Patent Publication Number: US-2023148137-A1

Title: Semiconductor Device, Power Module, Inverter Device, and Electric Vehicle

Description:
TECHNICAL FIELD 
     The present invention relates to a semiconductor device, a power module, an inverter device, and an electric vehicle. 
     BACKGROUND ART 
     An inverter device mounted on an electric vehicle such as a hybrid automobile or an electric automobile uses a switching element that is on-off controlled. This switching element is desired to achieve both shortening of switching time and suppression of surge voltage. Therefore, a surge voltage protection circuit is provided between a positive electrode side terminal of the switching element and a control terminal of the switching element. The surge voltage protection circuit is set to operate at a voltage (clamp voltage) lower than a breakdown voltage between a drain and a source of the switching element, and when a surge occurs, the surge voltage protection circuit breaks down before the switching element to protect the switching element. 
     PTL 1 discloses a load control device in which a cathode of a Zener diode Z1 is connected to a drain of a MOSFET, an anode of the diode is connected to an anode of the Zener diode Z1, a thermistor is connected between a cathode of the diode and a gate of the MOSFET, and a fixed resistor is connected to the thermistor in parallel. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP 2019-47416 A 
     SUMMARY OF INVENTION 
     Technical Problem 
     The device described in PTL 1 has a problem that, when the value of the current flowing through the thermistor increases, the voltage drop generated in the thermistor increases, and variations occur in the clamp voltage. 
     Solution to Problem 
     A semiconductor device according to the present invention includes: a switching element that is on-off controlled; and a surge voltage protection circuit connected between a positive electrode side terminal of the switching element and a control terminal of the switching element. The surge voltage protection circuit includes a first Zener diode, a second Zener diode connected in series with the first Zener diode, and a temperature characteristic compensating element having a temperature coefficient different in polarity from the first Zener diode and the second Zener diode and connected in parallel with the second Zener diode. 
     Advantageous Effects of Invention 
     According to the present invention, it is possible to suppress the variation in the clamp voltage regardless of the current value. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    is a circuit configuration diagram of a semiconductor device according to a first embodiment. 
         FIG.  2    is a diagram illustrating temperature characteristics of a clamp voltage according to the first embodiment. 
         FIG.  3    is a diagram illustrating a current characteristic of a clamp voltage according to the first embodiment. 
         FIG.  4    is a circuit configuration diagram of a semiconductor device according to a second embodiment. 
         FIG.  5    is a diagram illustrating temperature characteristics of a clamp voltage according to the second embodiment. 
         FIG.  6    is an external view illustrating a mounting structure of the semiconductor device. 
         FIG.  7    is a view illustrating an internal structure of the semiconductor device. 
         FIG.  8    is an external view of a power module incorporating the semiconductor device. 
         FIG.  9    is a view illustrating an internal structure of the power module. 
         FIG.  10    is a diagram illustrating a drive circuit of a motor using an inverter device. 
         FIG.  11    is a diagram illustrating a configuration of an electric vehicle. 
     
    
    
     Description of Embodiments 
     [First Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. However, the present invention should not be interpreted as being limited to the following embodiments, and the technical idea of the present invention may be realized by combining other known components. Note that, in the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. 
       FIG.  1    is a circuit configuration diagram of a semiconductor device  100  according to the present embodiment. 
     A switching element  110  is configured by a metal oxide film field effect transistor (MOSFET), a combination of an insulated gate bipolar transistor (IGBT) and a diode, or the like, and includes a positive electrode side terminal  11 , a negative electrode side terminal  12 , and a control terminal  13 . 
     The positive electrode side terminal  11  is connected to a positive electrode side of an inverter device (not shown), the negative electrode side terminal  12  is connected to a negative electrode side of the inverter device (not shown), and the control terminal  13  is connected to an inverter control device (not shown). In the switching element  110 , on/off of a current flowing from the positive electrode side terminal  11  to the negative electrode side terminal  12  is controlled based on a control signal input to the control terminal  13 . 
     A surge voltage protection circuit  10  is connected between the positive electrode side terminal  11  of the switching element  110  and the control terminal  13  of the switching element  110 . In general, the surge voltage protection circuit  10  is configured by connecting a diode  14  and a first Zener diode  15  in series. In this configuration, it is assumed that a surge voltage generated between the positive electrode side terminal  11  and the negative electrode side terminal  12  by the switching of the switching element  110  exceeds the clamp voltage set by a Zener voltage of the first Zener diode  15 . At this time, when the first Zener diode  15  is energized, a current flows from the positive electrode side terminal  11  to the control terminal  13 , and the potential of the control terminal  13  is raised to protect the switching element  110  from the surge voltage. 
     In the present embodiment, as illustrated in  FIG.  1   , the surge voltage protection circuit  10  includes a diode  14 , a first Zener diode  15 , a second Zener diode  16  connected in series with the first Zener diode  15 , and a temperature characteristic compensating element  17  having a temperature coefficient different in polarity from the first Zener diode  15  and the second Zener diode  16  and connected in parallel with the second Zener diode  16 . The temperature characteristic compensating element  17  is, for example, a thermistor. 
     When the polarity of the temperature coefficient of the temperature characteristic compensating element  17  is different from that of the second Zener diode  16  and the second Zener diode  16  has a positive temperature coefficient, the temperature characteristic compensating element  17  has a negative temperature coefficient. That is, when the element temperatures of the second Zener diode  16  and the temperature characteristic compensating element  17  increase, the Zener voltage of the second Zener diode  16  increases, but the resistance value of the temperature characteristic compensating element  17  decreases. On the other hand, when the element temperatures of the second Zener diode  16  and the temperature characteristic compensating element  17  decrease, the Zener voltage of the second Zener diode  16  decreases, but the resistance value of the temperature characteristic compensating element  17  increases. As a result, when the element temperatures of the second Zener diode  16  and the temperature characteristic compensating element  17  are high, the current flowing through the surge voltage protection circuit  10  flows more to the temperature characteristic compensating element  17 , and when the element temperatures of the second Zener diode  16  and the temperature characteristic compensating element  17  are low, the current flowing through the surge voltage protection circuit  10  flows more to the second Zener diode  16 . 
     Therefore, the clamp voltage when the element temperatures of the second Zener diode  16  and the temperature characteristic compensating element  17  are high is calculated by following Equation (1), and the clamp voltage when the element temperatures of the second Zener diode  16  and the temperature characteristic compensating element  17  are low is calculated by following Equation (2). 
         V clamp= Vf +VZD 1 +VNTC . . .   (1)
 
         V clamp= Vf +VZD 1 +VZD 2  . . .   (2)
 
     Here, Vclamp is a clamp voltage of the surge voltage protection circuit  10 , Vf is a forward voltage of the diode  14 , VZD 1  is a Zener voltage of the first Zener diode  15 , VNTC is a voltage drop generated in the temperature characteristic compensating element  17 , and VZD 2  is a Zener voltage of the second Zener diode  16 . 
       FIG.  2    is a diagram illustrating a temperature characteristic of a clamp voltage according to the first embodiment. In  FIG.  2   , the horizontal axis represents temperature, and the vertical axis represents voltage. 
     When the temperatures of the second Zener diode  16  and the temperature characteristic compensating element  17  are low (T 1  in  FIG.  2   ), since the Zener voltage VZD 2  of the second Zener diode  16  is low and the resistance value of the temperature characteristic compensating element  17  is large, the clamp voltage Vclamp is a sum of the Zener voltage VZD 1  of the first Zener diode  15  and the Zener voltage VZD 2  of the second Zener diode  16  as shown in Equation (2). 
     On the other hand, when the element temperatures of the second Zener diode  16  and the temperature characteristic compensating element  17  are high (T 2  in  FIG.  2   ), since the Zener voltage VZD 2  of the second Zener diode  16  is high and the resistance value of the temperature characteristic compensating element  17  is small, the clamp voltage Vclamp is a sum of the Zener voltage VZD 1  of the first Zener diode  15  and the voltage drop VNTC generated in the temperature characteristic compensating element  17  as shown in Equation (1). As a result, as compared with a general configuration using only the first Zener diode  15 , fluctuation of the clamp voltage due to temperature change is suppressed. 
       FIG.  3    is a diagram illustrating a current characteristic of a clamp voltage according to the first embodiment. In  FIG.  3   , the horizontal axis represents the current flowing through the surge voltage protection circuit  10 , and the vertical axis represents the voltage of the surge voltage protection circuit  10 . Vclamp is a clamp voltage of the surge voltage protection circuit  10 , Vf is a forward voltage of the diode  14 , VZD 1  is a Zener voltage of the first Zener diode  15 , VNTC is a voltage drop generated in the temperature characteristic compensating element  17 , and VZD 2  is a Zener voltage of the second Zener diode  16 . 
     When the element temperatures of the second Zener diode  16  and the temperature characteristic compensating element  17  are high, since the Zener voltage VZD 2  of the second Zener diode  16  is high and the resistance value of the temperature characteristic compensating element  17  is small, the current flowing through the surge voltage protection circuit  10  flows more to the temperature characteristic compensating element  17 . Then, when the current increases, the voltage drop VNTC generated in the temperature characteristic compensating element  17  increases, and when the second Zener diode  16  exceeds the Zener voltage VZD 2  at the current I 1 , the second Zener diode  16  is energized. As a result, it is possible to suppress an increase in the clamp voltage Vclamp when the current flowing through the surge voltage protection circuit  10  increases. 
     [Second Embodiment]  FIG.  4    is a circuit configuration diagram of a semiconductor device  100 ′ according to the second embodiment. The same portions as those of the first embodiment illustrated in  FIG.  1    are denoted by the same reference numerals, and the description thereof will be omitted. 
     In the second embodiment, a surge voltage protection circuit  20  is configured by series connection of a diode  14 , a first Zener diode  15 , a first clamp voltage compensation circuit unit  20   a , a second clamp voltage compensation circuit unit  20   b , . . . , and an n-th clamp voltage compensation circuit unit  20   n.    
     The first clamp voltage compensation circuit unit  20   a  is configured by parallel connection of the second Zener diode  16   a  and the temperature characteristic compensating element  17   a . The second clamp voltage compensation circuit unit  20   b  is configured by parallel connection of the third Zener diode  16   b  and the temperature characteristic compensating element  17   b . The n-th clamp voltage compensation circuit unit  20   n  is configured by parallel connection of an n-th Zener diode  16   n  and a temperature characteristic compensating element  17   n . The temperature characteristic compensating elements  17   a ,  17   b , . . . , and  17   n  have temperature coefficient polarities different from those of the first Zener diode  15 , the second Zener diode  16   a , and the n-th Zener diode  16   n.    
     In the second embodiment, the temperature at which the magnitude relationship between the Zener voltage VZD 2   a  of the second Zener diode  16   a  in the first clamp voltage compensation circuit unit  20   a  and the voltage drop VNTCa generated in the temperature characteristic compensating element  17   a  changes is different from the temperature at which the magnitude relationship between the Zener voltage VZD 2   b  of the third Zener diode  16   b  in the second clamp voltage compensation circuit unit  20   b  and the voltage drop VNTCb generated in the temperature characteristic compensating element  17   b  changes. 
       FIG.  5    is a diagram illustrating a temperature characteristic of a clamp voltage according to the second embodiment. In  FIG.  2   , the horizontal axis represents temperature, and the vertical axis represents voltage. 
     Hereinafter, in order to simplify the description, a case where the surge voltage protection circuit  20  is configured by series connection of the diode  14 , the first Zener diode  15 , the first clamp voltage compensation circuit unit  20   a , and the second clamp voltage compensation circuit unit  20   b  will be described as an example. 
     As illustrated in  FIG.  5   , when the component temperatures of the first to second clamp voltage compensation circuit units  20   a  to  20   b  are low at T 0  to T 1 , the voltage drop VNTCa generated in the temperature characteristic compensating element  17   a  is larger than the Zener voltage VZD 2   a  of the second Zener diode  16   a . In addition, the voltage drop VNTCb generated in the temperature characteristic compensating element  17   b  is larger than the Zener voltage VZD 2   b  of the third Zener diode  16   b . Therefore, the current flowing through the surge voltage protection circuit  20  flows through the second Zener diode  16   a  and the third Zener diode  16   b . Therefore, the clamp voltage Vclamp is the sum of the Zener voltage VZD 1  of the first Zener diode  15   a , the Zener voltage VZD 2   a  of the second Zener diode  16   a , and the Zener voltage VZD 2   b  of the third Zener diode  16   b , and is calculated by following Equation (3). 
         V clamp= Vf +VZD 1 +VZD 2   a +VZD 2   b  . . .   (3)
 
     When the component temperatures of the first to second clamp voltage compensation circuit units  20   a  to  20   b  increase to T 1  to T 2  as illustrated in  FIG.  5   , the voltage drop VNTCa generated in the temperature characteristic compensating element  17   a  is larger than the Zener voltage VZD 2   a  of the second Zener diode  16   a . In addition, the voltage drop VNTCb generated in the temperature characteristic compensating element  17   b  is smaller than the Zener voltage VZD 2   b  of the third Zener diode  16   b . Therefore, the current flowing through the surge voltage protection circuit  20  flows through the second Zener diode  16   a  and the temperature characteristic compensating element  17   b . Therefore, the clamp voltage Vclamp is the sum of the Zener voltage VZD 1  of the first Zener diode  15   a , the Zener voltage VZD 2   a  of the second Zener diode  16   a , and the voltage drop VNTCb generated in the temperature characteristic compensating element  17   b , and is calculated by following Equation (4). 
         V clamp= Vf +VZD 1 +VZD 2   a +VNTCb . . .   (4)
 
     As illustrated in  FIG.  5   , when the component temperatures of the first to second clamp voltage compensation circuit units  20   a  to  20   b  are high at T 2  to T 3 , the voltage drop VNTCa generated in the temperature characteristic compensating element  17   a  is smaller than the Zener voltage VZD 2   a  of the second Zener diode  16   a . In addition, the voltage drop VNTCb generated in the temperature characteristic compensating element  17   b  is smaller than the Zener voltage VZD 2   b  of the third Zener diode  16   b . Therefore, the current flowing through the surge voltage protection circuit  20  flows through the temperature characteristic compensating element  17   a  and the temperature characteristic compensating element  17   b . Therefore, the clamp voltage Vclamp is the sum of the Zener voltage VZD 1   a  of the first Zener diode  15   a , the voltage drop VNTCa generated in the temperature characteristic compensating element  17   a , and the voltage drop VNTCb generated in the temperature characteristic compensating element  17   b , and is calculated by following Equation (5). 
         V clamp= Vf +VZD 1 +VNTCa+VNTCb . . .   (5)
 
     As a result, the clamp voltage is switched a plurality of times when the component temperatures of the first to second clamp voltage compensation circuit units  20   a  to  20   b  change, so that fluctuation of the clamp voltage is further suppressed. Although the first to second clamp voltage compensation circuit units  20   a  to  20   b  have been described, the same applies to a case where a plurality of clamp voltage compensation circuit units are connected in series, and fluctuation of the clamp voltage can be further suppressed. 
       FIG.  6    is an external view illustrating a mounting structure of the semiconductor device  100 . This external view will be described by taking the external view of the semiconductor device  100  according to the first embodiment shown in  FIG.  1    as an example, but the same applies to the external view of the semiconductor device  100 ′ according to the second embodiment shown in  FIG.  4   . 
     A positive electrode side terminal conductor  11   a  is disposed on the lowermost surface of a substrate  30 , and is formed of a conductor having small electric resistance and small thermal resistance, such as copper or aluminum. A negative electrode side terminal conductor  12   a  is disposed on the uppermost surface of the substrate  30 , and is formed of a conductor such as copper or aluminum. 
       FIG.  7    is a view illustrating an internal structure of the semiconductor device  100 , and illustrates a state in which the negative electrode side terminal conductor  12   a  illustrated in  FIG.  6    is removed. 
     A positive electrode side terminal conductor insulating layer  11   b  is disposed on the upper surface of the positive electrode side terminal conductor  11   a , and the positive electrode side terminal conductor insulating layer  11   b  is formed of an insulating resin, ceramic, or the like. A control signal layer  13   a  and the like are disposed on the upper surface of the positive electrode side terminal conductor insulating layer  11   b , and this is formed of a conductor such as copper. In addition, the switching element  110  is disposed on the upper surface of the positive electrode side terminal conductor  11   a , and the positive electrode side terminal conductor  11   a  and the positive electrode side terminal  11  (see  FIG.  1   ) of the switching element  110  are joined by a positive electrode side terminal joining material  11   d  such as solder. On the other hand, a negative electrode side terminal  12  (see  FIG.  1   ) of the switching element  110  is joined to a negative electrode side terminal  12  (not shown) by a negative electrode side terminal joining material  12   d  such as solder. At this time, the maximum output current of the semiconductor element can be increased by connecting the switching elements  110  in multi-parallel. 
     The control terminal  13  (see  FIG.  1   ) of the switching element  110  is connected to the control signal layer  13   a  by a control signal line  13   d  such as a bonding wire, and the diode  14 , the first Zener diode  15 , the second Zener diode  16 , and the temperature characteristic compensating element  17  constituting the surge voltage protection circuit  10  are soldered to the control signal layer  13   a . That is, the switching element  110  and the surge voltage protection circuit  10  (diode  14 , first Zener diode  15 , second Zener diode  16 , and temperature characteristic compensating element  17 ) are formed on the same substrate. At this time, in the semiconductor device  100 , by arranging the first Zener diode  15 , the second Zener diode  16 , and the temperature characteristic compensating element  17  so as to be close to each other, it is possible to reduce a variation in temperature of each component, and it is possible to suppress a variation in electrical characteristics. 
       FIG.  8    is an external view of a power module  200  incorporating the semiconductor device  100 . 
     The signal lines from the internal semiconductor device  100  are collected as a lower arm control signal line  13   c  and an upper arm control signal line  13   b . The upper arm positive electrode side terminal  11   c , the lower arm negative electrode side terminal  12   c , and the upper surface of the upper arm negative electrode terminal/lower arm positive electrode terminal  18  are joined to a heat dissipation fin  22  by a joining material having low thermal resistance such as solder. The side surface is molded with a resin  21  to prevent mixing of foreign substances and improve the withstand voltage. 
       FIG.  9    is a view illustrating an internal structure of the power module  200 , and is a view illustrating a state in which the heat dissipation fin  22  and the resin  21  illustrated in  FIG.  8    are removed. 
       FIG.  9    illustrates an example in which two semiconductor devices  100 - 1  used as the upper arm and two semiconductor devices  100 - 2  used as the lower arm are provided. The positive electrode side terminal conductor  11   a  (see  FIG.  7   ) of the upper arm is connected to the upper arm positive electrode side terminal  11   c  by a joining material such as solder. The negative electrode side terminal of the upper arm (see  FIG.  1   ) and the positive electrode side terminal of the lower arm (see  FIG.  1   ) are connected to the upper arm negative electrode terminal/lower arm positive electrode terminal  18 . The negative electrode side terminal (see  FIG.  1   ) of the lower arm is connected to the lower arm negative electrode side terminal  12   c . In order to reduce the wiring inductance, the upper arm positive electrode side terminal  11   c  and the lower arm negative electrode side terminal  12   c  are arranged close to each other. The control terminals (see  FIG.  1   ) of the upper arm and the lower arm are connected to the upper arm control signal line  13   b  and the lower arm control signal line  13   c , respectively. 
     In the first and second embodiments, since the surge voltage protection circuit  10 ,  20  that suppresses the fluctuation of the clamp voltage can be arranged in the immediate vicinity of the switching element  110 , the wiring inductance of the surge voltage protection circuit  10 ,  20  can be reduced, and the response speed when clamping the surge voltage can be improved. In addition, since a control device such as a microcomputer is not required for the surge voltage protection circuit  10 ,  20  that suppresses the fluctuation of the clamp voltage, the surge voltage protection circuit can be downsized and can be mounted inside the semiconductor device  100 ,  100 ′ or the power module  200 . 
       FIG.  10    is a diagram illustrating a drive circuit of a motor  400  using an inverter device  300 . 
     The drive circuit includes an inverter device  300 , an inverter control device  320 , a motor  400 , a position sensor  410 , and a current sensor  420 . 
     The inverter control device  320  performs PWM control of the inverter device  300  on the basis of a torque command T* from the outside, three-phase currents iu, iv, and iw detected by the current sensor  420 , and a rotor position θ detected by the position sensor  410 . 
     The inverter device  300  includes semiconductor devices  100   a  to  100   f . Each of the semiconductor devices  100   a  to  100   f  is a semiconductor device  100  incorporating the switching element  110  and the surge voltage protection circuit  10  illustrated in  FIG.  1   . Alternatively, each of the semiconductor devices  100   a  to  100   f  is a semiconductor device  100 ′ incorporating the switching element  110  and the surge voltage protection circuit  20  illustrated in  FIG.  4   . 
     The semiconductor device  100   a  is disposed in a U-phase upper arm, the semiconductor device  100   b  is disposed in a U-phase lower arm, the semiconductor device  100   c  is disposed in a V-phase upper arm, the semiconductor device  100   d  is disposed in a V-phase lower arm, the semiconductor device  100   e  is disposed in a W-phase upper arm, and the semiconductor device  100   f  is disposed in a W-phase lower arm. 
     In the semiconductor devices  100   a  to  100   f , the switching element  110  is turned on or off based on the switching signal generated by the inverter control device  320 , and the DC voltage applied from the DC power supply is converted into the AC voltage. The converted AC voltage is applied to the stator of the motor  400  to generate a three-phase AC current. This three-phase AC current generates a rotating magnetic field in the motor  400 , and the rotor rotates. 
     The position sensor  410  detects the position of the rotor of the motor  400  and outputs the detected rotor position θ to the inverter control device  320 . The current sensor  420  detects a current flowing through the motor  400  and outputs the detected three-phase currents iu, iv, and iw to the inverter control device  320 . 
       FIG.  11    is a diagram illustrating a configuration of an electric vehicle. 
     In the electric vehicle illustrated in  FIG.  11   , the inverter device  300  is mounted on a vehicle body  700  of a hybrid electric automobile to drive the motor  400 . The inverter device  300  includes the semiconductor device  100  or the semiconductor device  100 ′ described in each of the first and second embodiments. 
     The inverter device  300  operates based on a switching signal output from the inverter control device  320 , and performs power conversion from DC power to AC power. The motor  400  is driven using AC power output from the inverter device  300 . As a result, the electric vehicle travels using the driving force of the motor  400 . Furthermore, the motor  400  operates not only as an electric motor that generates a rotational driving force but also as a generator that generates power by receiving the driving force. That is, the electric vehicle is a power train in which the motor  400  is applied as a motor/generator. 
     A front wheel axle  701  is rotatably supported on a front portion of the vehicle body  700 , and front wheels  702  and  703  are provided at both ends of the front wheel axle  701 . A rear wheel axle  704  is rotatably supported on a rear portion of the vehicle body  700 , and rear wheels  705  and  706  are provided at both ends of the rear wheel axle  704 . The front wheel axle  701  is provided with a differential gear  711  which is a power distribution mechanism, and distributes the rotational driving force transmitted from an engine  710  via a transmission  712  to the left and right front wheel axles  701 . 
     The output shaft of the engine  710  is mechanically coupled to the output shaft of the motor  400  directly or via the transmission  712 . As a result, the rotational driving force of the motor  400  can be transmitted to the engine  710 , and the rotational driving force of the engine  710  can be transmitted to the motor  400 . 
     In the motor  400 , the three-phase AC power controlled by the inverter device  300  is supplied to the stator coil of the stator, whereby the rotor rotates and generates a rotational driving force according to the three-phase AC power. That is, while the motor  400  is controlled by the inverter device  300  to operate as an electric motor, the electromotive force is induced in the stator coil of the stator by the rotation of the rotor by receiving the rotational driving force of the engine  710 , and the motor operates as a generator that generates three-phase AC power. 
     The inverter device  300  converts DC power supplied from a high-voltage battery  500 , which is a DC power supply of a high-voltage system (for example, 300 V), into three-phase AC power, and controls three-phase AC current flowing through the stator coil of the motor  400  according to the magnetic pole position of the rotor according to the operation command value. 
     The three-phase AC power generated by the motor  400  is converted into DC power by the inverter device  300  to charge the high-voltage battery  500 . The high-voltage battery  500  is electrically connected to a low-voltage battery  723  via a DC-DC converter  724 . The low-voltage battery  723  constitutes a DC power supply for a low-voltage system (for example, 12 V) of an automobile, and is used as a power supply for a starter  725  for initially starting (cold starting) the engine  710  and auxiliary machines such as a radio and a light. 
     When the electric vehicle is at vehicle stop such as waiting for a traffic light (idle stop mode), the engine  710  is stopped, and when the engine  710  is restarted (hot start) at the time of re-departure, the motor  400  is driven by the inverter device  300  to restart the engine  710 . However, when the amount of charge of the high-voltage battery  500  is insufficient or when the engine  710  is not sufficiently warmed, it is preferable to continue driving without stopping the engine  710  even in the idle stop mode. Further, during the idle stop mode, it is necessary to secure a drive source of auxiliary machines using the engine  710  as a drive source, such as a compressor of an air conditioner. In this case, the motor  400  may be driven instead of the engine  710  to serve as a drive source for auxiliary machines. 
     On the other hand, when the electric vehicle is in the acceleration mode or the high-load operation mode, the motor  400  is driven to assist the driving of the engine  710 . Conversely, when the high-voltage battery  500  is in the charging mode requiring charging, the engine  710  causes the motor  400  to generate power to charge the high-voltage battery  500 . Furthermore, at the time of braking or decelerating the electric vehicle, as the regeneration mode, the motor  400  may be caused to generate power by kinetic energy of the electric vehicle to charge the high-voltage battery  500 . 
     In the electric vehicle according to the present embodiment, the motor  400  that generates the driving force of the vehicle body  700  is controlled by the inverter device  300 , and the inverter device  300  is protected from the surge voltage by the surge voltage protection circuit  10 ,  20 . 
     Therefore, since the fluctuation of the clamp voltage Vclamp due to the temperature change of the surge voltage protection circuit  10 ,  20  is suppressed by the second Zener diode  16 , the temperature characteristic compensating element  17 , and the like, it is possible to reduce the margin of the clamp voltage with respect to the element withstand voltage of the switching element  110  when designing the surge voltage protection circuit  10 ,  20 . Therefore, the switching element  110  operates at a clamp voltage at which an appropriate margin is secured with respect to the element withstand voltage of the switching element  110  regardless of the component temperature of the surge voltage protection circuit  10 ,  20 , so that the switching time is shortened and the switching loss is reduced. 
     As a result, since the amount of heat generated in the inverter device  300  during traveling is reduced, the cooling mechanism can be downsized, and the inverter device  300  and the radiator can be downsized. Furthermore, since the loss generated in the inverter device  300  is reduced, the power consumption amount is reduced, and the fuel consumption of the electric vehicle is improved. 
     In addition, since the switching loss generated in the inverter device  300  is reduced, the maximum switching frequency can be increased without improving the cooling performance of the inverter device  300 . As a result, since the frequency of the voltage ripple generated in the DC voltage unit of the inverter device  300  is increased, the capacitance of the input voltage smoothing capacitor connected in parallel with the power input terminal of the inverter device  300  can be reduced and downsized. Furthermore, since the maximum output frequency of the inverter device  300  can be increased, the maximum rotation speed of the motor  400  can be increased. As a result, the motor  400  is downsized along with high-speed rotation, and the degree of freedom in mounting to the electric vehicle is increased, so that the space inside the vehicle can be expanded. 
     According to the embodiments described above, the following operational effects can be obtained. 
     (1) The semiconductor device  100 ,  100 ′ includes a switching element  110  that is on-off controlled, and a surge voltage protection circuit  10 ,  20  connected between a positive electrode side terminal of the switching element  110  and a control terminal of the switching element  110 . The surge voltage protection circuit  10 ,  20  includes a first Zener diode  15 , a second Zener diode  16  connected in series with the first Zener diode  15 , and a temperature characteristic compensating elements  17  having a temperature coefficient different in polarity from the first Zener diode  15 , and the second Zener diode  16 , and connected in parallel with the second Zener diode  16 . As a result, it is possible to suppress variation in the clamp voltage regardless of the current value. 
     The present invention is not limited to the above-mentioned embodiments, and other forms conceivable within the scope of the technical idea of the present invention are also included in the scope of the present invention as long as the characteristics of the present invention are not impaired. 
     REFERENCE SIGNS LIST 
     
         
           10 ,  20  surge voltage protection circuit 
           11  positive electrode side terminal 
           12  negative electrode side terminal 
           13  control terminal 
           14  diode 
           15  first Zener diode 
           16  second Zener diode 
           17  temperature characteristic compensating element 
           21  resin 
           22  heat dissipation fin 
           100 ,  100 ′ semiconductor device 
           100   a  U-phase upper arm semiconductor device 
           100   b  U-phase lower arm semiconductor device 
           100   c  V-phase upper arm semiconductor device 
           100   d  V-phase lower arm semiconductor device 
           100   e  W-phase upper arm semiconductor device 
           100   f  W-phase lower arm semiconductor device 
           110  switching element 
           300  inverter device 
           320  inverter control device 
           400  motor 
           410  position sensor 
           420  current sensor 
           700  vehicle body 
           701  front wheel axle 
           702 ,  703  front wheel 
           704  rear wheel axle 
           705 ,  706  rear wheel 
           710  engine 
           711  differential gear 
           712  transmission 
           723  low voltage battery 
           724  DC-DC converter 
           725  starter 
         VZD 1  Zener voltage of first Zener diode 
         VZD 2  Zener voltage of second Zener diode 
         VNTC voltage drop of temperature characteristic compensating element 
         Vclamp clamp voltage 
         i u  U-phase current detection value 
         i v  V-phase current detection value 
         i w  W-phase current detection value 
         T* torque command value 
         ω angular velocity 
         θ rotor position