Abstract:
A power converter includes semiconductor device, a driver device, a current sensor, a control device, and a capacitor. The semiconductor device has a plurality of switching elements for converting a direct current to an alternating current, the direct current being supplied from a direct current terminal. The driver device controls an operation of the plurality of switching elements provided in the semiconductor device. The current sensor detects the alternating current. The control device controls an operation of the driver device in accordance with the alternating current that has been detected by the current sensor. The capacitor is connected with the direct current terminal. The driver device and the control device are mounted on the same printed board. The driver device is arranged above the semiconductor device.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to power converters and in particular to a power converter used to control a motor for a hybrid vehicle. 
   2. Description of the Related Art 
   A power converter used to drive a motor for a hybrid vehicle or an electric vehicle supplies a driving voltage of 42 V to 600 V, which is higher than a typical load voltage of 14 V for a vehicle. Also, those power converters supply a driving current of several hundreds amperes, and accordingly it is required to reduce noise. In addition, it is necessary to suppress an increase in internal temperature due to heat generated by a semiconductor device and a capacitor. 
   JP-A-2005-287273 discloses a power converter having a structure capable of reducing noise, in which semiconductor devices that generate an alternating output voltage are arranged adjacent to a noise filter. In addition, JP-A-2004-282804 discloses an inverter having a structure capable of suppressing an increase in temperature, in which heat exchanger plates are provided on an upper surface of a semiconductor device, and a control device is attached to the heat exchanger plates. 
   SUMMARY OF THE INVENTION 
   In the abovementioned power converter, however, the semiconductor devices arranged adjacent to the noise filter are separately placed at two positions. In this arrangement, since a control board on which the semiconductor devices are mounted is affected by switching noise generated by the semiconductor devices, two filters are required to be provided on the control board in order to reduce noise. This causes the configuration of the circuit to be complicated. Also, noise may be amplified due to the complicated configuration of the circuit. Furthermore, since a control device is arranged adjacent to the semiconductor devices and the noise filter, the control device may be affected by heat generated by the semiconductor devices and the noise filter. This causes an excessive increase in temperature, resulting in difficulty in using the power converter for a vehicle operating at a relatively high ambient temperature. 
   In addition, in the abovementioned inverter, a drive circuit and a control circuit are partitioned by the heat exchanger plate. Thus, each interface circuit for the drive circuit and the control circuit is long, and the control circuit is arranged on the semiconductor device. Due to the configuration, the control device may be affected by switching noise generated by the semiconductor device. Also, this may cause an erroneous operation. 
   One of objects of the present invention is to provide a power converter with reduced switching noise. Another object of the present invention is to provide a power converter having a structure capable of reducing an effect of switching noise. Furthermore, it is still another object of the present invention to provide a power converter having a structure capable of suppressing an increase in temperature of the power converter and capable of being used for a vehicle or the like operating at a high ambient temperature. 
   In order to accomplish the abovementioned objects, a representative power converter according to the present invention comprises: a semiconductor device having a plurality of switching elements capable of converting a direct current to an alternating current, the direct current being supplied from a pair of positive and negative direct current terminals; a driver device for controlling operations of the switching elements provided in the semiconductor device; a current sensor for detecting the alternating current; a control device for controlling an operation of the driver device based on the alternating current that has been detected by the current sensor; and a capacitor connected between the direct current terminals. The driver device and the control device are mounted on the same printed board. The driver device is arranged above the semiconductor device. 
   Preferably, the representative power converter further comprises: an alternating current bus bar for transmitting to an alternating current terminal the alternating current that has been converted by the semiconductor device; and a capacitor bus bar used to electrically connect the direct current terminals, the capacitor and the semiconductor device. The semiconductor device, the alternating current bus bar, and the capacitor bus bar are arranged on substantially the same plane. In addition, the capacitor bus bar is placed above the capacitor, and the control device is placed above the capacitor bus bar. 
   Furthermore, preferably, the semiconductor device includes: a first switching element group forming an inverter unit for converting a direct current to a three phase alternating current; and a second switching element group forming a converter unit for changing a voltage between direct currents. In this case, more preferably, the semiconductor device further includes a noise filter composed of a first coil. The noise filter is connected in series between the second switching element group and a second direct current terminal which is different from the direct current terminals described above. 
   Furthermore, preferably, the power converter further comprises a cooling device for cooling the semiconductor device. 
   The present invention provides a power converter having a structure capable of reducing switching noise. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram showing the configuration of a power converter according to a first embodiment of the present invention. 
       FIG. 2  is a schematic plan view showing the power converter according to the first embodiment. 
       FIG. 3  is a schematic, cross-sectional, plan view showing the power converter according to the first embodiment. 
       FIG. 4  is a schematic side view showing the power converter according to the first embodiment. 
       FIG. 5  is another schematic side view showing the power converter according to the first embodiment. 
       FIG. 6  is another block diagram showing the configuration of the power converter according to the first embodiment. 
       FIG. 7  is a block diagram showing the entire configuration of a vehicle with a motor generator system installed therein according to the second embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   A first embodiment of the present invention will be described below in detail with reference to the accompanying drawings. 
   First Embodiment 
     FIG. 1  is a block diagram showing the configuration of a power converter according to a first embodiment of the present invention.  FIG. 2  is a schematic plan view showing the power converter shown in  FIG. 1 .  FIG. 3  is a schematic, cross-sectional, plan view showing the power converter when viewed from the same direction as that in  FIG. 2 .  FIGS. 4 and 5  are schematic side views each showing the power converter according to the first embodiment of the present invention. 
   In  FIGS. 1 to 5 , a power converter  100  includes a semiconductor motor device  110 . The semiconductor motor device  110  has metal oxide semiconductor field effect transistors (MOS FETs)  111   a ,  111   b ,  111   c ,  111   d ,  111   e ,  111   f , and a motor board  120 . Each of the MOS FETs  111   a ,  111   b ,  111   c ,  111   d ,  111   e , and  111   f  functions as a switching element. In addition, two chips, which are arranged in parallel to each other, are mounted on the motor board  120  by soldering for each of the MOS FETs  111   a ,  111   b ,  111   c ,  111   d ,  111   e  and  111   f.    
   The MOS FETs  111   a  and  111   b  are connected in series in a vertical direction by use of aluminum wire lines  131  and the motor board  120  so as to form an arm. The MOS FETs  111   c  and  111   d  are connected in the same manner as the connection of the MOS FETs  111   a  and  111   b . Also, the MOS FETs  111   e  and  111   f  are connected in the same manner as the connection of the MOS FETs  111   a  and  111   b . Positive and negative direct current input/output sections  121   a ,  122   a , positive and negative direct current input/output sections  121   c ,  122   c , positive and negative direct current input/output sections  121   e ,  122   e  are provided on one side of the motor board  120 . The alternating current input/output sections  123   a ,  123   c ,  123   e  are provided on the other side of the motor board  120 . The positive and negative direct current input/output sections  121   a ,  122   a  and the alternating current input/output section  123   a  are provided for the arm formed by the MOS FETs  111   a  and  111   b . Also, the positive and negative direct current input/output sections  121   c ,  122   c  and the alternating current input/output section  123   c  are provided for the arm formed by the MOS FETs  111   c  and  111   d . In addition, the positive and negative direct current input/output sections  121   e ,  122   e  and the alternating current input/output section  123   e  are provided for the arm formed by the MOS FETs  111   e  and  111   f.    
   A semiconductor converter device  150  includes MOS-FETs  151   a ,  151   b  and a converter board  160 . Two chips, which are arranged in parallel to each other, are mounted on the converter board  160  by soldering for each of the MOS-FETs  151   a ,  151   b . In addition, the MOS-FETs  151   a ,  151   b  are connected in series in the vertical direction by use of aluminum wire lines  171  and the converter board  160 . 
   Positive and negative direct current input/output sections  161 ,  162  are provided on one side of the converter board  160 , and an alternating current input/output section  163  is provided on the other side of the converter board  160 . The motor board  120  and the converter board  160  are fixed to an aluminum die cast chassis  10  so that the positive and negative direct current input/output sections  121   a ,  121   c ,  121   e ,  122   a ,  122   c ,  122   e ,  161 ,  162  are placed on one side of the motor board  120  and the converter board  160  and the alternating current input/output sections  123   a ,  123   c ,  123   e ,  163  are placed on the other side of the motor board  120  and the converter board  160 . 
   The direct current input/output sections  121   a ,  121   c ,  121   e ,  161  are connected to a positive capacitor bus bar  201 . The direct current input/output sections  122   a ,  122   c ,  122   e ,  162  are connected to a negative capacitor bus bar  202 . Aluminum wire lines  301  are used for those connections. 
   The alternating current input/output sections  123   a ,  123   c ,  123   e  are connected to alternating current bus bar  211 ,  212 ,  213  by using aluminum wire lines  311 , respectively. The direct current input/output section  162  is connected to a converter bus bar  221  by using the aluminum wire lines  311 . 
   The capacitor bus bar  201 ,  202 , the alternating current bus bar  211 ,  212 ,  213 , and the converter bus bar  221  are fixed to a resin case  20  by integral molding. The MOS FETs  111   a ,  111   b ,  111   c ,  111   d ,  111   e ,  111   f ,  151   a ,  151   b  are respectively connected to gate pins  401   a ,  401   b ,  401   c ,  401   d ,  401   e ,  401   f ,  401   g ,  401   h  by using aluminum wire lines  321  so that the MOS FETs each supply a drive signal. 
   It should be noted that the number of the aluminum wire lines  131 , the number of the aluminum wire lines  171 , the number of the aluminum wire lines  301 , and the number of the aluminum wire lines  311  are not limited to the numbers as shown in  FIG. 3 . The numbers of the aluminum wire lines  131 ,  171 ,  301 ,  311  may be increased or reduced if necessary. In addition, in  FIG. 3 , the aluminum wire lines  131 ,  171 ,  301 ,  311 ,  321  are partially illustrated, and other parts thereof are not illustrated. 
   In the present embodiment, although the aluminum wire lines are used for the electrical connections, the connections are not limited to the aluminum wire lines. Instead of the aluminum wire lines, a plate-shaped metal plate(s) may be used for the electrical connections. Replacement of a part or all of the aluminum wire lines with the plate-shaped metal plate(s) makes it possible to improve the reliability of the power converter. In this case, the replacement contributes to a reduction in inductance of the power converter. 
   The motor board  120  may be divided for each arm or for each MOS FET. The converter board  160  may be divided for each MOS FET. Even in this case, similar effects to the first embodiment can be obtained. The motor board  120  and the converter board  160  can be configured by using a single board to obtain similar effects to the first embodiment. 
   The number of the chips for each of the MOS FETs  111   a ,  111   b ,  111   c ,  111   d ,  111   e ,  111   f ,  151   a ,  151   b  is not limited to two. The number of the chips for each of the MOS FETs may be increased or reduced if necessary. In addition, instead of each of the MOS FETs, a combination of an insulated gate bipolar transistor (IGBT) and a fly-wheel diode, or a bipolar transistor may be used to obtain similar effects to those in the case of the MOS FETs. 
   Electrolytic capacitors  21 ,  22 ,  23 , an inductor  30  composed of a single phase coil, an electrolytic capacitor  40  for rectification, and a noise filter  50  composed of a single phase coil are fixed to the chassis  10 . Positive terminals of the electrolytic capacitors  21 ,  22 ,  23  are connected to the positive capacitor bus bar  201 , while negative terminals of the electrolytic capacitors  21 ,  22 ,  23  are connected to the negative capacitor bus bar  202 . 
   The positive capacitor bus bar  201  is connected to a secondary positive direct current terminal  61  by using a direct current bus bar  231 . The negative capacitor bus bar  202  is connected to a ground boss  11  of the chassis  10  and a negative terminal of the electrolytic capacitor  40  by using a direct current bus bar  232 . 
   The noise filter  50  has the one end connected to a primary positive direct current terminal  62  by using a direct current bus bar  233 , and has the other end connected to a positive terminal of the electrolytic capacitor  40  and the one end of the inductor  30  by using a direct current bus bar  234 . 
   The inductor  30  has the other end connected to the converter bus bar  221  through the converter bus bar  222  and  223 . Alternating current terminals  71 ,  72 ,  73  are connected to the alternating current bus bar  211 ,  212 ,  213  through alternating current bus bar  214 ,  215 ,  216 , respectively. 
   The primary direct current terminal  62 , the secondary direct current terminal  61 , the alternating current terminals  71 ,  72 ,  73  are fixed to the resin case  20  by integral molding. The capacitor bus bars  201 ,  202 , the direct current bus bars  231 ,  232 ,  233 ,  234 , and the converter bus bar  223  are arranged on the same plane on which the motor board  120  and the converter board  160  are placed. The electrolytic capacitors  21 ,  22 ,  23 , the inductor  30 , the electrolytic capacitor  40 , and the noise filter  50  are arranged below the motor board  120  and the converter board  160  and on the side of the chassis  10 . 
   The electrolytic capacitors  21 ,  22 ,  23  are arranged on the side opposite to the side of the alternating current input/output sections  123   a ,  123   c ,  123   e  provided on the motor board  120  and the alternating current input/output section  163  provided on the converter board  160 . The alternating current terminals  71 ,  72 ,  73  are arranged on the side of the alternating current input/output sections  123   a ,  123   c ,  123   e ,  163 . 
   Although screws are used for the connections of each of the bus bars shown in  FIG. 3 , the connections thereof are not limited to the connections using the screws. In addition, the positions of the inductor  30 , the electrolytic capacitor  40  and the noise filter  50  are not limited to those in the present embodiment. Also, the positions of the primary direct current terminal  62 , the secondary direct current terminal  61  and the ground boss  11  of the chassis  10  are not limited to those in the present embodiment. Instead of the electrolytic capacitors  21 ,  22 ,  23  and  40 , film capacitors or a combination of a film capacitor(s) and an electrolytic capacitor(s) can be used to obtain similar effects to those in the first embodiment described above. 
   The chassis  10  includes cooling fins  12  and a cover  13  used for a cold water path. The cooling fins  12  are molded by aluminum die casting. The cooling fins  12  are mounted on lower surfaces of the motor board  120  and the converter board  160 . The chassis  10  also serves as negative poles of the primary direct current terminal and the secondary direct current terminal. 
   The resin case  20  is formed by resin molding and fixed to the chassis  10  to fix and insulate each of the bus bars. Instead of the cooling fins  12 , air cooling fins or another cooling device may be used to obtain similar effects to those in the first embodiment. 
   A material having high thermal conduction such as an aluminum cast and a steel plate may be used for the chassis  10  to obtain similar effects to the present embodiment described above. Instead of providing each of the negative poles to the chassis  10 , a negative terminal may be provided to the chassis  10  so that the chassis  10  is fixed to the resin case  20 . 
   A driver device  701 , a control device  801 , motor current sensors  611 ,  612 ,  613 , and a converter current sensor  621  are mounted on a printed circuit board (PCB)  601 , which is a single printed board. The PCB  601  is fixed to a PCB boss  29  of the resin case  20  by use of screws  641  so that the PCB  601  overlaps and is parallel to a plane on which the motor board  120 , converter board  160 , the capacitor bus bars  201 ,  202 , the direct current bus bars  231 ,  232 ,  233 ,  234 , and the converter bus bar  223  are arranged. In this case, the PCB  601  may be connected with the chassis  10  at a part of fixed portions of the PCB  601  by the screws  641  or by another connection method so that the PCB  601  is grounded. 
   The driver device  701  is arranged to overlap the motor board  120  and the converter board  160 . Also, the control device  801  is arranged to overlap the capacitor bus bars  201 ,  202 , the direct current bus bars  231 ,  232 ,  233 ,  234 , and the converter bus bar  223 . 
   The motor current sensors  611 ,  612 ,  613  and the converter current sensor  621  are arranged on the side of the alternating current terminals  71 ,  72 ,  73  of the PCB  601 . With this arrangement, the driver device  701  is arranged to be surrounded by the control device  801  and the motor current sensors  611 ,  612 ,  613 . 
   The PCB  601  is connected with gate pins  401   a ,  401   b ,  401   c ,  401   d ,  401   e ,  401   f ,  401   g , and  401   h  through pin connection holes  651  and has connectors  631 ,  632 . The connectors  631 ,  632  are used for external interfaces of the control device  801 . Connector housings  27  and  28 , which are provided for the connectors  631  and  632  respectively, are molded to the resin case  20 . 
   The alternating current bus bars  211 ,  212 ,  213  extend through current detection units of the motor current sensors  611 ,  612 ,  613 , respectively. Also, the converter bus bar  221  extends through a current detection unit of the converter current sensor  621 . The motor current sensors  611 ,  612 ,  613 , the converter current sensor  621 , the control device  801 , the driver device  701 , and the connectors  631 ,  632  are connected on the PCB  601 . 
   Although an insulation type current sensor is used for each of the motor current sensors  611 ,  612 ,  613  and the converter current sensor  621 , another current sensor such as a shunt resistor may be used for each of them to obtain similar effects to those in the present embodiment described above. The PCB  601  may be fixed by using another method such as caulking, instead of using the screws  641 . External interfaces, which are each formed by a connector and a harness, may be used instead of using the connectors  631 ,  632  and the connector housings  27 ,  28 . 
   The power converter  100  according to the present invention has a cooling device. Heat generated by the semiconductor motor device  110  and the semiconductor converter device  150  is transmitted to a cooling medium through the cooling fins  12  provided in the chassis  10 . The heat is blocked by the resin case  20  so that it is not transmitted to the PCB  601 . 
   Heat generated by the electrolytic capacitors  21 ,  22 ,  23 , the inductor  30 , the electrolytic capacitor  40 , and the noise filter  50  is transmitted to the cooling medium through the cooling fins  12  provided in the chassis  10 . Since the heat is blocked by the capacitor bus bars  201 ,  202 , the direct current bus bars  231 ,  232 ,  233 ,  234  the converter bus bar  223  and the resin case  20 , it is not transmitted to the PCB  601 . 
   As a cooling device, a complete cooling medium path is formed in the chassis  10  so that the semiconductor motor device  110  and the semiconductor converter device  150  are arranged above the cooling medium path. With this configuration, it is possible to cool the heat. In order to the cooling efficiency, a metal base such as a copper base, which has the semiconductor motor device  110  and the semiconductor converter device  150  mounted thereon, may be directly mounted on an opening formed in the cooling medium path to completely form the cooling medium path. In this case, cooling fins can be formed on a portion of the metal base, which is in contact with the cooling medium. 
   This configuration makes it possible to minimize a distance between the semiconductor motor device  110 , the semiconductor converter device  150  and the PCB  601 , or a distance of an interface between the semiconductor motor device  110 , the semiconductor converter device  150  and the driver device  701 . This can reduce switching noise. 
   In addition, the motor current sensors  611 ,  612 ,  613 , and the converter current sensor  621  are not intersected with the semiconductor motor device  110 , the semiconductor converter device  150  and the driver device. Also, the control device  801  and interfaces of the abovementioned current sensors are not intersected with the semiconductor motor device  110 , the semiconductor converter device  150  and the driver device. Thus, the motor current sensors  611 ,  612 ,  613 , and the converter current sensor  621 , the control device  801  and the interfaces are not affected by switching noise. 
   Therefore, it is possible to easily install the power converter according to the present invention in, for example, a vehicle that is driven by an internal combustion engine without imposing any limitation on a position at which the power converter is installed. The distance between the semiconductor motor device  110  and the PCB  601  and the distance between the semiconductor converter device  150  and the PCB  601  can be minimized to reduce the size of the power converter. This also makes it possible to easily install the power converter according to the present invention in such a vehicle. 
   Next, a modification according to the first embodiment will be described below with reference to  FIG. 6 .  FIG. 6  is a block diagram showing a power converter  100 . In  FIG. 6 , the power converter  100  includes MOS FETs  111   a ,  111   b ,  111   c ,  111   d ,  111   e ,  111   f , an electrolytic capacitor  21 , a driver device  701 , and a control device  801 . Each interface and each structure of the above devices are configured similarly to those provided in the power converter  100  according to the first embodiment. The configuration shown in  FIG. 6  provides similar effects to those obtained by the configuration of the power converter  100  according to the first embodiment. 
   Second Embodiment 
     FIG. 7  is a diagram showing a vehicle according to a second embodiment of the present invention, the vehicle having the power converter  100  according to the modification mounted therein. In  FIG. 7 , a vehicle  910  has an engine  920 . A driving force of the engine  920  is transmitted to front wheels  926 A,  926 B through a transmission  922  and first front wheel shafts  924 A,  924 B to drive the front wheels  926 A,  926 B. 
   Although the vehicle  910  has the engine  920  which drives the front wheels  926 A,  926 B in the description above, the engine  920  may drive the rear wheels. Alternatively, a vehicle having six or more wheels, such as a truck, a tractor, a trailer and the like may be applied to the second embodiment. 
   A motor generator  940  is provided in an engine room. The motor generator  940  is composed of an alternating current motor which is coupled with the engine  920  and a belt  941 . The motor generator  940  drives the engine  920  through the belt  941 , or drives the front wheels  926 A,  926 B through a drive support, the engine  920 , and the transmission  922 . The engine  920  is driven through the belt  941 , and the front wheels  926 A,  926 B are driven through the engine  920  and the transmission  922 , so as to charge an in-vehicle battery  942 , a power supply for other devices  943  provided in the vehicle  910 , and a 12 V battery  944 . 
   It should be noted that the motor generator  940  can generate a battery voltage (e.g., 42 V) normally higher than a voltage (e.g., 12 V) supplied from the in-vehicle battery by using, for example, a coil field type three-phase alternating current motor so as to drive the engine  920  or the front wheels  926 A,  926 B. 
   Although the motor generator  940  is coupled with the engine  920  and the belt  941 , another method for the coupling, such as coupling with use of a chain, may be used. The motor generator  940  may be placed between the engine  920  and the transmission  922 , or placed in the transmission  922  to obtain similar effects to those in the case where it is placed as shown in  FIG. 7 . 
   The motor generator  940 , the in-vehicle battery  942 , the other devices  943 , and the 12 V battery  944  are connected through the power converter  100 . The power converter  100  supplies power generated by the motor generator  940  to the other devices  943 , the 12 V battery  944 , and the in-vehicle battery  942 . Also, the power converter  100  supplies power supplied from the in-vehicle battery  942  to the motor generator  940 . With a motor generator system having the abovementioned configuration, the vehicle  910  has an idling stop function and a regenerative brake function to improve the fuel efficiency. 
   The power converter according to the present invention makes it possible to reduce switching noise. Also, the power converter according to the present invention makes it possible to reduce effects of switching noise, which suppresses an increase in temperature of the control device. Furthermore, the size of the power converter can be reduced. 
   The power converter according to the modification can be easily installed in, for example, a vehicle that is driven by an internal combustion engine. A vehicle, which has such a power converter installed therein, has an idling stop function and a regenerative brake function. This contributes to improve the fuel efficiency.