     The PD device  4 A according to the firth embodiment includes a circuit configured to restore the input control signal included in the input AC information; and a circuit configured to superpose the output control signal on the output AC information from the primary-side controller  30 , in the primary-side controller  30 . 
     In the PD device  4 A according to the firth embodiment, the input control signal superposed on the input AC information is input into the output terminal from the outside. More specifically, the input control signal is input into the insulating bidirectional circuit  28  through the capacitor C 2  from the output, the electric power information is fed back to the primary-side controller  30  through the DC/AC component separating circuit  26  from the insulating bidirectional circuit  28 , and ON/OFF of the MOS transistor Q 1  is controlled by the primary-side controller  30 , thereby stabilizing the output voltage. Moreover, the amount of current conducted to the primary-side inductance L 1  is detected by the current sensing resistor RS, and the amount of current of the primary-side overcurrent is controlled in the primary-side controller  30 . 
     The insulating bidirectional circuit  28  can bidirectionally transmit the input/output AC information with the DC information. 
     A bidirectional transformer having an insulated driver, a bidirectional device, etc. are applicable to the insulating bidirectional circuit  28 . Moreover, the insulating bidirectional circuit  28  may be composed by combining a plurality of unidirectional circuits and unidirectional elements. 
     For example, the insulating bidirectional circuit  28  may include a plurality of insulating unidirectional circuits  31 ,  32  as shown in  FIG. 11 . In the present embodiment, the insulating unidirectional circuit  31  can transmit the DC information and the input AC information from the secondary side to the primary side, and the insulating unidirectional circuit  32  can transmit the output AC information from the primary side to the secondary side. The plurality of the insulating unidirectional circuits  31 ,  32  are combined, thereby composing the insulating bidirectional circuit  28  as a consequence. 
     In the PD device  4 A according to the fifth embodiment, the control information is transmitted to the primary-side controller  30  through the DC/AC component separating circuit  26  from the insulating bidirectional circuit  28 , and thereby the output voltage and the available output current capacity (MAX value) can be varied. 
     In the PD device  4 A according to the fifth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control from the insulating bidirectional circuit  28  to the primary-side controller  30 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the fifth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the fifth embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13  achieved by the feedback control to the primary-side controller  30  through the capacitor C 2  and the insulation circuit  20  from the insulating bidirectional circuit  28 . 
     The PD device  4 A according to the fifth embodiment can be called merely a Power Delivery (PD) device since the secondary-side controller (PD CHIP)  16  can be omitted. 
     Sixth Embodiment 
     As shown in  FIG. 12 , a PD device  4 A according to a sixth embodiment includes: a synchronous rectification type DC/DC converter  13  disposed between an input and an output, and composed of a transformer  15 , a MOS transistor Q 3 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a power source supply circuit  10  connected between the input and the primary-side controller  30 , and configured to supply a power source to the primary-side controller  30 ; a secondary-side controller (PD CHIP)  16  which is connected to the output through the capacitor C 2 , and can control an output voltage V o  and an output current I o ; and an insulation circuit  20  connected to the secondary-side controller (PD CHIP)  16 , and configured to feed back the output information to the primary-side controller  30 . As shown in  FIG. 6 , an error amplifier  18  for error compensation may be disposed between the secondary-side controller (PD CHIP)  16  and the insulation circuit  20 . 
     In the PD device  4 A according to the sixth embodiment, since, the synchronous rectification method is adopted for the DC/DC converter, instead of the diode rectification system, and thereby DC/DC power conversion efficiency can be increased, compared with the first to fifth embodiments adapting the diode rectification system. Other configurations are the same as those of the first embodiment. 
     A voltage-current control circuit for controlling the output voltage V o  and the output current I o  is included in the secondary-side controller (PD CHIP)  16 . 
     In the PD device  4 A according to the sixth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the synchronous rectification type DC/DC converter  13  is achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the sixth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the sixth embodiment, There can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the synchronous rectification type DC/DC converter  13  achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . 
     In the PD device  4 A according to the sixth embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the sixth embodiment can be called a USE Power Delivery (USB PD) device. 
     (AC Adapter) 
     The PD device  4 A according to the first to sixth embodiments can be included in an AC adapter  3 , as shown in  FIGS. 13A, 13B and 13C  and  FIGS. 14A, 14B, and 14C . Moreover, the AC adapter  3  can be connected to the USB PD device  5  disposed in the outside according to the first to sixth embodiments with a cable or a USB PD cable  6 . 
     The AC adapter  3  including the PD device  4 A according to the first to sixth embodiments can be connected to both of a plug  2  connectable to a power socket  1  and the USB PD device  5  disposed in the outside, using the cable, as shown in  FIG. 13A . 
     Moreover, the AC adapter  3  including the USB PD device  4 A according to the first to sixth embodiments can be connected to the plug  2  connectable to the power socket  1  using the cable, as shown in  FIG. 13B . 
     Moreover, the AC adapter  3  including the PD device  4 A according to the first to sixth embodiments can be connected to both of a plug  2  connectable to the power socket  1  and the USB PD device  5  disposed in the outside, using the USB PD cable  6 , as shown in  FIG. 13C . 
     Moreover, as shown in  FIG. 14A , the AC adapter  3  including the PD device  4 A according to the first to sixth embodiments can be connected to the plug  2  connectable to the power socket  1  using the USB PD cable  6 ; and can be connected to the USB PD device  5  disposed on the outside using the cable. 
     Moreover, the AC adapter  3  including the PD device  4 A according to the first to sixth embodiments can be connected to the plug  2  connectable to the power socket  1  using the USB PD cable  6 , as shown in  FIG. 14B . 
     Moreover, as shown in  FIG. 14C , the AC adapter  3  including the USB PD device  4 A according to the first to sixth embodiments can be connected to the plug  2  connectable to the power socket  1  using the USB PD cable  6 ; and can be connected to the USB PD device  5  disposed on the outside using the USB PD cable. 
     Moreover, the plug  2  connectable to the power socket  1  may be included in the AC adapter  3  including the PD device  4 A according to the first to sixth embodiments, as shown in  FIGS. 15A, 15B and 15C . 
     The AC adapter  3  including the PD device  4 A according to the first to sixth embodiments and the plug  2  connectable to the power socket  1  can be connected to the USB PD device  5  disposed on the outside using the cable, as shown in  FIG. 15A . 
     Moreover, the AC adapter  3  including the USB PD device  4 A according to the first to sixth embodiments and the plug  2  connectable to the power socket  1  is illustrated as shown in  FIG. 15B . 
     Moreover, as shown in  FIG. 15C , the AC adapter  3  including the USB PD device  4 A according to the first to sixth embodiments and the plug  2  connectable to the power socket  1  can be connected to the USB PD device  5  disposed on the outside using the USB PD cable  6 . 
     A plurality of the PD devices  4 A according to the first to sixth embodiments can be included in the AC adapter  3 , as shown in  FIGS. 16A, 16B and 16C . Moreover, the PD devices  4 A can be connected to the USB PD devices  51 ,  52  disposed in the outside according to the first to sixth embodiments with the cable or the USB PD cable  6 . 
     As shown in  FIG. 16A , the AC adapter  3  including the USB PD devices  41 ,  42  according to the first to sixth embodiments and the plug  2  connectable to the power socket  1  can be connected to the USB PD devices  51 ,  52  disposed on the outside using the cable. 
     Moreover, the AC adapter  3  including the USB PD devices  41 A,  42 A according to the first to sixth embodiments and the plug  2  connectable to the power socket  1  is illustrated as shown in  FIG. 16B . 
     Moreover, as shown in  FIG. 16C , the AC adapter  3  including the USB PD devices  41 A,  42 A according to the first to sixth embodiments and the plug  2  connectable to the power socket  1  can be connected to the USB PD devices  51 ,  52  disposed on the outside using the USB PD cables  61 ,  62 . 
     (Electronic Device) 
     The PD devices  41 A,  42 A according to the first to sixth embodiments can be included in an electronic apparatus  7 , as shown in  FIGS. 17A, 17B, 18A and 18B . Various devices, e.g. smart phones, laptop PCs, tablet PCs, monitors or TVs, external hard disk drives, set top boxes, cleaners, refrigerators, washing machines, telephone sets, facsimile machines, printers, laser displays, are applicable to the electronic apparatus, for example. 
     The electronic apparatus  7  including the PD devices  41 A,  42 A according to the first to sixth embodiments is connected to the plug  2  connectable to the power socket  1  using the cable, as shown in  FIG. 17A . 
     Moreover, the electronic apparatus  7  may include the plug  2  connectable to the power socket  1  in the electronic apparatus  7 , as shown in  FIG. 17B . 
     As shown in  FIGS. 17A and 17B , the electronic apparatus  7  includes a plurality of internal circuits  71 ,  72  respectively including the USB PD devices  41 A,  42 A according to the first to sixth embodiments, and the USB PD devices  41 A,  42 A are connected to each other using the USB PD cable  6 . Since the electronic apparatus  7  includes the plurality of the internal circuits  71 ,  72  including the USB PD devices  41 A,  42 A, there are a plurality of signals used for the USB PD devices  41 A,  42 A in the electronic apparatus  7 . 
     The electronic apparatus  7  including the PD devices  41 A,  42 A according to the first to sixth embodiments may include the USB PD device  41  connectable to other electronic apparatus disposed in the outside of electronic apparatus  7 , in one internal circuit  72 , as shown in  FIG. 18A . 
     As shown in  FIG. 18B , the electronic apparatus  7  including the PD devices  41 A,  42 A according to the first to sixth embodiments may include a plurality of the USB PD devices  43 A,  44 A connectable to other electronic apparatus disposed in the outside of electronic apparatus  7 , in one internal circuit  72 , as shown in  FIG. 18A . 
     (Protection Function) 
     The PD device  4 A according to the first to sixth embodiments may include a primary-side overpower Protecting circuit (OPP 1 )  81  as shown in  FIG. 19A , and a secondary-side overpower Protecting circuit (OPP 2 )  82  connected to the primary-side overpower protecting circuit (OPP 1 )  81 . 
     The primary-side overpower protecting circuit (OPP 1 )  81  is connected to the primary-side controller  30 . Moreover, the primary-side overpower protecting circuit (OPP 1 )  81  may be included in the primary-side controller  30 . 
     The secondary-side overpower protecting circuit (OPP 2 )  82  is connected to the secondary-side controller (PD CHIP)  16 . 
     In  FIG. 19A , although the AC/DC converter, the DC/DC converter  13 , etc. are not illustrated, the configuration of the PD device  4 A according to the first to sixth embodiments as shown in  FIGS. 6-12  can be applied thereto. 
     In accordance with target equipments (sets) connected to the USB connector, the electric power information in the USB connector is transmitted to the secondary-side overpower protecting circuit (OPP 2 )  82  from the secondary-side controller (PD CHIP)  16 , and the secondary-side overpower protecting circuit (OPP 2 )  82  communicates the electric power information in the output terminal to the primary-side overpower protecting circuit (OPP 1 )  81 . 
     Consequently, an overcurrent detecting set value can be changed in accordance with the target equipments (sets) connected to the USB connector, thereby executing the power change of the DC/DC converter  13 . 
     Any of the primary-side overpower protecting circuit (OPP 1 )  81  and the secondary-side overpower protecting circuit (OPP 2 )  82  may determine whether the electric power information in the USB connector exceeds the overcurrent detecting set value. 
     If any one of the primary-side overpower protecting circuit (OPP 1 )  81  and the secondary-side overpower protecting circuit  82  (OPP 2 ) determines that the electric power information in the USB connector exceeds the overcurrent (overpower) detecting set value, the primary-side overpower protecting circuit (OPP 1 )  81  can transmit the overcurrent (overpower) protecting control signal to the primary-side controller  30 , thereby executing the change for controlling the electric power in the DC/DC converter  13 . 
     There are applicable functions, e.g. an OverCurrent Protection (OCP), an OverPower Protection (OPP), OverVoltage Protection (OVP), OverLoad Protection (OLP), and a Thermal Shut Down (TSD), to the PD device  4 A according to the first to sixth embodiments. 
     The PD device  4 A according to the first to sixth embodiments includes a sensor (SENSOR) protection function for executing protection corresponding to the characteristics of a certain sensor element connected to the primary-side controller  30 , for example. 
     When changing the overcurrent (overpower) detecting set value in the PD device  4 A according to the first to sixth embodiments, the electric power information in the USB connector is transmitted to the primary-side overpower protecting circuit (OPP 1 )  81  through the secondary-side controller (PD CHIP)  16  and the secondary-side overpower protecting circuit (OPP 2 )  82 , and the overcurrent detecting set value is changed in accordance with the target equipments (sets) connected to the USB connector, thereby executing the power change of the DC/DC converter  13 , as mentioned above. 
     Moreover, when changing the overcurrent (overpower) detecting set value in the PD device  4 A according to the first to sixth embodiments, the electric power information in the USB connector may be directly transmitted to the primary-side overpower protecting circuit (OPP 1 )  81  from the secondary-side controller (PD CHIP)  16 , and then the set value may be directly changed in the primary-side overpower protecting circuit (OPP 1 )  81 . 
     Moreover, the electric power information may be directly transmitted to the primary-side overpower protecting circuit (OPP 1 )  81  from the PD device disposed in the outside of the PD device  4 A according to the first to sixth embodiments. 
     Thus, according to the PD device  4 A according to the first to sixth embodiments, it is possible to change the power delivery level corresponding to the target equipments (sets) connected to the USB connector, in the primary-side overpower protecting circuit (OPP 1 )  81 . Consequently, a destruction of the target equipments (sets) can be prevented under an abnormal state. 
     When using a smart phone  160  as a connecting target, if the electric power information of 7 W is transmitted to the secondary-side overpower protecting circuit (OPP 2 )  82  from the secondary-side controller (PD CHIP)  16 , for example, with respect to the smart phone  160  (the amount of power 5V·1 A=5 W), the electric power information of 7 W is transmitted to the primary-side overpower protecting circuit (OPP 1 )  81  from the secondary-side overpower protecting circuit (OPP 2 )  82 , and then the overcurrent (overpower) detecting set value is changed (SW) from 7 W up to 10 W in the primary-side overpower protecting circuit (OPP 1 )  81 . Consequently, the electric power up to 10 W can be transmitted, in the DC/DC converter in the PD device  4 A according to the first to sixth embodiments. 
     When using a laptop PC  140  as a connecting target, if the electric power information of 80 W is transmitted to the secondary-side overpower protecting circuit (OPP 2 )  82  from the secondary-side controller (PD CHIP)  16 , for example, with respect to the laptop PC  140  (the amount of power 20V·3 A=60 W), the electric power information of 80 W is transmitted to the primary-side overpower protecting circuit (OPP 1 )  81  from the secondary-side overpower protecting circuit (OPP 2 )  82 , and then the overcurrent (overpower) detecting set value is changed (SW) from 80 W up to 100 W in the primary-side overpower protecting circuit (OPP 1 )  81 . Consequently, the electric power up to 100 W can be transmitted, in the DC/DC converter in the PD device  4 A according to the first to sixth embodiments. 
     (Plug) 
     As shown in  FIG. 20 , a plug  85  applicable to the adapter and the electronic apparatus mounted with the PD device (PD, USB PD) according to the first to sixth embodiments can be connected to the power socket having the AC power source, e.g., 100V-115V, and can also be USB-connected. 
     Moreover, as shown in  FIG. 21 , a plug  86  applicable to the adapter and the electronic apparatus mounted with the PD device (PD, USB PD) according to the first to sixth embodiments can be connected to the power socket having the AC power source, e.g., 230V, and can also be USB-connected. 
     Moreover, as shown in  FIG. 22 , a plug  87  applicable to the adapter and the electronic apparatus mounted with the PD device (PD, USB PD) according to the first to sixth embodiments can be connected to the power socket having the AC power source, e.g., 100V-115V, and a plurality of the USB connections can also be achieved. 
     Moreover, as shown in  FIG. 23 , a plug  88  applicable to the adapter and the electronic apparatus mounted with the PD device (PD, USB PD) according to the first to sixth embodiments can be connected to the power socket having the AC power source, e.g., 100V-115V, and USB PD cable connection can also be achieved. 
     (Power Delivery System) 
     In the power delivery (PD) system capable of applying the PD device according to the first to sixth embodiments, the source of electric power can be switched without changing a direction of the cable. For example, electric charging of a battery in a laptop PC from external devices and power transmission from the battery in the laptop PC to external devices (e.g., display etc.) can be achieved without replacement of the cable. 
     Moreover, a half-duplex data communication with AC superposition can be achieved between two units through the USB PD cable. 
     In the PD system capable of applying the PD device according to the first to sixth embodiments, DC power delivery (DC output V BUS ) and USB data communications (D + , D − , ID, etc.) can be achieved using the USB PD cable  6  between the Battery Charger System (BCS)  46  and the laptop PC  140 , as shown in  FIG. 24A . In the present embodiment, although the PD device according to the first to sixth embodiments is mounted in the BCS  46  and the laptop PC  140 , illustration thereof is omitted. 
     In the PD system capable of applying the PD device according to the first to sixth embodiments, the DC power delivery (DC output V BUS ) and the USB data communications (D + , D − , ID, etc.) can be transmitted also between the smart phone  160  and the laptop PC  140  using the USB PD cable  6 , in the same manner as  FIG. 24A . Furthermore, as shown in  FIG. 24B , a transmitter (T X )  50 T and a receiver (R X )  50 R for USB data communications are mounted in the smart phone  160 , and a transmitter (T X )  52 T and a receiver (R X )  52 R for USB data communications are mounted in the laptop PC  140 . In the present embodiment, although the PD device according to the first to sixth embodiments is mounted in the smart phone  160  and the laptop PC  140 , illustration thereof is omitted. The transmitter (T X )  50 T,  52 T and the receiver (R X )  50 R,  52 R for USB data communications are included in each secondary-side controller (PD CHIP)  16 . 
     In the PD system capable of applying the PD device according to the first to sixth embodiments,  FIG. 25A  shows a schematic block configuration illustrating the USB data communication and the power delivery between two personal computers PCA, PCB, a waveform in which one-directional AC information AC 1  superposed on the DC power is schematically illustrated as shown in  FIG. 25B , and a waveform in which reverse directional AC information AC 2  superposed on the DC power is schematically illustrated as shown in  FIG. 25B . In the present embodiment, between the personal computers PCA, PCB is connected through the USB PD cable  6 . Moreover, the PD device according to the first to sixth embodiments is mounted in each personal computer PCA, PCB. The illustration of the DC/DC converter is omitted, and the secondary-side controllers (PD CHIP)  16 A,  16 B are illustrated in  FIG. 25A . As shown in  FIG. 25A , a battery E and a battery charger IC (CHG)  53  connected to the battery E are mounted in the personal computer PCA, and a Power Management IC (PMIC)  54  is mounted in the personal computer PCA. 
     In the PD system capable of applying the PD device according to the first to sixth embodiments, for example, electric charging of the battery E from the personal computer PCB to the personal computer PCA, and power transmission of the battery E from the personal computer PCA to the personal computer PCB can achieved without replacement of any cable. 
     Moreover, the secondary-side controllers (PD CHIP)  16 A,  16 B are connected to the DC output V BUS  with AC coupling through the capacitor, and the half-duplex data communication with AC superposition is achieved in between the personal computers PCA, PCB. In the present embodiment, the carrier frequency is approximately 23.2 MHz, for example, and the FSK modulation/demodulation frequency is approximately 300 kbps, for example. In the present embodiment, the Bit Error Rate (BER) is approximately 1×10 −6 , and an LSI for built-in self tests (BIST) may be included therein, for example. 
     In the PD system capable of applying the PD device according to the first to sixth embodiments,  FIG. 26A  shows a schematic block configuration illustrating the USB data communication and the power delivery between two units  56 ,  58 , and a waveform in which the control signals SG 12 , SG 21  to be bidirectionally transmitted are superposed on the DC power is schematically illustrated as shown in  FIG. 26B . The two units  56 ,  58  are connected to each other through the USB PD cable  6 . The two units  56 ,  58  may be arbitrary electronic apparatus, and the PD device according to the first to sixth embodiments is mounted therein. The illustration of the DC/DC converter is omitted, and the secondary-side controllers (PD CHIP)  16 A,  16 B are illustrated in  FIG. 26A . 
       FIG. 27  shows a schematic block configuration in which the smart phone  160  is connected to the AC adapter  3  through the USB PD cable  6 , in the PD system capable of applying the PD device according to the first to sixth embodiments. 
     The AC adapter  3  includes an AC/DC converter  60  and a USB PD  4 A. The smart phone  160  includes a USB PD  5 , a secondary-side controller (PD CHIP)  16 , an embedded type controller (EMBC)  64 , a CPU  68 , a PMIC  54 , a battery  66 , and a CHG  62 . 
     In the PD system capable of applying the PD device according to the first to sixth embodiments, for example, electric charging of the battery  66  in the smart phone  160  from the AC adapter  3 , and power transmission of the battery  66  in the smart phone  160  to external devices can be achieved without replacement of the cables. 
       FIG. 28  shows a schematic block configuration in which the unit  56  and the unit  58  are connected to each other through the USB PD cable  6 , in the PD system capable of applying the PD device according to the first to sixth embodiments. 
     The unit  56  includes an AC/DC converter  60 , a USB PD device  4 A, and a secondary-side controller (PD CHIP)  16 A, and the unit  58  includes a USB PD device  5 , a secondary-side controller (PD CHIP)  16 B, and a load  70 . In the present embodiment, the load  70  can be composed of a CPU, a battery BAT, a controller CTR, etc. 
     Furthermore, as shown in  FIG. 28 , a transmitter (T X )  56 T for USB data communications and a receiver (R X )  56 R are mounted in the secondary-side controller (PD CHIP)  16 A, and a transmitter (T X )  56 T for USB data communications and a receiver (R X )  56 R are mounted in the secondary-side controller (PD CHIP)  16 B. 
     In the PD system capable of applying the PD device according to the first to sixth embodiments, power transmission from the unit  56  to the unit  58 , and power transmission to external devices from the unit  58  can be achieved without replacement of the cable, for example. 
     Moreover, the half-duplex data communication with AC superposition is achieved also in between the units  56 ,  58  through the USB PD cable  6 . 
     In the PD system capable of applying the PD device according to the first to sixth embodiments,  FIG. 29A  shows a schematic block configuration composed of two units  56 ,  58  different from the configuration shown in  FIG. 28 , and  FIG. 29B  shows a schematic diagram illustrating a transmission direction of the USB data and electric power transmitted through the USB PD cable  6 . 
     The unit  56  includes a battery E, a CPU  68 A and a secondary-side controller (PD CHIP)  16 A, and the unit  58  includes a secondary-side controller (PD CHIP)  16 B and a load CL. 
     In the PD system capable of applying the PD device according to the first to sixth embodiments, power transmission from the unit  58  to the unit  56 , and power transmission to the unit  58  from the battery E can be achieved without replacement of the cable, for example. 
     Moreover, the half-duplex data communication with AC superposition is achieved also in between the units  56 ,  58  through the USB PD cable  6 . 
     (Power Delivery System) 
     As shown in  FIG. 30 , a first PD system  100  capable of applying the PD device (PD, USB PD) according to the first to sixth embodiments includes: a monitor  110  connected to a power socket through a plug; and an external hard disk drive  120 /a set top box  130 /a laptop PC  140 /a tablet PC  150 /a smart phone  160  each connected to the monitor  110  using the USB PD cable. 
     Although the PD device (PD, USB PD) according to the first to sixth embodiments  4 A is mounted in each configuring elements, the illustration of the DC/DC converter is omitted in  FIG. 30 , but the secondary-side controller (PD CHIP)  16  is illustrated in  FIG. 30 . 
     USB DATA and DC power can be transmitted between the monitor  110  and the external hard disk drive  120 /the set top box  130 /the laptop PC  140 /the tablet PC  150 /the smart phone  160  through the USB PD cable. 
     An AC/DC converter  60  is mounted in the monitor  110 . A CPU/interface board  122  is mounted in the external hard disk drive  120 . A CPU/interface board  132  is mounted in the set top box  130 . A Narrow Voltage DC/DC (NVDC) charger  142 , a CPU  148 , a Platform Controller Hub (PCH)  147 , and an Embedded Controller (EC)  146  are mounted in the laptop PC  140 . An Application CPU (ACPU)  156 , a charger  158 , and a battery  157  are mounted in the tablet PC  150 . An ACPU  166 , a USB charger  162 , and a battery  172  are mounted in a smart phone  160 . 
     As shown in  FIG. 31 , a second PD system  200  capable of applying the PD device (PD, USB PD) according to the first to sixth embodiments includes: a USB PD adapter  230  connected to a power socket through a plug; a laptop PC  140  connected to the USB PD adapter  230  using the USB PD cable; and an external hard disk drive  120 /a monitor  110 /a tablet PC  150 /a smart phone  160  each connected to the laptop PC  140  using the USB PD cable. 
     Although the PD device (PD, USB PD) according to the first to sixth embodiments  4 A is mounted in each configuring elements, the illustration of the DC/DC converter is omitted in  FIG. 31 , but the secondary-side controller (PD CHIP)  16  is illustrated in  FIG. 31 . 
     The USB DATA and the DC power can be transmitted between the laptop PC  140  and the external hard disk drive  120 /the monitor  110 /the tablet PC  150 /the smart phone  160  through the USB PD cable. 
     An NVDC charger  142 , a CPU  148 , a PCH  147 , an EC  146 , a battery  154 , a DC/DC converter  159 , and PD CHIPs  16   1 ,  16   2  are mounted in the laptop PC  140 . A PMIC  112  is mounted in the monitor  110 . Other configurations are the same as that of the first PD system  100  ( FIG. 30 ). 
     As shown in  FIG. 32 , a third PD system  300  capable of applying the PD device (PD, USB PD) according to the first to sixth embodiments includes: a USB PD adapter (USB PD charger)  310  connected to a power socket through a plug; and an external hard disk drive  120 /a monitor  110 /a set top box  130 /a laptop PC  140 /a tablet PC  150 /a smart phone  160  each connected to the USB PD adapter (USB PD charger)  310  using the USB PD cable. 
     Although the PD device (PD, USB PD) according to the first to sixth embodiments  4 A is mounted in each configuring elements, the illustration of the DC/DC converter is omitted in  FIG. 32 , but the secondary-side controller (PD CHIP)  16  is illustrated in  FIG. 32 . 
     The USB DATA and the DC power can be transmitted between the USB PD adapter  310  (USB PD charger) and the external hard disk drive  120 /the monitor  110 /the set top box  130 /the laptop PC  140 /the tablet PC  150 /the smart phone  160  through the USB PD cable. 
     The AC/DC converter  60  is mounted in the USB PD adapter (USB PD charger)  310 . Other configurations are the same as those of the first PD system  100  ( FIG. 30 ) and the second PD system  200  ( FIG. 31 ). 
     As shown in  FIG. 33 , a fourth PD system  400  capable of applying the PD device (PD, USB PD) according to the first to sixth embodiments includes: a high-performance USB PD adapter/charger  330  connected to a power socket through a plug; and an external hard disk drive  120 /a monitor  110 /a set top box  130 /a laptop PC  140 /a tablet PC  150 /a smart phone  160  each connected to the high-performance USB PD adapter/charger  330  using the USB PD cable. 
     Although the PD device (PD, USB PD) according to the first to sixth embodiments  4 A is mounted in each configuring elements, the illustration of the DC/DC converter is omitted in  FIG. 32 , but the secondary-side controller (PD CHIP)  16  is illustrated in  FIG. 32 . 
     The USB DATA and the DC power can be transmitted between the high-performance USB PD adapter/charger  330  and the external hard disk drive  120 /the monitor  110 /the set top box  130 /the laptop PC  140 /the tablet PC  150 /the smart phone  160  through the USB PD cable. 
     The AC/DC converter  60 A including a synchronous FET switching converter is mounted in the high-performance USB PD adapter/charger  330 . Other configurations are the same as that of the third PD system  300  ( FIG. 32 ). 
     A usage example of the secondary-side controller (PD CHIP) applicable to the PD device according to the first to sixth embodiments is illustrated as shown in  FIGS. 36, 37 and 38 . 
     The PD CHIP  16 C applicable in a consumer mode for receiving the power supplied from connecting target devices (sets) is connected to the laptop PC  140  connected to the AC adapter  230 , as shown in  FIG. 34 . The laptop PC  140  can be further connected to the smart phone  160 , and the smart phone  160  can also be connected to the AC adapter  230 . 
     The PD CHIP  16 P applicable in a provider mode for delivering (providing) electric power to the connecting target devices (sets) is connected to the laptop PC  140 , as shown in  FIG. 35 . The laptop PC  140  can be further connected to the monitor  110  and the smart phone  160 . 
     The PD CHIP  16 D applicable in a dual role mode of both of the consumer mode and the provider mode is connected to the laptop PC  140  connected to the AC adapter  230 , as shown in  FIG. 36 . The laptop PC  140  can be further connected to the smart phone  160 . 
     The PD CHIP  16 D applicable in the dual role mode can be connected to the laptop PC  140 A connected to connected to the AC adapter  230 , and can be further connected to the laptop PC  140 B connected to the smart phone  160 , as shown in  FIG. 37 . 
     As shown in  FIG. 38 , the PD CHIP  16 P applicable in the provider mode for delivering (providing) electric power to the connecting target devices (sets) may be connected to the AC adapter  230 , and the AC adapter  230  may be connected to the laptop PC  140  and the smart phone  160 . 
     Seventh Embodiment 
     As shown in  FIG. 39A , a PD device  4 A according to a seventh embodiment includes: a DC/DC converter  13  disposed between an input and an output, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a power source supply circuit  10  connected between the input and the primary-side controller  30 , and configured to supply a power source to the primary-side controller  30 ; an insulating bidirectional circuit  34  connected to the output of the DC/DC converter  13 , and also connected to the output terminal through the capacitor C 2 ; and a DC/AC component separating circuit  32  which is connected to the insulating bidirectional circuit  34  and which feeds back the electric power information in the output side to the primary-side controller  30 . 
     In the seventh embodiment, the insulating bidirectional circuit  34  achieves DC feedback and AC signal separation with feedback control from the insulating bidirectional circuit  34  to the primary-side controller  30 . 
     An inductance L 3  is a separating inductance. More specifically, a filter circuit composed of the inductance L 3  and a capacitor CF separates a control signal from the DC/DC converter so that the control signal from the output is not input into the DC/DC converter. 
     In the PD device  4 A according to the seventh embodiment, the voltage is fed back from the output. Moreover, the PD device  4 A according to the seventh embodiment has an output voltage variable function. 
     In the PD device  4 A according to the seventh embodiment, the AC signal is superposed on and input into the output terminal from the outside. 
     In the PD device  4 A according to the seventh embodiment, the control signal is input into the insulating bidirectional circuit  34  through the capacitor C 2  from the output, and the electric power information in the output side is fed back to the primary-side controller  30  through the DC/AC component separating circuit  32 . The primary-side controller  30  controls ON/OFF of the MOS transistor Q 1 , thereby stabilizing the output voltage. 
     The DC/AC component separating circuit  32  includes a Low Pass Filter (LPF)  36  and a DC component eliminating circuit  38 , in the PD device  4 A according to the seventh embodiment. 
     The DC information of the output of DC/DC converter is input into the DC component eliminating circuit  38  and the LPF  36  in the DC/AC component separating circuit  32  through the insulating bidirectional circuit  34 . The input AC information of the output terminal is also input into the DC component eliminating circuit  38  and the LPF  36  in the DC/AC component separating circuit  32  through the capacitor C 2  and the insulating bidirectional circuit  34  from the output terminal. 
     The DC output of LPF  36  is fed back directly to the primary-side controller  30  as DC information (FBD). The DC information (DC component) of the output of DC/DC converter is removed in the DC component eliminating circuit  38 , and only the input AC information is fed back to the primary-side controller  30  (FBA 1 ). The input control signal from the outside of the output terminal is AC-superposed on the input AC information. 
     Furthermore, the output AC information (FBA 2 ) is fed back from the primary-side controller  30  to the output terminal through the insulating bidirectional circuit  34  and the capacitor C 2 . In the present embodiment, the output control signal is superposed on the output AC information (FBA 2 ) fed back to the output terminal from the primary-side controller  30 . 
     The PD device  4 A according to the seventh embodiment includes: a circuit configured to restore the input control signal included in the input AC information; and a circuit configured to superpose the output control signal on the output AC information from the primary-side controller  30 , in the primary-side controller  30 . 
     In the PD device  4 A according to the seventh embodiment, the input control signal superposed on the input AC information is input into the output terminal from the outside. More specifically, the input control signal is input into the insulating bidirectional circuit  24  through the capacitor C 2  from the output, the electric power information is fed back to the primary-side controller  30  through the DC/AC component separating circuit  32  from the insulating bidirectional circuit  34 , and ON/OFF of the MOS transistor Q 1  is controlled by the primary-side controller  30 , thereby stabilizing the output voltage. Moreover, the amount of current conducted to the primary-side inductance L 1  is detected by the current sensing resistor RS, and the amount of current of the primary-side overcurrent is controlled in the primary-side controller  30 . 
     The insulating bidirectional circuit  34  can bidirectionally transmit the input/output AC information with the DC information. 
     A bidirectional transformer having an insulated driver, a bidirectional device, etc. are applicable to the insulating bidirectional circuit  34 . Moreover, the insulating bidirectional circuit  34  may be composed by combining a plurality of unidirectional circuits and unidirectional elements. 
     For example, the insulating bidirectional circuit  34  may include a plurality of insulating unidirectional circuits  35 ,  37  as shown in  FIG. 39B . In the present embodiment, the insulating unidirectional circuit  35  can transmit the DC information and the input AC information from the secondary side to the primary side, and the insulating unidirectional circuit  37  can transmit the output AC information from the primary side to the secondary side. The plurality of the insulating unidirectional circuits  35 ,  37  are combined, thereby composing the insulating bidirectional circuit  34  as a consequence. 
     In the PD device  4 A according to the seventh embodiment, the control information is transmitted to the primary-side controller  30  through the DC/AC component separating circuit  32  from the insulating bidirectional circuit  34 , and thereby the output voltage and the available output current capacity (MAX value) can be varied. 
     In the PD device  4 A according to the seventh embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control from the insulating bidirectional circuit  34  to the primary-side controller  30 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the seventh embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the seventh embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13  achieved by the feedback control to the primary-side controller  30  through the capacitor C 2  and the insulation circuit  20  from the insulating bidirectional circuit  34 . 
     The PD device  4 A according to the seventh embodiment can be called merely a power delivery (PD) device since the secondary-side controller (PD CHIP)  16  can be omitted. 
     Eighth Embodiment 
     As shown in  FIG. 40 , a PD device  4 A according to an eighth embodiment includes: a DC/DC converter  13  disposed between an input and an output, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a power source supply circuit  10  connected between the input and the primary-side controller  30 , and configured to supply a power source to the primary-side controller  30 ; a secondary-side controller (PD CHIP)  16  connected to the output of the DC/DC converter  13 , and also connected to the output terminal through the capacitor C 2 ; an insulating bidirectional circuit  34  connected to the output of the DC/DC converter  13 , and also connected to the secondary-side controller (PD CHIP)  16 ; and a DC/AC component separating circuit  32  which is connected to the insulating bidirectional circuit  34  and which feeds back the electric power information in the output side to the primary-side controller  30 . Other configurations are the same as those of the seventh embodiment. 
     In the eighth embodiment, the insulating bidirectional circuit  34  achieves DC feedback and AC signal separation with feedback control from the insulating bidirectional circuit  34  to the primary-side controller  30 , in the same manner as the seventh embodiment. 
     A voltage-current control circuit for controlling the output voltage V o  and the output current I o  is included in the secondary-side controller (PD CHIP)  16 . 
     In the PD device  4 A according to the eighth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the eighth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the eighth embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification system and step-down (buck) type DC/DC converter  13  achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . 
     In the PD device  4 A according to the eighth embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the eighth embodiment can be called a USB Power Delivery (USB PD) device. 
     Ninth Embodiment 
     As shown in  FIG. 41 , a PD device  4 A according to a ninth embodiment includes: a synchronous rectification type DC/DC converter  13  disposed between an input and an output, and composed of a transformer  15 , a MOS transistor Q 3 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a power source supply circuit  10  connected between the input and the primary-side controller  30 , and configured to supply a power source to the primary-side controller  30 ; a secondary-side controller (PD CHIP)  16  connected to the output of the DC/DC converter  13 , and also connected to the output terminal through the capacitor C 2 ; an insulating bidirectional circuit  34  connected to the secondary-side controller (PD CHIP)  16 ; and a DC/AC component separating circuit  32  which is connected to the insulating bidirectional circuit  34  and which feeds back the electric power information in the output side to the primary-side controller  30 . 
     The MOS transistor Q 3  included in the synchronous rectification type DC/DC converter  13  has ON/OFF controlled by the secondary-side controller (PD CHIP)  16 . 
     Moreover, the secondary-side controller (PD CHIP)  16  can control the output voltage V o  and the output current I o . 
     The PD device  4 A according to the ninth embodiment can improve the DC/DC power conversion efficiency compared with the seventh to eighth embodiments having the diode rectification system since the synchronizing rectification method is used for the DC/DC converter instead of the diode rectification system. Other configurations are the same as those of the seventh embodiment. 
     A voltage-current control circuit for controlling the output voltage V o  and the output current I o  is included in the secondary-side controller (PD CHIP)  16 . 
     In also the ninth embodiment, the insulating bidirectional circuit  34  achieves DC feedback and AC signal separation with feedback control from the insulating bidirectional circuit  34  to the primary-side controller  30 , in the same manner as the seventh to eighth embodiments. 
     In the PD device  4 A according to the ninth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the synchronous rectification type DC/DC converter  13  is achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the ninth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the ninth embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the synchronous rectification type DC/DC converter  13  achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . 
     In the PD device  4 A according to the ninth embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the ninth embodiment can be called a USB Power Delivery (USB PD) device. 
     Tenth Embodiment 
     As shown in  FIG. 42 , a PD device  4 A according to a tenth embodiment includes an AC/DC converter connected to the AC input and composed of a fuse  11 , a choke coil  12 , a diode rectification bridge  14 , capacitors C 5 , C 6 , C 3 , etc., instead of the power source supply circuit  10  as in the ninth embodiment. 
     Moreover, an auxiliary inductance L 4  composed of the primary-side auxiliary winding in the transformer  15 , and a diode D 2  and a capacitor C 4  connected in parallel to the auxiliary inductance L 4  are provided therein, and the DC voltage VCC is supplied from the capacitor C 4  to the primary-side controller  30 . 
     Furthermore, as shown in  FIG. 42 , the PD device  4 A according to the tenth embodiment includes: a synchronous rectification type DC/DC converter  13  disposed between an output of AC/DC converter and the output, and composed of a transformer  15 , a MOS transistor Q 3 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a secondary-side controller (PD CHIP)  16  connected to the output of the DC/DC converter  13 , and also connected to the output terminal through the capacitor C 2 ; an insulating bidirectional circuit  34  connected to the secondary-side controller (PD CHIP)  16 ; and a DC/AC component separating circuit  32  which is connected to the insulating bidirectional circuit  34  and which feeds back the electric power information in the output side to the primary-side controller  30 . 
     The MOS transistor Q 3  included in the synchronous rectification type DC/DC converter  13  has ON/OFF controlled by the secondary-side controller (PD CHIP)  16 . 
     Moreover, the secondary-side controller (PD CHIP)  16  can control the output voltage V o  and the output current I°. 
     The PD device  4 A according to the tenth embodiment can improve the DC/DC power conversion efficiency compared with the seventh to eighth embodiments having the diode rectification system since the synchronizing rectification method is used for the DC/DC converter instead of the diode rectification system. Other configurations are the same as those of the seventh embodiment. 
     A voltage-current control circuit for controlling the output voltage V o  and the output current I o  is included in the secondary-side controller (PD CHIP)  16 . 
     In also the tenth embodiment, the insulating bidirectional circuit  34  achieves DC feedback and AC signal separation with feedback control from the insulating bidirectional circuit  34  to the primary-side controller  30 , in the same manner as the seventh to ninth embodiments. 
     In the PD device  4 A according to the tenth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the synchronous rectification type DC/DC converter  13  is achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the tenth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the tenth embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the synchronous rectification type and step-down (buck) type DC/DC converter  13  achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . 
     In the PD device  4 A according to the tenth embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the tenth embodiment can be called a USB Power Delivery (USB PD) device having the AC/DC converter function (AC/DC+USB PD). 
     Eleventh Embodiment 
     As shown in  FIG. 43 , a PD device  4 A according to an eleventh embodiment includes an AC/DC converter connected to the AC input and composed of a fuse  11 , a choke coil  12 , a diode rectification bridge  14 , capacitors C 5 , C 6 , C 3 , etc., instead of the power source supply circuit  10  as in the seventh embodiment. 
     Moreover, an auxiliary inductance L 4  composed of the primary-side auxiliary winding in the transformer  15 , and a diode D 2  and a capacitor C 4  connected in parallel to the auxiliary inductance L 4  are provided therein, and the DC voltage VCC is supplied from the capacitor C 4  to the primary-side controller  30 . 
     Furthermore, as shown in  FIG. 43 , the PD device  4 A according to the eleventh embodiment includes: a DC/DC converter  13  disposed between an output of AC/DC converter and an output, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; an insulating bidirectional circuit  34  connected to the output of the DC/DC converter  13 , and also connected to the output terminal through the capacitor C 2 ; and a DC/AC component separating circuit  32  which is connected to the insulating bidirectional circuit  34  and which feeds back the electric power information in the output side to the primary-side controller  30 . 
     In also the tenth embodiment, the insulating bidirectional circuit  34  achieves DC feedback and AC signal separation with feedback control from the insulating bidirectional circuit  34  to the primary-side controller  30 , in the same manner as the seventh to tenth embodiments. 
     In the PD device  4 A according to the eleventh embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control from the insulating bidirectional circuit  34  to the primary-side controller  30 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the eleventh embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the eleventh embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13  achieved by the feedback control to the primary-side controller  30  through the capacitor C 2  and the insulation circuit  20  from the insulating bidirectional circuit  34 . 
     In the PD device  4 A according to the eleventh embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the tenth embodiment can be called a USB Power Delivery (USB PD) device having the AC/DC converter function (AC/DC+USB PD). 
     Twelfth Embodiment 
     As shown in  FIG. 44 , a PD device  4 A according to a twelfth embodiment includes an AC/DC converter connected to the AC input and composed of a fuse  11 , a choke coil  12 , a diode rectification bridge  14 , capacitors C 5 , C 6 , C 3 , etc., instead of the power source supply circuit  10  as in the eighth embodiment. 
     Moreover, an auxiliary inductance L 4  composed of the primary-side auxiliary winding in the transformer  15 , and a diode D 2  and a capacitor C 4  connected in parallel to the auxiliary inductance L 4  are provided therein, and the DC voltage VCC is supplied from the capacitor C 4  to the primary-side controller  30 . 
     Furthermore, as shown in  FIG. 44 , the PD device  4 A according to the twelfth embodiment includes: a DC/DC converter  13  disposed between an output of AC/DC converter and an output, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a secondary-side controller (PD CHIP)  16  connected to the output of the DC/DC converter  13 , and also connected to the output terminal through the capacitor C 2 ; an insulating bidirectional circuit  34  connected to the secondary-side controller (PD CHIP)  16 ; and a DC/AC component separating circuit  32  which is connected to the insulating bidirectional circuit  34  and which feeds back the electric power information in the output side to the primary-side controller  30 . Moreover, the secondary-side controller (PD CHIP)  16  can control the output voltage V o  and the output current I o . Other configurations are the same as those of the seventh embodiment. 
     A voltage-current control circuit for controlling the output voltage V o  and the output current I o  is included in the secondary-side controller (PD CHIP)  16 . 
     In also the twelfth embodiment, the insulating bidirectional circuit  34  achieves DC feedback and AC signal separation with feedback control from the insulating bidirectional circuit  34  to the primary-side controller  30 , in the same manner as the seventh to eleventh embodiments. 
     In the PD device  4 A according to the twelfth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the twelfth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the twelfth embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification system and step-down (buck) type DC/DC converter  13  achieved by the feedback control from the secondary-side controller (PD CHIP)  16  to the primary-side controller  30 . 
     In the PD device  4 A according to the twelfth embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the twelfth embodiment can be called a USB Power Delivery (USB PD) device having the AC/DC converter function (AC/DC+USB PD). 
     Thirteenth Embodiment 
     As shown in  FIG. 45 , a PD device  4 A according to a thirteenth embodiment includes an AC/DC converter connected to the AC input and composed of a fuse  11 , a choke coil  12 , a diode rectification bridge  14 , capacitors C 5 , C 6 , C 3 , etc. instead of the power source supply circuit  10  as in the seventh embodiment, in the same manner as the tenth embodiment. 
     As shown in  FIG. 45 , the PD device  4 A according to the thirteenth embodiment includes an independent DC/DC converter  24  which is connected to the output of the step-down (buck) type DC/DC converter  13  and which includes the secondary-side controller (PD CHIP)  16  therein. 
     The synchronous rectification type DC/DC converter  24  is composed of the MOS transistor Q 2 , the inductance L 7 , and the secondary-side controller (PD CHIP)  16 . The secondary-side controller (PD CHIP)  16  is connected to the gate of the MOS transistor Q 2 , and the secondary-side controller (PD CHIP)  16  controls ON/OFF of the MOS transistor Q 2 . The inductance L 7  is an inductance used for the DC/DC converter  24 . 
     An inductance L 8  is a PD separating inductance. More specifically, a filter circuit composed of the inductance L 8  and a capacitor C 5  separates a control signal from the DC/DC converter so that the control signal from the output side is not input into the DC/DC converter. 
     Furthermore, as shown in  FIG. 45 , the PD device  4 A according to the thirteenth embodiment includes: A DC/DC converter  13  disposed between the output of the AC/DC converter and the output of the DC/DC converter, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a secondary-side controller (PD CHIP)  16  which is connected to the output through the capacitor C 2 , and can control an output voltage V o  and an output current I o ; an insulating bidirectional circuit  34  connected to the output of DC/DC converter  13 , and also connected to the DC/DC converter  24 ; and a DC/AC component separating circuit  32  which is connected to the insulating bidirectional circuit  34  and which feeds back the electric power information in the output side to the primary-side controller  30 . Other configurations are the same as those of the tenth embodiment. 
     In the PD device  4 A according to the thirteenth embodiment, the voltage is fed back from the output of the DC/DC converter  13 . More specifically, the electric power information is fed back from the output of the DC/DC converter  13  (secondary) side to the input (primary) side, and ON/OFF of MOS transistor Q 1  is controlled by the primary-side controller  30 , thereby stabilizing the output voltage. The amount of current conducted to the primary-side inductance L 1  in the transformer  15  is detected by the current sensing resistor RS, and the amount of current of the primary-side overcurrent is controlled in the primary-side controller  30 . 
     In the PD device  4 A according to the thirteenth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the synchronous rectification type DC/DC converter  24  is achieved by the secondary-side controller (PD CHIP)  16  included in the synchronous rectification type DC/DC converter  24 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the output. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the thirteenth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the thirteenth embodiment, the output voltage of diode rectification and step-down (buck) type DC/DC converter  13  is stabilized by the feedback control from the output of step-down (buck) type DC/DC converter to the primary-side controller  30 , and the variable function of the output voltage value and the available output current capacity (MAX value) of the synchronous rectification type DC/DC converter  24  connected to the DC/DC converter  13  is achieved by the secondary-side controller (PD CHIP)  16  included in the synchronous rectification type DC/DC converter  24 . 
     As a consequence, according to the thirteenth embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13 . 
     In the PD device  4 A according to the thirteenth embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the thirteenth embodiment can be called a USB Power Delivery (USB PD) device having the AC/DC converter function (AC/DC+USB PD). 
     Fourteenth Embodiment 
     As shown in  FIG. 46 , a PD device  4 A according to a fourteenth embodiment includes: a DC/DC converter  13  disposed between a first terminal and a second terminal, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; A power source supply circuit  10  connected between the first terminal and the primary-side controller  30 , and configured to supply a power source to the primary-side controller  30 ; an insulating bidirectional circuit  34 A which is connected to the second terminal and feeds back second terminal information to the primary-side controller  30 ; a capacitor CA for AC coupling connected to between the insulating bidirectional circuit  34 A and the primary-side controllers  30 ; and a low pass filter (LPF)  36 A connected to between the insulating bidirectional circuit  34 A and the primary-side controllers  30 . In the present embodiment, the LPF  36 A may be included in the primary-side controller  30 . 
     In the fourteenth embodiment, as shown in  FIG. 47 , the DC feedback and the AC signal common are achieved by the capacitor CA, the LPF  36 A and the insulating bidirectional circuit  34 A disposed between the primary-side controller  30  and the second terminal. 
     In the PD device  4 A according to the seventh embodiment, the AC signal is superposed on and input into the second terminal from the outside. 
     The AC signal input into the second terminal from the outside is fed back to the primary-side controller  30  through the insulating bidirectional circuit  34 A and the capacitor CA from the second terminal. The AC signal fed back to the primary-side controller  30  conducts on a connection line  30 B between the primary-side controller  30  and the insulating bidirectional circuit  34 A. 
     The DC signal in the second terminal is fed back to the primary-side controller  30  through the insulating bidirectional circuit  34 A and the LPF  36 A from the second terminal. The DC signal fed back to the primary-side controller  30  conducts on a connection line  30 A between the primary-side controller  30  and the LPF  36 A. The DC signal fed back to the primary-side controller  30  is input into an error amplifier  30 E disposed in the primary-side controller  30 , as shown in  FIG. 46 . 
     On the other hand, the AC signal transmitted to the second terminal from the primary-side controller  30  (control signal to the connecting targets (set devices) connected to the outside) is transmitted to the second terminal through the capacitor CA and the insulating bidirectional circuit  34 A from the primary-side controller  30 . 
     On the basis of the fed back DC signal and the fed back AC signal, the primary-side controller  30  controls ON/OFF of the MOS transistor Q 1 , thereby stabilizing the output voltage. 
     Moreover, in the PD device  4 A according to the fourteenth embodiment, the amount of current conducted to the primary-side inductance L 1  is detected by the current sensing resistor RS, and the amount of current, e.g. a primary-side overcurrent, is controlled in the primary-side controller  30 . 
     As a consequence, the PD device  4 A according to the fourteenth embodiment has a variable function of an output voltage value and available output current capacity (MAX value) by the primary-side controller  30 . 
     In the PD device  4 A according to the fourteenth embodiment, the control information is transmitted to the primary-side controller  30  through the insulating bidirectional circuit  34 A and the LPF  36 A from the second terminal, and thereby the output voltage and the available output current capacity (MAX value) can be varied. 
     An inductance L 3  is a separating inductance. More specifically, a filter circuit composed of the inductance L 3  and a capacitor C 1  separates a control signal from the DC/DC converter so that the control signal from the second terminal is not input into the DC/DC converter  13 . 
     A capacitor, a photo coupler, a transformer, etc. is applicable to the insulating bidirectional circuit  34 A. As usage, a bidirectional transformer having an insulated driver, a bilateral device, etc. may also be applied thereto. 
     In the PD device  4 A according to the fourteenth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control to the primary-side controller  30  through the insulating bidirectional circuit  34 A and the LPF  36 A from the second terminal. Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the second terminal. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the fourteenth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the fourteenth embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13 , achieved by the feedback control to the primary-side controller  30  from the second terminal through the insulating bidirectional circuit  34 A and the LPF  36 A. 
     In the PD device  4 A according to the fourteenth embodiment, the insulating bidirectional circuit  34 A includes a plurality of insulating unidirectional circuits  35 ,  37 , as shown in  FIG. 48A . As shown in  FIG. 48A , the insulating simplex transmission of AC+DC signal from the second terminal to the primary-side controller  30  is available in the insulating unidirectional circuit  35 , and the insulating simplex transmission of AC+DC signal from the second terminal to the primary-side controller  30  is available in the insulating unidirectional circuit  37 . 
     Moreover, in the PD device  4 A according to the fourteenth embodiment, the insulating bidirectional circuit  34 A includes a plurality of insulating unidirectional circuits  35 ,  37  and capacitors C i1 , C i2 , as shown in  FIGS. 48B and 48C . As shown in  FIGS. 48B and 48C , the insulating simplex transmission of the AC signal from the second terminal to the primary-side controller  30  is available in the insulating unidirectional circuit  35  and the capacitor C i1 , and the insulating simplex transmission of the AC signal from the second terminal to the primary-side controller  30  is available in the insulating unidirectional circuit  37  and the capacitor C i2 . The DC signal conducting between the second terminal and the primary-side controller  30  can be conducted through a DC path in the LPF  36 A and the insulating bidirectional circuit  34 A. 
     The electrodes in the primary-side controller  30  side of the capacitors C i1 , C i2  may be connected to each other in the insulating bidirectional circuit  34 A as shown in  FIG. 48B , and may be connected to each other in the insulating bidirectional circuit  34 A as shown in  FIG. 48C . 
     The PD device  4 A according to the fourteenth embodiment can be called merely a PD device (PD) in the case of connecting to the external apparatuses using the normal cable, but can be called a USB Power Delivery (USB PD) device in the case where the USB-connecting is available. 
     Fifteenth Embodiment 
     As shown in  FIG. 49 , a PD device  4 A according to a fifteenth embodiment includes: a synchronous rectification type DC/DC converter  13  disposed between a first terminal and a second terminal, and composed of a transformer  15 , a MOS transistor Q 3 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; A power source supply circuit  10  connected between the first terminal and the primary-side controller  30 , and configured to supply a power source to the primary-side controller  30 ; a secondary-side controller (PD CHIP)  16  connected to the output of the DC/DC converter  13 , and also connected to the second terminal through the capacitor C 2 ; an insulating bidirectional circuit  34 A which is connected to the secondary-side controller (PD CHIP)  16 , and feeds back second terminal information to the primary-side controller  30 ; a capacitor CA for AC coupling connected to between the insulating bidirectional circuit  34 A and the primary-side controllers  30 ; and a low pass filter (LPF)  36 A connected to between the insulating bidirectional circuit  34 A and the primary-side controllers  30 . In the present embodiment, the LPF  36 A may be included in the primary-side controller  30 . 
     The secondary-side controller (PD CHIP)  16  can control the output voltage V o  and the output current I o . 
     The PD device  4 A according to the fifteenth embodiment can improve the DC/DC power conversion efficiency compared with the fourteenth embodiment having the diode rectification system since the synchronizing rectification method is used for the DC/DC converter instead of the diode rectification system. Other configurations are the same as those of the fourteenth embodiment. 
     A voltage-current control circuit for controlling the output voltage V o  and the output current I o  is included in the secondary-side controller (PD CHIP)  16 . 
     In the fifteenth embodiment, as shown in  FIG. 49 , the DC feedback and the AC signal common are achieved by the capacitor CA, the LPF  36 A and the secondary-side controller  16  disposed between the primary-side controller  30  and the second terminal. 
     In the PD device  4 A according to the fifteenth embodiment, the AC signal is superposed on and input into the second terminal from the outside. 
     The AC signal input into the second terminal from the outside is fed back to the primary-side controller  30  through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the capacitor CA from the second terminal. The AC signal fed back to the primary-side controller  30  conducts on a connection line  30 B between the primary-side controller  30  and the insulating bidirectional circuit  34 A. 
     The DC signal in the second terminal is fed back to the primary-side controller  30  through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the LPF  36 A from the second terminal. The DC signal fed back to the primary-side controller  30  conducts on a connection line  30 A between the primary-side controller  30  and the LPF  36 A. The DC signal fed back to the primary-side controller  30  is input into an error amplifier  30 E disposed in the primary-side controller  30 , as shown in  FIG. 49 . 
     On the other hand, the AC signal transmitted to the second terminal from the primary-side controller  30  (control signal to the connecting targets (set devices) connected to the outside) is transmitted to the second terminal through the capacitor CA, the insulating bidirectional circuit  34 A and the secondary-side controller  16  from the primary-side controller  30 . 
     On the basis of the fed back DC signal and the fed back AC signal, the primary-side controller  30  controls ON/OFF of the MOS transistor Q 1 , thereby stabilizing the output voltage. 
     Moreover, the primary-side controller  30  detects the amount of the current conducted to the primary-side inductance L 1  by the current sensing resistor RS, thereby controlling the amount of the current, such as a primary-side overcurrent. 
     As a consequence, the PD device  4 A according to the fifteenth embodiment has a variable function of an output voltage value and available output current capacity (MAX value) by the primary-side controller  30 . 
     In the PD device  4 A according to the fifteenth embodiment, the control information is transmitted to the primary-side controller  30  through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the LPF  36 A from the second terminal, and thereby the output voltage and the available output current capacity (MAX value) can be varied. 
     An inductance L 3  is a separating inductance. More specifically, a filter circuit composed of the inductance L 3  and a capacitor CF separates a control signal from the DC/DC converter so that the control signal from the second terminal is not input into the DC/DC converter  13 . In the present embodiment, the capacitor C 1  can also be applied thereto, omitting the capacitor CF. 
     A capacitor, a photo coupler, a transformer, etc. is applicable to the insulating bidirectional circuit  34 A. As usage, a bidirectional transformer having an insulated driver, a bilateral device, etc. may also be applied thereto. The insulating bidirectional circuit  34 A may also be composed of a plurality of the insulating unidirectional circuits, as shown in  FIGS. 48A, 48B, and 48C . 
     In the PD device  4 A according to the fifteenth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control to the primary-side controller  30  through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the LPF  36 A from the second terminal. Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the second terminal. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the fifteenth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the fifteenth embodiment, achieved by the feedback control to the primary-side controller  30  from the second terminal through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the LPF  36 A, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13 . 
     In the PD device  4 A according to the fifteenth embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the fifteenth embodiment can be called a USB Power Delivery (USB PD) device. 
     In addition, the PD device  4 A according to the fifteenth embodiment may include an AC/DC converter connected to the AC input (first terminal) and composed of a fuse, a choke coil, a diode rectification bridge capacitor etc., instead of the power source supply circuit  10  shown in  FIG. 49 . 
     Sixteenth Embodiment 
     As shown in  FIG. 50 , a PD device  4 A according to a sixteenth embodiment includes: a DC/DC converter  13  disposed between a first terminal and a second terminal, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; A power source supply circuit  10  connected between the first terminal and the primary-side controller  30 , and configured to supply a power source to the primary-side controller  30 ; a secondary-side controller (PD CHIP)  16  connected to the output of the DC/DC converter  13 , and also connected to the second terminal through the capacitor C 2 ; an insulating bidirectional circuit  34 A which is connected to the secondary-side controller (PD CHIP)  16 , and feeds back second terminal information to the primary-side controller  30 ; a capacitor CA for AC coupling connected to between the insulating bidirectional circuit  34 A and the primary-side controllers  30 ; and a low pass filter (LPF)  36 A connected to between the insulating bidirectional circuit  34 A and the primary-side controllers  30 . In the present embodiment, the LPF  36 A may be included in the primary-side controller  30 . 
     The secondary-side controller (PD CHIP)  16  can control the output voltage V o  and the output current I o , and a voltage-current control circuit for controlling the output voltage V o  and the output current I o  is included in the secondary-side controller (PD CHIP)  16 . 
     Also in the sixteenth embodiment, as shown in  FIG. 50 , the DC feedback and the AC signal common are achieved by the capacitor CA, the LPF  36 A and the secondary-side controller  16  disposed between the primary-side controller  30  and the second terminal, as in the case of the fifteenth embodiment. Other configurations are the same as those of the fifteenth embodiment. 
     In the PD device  4 A according to the sixteenth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control to the primary-side controller  30  through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the LPF  36 A from the second terminal. Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the second terminal. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the sixteenth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the sixteenth embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13 , achieved by the feedback control to the primary-side controller  30  from the second terminal through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the LPF  36 A. 
     In the PD device  4 A according to the sixteenth embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the fifteenth embodiment can be called a USB Power Delivery (USB PD) device. 
     Seventeenth Embodiment 
     As shown in  FIG. 51 , a PD device  4 A according to a seventeenth embodiment includes an AC/DC converter connected to the AC input (first terminal) and composed of a fuse  11 , a choke coil  12 , a diode rectification bridge  14 , capacitors C 5 , C 6 , C 3 , etc., instead of the power source supply circuit  10  as in the sixteenth embodiment. 
     Moreover, an auxiliary inductance L 4  composed of the primary-side auxiliary winding in the transformer  15 , and a diode D 2  and a capacitor C 4  connected in parallel to the auxiliary inductance L 4  are provided therein, and the DC voltage VCC is supplied from the capacitor C 4  to the primary-side controller  30 . 
     Furthermore, as shown in  FIG. 51 , the PD device  4 A according to the seventeenth embodiment includes: a DC/DC converter  13  disposed between the output of AC/DC converter and a second terminal, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a secondary-side controller (PD CHIP)  16  connected to the output of the DC/DC converter  13 , and also connected to the second terminal through the capacitor C 2 ; an insulating bidirectional circuit  34 A which is connected to the secondary-side controller (PD CHIP)  16 , and feeds back second terminal information to the primary-side controller  30 ; a capacitor CA for AC coupling connected to between the insulating bidirectional circuit  34 A and the primary-side controllers  30 ; and a low pass filter (LPF)  36 A connected to between the insulating bidirectional circuit  34 A and the primary-side controllers  30 . In the present embodiment, the LPF  36 A may be included in the primary-side controller  30 . Other configurations are the same as those of the sixteenth embodiment. 
     In the PD device  4 A according to the seventeenth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control to the primary-side controller  30  through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the LPF  36 A from the second terminal. Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the second terminal. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the seventeenth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     According to the seventeenth embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13 , achieved by the feedback control to the primary-side controller  30  from the second terminal through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the LPF  36 A. 
     In the PD device  4 A according to the seventeenth embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the thirteenth embodiment can be called a USB Power Delivery (USB PD) device having the AC/DC converter function (AC/DC+USB PD). 
     Eighth Embodiment 
     As shown in  FIG. 52 , a PD device  4 A according to an eighteenth embodiment includes an independent DC/DC converter  24  which is connected to the output of the step-down (buck) type DC/DC converter  13  and which includes the secondary-side controller (PD CHIP)  16  therein. Moreover, the PD device  4 A according to the eighteenth embodiment includes an AC/DC converter connected to the AC input (first terminal) and composed of a fuse  11 , a choke coil  12 , a diode rectification bridge  14 , capacitors C 5 , C 6 , C 3 , as in the case of the seventeenth embodiment. 
     The synchronous rectification type DC/DC converter  24  is composed of the MOS transistor Q 2 , the inductance L 7 , and the secondary-side controller (PD CHIP)  16 . The secondary-side controller (PD CHIP)  16  is connected to the gate of the MOS transistor Q 2 , and the secondary-side controller (PD CHIP)  16  controls ON/OFF of the MOS transistor Q 2 . The inductance L 7  is an inductance used for the DC/DC converter  24 . 
     An inductance L 8  is a PD separating inductance. More specifically, a filter circuit composed of the inductance L 8  and a capacitor CF separates a control signal from the DC/DC converter so that the control signal from the second terminal side is not input into the DC/DC converter  24 . 
     Furthermore, as shown in  FIG. 52 , the PD device  4 A according to the eighteenth embodiment includes: a DC/DC converter  13  disposed between the output of the AC/DC converter and the output of the DC/DC converter, and composed of a transformer  15 , a diode D 1 , a capacitor C 1 , and a MOS transistor Q 1  and a resistor RS connected in series between a primary-side inductance L 1  of the transformer  15  and a ground potential; a primary-side controller  30  configured to control the MOS transistor Q 1 ; a secondary-side controller (PD CHIP)  16  DC-connected to the second terminal, and AC-connected through the capacitor C 2 ; An insulating bidirectional circuit  34 A which is connected to the secondary-side controller (PD CHIP)  16 , and feeds back second terminal information to the primary-side controller  30 ; a capacitor CA for AC coupling connected to between the insulating bidirectional circuit  34 A and the primary-side controllers  30 ; and a low pass filter (LPF)  36 A connected to between the insulating bidirectional circuit  34 A and the primary-side controllers  30 . In the present embodiment, the LPF  36 A may be included in the primary-side controller  30 . 
     An inductance L 8  is a separating inductance. More specifically, a filter circuit composed of the inductance L 8  and a capacitor CF separates a control signal from the DC/DC converter so that the control signal from the second terminal side is not input into the DC/DC converter  24 . Other configurations are the same as those of the seventeenth embodiment. 
     A voltage-current control circuit for controlling the output voltage V o  and the output current I o  is included in the secondary-side controller (PD CHIP)  16 . 
     In the eighteenth embodiment, as shown in  FIG. 52 , the DC feedback and the AC signal common are achieved by the capacitor CA, the LPF  36 A and the secondary-side controller  16  disposed between the primary-side controller  30  and the second terminal. 
     The AC signal input into the second terminal from the outside is fed back to the primary-side controller  30  through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the capacitor CA from the second terminal. The AC signal fed back to the primary-side controller  30  conducts on a connection line  30 B between the primary-side controller  30  and the insulating bidirectional circuit  34 A. 
     The DC signal in the second terminal is fed back to the primary-side controller  30  through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the LPF  36 A from the second terminal. The DC signal fed back to the primary-side controller  30  conducts on a connection line  30 A between the primary-side controller  30  and the LPF  36 A. The DC signal fed back to the primary-side controller  30  is input into an error amplifier  30 E disposed in the primary-side controller  30 , as shown in  FIG. 52 . 
     On the other hand, the AC signal transmitted to the second terminal from the primary-side controller  30  (control signal to the connecting targets (set devices) connected to the outside) is transmitted to the second terminal through the capacitor CA, the insulating bidirectional circuit  34 A and the secondary-side controller  16  from the primary-side controller  30 . 
     On the basis of the fed back DC signal and the fed back AC signal, the primary-side controller  30  controls ON/OFF of the MOS transistor Q 1 , thereby stabilizing the output voltage. 
     Moreover, the primary-side controller  30  detects the amount of the current conducted to the primary-side inductance L 1  by the current sensing resistor RS, thereby controlling the amount of the current, such as a primary-side overcurrent. 
     As a consequence, the PD device  4 A according to the eighteenth embodiment has a variable function of an output voltage value and available output current capacity (MAX value) by the primary-side controller  30 . 
     In the PD device  4 A according to the eighteenth embodiment, the control information is transmitted to the primary-side controller  30  through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the LPF  36 A from the second terminal, and thereby the output voltage and the available output current capacity (MAX value) can be varied. 
     A capacitor, a photo coupler, a transformer, etc. is applicable to the insulating bidirectional circuit  34 A. As usage, a bidirectional transformer having an insulated driver, a bilateral device, etc. may also be applied thereto. Moreover, the insulating bidirectional circuit  34 A may also be composed of a plurality of the insulating unidirectional circuits, as shown in  FIGS. 48A, 48B, and 48C . 
     In the PD device  4 A according to the eighteenth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the step-down (buck) type DC/DC converter  13  is achieved by the feedback control to the primary-side controller  30  through the secondary-side controller  16 , the insulating bidirectional circuit  34 A and the LPF  36 A from the second terminal. Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the second terminal. 
     As the relationship between the output voltage V o  and the output current I o  obtained by using the PD device  4 A according to the eighteenth embodiment, there can be adopted various shape, e.g. a rectangular shape as shown in  FIG. 3A , an inverted trapezoidal shape as shown in  FIG. 3B , an inverted triangle shape as shown in  FIG. 3C , a trapezoidal shape as shown in  FIG. 3D , and a pentagonal shape as shown in  FIG. 3E . 
     In the PD device  4 A according to the eighteenth embodiment, the variable function of the output voltage value and the available output current capacity (MAX value) of the synchronous rectification type DC/DC converter  24  is achieved by the secondary-side controller (PD CHIP)  16  included in the synchronous rectification type DC/DC converter  24 . Accordingly, the relationship between the output voltage V o  and the output currents I o  can be varied (variable function) in accordance with loads (e.g., smart phones, laptop PCs, tablet PCs, etc.) connected to the second terminal. 
     According to the eighteenth embodiment, the output voltage of diode rectification and step-down (buck) type DC/DC converter  13  is stabilized by the feedback control from the output of step-down (buck) type DC/DC converter to the primary-side controller  30 , and the variable function of the output voltage value and the available output current capacity (MAX value) of the synchronous rectification type DC/DC converter  24  connected to the DC/DC converter  13  is achieved by the secondary-side controller (PD CHIP)  16  included in the synchronous rectification type DC/DC converter  24 . 
     As a consequence, according to eighteenth embodiment, there can be provided the PD device having the variable function of the output voltage value and the available output current capacity (MAX value) of the diode rectification and step-down (buck) type DC/DC converter  13 . 
     In the PD device  4 A according to the eighteenth embodiment, since the secondary-side controller (PD CHIP)  16  is able to USB-connect, the PD device  4 A according to the thirteenth embodiment can be called a USB Power Delivery (USB PD) device having the AC/DC converter function (AC/DC+USB PD). 
     A point that the PD device according to the seventh to eighth embodiments can also be included in the AC adapter is the same as that of the first to sixth embodiments. Accordingly, the duplicated description thereof is omitted hereinafter. 
     A point that the PD device according to the seventh to eighth embodiments can also be included in the electronic apparatuses is the same as that of the first to sixth embodiments. Accordingly, the duplicated description thereof is omitted hereinafter. 
     A point that the PD device according to the seventh to eighth embodiments can also apply the protection function thereto is the same as that of the first to sixth embodiments. Accordingly, the duplicated description thereof is omitted hereinafter. 
     The Plug structure applicable to the adapter and the electronic apparatuses including the PD device according to the seventh to eighth embodiments is the same as that of the first to sixth embodiments. Accordingly, the duplicated description thereof is omitted hereinafter. 
     A point that the PD device according to the seventh to eighth embodiments can also apply the PD system thereto is the same as that of the first to sixth embodiments. Accordingly, the duplicated description thereof is omitted hereinafter. 
     As explained above, according to the present invention, there is provided the PD device, the AC adapter, the electronic apparatus, and the PD system each which can control the variable function of the output voltage value and the available output current capacity (MAX value). 
     Other Embodiments 
     While the solution testing equipments are described in accordance with the embodiments, it should be understood that the description and drawings that configure part of this disclosure are merely instances, and are not intended to limit the present invention. This disclosure makes clear a variety of alternative embodiments, working examples, and operational techniques for those skilled in the art. 
     Such being the case, the present invention covers a variety of embodiments, whether described or not.