Patent Publication Number: US-2013249472-A1

Title: Ac-dc converter and charge and discharge system thereof

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention is related to an AC-DC converter and to a charging and discharging system thereof; more particularly, it is related to an AC-DC converter and a charging and discharging system thereof that can amplify the potential of a power signal. 
     2. Description of the Related Art 
     In today&#39;s technology, electrical power is a critical element that cannot be ignored. Various technologies for converting AC (alternating current) signals and DC (direct current) signals have been developed. Bidirectional AC-DC conversion circuits are used in various charging and discharging systems. However, in the conventional art, normal bidirectional AC-DC conversion circuits are composed of multiple conversion circuits connected electrically for converting AC power signals and DC power signals into each other. These conversion circuits are constructed of multiple switch units that are electrically connected as a bridge circuit, and they do not adjust the potential of power signals. For example, when a bidirectional conversion circuit converts an AC power signal with a low potential into a DC power signal, it can only be converted into a DC power signal with a low potential. If it is used for charging a battery unit, a longer charging time is therefore necessary. If a DC power signal with a larger potential is needed to be output, a large transformer is used for conversion, but the much greater weight of a large transformer makes using such a device inconvenient. For uninterruptible power supply systems or electrical cars that a need larger power storage capacity, the conversion efficiency of conventional AC-DC converters is inefficient. 
     Therefore, there is a need for a new AC-DC converter and a charging and discharging system with an AC-DC converter that can solve the problems of the prior art. 
     SUMMARY OF THE INVENTION 
     A major objective of the present invention is to provide an AC-DC converter that is able to amplify a potential of a power signal. 
     Another major objective of the present invention is to provide a charging and discharging system with the abovementioned AC-DC converter. 
     To achieve the above objectives, the AC-DC converter of the present invention includes a first signal terminal, a power storage unit, a first conversion circuit, a control module, a second conversion circuit, and a second signal terminal. The first signal terminal is used for inputting a first power signal. The power storage unit is electrically connected to the first signal terminal for increasing a potential of the first power signal and transforming the first power signal into a first conversion signal. The first conversion circuit is electrically connected to the power storage unit. The control module is electrically connected to the first conversion circuit. The control module controls the first conversion circuit to use the power storage unit for amplifying the first power signal into the first conversion signal and then transferring it into a second conversion signal. The second conversion circuit is electrically connected to the first conversion circuit via a transformer for converting the second conversion signal into a DC power signal. The second signal terminal is electrically connected to the second conversion circuit for outputting a DC power signal. 
     The charging and discharging system includes an AC-DC converter and a battery apparatus. The AC-DC converter includes a first signal terminal, a power storage unit, a first conversion circuit, a control module, a second conversion circuit, and a second signal terminal. The first signal terminal is used for inputting a first power signal. The power storage unit is electrically connected to the first conversion circuit for amplifying the potential of the first power signal and converting it into a first conversion signal. The first conversion circuit is electrically connected to the power storage unit. The control module is electrically connected to the first conversion circuit. The control module controls the first conversion circuit to use the power storage unit for amplifying the first power signal into the first conversion signal and then transferring it into a second conversion signal. The second conversion circuit is electrically connected to the first conversion circuit for converting the second conversion signal into a DC power signal. The second signal terminal is electrically connected to the second conversion circuit for outputting a DC power signal. The battery apparatus is electrically connected to the second signal terminal for receiving the DC power signal. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a structure diagram illustrating a charging and discharging system with an AC-DC converter of the present invention. 
         FIG. 1B  is a structure diagram illustrating the AC-DC converter with an AC signal conversion circuit of the present invention. 
         FIG. 2A  is a circuit structure diagram of an AC signal conversion circuit of the AC-DC converter of the first embodiment of the present invention. 
         FIG. 2B  is a circuit structure diagram of an AC signal conversion circuit of the AC-DC converter of the second embodiment of the present invention. 
         FIG. 3A  is a circuit structure diagram of a first conversion circuit of the AC-DC converter of the third embodiment of the present invention. 
         FIG. 3B  is a circuit structure diagram of a first conversion circuit of the AC-DC converter of the fourth embodiment of the present invention. 
         FIG. 3C  is a circuit structure diagram of a first conversion circuit of the AC-DC converter of the fifth embodiment of the present invention. 
         FIG. 3D  is a circuit structure diagram of a first conversion circuit of the AC-DC converter of the sixth embodiment of the present invention. 
         FIG. 4A  is a circuit structure diagram of a second conversion circuit of the AC-DC converter of the seventh embodiment of the present invention. 
         FIG. 4B  is a circuit structure diagram of a second conversion circuit of the AC-DC converter of the eighth embodiment of the present invention. 
         FIG. 4C  is a circuit structure diagram of a second conversion circuit of the AC-DC converter of the ninth embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     These and other objects and advantages of the present invention will become apparent from the following description of the accompanying drawings, which disclose several embodiments of the present invention. It is to be understood that the drawings are to be used for purposes of illustration only, and not as a definition of the invention. 
     Please refer to  FIG. 1A , which is a structure diagram illustrating a charging and discharging system with an AC-DC converter of the present invention. 
     The charging and discharging system  1  of the present invention can be used in systems with two directional power signal transmission, such as an electrical car or an uninterruptible power supply system, but the present invention is not limited to only such applications. The charging and discharging system  1  comprises a battery apparatus  2  and an AC-DC converter  10   a . The AC-DC converter  10   a  is a two directional AC-DC power signal conversion module in which the second signal terminal  22  is electrically connected to an external electronic device, such as the battery apparatus  2 , for outputting a DC power signal to the battery apparatus  2  or receiving a DC power signal from the battery apparatus  2 . 
     The AC-DC converter  10   a  comprises a first signal terminal  21 , a second signal terminal  22 , a first conversion circuit  32 , a second conversion circuit  33 , a power storage unit  41 , a control module  42 , a transformer T, and other electrical units. The first signal terminal  21  of the AC-DC converter  10   a  is electrically connected to the power supply system  3  for receiving a first power signal. The power supply system  3  is able to be a system for supplying a DC power, but the present invention is not limited to only the examples mentioned above. The power supply system  3  may also be a system for supplying a DC power. As shown in the  FIG. 1A , it is only explained here that the power supply system  3  is a related system for supplying the DC power and that the first power signal is the DC signal in the following disclosure. 
     The first conversion circuit  32  is electrically connected to the first signal terminal  21 . Moreover, the power storage unit  41  may also be connected between the first conversion circuit  32  and first signal terminal  21 . The power storage unit  41  may be an inductor for amplifying a potential of the first power signal to convert it into a first conversion signal, wherein the first conversion circuit  32  and the power storage unit  41  may both have a power factor correction (PFC) function. Then the first conversion circuit  32  is used for receiving the first conversion signal and transferring the first conversion signal, which has an amplified potential, into a second conversion signal. Then the second conversion signal is transmitted to the second conversion circuit  33  via the transformer T. 
     The first conversion circuit  32  is also used for electrically connecting to the control module  42  so that the generation of the second conversion signal is controlled by the control module  42 . The control module  42  may be implemented with circuit or chip hardware architecture, hardware combined with firmware structure, or other structures, but the present invention is not limited to such designs. The control module  42  is used for controlling the first conversion circuit  32  to allow the power storage unit  41  first to amplify the potential of the first conversion signal and then to control the first conversion circuit  32  to transfer the amplified first conversion signal into the second conversion signal. How the control module  42  controls the first conversion circuit  32  will be explained in greater detail later and thus is not described here. As such, the AC-DC converter  10   a  is capable of amplifying the potential of the input signal from the first signal terminal  21  by switching of the first conversion circuit  32  and storing a greater amount of energy for charging the battery apparatus  2 . 
     The second conversion circuit  33  is electrically connected to the first conversion circuit  32  via the transformer T for receiving the second conversion signal and then converting it into the DC power signal. Finally, the DC power signal flows through the second signal terminal  22  to the battery apparatus  2  for charging the battery apparatus  2 . Please note that the second conversion circuit  33  may also be electrically connected to the control module  42  and be controlled by the control module  42  for performing signal conversion, but the present invention is not limited to such a design. In addition, passive elements like a capacitor C or an inductor L (as illustrated in  FIG. 2A ) may be disposed inside the AC-DC converter for stabilizing potential. Since how the capacitor C operates and functions is well known to person of ordinary skill in the art, it is not further explained here. 
     Next please refer to  FIG. 1B , which is a structure diagram illustrating the AC-DC converter with an AC signal conversion circuit of the present invention 
     If the power supply system  3  is a system for supplying mains electricity or an electrical generator for supplying the AC power signal, the power supply system  3  is able to supply the first power signal in the AC signal. In this embodiment, the AC-DC converter  10   b  further comprises an AC signal conversion circuit  31 . The AC signal conversion circuit  31  is electrically connected between the first signal terminal  21  and the power storage unit  41  and used for receiving the AC signal of the first power signal to be converted into a DC signal and to be transmitted to the power storage unit  41 . Similarly, the AC signal conversion circuit  31  can be controlled by the control module  42  for performing signal conversion. Because the usage of the other elements in the AC-DC converter  10   b , such as the first conversion circuit  32  or the second conversion circuit  33 , are the same as described in  FIG. 1A , no further description is provided here. 
     The AC-DC converter  10   b  can also transfer a DC power signal into a first power signal in the opposite direction. That is, after the battery apparatus  2  inputs a DC power signal, the control module  42  controls the second conversion circuit  33 , the first conversion circuit  32 , and the AC signal conversion circuit  31  to perform conversion, and then the first power signal obtained from conversion is transmitted to a load (not shown in the drawing) via the first signal terminal  21 . Next, please refer to  FIG. 2A , which is a circuit diagram of the AC signal conversion circuit of the AC-DC converter of the first embodiment of the present invention. Please note that, because the flow for the circuit structure of the AC-DC converter  10   a  for transferring a DC signal to an AC signal is similar to that for converting an AC signal to a DC signal, and persons of ordinary skill in the art understand the conversion structure and processes for both directions of conversion, the following disclosure explains only how an AC signal is converted to a DC signal. 
     In the first embodiment of the present invention, the AC signal conversion circuit  31   a  comprises a first switch unit  311 , a second switch unit  312 , a third switch unit  313 , and a fourth switch unit  314 , and they all may be implemented by using a transistor with a diode, wherein the transistor may be a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT). However, the present invention is not limited to such arrangement. For example, they can be implemented with diode devices. As shown in  FIG. 2A , the first switch unit  311 , the second switch unit  312 , the third switch unit  313 , and the fourth switch unit  314  form a bridge circuit, but the AC signal conversion circuit  31   a  may also be a half bridge circuit. Therefore, when a first power signal generated by the power supply system  3   a  is input, it flows through each switch unit of the AC signal conversion circuit  31   a  respectively for converting the first power signal to be rectified into a first conversion signal. On the other hand, the AC signal conversion circuit  31   a  may also be controlled by the control module  42  to perform signal conversion. The control module  42  first controls the first switch unit  311  and the third switch unit  313  to be turned on, and the second switch unit  312  and the fourth switch unit  314  to be turned off, and then controls the second switch unit  312  and the fourth switch unit  314  to be turned on and the third switch unit  313  and the first switch unit  311  to be turned off. With such a process, the first conversion signal is generated via switching. In this embodiment, the AC signal conversion circuit  31   a  may be controlled by the control module  42  to achieve better conversion efficiency, but the present invention is not limited to a design that requires a control module  42 . 
     Please also note that the charging and discharging system  1  may further include a switch module  50  when it is used in different applications. For example, when the charging and discharging system  1  is an uninterruptible power supply system, the first signal terminal  21  can be electrically connected to the switch module  50  so as to determine whether to receive a first power signal from the power supply system  3   a  or to output a first power signal to other loads with the switch module  50 . The switch module  50  can be a single-way switch connected to one output terminal of the power supply system  3   a  or can be a double-way switch connected to two terminals of the power supply system  3   a  at the same time. However, the present invention is not limited to such designs. 
     The AC signal conversion circuit  31   a , as shown in  FIG. 2A , is used for converting a single phase AC signal. But the present invention is not limited to such a design. Next, please refer to  FIG. 2B , which is a circuit structure diagram of an AC signal conversion circuit of the AC-DC converter of the second embodiment of the present invention. 
     In the second embodiment of the present invention, the power supply system  3   b  is used for supplying a three-phase AC signal. The AC signal conversion circuit  31   b  comprises a first switch unit  311 , a second switch unit  312 , a third switch unit  313 , a fourth switch unit  314 , a fifth switch unit  315 , and a sixth switch unit  316 , and they all may be implemented by using a transistor with a diode, wherein the transistor may be a MOSFET or an IGBT. As a result, when the power supply system  3   b  supplies the three phase AC signal, the AC signal conversion circuit  31   b  controls the first switch unit  311 , the second switch unit  312 , the third switch unit  313 , the fourth switch unit  314 , the fifth switch unit  315 , and the sixth switch unit  316  to turned on or turned off for generating the DC signal. 
     Next, please refer to  FIG. 3A , which illustrates a circuit structure of the first conversion circuit of the AC-DC converter of the third embodiment of the present invention. 
     In the third embodiment of the present invention, the first conversion circuit  32   a  comprises a synchronous rectifier and an auxiliary switch unit  325 . The synchronous rectifier comprises a first switch unit  321  and a second switch unit  322  with different terminals electrically connected to the auxiliary switch unit  325 . The auxiliary switch  325 , the first switch unit  321 , and the second switch unit  322  are respectively implemented by using a transistor with a diode, such as a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT) with a diode, and they are all electrically connected to the control module  42 . When the first conversion signal is received, the control module  42  first controls the auxiliary switch unit  325  to be turned on. With such a status of the auxiliary switch unit  325 , the first conversion signal flows through the capacitor C, the power storage unit  41 , the auxiliary switch  325 , and then back to the capacitor C so that the first conversion signal is amplified and more energy is stored in the power storage unit  41 . Next, the control module  42  controls the auxiliary switch unit  325  to be turned off, and the first switch unit  321  to be turned on, so as to output the second conversion signal with a positive waveform. Then the control module  42  further executes a similar control flow for controlling the switch unit  325  to be turned on first, and then controls the auxiliary switch unit  325  to be turned off and the second switch unit  322  to be turned on so as to generate the second conversion signal with an opposite waveform. 
     It can be understood from the above disclosure that the first conversion circuit  32   a  may use the power storage unit  41  to amplify the first conversion signal and then may output the second conversion signal to get a signal of greater energy. 
     Next please refer to  FIG. 3B , which illustrates a circuit structure diagram of a first conversion circuit of an AC-DC converter of a fourth embodiment of the present invention. 
     In the fourth embodiment of the present invention, the first conversion circuit  32   b  is similar to the first conversion circuit  32   a  of the third embodiment, for both conversion circuits have a synchronous rectifier and the auxiliary switch unit  325 . The only differences are the direction of the electrical connection between the first switch unit  321  and the auxiliary switch unit  325  and the direction of the electrical connection between the second switch unit  322  and the auxiliary switch unit  325 . The first conversion circuit  32   b  operates under a similar principle to the first conversion circuit  32   a  of the third embodiment. Therefore, in the fourth embodiment, the control module  42  first controls the auxiliary switch unit  325  to be turned on, and then controls the auxiliary switch unit  325  to be turned off and the second switch unit  322  to be turned on for outputting a second conversion signal with a positive waveform. Then the control module  42  controls the auxiliary switch unit  325  to be turned on, and then controls the auxiliary switch unit  325  to be turned off and the first switch unit  321  to be turned on for outputting a second conversion signal with an opposite waveform. With such a process, the first conversion circuit  32   b  is able to output the second conversion signal. 
     Next, please refer to  FIG. 3C , which is a circuit structure diagram of the first conversion circuit of the AC-DC converter of a fifth embodiment of the present invention. 
     In the fifth embodiment of the present invention, the first conversion circuit  32   c  is a synchronous current double rectifier. The first conversion circuit  32   c  has a first switch unit  321  and a second switch unit  322 , which respectively are similarly made of a metal oxide semiconductor field-effect transistor with a diode, such as a MOSFET or an IGBT with a diode. They are both electrically connected to the control module  42 . In the fifth embodiment, the power storage unit (not shown) includes a first inductor L 1  and a second inductor L 2 . The first inductor L 1  is electrically connected to a first switch unit  321  and the second inductor L 2  is electrically connected to a second switch unit  322 . 
     When the first conversion signal is received, the control module  42  first controls the first switch unit  321  to be turned on. As such, the first conversion signal flows through the capacitor C, the first inductor L 1 , and the first switch unit  321 , and then flows back to the capacitor C. Therefore, the first conversion signal is amplified and stored as energy by the power storage unit (not shown). Next, the control module  42  controls the first switch unit  321  to be turned off and the second switch unit  322  to be turned on for outputting a second conversion signal with a positive waveform. Next, the control module  42  executes a similar control flow for controlling the second switch unit  322  to be turned on first so that the first conversion signal flows through the capacitor C, the second inductor L 2 , and the second switch unit  322 , and then flows back to the capacitor C. Finally, the second switch unit  322  is controlled to be turned off and the first switch unit  321  is controlled to be turned on so as to output a second conversion signal with an opposite waveform. As a result, the first conversion circuit  32   c  is capable of storing the energy of the first conversion signal by using the first inductor L 1  and the second inductor L 2  respectively for outputting the second conversion signal with greater energy. 
     Next, please refer to  FIG. 3D , which illustrates a circuit structure diagram of a first conversion circuit of an AC-DC converter of a sixth embodiment of the present invention. 
     In the sixth embodiment of the present invention, the first conversion circuit  32   d  is a full wave bridge rectifier that has a first switch unit  321 , a second switch unit  322 , a third switch unit  323 , and a fourth switch unit  324  electrically connected to form a bridge circuit. These switch units are similarly composed of a metal oxide semiconductor field-effect transistor with a diode, such as a MOSFET or an IBGT with a diode. They are all electrically connected to the control module  42 . 
     When the first conversion signal is received, the control module  42  first controls the first switch unit  321  and the second switch unit  322  to be turned on. As such, the first conversion signal flows through the capacitor C, the power storage unit  41 , the first switch unit  321 , and the second switch unit  322 , and then flows back to the capacitor C. Therefore, the first conversion signal is amplified by the power storage unit  41 . Next, the control module  42  controls the first switch unit  321  and the third switch unit  323  to be turned on and the second switch unit to be turned off for generating a second conversion signal with a positive waveform. Next, the control module  42  executes a similar control flow by first controlling the fourth switch unit  324  and the third switch unit  323  to be turned on so that the first conversion signal flows through the capacitor C, the power storage unit  41 , the fourth switch unit  324 , and the third switch unit  323 , and then flows back to the capacitor C. Finally, the third switch unit  323  is turned off, and the second switch unit  322  and the fourth switch unit  324  are turned on for outputting a second conversion signal with an opposite waveform. With such a process, the first conversion circuit  32   d  can use the power storage unit  41  to store energy of the first conversion signal and then output the second conversion signal for obtaining a signal of greater energy. 
     The charging and discharging system  1  may be configured to set different circuits of the first conversion circuit  32  under different situations. For example, when the charging and discharging system  1  is used in a low power environment, the first conversion circuit  32   a  or the first conversion circuit  32   b  is used. When the charging and discharging system  1  is used in a medium power environment, the first conversion circuit  32   c  is used. When the charging and discharging system  1  is used in a high power environment, the first conversion circuit  32   d  is used. 
     The second conversion circuit  33  of the present invention may also be implemented in different ways. Next, please refer to  FIG. 4A , which is a circuit structure diagram of the second conversion circuit of the seventh embodiment of the present invention. 
     In the seventh embodiment of the present invention, the second conversion circuit  33   a  has a first switch unit  331  and a second switch unit  332 . The first switch unit  331  and the second switch unit  332  are structured as a push-pull circuit and electrically connected to the battery apparatus  2  and the transformer T. The first switch unit  331  and the second switch unit  332  are also constructed of a metal oxide semiconductor filed-effect transistor with a diode, such as a MOSFET or an IBGT with a diode, and they both all electrically connected to the control module  42 . However, such arrangement should not be regarded as a limitation of the present invention. When the second conversion signal is input to the second conversion circuit  33   a , the control module  42  controls the first switch unit  331  and the second switch unit  332  to be turned on or turned off so as to convert the second conversion signal into a DC power signal for charging the battery apparatus  2 . The second conversion circuit  33   a  may be controlled by the control module  42  for achieving better conversion efficiency. However, when the second conversion signal is input, the second conversion circuit  33   a  may also perform conversion with its own circuit, and the present invention is not limited to the use of a control module  42  to control the second conversion circuit  33   a.    
     Next, please refer to  FIG. 4B , which is a circuit structure diagram of the second conversion circuit of the eighth embodiment of the present invention. 
     In the eighth embodiment of the present invention, the second conversion circuit  33   b  has a first switch unit  331  and a second switch unit  332  to form a half bridge circuit. The first switch unit  331  and the second switch unit  332  may be structured of a metal oxide semiconductor filed-effect transistor with a diode, such as a MOSFET or an IGBT with a diode, and they are both electrically connected to the control module  42 . However, the present invention is not limited to such a design. Similar to the second conversion circuit  33   a , when the second conversion signal is input to the second conversion circuit  33   b , the control module  42  controls the first switch unit  331  and the second switch unit  332  to be turned on or to be turned off in order to convert the second conversion signal into a DC power signal for charging the battery apparatus  2 . Similarly, the second conversion circuit  33   b  may also convert the second conversion signal into a DC power signal with its own circuit structure. Although the second conversion circuit  33   b  may be controlled by the control module  42  to achieve better conversion efficiency, the present invention is not limited to the second conversion circuit  33   b  being controlled by the control module  42 . 
     Last, please refer to  FIG. 4C , which is a circuit structure diagram of the second conversion circuit of the AC-DC converter of the ninth embodiment of the present invention. 
     In the ninth embodiment of the present invention, the second conversion circuit  33   c  has a first switch unit  331 , a second switch unit  332 , a third switch unit  333 , and a fourth switch unit  334  electrically connected to form a full bridge circuit. These switch units are also respectively made of a metal oxide semiconductor filed-effect transistor with a diode, such as a MOSFET or an IGBT with a diode, and they are all electrically connected to the control module  42 . Therefore, the control module  42  may first control the first switch unit  331  and the third switch unit  333  to be turned on, and the second switch unit  332  and the fourth switch unit  334  to be turned off. Then the fourth switch unit  334  and the second switch unit  332  are turned on and the third switch unit  333  and the first switch unit  331  are turned off for converting the second conversion signal into a DC power signal for charging the battery apparatus  2 . With such a process, better conversion efficiency is obtained. Similarly, the second conversion circuit  33   c  may use its own circuit structure for converting the second conversion signal into a DC power signal, and the present invention is not limited to the use of the control module  42  for controlling the second conversion circuit  33   c.    
     Therefore, an AC-DC converter  10   a  or  10   b  may be implemented by various combinations of the abovementioned embodiments. For example, the AC signal conversion circuit  31  is capable of connecting to any one of the first conversion circuits  32   a  to  32   d  and then connecting to any one of the second conversion circuits  33   a  to  33   c  for converting the input first power signal into a DC power signal. Moreover, the AC-DC converter  10   a  or  10   b  can increase the energy of the signal in order to reduce the charging time of the battery apparatus  2 . 
     It is noted that the above-mentioned embodiments are only for illustration. It is intended that the present invention cover modifications and variations of the present invention provided they fall within the scope of the following claims and their equivalents. Therefore, it will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention.