Abstract:
A DC converter includes a non-isolated conversion module and an isolated conversion module. The non-isolated conversion module is implemented based on a redundant structure and has a first power conversion loop, a second power conversion loop, and an energy storage element. The first and second power conversion loops are connected and share the energy storage element. The energy storage element is further connected to an input terminal of the isolated conversion module. The first and second conversion loops of the non-isolated conversion module convert DC power outputted from two battery sets and output the converted power to the isolated conversion module. The isolated conversion module further supplies DC power to a load. Accordingly, power supply systems using the foregoing DC converter can reduce the number of transformer therein and thus size reduction of the power supply system can be achieved.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a power supply system and a converter thereof, and more particularly to a direct-current (DC) converter composed of a pre-stage non-isolated conversion module and a post-stage isolated conversion module dedicated to resolve the issue of conventional DC converters being bulky due to use of transformer in each isolated converter in the conventional DC converters. 
         [0003]    2. Description of the Related Art 
         [0004]    With reference to  FIG. 7 , a conventional power supply system has an AC (Alternating Current) to DC converter  80 , a DC converter  70  and two battery sets  73 ,  74 . The AC to DC converter  80  has a set of AC input terminals and a set of DC output terminals. The set of AC input terminals is connected to a mains power. The set of DC output terminals is connected to a set of DC input terminals of the DC converter  70 . The two battery sets  73 ,  74  are bridged over the set of DC input terminals to serve as backup power supplies. When the mains power is irregular, the DC converter  70  converts power of the battery sets  73 ,  74  into power with a desired voltage to continue supplying the converted power to a load. 
         [0005]    When the foregoing power system is applied to a communication system, the DC converter  70  should be able to output power with negative voltage. With reference to  FIG. 8 , a DC converter  70  having negative output voltage has a first power conversion module  71 , a second power conversion module  72 , and two battery sets  73 ,  74 . Each of the first power conversion module  71  and the second power conversion module  72  has a positive input terminal Vcom and a negative input terminal RTN 1 , RTN 2 . The positive input terminals Vcom of the first power conversion module  71  and the second power conversion module  72  are connected to a common positive terminal of the battery sets  73 ,  74 . The negative input terminals RTN 1 , RTN 2  are respectively connected to the negative terminals of the battery sets  73 ,  74 . The first power conversion module  71  and the second power conversion module  72  respectively have two sets of output terminals, which are connected in parallel. 
         [0006]    The foregoing DC converter employs a redundant structure. When one of the battery sets  73 ,  74  or one of the first power conversion module  71  and the second power conversion module  72  corresponding to one of the battery sets  73 ,  74  is faulty, the normal one of the first power conversion module  71  and the second power conversion module  72  can still supply power to the load to achieve the effect of redundant power supply. 
         [0007]    Each of the first power conversion module  71  and the second power conversion module  72  of the foregoing DC converter is composed of an isolated converter, and the isolated converter is equipped with at least one transformer. To any communication system or server system, regardless of the system itself or the power supply therefor, how to reduce the size of the system and the power supply has long been a critical subject. However, due to the transformer required in each of the first and second power conversion modules  71 ,  72 , size reduction naturally becomes a challenge to the foregoing DC converter. 
       SUMMARY OF THE INVENTION 
       [0008]    An objective of the present invention is to provide a DC converter composed of a non-isolated conversion module and an isolated conversion module and requiring less number of transformer for reducing the space occupied by the transformers used in multiple isolated converters of conventional DC converters. 
         [0009]    To achieve the foregoing objective, the DC converter has a non-isolated conversion module and an isolated conversion module. 
         [0010]    The non-isolated conversion module is implemented based on a redundant structure and has a first power conversion loop, a second power conversion loop, and an energy storage element. The first power conversion loop and the second power conversion loop are connected and commonly share the energy storage element. 
         [0011]    The isolated conversion module has a set of input terminals and a set of output terminals. The set of input terminals is connected to the energy storage element of the non-isolated conversion module. 
         [0012]    The first and second power conversion loops of the non-isolated conversion module in the foregoing DC converter convert DC power outputted from two battery sets and then output the converted DC power to the isolated conversion module. The isolated conversion module further supplies the converted DC power to a load. As the first and second power conversion loops in the non-isolated power conversion module have no transformer therein, the size of the non-isolated conversion module can be significantly reduced. Besides, the post-stage isolated conversion module has only one transformer. Accordingly, the DC converter of the present invention is significantly smaller than conventional DC converters, thereby resolving the issue of the conventional DC converters, which is bulky in size due to the use of multiple transformers therein. 
         [0013]    Another objective of the present invention is to provide a power supply system with a reduced size because of less number of transformer used therein. 
         [0014]    To achieve the foregoing objective, the power supply system has an AC to DC converter, a DC converter and two battery sets. 
         [0015]    The AC to DC converter has a set of AC input terminals and a set of DC output terminals. The set of AC input terminals are adapted to connect to a mains power. 
         [0016]    The DC converter has a set of DC input terminals and a set of DC output terminals. The set of DC input terminals are connected to the set of DC output terminals of the AC to DC converter. 
         [0017]    The two battery sets are bridged over the set of DC input terminals of the DC converter. 
         [0018]    As including the foregoing DC converter, the power supply system has the advantage of reducing the size thereof. 
         [0019]    Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a functional block diagram of a DC converter in accordance with the present invention; 
           [0021]      FIG. 2  is a circuit diagram of a first embodiment of a non-isolated conversion module in the DC converter in  FIG. 1 ; 
           [0022]      FIG. 3  is a circuit diagram of a second embodiment of a non-isolated conversion module in the DC converter in  FIG. 1 ; 
           [0023]      FIG. 4  is a circuit diagram of a third embodiment of a non-isolated conversion module in the DC converter in  FIG. 1 ; 
           [0024]      FIG. 5  is a circuit diagram of a fourth embodiment of a non-isolated conversion module in the DC converter in  FIG. 1 ; 
           [0025]      FIG. 6  is a functional block diagram of a power supply system in accordance with the present invention; 
           [0026]      FIG. 7  is a functional block diagram of a conventional power supply system; and 
           [0027]      FIG. 8  is a functional block diagram of a DC converter in the conventional power supply system in  FIG. 7 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0028]    With reference to  FIG. 1 , a DC converter has a non-isolated conversion module  10 , an isolated conversion module  20  and a controller  30 . 
         [0029]    The non-isolated conversion module  10  has a first power conversion loop  11  and a second power conversion loop  12 . Each of the first power conversion loop  11  and the second power conversion loop  12  has a positive terminal Vcom and a negative terminal RTN 1 , RTN 2 . IN the present embodiment, the DC converter further has a first EMI (Electromagnetic interference) filter  41  and a second EMI filter  42 . The positive terminal Vcom and the negative terminal RTN 1  of the first power conversion loop  11  is connected to a first battery set  103  through the first EMI filter  41 . The positive terminal Vcom and the negative terminal RTN 2  of the second power conversion loop  12  is connected to a second battery set  104  through the second EMI filter  42 . Positive terminals V+ of the first battery set  103  and the second battery set  104  are commonly connected and further connected to the positive terminals Vcom of the first power conversion loop  11  and the second power conversion loop  12 . Negative terminals of the first battery set  103  and the second battery set  104  are respectively connected to the negative terminals RTN 1 , RTN 2  of the first power conversion loop  11  and the second power conversion loop  12 . 
         [0030]    The controller  30  is connected to the first power conversion loop  11 , the second power conversion loop  12 , and the isolated conversion module  20  to control power conversion in the non-isolated conversion module  10  and the isolated conversion module  20 . 
         [0031]    With reference to  FIG. 2 , a first embodiment of the non-isolated conversion module  10  has a first power conversion loop  11  and a second power conversion loop  12 . The first power conversion loop  11  and the second power conversion loop  12  in the present embodiment are buck converters. 
         [0032]    The first power conversion loop  11  has a first diode D 1 , a first switch Q 1 , a first inductor L 1  and an energy storage element. In the present embodiment, the energy storage element is an output capacitor C. The output capacitor C has a first end and a second end. The first end of the output capacitor C and a cathode of the diode D 1  are connected to the positive terminal Vcom of the first power conversion loop  11 , and the second end of the output capacitor C is connected to one end of the first inductor L 1 . The other end of the first inductor L 1  is connected to the anode of the first diode D 1  and the first switch Q 1 . In the present embodiment, the first switch is a field effect transistor. The drain of the first switch Q 1  is connected to the other end of the first inductor L 1  and the anode of the first diode D 1 . The source of the first switch Q 1  is connected to the negative terminal RTN 1  of the first power conversion loop  11 . The gate of the first switch Q 1  is connected to and controlled by the controller  30 . 
         [0033]    The second power conversion loop  12  has a second diode D 2 , a second switch Q 2 , a second inductor L 2  and an energy storage element. In the present embodiment, the energy storage element shares the output capacitor C in the first power conversion loop  11 . The first end of the output capacitor C and the cathode of the second diode D 2  are commonly connected to the positive terminal Vcom of the second power conversion loop  12 . The second end of the output capacitor C is connected to one end of the second inductor L 2 . The other end of the second inductor L 2  is connected to the anode of the second diode D 2  and the second switch Q 2 . Similar to the first switch Q 1  in the first power conversion loop  11 , the second switch Q 2  is also a field effect transistor. The drain of the second switch Q 2  is connected to the other end of the second inductor L 2  and the anode of the second diode D 2 . The source of the second switch Q 2  is connected to the negative terminal RTN 2  of the second power conversion loop  12 . The gate of the second switch Q 2  is connected to and controlled by the controller  30 . 
         [0034]    The first end and the second end of the output capacitor C constitute a positive output terminal Vout and a negative output terminal RTN of the non-isolated conversion module  10 , and are connected to a set of input terminals of the isolated conversion module  20 . 
         [0035]    The controller  30  alternately drives the first power conversion loop  11  and the second power conversion loop  12  of the non-isolated conversion module  10  to convert power of the first battery set  103  and the second battery set  104  into a DC power with a configured voltage to the isolated conversion module  20  for the isolated conversion module  20  to convert the configured voltage of the DC power into another configured voltage and supply the DC power to a load. Operation of the non-isolated conversion module  10  is described in detail as follows. 
         [0036]    As to the first power conversion loop  11 , when the first switch Q 1  is turned on, current flows through the output capacitor C and the first inductor L 1 , voltage of the output capacitor C rises up, and the first inductor L 1  gets charged. When the first switch Q 1  is turned off, the first inductor L 1  discharges energy to charge the output capacitor C through the first diode D 1 . On the other hand, when the second switch Q 2  of the second power conversion loop  12  is turned on, a current flows through the output capacitor C and the second inductor L 2 , the voltage of the output capacitor C rises up, and the second inductor L 2  is charged. When the second switch Q 2  is turned off, the second inductor L 2  discharges energy to charge the output capacitor C through the second diode D 2 . The first power conversion loop  11  and the second power conversion loop  12  are alternately driven to supply DC power to the isolated conversion module  20 . DC power outputted from the isolated conversion module  20  may be positive voltage or negative voltage. 
         [0037]    Since the first power conversion loop  11  and the second power conversion loop  12  of the non-isolated conversion module  10  have no transformer therein and the post-stage isolated conversion module has only one transformer, the issue of space unduly occupied by transformers can be effectively resolved. 
         [0038]    With reference to  FIG. 3 , a second embodiment of the non-isolated conversion module  10  has a first power conversion loop  11 ′ and a second power conversion loop  12 ′. The first power conversion loop  11 ′ and the second power conversion loop  12 ′ in the present embodiment are boost converters. 
         [0039]    The first power conversion loop  11 ′ has a first diode D 1 , a first switch Q 1 , a first inductor L 1  and an output capacitor C. The output capacitor C has a first end and a second end. The first end of the output capacitor C and the drain of the first switch Q 1  are connected to the positive terminal Vcom of the first power conversion loop  11 ′. The second end of the output capacitor C is connected to the anode of the first diode D 1 . The cathode of the first diode D 1  is connected to the source of the first switch Q 1 . The source of the first switch Q 1  is connected to one end of the first inductor L 1 . The other end of the first inductor L 1  is connected to the negative terminal RTN 1  of the first power conversion loop  11 ′. The gate of the first switch Q 1  is connected to and controlled by the controller  30 . 
         [0040]    The second power conversion loop  12 ′ has a second diode D 2 , a second switch Q 2 , a second inductor L 2  and an output capacitor. The second power conversion loop  12 ′ and the first power conversion loop  11 ′ share the same output capacitor C. The first end of the output capacitor C and the drain of the second switch Q 2  are connected to the positive terminal Vcom of the first power conversion loop  11 ′. The second end of the output capacitor C is connected to the anode of the second diode D 2 . The cathode of the second diode D 2  is connected to the source of the second switch Q 2 . The source of the second switch Q 2  is further connected to one end of the second inductor L 2 . The other end of the second inductor L 2  is connected to the negative terminal RTN 2  of the second power conversion loop  12 ′. The gate of the second switch Q 2  is connected to and controlled by the controller  30 . 
         [0041]    The present embodiment differs from the first embodiment in that the first power conversion loop  11 ′ and the second power conversion loop  12 ′ of the non-isolated conversion module  10  boost voltage of power from the first battery set  103  and the second battery set  104  instead of lowering voltage of power from the first battery set  103  and the second battery set  104 . The boosted voltage is further converted by the isolated conversion module  20  into DC power with another configured voltage, which may be positive voltage or negative voltage. Detailed operation of the non-isolated conversion module  10  is described as follows. 
         [0042]    The operation of the first power conversion loop  11 ′ is depicted first. When the first switch Q 1  is turned on, the first inductor L 1  is charged. When the first switch Q 1  is turned off, the first inductor L 1  discharges energy stored therein to charge the output capacitor C, and a current flows through the output capacitor C and the first diode D 1 . 
         [0043]    The operation of the second power conversion loop  12 ′ is depicted as follows. When the second switch Q 2  is turned on, the second inductor L 2  is charged. When the second switch Q 2  is turned off, the second inductor L 2  discharges energy stored therein to charge the output capacitor C, and a current flows through the output capacitor C and the second diode D 2 . The first power conversion loop  11  and the second power conversion loop  12  are alternately driven to supply DC power to the isolated conversion module  20 . Similarly, DC power outputted from the isolated conversion module  20  may be positive voltage or negative voltage. 
         [0044]    With reference to  FIG. 4 , a third embodiment of the non-isolated conversion module  10  differs from the first embodiment in two additional current detection elements  51 ,  52 . The two current detection elements  51 ,  52  are respectively connected with the negative terminals RTN 1 , RTN 2  of the first power conversion loop  11  and the second power conversion loop  12 . The current detection elements  51 ,  52  are further connected to the controller  30  for the controller  30  to sense an input current of the non-isolated conversion module  10 . The current detection element  51 ,  52  may be a hall element, a resistor or a current transformer (CT). 
         [0045]    As the positive terminals Vcom of the first power conversion loop  11  and the second power conversion loop  12  are commonly connected, the current detection elements  51 ,  52  respectively connected to the negative terminals RTN 1 , RTN 2  allow the controller  30  to accurately determine input current to the first power conversion loop  11  and the second power conversion loop  12  and control the first power conversion loop  11  and the second power conversion loop  12  for current sharing thereof. When an output current of the non-isolated conversion module  10  is Iout and output currents of the first power conversion loop  11  and the second power conversion loop  12  are I 1 , I 2  respectively, Iout=I 1 +I 2  and I 1 =I 2 . As to current sharing and voltage sharing performed by the controller  30 , a master-slave method or an active current sharing method can be adopted. With further reference to  FIG. 1 , the foregoing design facilitates determination of the specification of two pre-stage no fuse breakers  105 ,  106 . When specification downgrade of the no fuse breaker determined according to the foregoing approaches is permitted, cost down of the present invention is possible. 
         [0046]    Although the first power conversion loop  11  and the second power conversion loop  12  in the present embodiment are buck converters, the current sharing and voltage sharing applicable in the present embodiment is also applicable to boost converters like the first power conversion loop  11 ′ and the second power conversion loop  12 ′ as shown in  FIG. 5 . 
         [0047]    From the foregoing, the DC converter of the present invention is composed of a non-isolated conversion module and an isolated conversion module. As the first power conversion loop and the second power conversion loop in the non-isolated conversion module have no transformer and the post-stage isolated conversion module has only one transformer, the DC converter of the present invention occupies significantly less space relative to conventional DC converters having at least two transformers. 
         [0048]    With reference to  FIG. 6 , a power supply system  100  in accordance with the present invention has the foregoing DC converter, and has an AC to DC converter  101 , a DC converter  102  and two battery sets. 
         [0049]    The AC to DC converter  101  has an AC input terminal and a DC output terminal. The AC input terminal is connected to a mains power. 
         [0050]    The DC converter  102  may be one of the DC converters in the foregoing embodiments. The DC converter  102  has a DC input terminal and a DC output terminal. The DC input terminal of the DC converter  102  is composed of the positive terminals and the negative terminals of the first power conversion loop and the second power conversion loop, and is connected to the DC output terminal of the AC to DC converter  101 . 
         [0051]    The two battery sets are bridged over the DC input terminal of the DC converter  102 . Specifically, the battery sets include a first battery set  103  and a second battery set  104 . Positive terminals of the first battery set  103  and the second battery set  104  are commonly connected to the positive terminals of the first power conversion loop and the second power conversion loop in the DC converter  102 . A negative terminal of the first battery set  103  is connected to the negative terminal of the first power conversion loop in the DC converter  102 . A negative terminal of the second battery set  104  is connected to the negative terminal of the second power conversion loop of the DC converter  102 . 
         [0052]    By adopting the DC converters in the foregoing embodiments, the power supply system reduces the number of transformer in its DC converter design. The size reduction in the DC converters also facilitates the same to be implemented in the power supply system. 
         [0053]    Even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.