JP2019213430A - Drive circuit - Google Patents

Abstract

To provide a drive circuit capable of appropriately protecting short circuit in switching elements connected in parallel.SOLUTION: A drive IC 10 constitutes one arm 5b of upper and lower arm circuits, and drives an IGBT6 and an MOSFET7, as multiple switching elements connected in parallel, and having mirror periods different from each other. The drive IC includes comparators 26, 36 for comparing a sense voltage each of the multiple switching elements with a threshold voltage for short circuit protection for determining occurrence of short circuit in another arm, and blockage parts 27, 37 for turning off a switching element satisfying such a condition that the state where the current exceeds a threshold continues even after the end of a prescribed filter period. The filter period is set according to a length of the mirror period, and the filter period is made shorter for the switching element having a shorter mirror period.SELECTED DRAWING: Figure 8

Description

  The disclosure in this specification relates to a drive circuit.

  Patent Document 1 discloses a drive circuit for switching elements connected in parallel. In Patent Document 1, a MOSFET and an IGBT are connected in parallel. The drive circuit changes the voltage applied to the gate electrode in accordance with the current flowing through the load. Thereby, only the MOSFET is turned on in the small current region, and both the MOSFET and the IGBT are turned on in the large current region.

Japanese Patent Laid-Open No. 2002-16486

  The switching elements connected in parallel constitute one arm of the upper and lower arm circuits. In the case of the upper and lower arm circuit, for example, when a short circuit occurs in the switching element of the upper arm, a large current flows in the lower arm at the timing when the switching element of the lower arm is turned on.

  However, the drive circuit disclosed in Patent Document 1 cannot properly protect the switching elements connected in parallel on the lower arm side, for example, when a short circuit occurs in the upper arm.

  The present disclosure has been made in view of such a problem, and an object thereof is to provide a drive circuit capable of appropriately short-circuiting switching elements connected in parallel.

  The present disclosure employs the following technical means to achieve the above object. In addition, the code | symbol in parenthesis shows the corresponding relationship with the specific means as described in embodiment mentioned later as one aspect | mode, Comprising: The technical scope is not limited.

One of the disclosures is a drive circuit that configures one arm (5b) of the upper and lower arm circuit (5a), drives a plurality of switching elements (6, 7) connected in parallel with different mirror periods. ,
A comparison unit (26, 36) that compares a current correlation value correlated with a current flowing through each of the plurality of switching elements and a threshold value for determining that a short circuit has occurred in the other arm constituting the upper and lower arm circuits. When,
On condition that the state where the current correlation value exceeds the threshold value continues even after the end of the predetermined filter period, a blocking unit (27, 37) that turns off the switching element that satisfies the condition;
With
The filter period is set according to the length of the mirror period, and the filter period is shortened as the switching element has a shorter mirror period.

  Since a switching element with a short filter period also has a short mirror period, during normal switching operation, the current correlation value falls below the threshold within the filter period. Therefore, even if the filter period is shortened, erroneous detection of a short circuit can be suppressed.

  In addition, since the switching period of the switching element having a short mirror period is shortened, it can be quickly turned off when a short circuit occurs in another arm. Thereby, in a state where a short-circuit abnormality has occurred in the other arm, the short-circuit energy from turning on to shut-off (off) can be reduced.

  As described above, the switching elements connected in parallel can be appropriately short-circuit protected.

It is a figure which shows schematic structure of the power converter device to which the drive IC of 1st Embodiment is applied. It is a figure which shows IV characteristic. It is a timing chart which shows the signal waveform of Si-IGBT at the time of turn-on. It is a timing chart which shows the signal waveform of SiC-MOSFET at the time of turn-on. It is a timing chart for explaining charge of a gate electrode and a mirror period. It is a figure for demonstrating charge of a gate electrode, and a mirror period. It is a figure which shows the reference example of an up-and-down arm circuit. It is a circuit diagram which shows the drive IC of 1st Embodiment. It is a timing chart which shows the signal waveform at the time of normal switching operation. It is a timing chart which shows a signal waveform at the time of short circuit protection operation. It is a schematic diagram which shows a short circuit energy and a short circuit tolerance. It is a circuit diagram which shows the drive IC of 2nd Embodiment. It is a circuit diagram which shows the drive IC of 3rd Embodiment. It is a circuit diagram which shows the drive IC of 4th Embodiment. It is a circuit diagram which shows the drive IC of 5th Embodiment.

  A plurality of embodiments will be described with reference to the drawings. In several embodiments, functionally and / or structurally corresponding parts are given the same reference numerals.

  (First embodiment)

(Schematic configuration of power converter)
A power conversion device 1 shown in FIG. 1 is mounted on, for example, an electric vehicle or a hybrid vehicle. The power conversion apparatus 1 is configured to convert a DC voltage supplied from a DC power supply 2 mounted on a vehicle into a three-phase AC and output it to a three-phase AC motor 3. The motor 3 functions as a vehicle driving source. The power conversion device 1 can also convert the power generated by the motor 3 into direct current and charge the direct current power source 2. Thus, the power conversion device 1 can perform bidirectional power conversion.

  The power converter 1 includes a smoothing capacitor 4 and an inverter 5 that is a power converter. The positive electrode side terminal of the smoothing capacitor 4 is connected to the positive electrode which is the high potential side electrode of the DC power source 2, and the negative electrode side terminal is connected to the negative electrode which is the low potential side electrode of the DC power source 2. The inverter 5 converts the input DC power into three-phase AC having a predetermined frequency and outputs it to the motor 3. The inverter 5 converts AC power generated by the motor 3 into DC power.

  The inverter 5 includes an upper and lower arm circuit 5a for three phases. The upper and lower arm circuits 5 a for each phase are formed by connecting two arms 5 b in series between the positive electrode side terminal and the negative electrode side terminal of the smoothing capacitor 4. The inverter 5 has six arms 5b.

  Each arm 5 b has an IGBT 6 and a MOSFET 7. The IGBT 6 and the MOSFET 7 are connected in parallel to each other. The IGBT 6 and the MOSFET 7 correspond to a plurality of switching elements connected in parallel. The IGBT 6 is formed on a silicon substrate. The IGBT 6 is connected in reverse parallel to the FWD 8 which is a reflux diode. In this embodiment, RC (Reverse Conducting) -IGBT in which FWD 8 is integrally formed is adopted as IGBT 6. Hereinafter, IGBT6 is also shown as Si-IGBT. The IGBT 6 corresponds to the first switching element.

  MOSFET 7 is formed on a silicon carbide substrate. Hereinafter, the MOSFET 7 is also referred to as a SiC-MOSFET. MOSFET 7 corresponds to a second switching element. In the present embodiment, as the IGBT 6 and the MOSFET 7, both n-channel types are adopted. The IGBT 6 has a collector electrode and an emitter electrode as main electrodes through which a main current flows. The MOSFET 7 has a drain electrode and a source electrode as main electrodes through which a main current flows.

  In the upper arm, which is the high-side arm 5 b, the collector electrode of the IGBT 6 and the drain electrode of the MOSFET 7 are connected to the positive terminal of the smoothing capacitor 4. In the lower arm, which is the low-side arm 5 b, the emitter electrode of the IGBT 6 and the source electrode of the MOSFET 7 are connected to the negative electrode side terminal of the smoothing capacitor 4. The collector electrode of the IGBT 6 and the drain electrode of the MOSFET 7 in the lower arm are connected to the emitter electrode of the IGBT 6 and the source electrode of the MOSFET 7 in the upper arm. In the upper and lower arm circuits 5 a for each phase, the connection point between the upper arm and the lower arm is connected to the coil (winding) of the corresponding phase of the motor 3.

  The power conversion device 1 further includes a control circuit 9 and a drive IC 10. The control circuit 9 generates a drive command for operating the switching element of the inverter 5 and outputs it to the drive IC 10. The control IC 9 generates a drive command based on, for example, a torque request input from a host ECU (not shown), a phase current detected by a current sensor (not shown), a rotation angle of a rotor detected by a rotation angle sensor (not shown), etc. To do. Specifically, a PWM signal is output as a drive command. The control IC 9 is configured with a microcomputer, for example.

  The drive IC 10 generates a drive signal based on a drive command from the control circuit 9. The drive IC 10 outputs the generated drive signal to the IGBT 6 and the MOSFET 7 of the corresponding arm 5b. The gate electrodes of the IGBT 6 and the MOSFET 7 constituting the same arm are electrically connected to the same drive IC 10.

  Thus, the drive IC 10 drives the IGBT 6 and the MOSFET 7 connected in parallel, that is, on-drive and off-drive. The drive IC 10 corresponds to a drive circuit. The drive IC 10 is also referred to as a driver. In the present embodiment, the drive IC 10 is provided individually for each arm constituting the inverter 5. In the present embodiment, the drive IC 10 is employed as the drive circuit, but is not limited to an IC (one chip).

(Characteristics of switching element)
FIG. 2 shows the IV characteristics of the switching element to be driven by the driving IC 10. In FIG. 2, the horizontal axis V represents the voltage between the main electrodes, and the vertical axis I represents the current flowing between the main electrodes, that is, the main current. The voltage V is the collector voltage Vce in the IGBT 6 and the drain voltage Vds in the MOSFET 7. The voltage V is also referred to as an on voltage. A broken line in FIG. 2 indicates an IV characteristic of the Si-IGBT. The solid line indicates the IV characteristics of the SiC-MOSFET.

  As shown in FIG. 2, in the small current region, the SiC-MOSFET has a lower voltage V than the Si-IGBT, and has better loss characteristics. On the other hand, in the large current region, the Si-IGBT has a lower voltage V than the SiC-MOSFET and has better loss characteristics. In the present embodiment, the control circuit 9 and the drive IC 10 operate the inverter 5 so that only the SiC-MOSFET is turned on in the small current region and both the SiC-MOSFET and the Si-IGBT are turned on in the large current region. Since the region having excellent loss characteristics of the switching elements connected in parallel is used, the loss can be reduced as a whole.

  FIG. 2 shows two levels of the SiC-MOSFET with different gate voltages Vgs. The gate voltage Vgs indicates a voltage between the gate electrode and the source electrode. High Vgs indicates a higher voltage than low Vgs. For example, the low Vgs is 10V and the high Vgs is 20V.

  The SiC-MOSFET has a characteristic that the saturation current increases as the gate voltage Vgs increases. For this reason, if the gate voltage Vgs to apply is made high, a main current can be sent by SiC-MOSFET to a higher electric current range. That is, the range of the loss reduction effect by the SiC-MOSFET can be expanded. The driving IC 10 according to the present embodiment drives the Si-IGBT and the SiC-MOSFET so as to exhibit IV characteristics as indicated by a one-dot chain line shown in FIG.

  FIG. 3 shows a signal waveform when the Si-IGBT is turned on. Vge represents a gate voltage between the gate electrode 6g and the emitter electrode 6e. Ice represents a collector current flowing between the collector electrode 6c and the emitter electrode 6e, and Vce represents a collector voltage between the collector electrode 6c and the emitter electrode 6e. Vse represents a sense voltage between the sense terminal 6st for current sensing and the emitter electrode 6e. The sense voltage Vse is a voltage proportional to the collector current Ice. This sense voltage Vse corresponds to a current correlation value.

  FIG. 4 shows a signal waveform when the SiC-MOSFET is turned on. Vgs represents a gate voltage between the gate electrode 7g and the source electrode 7s. Ids indicates a drain current flowing between the drain electrode 7d and the source electrode 7s, and Vds indicates a drain voltage between the drain electrode 7d and the source electrode 7s. Vse indicates a sense voltage between the sense terminal 7st for current sensing and the source electrode 7s. The sense voltage Vse is a voltage proportional to the drain current Ids. This sense voltage Vse also corresponds to a current correlation value.

  As shown in FIGS. 3 and 4, the IGBT 6 and the MOSFET 7 have current sensing sense terminals 6st and 7st, respectively, in order to protect themselves from an overcurrent caused by a short circuit of the other arm. The sense voltage Vse has a characteristic that the voltage rises at the start of turn-on rise. The sense voltage Vse rises when the recovery current is generated and during the mirror period. Thus, at least in the mirror period, the sense voltage Vse is raised.

  The mirror periods Tm1 and Tm2 are periods in which the gate voltages Vge and Vgs are flat. The mirror period Tm1 of the IGBT 6 is during charging of the gate electrode 6g, specifically, charging of the capacitance Cgc between the gate electrode 6g and the collector electrode 6c and charging of the capacitance Cce between the collector electrode 6c and the emitter electrode 6e. Occurs during. Note that the symbol Cge in FIG. 3 indicates the capacitance between the gate electrode 6g and the emitter electrode 6e.

  The mirror period T2 of the MOSFET 7 is during the charging of the gate electrode 7g, specifically, the capacitance Cgd between the gate electrode 7g and the drain electrode 7d, and between the drain electrode 7d and the source electrode 7s which are the main electrodes. Occurs during charging of the capacitance Cds. Note that the symbol Cgs in FIG. 4 indicates the capacitance between the gate electrode 7g and the source electrode 7s. Capacitances Cgc, Cce, Cgd, and Cds related to the mirror periods T1 and T2 are constituted by at least parasitic capacitances. In this embodiment, it is comprised only by the parasitic capacitance.

  The charging of the gate electrode and the mirror period will be described in detail with reference to FIGS. Here, the IGBT 6 will be described, but the same applies to the MOSFET 7. For example, the period Ta shown in FIG. 5 corresponds to FIG.

  A period Ta shown in FIG. 5 is a period before the start of driving. In the period Ta, as shown in FIG. 6A, the drive current (charging current) does not flow to the gate electrode 6g.

  A period Tb shown in FIG. 5 is a period immediately after the start of charging, and the IGBT 6 is in an off state. Although the gate voltage Vge is increased by the start of charging, the collector electrode 6c has a higher potential than the gate electrode 6g, so that only the capacitor Cge is charged as shown in FIG. The capacitance Cge, in other words, the capacitance between the gate electrode and the main electrode on the low potential side is also referred to as input capacitance.

  A period Tc shown in FIG. 5 is a period during which the IGBT 6 is turned on. Since the potential of the collector electrode 6c is lower than that of the gate electrode 6g by being turned on, the capacitor Cgc and the capacitor Cce are also charged as shown in FIG. Until the capacitors Cgc and Cce are charged with a charge corresponding to the gate threshold voltage, the voltage near the gate threshold is maintained. Therefore, the gate voltage Vge becomes flat in the period Tc. This period Tc corresponds to the mirror period Tm1. Note that the capacitance Cgc, in other words, the capacitance between the gate electrode and the main electrode on the high potential side is also referred to as feedback capacitance. The capacitance Cce, in other words, the capacitance between the main electrodes is also referred to as output capacitance.

  A period Td shown in FIG. 5 is a period from when the charge corresponding to the gate threshold voltage is charged until the output voltage of the driving IC 10 is reached. As shown in FIG. 6D, charging is continued and the gate voltage Vge increases.

  A period Te shown in FIG. 5 is a period in which charging is completed. When the charging is completed up to the output voltage of the driving IC 10, the driving current disappears as shown in FIG.

  Here, the mirror period is different for IGBTs and MOSFETs formed from the same substrate. Particularly in this embodiment, the chip area of the SiC substrate on which the MOSFET 7 is formed is made smaller than that on the Si substrate on which the IGBT 6 is formed in order to reduce costs. In general, when the chip size is reduced, the heat radiation area is reduced and heat generation becomes severer. However, since SiC has a higher thermal rating than Si, the chip size can be reduced.

  Thus, since the chip size of SiC is small, the parasitic capacitance of SiC is smaller than that of Si. For this reason, SiC takes less time to charge the capacity. Such characteristics of Si and SiC are largely reflected, and the mirror periods Tm1 and Tm2 of the SiC-MOSFET and the Si-IGBT are different. Specifically, the mirror period Tm2 of the SiC-MOSFET is shorter than the mirror period Tm1 of the Si-IGBT. Furthermore, the rising period of the sense voltage Vse on the MOSFET side including the mirror period Tm2 is shorter than the rising period of the sense voltage Vse on the IGBT side including the mirror period Tm1.

(Short circuit, short circuit energy, and short circuit tolerance)
The arm 5b in which the IGBT 6 and the MOSFET 7 are connected in parallel constitutes the upper and lower arm circuit 5a as described above. In the case of the upper and lower arm circuit 5a, when a short circuit occurs in the switching element of one arm 5b, a large current flows to the other one arm 5b at the ON timing.

  FIG. 7 shows a reference example of the upper and lower arm circuits. In FIG. 7, the MOSFET is not shown for convenience. In the reference example, r is given to the end of the reference numerals of the related elements in the present embodiment. FIG. 7 shows the signal waveform of the IGBT on the lower arm side.

  Among the upper and lower arm circuits 5ar, a short circuit has occurred in the upper arm at time t10. After the occurrence of a short circuit, the lower arm drive command is switched from OFF to ON at time t11. As a result, the gate voltage Vge rises and a large current flows as the collector current Ice. For example, the collector current Ice has a maximum current of about several hundreds A in a normal state, and flows several thousand A in a short circuit abnormality.

  On the lower arm side, for example, if a short circuit occurring in the upper arm cannot be detected, and thus the IGBT 6r cannot be forcibly turned off (cut off), a large current continues to flow as indicated by a one-dot chain line as the collector current Ice. That is, the short-circuit energy also increases as shown by the alternate long and short dash line. The short-circuit energy is obtained by integrating the product of the collector voltage Vce and the collector current Ice over time during the period from the start of driving in a state where a short circuit has occurred in the other arm 5br to the interruption. In the case of MOSFET, the product of drain voltage Vds and drain current Ids is integrated over time.

  When a large current continues to flow and the short-circuit energy exceeds the short-circuit tolerance of the lower arm IGBT 6r (Si-IGBT) at time t12, the lower arm IGBT 6r also fails. As described above, in the upper and lower arm circuit 5ar, when one arm 5br is short-circuited, there is a possibility that the other one arm 5br may be damaged together. As shown below, the drive IC 10 of this embodiment is configured to suppress accompanying failures.

(Drive IC details)
As shown in FIG. 8, the drive IC 10 of this embodiment has an IGBT drive unit 20 that drives the IGBT 6 (Si-IGBT) and a MOS drive unit 30 that drives the MOSFET 7 (SiC-MOSFET).

  The IGBT drive unit 20 includes an on drive unit 21 and an off drive unit 22 as a normal drive circuit that performs a normal switching operation. In the present embodiment, a p-channel type MOSFET is adopted as the on-drive unit 21, and an n-channel type MOSFET is adopted as the off-drive unit 22. The on driving unit 21 and the off driving unit 22 are connected in series between a power source and a ground (GND).

  A resistor 24 is provided between the connection point 23 of the on-drive unit 21 and the off-drive unit 22 and the on-drive unit 21, and a resistor 25 is provided between the connection point 23 and the off-drive unit 22. The drain electrode of the on drive unit 21 is connected to the gate electrode 6 g of the IGBT 6 through the resistor 24 and the connection point 23. The drain electrode of the off drive unit 22 is connected to the gate electrode 6 g of the IGBT 6 through the resistor 25 and the connection point 23.

  For example, when the drive command (PWM signal) is at the L level, the on drive unit 21 is turned on and the off drive unit 22 is turned off. Thereby, a driving current (charging current) flows from the power source to the gate electrode 6g, the gate electrode 6g is charged, and the IGBT 6 is turned on. On the other hand, when the drive command is at the H level, the on drive unit 21 is turned off and the off drive unit 22 is turned on. Thereby, the charge of the gate electrode 6g is drawn to the ground, and the IGBT 6 is turned off.

  The IGBT driving unit 20 further includes a comparator 26 and a blocking unit 27 as a short circuit protection circuit.

  The comparator 26 compares the sense voltage Vse detected by the sense terminal 6st of the IGBT 6 with the threshold voltage Vth for short-circuit protection, and outputs the comparison result to the cutoff unit 27. That is, the comparator 26 detects a short circuit abnormality that has occurred in the other arm 5b that constitutes the upper and lower arm circuit 5a. The comparator 26 corresponds to a comparison unit, and the threshold voltage Vth corresponds to a threshold value. For example, the comparator 26 outputs an H level signal when the sense voltage Vse is equal to or lower than the threshold voltage Vth, and outputs an L level signal when the sense voltage Vse exceeds the threshold voltage.

  The blocking unit 27 includes a filter 27a and a soft blocking unit 27b. The soft shut-off unit 27b forcibly turns off (cuts off) the IGBT 6 when the short circuit abnormality is determined. In the present embodiment, an n-channel type MOSFET is employed as the soft cutoff unit 27b.

  The filter 27a sets a predetermined filter period so that even if a short circuit abnormality is detected by the comparator 26, the IGBT 6 is not immediately turned off by the soft cutoff unit 27b. The filter 27a is constituted by a timer counter. In addition to the timer counter, an RC filter or the like can be employed.

  FIG. 9 shows signal waveforms during normal switching operation. FIG. 9 shows a signal waveform when the IGBT 6 is turned on. Even during the normal switching operation, the sense voltage Vse rises during the mirror period Tm1. The increase in the sense voltage Vse is a state indicating a voltage higher than the threshold voltage Vth.

  The filter 27a sets a predetermined filter period Tf1 in order to prevent erroneous detection of a short circuit during a normal switching operation due to an increase in the sense voltage Vse. The filter period Tf1 is a period from time t20 when the IGBT 6 is turned on to time t21. The filter period Tf1 is set longer than the lifting period including the mirror period Tm1. Although the sense voltage Vse exceeds the threshold voltage Vth immediately after the start of ON, the short circuit abnormality is not erroneously detected because it is within the filter period Tf1. If no short circuit abnormality has occurred, the sense voltage Vse becomes equal to or lower than the threshold voltage Vth when the filter period Tf1 ends. Therefore, the IGBT 6 can be normally driven.

  FIG. 10 shows a signal waveform when the short circuit is abnormal. FIG. 10 also shows the signal waveform of the IGBT 6. When the short circuit is abnormal, a large current flows as the collector current Ice. For this reason, the sense voltage Vse is higher than the threshold voltage Vth. If the sense voltage Vse exceeds the threshold voltage Vth at the end of the filter period Tf1, a short circuit abnormality is determined, and the soft cutoff unit 27b is turned on by the output of the filter 27a. If the state where the sense voltage Vse exceeds the threshold voltage Vth continues even after the end of the filter period Tf1, the filter 27a determines that a short-circuit abnormality has occurred and outputs an H level signal.

  When the soft shut-off portion 27b is turned on, the charge of the gate electrode 6g is drawn to the ground through the resistor 27c and the soft shut-off portion 27b, and the IGBT 6 is turned off. For example, since the resistance value of the resistor 27 c is higher than that of the resistor 25, the blocking speed by the soft blocking unit 27 b is slower than the blocking speed of the off drive unit 22. The surge voltage can be reduced by gradual interruption.

  The MOS drive unit 30 is configured in the same manner as the IGBT drive unit 20. The MOS drive unit 30 includes an on drive unit 31 and an off drive unit 32 as a normal drive circuit that performs a normal switching operation. In the present embodiment, a p-channel MOSFET is employed as the on-drive unit 31, and an n-channel MOSFET is employed as the off-drive unit 32. The on drive unit 31 and the off drive unit 32 are connected in series between the power supply and the ground.

  A resistor 34 is provided between the connection point 33 of the ON drive unit 31 and the OFF drive unit 32 and the ON drive unit 31, and a resistor 35 is provided between the connection point 33 and the OFF drive unit 32. The drain electrode of the on drive unit 31 is connected to the gate electrode 7 g of the MOSFET 7 through the resistor 34 and the connection point 33. The drain electrode of the off drive unit 32 is connected to the gate electrode 7 g of the MOSFET 7 through the resistor 35 and the connection point 33.

  For example, when the drive command (PWM signal) is at the L level, the on drive unit 31 is on and the off drive unit 32 is off. As a result, a drive current (charging current) flows from the power source to the gate electrode 7g, the gate electrode 7g is charged, and the MOSFET 7 is turned on. On the other hand, when the drive command is at the H level, the on drive unit 31 is turned off and the off drive unit 32 is turned on. As a result, the charge of the gate electrode 7g is extracted to the ground, and the MOSFET 7 is turned off.

  The MOS drive unit 30 further includes a comparator 36 and a blocking unit 37 as a short circuit protection circuit.

  The comparator 36 compares the sense voltage Vse detected by the sense terminal 7 st of the MOSFET 7 with the threshold voltage Vth for short-circuit protection, and outputs the comparison result to the cutoff unit 37. That is, the comparator 36 detects a short circuit abnormality that has occurred in the other arm 5b that constitutes the upper and lower arm circuit 5a. The comparator 36 corresponds to the comparison unit, and the threshold voltage Vth corresponds to the threshold value. For example, the comparator 36 outputs an H level signal when the sense voltage Vse is equal to or lower than the threshold voltage Vth, and outputs an L level signal when the sense voltage Vse exceeds the threshold voltage.

  The blocking unit 37 includes a filter 37a and a soft blocking unit 37b. The soft shut-off unit 37b forcibly turns off the MOSFET 6 when a short circuit abnormality is detected. In the present embodiment, an n-channel MOSFET is employed as the soft shut-off unit 37b.

  The filter 37a sets a predetermined filter period so that the MOSFET 7 is not immediately turned off by the soft cutoff unit 37b even if a short circuit abnormality is detected by the comparator 36. The filter 37a is constituted by a timer counter. In addition to the timer counter, an RC filter or the like can be employed.

  The filter 37a sets a filter period Tf2 (not shown) in order to prevent erroneous detection of a short circuit during a normal switching operation due to an increase in the sense voltage Vse. The filter period Tf2 is a predetermined period after the MOSFET 7 is turned on. The filter period Tf2 is set longer than the lifting period including the mirror period Tm2. Although the sense voltage Vse exceeds the threshold voltage Vth immediately after the start of ON, the short circuit abnormality is not erroneously detected because it is within the filter period Tf2. If no short circuit abnormality has occurred, the sense voltage Vse becomes equal to or lower than the threshold voltage Vth when the filter period Tf2 ends. Therefore, the MOSFET 7 can be normally driven.

  On the other hand, when a short circuit is abnormal, a large current flows as the drain current Ids. For this reason, the sense voltage Vse is higher than the threshold voltage Vth. If the state in which the sense voltage Vse exceeds the threshold voltage Vth continues after the end of the filter period Tf2, the filter 37a determines that a short-circuit abnormality has occurred and outputs an H level signal. Thereby, the soft interruption | blocking part 37b is turned ON.

  When the soft shut-off portion 37b is turned on, the charge of the gate electrode 7g is drawn to the ground via the resistor 37c and the soft shut-off portion 37b, and the MOSFET 7 is turned off. For example, since the resistance value of the resistor 37 c is higher than that of the resistor 35, the blocking speed by the soft blocking unit 37 b is slower than the blocking speed of the off drive unit 32. The surge voltage can be reduced by gradual interruption. The blocking portions 27 and 37 correspond to the blocking portion.

  In the present embodiment, the lengths of the mirror periods Tm1 and Tm2 are different between the IGBT 6 and the MOSFET 7 connected in parallel. The filter periods Tf1 and Tf2 are set according to the lengths of the mirror periods Tm1 and Tm2. Specifically, as shown in FIGS. 3 and 4, the filter period Tf2 on the MOSFET 7 side having the short mirror period Tm2 is shorter than the filter period Tf1 on the IGBT 6 side having the long mirror period Tm1. Thus, the shorter the mirror period, the shorter the filter period.

  Since the mirror period Tm2 of the MOSFET 7 is shorter than the mirror period Tm1 of the IGBT 6, even when the filter period Tf2 is shortened, the sense voltage Vse is equal to or lower than the threshold voltage Vth within the filter period Tf2 even during normal switching operation. Therefore, erroneous detection of a short circuit can be suppressed. On the other hand, for the IGBT 6 having the long mirror period Tm1, since the filter period Tf1 is longer than the filter period Tf2, it is possible to suppress erroneous detection of a short circuit.

  Further, by shortening the filter period Tf2, the MOSFET 7 in the short mirror period Tm2 can be quickly turned off when a short circuit occurs in the other arm 5b. Thereby, short circuit energy can be made small. Therefore, it is possible to suppress the short-circuit energy from exceeding the short-circuit tolerance and damaging the MOSFET 7.

  As described above, according to the drive IC 10 of this embodiment, the IGBT 6 and the MOSFET 7 connected in parallel can be appropriately short-circuit protected.

  In this embodiment, the filter period is shortened as the capacitance between the gate electrode and the main electrode on the high potential side and the capacitance between the main electrodes are smaller. Specifically, as shown in FIG. 8, the sum C2 of the capacitances Cgd and Cds of the MOSFET 7 is made smaller than the sum C1 of the capacitances Cgc and Cce of the IGBT 6. The filter period Tf2 is shorter than the filter period Tf1 because of the capacity C2 <capacitance C1. Since the mirror period is shorter as the capacitance of the switching element is smaller, the above-described effects can be achieved.

  In the present embodiment, the IGBT 6 is formed on the Si substrate, and the MOSFET 7 is formed on the SiC substrate. The filter period Tf2 of the SiC-MOSFET is shorter than the filter period Tf1 of the Si-IGBT. As described above, SiC has a smaller parasitic capacitance than Si, and thus takes less time to charge the capacitance. Therefore, even if the SiC-side filter period Tf2 is shortened, erroneous detection of a short circuit can be suppressed. On the other hand, on the Si side, since the filter period Tf1 is long, erroneous detection of a short circuit can be suppressed.

  Further, as shown in FIG. 11, the short-circuit tolerance is different between Si and SiC. For example, since the chip size of SiC is smaller than that of Si, SiC has a smaller short-circuit tolerance. The broken line position shown in FIG. 11 indicates the short circuit tolerance of Si and SiC. Since the SiC-side filter period Tf2 with a short-circuit withstand capability is shortened, the short-circuit energy can be reduced, thereby preventing the short-circuit withstand capability from being exceeded. Moreover, since Si has a short-circuit tolerance larger than that of SiC, even if the filter period Tf1 is lengthened, the short-circuit energy can be prevented from exceeding the short-circuit tolerance.

  In the present embodiment, an example in which the capacitances Cgd and Cds of the MOSFET 7 and the capacitances Cgc and Cce of the IGBT 6 are configured only by the parasitic capacitances is not limited to this. A capacitance connected between the electrodes by simulating a parasitic capacitance, for example, an external capacitance may be included.

  Although the example which provided the soft interruption | blocking part 27b separately from the OFF drive part 22 was shown, it can also be shared. For example, a drive command from the control circuit 9 and an output from the filter 27a may be input to the OR gate and output to the gate electrode of the common switching element. The same applies to the soft shut-off unit 37b and the off-drive unit 32.

(Second Embodiment)
This embodiment can refer to the preceding embodiment. For this reason, the description of the parts common to the drive circuit 10 shown in the previous embodiment is omitted.

  As shown in FIG. 12, in this embodiment, filter periods Tf1 and Tf2 are set according to drive currents I1 and I2 for charging the gate electrodes 6g and 7g. The larger the drive current, the faster the corresponding gate electrode is charged. That is, the larger the drive current, the shorter the mirror period.

  Specifically, the drive current I2 on the on drive unit 31 side is made larger than the drive current I1 on the on drive unit 21 side. The ON drive units 21 and 31 are supplied with substantially equal drive voltages (power supply voltages). The drive current I2 is made larger than the drive current I1 by making the resistance value R1 of the resistor 24 different from the resistance value R2 of the resistor 34, specifically, by making the resistance value R2 smaller than the resistance value R1. The filter period Tf2 on the MOSFET 7 side in which the drive current I2 flows is shorter than the filter period Tf1 on the IGBT 6 side in which the drive current I1 flows. Other configurations are the same as those of the preceding embodiment.

  Since the drive current I2 larger than the drive current I1 is supplied to the gate electrode 7g of the MOSFET 7, the mirror period Tm2 is shorter than the mirror period Tm1 of the IGBT 6. Therefore, even if the filter period Tf2 on the MOSFET 7 side is shortened, erroneous detection of a short circuit can be suppressed.

  Further, by shortening the filter period Tf2, the MOSFET 7 in the short mirror period Tm2 can be quickly turned off when a short circuit occurs in the other arm 5b. Thereby, short circuit energy can be made small. Therefore, it is possible to suppress the short-circuit energy from exceeding the short-circuit tolerance and damaging the MOSFET 7.

  The drive currents I1 and I2 may be varied depending on the drive voltage. Specifically, the drive current I2 may be made larger than the drive current I1 by making the drive voltage supplied to the ON drive unit 31 higher than the drive voltage supplied to the ON drive unit 21. The drive currents I1 and I2 may be made different depending on the combination of the drive voltage and the resistance value.

  The configuration shown in this embodiment may be combined with a configuration in which switching elements connected in parallel are the same, in other words, a configuration in which the capacitors C1 and C2 are substantially equal to each other.

(Third embodiment)
This embodiment can refer to the preceding embodiment. For this reason, the description of the parts common to the drive circuit 10 shown in the previous embodiment is omitted.

  In the present embodiment, the IGBT 6 is formed on the Si substrate, and the MOSFET 7 is formed on the SiC substrate. As described above, SiC has a smaller short-circuit tolerance than Si. The drive IC 10 is configured such that the SiC-MOSFET having a small short-circuit tolerance has a higher cutoff speed when a short-circuit abnormality is detected than the Si-IGBT having a large short-circuit tolerance. Other configurations are the same as those in the first embodiment.

  Specifically, as shown in FIG. 13, the resistance value R3 of the resistor 27c of the blocking unit 27 and the resistance value R4 of the resistor 37c of the blocking unit 37 are made different. By making resistance value R4 smaller than resistance value R3, the cutoff speed of SiC-MOSFET is made faster than Si-IGBT.

  The short circuit abnormality detection timing of the comparator 26 based on the sense voltage Vse of the Si-IGBT and the short circuit abnormality detection timing of the comparator 36 based on the sense voltage Vse of the SiC-MOSFET are substantially the same. Further, as described above, since the resistance value R4 is smaller than the resistance value R3, the gate electrode 7g is more likely to extract charges than the gate electrode 6g. Therefore, the SiC-MOSFET can be shut off first. Thus, the switching element with a small short circuit tolerance can be shut off first. Thereby, it is possible to prevent the main current from flowing from the Si-IGBT side having a large short-circuit tolerance to the SiC-MOSFET side having a small short-circuit tolerance, thereby reducing the short-circuit energy of the SiC-MOSFET.

  The configuration shown in the present embodiment is not limited to the combination with the configuration shown in the first embodiment. A combination with the configuration shown in the second embodiment is also possible.

(Fourth embodiment)
This embodiment can refer to the preceding embodiment. For this reason, the description of the parts common to the drive circuit 10 shown in the previous embodiment is omitted.

  In addition to the configuration shown in the first embodiment, the driving IC 10 according to the present embodiment turns off the switching element with a large short-circuit resistance when the current correlation value of the switching element with a small short-circuit resistance exceeds the threshold and becomes equal to or less than the threshold. It is configured as follows.

  Specifically, as shown in FIG. 14, the blocking unit 27 has an AND gate 27d. The output of the filter 27a and the output of the comparator 36 are input to the AND gate 27d. Then, the output of the AND gate 27d is input to the gate of the soft cutoff unit 27b.

  As described above, the comparators 26 and 36 output an H level signal when the sense voltage Vse is equal to or lower than the threshold voltage Vth, and output an L level signal when the sense voltage Vse exceeds the threshold voltage. If the state where the sense voltage Vse exceeds the threshold voltage continues even after the end of the filter period, the filters 27a and 37a determine that there is a short circuit abnormality and output an H level signal. The AND gate 27d outputs an H level signal when the outputs of the filter 27a and the comparator 36 are both at the H level. As a result, the MOSFET constituting the soft cutoff unit 27b is turned on, and the Si-IGBT is shut off (off).

  Thus, in this embodiment, after the sense voltage Vse of the SiC-MOSFET having a small short-circuit resistance exceeds the threshold voltage Vth after the threshold voltage Vth is reached, that is, after the detection of the short-circuit abnormality by the comparator 36 is canceled, The blocking of the Si-IGBT having a large tolerance is started. Therefore, the SiC-MOSFET can be shut off more reliably than the configuration shown in the third embodiment. Thereby, the short-circuit energy of the SiC-MOSFET can be further reduced.

  In the present embodiment, the relationship between the resistance value (R4) of the resistor 37c and the resistance value (R3) of the resistor 27c is not particularly limited. For example, the resistance values R3 and R4 can be made substantially equal to each other. Thus, when the value of the resistance value R4 is made larger than that in the third embodiment, the surge voltage can be reduced thereby.

  The configuration shown in the present embodiment is not limited to the combination with the configuration shown in the first embodiment. Other combinations with the configurations shown in the second and third embodiments, which are the preceding embodiments, are also possible.

(Fifth embodiment)
This embodiment can refer to the preceding embodiment. For this reason, the description of the parts common to the drive circuit 10 shown in the previous embodiment is omitted.

  In the present embodiment, in addition to the configuration shown in the first embodiment, when the blocking units 27 and 37 determine the short-circuit abnormality of the other arm 5b based on at least one sense voltage Vse of the IGBT 6 and the MOSFET 7, All the MOSFETs 7 are shut off.

  Specifically, as shown in FIG. 15, the blocking part has a wiring part 40. The wiring unit 40 connects the outputs of the filters 27a and 37a, in other words, the gate electrodes of the MOSFETs constituting the soft cutoff units 27b and 37b. For example, when a short circuit abnormality is determined by the filter 37a, an H level signal is input not only to the soft shut-off unit 37b but also to the soft shut-off unit 27b.

  Therefore, not only the MOSFET 7 in the short filter period Tf2 but also the IGBT 6 is cut off at the same timing. Thereby, also about IGBT6 of long filter period Tf1, short circuit energy can be made small. According to this, since all the switching elements are shut off based on the determination of the earliest short-circuit abnormality, the short-circuit energy can be reduced for all the switching elements.

  The disclosure of this specification is not limited to the illustrated embodiments. The disclosure encompasses the illustrated embodiments and variations by those skilled in the art based thereon. For example, the disclosure is not limited to the combination of elements shown in the embodiments. The disclosure can be implemented in various combinations. The technical scope disclosed is not limited to the description of the embodiments. The several technical scopes disclosed are indicated by the description of the claims, and should be understood to include all modifications within the meaning and scope equivalent to the description of the claims. .

  An object to be driven by the drive IC 10 is not limited to the switching elements that constitute the upper and lower arm circuits 5 a of the inverter 5. The present invention can also be applied to switching elements constituting other upper and lower arm circuits. For example, in a boost converter that boosts a DC voltage supplied from the DC power supply 2, the present invention can also be applied to switching elements of upper and lower arm circuits.

  The configuration of the switching elements connected in parallel is not limited to the combination of Si-IGBT and SiC-IGBT described above. The number of switching elements connected in parallel is not limited to two. The mirror periods may be different from each other for a plurality of switching elements connected in parallel.

DESCRIPTION OF SYMBOLS 1 ... Power converter device, 2 ... DC power supply, 3 ... Motor, 4 ... Smoothing capacitor, 5 ... Inverter, 5a ... Upper and lower arm circuit, 5b ... Arm, 6 ... IGBT, 7 ... MOSFET, 8 ... FWD, 9 ... Control circuit DESCRIPTION OF SYMBOLS 10 ... Drive IC, 20 ... IGBT drive part, 21 ... On drive part, 22 ... Off drive part, 23 ... Connection point, 24, 25 ... Resistance, 26 ... Comparator, 27 ... Cutoff part, 27a ... Filter, 27b ... Soft shut-off section, 27c ... resistor, 27d ... AND gate, 30 ... MOS drive section, 31 ... on drive section, 32 ... off drive section, 33 ... connection point, 34,35 ... resistor, 36 ... comparator, 37 ... cut-off section , 37a ... filter, 37b ... soft blocking part, 37c ... resistor, 40 ... wiring part

Claims (8)

A drive circuit that constitutes one arm (5b) of the upper and lower arm circuits (5a) and drives a plurality of switching elements (6, 7) connected in parallel with different mirror periods,
A comparison unit that compares a current correlation value correlated with a current flowing through each of the plurality of switching elements and a threshold value for determining that a short circuit has occurred in the other arm constituting the upper and lower arm circuits (26, 36)
On condition that the state where the current correlation value exceeds the threshold value continues even after the end of a predetermined filter period, a blocking unit (27, 37) for turning off the switching element that satisfies the condition;
With
The drive circuit in which the filter period is set according to the length of the mirror period, and the filter period is shortened as the switching element has a shorter mirror period.   2. The drive circuit according to claim 1, wherein the filter period is shortened as the switching element has a smaller capacitance between a gate electrode and a high potential side main electrode and a capacitance between the main electrodes. A plurality of the switching elements including a first switching element formed in silicon and a second switching element formed in silicon carbide;
The drive circuit according to claim 2, wherein the filter period of the second switching element is shorter than the filter period of the first switching element. In order to turn on the switching element, an on-drive unit (21, 31) for charging the gate electrode of the switching element with a driving current is provided for each switching element,
The drive circuit according to any one of claims 1 to 3, wherein the filter period is shortened as the switching element has a larger drive current. The plurality of switching elements have different short circuit tolerances,
The drive circuit according to any one of claims 1 to 4, wherein the switching element having a smaller short-circuit tolerance has a higher blocking speed by the blocking unit. A plurality of the switching elements including a first switching element formed in silicon and a second switching element formed in silicon carbide;
The drive circuit according to claim 5, wherein a cutoff speed of the second switching element is faster than a cutoff speed of the first switching element. The plurality of switching elements have different short circuit tolerances,
The said interruption | blocking part turns off the said switching element with a large said short circuit tolerance, when the said current correlation value of the said switching element with a small said short circuit tolerance becomes less than the said threshold value after exceeding the said threshold value. The drive circuit according to the item.   The drive circuit according to any one of claims 1 to 4, wherein the blocking unit turns off all of the plurality of switching elements when the condition is satisfied for at least one of the plurality of switching elements.

Images