Abstract:
A power semiconductor device M includes: first and second frames for feeding unipolar power from outside; first and second switching units which are series-connected between the first and second frames; an output frame for outputting AC power which is generated by conduction and shutoff of each switching unit to outside; a connecting wire for electrically connecting at least one pair of the first frame and the first switching unit, the first switching unit and the output frame, the output frame and the second switching unit, and the second switching unit and the second frame; a third frame which is arranged close to the output frame; and a branching wire for electrically connecting the first switching unit or the second switching unit to the third frame, whereby sufficiently suppressing surge voltage which takes place within the module even using an external snubber circuit.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a power semiconductor device, which is applicable to, for example, general-purpose inverters or power converters. 
   2. Description of the Related Art 
     FIG. 7  is a plan view showing an example of an internal configuration of a conventional power semiconductor module.  FIG. 8  is a circuit diagram relevant to a phase-W circuit of the power semiconductor module of  FIG. 7 . Here, exemplified is a case of converting unipolar power, which is rectified from AC power, into three-phase AC power (phase-U, phase-V, phase-W). 
   The power semiconductor module M is provided with frames F 1  to F 5  made of electrically conductive material on an electrically insulating substrate. The frames F 1  and F 5  are fed with external unipolar power. For example, a terminal P of the frame F 1  is connected with a positive line of an AC power rectifying circuit, while a terminal N of the frame F 5  is connected with a negative line of the AC power rectifying circuit. 
   A terminal W of the frame F 2  outputs the phase-W of AC power to an external circuit. A terminal V of the frame F 3  outputs the phase-V of AC power to an external circuit. A terminal U of the frame F 4  outputs the phase-U of AC power to an external circuit. 
   On the frame F 1 , mounted are switching devices S 4  to S 6 , such as IGBT (Insulated Gate Bipolar Transistor), and flywheel diodes D 4  to D 6 . The collectors of the switching devices S 4  to S 6  and the cathodes of the diodes D 4  to D 6  are electrically connected to the frame F 1 . 
   The emitter of the switching device S 4  and the anode of the diode D 4  are connected to each other using a short connecting wire, and also to the frame F 4  using a relatively longer connecting wire L 4 . Likewise, the emitter of the switching device S 5  and the anode of the diode D 5  are connected to each other using a short connecting wire, and also to the frame F 3  using a relatively longer connecting wire L 5 . Further, the emitter of the switching device S 6  and the anode of the diode D 6  are connected to each other using a short connecting wire, and also to the frame F 2  using a relatively longer connecting wire L 6 . 
   Meanwhile, on the frame F 2 , mounted are a switching device S 3 , such as IGBT, and a flywheel diodes D 3 . The collector of the switching device S 3  and the cathode of the diode D 3  are electrically connected to the frame F 2 . The emitter of the switching device S 3  and the anode of the diode D 3  are connected to each other using a short connecting wire, and also to the frame F 5  using a relatively longer connecting wire L 3 . 
   On the frame F 3 , mounted are a switching device S 2 , such as IGBT, and a flywheel diodes D 2 . The collector of the switching device S 2  and the cathode of the diode D 2  are electrically connected to the frame F 3 . The emitter of the switching device S 2  and the anode of the diode D 2  are connected to each other using a short connecting wire, and also to the frame F 5  using a relatively longer connecting wire L 2 . 
   On the frame F 4 , mounted are a switching device S 1 , such as IGBT, and a flywheel diodes D 1 . The collector of the switching device S 1  and the cathode of the diode D 1  are electrically connected to the frame F 4 . The emitter of the switching device S 1  and the anode of the diode D 1  are connected to each other using a short connecting wire, and also to the frame F 5  using a relatively longer connecting wire L 1 . 
   Incidentally, for avoiding complexity of the drawing, illustration of the respective gate of the respective IGBT and the respective wire connected with each gate is omitted. 
   In this configuration, the switching devices S 6  and S 3  are series-connected between the frames F 1  and F 5 , which are fed with unipolar power, to control the phase-W of AC power. The switching devices S 5  and S 2  are series-connected to control the phase-V of AC power. The switching devices S 4  and S 1  are series-connected to control the phase-U of AC power. 
   A snubber circuit for suppressing surge voltage which may occur in the outputted AC power, is externally connected to the power semiconductor module M. The snubber circuit is typically composed of capacitor, diode, resistor, etc. 
   Referring to the phase-W of AC power, for example, as shown in  FIG. 8 , a snubber circuit SN 1  is connected between the terminals P and W, and a snubber circuit SN 2  is connected between the terminals N and W. Alternatively to the snubber circuits SN 1  and SN 2 , another snubber circuit SN 3  may be connected between the terminals P and N. 
   For the other phase-U and phase-V of AC power, the snubber circuits SN 1  and SN 2 , or SN 3  are connected like phase-W. 
   In such an internal configuration of the above-described power semiconductor module M, since the frames and the semiconductor devices are mutually connected using the connecting wires L 1  to L 6 , total length of the wiring path where each of main circuit current flows is likely to be relatively larger. Hence, due to inductance of the wiring path, relatively higher surge voltage easily takes place during switching operation of the switching devices S 1  to S 6 . Such a higher surge voltage may increase switching loss of the switching devices S 1  to S 6 , or cause breakage of the devices. 
   As shown in  FIG. 8 , external connection of the snubber circuits SN 1  and SN 2 , or SN 3  with the power semiconductor module M can suppress the surge voltage to some level. 
   However, in a case of the conventional power semiconductor module M having remarkably larger inductances of the connecting wires L 1  to L 6 , it is difficult for the external snubber circuit to sufficiently suppress surge voltage which takes place within the module. 
   The related prior arts are listed as follows: Japanese Patent Unexamined Publications (kokai) JP-2000-82775 A1, JP-3-136412(1991) A1, JP-8-32021(1996) A1, JP-2004-112999 A1. 
   SUMMARY OF THE INVENTION 
   An object of the present invention is to provide a power semiconductor device which can sufficiently suppress surge voltage which takes place within the module even using an external snubber circuit. 
   To achieve the above object, a power semiconductor device according to the present invention, includes: 
   first and second frames for feeding unipolar power from outside; 
   first and second switching units which are series-connected between the first and second frames; 
   an output frame for outputting AC power which is generated by conduction and shutoff of each switching unit to outside; 
   a connecting wire for electrically connecting at least one pair of the first frame and the first switching unit, the first switching unit and the output frame, the output frame and the second switching unit, and the second switching unit and the second frame; 
   a third frame which is arranged close to the output frame; and 
   a branching wire for electrically connecting the first switching unit or the second switching unit to the third frame. 
   Further, a power semiconductor device according to the present invention, includes: 
   first and second frames for feeding unipolar power from outside; 
   first and second switching units which are series-connected between the first and second frames; 
   an output frame for outputting AC power which is generated by conduction and shutoff of each switching unit to outside; 
   a connecting wire for electrically connecting at least one pair of the first frame and the first switching unit, the first switching unit and the output frame, the output frame and the second switching unit, and the second switching unit and the second frame; 
   a third frame which is arranged close to one of the first and second frames; and 
   a branching wire for electrically connecting the output frame and the third frame. 
   Furthermore, a power semiconductor device according to the present invention, includes: 
   first and second frames for feeding unipolar power from outside; 
   first and second switching units which are series-connected between the first and second frames; 
   an output frame for outputting AC power which is generated by conduction and shutoff of each switching unit to outside; 
   a connecting wire for electrically connecting at least one pair of the first frame and the first switching unit, the first switching unit and the output frame, the output frame and the second switching unit, and the second switching unit and the second frame; 
   a third frame which is arranged close to one of the first and second frames; and 
   a branching wire for electrically connecting the other of the first and second frames to the third frame. 
   It is preferable in the present invention that a snubber circuit is connected between the output frame and the third frame. 
   It is preferable in the present invention that a snubber circuit is connected between the one of the first and second frames and the third frame. 
   According to the present invention, an additional third frame is arranged separately from the output frame and the first and second frames and close thereto to connect a branching wire which is separate from the connecting wire with the third frame. Then, by connecting the third frame with an external snubber circuit, wiring length and loop area of the closed loop circuit including the snubber circuit can be reduced, thereby improving the effect of the snubber circuit for suppressing surge voltage. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a plan view showing an example of an internal configuration of a power semiconductor module according to a first embodiment of the present invention. 
       FIG. 2  is a circuit diagram relevant to a phase-W circuit of the power semiconductor module of  FIG. 1 . 
       FIG. 3  is a plan view showing an example of an internal configuration of a power semiconductor module according to a second embodiment of the present invention. 
       FIG. 4  is a circuit diagram relevant to a phase-W circuit of the power semiconductor module of  FIG. 3 . 
       FIG. 5  is a plan view showing an example of an internal configuration of a power semiconductor module according to a third embodiment of the present invention. 
       FIG. 6  is a circuit diagram relevant to a phase-W circuit of the power semiconductor module of  FIG. 5 . 
       FIG. 7  is a plan view showing an example of an internal configuration of a conventional power semiconductor module. 
       FIG. 8  is a circuit diagram relevant to a phase-W circuit of the power semiconductor module of  FIG. 7 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   This application is based on an application No. 2006-195585 filed Jul. 18, 2006 in Japan, the disclosure of which is incorporated herein by reference. 
   Hereinafter, preferred embodiments will be described with reference to drawings. 
   Embodiment 1 
     FIG. 1  is a plan view showing an example of an internal configuration of a power semiconductor module according to a first embodiment of the present invention.  FIG. 2  is a circuit diagram relevant to a phase-W circuit of the power semiconductor module of  FIG. 1 . Here, exemplified is a case of converting unipolar power, which is rectified from AC power, into three-phase AC power (phase-U, phase-V, phase-W). 
   The power semiconductor module M is provided with frames F 1  to F 5  made of electrically conductive material on an electrically insulating substrate, and an additional frame F 6  is arranged close to the frame F 2 . The frames F 1  and F 5  are fed with external unipolar power. For example, a terminal P of the frame F 1  is connected with a positive line of an AC power rectifying circuit, while a terminal N of the frame F 5  is connected with a negative line of the AC power rectifying circuit. 
   A terminal W of the frame F 2  outputs the phase-W of AC power to an external circuit. A terminal V of the frame F 3  outputs the phase-V of AC power to an external circuit. A terminal U of the frame F 4  outputs the phase-U of AC power to an external circuit. 
   On the frame F 1 , mounted are switching devices S 4  to S 6 , such as IGBT (Insulated Gate Bipolar Transistor), and flywheel diodes D 4  to D 6 . The collectors of the switching devices S 4  to S 6  and the cathodes of the diodes D 4  to D 6  are electrically connected to the frame F 1 . 
   The emitter of the switching device S 4  and the anode of the diode D 4  are connected to each other using a short connecting wire, and also to the frame F 4  using a relatively longer connecting wire L 4 . Likewise, the emitter of the switching device S 5  and the anode of the diode D 5  are connected to each other using a short connecting wire, and also to the frame F 3  using a relatively longer connecting wire L 5 . Further, the emitter of the switching device S 6  and the anode of the diode D 6  are connected to each other using a short connecting wire, and also to the frame F 2  using a relatively longer connecting wire L 6 . 
   Meanwhile, on the frame F 2 , mounted are a switching device S 3 , such as IGBT, and a flywheel diodes D 3 . The collector of the switching device S 3  and the cathode of the diode D 3  are electrically connected to the frame F 2 . The emitter of the switching device S 3  and the anode of the diode D 3  are connected to each other using a short connecting wire, and also to the frame F 5  using a relatively longer connecting wire L 3 . 
   On the frame F 3 , mounted are a switching device S 2 , such as IGBT, and a flywheel diodes D 2 . The collector of the switching device S 2  and the cathode of the diode D 2  are electrically connected to the frame F 3 . The emitter of the switching device S 2  and the anode of the diode D 2  are connected to each other using a short connecting wire, and also to the frame F 5  using a relatively longer connecting wire L 2 . 
   On the frame F 4 , mounted are a switching device S 1 , such as IGBT, and a flywheel diodes D 1 . The collector of the switching device S 1  and the cathode of the diode D 1  are electrically connected to the frame F 4 . The emitter of the switching device S 1  and the anode of the diode D 1  are connected to each other using a short connecting wire, and also to the frame F 5  using a relatively longer connecting wire L 1 . 
   In this embodiment, the additional frame F 6  is electrically connected to the anode of the diode D 3  using a branching wire J 1  which branches from the connecting wire L 3 . 
   Incidentally, for avoiding complexity of the drawing, illustration of the respective gate of the respective IGBT and the respective wire connected with each gate is omitted. 
   In this configuration, the switching devices S 6  and S 3  are series-connected between the frames F 1  and F 5 , which are fed with unipolar power, to control the phase-W of AC power. The switching devices S 5  and S 2  are series-connected to control the phase-V of AC power. The switching devices S 4  and S 1  are series-connected to control the phase-U of AC power. 
   In this embodiment, as shown in  FIG. 2 , an external snubber circuit SN 2  is connected between the terminal W of the frame F 2  for outputting the phase-W and a terminal T 1  of the additional frame F 6 . Hence, the snubber circuit SN 2  resides in the closed loop circuit including the terminal T 1 , the frame F 6 , the branching wire J 1 , the switching device S 3  (diode D 3 ), the frame F 2  and the terminal W. 
   In the conventional power semiconductor module, on the other hand, as shown in  FIGS. 7 and 8 , the snubber circuit SN 2  resides in the closed loop circuit including the terminal N, the frame F 5 , the connecting wire L 3 , the switching device S 3  (diode D 3 ), the frame F 2  and the terminal W. 
   Therefore, this embodiment can reduce wiring length and loop area of the closed loop circuit including the snubber circuit SN 2 , thereby improving the effect of the snubber circuit SN 2  for suppressing surge voltage. 
   Here, surge suppression of the phase-W of AC power has been described in detail. Likewise, in case of the phase-U of AC power, an additional frame is arranged close to the frame F 4 , and a branching wire is connected between the frame and the diode D 1 , and an external snubber circuit is connected between a terminal of the frame and the terminal U of the frame F 4 , resulting in the same effect as in phase-W. Moreover, in case of the phase-V of AC power, an additional frame is arranged close to the frame F 3 , and a branching wire is connected between the frame and the diode D 2 , and an external snubber circuit is connected between a terminal of the frame and the terminal V of the frame F 3 , resulting in the same effect as in phase-W. 
   In the above description, discussed was the closed loop circuit of the snubber circuit SN 2  which was connected between the respective frames F 2  to F 4  for outputting AC power and the frame F 5  which is a negative line of unipolar power. Similarly, another closed loop circuit of a snubber circuit SN 1  which is connected between the respective frames F 2  to F 4  and the frame F 1  which is a positive line of unipolar power can be improved. 
   Embodiment 2 
     FIG. 3  is a plan view showing an example of an internal configuration of a power semiconductor module according to a second embodiment of the present invention.  FIG. 4  is a circuit diagram relevant to a phase-W circuit of the power semiconductor module of  FIG. 3 . Here, exemplified is a case of converting unipolar power, which is rectified from AC power, into three-phase AC power (phase-U, phase-V, phase-W). 
   The power semiconductor module M is provided with frames F 1  to F 5  made of electrically conductive material on an electrically insulating substrate, and an additional frame F 7  is arranged close to the frame F 5 . The frames F 1  and F 5  are fed with external unipolar power. For example, a terminal P of the frame F 1  is connected with a positive line of an AC power rectifying circuit, while a terminal N of the frame F 5  is connected with a negative line of the AC power rectifying circuit. 
   A terminal W of the frame F 2  outputs the phase-W of AC power to an external circuit. A terminal V of the frame F 3  outputs the phase-V of AC power to an external circuit. A terminal U of the frame F 4  outputs the phase-U of AC power to an external circuit. 
   On the frame F 1 , mounted are switching devices S 4  to S 6 , such as IGBT, and flywheel diodes D 4  to D 6 . The collectors of the switching devices S 4  to S 6  and the cathodes of the diodes D 4  to D 6  are electrically connected to the frame F 1 . 
   The emitter of the switching device S 4  and the anode of the diode D 4  are connected to each other using a short connecting wire, and also to the frame F 4  using a relatively longer connecting wire L 4 . Likewise, the emitter of the switching device S 5  and the anode of the diode D 5  are connected to each other using a short connecting wire, and also to the frame F 3  using a relatively longer connecting wire L 5 . Further, the emitter of the switching device S 6  and the anode of the diode D 6  are connected to each other using a short connecting wire, and also to the frame F 2  using a relatively longer connecting wire L 6 . 
   Meanwhile, on the frame F 2 , mounted are a switching device S 3 , such as IGBT, and a flywheel diodes D 3 . The collector of the switching device S 3  and the cathode of the diode D 3  are electrically connected to the frame F 2 . The emitter of the switching device S 3  and the anode of the diode D 3  are connected to each other using a short connecting wire, and also to the frame F 5  using a relatively longer connecting wire L 3 . 
   On the frame F 3 , mounted are a switching device S 2 , such as IGBT, and a flywheel diodes D 2 . The collector of the switching device S 2  and the cathode of the diode D 2  are electrically connected to the frame F 3 . The emitter of the switching device S 2  and the anode of the diode D 2  are connected to each other using a short connecting wire, and also to the frame F 5  using a relatively longer connecting wire L 2 . 
   On the frame F 4 , mounted are a switching device S 1 , such as IGBT, and a flywheel diodes D 1 . The collector of the switching device S 1  and the cathode of the diode D 1  are electrically connected to the frame F 4 . The emitter of the switching device S 1  and the anode of the diode D 1  are connected to each other using a short connecting wire, and also to the frame F 5  using a relatively longer connecting wire L 1 . 
   In this embodiment, the additional frame F 7  is electrically connected to the frame F 2  using a branching wire J 2 . 
   Incidentally, for avoiding complexity of the drawing, illustration of the respective gate of the respective IGBT and the respective wire connected with each gate is omitted. 
   In this configuration, the switching devices S 6  and S 3  are series-connected between the frames F 1  and F 5 , which are fed with unipolar power, to control the phase-W of AC power. The switching devices S 5  and S 2  are series-connected to control the phase-V of AC power. The switching devices S 4  and S 1  are series-connected to control the phase-U of AC power. 
   In this embodiment, as shown in  FIG. 4 , an external snubber circuit SN 2  is connected between the terminal N of the frame F 5  and a terminal T 2  of the additional frame F 7 . Hence, the snubber circuit SN 2  resides in the closed loop circuit including the terminal T 2 , the frame F 7 , the branching wire J 2 , the switching device S 3  (diode D 3 ), the connecting wire L 3 , the frame F 5  and the terminal N. 
   Therefore, this embodiment can reduce wiring length and loop area of the closed loop circuit including the snubber circuit SN 2 , thereby improving the effect of the snubber circuit SN 2  for suppressing surge voltage. 
   Here, surge suppression of the phase-W of AC power has been described in detail. Likewise, in case of both the phase-U and the phase-V of AC power, respective additional frames are arranged close to the frame F 5 , and respective branching wires are connected between the respective frames and the frames F 3  and F 4 , and respective external snubber circuits are connected between each terminal of the respective frames and the terminal N of the frame F 5 , resulting in the same effect as in phase-W. 
   In the above description, discussed was the closed loop circuit of the snubber circuit SN 2  which was connected between the respective frames F 2  to F 4  for outputting AC power and the frame F 5  which is a negative line of unipolar power. Similarly, another closed loop circuit of a snubber circuit SN 1  which is connected between the respective frames F 2  to F 4  and the frame F 1  which is a positive line of unipolar power can be improved. 
   Embodiment 3 
     FIG. 5  is a plan view showing an example of an internal configuration of a power semiconductor module according to a third embodiment of the present invention.  FIG. 6  is a circuit diagram relevant to a phase-W circuit of the power semiconductor module of  FIG. 5 . Here, exemplified is a case of converting unipolar power, which is rectified from AC power, into three-phase AC power (phase-U, phase-V, phase-W). 
   The power semiconductor module M is provided with frames F 1  to F 5  made of electrically conductive material on an electrically insulating substrate, and an additional frame F 8  is arranged close to the frame F 1 . The frames F 1  and F 5  are fed with external unipolar power. For example, a terminal P of the frame F 1  is connected with a positive line of an AC power rectifying circuit, while a terminal N of the frame F 5  is connected with a negative line of the AC power rectifying circuit. 
   A terminal W of the frame F 2  outputs the phase-W of AC power to an external circuit. A terminal V of the frame F 3  outputs the phase-V of AC power to an external circuit. A terminal U of the frame F 4  outputs the phase-U of AC power to an external circuit. 
   On the frame F 1 , mounted are switching devices S 4  to S 6 , such as IGBT, and flywheel diodes D 4  to D 6 . The collectors of the switching devices S 4  to S 6  and the cathodes of the diodes D 4  to D 6  are electrically connected to the frame F 1 . 
   The emitter of the switching device S 4  and the anode of the diode D 4  are connected to each other using a short connecting wire, and also to the frame F 4  using a relatively longer connecting wire L 4 . Likewise, the emitter of the switching device S 5  and the anode of the diode D 5  are connected to each other using a short connecting wire, and also to the frame F 3  using a relatively longer connecting wire L 5 . Further, the emitter of the switching device S 6  and the anode of the diode D 6  are connected to each other using a short connecting wire, and also to the frame F 2  using a relatively longer connecting wire L 6 . 
   Meanwhile, on the frame F 2 , mounted are a switching device S 3 , such as IGBT, and a flywheel diodes D 3 . The collector of the switching device S 3  and the cathode of the diode D 3  are electrically connected to the frame F 2 . The emitter of the switching device S 3  and the anode of the diode D 3  are connected to each other using a short connecting wire, and also to the frame F 5  using a relatively longer connecting wire L 3 . 
   On the frame F 3 , mounted are a switching device S 2 , such as IGBT, and a flywheel diodes D 2 . The collector of the switching device S 2  and the cathode of the diode D 2  are electrically connected to the frame F 3 . The emitter of the switching device S 2  and the anode of the diode D 2  are connected to each other using a short connecting wire, and also to the frame F 5  using a relatively longer connecting wire L 2 . 
   On the frame F 4 , mounted are a switching device S 1 , such as IGBT, and a flywheel diodes D 1 . The collector of the switching device S 1  and the cathode of the diode D 1  are electrically connected to the frame F 4 . The emitter of the switching device S 1  and the anode of the diode D 1  are connected to each other using a short connecting wire, and also to the frame F 5  using a relatively longer connecting wire L 1 . 
   In this embodiment, the additional frame F 8  is electrically connected to the frame F 5  using a branching wire J 3 . 
   Incidentally, for avoiding complexity of the drawing, illustration of the respective gate of the respective IGBT and the respective wire connected with each gate is omitted. 
   In this configuration, the switching devices S 6  and S 3  are series-connected between the frames F 1  and F 5 , which are fed with unipolar power, to control the phase-W of AC power. The switching devices S 5  and S 2  are series-connected to control the phase-V of AC power. The switching devices S 4  and S 1  are series-connected to control the phase-U of AC power. 
   In this embodiment, as shown in  FIG. 6 , an external snubber circuit SN 3  is connected between the terminal P of the frame F 1  and a terminal T 3  of the additional frame F 8 . Hence, the snubber circuit SN 3  resides in the closed loop circuit including the terminal T 3 , the frame F 8 , the branching wire J 3 , the pair of switching devices, the frame F 1  and the terminal P. 
   In the conventional power semiconductor module, on the other hand, as shown in  FIGS. 7 and 8 , the snubber circuit SN 3  resides in the closed loop circuit including the terminal N, the frame F 5 , the pair of switching devices, the frame F 1  and the terminal P. 
   Therefore, this embodiment can reduce wiring length and loop area of the closed loop circuit including the snubber circuit SN 3 , thereby improving the effect of the snubber circuit SN 3  for suppressing surge voltage. 
   In the above description, discussed was the case where the additional frame F 8  was arranged close to the frame F 1  which was a positive line of unipolar power, and the snubber circuit SN 3  was connected therebetween. Similarly, the other case where an additional frame is arranged close to the frame F 5  which is a negative line of unipolar power, and the snubber circuit SN 3  is connected therebetween can be improved. 
   Although the present invention has been fully described in connection with the preferred embodiments thereof and the accompanying drawings, it is to be noted that various changes and modifications are apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.