JPWO2020245900A1 - Semiconductor device - Google Patents

Abstract

The semiconductor device includes a semiconductor switching element, a drive circuit for driving the semiconductor switching element, and a snubber circuit for suppressing a surge voltage generated when the semiconductor switching element is switched. The drive circuit is configured to switch the semiconductor switching element at a timing when a predetermined time elapses from the timing at which the semiconductor switching element is switched. The predetermined time is set based on the timing at which the voltage increases in the voltage vibration generated by the switching of the semiconductor switching element.

Description

The present invention relates to semiconductor devices.

Japanese Patent Application Laid-Open No. 2007-143336 (Patent Document 1) describes a semiconductor device including a semiconductor switching element, a drive circuit for driving the semiconductor switching element, and a snubber circuit for suppressing a surge voltage generated when the semiconductor switching element is switched. Is disclosed.

The semiconductor device further includes a voltage detection circuit that detects the voltage across the snubber circuit, and a phase detection circuit that detects the movement of the vibration component of the detection signal output by the voltage detection circuit. The phase detection circuit detects the phase of voltage vibration generated by switching from the detection signal output by the voltage detection circuit. The drive circuit is configured to control the timing of the switching operation of the semiconductor switching element so as to be superimposed in the phase opposite to the phase of the vibration component based on the output of the phase detection circuit.

JP-A-2007-143336

According to the semiconductor device described in Patent Document 1, the amplitude of voltage vibration generated after the switching operation can be attenuated. However, since it is necessary to provide a voltage detection circuit and a phase detection circuit in order to control the timing of the switching operation of the semiconductor switching element, there is a concern that the circuit configuration becomes complicated and the number of parts increases.

The present invention has been made to solve such a problem, and an object of the present invention is the timing of switching a semiconductor switching element so as to attenuate the voltage vibration generated by the switching of the semiconductor switching element with a simple configuration. Is to provide a semiconductor device capable of controlling.

The semiconductor device according to the present invention includes a semiconductor switching element, a drive circuit for driving the semiconductor switching element, and a snubber circuit for suppressing a surge voltage generated when the semiconductor switching element is switched. The drive circuit is configured to switch the semiconductor switching element at a timing when a predetermined time elapses from the timing at which the semiconductor switching element is switched. The predetermined time is set based on the timing at which the voltage increases in the voltage vibration generated by the switching of the semiconductor switching element.

According to the present invention, it is possible to provide a semiconductor device capable of controlling the timing of switching the semiconductor switching element so as to attenuate the voltage vibration generated by the switching of the semiconductor switching element with a simple configuration.

It is a figure which shows the structure of the semiconductor device which concerns on embodiment. It is a figure which shows the waveform of the voltage and the current when the switching element is turned off. It is a figure explaining the measurement procedure of the preferable timing to turn on a switching element. It is a figure which shows the waveform of the current and voltage when the switching element is turned on at the time t1 of FIG. It is a figure which shows the waveform of the current and voltage when the switching element is turned on at the time t2 of FIG. It is a figure which shows the waveform of the current and voltage when the switching element is turned on at the time t3 of FIG. It is a figure which shows the waveform of the current and voltage when the switching element is turned on at the time t4 of FIG. It is a figure which shows the waveform of the current and voltage when the switching element is turned on at the time t5 of FIG. It is a figure which shows the waveform of the current and voltage when the switching element is turned on at the time t6 of FIG. It is a figure which shows the waveform of the current and voltage when the switching element is turned on at the time t7 of FIG. It is a figure which shows the waveform of the voltage and the current when the voltage vibration is amplified after turning on a switching element. It is a figure which shows the waveform of the voltage and the current when the voltage vibration is attenuated after turning on a switching element.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following, the same or corresponding parts in the figure are designated by the same reference numerals, and the explanations will not be repeated in principle.

FIG. 1 is a diagram showing a configuration of a semiconductor device according to an embodiment.
With reference to FIG. 1, the semiconductor device includes semiconductor switching elements (hereinafter, also simply referred to as “switching elements”) Q1 and Q2, diodes D1 and D2, a drive circuit 12, and a snubber circuit 14. In FIG. 1, IGBTs (Insulated Gate Bipolar Transistors) are illustrated as semiconductor switching elements Q1 and Q2, but they are not necessarily limited to IGBTs, and any self-extinguishing such as MOSFET (Metal Oxide Field Effect Transistor). It may be an arc-shaped semiconductor switching element. The semiconductor device shown in FIG. 1 is applied to a power converter such as an inverter that converts DC power into AC power and a converter that converts AC power into DC power.

In the switching element Q1, the collector C1 is connected to the DC positive bus PL, and the emitter E1 is connected to the collector terminal C2 of the switching element Q2. The emitter E2 of the switching element Q2 is connected to the DC negative bus NL.

Diodes D1 and D1 and 2 are connected in antiparallel to each of the switching elements Q1 and Q2, respectively. Each of the diodes D1 and D2 is provided to allow a freewheel current to flow when the corresponding switching element is off. When the switching elements Q1 and Q2 are MOSFETs, the freewheel diode may be composed of a parasitic diode (body diode).

The series circuit 10 of the switching element Q1 and the switching element Q2 constitutes a half-bridge circuit. By connecting two series circuits 10 in parallel between the DC positive bus PL and the DC negative bus NL, a power converter having a full bridge circuit can be configured.

The series circuit 10 of the switching elements Q1 and Q2 has an input terminal T1 and T2 and an output terminal T3. The input terminal T1 is connected to the collector C1 of the switching element Q1 and the DC positive bus PL, and the input terminal T2 is connected to the emitter E2 of the switching element Q2 and the DC negative bus NL. The output terminal T3 is connected to the emitter E1 of the switching element Q1 and the collector C2 of the switching element Q2.

A capacitor 11 is connected between the input terminal T1 and the input terminal T2. The capacitor 11 corresponds to one embodiment of the "DC power supply".

The drive circuit 12 is connected to the gate terminals of the switching elements Q1 and Q2. The drive circuit 12 is configured to apply a voltage for switching the switching elements Q1 and Q2 to the gate terminal when receiving a control command from a control device of a power converter (not shown). Specifically, when the drive circuit 12 receives an ON command for the switching element Q1 from the control device, the drive circuit 12 transmits a voltage for transitioning (turning on) the switching element Q1 to the conduction state (ON state) to the gate terminal of the switching element Q1. Apply. The voltage for turning on is set to a voltage higher than the threshold voltage of the switching element Q1.

On the other hand, when the drive circuit 12 receives an off command of the switching element Q1 from the control device, the drive circuit 12 applies a voltage for transitioning (turning off) the switching element Q1 to the cutoff state (off state) to the gate terminal of the switching element Q1. The voltage for turning off is set to a voltage lower than the threshold voltage of the switching element Q1.

Similarly, when the drive circuit 12 receives an ON command for the switching element Q2 from the control device, the drive circuit 12 applies a voltage for turning on the switching element Q2 to the gate terminal of the switching element Q2. When the drive circuit 12 receives an off command for the switching element Q2 from the control device, the drive circuit 12 applies a voltage for turning off the switching element Q2 to the gate terminal of the switching element Q2. The drive circuit 12 is configured to drive the switching elements Q1 and Q2 in a complementary manner.

The snubber circuit 14 is connected between the input terminal T1 and the input terminal T2 of the series circuit 10. The snubber circuit 14 is provided to absorb the surge voltage generated during the switching operation of the switching elements Q1 and Q2. The snubber circuit 14 includes a capacitor 16. The capacitance of the capacitor 16 is determined according to the current flowing through the switching elements Q1 and Q2.

In the following description, the voltage between the collector C1 of the switching element Q1 and the emitter E2 of the switching element Q2 is defined as the voltage V1, and the voltage between the collector C2 and the emitter E2 of the switching element Q2 is defined as the voltage V2. The current flowing between the collector C1 and the emitter E1 of the switching element Q1 is defined as the current I1, the voltage between the terminals of the capacitor 16 of the snubber circuit 14 is defined as the voltage Vs, and the current flowing through the capacitor 16 is defined as the current Is.

Next, the operation of the semiconductor device shown in FIG. 1 will be described with reference to FIG.
FIG. 2 is a diagram showing waveforms of voltage V1 and current I1 when the switching element Q1 is turned off. The voltage V1 is equivalent to the voltage Vs between the terminals of the capacitor 16.

With reference to FIG. 2, when the switching element Q1 is turned off by the drive circuit 12 at time t0, the current I1 starts to decrease toward 0, while the voltage V1 starts to increase from the reference voltage. Immediately after the turn-off, a surge voltage is generated in the voltage V1. The higher the switching speed of the switching element Q1, the higher the surge voltage.

Here, in the semiconductor device shown in FIG. 1, since the wiring between the snubber circuit 14 and the switching elements Q1 and Q2 has a parasitic inductance 18 to 20, the capacitor 16 of the snubber circuit 14 and the parasitic inductance 18 to 20 exist. Due to the resonance with, the voltage V1 vibrates after the switching element Q1 is turned off. If the switching element Q1 is turned on by receiving an on command from the control device while the voltage vibration remains, the voltage vibration may be amplified depending on the turn-on timing. In this case, if the voltage applied between the collector and the emitter of the switching element exceeds the withstand voltage of the switching element, the switching elements Q1 and Q2 may be destroyed.

By turning on the switching element Q1 after waiting for the vibration of the voltage V1 to decay after the turn-off, the amplification of the voltage vibration described above can be suppressed, but the response of the semiconductor device (and the power converter). There is a concern that it may lead to a decrease in sex. In order to dispel such concerns, the semiconductor device described in Patent Document 1 sets the phase of the voltage detection circuit that detects the voltage across the snubber circuit and the vibration component of the detection signal output from the voltage detection circuit. It includes a phase detection circuit for detection, and is configured to control the timing of switching operation of the switching element based on the output of the phase detection circuit. In the above configuration, the drive circuit controls the timing of the switching operation of the switching element so that the voltage vibrations are superimposed in the opposite phase based on the output of the phase detection circuit.

However, in the semiconductor device described in Patent Document 1, since it is necessary to provide a voltage detection circuit and a phase detection circuit, there is a concern that the circuit configuration becomes complicated and the number of parts increases.

Therefore, in the present embodiment, a semiconductor device capable of controlling the timing of turning on the switching element Q1 so as to attenuate the voltage vibration generated at the time of turning off of the switching element Q1 is provided by a simpler configuration.

Hereinafter, the measurement results regarding the suitable timing for turning on the switching element Q1 will be described with reference to FIGS. 3 to 10.

In the measurement with reference to FIG. 3, in order to verify the relationship between the timing at which the switching element Q1 is turned on and the voltage vibration, a plurality of times t1 to be set as the timing at which the switching element Q1 is turned on after being turned off at the time t0. Set t7. The switching element Q2 is fixed in the off state.

Specifically, when the period of voltage vibration after turn-off is T, the time t1 is set so as to have a time difference corresponding to a 1/4 period (= 1/4 × T) from the time t0. NS. Regarding the period T of voltage vibration, the time t0 at which the voltage V1 starts to increase from the reference voltage is set to phase 0 °, and the timing at which the voltage V1 decreases to become the reference voltage is set to phase 180 ° (1/2 cycle). .. Further, the phase is set to 360 ° (1 cycle) when the voltage V1 changes from decreasing to increasing and becomes the reference voltage again. The period T of voltage vibration is determined by the capacitance of the capacitor 16 of the snubber circuit 14 and the parasitic inductances 18 to 20. That is, the period T of voltage vibration is a fixed value determined by the circuit configuration of the semiconductor device.

Times t2, t3, and t4 all have a time difference greater than 1/4 period (= 1/4 × T) and less than 3/4 period (= 3/4 × T) with time t0. Is set to. The time difference between the time t3 and the time t0 corresponds to 1/2 cycle (= 1/2 × T). The time difference between time t2 and time t0 is shorter than 1/2 cycle, and the time difference between time t4 and time t0 is longer than 1/2 cycle.

Times t5, t6, and t7 all have a time difference greater than 3/4 cycle (= 3/4 × T) and less than 5/4 cycle (= 5/4 × T) with time t0. Is set to. The time difference between the time t6 and the time t0 corresponds to one cycle (= T). The time difference between the time t5 and the time t0 is shorter than one cycle, and the time difference between the time t7 and the time t0 is longer than one cycle.

By measuring the waveforms of the current I1 and the voltages V2 and V3 when the switching element Q1 was turned on at the times t1 to t7 in FIG. 3, the change in the amplitude of the voltage fluctuation due to the turn-on timing was examined.

FIG. 4 is a diagram showing waveforms of the current I1 and the voltages V1 and V2 when the switching element Q1 is turned on at the time t1 of FIG. As shown in FIG. 4, when the switching element Q1 is turned on at time t1, a surge voltage is generated again at the voltage V1, and then voltage vibration occurs. The peak value of the voltage vibration that appears immediately after the turn-on changes depending on the turn-on timing, as shown below.

FIG. 5 is a diagram showing waveforms of current I1 and voltages V1 and V2 when the switching element Q1 is turned on at time t2 in FIG. As shown in FIG. 5, when the switching element Q1 is turned on at the time t2, the peak value of the voltage vibration appearing immediately after the time t1 becomes larger than the peak value of the voltage vibration appearing immediately after the time t0.

FIG. 6 is a diagram showing waveforms of current I1 and voltages V1 and V2 when the switching element Q1 is turned on at time t3 in FIG. As shown in FIG. 6, when the switching element Q1 is turned on at the time t3, the peak value of the voltage vibration appearing immediately after the time t2 becomes larger than the peak value of the voltage vibration appearing immediately after the time t0. In the case of FIG. 6, the peak value of the voltage signal appearing immediately after the turn-on is larger than that in FIG.

FIG. 7 is a diagram showing waveforms of the current I1 and the voltages V1 and V2 when the switching element Q1 is turned on at the time t4 of FIG. As shown in FIG. 7, when the switching element Q1 is turned on at the time t4, the peak value of the voltage vibration appearing immediately after the time t4 becomes larger than the peak value of the voltage vibration appearing immediately after the time t0.

According to FIGS. 5 to 7, when the switching element Q1 is turned on at time t2, t3, and t4, the peak value of the voltage vibration appearing after the turn-on becomes larger than the peak value of the voltage vibration appearing after the turn-off. According to this, when the switching element Q1 is turned on at a timing having a time difference larger than 1/4 cycle of the voltage vibration and less than 3/4 cycle with the time t0 when the switching element Q1 is turned off, the voltage vibration occurs. It can be seen that it amplifies.

FIG. 8 is a diagram showing waveforms of the current I1 and the voltages V1 and V2 when the switching element Q1 is turned on at the time t5 of FIG. As shown in FIG. 8, when the switching element Q1 is turned on at the time t5, the peak value of the voltage vibration appearing immediately after the time t5 becomes smaller than the peak value of the voltage vibration appearing immediately after the time t0.

FIG. 9 is a diagram showing waveforms of the current I1 and the voltages V1 and V2 when the switching element Q1 is turned on at the time t6 of FIG. As shown in FIG. 9, when the switching element Q1 is turned on at the time t6, the peak value of the voltage vibration appearing immediately after the time t6 becomes smaller than the peak value of the voltage vibration appearing immediately after the time t0. In the case of FIG. 9, the peak value of the voltage signal appearing immediately after the turn-on is smaller than that in FIG.

FIG. 10 is a diagram showing waveforms of current I1 and voltages V1 and V2 when the switching element Q1 is turned on at time t7 in FIG. As shown in FIG. 10, when the switching element Q1 is turned on at the time t7, the peak value of the voltage vibration appearing immediately after the time t7 becomes larger than the peak value of the voltage vibration appearing immediately after the time t0.

According to FIGS. 8 to 10, when the switching element Q1 is turned on at time t5, t6, t7, the peak value of the voltage vibration appearing after the turn-on is smaller than the peak value of the voltage vibration appearing after the turn-off. According to this, when the switching element Q1 is turned on at a timing having a time difference larger than the 3/4 cycle of the voltage vibration and less than the 5/4 cycle with the time t0 when the switching element Q1 is turned off, the voltage It can be seen that the vibration is dampened.

Although not shown, in the measurement result, there is a time difference corresponding to (1/4 + n) times larger than (1/4 + n) times the voltage vibration period T and less than (3/4 + n) times the time t0 when the voltage vibration is turned off. It was confirmed that the voltage vibration was amplified after the turn-on when the turn-on time was set so as to have the turn-on. However, n is an integer of 0 or more. On the other hand, the time for turning off is set so as to have a time difference corresponding to (3/4 + n) times larger than (3/4 + n) times the voltage vibration cycle T and less than (5/4 + n) times the turn-off time t0. In that case, it was confirmed that the voltage vibration was attenuated after the turn-on.

Returning to FIG. 3, the times t2, t3, and t4 all correspond to the timing at which the voltage V1 decreases from the positive peak value of the voltage vibration toward the negative peak value. On the other hand, the times t5, t6, and t7 all correspond to the timing at which the voltage V1 increases from the negative peak value of the voltage vibration toward the positive peak value. Therefore, the inventors of the present application have considered the relationship between the behavior (increase / decrease) of the voltage V1 at the timing of turning on the switching element Q1 and the amplification / attenuation of the voltage vibration. As a result, the following findings were obtained.

FIG. 11 is a diagram showing waveforms of voltage and current when voltage vibration is amplified after the switching element Q1 is turned on. 11 (A) shows the waveforms of the voltages V1 and V2, FIG. 11 (B) shows the waveform of the current I1, and FIG. 11 (C) shows the waveform of the current Is. The current Is has a positive direction in the direction of flowing into the capacitor 16 of the snubber circuit 14 and a negative direction in the direction of flowing out from the capacitor 16.

In FIGS. 11A to 11C, the time toff is the timing at which the switching element Q1 is turned off, and the time ton is the timing at which the switching element Q1 is turned on.

Focusing on FIG. 11C, when the switching element Q1 is turned off at the time to off, the current flowing through the switching element Q1 is commutated to the snubber circuit 14. Therefore, the current Is increases in the positive direction at time to off (see region R1 in the figure). On the other hand, when the switching element Q1 is turned on at the time ton, the current flowing in the snubber circuit 14 is commutated to the switching element Q1. Therefore, the current Is increases in the negative direction at the time ton. In FIG. 11C, since the current Is is negative at the time ton, the amplitude of the current Is is further increased by increasing the current Is in the negative direction due to the turn-on (see region R2 in the figure). .. As the amplitude of the current Is increases, the amplitude of the voltage Vs (≈voltage V1) also increases.

FIG. 12 is a diagram showing voltage and current waveforms when the voltage vibration is attenuated after the switching element Q1 is turned on. 12 (A) shows the waveforms of the voltages V1 and V2, FIG. 12 (B) shows the waveform of the current I1, and FIG. 12 (C) shows the waveform of the current Is. Similar to FIG. 11C, the current Is has a positive direction in the direction of flowing into the capacitor 16 of the snubber circuit 14 and a negative direction in the direction of flowing out from the capacitor 16. In FIGS. 12A to 12C, the time toff is the timing at which the switching element Q1 is turned off, and the time ton is the timing at which the switching element Q1 is turned on.

Focusing on FIG. 12C, when the switching element Q1 is turned off at the time to off, the current flowing through the switching element Q1 is commutated to the snubber circuit 14, so that the current Is increases in the positive direction (in the figure). See region R3).

On the other hand, when the switching element Q1 is turned on at the time ton, the current flowing in the snubber circuit 14 is commutated to the switching element Q1, so that the current Is increases in the negative direction. However, in FIG. 12C, since the current Is is positive at the time ton, the vibration of the current Is is canceled by the increase of the current Is in the negative direction due to the turn-on, and the amplitude of the current Is increases. Decays (see region R4 in the figure). As the amplitude of the current Is is attenuated, the amplitude of the voltage Vs (≈voltage V1) is also attenuated.

Here, since the snubber circuit 14 has the capacitor 16, the phase of the voltage V1 (≈voltage Vs) is delayed by about π / 2 with respect to the phase of the current Is. Therefore, at the timing when the voltage V1 increases from the negative peak value of the voltage vibration toward the positive peak value, the current Is shows a value close to the positive peak value. When the switching element Q1 is turned on at this timing, the amplitude of the current Is is attenuated as shown in FIG. 12C, so that the amplitude of the voltage V1 is attenuated, and as a result, the voltage vibration is attenuated.

As described above, the amplification of the voltage vibration can be attenuated by turning on the switching element at the timing when the voltage is increasing in the voltage vibration generated by the turn-off of the switching element. Similarly, regarding the timing of turning off the switching element, the voltage vibration can be attenuated by turning off the switching element at the timing when the voltage is increasing in the voltage vibration generated by the turn-on of the switching element.

The timing for turning on (or turning off) the switching element described above can be set by using the period of voltage vibration determined by the capacitance of the capacitor 16 of the snubber circuit 14 and the parasitic inductance of the wiring or the like. Therefore, the drive circuit 12 can be configured to turn on (or turn off) the switching element at a timing when a predetermined time elapses from the timing when the switching element is turned off (or turn on).

In the above configuration, the predetermined time can be set in advance using the period of voltage vibration. When the drive circuit 12 receives an on command (or off command) of the switching element from the control device, the drive circuit 12 turns on (or turns on) (or off) the switching element at a timing when the elapsed time from the timing at which the switching element was turned off immediately before reaches a predetermined time. Turn off).

According to this, the suitable switching timing capable of attenuating the voltage vibration is controlled without using the voltage detection circuit for detecting the voltage across the snubber circuit and the phase detection circuit for detecting the phase of the voltage vibration. can do. Therefore, it is possible to realize a semiconductor device capable of controlling the timing of switching the switching element so as to attenuate the voltage vibration generated when the switching element is switched with a simple configuration.

It should be considered that the embodiments disclosed this time are exemplary in all respects and not restrictive. The scope of the present invention is shown by the claims rather than the above description, and it is intended to include all modifications within the meaning and scope equivalent to the claims.

10 series circuit, 11,16 capacitor, 12 drive circuit, 14 snubber circuit, 18-20 parasitic inductance, Q1, Q2 switching element, D1, D2 diode

FIG. 10 is a diagram showing waveforms of current I1 and voltages V1 and V2 when the switching element Q1 is turned on at time t7 in FIG. As shown in FIG. 10, when the turns on the switching element Q1 at time t7, the peak value of the voltage oscillations appearing immediately after time t7 is smaller than the peak value of the voltage oscillations appearing immediately after time t0 Kunar.

Claims (4)

Semiconductor switching elements and
The drive circuit that drives the semiconductor switching element and
A snubber circuit that suppresses the surge voltage generated during switching of the semiconductor switching element is provided.
The drive circuit is configured to switch the semiconductor switching element at a timing when a predetermined time elapses from the timing at which the semiconductor switching element is switched.
The predetermined time is set based on the timing at which the voltage increases in the voltage vibration generated by the switching of the semiconductor switching element. The drive circuit is configured to turn on the semiconductor switching element at a timing when the predetermined time elapses from the timing at which the semiconductor switching element is turned off.
The predetermined time is set within a range (n is an integer of 0 or more) that is larger than (3/4 + n) times the period of voltage vibration generated by the switching and less than (5/4 + n) times. The semiconductor device according to 1. The drive circuit is configured to turn off the semiconductor switching element at a timing when the predetermined time elapses from the timing at which the semiconductor switching element is turned on.
The predetermined time is set within a range (n is an integer of 0 or more) that is larger than (3/4 + n) times the period of voltage vibration generated by the switching and less than (5/4 + n) times. The semiconductor device according to 1. The snubber circuit includes a capacitor connected in series with the semiconductor switching element.
The semiconductor device according to claim 2 or 3, wherein the period of the voltage vibration is calculated based on the capacity of the capacitor and the parasitic inductance of the semiconductor device.

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