Abstract:
An apparatus for converting power of a power source used for a main unit mounted on a vehicle includes: a first circuit that converts the power into a first power and supplies the first power to a first auxiliary unit mounted on the vehicle; a second circuit that converts the power into a second power and supplies the second power to a second auxiliary unit mounted on the vehicle; a first board on which the first circuit is mounted; a second board on which the second circuit is mounted; and a connecting member that electrically connects between the first board and the second board to allow the power of the power source to be conducted therebetween.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based on and claims the benefit of priority from earlier Japanese Patent Application No. 2011-141332 filed on Jun. 27, 2011 the description of which is incorporated herein by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to power conversion apparatuses, and more particularly to a power conversion apparatus having a power conversion circuit that supplies an on-vehicle auxiliary unit with power converted from power supplied to an on-vehicle main unit. 
         [0004]    2. Description of the Related Art 
         [0005]    This type of apparatus has been widely used for power conversion in the vehicle systems. For example, Japanese Patent Application Publication No. 2002-345252 discloses an apparatus provided with a plurality of power conversion circuits. 
         [0006]    Assuming a plurality of power conversion circuits are required to supply power to the on-vehicle auxiliary unit, the space where the power conversion circuits are to be arranged is likely to be restricted, and therefore it is preferable to shrink the power conversion circuits. In this instance, when a plurality of power conversion circuits need to be shrunk, the power conversion circuits can be disposed effectively on a single circuit board. However, since heat radiation from each of the power conversion circuits becomes larger, excessive thermal stress may be applied to the single circuit board. 
       SUMMARY 
       [0007]    An embodiment provides a newly developed power conversion apparatus having a power conversion circuit that supplies power used for an on-vehicle main unit to an on-vehicle auxiliary unit. 
         [0008]    As a first aspect of the embodiment, an apparatus for converting power of a power source used for a main unit mounted on a vehicle includes: a first circuit that converts the power into a first power and supplies the first power to a first auxiliary unit mounted on the vehicle; a second circuit that converts the power into a second power and supplies the second power to a second auxiliary unit mounted on the vehicle; a first board on which the first circuit is mounted; a second board on which the second circuit is mounted; and a connecting member that electrically connects between the first board and the second board to allow the power of the power source to be conducted therebetween. 
         [0009]    According to the first aspect of the embodiment, considering space for disposing the conversion boards is limited, the conversion boards need to be shrunk. However, the first circuit and the second circuit are disposed on separated circuit boards. As a result, an amount of heat radiation from a single conversion board can be reduced so that excessive stress applied to the circuit board can be suppressed. 
         [0010]    As a second aspect of the embodiment, the apparatus includes a casing that accommodates the first board and the second board. The casing includes a first connector that electrically connects between the first circuit and the first auxiliary unit, and a second connector that electrically connects between the second circuit and the second auxiliary unit. The first and second connectors are disposed on the same surface of the casing. 
         [0011]    When the connectors of the first and second circuits are disposed on the same side surface of the casing, comparing to the connectors of the first and second being arranged on each side surface separately, first and second circuits may be arranged to be one-sided to one side surface of the pair of side surfaces facing each other so that location at which heat is generated is one-sided to the one side surface. Therefore, in view of accelerating heat radiation of the first and second circuits, this arrangement would be disadvantageous comparing with the circuit boards being arranged on each of the side surfaces. However, according to the embodiment of the present disclosure, separate circuit boards are arranged in the power conversion apparatus. As a result, degrading heat-radiation characteristics because of the connectors being arranged on the identical side surface, can preferably be compensated for. 
         [0012]    As a third aspect of the embodiment, the apparatus includes a power supply board on which a power supply unit used for supplying the power of the power source to the first and second circuits is disposed; and a casing that accommodates the first board, the second board and the power supply board. The first board, the second board and the power supply board are arranged in a single row, and the power supply board is disposed in an end portion of the casing. 
         [0013]    According to the third embodiment, the power of the power supply board can be sequentially transferred to a circuit board adjacent to the power supply board and the other circuit board which is not adjacent to the power supply board. Therefore, a wiring pattern used for supplying power on the power supply board can readily be accomplished. Moreover, the number of connecting devices mounted on the power supply board can be reduced so that the size of the power supply board which is likely to be large can be shrunk as much as possible. 
         [0014]    As a fourth aspect of the embodiment, the first and second circuits are operated at mutually different switching frequencies. 
         [0015]    The inventors have found that when the switching frequencies of the first and second circuit thereof are different to each other, the power supply unit is shared by the first and second circuits whereby necessary power for the first and second circuits is supplied by the shared power supply unit of which power supply capability (i.e., rated power output) is smaller than sum of the power supply capability of respective power supply units when the power supply units are arranged individually for each of the first and second circuits. Therefore, according to the embodiment, the power supply unit can be shrunk based on the above-described configuration. 
         [0016]    As a fifth aspect of the embodiment, the apparatus includes a casing that accommodates the first board and the second board, and a heat sink is disposed on a surface of the casing to be extended in a direction perpendicular to a direction along which the first and second boards are arranged. 
         [0017]    According to the fifth aspect of the embodiment, the heat-sink is disposed in such a manner. Therefore, compared to the heat-sink extended in a direction along which the first and second boards are arranged, the heat radiation of the first and second boards by the heat sink can be averaged. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    In the accompanying drawings: 
           [0019]      FIG. 1  is a diagram showing a system configuration according to an embodiment; 
           [0020]      FIGS. 2A and 2B  are diagrams showing a configuration of the power conversion unit according to the embodiment; and 
           [0021]      FIG. 2C  is a cross sectional view taken at line A-A of  FIG. 2A . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     First Embodiment 
       [0022]    With reference to the drawings, hereinafter is described the first embodiment in which a power conversion apparatus according to the present disclosure is adapted to a hybrid vehicle. 
         [0023]      FIG. 1  is a diagram showing a system configuration according to the first embodiment. 
         [0024]    A high voltage battery  20  as shown in  FIG. 1  is a power source for supplying power to an on-vehicle main unit as a driving motor of the vehicle. The high voltage battery  20  is a secondary battery having a terminal voltage of about 100 volts, such as a lithium-ion battery or a nickel metal hydride battery. The negative terminal voltage of the high voltage battery  200  is isolated from the vehicle body. For example, a pair of capacitors are connected to both terminals of the high voltage battery and the connection point of the pair of capacitors is connected to the vehicle body so that a center value between a potential at the positive terminal and a potential at the negative terminal of the high voltage battery  20  equals the potential of the vehicle body. 
         [0025]    The high voltage battery  20  is electrically connected to a pair of power supply lines Lp and Ln which are connected to the power supply unit PSC. The power supply unit PSC includes a normal mode choke coil  16  and a smoothing capacitor  18 . The normal mode choke coil  16  is connected to each power supply line Lp and Ln and the smoothing capacitor  18  is connected to the power supply lines Lp and Ln in parallel. 
         [0026]    The inverters INV 1 , INV 2  and INV  3  (i.e., conversion circuit) connected in parallel with each other are connected to the power supply unit PSC. The inverter INV 1  is used for applying three phase AC (alternating current) voltage to a heater  10  mounted on the on-vehicle air conditioner. The inverter  2  is used for applying three phase AC voltage to a motor  12  of a blower fan mounted on the on-vehicle  20 . The inverter INV 3  is used for applying three phase AC voltage to a motor  14  mounted on a water pump for cooling coolant in a cylinder block of the on-vehicle internal combustion engine. The above-described heater  10  is an electric heater designed to be driven by a three phase AC inverter similar to the inverters INV 1 , INV 2  and INV 3 . The heater  10 , the motor  12  of the blower fan and the motor  14  connected to respective inverters INV 1 , INV 2  and INV 3  serves as on-vehicle auxiliary units each corresponding to either the first auxiliary unit or the second auxiliary unit. The inverters INV 1 , INV 2  and INV 3  each corresponds to either the first circuit or the second circuit. 
         [0027]    In this configuration, the inverters INV 1 , INV 2  and INV 3  share the power supply unit PSC. This is because capacitance value of the smoothing capacitor connected to the power supply unit PSC when the inverters INV 1 , INV 2  and INV 3  share the power supply unit PSC becomes smaller than the capacitance value of the smoothing capacitor when each inverter has own power supply unit. However, to decrease the capacitance value of the smoothing capacitor, the switching frequencies fs 1 , fs 2  and fs 3  corresponding to the respective inverters INV 1 , INV 2  and INV 3  should be set to be different values each other. Therefore, according to the first embodiment, these switching frequencies fs 1 , fs 2  and fs 3  are set to be different values. 
         [0028]    The above-described inverters INV 1 , INV 2 , INV 3  and the power supply unit PSC are accommodated in a single casing CA which is made of metal. The on-vehicle electrical load, i.e., the motors  12 ,  14  and the heater  10  are connected to the casing CA externally whereby the casing CA can be shrunk and arranged at a location where suffering damage if the vehicle collides with something can be avoided. 
         [0029]    The above-described casing CA further includes microprocessors  32 ,  34  and  36  which generate control signals of the inverters INV 1 , INV 2  and INV 3  and outputs the control signals to the inverters INV 1 , INV 2  and INV 3 , and the microprocessor  30 . The microprocessor  30  receives a command value used for a control variable of each load (i.e., auxiliary unit) which is inputted externally (from an external device), assigns the command value to the respective microprocessors  32 ,  34  and  36  and outputs the command value to the respective microprocessors. Therefore, each of the microprocessor  32 ,  34  and  36  controls a phase-voltage corresponding to the respective inverters INV 1 , INV 2  and INV 3  in response to the command value inputted externally. Specifically, each of the microprocessors  32 ,  34  and  36  compares the phase-voltage of the inverter with a triangle-wave-shape carrier signal and generates the control signal of the inverters INV 1 , INV 2  and INV 3  based on the result of comparison between the phase-voltage and the carrier signal, so as to control the respective phase-voltage of the inverters. The microprocessor  30  receives the command value via an isolation means such as a photo coupler. The above-described microprocessor  30  and the power supply unit PSC are mounted on a power supply board  40 , the inverter INV 1  and the microprocessor  32  are mounted on a conversion board  42 , the inverter INV 2  and the microprocessor  34  are mounted on a conversion board  44  and, the inverter INV 3  and the microprocessor  36  are mounted on the conversion board  46 . The conversion boards  42 ,  44  and  46  each correspond to either the first board or the second board. 
         [0030]    With reference to  FIGS. 2A and 2B , a structure of the casing CA according to the first embodiment and how the power supply board  40 , the conversion boards  42 ,  44  and  46  are accommodated in the casing CA, are explained as follows. 
         [0031]    As shown in  FIG. 2A , in the casing, the power supply board  40  and the conversion boards  42 ,  44  and  46  are arranged in a single row having gaps (G 1 , G 2  and G 3  as shown in  FIG. 2C ) therebetween. The power supply board  40  and the conversion board  42  are electrically connected via a connecting member  50 . Similarly, the conversion boards  42  and  44  are electrically connected via the connecting member  50 . Further, the conversion boards  44  and  46  are electrically connected via the connecting member  50  as well. The connecting member  50  is a conducting member being embedded into each of the end portions in adjacent two boards. 
         [0032]    Specifically, the connecting member  50  connected between the power supply board  40  and the conversion board  42  includes a pair of power supply path connected to the output terminal of the power supply unit PSC (i.e., positive end and negative end of the smoothing capacitor  18 ) and a signal propagation path in which a command value used for generating the control signals of the inverters INV 1 , INV 2  and INV 3  is transmitted. The connecting member  50  connected between the conversion board  42  and the conversion board  44  includes a pair of power supply path connected to the output terminal of the power supply unit PSC (i.e., positive end and negative end of the smoothing capacitor  18 ) and a signal propagation path in which a command value used for generating the control signals of the INV 2  and INV 3  is transmitted. Further, the connecting member  50  connected between the conversion board  44  and the conversion board  46  includes a pair of power supply path connected to the output terminal of the power supply unit PSC (i.e., positive end and negative end of the smoothing capacitor  18 ) and a signal propagation path in which a command value used for generating the control signal of the INV 3  is transmitted. 
         [0033]    Regarding the above-described casing CA, connectors  60   a,    60   b ,  60   c,    60   d  and  60   e  which are made of resin are arranged on a side surface of the casing CA to be in single row shape. The connector  60   a  connects the above-described ECU  22  and the power supply board  40  (interface  30 ), and is disposed facing the power supply board  40 . The connector  60   b  connects the above-described pair of power supply line Lp and Ln and the power supply unit PSC of the power supply board  40 , and is disposed facing the power supply board  40 . The connector  60   c  connects the heater  10  and the conversion board  42  (inverter INV 1 ), and is disposed facing the conversion board  42 . Moreover, the connector  60   d  connects the motor  12  of the blower fan and the conversion board  44  (inverter INV 2 ), and is disposed facing the conversion board  44 . The connector  60   e  connects the motor  14  of the water pump and the conversion board  46  (inverter INV 3 ), and is disposed facing the conversion board  46 . 
         [0034]      FIG. 2B  is a diagram showing a surface of the casing CA. As shown in  FIG. 2B , a heat sink (ribs  62   a  and  62   b ) is arranged on the surface of the casing CA (arranged on R 1  and R 2  areas respectively as shown in  FIG. 2B ). The heat sink is arranged such that the longitudinal direction of each rib is disposed along a direction where the connectors  60   a,    60   b ,  60   c,    60   d  and  60   e  are extended from the casing CA. The Ribs  62   a  and  62   b  are used to expand an area being exposed to the atmosphere surrounding the heat sink whereby the heat exchange between the heat sink and the atmosphere can be enhanced. 
         [0035]    As described above, in the first embodiment, the connectors  60   a ,  60   b,    60   c,    60   d  and  60   e  are disposed on a side surface of the casing CA so as to improve a working property when the casing CA is installed to an on-vehicle system. Assuming the connectors are arranged on both side surfaces (a pair of side surfaces facing each other) of the casing CA, it may be necessary to change the type of supporting the casing CA depending on which connectors on the both side surfaces are used for connecting. As a result, the working property may be decreased. 
         [0036]    According to the first embodiment, the power supply board  40 , the conversion boards  42 ,  44  and  46  are separated as individual boards. As a first reason, since the circuit board tends to bend to have curvature, when the circuit components to be mounted on the power supply board  40  and the conversion boards  42 ,  44  and  46  are mounted on a single circuit board, surface area of the board becomes larger so that the curvature may become significant. Therefore, if the circuit board has curvature, even when a mold material covers the surface of the circuit board to avoid a dielectric breakdown between wiring of the circuit board and the electronic devices, the mold material may be peeled off thereby degrading the insulating performance. 
         [0037]    The second reason is to enhance a capability of heat radiation from the circuit board. Specifically, according to the first embodiment, the connectors  60   a,    60   b,    60   c,    60   d  and  60   e  are arranged on only one side surface of the casing CA so that the power switching elements (i.e., inverter INV 1 , INV 2  and INV 3 ) need to be disposed on the one side in the casing CA and an amount of heat at the one side in the casing CA increases. Accordingly, the circuit board is divided to enhance the heat radiation when comparing with only one circuit board being used. Further, gaps are disposed between circuit boards, and the connecting member  50  having high heat-radiation characteristics connects between the circuit boards, whereby the effect of the heat radiation can be significant. 
         [0038]    Moreover, the power supply unit PSC used for supplying power to the INV 1 , INV 2  and INV 3  mounted on the respective conversion circuit board  42 ,  44  and  46  is mounted to the power supply board  40 , whereby heat radiation from the conversion boards  42 ,  44  and  46  can be further enhanced. That is, since the circuit components mounted on the power supply board  40  include a component such as smoothing capacitor  18  of which height is larger than that of the circuit components mounted on the conversion board  42 ,  44  and  46 , as shown in  FIG. 2B , the length of the rib  62   b  (L 1 ) extended from the casing CA is set to be shorter than that of the rib  62   a  (L 2 ) at the conversion circuits  42 ,  44  and  46 . Therefore, assuming the power supply unit PSC is disposed to each of the conversion boards  42 ,  44  and  46 , the length of the rib  62   a  extended from the conversion boards  42 ,  44  and  46  becomes shorter, thereby degrading heat-radiation characteristics of the conversion boards  42 ,  44  and  46 . 
         [0039]    The above-described rib  62   a  is formed to be perpendicular to a direction along which the conversion boards  42 ,  44  and  46  are arranged (i.e., a direction where the conversion boards are facing each other) so that the capability of heat-radiation in the respective conversion boards  42 ,  44  and  46  can be equivalent to each other. 
         [0040]    The power supply board  40  including the above-described power supply unit PSC is disposed in the end portion of the casing CA so that the power supply board  40  can be shrunk. However, if the power supply board  40  is disposed in the central area of the casing CA, the power line which is connected to the positive and negative terminals of the smoothing capacitor  18  needs to be connected to the connecting member  50  disposed at the respective end portions of the power supply board  40 . Therefore, size of the power supply board  40  becomes larger. 
       Other Embodiment 
       [0041]    The above-described embodiment can be modified as follows. Regarding the connecting member  50 , it is not limited to the conducting member embedded into the end portions where adjacent circuit boards face each other. For example, a bonding wire soldered to a wiring portion in the respective circuit boards can be used to electrically connect the circuit boards. 
         [0042]    Regarding the casing, it is not limited to the circuit boards arranged in a single row, however, the circuit boards can be arranged in double rows. In this case, to avoid interference between wirings, the connectors may preferably be disposed on an opposing pair of surfaces of a hexahedral casing. 
         [0043]    Moreover, the casing is not limited to the hexahedron shape. For example, a casing having ellipse shape can be employed. The casing is not limited to a single casing, however, a plurality of casing can be used such that the a casing accommodating the power supply board  40 , a casing accommodating the conversion board  42 , a casing accommodating the conversion board  44  and a casing accommodating the conversion board  46  can be prepared separately and these casings are connected each other by a connecting member disposed on the respective side surfaces of the plurality of casing. In this case, capability of heat-radiation in the respective circuit boards can be further enhanced. 
         [0044]    Regarding the connector, it is not limited to arrange all of the connectors on one surface of the hexahedron of the casing. For example, the connectors can be arranged on two surfaces that face each other. In this case, a difference between an average distance (average) from the surface facing the inverter to a surface of a pair of surfaces, and an average distance from the surface facing the inverter and the other surface of the pair of surfaces, can be reduced so that locations where the heat is produced can be balanced in the casing. 
         [0045]    The connectors can be made of metal instead of resin whereby the heat-radiation performance at the connector portion can be enhanced. 
         [0046]    Regarding the power supply board, it is not limited to the power supply board disposed at the end portion of the casing. 
         [0047]    As to the power supply board, the power supply board may include not only the microprocessor  30 , but also microprocessors  32 ,  34  and  36 . 
         [0048]    Regarding the number of conversion boards, it is not limited to three boards, for example, two boards or four or more conversion boards can be used. Further the number of auxiliary units connected to the respective conversion boards is not limited to three, for example, two auxiliary units or four or more auxiliary units can be used. Moreover, one conversion board does not necessarily include only one conversion circuit, however, one conversion board can include two or more conversion circuits. 
         [0049]    Also, devices used for generating a control signal to control the switching element of the conversion board can be mounted on the conversion board. 
         [0050]    Regarding the heat sink, it is not limited to the rib  62   a  and the rib  62   b  of which size is smaller than the rib  62   a.  However, the rib  62   a  and the rib  62   b  having the same size can be used, when the smoothing capacitor  18  included in the power supply unit PSC is shrunk so that the dimension of the casing CA is shrunk significantly. 
         [0051]    Regarding the ribs  62   a  and  62   b,  it is not limited to a rib extending in a direction perpendicular to a direction along which the conversion boards are arranged. However, the ribs  62   a  and  62   b  can be extended in the direction along which the conversion boards are arranged. 
         [0052]    Regarding the conversion circuit, it is not limited to three phase inverters. For example, a single phase inverter can be used for the heater  10 . When a five phase motor is used for the motor  12  of the blower fan, the inverter used for the motor  12  will be a five phase inverter. 
         [0053]    Further, it is not limited to a DC-AC conversion circuit having a switch element that selectively connects positive/negative terminals of a DC power source and a terminal of an on-vehicle auxiliary unit. 
         [0054]    Moreover, it is not limited to the conversion circuits of which switching frequencies are changed depending on the conversion boards. It is not limited to a hybrid vehicle, that is, for storing energy supplied to an on-vehicle drive motor, only an output unit that outputs an electric energy (i.e., secondary battery, fuel cell) may be provided. Even in this case, the present disclosure has an advantage when the output unit is used for a power source of a plurality of on-vehicle auxiliary units such as a blower fan or a heater.