PATENT DOCUMENT

Publication Number: US-9866016-B2
Application Number: US-201514793601-A
Country: US
Kind Code: B2

Title: Multiport power converter with load detection capabilities

Abstract:
Power converters are provided that convert alternating current (AC) power to direct current (DC) power. A power converter may have multiple ports. Each port may have an associated connector with multiple power and data terminals. When an electronic device is connected to a given port, the electronic device draws DC power from the power converter. To ensure that the capacity of the power converter is not exceeded when multiple devices are connected to the ports of the power converter, the power converter may actively monitor its ports for active loads. Load detection circuitry can determine what number of ports are active. Control circuitry can compute a per-port available DC power level based on the number of active ports and can provide this information to connected devices.

Claims:
What is claimed is: 
     
       1. A method of managing power availability for an external device, the method comprising:
 by a power managing device: 
 determining a number of connected ports, wherein: i) a plurality of ports of the power managing device includes the connected ports, ii) each port of the connected ports is connected to an active load, and iii) a first port of the connected ports comprises: 1) a power terminal, 2) a ground terminal, and 3) a data terminal; 
 reconfiguring a power output of the power managing device based on a per-port available power level of the power managing device that corresponds to the number of connected ports, the power output including a per-port power level, wherein the per-port power level comprises a fraction of the total available power for the plurality of ports relative to the number of connected ports; 
 communicating the per-port power level over the first port using the data terminal; and 
 providing power over the first port corresponding to the per-port power level. 
 
     
     
       2. The method of  claim 1 , further comprising:
 providing, using adjustable voltage divider circuitry, a code to an external device associated with the active load, wherein the code is provided to the external device using an electrical signal. 
 
     
     
       3. The method of  claim 2 , wherein the code indicates to the external device the per-port available power level of the power managing device. 
     
     
       4. The method of  claim 3 , wherein the code is provided to the external device via the data terminal simultaneous to the external device receiving power from the power terminal. 
     
     
       5. An apparatus configured to provide power-related data to a device, the apparatus comprising:
 load detection circuitry configured to detect when the device is connected to the apparatus; 
 control circuitry configured to provide a power availability indication to the device based in part on a number of active loads connected to the apparatus, wherein the power availability indication is provided to the device using an electrical signal over a data terminal, wherein the power availability indication corresponds to a per-port available power level for at least one port of the plurality of ports, and wherein the per-port power level comprises a fraction of the total available power for the plurality of ports relative to a number of connected ports; and 
 a plurality of ports, wherein a first port of the plurality of ports comprises: i) a power terminal, ii) a ground terminal, and iii) the data terminal. 
 
     
     
       6. The apparatus of  claim 5 , wherein:
 the control circuitry is configured to adjust a voltage at the data terminal to advertise the per-port available power level via the data terminal. 
 
     
     
       7. The apparatus of  claim 5 , wherein the load detection circuitry further comprises a plurality of control switches, each control switch of the plurality of control switches being associated with a port of the plurality of ports. 
     
     
       8. The apparatus of  claim 5 , wherein the load detection circuitry comprises a plurality of current-sensing resistors, each current-sensing resistor of the plurality of current-sensing resistors being associated with a port of the plurality of ports. 
     
     
       9. The apparatus of  claim 5 , wherein the load detection circuitry includes a plurality of current-limited voltage regulators and at least one of the current-limited voltage regulators provides a power output to the device. 
     
     
       10. The apparatus of  claim 9 , wherein the load detection circuitry further includes a plurality of switches, each switch of the plurality of switches having a terminal that is connected to an output of at least one of the plurality of current-limited voltage regulators. 
     
     
       11. The apparatus of  claim 5 , wherein the control circuitry comprises a digital-to-analog converter configured to provide at least one analog voltage to the data terminal of the apparatus to advertise the per-port available power level. 
     
     
       12. The apparatus of  claim 5 , further comprising an alternating current to direct current converter. 
     
     
       13. A power management device comprising:
 a plurality of ports, wherein a first port of the plurality of ports comprises: i) a power terminal, ii) a ground terminal, and iii) a data terminal; and 
 control circuitry configured to:
 provide a per-port available power level over the data terminal of the first port of the plurality of ports of the power management device based on a number of active loads that are connected to the plurality of ports, wherein the per-port power level comprises a fraction of the total available power for the plurality of ports relative to the number of active loads. 
 
 
     
     
       14. The power management device of  claim 13 , wherein the control circuitry is further configured to provide a code to an external device via the data terminal of the first port of the plurality of ports, wherein the code is provided using an electrical signal. 
     
     
       15. The power management device of  claim 14 , wherein the power management device is configured to provide the per-port available power level simultaneous to providing power to at least one of the active loads. 
     
     
       16. The power management device of  claim 13 , wherein the control circuitry includes adjustable voltage divider circuitry. 
     
     
       17. The power management device of  claim 16 , wherein the adjustable voltage divider circuitry comprises a plurality of resistors and at least one transistor having a gate that receives a control signal from the control circuitry.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 12/566,594, filed Sep. 24, 2009, entitled “MULTIPORT POWER CONVERTER WITH LOAD DETECTION CAPABILITIES”, the contents of which are incorporated herein by reference in its entirety for all purposes. 
    
    
     FIELD 
     This relates to power converters, and more particularly, to multiport power converters. 
     BACKGROUND 
     Power converter circuitry can be used to convert alternating current (AC) power into direct current (DC) power. AC power is typically supplied from wall outlets and is sometimes referred to as line power. Electronic devices include circuitry that runs from DC power. The DC power that is created by an AC-to-DC power converter may be used to power an electronic device. The DC power that is created may also be used to charge a battery in an electronic device. 
     In some applications, AC to DC power converter circuitry may be incorporated into an electronic device. For example, desktop computers often include AC to DC power converter circuitry in the form of computer power supply units. A computer power supply unit has a socket that receives an AC power cord. With this type of arrangement, the AC power cord may be plugged directly into the rear of the computer to supply AC power without using an external power converter. 
     Although desktop computers are large enough to accommodate internal power supplies, other devices such as handheld electronic devices and portable computers are not. As a result, typical handheld electronic devices and laptop computers require the use of external power converters. When untethered from the power converter, a handheld electronic device or portable computer may be powered by an internal battery. When AC line power is available, the power converter is used to convert AC power into DC power for the electronic device. 
     Compact AC-DC power converter designs are typically based on switched-mode power supply architectures. Switched-mode power converters contain switches such as transistor-based switches that work in conjunction with energy storage components such as inductive and capacitive elements to regulate the production of DC power from an AC source. A feedback path may be used to tap into the converter output and thereby ensure that a desired DC voltage level is produced under varying loads. 
     Some power converters have more than one port. This allows multiple devices to be powered at a single time, but requires that the power converter be capable of delivering sufficient power to satisfy a worst-case scenario when all ports are occupied. The need to over-provision a power converter in this way to accommodate worst-case scenarios can lead to undesirable increases in the size and cost of the power converter. 
     SUMMARY 
     An alternating-current (AC) to direct-current (DC) power converter may have multiple ports. The ports may have connectors such as universal serial bus connectors that allow cellular telephones, media players, or other devices to be connected to the power converter. When a port is occupied by an electronic device, DC power may be conveyed to that electronic device to power the electronic device. For example, a battery in the electronic device may be recharged. 
     In some situations, only a single port will be occupied. In other situations, a user may plug electronic devices into two or more ports. Because the resources of the power converter are limited, there may be a desire to limit the amount of DC power that is delivered to each port when all of the ports are occupied. 
     The power converter may contain load detection circuitry. For example, voltage detector circuitry in a control circuit may monitor the voltage drop that develops across current sensing resistors that are connected in series with the ports of the power converter. When a current is sensed using one of the current sensing resistors, the control circuitry can conclude that an active load is connected to the power converter. 
     More sensitive load current measurements may be made using a control switch and a current-limited voltage regulator. A current-limited voltage regulator may be coupled to a positive power supply output terminal in a port. The switch may be connected in series with the output terminal and may be periodically opened using the control circuitry. The voltage regulator may be based on a booster circuit that produces an output voltage that is larger than the nominal power supply voltage on the output terminal. When the switch is opened, control circuitry in the power converter can monitor the voltage on the output terminal. If no load is present, the output voltage will rise to the value produced at the output of the current-limited voltage regulator booster circuit. If an electronic device is connected to power converter, the current drawn by the electronic device will exceed the capacity of the voltage regulator, causing the output voltage to sag. 
     The power converter can use the current sensing resistors and other load detection circuitry to monitor the ports in the power converter and thereby determine what number of ports are connected to electronic devices or other active loads. The power converter can then compute the amount of available power per port (i.e., the per-port available DC power) based on the number of active ports. 
     The amount of power that is delivered to each electronic device can be regulated using control switches. Each electronic device that is connected to the power converter can also be informed of the per-port available power level. This information can be conveyed to the electronic devices using voltage codes (as an example). A pair of voltages may, for example, be produced on a pair of data lines in each port. More complex digital communications schemes may also be used to convey per-port available power information (e.g., serial and parallel buses, bidirectional and unidirectional paths, links that use synchronous or asynchronous communications, etc). 
     Further features of the invention, its nature and various advantages will be more apparent from the accompanying drawings and the following detailed description of the preferred embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a diagram of a system including a multiport power converter to which a single electronic device has been attached in accordance with an embodiment of the present invention. 
         FIG. 1B  is a diagram of a system including a multiport power converter to which multiple electronic devices have been attached in accordance with an embodiment of the present invention. 
         FIG. 2  is a circuit diagram of an illustrative multiport power converter in accordance with an embodiment of the present invention. 
         FIG. 3  is a circuit diagram of illustrative circuitry that may be used in a multiport power converter to convey port power capacity information to equipment that is connected to the power converter in accordance with an embodiment of the present invention. 
         FIG. 4  is a circuit diagram of a configurable voltage divider with multiple control transistors that may be used in a multiport power converter to convey port power capacity information to equipment that is connected to the power converter in accordance with an embodiment of the present invention. 
         FIG. 5  is a circuit diagram of illustrative control circuitry and digital-to-analog converter circuitry that may be used in a multiport power converter to convey port power capacity information to equipment that is connected to the power converter in accordance with an embodiment of the present invention. 
         FIG. 6  is a flow chart of illustrative steps involved in operating multiport power converter circuitry in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Power converters can be used to convert alternating current (AC) power into direct current (DC) power. The DC power that is produced by a power converter can be used to power an electronic device. When powered in this way, a rechargeable battery in the electronic device may be recharged. 
     Portable power converters are often used to power portable electronic devices. These portable electronic devices may include laptop computers, handheld electronic device, cellular telephone, media player, accessories, etc. 
     To reduce size and save weight, AC-DC power converters may be formed using switched-mode power supply architectures. In AC-DC power converters having switched-mode power supply designs, transistor-based switches are used in conjunction with energy storage components such as inductors and capacitors to regulate the production of DC power from an AC source. 
     Size and weight can be minimized by ensuring the transistor-based switches, energy storage components, and other circuitry of a given power converter are not overly large. In general, these components should be sized according to the expected power delivery requirements for the power converter. 
     Conventional power converters are often provided with hardwired cables and connectors. For example, a conventional power converter may have an AC connector that fits into a wall outlet and may have a DC connector that fits into a particular type of electronic device. The AC connector may be provided at the end of an AC power cord. The DC connector may be provided at the end of a DC power cable that couples the DC connector to the main body of the power converter. A user who desires to power the electronic device from a conventional power converter of this type can plug the AC connector into a wall outlet and can plug the DC connector into a mating connector on the electronic device. Conventional power converters such as these are only compatible with a particular type of electronic device and can only be used to power a single electronic device at one time. 
     To address these shortcomings, it may be desirable to provide more flexible power converters. For example, a power converter can be provided with multiple ports to which DC power cables can be connected. A power converter may, for example, have multiple Universal Serial Bus (USB) ports. Each USB port may have an associated connector that is adapted to receive a mating USB connector on a USB cable. If the user desires to power a single electronic device, that electronic device can be coupled to the power converter by plugging one end of a cable into the electronic device and by plugging the other end of the cable into one of the USB ports on the power converter. Because the power converter has multiple ports, it is also possible to power multiple electronic devices at the same time. If, for example, a user desires to power two devices simultaneously, a first device may be powered using a first of the USB ports on the power converter and a second device may be powered using a second of the USB ports on the power converter. 
     To ensure proper operation of the power converter, the power converter must have the capacity to satisfy the power demands of the electronic devices that are connected to the power converter. To avoid over-provisioning the power converter and to thereby allow the size and weight of the power converter to be minimized, it may be desirable to provide the power converter with intelligent load detection and power delivery capabilities. Particularly when the power converter has multiple ports, the power converter may sometimes be needed to supply different amounts of power to different ports. Load detection and power delivery adjustment capabilities allow the power converter and attached electronic devices to be reconfigured to meet changing needs. 
     Consider, as an example, power converter  12  of  FIGS. 1A and 1B . In the situation illustrated in  FIG. 1A , there is only one electronic device  10  that is connected to power converter  12  (i.e., device A). In the situation illustrated in  FIG. 1B , there are two electronic devices  10  that have been connected to  FIG. 1B  (i.e., device A and device B). Devices  10  may be cellular telephones, media players, portable computers, handheld computing equipment, or other electronic devices. Power converter  12  can sense which ports are active and can use each port to deliver an appropriate amount of power so that the capacity of power converter  12  is not exceeded. 
     For example, in the situation of  FIG. 1A , power converter  12  can deliver 10 W of power to device A, whereas in the situation of  FIG. 1B , power converter  12  can deliver 5 W of power to device A and 5 W of power to device B. In this example, power converter  12  has a maximum capacity of 10 W. When only a single device is drawing power, this capacity can be dedicated to powering that single device (e.g., device A of  FIG. 1A ). When two devices are drawing power as shown in  FIG. 1B , the 10 W total capacity of converter  12  can be shared between device A and device B. To ensure that devices A and B do not draw more than 5 W each, devices A and B may be informed by converter  12  that there is only a maximum power available of 5 W per port. Power regulation circuitry can also be used in converter  12  to ensure that per-port power limits are not exceeded. 
     Converter  12  can inform attached devices of the available per-port power limit using voltage codes, resistive codes, serial or parallel digital communications, using asynchronous communications, using synchronous communications, etc. Prior to communicating the maximum per-port available power to attached devices, converter  12  can examine each port to determine whether a load is attached. From this load monitoring operation, converter  12  can calculate how many devices are connected to converter  12 . By determining what number of devices are connected to converter  12  using load detection circuitry, converter  12  and can use this information to determine the maximum per-port available power (i.e., by dividing the maximum capacity of converter  12  by the number of connected devices). 
     As shown in  FIGS. 1A and 1B , AC power can be provided to converter  12  from AC source  14  (e.g., an AC wall outlet). The AC line power from outlet  14  may be converted into DC power by converter  12  (e.g., using a switched-mode power supply design). Although AC-DC converters are sometimes described herein as an example, converter  12  may, in general, be any suitable type of converter (e.g., a DC-DC converter, etc.). Converter  12  may have multiple ports (e.g., port A, port B, etc.). There may be, for example, two ports in converter  12 , three ports, four ports, more than four ports, etc. Arrangements in which converter  12  has two ports are sometimes described herein as an example. 
     As shown in  FIGS. 1A and 1B , there may be connectors associated with the ports of converter  12 . For example, connectors  20 A may be associated with a first port, connector  20 B may be associated with a second port, etc. 
     Electronic devices  10  may also have connectors (e.g.,  28 A,  28 B, etc.). Cables such as cables  18 A and  18 B may be used to interconnect converter  12  and devices  10 . For example, cable  18 A may have a first connector  22 A that plugs into mating connector  20 A of converter  12  and may have a second connector  24 A that plugs into mating connector  28 A of device  10 . Cable portion  26 A may contain conductive lines (e.g., wires) that connect the terminals of connector  22 A to the terminals of connector  24 A. Device B and other devices may likewise be coupled to converter  12 . For example, device B may have a connector  28 B that is coupled to connector  20 B of a second port in converter  12  using connector  24 B, cable portion  26 B, and connector  22 B of cable  18 B, as shown in  FIG. 1B . The use of cables such as cables  18 A and  18 B to connect one or more devices  10  to respective ports of converter  12  is merely illustrative. If desired, converter  12  may have ports that receive electronic devices  10  directly (with no intervening cables) or that are connected to devices  10  using hardwired cables (e.g., cables that are integrated with converter  12  and that do not include connectors such as connectors  22 A and  22 B). 
     The connectors of converter  12  such as connectors  20 A and  20 B may be USB connectors (e.g., female USB connectors for receiving mating male USB plugs on cables  18 A and  18 B). The connectors on devices  10  may be USB connectors, 30-pin connectors, or other suitable connectors. 
     Illustrative circuitry for power converter  12  is shown in  FIG. 2 . Power converter  12  of  FIG. 2  is a two port power converter that converts AC power from AC source  14  to DC power on ports A and B. This is, however, merely illustrative. In general, power converters, which are sometimes referred to as power adapters, can be used to convert any suitable types of power. For example, a power converter may be used to boost or reduce a DC power level. Power converters such as power converter  12  of  FIG. 2  that can be used in converting AC power to DC power are sometimes described herein as an example. In general, however, the power converter circuitry may include circuitry for transforming any suitable input signal (e.g., AC or DC currents and voltages) into any suitable output signal (e.g., boosted, reduced, or otherwise transformed AC or DC currents and voltages). The use of power converters such as AC-to-DC power converters that produce regulated DC output voltages from AC input signals is merely illustrative. 
     As shown in  FIG. 2 , power converter  12  may be plugged into a source of AC line power (source  14 ) such as a wall outlet. The AC power source may provide power at 120 volts or 240 volts (as examples). Circuitry in the power converter such as AC-DC power converter circuit  122  may convert the AC line power that is received into DC power. For example, an AC to DC power converter may receive AC line power at an input and may supply DC power at a corresponding output. The output voltage level may be 12 volts, 5 volts, or any other suitable DC output level. 
     The circuitry of AC-DC power converter circuit  122  may be based on a switched mode power supply architecture. Switched mode power supplies use switches such as metal-oxide-semiconductor power transistors and associated control schemes such as pulse-width modulation control schemes or frequency modulation control schemes to implement power conversion functions in relatively compact circuits. When the switching circuitry has a first configuration, power is transferred from a power source to a storage element such as an inductor (e.g., a transformer) or a capacitor. When the switching circuitry has a second configuration, power is released from the storage element into a load. Feedback may be used to regulate the power transfer operation and thereby ensure that the output voltage is maintained at a desired level. Examples of switched mode power supply topologies that may be used in a power converter include buck converters, boost converters, flyback converters, etc. 
     With one suitable arrangement, which is sometimes described herein as an example, AC to DC power converter circuit  122  may be implemented using a voltage rectifier and flyback converter. The voltage rectifier converts AC line power from AC source  14  into DC power at a relatively high voltage level. The flyback converter portion of the power converter steps down the DC power at the output of the rectifier circuit to 12 volts, 5 volts, or other suitably low level for operating circuitry in an electronic device. This low level DC output voltage may be presented across outputs  64  and  70 . If desired, other power converter architectures may be used. The use of a switched mode power converter arrangement that is based on a flyback converter design is merely illustrative. 
     Load detection circuitry may be provided in power converter  12  to allow power converter  12  to detect which ports are occupied by attached loads (i.e., which ports are coupled to electronic devices  10  of  FIGS. 1A and 1B ). In general, an AC to DC power converter or other circuit that includes load detection circuitry may supply DC power to any suitable load. Arrangements in which electronic devices  10  serve as loads for power converter  12  are sometimes described herein as examples. Electronic devices that may receive DC power from power converter  12  include a handheld computer, a miniature or wearable device, a portable computer, a desktop computer, a router, an access point, a backup storage device with wireless communications capabilities, a mobile telephone, a music player, a remote control, a global positioning system device, a device that combines the functions of one or more of these devices, etc. 
     Electronic devices  10  (not shown in  FIG. 2 ) may be connected to the terminals of ports A and B. Only two ports are shown in  FIG. 2 , but power converter  12  may have additional ports if desired. Each electronic device  10  may have a battery for use in powering the device when unattached to power converter  12 . When power converter  12  is plugged into AC power source  14  and when a given electronic device is connected to power converter  12 , power converter  12  can transform AC power that is received from AC power source  14  into DC power for that device. 
     Each port in converter  12  may have a connector. The connectors may have any suitable number of terminals. For example, devices  10  may each have a 30-pin connector universal serial bus (USB) port into which a USB cable may be plugged. The USB cable may be used to convey DC power between a respective one of connectors  20 A and  20 B in power converter  12  and electronic device  10 . In the example of  FIG. 2 , each port and its associated connector in converter  12  has four USB-type terminals. These four terminals include two power terminals P (positive power) and G (ground). These four terminals also include two data lines DP and DN. When a mating USB plug is connected, power can be delivered to a connected electronic device over the P and G power lines. Data lines DP and DN may be used to convey information to the attached device (e.g., information on a desired power draw setting for the attached device). 
     As shown in  FIG. 2 , the positive power terminal P in connector  20 B may be connected to positive power supply line  72 A and the positive power terminal P in connector  20 A may be connected to positive power supply line  72 B. Lines  72 A and  72 B may be use to convey a positive DC voltage at 12 volts, 5 volts, or other suitable positive DC voltage level. This DC voltage level is sometimes referred to as Vbus (i.e., Vbusa for port A and Vbusb for port B) and corresponding lines  73 A and  73 B are sometimes referred to as power supply buses or output lines. The ground terminal G in connector  20 B may be connected to ground power supply line  74 B and the ground terminal G in connector  20 A may be connected to ground power supply line  74 A. Ground lines  74 A and  74 B may be coupled to ground nodes  75 A and  75 B and to ground output  70  of AC-DC power converter circuit  12  and may be used to convey a ground voltage at 0 volts or other suitable ground voltage level. 
     When connected to power converter  12 , each electronic device  10  may receive DC power through the power pins of the USB connector and cable (as an example). The use of a USB connector to connect power converter  12  and electronic device  10  is, however, merely illustrative. Any suitable plugs, jacks, ports, pins, or other connectors, may be used to interconnect power converter  12  and electronic devices if desired. Similarly, a hardwired connection or a suitable plug, jack, port, pin structure, or other connector may be used to connect power converter  12  to power source  14 . 
     AC-DC power converter circuit  122  may convert AC power from AC source  14  to DC power on output paths  64  and  70 . Path  64  may be a positive power supply line that is coupled to converter output line  73 A via series-connected current sensing resistor RA and switch SWA and that is coupled to converter output line  73 B via series-connected current sensing resistor RB and switch SWB. The circuitry of converter  12  such as resistors RA and RB can be used to detect when an electronic device is attached to a port. When an active device is attached to a given port, current flows across the current sensing resistor that is associated with that port. For example, when a device is connected to port A, current may flow across resistor RA. This can produce a measurable voltage drop across the voltage probe lines that are connected across the resistor. 
     As shown in  FIG. 2 , voltage measurements lines  80 A and  82 A may be used to route voltage measurement signals from resistor RA to control circuitry  54 , whereas voltage measurement lines  80 B and  82 B may be used to route voltage measurement signals from resistor RB to control circuitry  54 . Control circuitry  54  may include voltage detector circuitry that uses lines  80 A,  80 B,  82 A, and  82 B to measure the currents flowing through each port. 
     The magnitude of the voltage across resistor RA is indicative of the current flowing through port A. The magnitude of the voltage across resistor RB corresponds to the amount of current flowing through port B. Because the magnitude of the current sensing resistors RA and RB may be determined in advance, measurement of the voltages across resistors RA and RB can be used to determine the amount of current flowing through each port from Ohm&#39;s law. This calculation may be made by control circuitry  54  or other circuitry in converter  12 . Control circuitry  54  may include one or more microprocessors, digital signal processors, microcontrollers, memory circuits, hardwired processing circuits, analog-to-digital and digital-to-analog converter circuits, communications circuits, etc. 
     Path  70  may be a ground power supply line that is coupled to ground outputs  75 A and  75 B of converter  12 . Switching circuitry such as switches SWA and SWB may be based on any suitable electrical components that can control the flow of DC power from the output of AC-DC power converter circuit  122  to the power supply input lines associated with attached loads (i.e., the inputs of an electronic device that are connected to the output port power supply lines in converter  12 ). For example, switches SWA and SWB may be implemented using one or more transistors such as one or more power field-effect transistors (power FETs). 
     Consider an example in which an electronic device is connected to port A. During normal operation, power converter  12  may use AC-DC power converter circuit  122  to supply a DC power supply voltage on lines  64  and  70 . Control circuitry  54  will close switch SWA, so line  64  will be shorted to output line  73 A in port A. This allows the DC power supply voltages at the output of AC-DC power converter circuit  122  to be provided to the electronic device via outputs  72 A and  74 A. The circuitry of port B may operate in the same way. 
     AC-DC power converter circuit  122  may contain control circuitry  38  for controlling internal switching circuits (e.g., transistor-based switches). The control circuitry may be responsive to feedback signals. For example, if port A is active, a feedback path that is formed using line  60 A, control circuitry  54 , and isolation stage  78  in path  76  may be used to supply AC-DC power converter circuit  122  with information on the current level of voltage Vbusa on output line  73 A. In response to this feedback information, the control circuitry in AC-DC power converter circuit  122  (i.e., control circuitry  38 ) can make real-time adjustments to the amount of DC voltage that is being supplied to the output of AC-DC power converter circuit. For example, if the DC voltage on output  64  has a nominal value Vsec of 5 volts and feedback indicates that the voltage has undesirably risen to 5.05 volts, the control circuitry in AC-DC power converter circuit  122  can make adjustments to lower the DC output voltage back to the nominal value (Vsec). If port B is active while port A is inactive, feedback of this type can be derived from feedback path  60 B. When both ports A and B are active at the same time, control circuitry  54  may monitor either line  60 A or  60 B, may monitor both lines to produce an average feedback signal, or may monitor output  64  using a separate feedback path (as examples). 
     Power converter  12  may contain an energy storage circuit  50 . Energy storage circuit  50  (sometimes also referred to as an energy storage element) may be based on any suitable circuitry for storing energy. As an example, energy storage circuit  50  may include one or more batteries, capacitors, etc. During operation of power converter  12  when AC-DC power converter circuit  122  is supplying power to output path  64 , a path such as path  66  may be used to route power to energy storage circuit  50 . The power that is routed to energy storage circuit  50  in this way may be used to replenish the battery, capacitor or other energy storage components in circuit  50 . In the example of  FIG. 1 , energy storage circuit  50  is coupled to AC-DC power converter circuit  122  by paths  64  and  66  (and ground  70 ). This is, however, merely illustrative. Any suitable routing paths may be used to supply replenishing power from AC-DC power converter circuit  122  to energy storage circuit  50  if desired. 
     Control circuitry  54  may monitor the status of power converter  12  using paths such as paths  80 A,  80 B,  82 A,  82 B,  66 ,  60 A, and  60 B. When appropriate, monitor  54  may provide control signals to AC-DC power converter circuit  122  using paths such as path  76 . 
     An isolation element such as isolation stage  78  may be interposed in path  76 . The control signals that are provided over path  76  may be used to direct control circuitry  38  to make adjustments to the operation of converter circuit  122  (e.g., to increase or decrease the output voltage on line  64  and/or to place AC-DC power converter circuit in an appropriate operating mode). In general, any suitable number of operating modes may be supported by AC-DC power converter circuit  122 . 
     For example, AC-DC power converter circuit  122  may be placed in one or more active modes and an optional standby mode. When in an active mode, AC-DC power converter  122  is on and supplies DC output power for replenishing energy storage circuit  50  and for supplying power to ports A and B. In standby mode, which is sometimes referred to as a sleep mode or low-power mode, AC-DC power converter circuit  122  is placed in a state in which little or no power is consumed by AC-DC power converter circuit  122  (i.e., AC-DC power converter circuit  122  is turned off by inhibiting modulation of its switched-mode power supply switches). If desired, AC-DC power converter circuit  122  may have multiple lower power states (e.g., a partly off state and a fully-off state). 
     When AC-DC power converter circuit  122  is in standby mode, AC-DC power converter circuit  122  is off and allows output  64  to float. In this situation, the power that has been stored in energy storage circuit  50  may be delivered to path  66  from within energy storage circuit  50 . For example, if energy storage circuit  50  contains a battery or a capacitor, the battery or capacitor may be used to supply a battery or capacitor voltage to path  66 . The voltage supplied by energy storage circuit  50  may be supplied at the same voltage level as the nominal output voltage level (Vsec) that AC-DC power converter circuit  122  supplies to path  64  when AC-DC power converter circuit  122  is in active mode. 
     Voltage regulators  52 A and  52 B may be current-limited circuits that produce output voltages that differ from the nominal output of AC-DC power converter circuit  122 . Voltage regulators  52 A and  52 B may, for example, be current-limited booster circuits that each produce an output of 5.1 volts (as compared to the 5 volt output of AC-DC power converter circuit  122 ). Periodically, control circuitry  54  can test whether a load is present on a given port by opening the switch for that port and monitoring its power supply voltage. 
     Consider, as an example, the monitoring of the status of port A. To check the status of port A, control circuitry  54  may open periodically open switch SWA using control line  62 A. This disconnects line  72 A and line  58 A from the output of converter circuit  122 . If an electronic device is present on port A, voltage regulator  52 A will be unable to supply all of the current needed by the device. This will cause the voltage Vbusa that is being monitored on line  60 A by control circuitry  54  to drop. In this situation, control circuitry  54  can conclude that a load is present on port A. Switch SWA can then be closed to allow normal operations to continue. If, however, no electronic device is present on port A, the opening of switch SWA will cause the voltage Vbusa on line  60 A to rise (e.g., to 5.1 volts). When this rise is detected, control circuitry  54  can conclude that no load is present on port A. In the same way, switch SWB may be controlled by control line  62 B while voltage Vbusb on line  72 B and line  58 B at the output of voltage regulator  52 B is being monitored using line  60 B. 
     This type of arrangement may be used by control circuitry  54  to determine which ports have active loads. If desired, current-sensing resistors such as resistors RA and RB may be used to make load current measurements. With one suitable arrangement, the voltages across resistors RA and RB are examined before the scheduled opening of switches SWA and SWB. Resistors RA and RB are generally not too large, so as not to impede efficient power delivery to attached devices. As a result, it can be difficult to use resistors RA and RB to measure extremely low load current values (i.e., load currents of the type that can be detected using switches SWA and SWB, voltage regulators  52 A and  52 B, and sensing lines  60 A and  60 B). Current-sensing resistors RA and RB can, however, be used to perform current pre-sensing operations. For example, control circuitry  54  can examine the voltage across resistors RA and RB before opening switches SWA and SWB. If a voltage is detected across a current-sensing resistor, control circuitry  54  can conclude that the port that is associated with the detected voltage has an active load. In this situation, there is no need to open the corresponding switch SWA or SWB and the switch opening operation can be inhibited to avoid possible glitches. 
     If desired, other circuit arrangements may be used to poll the ports in power converter  12  to determine whether an electronic device or other load is connected to that port. The illustrative load monitoring circuitry of  FIG. 2  is merely illustrative. 
     Once the number of active ports has been determined, control circuitry  54  can compute how much power is available for each port. For example, if the total capacity of AC-DC power converter circuit  122  is 10 W and if there is only a single electronic device connected to converter  12 , control circuitry  54  may conclude that the entire 10 W capacity of converter circuit  122  is available for delivery to the connected device. If, however, there are two electronic devices connected to converter  12 , control circuitry  54  may conclude that each port will be able to supply 5 W to its associated device. Computing the amount of power available for each of the active ports in this way allows the capacity of power converter circuit  122  to be intelligently shared between the devices that are connected to converter  12 . It is therefore not necessary to over-provision the circuitry in converter  12 . 
     Each device  10  that is connected to converter  12  may be informed of the amount of available power from converter  12 . In some situations, relatively more power may be available. For example, when a device is the only device connected to a given power converter, the power converter may be able to supply the device with 10 W of power. In other situations, less power may be available. For example, if there are two devices connected to the given power converter, the power converter may only be able to supply each device with 5 W of power. Devices  10  generally contain power management circuitry that can be configured to adjust their power draw levels. When a device is informed that there are 10 W of power available, the device may configure its power management circuitry so that the device consumes 10 W. When a device is informed that there are 5 W of power available, the device may configure its power management circuitry so that the device consumes a reduced power of 5 W. 
     By advertising the amount of power that is available for each port (i.e., the per-port available power), converter  12  can reconfigure devices  10  and can effectively share a limited amount of power conversion capacity among the devices. Any suitable technique may be used by converter  12  to convey information to devices  10  that informs devices  10  the per-port power availability. For example, converter  12  may include analog communications circuitry, digital communications circuitry, circuitry that generates codes based on fixed or time-varying resistance values, fixed or time-varying current values, or fixed or time varying voltage values. Coding schemes may present a particular circuit parameter (resistance, current, voltage, inductance, etc.) across a pair of terminals in a port or may present a series of multiple circuit parameters (e.g., across a single pair of terminals or across multiple sets of terminals). Combinations of these coding approaches may also be used. 
     With one illustrative configuration, which is sometimes described herein as an example, converter  12  may include circuitry that presents voltage-based codes to devices  10 . The voltage-based codes may instruct a device to configure its power management circuitry so that the device consumes a particular desired amount of power. The circuitry for producing the voltage-based codes may be implemented as part of control circuitry  54 . 
     Illustrative voltage-coding circuitry of the type that may be used in control circuitry  54  is shown in  FIG. 3 . As shown in  FIG. 3 , voltage-coding circuitry  100  (which may sometimes be referred to as communications circuitry, adjustable voltage divider circuitry, or coding circuitry), may be formed from parallel voltage dividers VD 1  and VD 2 . Voltage divider VD 1  includes series-connected resistors R 1  and R 2 . Voltage divider VD 2  may include resistor R 3  and an adjustable resistor that is formed from the parallel combination of resistor R 4  (in a first branch) and resistor RN and transistor  106  (in a second branch). 
     Line  102  may be connected to a source of positive voltage (e.g., line  64 ) and line  104  may be connected to ground (e.g., ground terminal  70 ). In a two-port power converter, there may be one of circuits  100  associated with port A and one of circuits  100  associated with port B. In port A, connector terminal Vbus of the first version of circuit  100  is connected to terminal P in connector  20 A. Connector terminal Vbus of the second version of circuit  100  is connected to terminal P in connector  20 B of port B. Similarly, terminals DP and DN in the first instance of circuit  100  are associated with DP and DN in connector  20 A and terminals DP and DN in the second instance of circuit  100  are associated with connector  20 B. In the first instance of circuit  100 , ground terminal GND is coupled to ground terminal G of connector  20 A (line  74 A). In the second instance of circuit  100 , ground terminal GND is coupled to ground terminal G of connector  20 B (line  74 B). 
     In a typical scenario, line  102  is provided with a positive supply voltage at 5 V and line  104  is provided with a ground supply voltage of 0 volts. Resistors R 1  and R 2  may be selected to produce a desired fixed voltage value V 1  on line DP. In voltage divider VD 2 , a variable voltage V 2  may be produced on node N 1 . Resistor R 3  may be coupled between line  102  and node N 1 . A variable resistor may be coupled between node N 1  and node N 2 . 
     In the  FIG. 3  example, the variable resistor between nodes N 1  and N 2  has been implemented using the parallel combination of two resistances. The first resistance is a fixed resistance associated with resistor R 4 . The second resistance varies depending on the state of control switch  106 . Control switch  106  may be implemented using a transistor or other suitable switching circuit. In the example of  FIG. 3 , switch  106  has been implemented using an n-channel metal-oxide-semiconductor (NMOS) transistor. Control circuitry  54  ( FIG. 2 ) may generate time-varying or static control signals CNTL on line  108  at the gate of transistor  106 . The value of the control signal CNTL on line  108  determines the state of transistor  106 . If CNTL is high, transistor  106  will be on and drain terminal D will be shorted to source terminal S. If CNTL is low, transistor  106  will be off and will form an open circuit (infinite resistance) between drain terminal D and source S. 
     The state of transistor  106  therefore controls the resistance between nodes N 1  and N 2 . When transistor  106  is off, there is an open circuit between drain D and source S, so the resistance between nodes N 1  and N 2  is equal to the resistance of resistor R 4 . When transistor  106  is on, both of the parallel resistor paths between node N 1  and node N 2  are active. In this situation, the resistance between node N 1  and N 2  is given by the parallel combination of R 4  and RN (i.e., R 4 *RN/(R 4 +RN)). When transistor  106  is off, the voltage V 2  has a first (higher) value associated with the relative strengths of resistors R 3  and R 4 . When transistor  106  is on, the voltage V 2  has a second (lower) value associated with the relative strengths of resistor R 3  and the combination of resistor R 4  in parallel with resistor RN. 
     With this type of circuit, control circuitry  54  can adjust the values of V 1  and V 2 . The values of V 1  and V 2  and/or their relative values can be used as codes. An electronic device that is connected to converter  12  can monitor the values of V 1  and V 2  over the DP and DN lines in a USB cable and can take appropriate action based on the V 1  and V 2  values. One combination of V 1  and V 2  may, for example, correspond to a situation in which the device should be configured to draw 10 W of power (i.e., when the per-port available DC power is 10 W) and another combination of V 1  and V 2  may, for example, correspond to a situation in which the device should be configured to draw 5 W of power (i.e., when the per-port available DC power is 5 W). 
     Another circuit that may be used in control circuitry  54  to produce desired values of V 1  and V 2  on connector terminals DP and DN is shown in  FIG. 4 . In circuitry  110  of  FIG. 4 , line  112  may be connected to a source of positive voltage (e.g., line  64  in  FIG. 2 ) and line  114  may be connected to ground (e.g., ground terminal  70  in  FIG. 2 ). As with circuit  100  of  FIG. 3 , there may be a respective one of circuits  110  associated with each port in power converter  12 . For example, there may be one of circuits  110  associated with port A and one of circuits  110  associated with port B in a two-port configuration. 
     The values of V 1  and V 2  that are produced by circuitry  110  may be controlled by control circuitry  54  by applying appropriate digital control signals (logic ones and zeros) to the gates G of the control transistors of circuitry  110 . As shown in  FIG. 4 , circuitry  110  may have a first adjustable voltage divider circuit  110 A that produces voltage V 1  and a second adjustable voltage divider circuit  110 B that produces voltage V 2 . 
     Each adjustable voltage divider has a number of branches. Each branch has an upper segment and a lower segment. The upper segments include p-channel metal-oxide-semiconductor (PMOS) transistors and the lower segments include n-channel metal-oxide-semiconductor (NMOS) transistors. Each branch also includes a pair of transistors, one of which is in the upper segment of that branch and one of which is in the lower segment of that branch. For example, the first branch of circuit  110 A (branch B 1 A) has an upper segment that contains PMOS transistor TP 1  and resistor RP 1  and has a lower segment that contains NMOS transistor TN 1  and resistor RN 1 . The upper segments of the branches of voltage divider  110 A may each have a different respective resistance (RP 1 , . . . RPN) and the lower segments of the branches of voltage divider  110 A may likewise each have a different respective resistance (RN 1 , . . . RNN). By turning on a given one of the PMOS transistors and a given one of the NMOS transistors in circuit  110 A while all other transistors in circuit  110 A are turned off, a desired voltage divider may be formed by circuit  110 A and therefore a desired value of V 1  on terminal DP may be produced. If desired, multiple transistors (e.g., multiple NMOS transistors and/or multiple PMOS transistors) may be turned on at the same time in circuit  110 A, thereby creating parallel resistance circuits of desired resistance values. Adjustable voltage divider  110 B may be operated in the same way as adjustable voltage divider  110 A to produce a desired value of V 2  on terminal DN. 
     The adjustable voltage divider circuitry of  FIGS. 3 and 4  serves as a type of digital-to-analog (D-to-A) converter circuit for producing desired V 1  and V 2  values. An illustrative circuit that is based on D-to-A circuits  124  and  126  (e.g., integrated circuit D-to-A circuits) is shown in  FIG. 5 . In this type of arrangement, control circuitry  123  may be implemented using the resources of control circuitry  54 . D-to-A converters  124  and  126  may also be implemented within circuitry  54 . Line  118  may receive a positive power supply voltage from line  64  of  FIG. 2  and ground line  116  may receive a 0 volt ground signal from line  70  of  FIG. 2 . Terminals VBUS, DP, DN, and GND may be associated with a connector in a port in power converter  12 . Multiple circuits  116  may be used in converters that include multiple ports. 
     During load sensing operations, control circuitry  54  may determine the per-port power that is available to the devices that have been connected to the ports of converter  12 . The available per-port power level may then be communicated to the connected devices. For example, control circuitry  123  may provide digital signals to D-to-A converter  124  that direct D-to-A converter  124  to produce a desired value of V 1  on terminal DP. Control circuitry  123  may also provide digital signals to D-to-A converter  126  that direct D-to-A converter  126  to produce a desired value of V 2  on terminal DN. Each device  10  may include voltage detector circuitry and control logic that can monitor lines DP and DN and that can recognize the coded per-port power information being transmitted by control circuitry  123 . Each device  10  may then adjusts its power draw to accommodate the per-port available power from converter  12 . 
     If desired, more complex communications circuits can be used by control circuitry  123 . For example, D-to-A converters  124  and  126  can be omitted so that control circuitry  123  can be connected directly to terminals DP and DN. An asynchronous or synchronous digital communications link may then be established over paths DP and DN between converter  12  and each attached device. This communications link may be unidirectional or bidirectional and may involve the transmission of signals using any suitable coding scheme. 
     Illustrative steps involved in using power converter  12  are shown in  FIG. 6 . Initially, as shown by line  127 , a user may decide to connect one or more devices  10  or other loads to respective ports in power converter  12 . 
     Power converter  12  may periodically monitor the status of its ports. For example, control circuitry  54  may periodically make load current measurements as described in connection with  FIG. 2  (step  128 ). From these measurements, control circuitry  54  can determine which of the ports in power converter  12  are connected to loads. If, for example, there are three ports in converter  12  and a user has plugged only a single device into one of these three ports, control circuitry  54  can determine that only one device is present. If, as another example, three separate electronic devices are plugged into the three ports, control circuitry  54  can determine from load measurements that all three ports are occupied. 
     Following a determination of the number of ports to which electronic devices have been attached at step  128 , power converter  12  can use control circuitry  54  to compute the maximum per-port power available (step  130 ). For example, if power converter  12  has a converter circuit such as circuit  122  with a 10 W capacity and there are three occupied ports, control circuitry  54  will determine that the per-port available power level is 10 W divided by three (i.e., 3.33 W). If fewer devices are connected, the per-port available power level will be larger. 
     At step  132 , control circuitry  54  may advertise the amount of power that is available on each port. Any suitable communications scheme may be used. For example, control circuitry  54  may use a voltage coding scheme of the type described in connection with  FIGS. 3, 4, and 5  to produce a set of voltages V 1  and V 2  that indicate the value of the per-port available power. Schemes based on more complex digital communications protocols (e.g., bidirectional protocols, etc.) may also be used. 
     Control circuitry  54  may limit the current that is drawn by the connected devices. For example, control circuitry  54  can monitor the amount of current (and therefore the amount of power) that is delivered through each port by monitoring the voltage drop across current sensing resistors such as resistors RA and RB of  FIG. 2 . If the power flowing to a given port starts to exceed the maximum allowed per-port limit, the power flowing to that port can be regulated. For example, control circuitry  54  can adjust a control switch that is associated with the port to reduce or interrupt power flow (e.g., by adjusting switch SWA to prevent excessive power from flowing to the device that is connected to port A, by adjusting switch SWB to regulate power flow to port B, etc.). Switches such as switches SWA and SWB may be adjusted using analog or digital control signals, fixed or time-varying control signals, or any other suitable control signals to impose desired power limits. Power regulation can also be performed using circuit  122 . Fuses, circuit breakers, or other power-limiting devices or circuits can also be used to ensure that power limits are not exceeded. 
     At step  136 , the electronic devices  10  that are attached to power converter  12  can receive and decode the encoded per-port available power information that was transmitted from control circuitry  54  during the operations of step  132 . If, for example, there is only a single device connected to converter  12 , the device might receive and process information that 10 W of power is available from converter  12 . That device may then use its power management circuitry to adjust the amount of power that is being drawn from converter  12  to a matching value (i.e., 10 W). If, however, there were two devices connected to converter  12 , the devices might each receive and process information indicating that 5 W of power is available per port. Each of the two devices may then use its power management circuitry to adjust its power draw to match the available 5 W of power. 
     As illustrated by line  138 , the steps of  FIG. 6  involved in using power converter  12  may be repeated. For example, the steps of  FIG. 6  may be repeated after a user disconnects one or more devices  10  or other loads from their respective ports in power converter  12  (e.g., whenever a user disconnects one or more of the devices or other loads connected to power converter  12 ). This type of arrangement may help to ensure that devices  10  which are still connected to power converter  12  can receive the maximum amount of power available from power converter  12  (e.g., that power converter  12  does not reserve power for ports which are no longer connected to a device or other load). With one suitable arrangement, the steps of  FIG. 6  may be continuously repeated or repeated at certain intervals (e.g., every 5 seconds, every 10 seconds, every 30 seconds, every minute, every five minutes, or at other suitable intervals). In general, the steps of  FIG. 6  may be repeated at any periodic or random interval. 
     The foregoing is merely illustrative of the principles of this invention and various modifications can be made by those skilled in the art without departing from the scope and spirit of the invention.

Metadata:
Filing Date: 20150707
Publication Date: 20180109
Grant Date: 20180109
Priority Date: 20090924
Inventors: TERLIZZI JEFFREY J.
SIMS NICHOLAS A.
Assignee: APPLE INC
CPC Classifications: [{"code": "H02J7/0036", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/00", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J1/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J9/005", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J1/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0036", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J9/005", "inventive": false, "first": false, "tree": "[]"}, {"code": "Y10T307/414", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/0027", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J9/005", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J1/08", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J7/0036", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/045", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J1/14", "inventive": true, "first": false, "tree": "[]"}, {"code": "H02J2007/0062", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J1/00", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J7/0013", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J2310/22", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J1/08", "inventive": true, "first": true, "tree": "[]"}, {"code": "H02J2310/22", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/0013", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J7/04", "inventive": false, "first": false, "tree": "[]"}, {"code": "H02J1/08", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 43756000