Abstract:
An integrated converter and method are provided that combine an onboard charger and a low voltage direct current converter. The integrated improves the charging efficiency of the battery of a vehicle and supplies the high density power to an electronic device load. The charging efficiency of the high voltage battery and electricity transmitting efficiency to the low voltage converter is improved using the integrated converter. Furthermore, the low voltage converter receives high density power since the low voltage converter is input with a substantially stable voltage from the integrated converter.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to and the benefit of Korean Patent Application No. 10-2013-0095373 filed in the Korean Intellectual Property Office on Aug. 12, 2013, the entire contents of which are incorporated herein by reference. 
       BACKGROUND 
       [0002]    (a) Field of the Invention 
         [0003]    The present invention relates to a converter apparatus and method which charge a high voltage battery and a low voltage battery of an electric vehicle and supply necessary power for an electronic device load. 
         [0004]    (b) Description of the Related Art 
         [0005]    A plug-in hybrid electric vehicle (PHEV) or an electric vehicle (EV) charges a high voltage battery of the vehicle using a common alternating current (AC) power on board charger (OBC), and charges a low voltage battery of the vehicle using a low voltage direct current-direct current (DC-DC) converter (LDC) and supplies power for the electronic device load. The OBC generates a voltage (e.g., SoC minimum˜SoC maximum) that the battery requires based on a state of charge (SoC) of the battery. Then, the LDC supplies a variable high voltage input from the battery by converting to the input electronic device load and the low voltage battery. 
         [0006]    In recent years, studies on improving the efficiency of the OBC which charges the high voltage battery of the electric vehicle and supplying the high density power to the LDC has been in progress. 
         [0007]    The above information disclosed in this section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. 
       SUMMARY 
       [0008]    The present invention provides an integrated converter apparatus and method combining OBC and LDC which improves the charging efficiency of the battery of the electric vehicle, and supplies the high density power to an electronic device load. 
         [0009]    According to an exemplary embodiment of the present invention, the integrated converter apparatus of the electric vehicle may include: a power converting module that converts an AC voltage input thereto into a first DC voltage and transmits the first DC voltage to a low voltage converter when the electric vehicle is charged; and a bidirectional buck-boost module that increases the first DC voltage to a second DC voltage and transmits the second DC voltage to a high voltage battery when the electric vehicle is charged, and reduces a third DC voltage output from the high voltage battery and transmits the reduced third DC voltage to the low voltage converter when the electric vehicle is operated. 
         [0010]    The power converting module may include an AC power rectifying module that converts the AC voltage into the first DC voltage; a boosting module that increases the first DC voltage; and a rectifying module hat rectifies the increased first DC voltage. The boosting module may include at least one of a power factor correction boost (PFC boost) circuit, a continuous conduction mode (CCM) PFC circuit, and a semi-bridgeless interleaved PFC circuit. The rectifying module may include at least one of a phase shift full bridge circuit, a center tap synchronous rectifier circuit, a half bridge circuit, a series resonant converter circuit, a center tap diode rectifier circuit, and a full bridge diode rectifier circuit. The bidirectional buck-boost module may increase the first DC voltage to the second DC voltage and reduce the third DC voltage by operating a switch of the bidirectional buck-boost module. The low voltage converter may supply electric power to the low voltage battery of the electric vehicle and an electronic device load. The high voltage battery may supply the electric power to a motor/generator (MG) of the electric vehicle. 
         [0011]    Additionally, the present invention provides a method of operating a converter of an electric vehicle. The method of operating a converter of an electric vehicle may include: converting an AC voltage input thereto into a first DC voltage and transmitting the first DC voltage to a low voltage converter when the electric vehicle is charged; increasing the first DC voltage to a second DC voltage and transmitting the second DC voltage to a high voltage battery when the electric vehicle is charged; and reducing a third DC voltage output from the high voltage battery and transmitting the reduced third DC voltage to the low voltage converter when the electric vehicle is operated. 
         [0012]    The method may further include increasing the first DC voltage and rectifying the increased first DC voltage. In particular, the increasing of the first DC voltage may be implemented by at least one of a power factor correction boost (PFC boost) circuit, a continuous conduction mode (CCM) PFC circuit, and a semi-bridgeless interleaved PFC circuit. In addition, the rectifying the increased first DC voltage may be implemented by at least one of a phase shift full bridge circuit, a center tap diode rectifier circuit, a center tap synchronous rectifier circuit, a half bridge circuit, and a full bridge diode rectifier circuit. 
         [0013]    Furthermore, the transmitting of the second DC voltage may include increasing the first DC voltage to the second DC voltage by operating a switch. The transmitting of the third DC voltage may include reducing the third DC voltage by operating a switch. In addition, the low voltage converter may supply electric power to a low voltage battery of the electric vehicle and an electronic device load. The high voltage battery may supply electric power to a motor/generator (MG) of the electric vehicle. 
         [0014]    According to an exemplary embodiment of the present invention, the charging efficiency of the high voltage battery and power transmission efficiency to the low voltage converter may improve using the integrated converter apparatus. In other words, a conduction loss of a first element of the DC/DC voltage transformation module of the integrated converter apparatus may be reduced and a diode forward voltage reduction included in the rectifying module may be reduced, thereby reducing a power loss. In addition, the power loss in an output protection diode may be reduced since the integrated converter apparatus does not use the output protection diode. Furthermore, the low voltage converter may receive high density power since the low voltage converter may be input with a stable voltage from the integrated converter apparatus. Further, volume of the low voltage converter may be reduced since the low voltage converter may be implemented by a low-capacity element, thus improving the efficiency of the low voltage converter. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  is an exemplary block diagram of a charging system of an electric vehicle according to an exemplary embodiment of the present invention; 
           [0016]      FIGS. 2A and 2B  are exemplary diagrams illustrating a circuit of a charging system of an electric vehicle according to an exemplary embodiment of the present invention; and 
           [0017]      FIG. 3  to  FIG. 7  are exemplary diagrams illustrating a circuit of a charging system of an electric vehicle according to another exemplary embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]    It is understood that the term “vehicle” or “vehicular” or other similar term as used herein is inclusive of motor vehicles in general such as passenger automobiles including sports utility vehicles (SUV), buses, trucks, various commercial vehicles, watercraft including a variety of boats and ships, aircraft, and the like, and includes hybrid vehicles, electric vehicles, plug-in hybrid electric vehicles, hydrogen-powered vehicles, fuel cell vehicles, and other alternative fuel vehicles (e.g. fuels derived from resources other than petroleum). As referred to herein, a hybrid vehicle is a vehicle that has two or more sources of power, for example both gasoline-powered and electric-powered vehicles. 
         [0019]    Although exemplary embodiment is described as using a plurality of units to perform the exemplary process, it is understood that the exemplary processes may also be performed by one or plurality of modules. Additionally, it is understood that the term controller/control unit refers to a hardware device that includes a memory and a processor. The memory is configured to store the modules and the processor is specifically configured to execute said modules to perform one or more processes which are described further below. 
         [0020]    Furthermore, control logic of the present invention may be embodied as non-transitory computer readable media on a computer readable medium containing executable program instructions executed by a processor, controller/control unit or the like. Examples of the computer readable mediums include, but are not limited to, ROM, RAM, compact disc (CD)-ROMs, magnetic tapes, floppy disks, flash drives, smart cards and optical data storage devices. The computer readable recording medium can also be distributed in network coupled computer systems so that the computer readable media is stored and executed in a distributed fashion, e.g., by a telematics server or a Controller Area Network (CAN). 
         [0021]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
         [0022]    In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described exemplary embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification. 
         [0023]    Throughout the specification, unless explicitly described to the contrary, each of the terms “unit”, “-er”, “-or”, “module”, and “block” described in the specification refers to a unit that processes at least one function or operation, which may be implemented by hardware, software, or a combination of thereof. 
         [0024]      FIG. 1  is an exemplary block diagram of an integrated converter of an electric vehicle according to an exemplary embodiment of the present invention. Referring to  FIG. 1 , a charging system  100  of the electric vehicle according to an exemplary embodiment of the present invention may include an integrated converter  110 , a high voltage battery  120 , and a low voltage DC/DC converter  130 . 
         [0025]    The integrated converter  110  may be configured to convert AC input power into DC power, charge the high voltage battery  120 , and supply the power to the low voltage DC/DC converter  130 . The high voltage battery  120  may be configured to supply the power to a plurality of inverters  30  using the power charged through the integrated converter  110 , to operate a motor/generator (MG) or supply the power to the low voltage DC/DC converter  130 . The low voltage DC/DC converter  130  may be configured to receive the power from the integrated converter  110  or high voltage battery  120 , to charge a low voltage battery  10  or supply the power to an electronic device load  20 . 
         [0026]      FIG. 2  is an exemplary diagram illustrating an integrated converter circuit of the electric vehicle according to an exemplary embodiment of the present invention. Referring to  FIG. 2 , a charging system  100 , executed by a controller, according to an exemplary embodiment of the present invention may include the integrated converter  110 , the high voltage battery  120 , and the low voltage DC/DC converter  130 . The integrated converter  110  may include an AC power rectifying module  111 , a power factor correction boost module  112 , a DC/DC voltage transformation module  113 , a rectifying module  114 , and a bidirectional buck-boost module  115 . 
         [0027]    According to an exemplary embodiment of the present invention, the power factor correction boost module  112  of the integrated converter as illustrated  FIG. 2  may be implemented by a power factor correction boost (PFC boost) converter, the DC/DC voltage transformation module  113  may be implemented by a phase shifted full bridge converter, and the rectifying module  114  may be implemented by a center tap diode rectifier. 
         [0028]      FIG. 2A  is an exemplary diagram illustrating the charging system when the electric vehicle is charging according to an exemplary embodiment of the present invention. A rectifier diode (D 1  to D 4 ) of the AC power rectifying module  111  may be configured to generate a full-wave rectification waveform from a waveform of an AC voltage (V in ), and a capacitor C 1  may be configured to transmit a DC voltage to the power factor correction boost module  112  by discharging a charged voltage at a falling curve of the full-wave rectification waveform. 
         [0029]    The power factor correction boost module  112  may be configured to correct a power factor (pf) using a power factor correction inductor L 1  and a power factor correction capacitor C 2 , and increase a DC voltage by operating a switch M 1 . The power factor correction boost module  112  of the integrated converter  110  according to an exemplary embodiment of the present invention may be configured to reduce the size of the integrated converter by designing the correction capacitor C 2  to be smaller in size. Since the low voltage DC/DC converter  130  may receive energy from a capacitor of the bidirectional buck-boost module  115 , the reduced capacitor C 2  may be used. 
         [0030]    Further, the increased DC voltage may be output as a minimum SoC of the battery through the DC/DC voltage transformation module  113  and the rectifying module  114 . In other words, the DC voltage may be transmitted from the rectifying module  114  to the low voltage DC/DC converter  130 . The DC/DC voltage transformation module  113  may be configured to transform a size of the DC voltage by adjusting a duty cycle ratio with a switch (M 2  to M 5 ). In addition, the rectifying module may be configured to transform an output voltage from a secondary coil of the DC/DC voltage transformation module to the DC voltage using rectifier diodes (D 1  and D 2 ). 
         [0031]    The bidirectional buck-boost module  115  may be configured to increase the DC voltage output from the rectifying module  114 , and charge the high voltage battery  120  to a necessary voltage (e.g., a predetermined voltage). A voltage of the capacitor C 3  may be formed consistently regardless of a voltage condition of the battery. A consistent voltage formed on the capacitor C 3  may become a SoC minimum voltage or maximum voltage. The bidirectional buck-boost module  115  may be configured to perform a role of a boost converter to generate a necessary voltage of the high voltage battery during the high voltage battery  120  charging. The bidirectional buck-boost module  115  may be configured to generate an output voltage based on the duty ratio of a switch M 6  as shown in Equation 1 below, wherein D 6  is the ratio of duty of switch M 6  to duty of switch M 7 . 
         [0000]    
       
         
           
             
               
                 
                   
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         [0032]    The high voltage battery  120  may be configured to transmit a voltage (V out     —     high ) to operate a motor generator  40  to an inverter  30  connected to the motor generator  40  when the electric vehicle is operated. The inverter  30  may be configured to convert the DC voltage of the high voltage battery  120  into an AC voltage, and transmit the AC voltage to the motor generator  40 . According to an exemplary embodiment of the present invention, the bidirectional buck-boost module  115  may be configured to transmit a voltage of the capacitor C 3  based on the duty ratio of a switch M 7  to the low voltage DC/DC converter  130  when the electric vehicle is operated. The bidirectional buck-boost module  115  may be configured to operate as a reduction converter when the electric vehicle is operated, to allow the bidirectional buck-boost module  115  to maintain (e.g., fix) a voltage V C3  despite receiving the voltage from the high voltage battery. In addition, the bidirectional buck-boost module  115  may be configured to generate a necessary voltage of the low voltage battery by reducing a voltage V C31  after maintaining the voltage V C31  as a maximum voltage, and may maintain a voltage of the low voltage DC/DC converter as a SoC maximum voltage by increasing a voltage of the low voltage battery when the electric vehicle is operated. In other words, the voltage V C3  may be maintained as a minimum or maximum SoC voltage using the bidirectional buck-boost module  115  when the electric vehicle is charged or operated. 
         [0033]    Furthermore, according to an exemplary embodiment of the present invention, the bidirectional buck-boost module  115  may be configured to increase the DC voltage by changing a switching duty ratio of switches (M 6  and M 7 ), and an output voltage from the bidirectional buck-boost module  115  may include in the range of a minimum SoC voltage to a maximum SoC voltage. In other words, the DC/DC voltage transformation module  113  may be designed regardless of a charging voltage of the high voltage battery  120  since the bidirectional buck-boost module  115  may be configured to transmit a necessary voltage of the high voltage battery  120 . 
         [0034]    The DC/DC voltage transformation module  113  may be configured to generate a voltage regardless of a voltage condition of the high voltage battery  120  and reduce current flow through a first switch element of the DC/DC voltage transformation module  113 . A low voltage may be transmitted to the rectifying module  114  according to these features, to reduce a voltage stress of the rectifying module  114  and to allow the integrated converter  110  to use a rectifying switch which has a reduced conduction loss. In addition, the bidirectional buck-boost module  115  may be configured to charge the high voltage battery  120  normally by changing the boost duty ratio even though the AC power input to the integrated converter  110  may be instantaneously shut off. Furthermore, the integrated converter  110  may not use a traditional output protection diode connected to an output terminal of on board charger. Therefore, a power loss in the output protection diode may be minimized. 
         [0035]    Meanwhile, a voltage transmitted to the low voltage DC/DC converter  130  may be a minimum or maximum SoC voltage output from the DC/DC voltage transformation module  113  and the rectifying module  114 . A low voltage DC/DC voltage transformation module  131  of the low voltage DC/DC converter  130  may adapt a minimum or maximum SoC voltage to a low voltage (V out     —     low ) to be supplied from the low voltage DC/DC converter  130  by adjusting the duty ratio. The output voltage from a traditional low voltage DC/DC converter  130  may be flexible since the traditional low voltage DC/DC converter  130  receives a voltage from the high voltage battery  120 . However, the low voltage DC/DC converter  130  according to an exemplary embodiment of the present invention may be configured to receive a stable voltage from the rectifying module  114  of the integrated converter  110  regardless of a voltage of the high voltage battery. 
         [0036]    The integrated converter  110  that receives the AC power when the electric vehicle is charged may be configured to charge the high voltage battery  120  and supply the power to the low voltage DC/DC converter  130  according to an exemplary embodiment of the present invention. In other words, the integrated converter  110  may use a minimum or maximum SoC voltage output from the rectifying module  114  while supplying the power to the low voltage DC/DC converter  130 , and may use a particular size of the minimum or maximum SoC voltage increased or reduced using the bidirectional buck-boost module  115  during charging the high voltage battery  120 . 
         [0037]      FIGS. 2A and 2B  are exemplary diagrams illustrating a charging system when the electric vehicle is operated according to an exemplary embodiment of the present invention. A charged power in the high voltage battery  120  may be supplied to the low voltage DC/DC converter  130  since the AC power may not input from the exterior when the electric vehicle is operated. Furthermore, the high voltage battery  120  may be charged by receiving electricity generated in the motor generator  40  when the electric vehicle is operated. 
         [0038]    In particular, a voltage output from the high voltage battery  120  may be transmitted to the low voltage DC/DC converter  130  through a switch M 7 . A voltage output from the high voltage battery  120  may be a fixed voltage depending on a duty ratio of an inductor L 3  and the switch M 7  included in the bidirectional buck-boost module  115 . Further, the low voltage DC/DC voltage transformation module  131  of the low voltage DC/DC converter  130  may be configured to adapt a minimum or maximum SoC voltage to a voltage supplied by the low voltage DC/DC converter  130  based on adjustment of the duty ratio, and output the voltage V out     —     low  by rectifying in a rectifying module  132 . 
         [0039]    A voltage input to the low voltage DC/DC converter  130  may be substantially constant regardless of the electric vehicle being charged or operated. The output voltage from the traditional low voltage DC/DC converter  130  may also be flexible since the traditional low voltage DC/DC converter  130  receives a voltage from the high voltage battery  120 . However, the low voltage DC/DC converter  130  may be configured to receive a substantially stable voltage from the bidirectional buck-boost module  115  of the integrated converter  110 . 
         [0040]    The high voltage battery  120  according to an exemplary embodiment of the present invention may become a power source of the low voltage DC/DC converter  130  while the electric vehicle is operated. In other words, the efficiency of the low voltage DC/DC converter  130  may be improved since a constant voltage transmitted by the bidirectional buck-boost module  115  output from the high voltage battery  120  may be supplied to the low voltage DC/DC converter  130 . In addition, a rectifying switch which has a minimal conduction loss may be used on account of reducing a voltage stress of the rectifying module of the low voltage DC/DC converter  130  based on the input voltage changing. 
         [0041]      FIG. 3  is an exemplary diagram illustrating a circuit of an integrated converter of the electric vehicle according to another exemplary embodiment of the present invention. A power factor correction boost module  311  as illustrated in  FIG. 3  may be implemented by a continuous conduction mode (CCM) PFC, and a DC/DC voltage transformation module  312  may be implemented by a phase-shifted full-bridge DC/DC converter. Moreover, the integrated converter  310  as illustrated in  FIG. 3  may include a bidirectional buck-boost module  320  and a low voltage DC/DC converter  330  implemented by an active forward converter. 
         [0042]      FIG. 4  is an exemplary diagram illustrating a circuit of an integrated converter of the electric vehicle according to another exemplary embodiment of the present invention. A power factor correction boost module  411  as illustrated in  FIG. 4  may be implemented by a CCM PFC, and a DC/DC voltage transformation module  412  may be implemented by a phase-shifted full-bridge DC/DC converter. Moreover, the integrated converter apparatus  410  as illustrated in  FIG. 4  may include a bidirectional buck-boost module  420  and a low voltage DC/DC converter  430  implemented by an active forward converter. 
         [0043]      FIG. 5  is an exemplary diagram illustrating a circuit of the integrated converter of the electric vehicle according to another exemplary embodiment of the present invention. A power factor correction boost module  511  as illustrated in  FIG. 5  may be implemented by a CCM PFC, and a DC/DC voltage transformation and rectifying module  512  may be implemented by a resonant full bridge DC/DC converter and a center tap diode rectifier. Moreover, the integrated converter  510  as illustrated in  FIG. 5  may include a bidirectional buck-boost module  520  and a low voltage DC/DC converter  530  implemented by a synchronous active forward converter. 
         [0044]      FIG. 6  is an exemplary diagram illustrating a circuit of the integrated converter of the electric vehicle according to another exemplary embodiment of the present invention. A power factor correction boost module  611  as illustrated in  FIG. 6  may be implemented by a CCM PFC, and a DC/DC voltage transformation and rectifying module  612  may be implemented by a resonant full bridge DC/DC converter and a full bridge diode rectifier. Moreover, the integrated converter  610  as illustrated in  FIG. 6  may include a bidirectional buck-boost module  620  and a low voltage DC/DC converter  630  implemented by a synchronous active forward converter. 
         [0045]      FIG. 7  is an exemplary diagram illustrating a circuit of the electric vehicle&#39;s charging system according to another exemplary embodiment of the present invention. A power factor correction boost module  711  as illustrated in  FIG. 7  may be implemented by a CCM PFC, and a DC/DC voltage transformation and rectifying module  712  may be implemented by a phase-shifted full-bridge DC/DC converter and a full bridge diode rectifier. Moreover, the integrated converter  710  as illustrated in  FIG. 7  may include a bidirectional buck-boost module  720  and a low voltage DC/DC converter  730  implemented by a full bridge sensor tap synchronous rectifier. 
         [0046]    As described above, according to an exemplary embodiment of the present invention, charging efficiency of the high voltage battery and power transmission efficiency to the low voltage converter may be improved using the integrated converter. In other words, a conduction loss of a first transformer switch of the DC/DC voltage transformation and rectifying module of the integrated converter may be reduced to extend switching capability. Therefore, a diode forward voltage drop included in the rectifying module may be reduced, thus reducing a power loss. In addition, the power loss in an output protection diode may be reduced since the integrated converter may not use the output protection diode. Furthermore, the low voltage converter may receive high density power since the low voltage converter may input a substantially stable voltage from the integrated converter. In addition, volume of the low voltage converter may be reduced since the low voltage converter may be implemented by a low-capacity element, improving the efficiency of the low voltage converter can be improved. 
         [0047]    While this invention has been described in connection with what is presently considered to be exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the accompanying claims.