JP2010200585A - Switching circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching circuit that suppresses a vibration phenomenon of current or voltage that is likely to occur in a circuit of a conventional power semiconductor device due to reverse recovery current generated by a reflux diode. <P>SOLUTION: The switching circuit includes a parallel circuit where a unipolar diode 101 and a bipolar diode 102 are connected in parallel in the same direction, and a switching element 103 connected in the parallel circuit. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

    The present invention relates to a switching circuit.

  2. Description of the Related Art A power semiconductor device is known in which a capacitor is connected in parallel to a free wheel diode to suppress an oscillation phenomenon of the free wheel diode (Patent Document 1).

JP 2004-281462 A

  However, in the conventional power semiconductor device, since the occurrence of the vibration phenomenon itself cannot be suppressed, there is a possibility of adversely affecting the peripheral circuits until the generated vibration phenomenon is attenuated.

  Therefore, the present invention provides a switching circuit that suppresses the occurrence of a vibration phenomenon.

The present invention solves the above problems by a switching circuit in which a unipolar diode and a bipolar diode are connected in parallel.

  According to the present invention, a switching element is connected to a parallel circuit of a unipolar diode and a bipolar diode, and a current is passed through the unipolar diode and the bipolar diode. And adverse effects on peripheral circuits can be suppressed.

It is a circuit diagram showing a drive circuit concerning an embodiment of the invention. It is a figure which shows the time-current characteristic of the unipolar diode and the switching element in the comparative example 1. 10 is a diagram illustrating time-current characteristics of a bipolar diode and a switching element in Comparative Example 2. FIG. It is a figure which shows the time-current characteristic of the parallel circuit and switching element of the unipolar diode of FIG. 1, and a bipolar diode. It is a figure which shows the voltage-current characteristic of the unipolar diode of FIG. 1, and a bipolar diode. It is a circuit diagram which shows the drive circuit which concerns on other embodiment of invention.

Hereinafter, embodiments of the invention will be described with reference to the drawings.
<< First Embodiment >>
FIG. 1 is a switching measurement circuit having an inductive load. Examples of the practical circuit having an inductive load include an inverter circuit connected to a motor and a DC / DC converter. The switching measurement circuit shown in FIG. 2 is for measuring the switching characteristics of semiconductor devices used in those practical circuits, and can reproduce the operation of the semiconductor devices and circuits in the practical circuits with a simple circuit. . FIG. 2 is a diagram for explaining current characteristics with respect to time of the unipolar diode and the switching element in the drive circuit of Comparative Example 1. FIG. 3 is a diagram with respect to time of the bipolar diode and the switching element in the drive circuit of Comparative Example 2. It is a figure for demonstrating an electric current characteristic. FIG. 4 is a diagram for explaining current characteristics with respect to time of a parallel circuit of a unipolar diode and a bipolar diode and a switching element in the drive circuit of this example.

  The driving circuit shown in FIG. 1 includes a unipolar diode 101, a bipolar diode 102 connected in parallel to the unipolar diode 101, a switching element 103 connected to the unipolar diode 101 and the bipolar diode 102, a load inductance 21, and a pulse generator 22. A DC power supply 24 that supplies current to the load inductance 21 by opening and closing the switching element 103, and a smoothing capacitor 25. The switching circuit 10 is formed by a unipolar diode 101, a bipolar diode 102, and a switching element 103.

  The unipolar diode 101 and the bipolar diode 102 are connected in parallel in the same direction, and the load inductance 21 is connected in parallel to a parallel circuit of the unipolar diode 101 and the bipolar diode 102. The switching element 103 of this example uses an IGBT, and the collector terminal of the switching element 103 is connected to the anode terminal of the unipolar diode 101 and the anode terminal of the bipolar diode 102. The gate terminal of the switching element 103 is connected to a pulse generator 22 for causing the switching element 103 to perform an ON / OFF operation. A resistor 23 between the switching element 103 and the pulse generator 22 is a gate resistor. A smoothing capacitor 25 is connected between the positive terminal and the negative terminal of the DC power supply 24. The positive terminal of the DC power supply 24 is connected to the cathode terminal of the unipolar diode 101 and the cathode terminal of the bipolar diode 102, and the negative terminal of the DC power supply 24 is connected to the emitter terminal of the switching element. A parasitic inductance 26 is provided between each element of the drive circuit shown in FIG.

  Next, the operation of the drive circuit of this example will be described. When a voltage is applied between the gate and emitter of the switching element 103 according to the signal of the pulse generator 22, the switching element 103 is turned on, and a current from the DC power supply 24 flows out to the switching circuit 10 and the load inductance 21. Here, since the unipolar diode 101 and the bipolar diode 102 are connected in the opposite direction to the current from the DC power supply 24, the current from the DC power 24 passes through the load inductance 21 and passes through the switching element 103. Flowing.

  When the switching element 103 changes from the ON state to the OFF state, the load inductance 21 keeps flowing current with the accumulated energy. At this time, since the switching element 103 is in an OFF state, the current does not flow between the collector and the emitter of the switching element 103, and flows out as a return current to the unipolar diode 101 and the bipolar diode 102, and the return current is unipolar diode. 101 and the bipolar diode 102 and the load inductance 21 flows in a closed circuit.

  Next, the operation of the switching circuit 10 when the switching element 103 is switched from the OFF state to the ON state while the return current is flowing is shown in FIG. 2 as Comparative Example 1, FIG. 3 as Comparative Example 2, and FIG. An example will be described with reference to FIG.

  The drive circuit of Comparative Example 1 is a drive circuit in the case where only the unipolar diode 101 is connected instead of the parallel circuit of the unipolar diode 101 and the bipolar diode 102 in the switching circuit 10 of this example shown in FIG. 2 shows the time-current characteristics of the unipolar diode 101 and the switching element 103 of the drive circuit of Comparative Example 1. FIG. 2A shows the current flowing through the unipolar diode 101, and FIG. 2B shows the current flowing through the switching element 103. Show.

  In the driving circuit of Comparative Example 1, when the switching element 103 is switched from the OFF state to the ON state in the state where the reflux current is flowing through the unipolar diode 101, the current from the DC power supply 24 flows out to the switching element 103 and flows into the unipolar diode 101. The reflux current that was flowing toward zero (time t1). In the process in which the reflux current is cut off from conduction, majority carriers in the unipolar diode 101 are discharged as charges according to the extension of the depletion layer (hereinafter referred to as reverse recovery charge). As a result, a reverse current flows through the unipolar diode 101 (hereinafter referred to as a reverse recovery current). The hatched portion (q) shown in FIG. 2 corresponds to the reverse recovery charge.

  Since the unipolar diode 101 forms reverse recovery charge only by majority carriers, the reverse recovery charge is less than that of the bipolar diode. However, since the reverse recovery charge of the unipolar diode 101 is discharged earlier than that of the bipolar diode, the blocking speed (dIr / dt) from the peak value (time t2) of the reverse recovery current to zero (time t3) is large. Become. A surge voltage (Lp × dIr / dt) is generated by the reverse recovery current cutoff speed and the inductance component (Lp) of the parasitic inductance 26 in the drive circuit. Thereby, the surge voltage is applied to the unipolar diode 101, and an excessive load is applied to the unipolar diode 101 in the drive circuit of Comparative Example 1.

  When the unipolar diode 101 is turned off, a depletion layer spreads in the drift layer of the unipolar diode 101 and a depletion capacitance is generated, so that the unipolar diode 101 operates as a capacitor. An LC resonance circuit is formed by the capacitor and the inductance component of the parasitic inductance 26, and LC resonance occurs. This LC resonance is the cause of current and voltage oscillation. This oscillation phenomenon of current and voltage becomes a source of noise and causes malfunction of peripheral circuits.

  The drive circuit of Comparative Example 2 is a drive circuit in the case where only the bipolar diode 102 is connected instead of the parallel circuit of the unipolar diode 101 and the bipolar diode 102 in the switching circuit 10 of this example shown in FIG. 3 shows the time-current characteristics of the bipolar diode 102 and the switching element 103 of the driving circuit of Comparative Example 2. (a) shows the current flowing through the bipolar diode 102, and (b) shows the current flowing through the switching element 103. Show.

  As in Comparative Example 1, when the switching element 103 changes from the OFF state to the ON state (time t1) while the return current flows through the bipolar diode 102, the return current goes to zero. In the bipolar diode, minority carriers are injected into the drift layer in the conductive state. Therefore, both minority carriers and majority carriers are discharged as reverse recovery charges in the process in which the reflux current is cut off from conduction.

  As described above, since the bipolar diode 102 forms reverse recovery charge with a small number of carriers and majority carriers, the reverse recovery charge is larger than the amount of reverse recovery charge formed with the unipolar diode 101 of Comparative Example 1. In FIG. 3, the part (q) shows the reverse recovery charge, but the part (q) in FIG. 3 is larger than the part (q) in FIG. As shown in FIG. 3B, the peak value of the reverse recovery current flowing through the switching element 103 is higher than that in the first comparative example, and a loss occurs in the switching element 103. Since the amount of reverse recovery charge discharged from the bipolar diode 102 increases when the current density of the return current flowing through the bipolar diode 102 is high, the loss also increases.

  On the other hand, since the cutoff speed (dIr / dt) from the peak value of the reverse recovery current (time t2) to zero (time t3) is slower than that of the unipolar diode 101 of Comparative Example 1, Such an oscillation phenomenon of current and voltage hardly occurs (see FIG. 2A).

As described above, in order to suppress the occurrence of the current / voltage oscillation phenomenon, it is important to relax the reverse recovery current cutoff speed dIr / dt, but the reverse recovery current is kept small while keeping the amount of reverse recovery charge small. It was difficult to relax the blocking rate dIr / dt.

  Since the drive circuit of this example has a parallel circuit of the unipolar diode 101 and the bipolar diode 102 in the same direction, the return current generated by switching the switching element 103 from the on state to the off state (time t1) is the unipolar diode 101. And the bipolar diode 102. When the switching element 103 is turned on and the unipolar diode 101 and the bipolar diode 102 are cut off, a reverse recovery current flows from the parallel circuit of the unipolar diode 101 and the bipolar diode 102. The reverse recovery charge is discharged from both the unipolar diode 101 and the bipolar diode 102. Therefore, by adjusting the ratio of the current flowing through the unipolar diode 101 and the bipolar diode 102, or by adjusting the chip area of the bipolar diode 102, Compared to the case of connecting only the bipolar diode 102 as in Comparative Example 2, the amount of reverse recovery charge can be reduced (see (q) in FIG. 4). Therefore, the reverse recovery current flowing through the switching element can also be suppressed (see (b) of FIG. 4).

  Further, since the reverse recovery charge discharged from the bipolar diode 102 having a low reverse recovery current cutoff speed is added to the reverse recovery charge discharged from the unipolar diode 101 having a high reverse recovery current cutoff speed, the parasitic inductance 26 is increased. The cutoff speed of the reverse recovery current that flows is limited by the bipolar diode 102 and becomes gentle as shown in FIG. As shown in FIG. 4, the peak value (time t2) of the reverse recovery current flowing in the parallel circuit of the switching element 103, the unipolar diode 101, and the bipolar diode 102 is suppressed, and in the process of reaching and decreasing the peak value, The recovery current gradually converges toward zero (time t3). Thereby, the drive circuit of this example can suppress the loss of each circuit element including the switching element 103 while suppressing the oscillation phenomenon of the current and voltage due to the interruption of the reverse recovery current.

  In this example, a soft recovery diode can be used instead of the bipolar diode. The soft recovery diode is a kind of bipolar diode, and the minority carrier lifetime in the drift layer is controlled so that the reverse recovery charge is gently cut off and the reverse recovery current cut-off rate is relaxed, so that dIr / dt is A relaxed current waveform is generated, the generation of surge voltage is small, and the occurrence of the oscillation phenomenon of current and voltage can be further suppressed.

  Next, in the switching circuit 10 of this example, the relationship between the rising voltage of the unipolar diode 101 and the bipolar diode 102 and the current flowing in the parallel circuit of the unipolar diode 101 and the bipolar diode 102 will be described with reference to FIG.

  5A to 5F, (I) shows the return current flowing in the parallel circuit of the unipolar diode 101 and the bipolar diode 102, (II) shows the return current flowing in the unipolar diode 101, and (III) shows the bipolar diode. The reflux current flowing through 102 is shown. Imax indicates the maximum current value flowing in the parallel circuit of the unipolar diode 101 and the bipolar diode 102, which is considered when designing the drive circuit of this example. The diode has a voltage at which a current suddenly rises when a certain forward voltage is applied. In this example, this voltage is called a rising voltage. When a forward voltage equal to or higher than the rising voltage is applied to the diode, the diode is referred to as a conductive state.

  There are various combinations of the relationship between the current-voltage characteristics of the unipolar diode 101 and the bipolar diode 102. If the relationship shown in FIGS. 5A to 5F is satisfied, the reverse recovery charge amount is kept small while maintaining the reverse recovery charge amount. The effect of relaxing the recovery current cutoff speed dIr / dt can be exhibited. What is common to FIGS. 5A to 5F is that the rising voltages of the unipolar diode 101 and the bipolar diode 102 are lower than the voltage drop value when the parallel circuit reaches the maximum current.

FIG. 5A shows an example in which the rising voltage of the unipolar diode 101 is set lower than the rising voltage of the bipolar diode 102. In the case of FIG. 5A, in the voltage region higher than the rising voltage of the bipolar diode 102, the reverse recovery current cut-off speed is reduced and the current / voltage oscillation phenomenon is suppressed while keeping the amount of reverse recovery charge small. Can do.

  5B is the same as the above-described FIG. 5A in that the rising voltage of the unipolar diode 101 is lower than the rising voltage of the bipolar diode 102, but the voltage-current characteristic of the bipolar diode 102 is not changed. The difference is that the slope is set larger than the slope of the voltage-current characteristic of the unipolar diode 101.

  As a result, when the return current flowing through the unipolar diode 101 and the bipolar diode 102 is large, a larger current flows through the bipolar diode 102 than the unipolar diode 101. Can suppress the oscillation phenomenon of current and voltage.

  FIGS. 5C and 5D are examples in which the rising voltage of the bipolar diode 102 is set to the same voltage as the rising voltage of the unipolar diode 101, and according to this, it is returned to the parallel circuit of the unipolar diode 101 and the bipolar diode 102. When a current flows, a reflux current flows through the unipolar diode 101 and the bipolar diode 102. Therefore, according to this example, the amount of reverse recovery charge can be reduced while suppressing the oscillation phenomenon of current and voltage due to the reverse recovery current in the entire region where the return current is equal to or less than the predetermined maximum current (Imax).

  In addition, in the switching circuit 10 of this example shown in FIG. 5C, when a large amount of return current flows, a larger amount of current flows toward the unipolar diode 101 than the bipolar diode 102, so that the amount of reverse recovery charge can be further suppressed. it can.

  Further, in the switching circuit 10 of this example shown in FIG. 5D, when a large amount of return current flows, a larger amount of current flows in the bipolar diode 102 than in the unipolar diode 101. Therefore, the effect of reducing the reverse recovery current cutoff speed is increased. Thus, the oscillation phenomenon of current and voltage can be further suppressed.

  FIG. 5E shows an example in which the rising voltage of the bipolar diode 102 is set lower than the rising voltage of the unipolar diode 101. With this, when a return current flows through the parallel circuit of the unipolar diode 101 and the bipolar diode 102, at least bipolar. A reflux current flows through the diode 102. Therefore, according to this example, the amount of reverse recovery charge can be reduced while suppressing the oscillation phenomenon of current and voltage in the entire region where the return current is equal to or less than the predetermined maximum current (Imax). In addition, when the return current is large, according to this example, since the return current flows more to the unipolar diode 101, the amount of reverse recovery charge can be further suppressed and the reverse recovery current can be suppressed.

  Further, by setting the rising voltage of the bipolar diode 102 so that the bipolar diode 102 is in a high injection state at the time when the voltage of the unipolar diode 101 rises, the reverse recovery current cut-off speed is further reduced, and the current, Voltage oscillation can be suppressed. Bipolar diodes, particularly soft recovery diodes, relax the reverse recovery current cutoff rate by injecting minority carriers into the drift layer at a high concentration. Therefore, when the current density reaches a certain level and the minority carriers are in a high injection state, the reverse recovery current cutoff rate can be more effectively relaxed, and the current / voltage oscillation phenomenon can be suppressed. The high injection state here means that the minority carrier concentration in the drift layer becomes equal to or higher than the impurity concentration of the drift layer.

  FIG. 5F is the same as the above-described FIG. 5E in that the rising voltage of the bipolar diode 102 is lower than the rising voltage of the unipolar diode 101, but the voltage-current characteristic of the bipolar diode 102 is not changed. The difference is that the slope is set larger than the slope of the voltage-current characteristic of the unipolar diode 101.

  Thereby, when the return current flowing through the unipolar diode 101 and the bipolar diode 102 is large, a larger current flows in the bipolar diode 102 than in the unipolar diode 101. Therefore, the cutoff speed of the reverse recovery current can be relaxed by the bipolar diode 102. The switching circuit 10 of the present example can further suppress current and voltage oscillation phenomena.

  Each of the characteristics shown in FIGS. 5A to 5F is appropriately selected according to the inductance characteristics of the drive circuit and measurement circuit in which the switching circuit 10 of this example is incorporated, the magnitude of the return current, and the like. It is incorporated in the switching circuit 10.

When the bipolar diode 102 is a PN diode, the rising voltage of the PN diode depends on the band gap. Therefore, by setting the semiconductor material forming the bipolar diode 102 to a material having a narrower band gap than the semiconductor material forming the unipolar diode 101, the rising voltage of the bipolar diode 102 is set lower than the rising voltage of the unipolar diode 101. I can do it. Thus, by setting the rising voltage of the bipolar diode 102 to be lower than the rising voltage of the unipolar diode 101, the reverse recovery current cutoff speed is reduced while the amount of reverse recovery charge is kept small in the entire current region, and the current・ Voltage oscillation phenomenon can be suppressed. The unipolar diode 101 of the switching circuit 10 of this example can be formed by a Schottky diode in which a metal is bonded to a base material of silicon carbide, gallium nitride, or diamond. These base materials have a wider band gap than normally used silicon, and can provide a switching circuit with higher breakdown voltage and lower loss.

  Moreover, the unipolar diode 101 of this example may be formed by a heterojunction diode in which a hetero semiconductor having a narrower band gap than that of a base material of silicon carbide, gallium nitride, or diamond is joined. These substrates can provide a switching circuit having a wider band gap, higher breakdown voltage, and lower loss than normally used silicon. In addition, since the heterojunction diode can control the rising voltage of the unipolar diode 101 by controlling the type of the hetero semiconductor material and the impurity concentration in the hetero semiconductor, the rising voltage of the unipolar diode 101 is set to the bipolar diode 102. It can be set higher than the rising voltage. As a result, the switching circuit 10 of this example can reduce the reverse recovery current cut-off speed and suppress the current / voltage oscillation phenomenon while keeping the amount of reverse recovery charge small in the entire current region.

  Note that single crystal silicon, polycrystalline silicon, amorphous silicon, germanium, silicon germanium, gallium arsenide, or the like may be used as a hetero semiconductor of the heterojunction diode.

  The bipolar diode 102 of this example is formed of a PN diode of silicon, silicon germanium, or germanium. Since these materials have a narrow band gap compared to materials such as silicon carbide, gallium nitride, and diamond, the rising voltage of the bipolar diode 102 can be further reduced. As a result, the switching circuit 10 of this example can reduce the reverse recovery current cut-off speed and suppress the current / voltage oscillation phenomenon while keeping the amount of reverse recovery charge small in the entire current region.

<< Second Embodiment >>
FIG. 6 is a drive circuit according to another embodiment of the invention. In this example, a three-phase inverter circuit is formed as a drive circuit using the switching circuits 10 to 60 of this example with respect to the first embodiment described above.

  The three-phase inverter circuit shown in FIG. 6 includes an upper and lower arm circuit in which the switching circuit 10 and the switching circuit 20 of this example are connected in series, an upper and lower arm circuit in which the switching circuit 30 and the switching circuit 40 are connected in series, a switching circuit 50 and a switching circuit. An upper and lower arm circuit in which a circuit 60 is connected in series, a DC power supply 24, a three-phase synchronous motor 27, a smoothing capacitor 25, and a relay switch 28 are provided. In the switching circuit 10, the anode terminal of the unipolar diode 101 and the anode terminal of the bipolar diode 102 are connected to the drain terminal of the switching element 203, whereas the switching circuit 20 is connected to the source terminal of the switching element 103. The basic operation is the same although the cathode terminal of the diode 201 and the cathode terminal of the bipolar diode 202 are connected. The same applies to the switching elements 30 to 60.

The three upper and lower arm circuits are connected in parallel, and the three parallel upper and lower arm circuits and the smoothing capacitor 25 are connected between the positive terminal and the negative terminal of the DC power supply 24 via a relay switch 28, and a three-phase synchronous motor. Twenty-five three-phase terminals are respectively connected to intermediate connection points of the upper and lower arm circuits arranged in parallel. As a result, the switching circuits 10 to 60 in this example form a PWM (Pulse Width Modulation) circuit and output a PWM signal to the three-phase synchronous motor 27. Note that the three-phase synchronous motor 27 of this example corresponds to the load inductance of the present invention.

  The switching elements 103 and 203 (the same applies to the other switching circuits 30 to 60) are formed of MOSFETs containing silicon, germanium, or silicon germanium, and parasitic PN diodes incorporated in the MOSFETs are used for the bipolar diodes 102 and 202. is doing. Unipolar diodes 101 and 201 are connected in parallel to switching elements 103 and 203, respectively, and are connected in the same direction as bipolar diodes 102 and 202, which are parasitic diodes of switching elements 103 and 203, respectively.

  In the drive circuit of this example, when the switching elements of the switching circuit 40 and the switching circuit 10 are turned on, current flows from the DC power supply 24 in the VU phase. Next, when the switching element 203 of the switching circuit 10 is turned off, a reflux current flows through the unipolar diode 101 and the bipolar diode 102 due to the inductance component of the three-phase motor 27. When the unipolar diode 101 and the bipolar diode 102 are cut off from energization, a reverse recovery current is generated. However, since the switching circuits 10 to 60 of this example include a parallel circuit of the unipolar diode 101 and the bipolar diode 102, The oscillation phenomenon of current and voltage due to the reverse recovery current can be suppressed, the amount of reverse recovery charge can be reduced, and the loss to the circuit element can be reduced.

  In the switching circuits 10 to 60 of this example, since the parasitic diode of the switching element is a bipolar diode, there is no need to provide a separate bipolar diode, the diode chip can be reduced, and the cost and size can be reduced. it can.

  In the driving circuit of this example, the unipolar diode 101 can be formed by a plurality of chips, and the bipolar diode 102 can be arranged between the plurality of unipolar diode chips. Since the unipolar diode 101 and the bipolar diode 102 have different current-voltage characteristics and the amount of reverse recovery charge, there is a difference in heat generation. With such an arrangement, the heat distribution of the drive circuit can be made more uniform, and a drive circuit with higher reliability can be provided.

10, 20, 30, 40, 50, 60 ... switching circuit 101, 201 ... unipolar diode 102, 202 ... bipolar diode 103, 203 ... switching element 21 ... load inductance 22 ... pulse generator 23 ... gate resistor 24 ... DC power supply 25 ... smoothing capacitor 26 ... parasitic inductance 27 ... three-phase motor 28 ... relay switch

Claims (12)

A parallel circuit in which a unipolar diode and a bipolar diode are connected in parallel in the same direction;
A switching circuit comprising a switching element connected to the parallel circuit. The switching circuit according to claim 1, wherein a return current generated when the switching element is switched from on to off flows in the parallel circuit to bring the unipolar diode and the bipolar diode into a conductive state. 3. The switching circuit according to claim 1, wherein a rising voltage of the bipolar diode is equal to or lower than a rising voltage of the unipolar diode. When the unipolar diode and the bipolar diode are conductive,
The switching circuit according to claim 1, wherein a current flowing through the unipolar diode is larger than a current flowing through the bipolar diode. The switching circuit according to claim 1, wherein the bipolar diode is a soft recovery diode. The semiconductor material forming the bipolar diode is:
The switching circuit according to claim 1, wherein a band gap is narrower than a semiconductor material forming the unipolar diode. The switching circuit according to claim 1, wherein the unipolar diode is a Schottky diode in which a metal is bonded to a silicon carbide or gallium nitride base material. The said unipolar diode is a heterojunction diode which heterojunction the semiconductor whose band gap is narrower than the said base material to the base material of a silicon carbide or a gallium nitride, It is characterized by the above-mentioned. Switching circuit. The switching circuit according to claim 7, wherein the bipolar diode is a PN diode including silicon, silicon germanium, or a germanium material. 9. The switching circuit according to claim 1, wherein the bipolar diode is a parasitic PN diode built in silicon or a silicon germanium or germanium MOSFET. A parallel circuit in which a first diode in which majority carriers have reverse recovery charges and a diode in which both majority carriers and decimal carriers have reverse charges are connected in parallel in the same direction;
A switching circuit comprising a switching element connected to the parallel circuit. The switching circuit according to any one of claims 1 to 11,
In a drive circuit comprising a load inductance connected to the switching circuit,
When the switching circuit is turned on, a direct current flows through the load inductance,
When the switching circuit is turned off, the parallel circuit conducts to form a closed circuit with the load inductance.

Images