JP2024114344A - Switch driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switch driving device in which protection against an actual flow of a short circuit current can be performed as quickly as possible while occurrence of wrong determination that a short circuit current is flowing is suppressed.

SOLUTION: A driving circuit Dr includes a diode 60 and a capacitor 62 that detect, as a determination voltage Vdesat, a drain-source voltage of a switch SW, and first and second comparators 66 and 68. The first comparator 66 compares the determination voltage Vdesat with a short circuit threshold Vthsc1. The second comparator 68 compares a gate voltage Vg of the switch SW with a mask threshold Vthsc2. A determination circuit 70 delays an output signal Sgv of the second comparator 68 by a filter period, and outputs the output signal Sgv. An AND circuit 71 outputs an abnormality signal Sgt on the basis of an output signal Sgc of the first comparator 66 and the output signal Sgfv of the determination circuit 70. The determination circuit 70 reduces the filter period if the temperature Tj of the switch SW is high.

SELECTED DRAWING: Figure 2

COPYRIGHT: (C)2024,JPO&INPIT

Description

This disclosure relates to a switch driver that drives switches in upper and lower arms connected in series.

Conventionally, there is known technology for protecting a switch from short circuit current when a short circuit occurs between the upper and lower arms, as described in, for example, Patent Document 1.

JP 2016-187296 A

The following configuration can be used to protect the switch from short-circuit current. The switch driver includes a parameter detector that detects either the terminal voltage (e.g., source-drain voltage), which is the voltage between the high-potential terminal and the low-potential terminal of the switch (e.g., an N-channel MOSFET) when the switch is on, or the current (e.g., drain current) that flows between the high-potential terminal and the low-potential terminal of the switch when the switch is on.

The drive device further includes a current determination unit, a voltage determination unit, and a signal output unit. The current determination unit determines whether the detection value of the parameter detection unit exceeds the short-circuit threshold. The voltage determination unit determines whether the gate voltage of the switch exceeds the mask threshold after the charging current starts to be supplied to the gate of the switch. The signal output unit outputs an abnormality signal that is a signal indicating that a short-circuit current is flowing through the switch at a timing when the filter period has elapsed since the voltage determination unit determined that the gate voltage of the switch exceeded the mask threshold in a state in which the current determination unit has determined that the detection value of the parameter detection unit exceeds the short-circuit threshold.

The filter period is set to prevent the occurrence of a situation in which it is erroneously determined that a short-circuit current is flowing through the switch when no short-circuit current is flowing. In other words, the detection value of the parameter detection unit during the transition period in which the switch is switched from the off state to the on state may temporarily be greater than the detection value of the parameter detection unit when the switch is in the on steady state. In this case, even though no short-circuit current is flowing, the detection value of the parameter detection unit may temporarily exceed the short-circuit threshold, resulting in an erroneous determination that a short-circuit current is flowing.

To prevent erroneous judgments, it is desirable to set the filter period to be longer. However, in this case, there is a risk that protection of the switch will be delayed if a short circuit current actually flows.

The primary objective of this disclosure is to provide a switch driver that can protect the switch as quickly as possible when a short-circuit current actually flows, while suppressing the occurrence of erroneous determinations that a short-circuit current is flowing.

The present disclosure relates to a switch drive device that drives upper and lower arm switches connected in series,
a parameter detection unit that detects either a terminal voltage that is a voltage between a high potential terminal and a low potential terminal of the switch when the switch is in an on state, or a current that flows between the high potential terminal and the low potential terminal of the switch when the switch is in an on state;
a current determination unit that determines whether or not a detection value of the parameter detection unit exceeds a short circuit threshold;
a voltage determination unit that determines whether or not a gate voltage of the switch exceeds a mask threshold after a charging current starts to be supplied to the gate of the switch;
a signal output unit that outputs an abnormality signal indicating that a short-circuit current is flowing through the switch at a timing when a filter period has elapsed since the voltage determination unit determined that the gate voltage of the switch exceeded the mask threshold in a state in which the current determination unit has determined that the detection value of the parameter detection unit exceeds the short-circuit threshold;
a state detection unit that detects either a temperature of the switch or a terminal-to-terminal voltage between a high potential terminal and a low potential terminal of the switch;
Equipped with
When the detection value of the state detection unit is high, the filter period is made shorter than when the detection value of the state detection unit is low.

This disclosure makes it possible to prevent erroneous determinations that a short-circuit current is flowing, while providing protection as quickly as possible when a short-circuit current actually does flow.

Here, the drive device of the present disclosure can be embodied, for example, as follows:

The state detection unit detects a temperature of the switch,
When the temperature detected by the state detection unit is high, the drive device shortens the filter period compared to when the temperature detected by the state detection unit is low.

The switch has the characteristic that the higher the switch temperature, the slower the switching speed and the smaller the short-circuit resistance. The slower the switching speed, the shorter the temporary increase period of the detection value of the parameter detection unit compared to the detection value in the steady on state during the transition period when the switch is switched from the off state to the on state. Considering the shorter increase period and the smaller short-circuit resistance, it is desirable to set the filter period to a short value when the switch temperature is high.

On the other hand, the switch has the characteristic that the lower the switch temperature, the higher the switching speed and the greater the short-circuit resistance. The higher the switching speed, the longer the temporary increase period of the detection value of the parameter detection unit compared to the detection value in the steady on state during the transition period when the switch is switched from the off state to the on state. Considering the longer increase period and the greater the short-circuit resistance, it is desirable to set the filter period longer when the switch temperature is low.

In consideration of this, when the temperature detected by the state detection unit is high, the filter period is made shorter than when the temperature detected by the state detection unit is low.

The drive device of the present disclosure can also be embodied as follows, for example:

The state detection unit detects a terminal voltage between a high potential terminal and a low potential terminal of the switch,
When the inter-terminal voltage detected by the state detection unit is high, the driving device shortens the filter period compared to when the inter-terminal voltage detected by the state detection unit is low.

The higher the terminal voltage when the switch is in the off state, the greater the short-circuit energy applied to the switch when a short-circuit current flows through the switch. In light of this, when the terminal voltage is high, it is desirable to set the filter period short from the perspective of switch protection.

In consideration of this, when the inter-terminal voltage detected by the state detection unit is high, the filter period is made shorter than when the inter-terminal voltage detected by the state detection unit is low.

Overall configuration diagram of the control system. FIG. 2 is a diagram showing a driver circuit and its peripheral configuration. FIG. 4 is a diagram showing an example of a determination circuit. 4 is a time chart showing an operation mode of a determination circuit. 4 is a flowchart showing a procedure of short-circuit protection control. FIG. 11 is a diagram showing a drive circuit and its peripheral configuration according to a second embodiment. FIG. 13 is a diagram showing a drive circuit and its peripheral configuration according to a third embodiment.

Several embodiments will be described with reference to the drawings. In several embodiments, functionally and/or structurally corresponding and/or associated parts may be given the same reference numerals or reference numerals that differ in the hundredth or higher digit. For corresponding and/or associated parts, the descriptions of other embodiments may be referred to.

First Embodiment
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a switch drive device according to the present disclosure will be described below with reference to the drawings.

As shown in FIG. 1, the control system includes a rotating electric machine 10, an inverter 20, and a control unit 23. In this embodiment, the rotating electric machine 10 includes a three-phase winding 11 that is star-connected. For example, the control system is mounted on a vehicle. In this case, the rotor of the rotating electric machine 10 is connected to the drive wheels of the vehicle so as to transmit power. The rotating electric machine 10 is, for example, a synchronous machine.

The rotating electric machine 10 is connected to a DC power source 21 via an inverter 20. In this embodiment, the DC power source 21 is a secondary battery such as a lithium ion battery or a nickel-metal hydride battery. The inverter 20 is equipped with a smoothing capacitor 22.

The inverter 20 has a series connection of upper and lower arm switches SW for each of the U, V, and W phases. In this embodiment, each switch SW is a voltage-controlled semiconductor switching element, specifically an N-channel MOSFET. Each switch SW has a body diode. In each switch SW, the high-potential terminal is the drain, and the low-potential terminal is the source.

Each switch may be an IGBT. In this case, a freewheel diode may be connected in inverse parallel to each switch SW. In an IGBT, the high-potential terminal is the collector, and the low-potential terminal is the emitter.

In each phase, the first end of the winding 11 is connected to the connection point between the low potential terminal of the upper arm switch SW and the high potential terminal of the lower arm switch SW. The second end of the winding 11 of each phase is connected at the neutral point.

The control unit 23 is mainly composed of a microcomputer, and performs switching control of each switch SW of the inverter 20 to control the control amount (e.g., torque) of the rotating electric machine 10 to a command value. The control unit 23 outputs a drive signal G* corresponding to the upper and lower arm switches SW to a drive circuit Dr provided individually for the upper and lower arm switches SW so that the upper and lower arm switches SW are alternately turned on with dead time in between. The drive signal G* takes either an on command to instruct the switch SW to be on, or an off command to instruct the switch SW to be off.

Next, the drive circuit Dr will be described using Figure 2. In this embodiment, the drive circuits Dr for the upper and lower arms are basically the same in configuration.

First, the switching control function of the switch SW will be described. The drive circuit Dr has a charge switch 31 and a discharge switch 32. A first end of the charge switch 31 is connected to a power supply terminal Tvcc of the drive circuit Dr. A constant voltage power supply 30 is connected to the power supply terminal Tvcc. The DC voltage supplied from the constant voltage power supply 30 to the power supply terminal Tvcc becomes the power supply voltage VCC (e.g., 15 V) of the drive circuit Dr.

The second end of the charging switch 31 is connected to the gate of the switch SW via the output terminal Tg of the driving circuit Dr. The power supply voltage VCC corresponds to the upper limit of the gate voltage of the switch SW. The source of the switch SW is connected to the output terminal Tg via the discharging switch 32. The source of the switch SW corresponds to the ground section.

The drive circuit Dr includes a switching drive unit 33. The switching drive unit 33 acquires a drive signal G* output from the control unit 23. When the acquired drive signal G* is an ON command, the switching drive unit 33 performs a charging process. The charging process is a process of turning on the charge switch 31 and turning off the discharge switch 32. According to the charging process, the gate voltage of the switch SW becomes equal to or higher than the threshold voltage Vth of the switch SW, and the switch SW is switched on.

When the acquired drive signal G* is an OFF command, the switching drive unit 33 performs a discharge process. The discharge process is a process of turning off the charge switch 31 and turning on the discharge switch 32. According to the discharge process, the gate voltage of the switch SW becomes less than the threshold voltage Vth, and the switch SW is switched off.

The functions provided by the switching driver 33 can be provided, for example, by software recorded in a physical memory device and a computer that executes the software, hardware, or a combination of these.

Next, we will explain the overheating protection function of the switch SW.

The drive circuit Dr includes a temperature detection circuit 41. An output signal of the temperature sensor 40 is input to the temperature detection circuit 41 via the first temperature detection terminal Tt1 and the second temperature detection terminal Tt2 of the drive circuit Dr. The temperature sensor 40 in this embodiment is a temperature-sensitive diode, and outputs a signal according to the temperature of the switch SW. The temperature detection circuit 41 detects the temperature of the switch SW based on the output signal of the temperature sensor 40. In this embodiment, the temperature sensor 40 and the temperature detection circuit 41 correspond to a "state detection unit."

The drive circuit Dr includes an overheat protection comparator 42, a power supply 43, and an abnormality signal output circuit 50. The temperature of the switch SW detected by the temperature detection circuit 41 (hereinafter, the detection temperature Tj) is input to the non-inverting input terminal of the overheat protection comparator 42. The DC voltage output from the power supply 43 is input to the inverting input terminal of the overheat protection comparator 42. The output voltage of the power supply 43 is the overheat threshold Tth. The overheat threshold Tth is set to the allowable upper limit temperature of the switch SW or a value less than the allowable upper limit temperature of the switch SW.

The output terminal of the overheat protection comparator 42 is connected to the abnormality signal output circuit 50. When the detection temperature Tj is less than the overheat threshold Tth, the logic of the output signal St from the overheat protection comparator 42 to the abnormality signal output circuit 50 becomes L. On the other hand, when the detection temperature Tj exceeds the overheat threshold Tth, the logic of the output signal St from the overheat protection comparator 42 to the abnormality signal output circuit 50 switches to H. When the abnormality signal output circuit 50 determines that the logic of the output signal St of the overheat protection comparator 42 has switched from L to H, it inverts the logic of the fail signal Sf, which is a signal indicating that an abnormality has occurred (for example, switches it from L to H). The fail signal Sf is output from the fail terminal Tf of the drive circuit Dr and input to the control unit 23.

Next, the overcurrent (short-circuit current) protection function of the switch SW will be described. This protection function protects against overcurrent that occurs when the rotating electric machine 10 or the load is short-circuited. Specifically, for example, this protection function protects the switch on the own arm side from short-circuit current when a short circuit occurs in one of the switches SW on the opposing arm side of the upper and lower arm switches SW, causing an upper/lower arm short circuit in which the switch on the other own arm side is switched on.

The drive circuit Dr in this embodiment has a Desat-type overcurrent protection function, and more specifically, has a diode 60, a resistor 61, a capacitor 62, a constant current power supply 63, a supply switch 64, and a reset switch 65.

The drain, which is the high potential terminal of the switch SW, is connected to the cathode of the diode 60. The first end of the resistor 61 is connected to the anode of the diode 60. The second end of the resistor 61 is connected to the first end of the capacitor 62 and to the monitor terminal Tdesat of the drive circuit Dr. The second end of the capacitor 62 is connected to the source, which is the low potential terminal of the switch SW. Note that the resistor 61 is not essential. In this case, the anode of the diode 60 is connected to the first end of the capacitor 62.

A constant current power supply 63 is connected to the monitor terminal Tdesat via a supply switch 64. The constant current power supply 63 has a function of receiving power from the constant voltage power supply 30 and outputting a constant current. The source of the switch SW is also connected to the monitor terminal Tdesat via a reset switch 65. In this embodiment, the diode 60, resistor 61, capacitor 62, supply switch 64, and reset switch 65 correspond to a "parameter detection unit."

The drive circuit Dr includes a first comparator 66, a first power supply 67, a second comparator 68, a second power supply 69, a judgment circuit 70, and an AND circuit 71 as a configuration for overcurrent protection. The monitor terminal Tdesat is connected to the non-inverting input terminal of the first comparator 66. As a result, the judgment voltage Vdesat, which is the terminal voltage of the capacitor 62, is input to the non-inverting input terminal of the first comparator 66. The short-circuit threshold Vthsc1, which is the output voltage of the first power supply 67, is input to the inverting input terminal of the first comparator 66. The short-circuit threshold Vthsc1 is set to a value that can determine whether a short circuit has occurred between the upper and lower arms and a short-circuit current flows through the switch SW. In this embodiment, the first comparator 66 and the first power supply 67 correspond to a "current judgment unit".

The non-inverting input terminal of the second comparator 68 is connected to the output terminal Tg. As a result, the gate voltage Vg of the switch SW is input to the non-inverting input terminal of the second comparator 68. The mask threshold Vthsc2, which is the output voltage of the second power supply 69, is input to the inverting input terminal of the second comparator 68. In this embodiment, the mask threshold Vthsc2 is set to a value that is equal to or greater than the threshold voltage Vth of the switch SW (specifically, for example, the mirror voltage of the switch SW) and less than the power supply voltage VCC. In this embodiment, the second comparator 68 and the second power supply 69 correspond to a "voltage determination unit."

The output signal Sgv of the second comparator 68 is input to the judgment circuit 70. The voltage judgment signal Sgfv, which is the output signal of the judgment circuit 70, and the current judgment signal Sgc, which is the output signal of the first comparator 66, are input to the AND circuit 71. The AND circuit 71 outputs an abnormality signal Sgt of logic H when the logic of both the voltage judgment signal Sgfv and the current judgment signal Sgc is H. The abnormality signal Sgt of logic H is a signal indicating that a short-circuit current is flowing between the drain and source of the switch SW. On the other hand, the AND circuit 71 outputs an abnormality signal Sgt of logic L when the logic of at least one of the voltage judgment signal Sgfv and the current judgment signal Sgc is L. The abnormality signal Sgt of logic L is a signal indicating that no short-circuit current is flowing between the drain and source of the switch SW. When the abnormality signal output circuit 50 determines that the logic of the abnormality signal Sgt of the AND circuit 71 has switched from L to H, it inverts the logic of the fail signal Sf (for example, switches it from L to H). In this embodiment, the determination circuit 70 and the AND circuit 71 correspond to the "signal output unit."

The switching drive unit 33 controls the drive of the supply switch 64 and the reset switch 65. In detail, when the switching drive unit 33 determines that the drive signal G* has been switched to an ON command, it switches the supply switch 64 ON while keeping the reset switch 65 OFF. As a result, current begins to be supplied from the constant current power supply 63 to the capacitor 62, and the determination voltage Vdesat begins to rise from 0.

When no short-circuit current flows through the switch SW, the judgment voltage Vdesat does not rise to the short-circuit threshold Vthsc1 during the period when the ON command is issued. On the other hand, when a short-circuit current flows through the switch SW, the judgment voltage Vdesat exceeds the short-circuit threshold Vthsc1 during the period when the ON command is issued. In this case, the logic of the current judgment signal Sgc of the first comparator 66 switches from L to H.

The switching driver 33 temporarily turns on the reset switch 65 during the period when the drive signal G* is in an OFF command. This resets the determination voltage Vdesat to 0.

The determination circuit 70 is a processing circuit that outputs the logic signal Sgv output from the second comparator 68 with a delay of the filter period Lf. The determination circuit 70 is intended to quickly protect the switch SW when a short-circuit current actually flows while suppressing the occurrence of erroneous determination that a short-circuit current is flowing through the switch SW.

In other words, the judgment voltage Vdesat during the transition period in which the switch SW is switched from the OFF state to the ON state by the charging process may temporarily be higher than the judgment voltage Vdesat when the switch SW is in the ON steady state, for example, due to ringing of the drain current of the switch SW. The ON steady state is, for example, a state in which the gate voltage of the switch SW has reached the power supply voltage VCC. In this case, even though no short-circuit current is flowing, the judgment voltage Vdesat temporarily exceeds the short-circuit threshold Vthsc1, and the logic of the current judgment signal Sgc of the first comparator 66 temporarily becomes H.

Here, after the charging process is started, the second timing at which the gate voltage exceeds the mask threshold Vthsc2 is later than the first timing at which the judgment voltage Vdesat exceeds the short-circuit threshold Vthsc1. By taking advantage of the fact that the second timing is later than the first timing, the current judgment signal Sgc of the first comparator 66 is not used to judge whether or not a short-circuit current is flowing during the period when the judgment voltage Vdesat is temporarily large. To achieve this, it is necessary to appropriately adjust the filter period. Therefore, in this embodiment, the drive circuit Dr is provided with a judgment circuit 70.

In particular, the determination circuit 70 of this embodiment has a function of making the filter period Lf when the detection temperature Tj exceeds the temperature threshold Tfth (< overheat threshold Tth) shorter than the filter period Lf when the detection temperature Tj is equal to or lower than the temperature threshold Tfth. This function is intended to suppress the occurrence of erroneous determination that a short-circuit current is flowing through the switch SW, while enhancing the effect of quickly protecting the switch SW when a short-circuit current actually flows.

In other words, the switch SW has the characteristic that the higher the temperature of the switch SW, the slower the switching speed and the smaller the short-circuit resistance. The slower the switching speed, the shorter the temporary increase period of the determination voltage Vdesat during the transition period in which the switch SW is switched from the off state to the on state. Considering that the increase period is shorter and the short-circuit resistance is smaller, when the temperature of the switch SW is high, it is desirable to set the filter period Lf to be short.

On the other hand, the switch SW has a characteristic that the lower the temperature of the switch SW, the higher the switching speed and the greater the short-circuit resistance. The higher the switching speed, the longer the temporary increase period of the judgment voltage Vdesat becomes during the transition period in which the switch SW is switched from the off state to the on state. In consideration of the longer increase period and the greater the short-circuit resistance, it is desirable to set the filter period Lf to be long when the temperature of the switch SW is low. Therefore, the judgment circuit 70 adjusts the length of the filter period Lf based on the detection temperature Tj.

An example of the determination circuit 70 is described below with reference to FIG.

The determination circuit 70 includes a switch section 72, a low-temperature side processing circuit 80, a high-temperature side processing circuit 90, a clock generation circuit 73, and an OR circuit 100.

The detected temperature Tj is input to the switch unit 72. The switch unit 72 includes a high-temperature side switch 71H and a low-temperature side switch 71L. When the detected temperature Tj is equal to or lower than the temperature threshold Tfth, the switch unit 72 turns on the low-temperature side switch 71L and turns off the high-temperature side switch 71H. As a result, the output signal Sgv of the second comparator 68 is input to the low-temperature side processing circuit 80. On the other hand, when the detected temperature Tj exceeds the temperature threshold Tfth, the switch unit 72 turns off the low-temperature side switch 71L and turns on the high-temperature side switch 71H. As a result, the output signal Sgv of the second comparator 68 is input to the high-temperature side processing circuit 90.

The low-temperature side processing circuit 80 is a shift register circuit including m D-type flip-flop circuits 81. The clock signal CLOCK output from the clock generation circuit 73 is input to the C terminal of each D-type flip-flop circuit 81. The output signal Sgv of the second comparator 68 is input to the D terminal of the topmost D-type flip-flop circuit 81 through the switch unit 72. The D terminal of the lowermost D-type flip-flop circuit 81 is connected to the Q terminal of the uppermost D-type flip-flop circuit 81. The OR circuit 100 is connected to the Q terminal of the bottommost D-type flip-flop circuit 81 of each D-type flip-flop circuit 81.

The high-temperature side processing circuit 90 is a shift register circuit having n D-type flip-flop circuits 91. The high-temperature side processing circuit 90 has basically the same configuration as the low-temperature side processing circuit 80. However, n<m, and in the example shown in FIG. 3, n=2, m=3. An OR circuit 100 is connected to the Q terminal of the bottommost D-type flip-flop circuit 91 of each D-type flip-flop circuit 91 in the high-temperature side processing circuit 90. Note that the number of flip-flop circuits in each processing circuit 80, 90 is not limited to the number shown in FIG. 3, and the number of flip-flop circuits in either processing circuit 80, 90 may be one.

The output signal SgL of the low-temperature side processing circuit 80 (i.e., the output signal of the Q terminal of the lowest-stage D-type flip-flop circuit 81) and the output signal SgH of the high-temperature side processing circuit 90 (i.e., the output signal of the Q terminal of the lowest-stage D-type flip-flop circuit 91) are input to an OR circuit 100. When the logic of at least one of the output signal SgL of the low-temperature side processing circuit 80 and the output signal SgH of the high-temperature side processing circuit 90 is H, the OR circuit 100 outputs a voltage determination signal Sgfv of logic H. On the other hand, when the logic of both the output signal SgL of the low-temperature side processing circuit 80 and the output signal SgH of the high-temperature side processing circuit 90 is L, the OR circuit 100 outputs a voltage determination signal Sgfv of logic L.

Figure 4 shows the transition of the output signal of the determination circuit 70 when the detection temperature Tj is equal to or lower than the temperature threshold Tfth and when it exceeds the temperature threshold Tfth. In Figure 4, one period of the clock signal CLOCK of the clock generation circuit 73 is indicated by tck. In the example shown in Figure 4, the logic of the current determination signal Sgc of the first comparator 66 is set to H.

First, we will explain the case where the detected temperature Tj is equal to or lower than the temperature threshold Tfth.

At time t0, the logic of the clock signal CLOCK is inverted to H, and at time t1 before the logic of the clock signal CLOCK is inverted to L, the logic of the output signal Sgv of the second comparator 68 is inverted to H.

Then, at time t2, which is "(n-1) x tck" (i.e., one cycle of the clock signal CLOCK) after time t0, the logic of the output signal SgH of the high-temperature side processing circuit 90 is inverted to H, and as a result, the logic of the voltage determination signal Sgfv of the OR circuit 100 is also inverted to H.

Next, we will explain the case where the detected temperature Tj exceeds the temperature threshold Tfth.

At time t0, the logic of the clock signal CLOCK is inverted to H, and at time t1 before the logic of the clock signal CLOCK is inverted to L, the logic of the output signal Sgv of the second comparator 68 is inverted to H.

Then, at time t3, which is "(m-1) x tck" (i.e., two cycles of the clock signal CLOCK) after time t0, the logic of the output signal SgL of the low-temperature side processing circuit 80 is inverted to H, which in turn inverts the logic of the voltage determination signal Sgfv of the OR circuit 100 to H.

Next, we will use Figure 5 to explain the process of protecting the switch SW from short-circuit current.

In step S10, the switch unit 72 determines whether the detected temperature Tj exceeds the temperature threshold Tfth.

If the switch unit 72 determines that the detected temperature Tj exceeds the temperature threshold Tfth, the process proceeds to step S11, where the high-temperature switch 71H is turned on and the low-temperature switch 71L is turned off. On the other hand, if the switch unit 72 determines that the detected temperature Tj is equal to or lower than the temperature threshold Tfth, the process proceeds to step S12, where the low-temperature switch 71L is turned on and the high-temperature switch 71H is turned off.

In the following step S13, the AND circuit 71 determines whether the logic of the current determination signal Sgc of the first comparator 66 is H or not.

In the following step S14, the AND circuit 71 determines whether the logic of the voltage determination signal Sgfv output from the determination circuit 70 is H. If the AND circuit 71 determines that the logic of the current determination signal Sgc of the first comparator 66 is H and that the logic of the voltage determination signal Sgfv output from the determination circuit 70 is H, the AND circuit 71 inverts the logic of the abnormality signal Sgt to H. As a result, in step S16, the abnormality signal output circuit 50 inverts the logic of the fail signal Sf to H.

In step S17, if the control unit 23 determines that the logic of the received fail signal Sf is H, it performs short-circuit protection control to turn off the drive signal G* output to each drive circuit Dr. In this embodiment, the control unit 23 corresponds to the "switch protection unit."

According to the present embodiment described above, it is possible to quickly protect the switch SW when a short-circuit current actually flows while suppressing the occurrence of erroneous determination that a short-circuit current is flowing through the switch SW.

Second Embodiment
Hereinafter, the second embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, the length of the filter period Lf is adjusted based on the drain-source voltage Vds of the switch SW that is turned off, instead of the temperature of the switch SW.

Figure 6 shows the drive circuit Dr and its peripheral configuration in this embodiment.

The control system includes a plurality of voltage-dividing resistors 44 as a ladder detection circuit, and the drive circuit Dr includes a voltage detection circuit 45. The voltage-dividing resistors 44 connect the drain of the switch SW to the voltage detection terminal Tvd of the drive circuit Dr. The voltage detection circuit 45 detects the divided voltage value between the drain and source of the switch SW. In this embodiment, the voltage-dividing resistors 44 and the voltage detection circuit 45 correspond to the "state detection unit."

The drive circuit Dr includes a comparator 46 and a power supply 47. The detection voltage VHr of the voltage detection circuit 45 is input to the non-inverting input terminal of the comparator 46. The voltage threshold VHth, which is the output voltage of the power supply 47, is input to the inverting input terminal of the comparator 46.

The following describes the differences between the judgment circuit 70 of this embodiment and the first embodiment.

The output signal of the comparator 46 and the drive signal G* are input to the switch section 72 of the judgment circuit 70. If the switch section 72 judges that the logic of the output signal of the comparator 46 is H during the period in which the drive signal G* was previously commanded to be OFF, the switch section 72 turns on the high-temperature side switch 71H and turns off the low-temperature side switch 71L. As a result, the output signal Sgv of the second comparator 68 is input to the high-temperature side processing circuit 90.

On the other hand, if the switch unit 72 determines that the logic of the output signal of the comparator 46 is L during the period in which the drive signal G* was previously commanded to be OFF, it turns on the low-temperature side switch 71L and turns off the high-temperature side switch 71H. As a result, the output signal Sgv of the second comparator 68 is input to the low-temperature side processing circuit 80.

According to the present embodiment described above, for example, when the power consumption of the device to be powered by the DC power source 21, such as the rotating electric machine 10, changes, or when the output voltage of the DC-DC converter changes in a control system in which the DC-DC converter is provided between the inverter 20 and the DC power source 21, the same effect as the first embodiment can be achieved.

Third Embodiment
Hereinafter, the third embodiment will be described with reference to the drawings, focusing on the differences from the first embodiment. In this embodiment, as shown in FIG. 7, the configuration for adjusting the length of the filter period is changed.

As shown in FIG. 7, the inverter 20 includes a first low-pass filter circuit having a first resistor 51a and a first capacitor 51b, and a second low-pass filter circuit having a second resistor 52a and a second capacitor 52b. The resistance of the first resistor 51a is R1, the capacitance of the first capacitor 51b is C1, the resistance of the second resistor 52a is R2, and the capacitance of the second capacitor 52b is C2. In this case, the time constant τ1 (=R1×C1) of the first low-pass filter circuit is smaller than the time constant τ2 (=R2×C2) of the second low-pass filter circuit.

The gate voltage Vg of the switch SW is subjected to low-pass filtering in the first low-pass filter circuit, and then is taken in from the first detection terminal TV1 of the drive circuit Dr. The gate voltage Vg of the switch SW is subjected to low-pass filtering in the second low-pass filter circuit, and then is taken in from the second detection terminal TV2 of the drive circuit Dr.

The drive circuit Dr includes a switch section 172. The switch section 172 includes a high-temperature switch 173H, a low-temperature switch 173L, an inverting circuit 174, a comparator 175, and a power supply 176. The high-temperature switch 173H connects the first detection terminal TV1 to the non-inverting input terminal of the second comparator 68. The low-temperature switch 173L connects the second detection terminal TV2 to the non-inverting input terminal of the second comparator 68.

The detected temperature Tj is input to the non-inverting input terminal of the comparator 175. The temperature threshold Tfth, which is the output voltage of the power supply 176, is input to the inverting input terminal of the comparator 175. The output signal of the comparator 175 is supplied to the high temperature side switch 173H and the inversion circuit 174. The output signal of the inversion circuit 174 is supplied to the low temperature side switch 173L. In this embodiment, the first resistor 51a, the first capacitor 51b, the second resistor 52a, the second capacitor 52b, the AND circuit 71, and the switch unit 172 correspond to the "signal output unit".

Next, we will explain the operation of the switch unit 172.

When the detected temperature Tj is lower than the temperature threshold Tfth and the logic of the output signal of the comparator 175 becomes L, the low-temperature side switch 173L is turned on and the high-temperature side switch 173H is turned off. As a result, the gate voltage Vg that has been subjected to low-pass filtering in the first low-pass filter circuit, which has a relatively small time constant, is input to the non-inverting input terminal of the second comparator 68.

On the other hand, when the detected temperature Tj exceeds the temperature threshold Tfth and the logic of the output signal of the comparator 175 becomes H, the low-temperature side switch 173L is turned off and the high-temperature side switch 173H is turned on. As a result, the gate voltage Vg that has been subjected to low-pass filtering in the second low-pass filter circuit, which has a relatively large time constant, is input to the non-inverting input terminal of the second comparator 68.

In this embodiment, the output signal Sgv of the second comparator 68 is input to the AND circuit 71. The AND circuit 71 outputs an abnormality signal Sgt of logic H when the logic of both the output signal Sgv of the second comparator 68 and the current determination signal Sgc is H. On the other hand, the AND circuit 71 outputs an abnormality signal Sgt of logic L when the logic of at least one of the output signal Sgv of the second comparator 68 and the current determination signal Sgc is L.

According to the present embodiment described above, it is possible to achieve effects similar to those of the first embodiment.

<Other embodiments>
Each of the above embodiments may be modified as follows.

- The adjustment of the length of the filter period is not limited to two stages, but may be three or more stages. Also, the adjustment of the length of the filter period may be continuous rather than staged.

- In the first and third embodiments, the temperature sensor may be, for example, a thermistor.

- In the second embodiment, the "state detection unit" which is a voltage detection unit that detects the drain-source voltage of the switch SW is not limited to the voltage dividing resistor 44 and the voltage detection circuit 45, but may be, for example, a high-voltage monitor IC. The high-voltage monitor IC is, for example, a single-packaged integrated circuit having a first terminal and a second terminal, and directly detects the voltage between the first and second terminals. The first terminal is connected to the drain, and the second terminal is connected to the source.

The configuration for detecting the drain current flowing through the switch SW that is turned on is not limited to the Desat type configuration. For example, a configuration may be used that includes a sense terminal of the switch SW and a sense resistor that generates a voltage drop according to the current flowing through the sense terminal, and detects the drain current based on a sense voltage that is the potential difference of the sense resistor. In this case, the sense voltage may be input to the non-inverting input terminal of the first comparator 66 in FIG. 2, for example.

The configuration of the determination circuit 70 and other components of the drive circuit Dr is not limited to analog circuits, but may also be realized by software that includes a processor and a memory in which a program is stored, and in which the program stored in the processor is executed.

- The power conversion circuit to which the drive device of the present disclosure is applied is not limited to an inverter, but may be, for example, a DC-DC converter (e.g., a step-up/step-down DC-DC converter) equipped with upper and lower arm switches.

20... inverter, 60... diode, 62... capacitor, 66... first comparator, 67... first power supply, 68... second comparator, 69... second power supply, SW... switch, Dr... drive circuit.

Claims (4)

In a switch drive device that drives upper and lower arm switches (SW) connected in series,
a parameter detection unit (60 to 65) that detects either a terminal voltage (Vdesat) that is a voltage between a high potential terminal and a low potential terminal of the switch when the switch is in an on state, or a current that flows between the high potential terminal and the low potential terminal of the switch when the switch is in an on state;
a current determination unit (66, 67) that determines whether or not a detection value of the parameter detection unit exceeds a short circuit threshold (Vthsc1);
a voltage determination unit (68, 69) that determines whether or not a gate voltage of the switch after a charging current starts to be supplied to the gate of the switch exceeds a mask threshold (Vthsc2);
a signal output unit (70, 71; 51a, 51b, 52a, 52b, 71, 172) that outputs an abnormality signal (Sgt) indicating that a short-circuit current is flowing through the switch at a timing when a filter period (Lf) has elapsed since the voltage determination unit determined that the gate voltage of the switch exceeded the mask threshold in a state in which the current determination unit has determined that the detection value of the parameter detection unit exceeds the short-circuit threshold;
a state detection unit (40, 41; 44, 45) for detecting either a temperature (Tj) of the switch or a terminal voltage (VHr) between a high potential terminal and a low potential terminal of the switch;
Equipped with
A switch driver that shortens the filter period when the detection value of the state detection unit is high compared to when the detection value of the state detection unit is low. the current determination unit outputs a determination result as to whether or not a current detection value of the parameter detection unit exceeds the short circuit threshold value as a binary logic signal;
the voltage determination unit outputs a determination result as to whether or not the current gate voltage of the switch exceeds the mask threshold value as a binary logic signal;
The signal output unit is
a determination circuit (70) that outputs a logic signal output from the voltage determination unit after delaying it by the filtering period;
outputting the abnormality signal based on the logic signal output from the determination circuit and the logic signal of the current determination unit;
2. The switch drive device according to claim 1, wherein the filter period is set shorter when the detection value of the state detection section is high than when the detection value of the state detection section is low. the current determination unit outputs a determination result as to whether or not a current detection value of the parameter detection unit exceeds the short circuit threshold value as a binary logic signal;
the signal output unit has a filter circuit (51 a, 51 b, 52 a, 52 b) that performs low-pass filtering on the gate voltage of the switch and outputs the result;
the voltage determination unit outputs a determination result as to whether or not the gate voltage that has been subjected to the low-pass filtering process in the filter circuit exceeds the mask threshold value as a binary logic signal;
The signal output unit is
When the detection value of the state detection unit is high, the time constant of the low-pass filter processing is made smaller than when the detection value of the state detection unit is low, thereby shortening the filter period;
2. The switch drive device according to claim 1, wherein the abnormality signal is output based on a logic signal of the voltage determination section and a logic signal of the current determination section. A switch protection unit (23) is provided,
4. The switch drive device according to claim 1, wherein the switch protector switches a drive signal for the switch to an OFF command when the abnormality signal is received.

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