Switch drive mechanism

Abstract

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

Description

Technical Field

[0001] The present disclosure relates to a switch driving device that drives switches of upper and lower arms connected in series.

Background Art

[0002] Conventionally, as described in Patent Document 1 for example, a technique for protecting a switch from a short-circuit current when a short circuit occurs between the upper and lower arms is known.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As a configuration for protecting a switch from a short-circuit current, the following configuration can be mentioned. The switch driving device includes a parameter detection unit that detects either the voltage between terminals (for example, the voltage between the source and the drain), which is the voltage between the high-potential side terminal and the low-potential side terminal of the switch when the switch (for example, an N-channel MOSFET) is turned on, or the current flowing between the high-potential side terminal and the low-potential side terminal of the switch (for example, the drain current) when the switch is turned on.

[0005] The drive unit further includes a current determination unit, a voltage determination unit, and a signal output unit. The current determination unit determines whether the value detected by 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 has started to be supplied to the gate of the switch. The signal output unit outputs an abnormal signal, which is a signal indicating that a short-circuit current is flowing through the switch, at a time when the current determination unit has determined that the value detected by the parameter detection unit exceeds the short-circuit threshold, and the voltage determination unit has determined that the gate voltage of the switch exceeds the mask threshold, after the filtering period has elapsed.

[0006] The filter period is set here to prevent a misinterpretation that a short-circuit current is flowing through the switch when it is not. In other words, the value detected by the parameter detection unit during the transient period when the switch is switched from the off state to the on state may temporarily be larger than the value detected by 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 value detected by the parameter detection unit may temporarily exceed the short-circuit threshold, leading to a misinterpretation that a short-circuit current is flowing.

[0007] To suppress the occurrence of false positives, it is desirable to set a longer filter period. However, in this case, there is a risk that the protection of the switch when an actual short-circuit current flows may be delayed.

[0008] The primary objective of this disclosure is to provide a switch drive device 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. [Means for solving the problem]

[0009] This disclosure relates to a switch drive device for driving switches of upper and lower arms connected in series, A parameter detection unit that detects either the terminal voltage, which is the voltage between the high-potential terminal and the low-potential terminal of the switch when the switch is in the ON state, or the current that flows between the high-potential terminal and the low-potential terminal of the switch when the switch is in the ON state, A current determination unit that determines whether the value detected by the parameter detection unit exceeds the short-circuit threshold, A voltage determination unit that determines whether the gate voltage of the switch exceeds a mask threshold after a charging current has started to be supplied to the gate of the switch, When the current determination unit determines that the value detected by the parameter detection unit exceeds the short-circuit threshold, and the voltage determination unit determines that the gate voltage of the switch exceeds the mask threshold, a signal output unit outputs an abnormal signal indicating that a short-circuit current is flowing through the switch at a time after the filtering period has elapsed, A state detection unit that detects either the temperature of the switch or the terminal voltage, which is the voltage between the high-potential terminal and the low-potential terminal of the switch, Equipped with, When the detected value of the state detection unit is high, the filter period is shortened compared to when the detected value of the state detection unit is low.

[0010] According to this disclosure, it is possible to suppress the occurrence of erroneous judgments that a short-circuit current is flowing, while providing protection as quickly as possible when a short-circuit current actually flows.

[0011] Here, the drive device of this disclosure can be embodied, for example, as follows.

[0012] The state detection unit detects the temperature of the switch, The drive device shortens the filter period when the temperature detected by the state detection unit is high compared to when the temperature detected by the state detection unit is low.

[0013] Switches have the characteristic that the higher the switch temperature, the lower the switching speed and the lower the short-circuit withstand capability. A lower switching speed means that during the transient period when the switch is switched from the off state to the on state, the temporary increase period of the parameter detection unit's detected value relative to the detected value in the on-steady state becomes shorter. Considering the shorter increase period and the lower short-circuit withstand capability, it is desirable to set a shorter filter period when the switch temperature is high.

[0014] On the other hand, switches have the characteristic that the lower the switch temperature, the higher the switching speed and the greater the short-circuit withstand capability. The higher the switching speed, the longer the period of temporary increase in the parameter detection unit's detected value relative to the detected value in the on steady state during the transient period when the switch is switched from the off state to the on state. Considering that the increase period is longer and the short-circuit withstand capability is greater, it is desirable to set a longer filter period when the switch temperature is low.

[0015] In light of this, when the temperature detected by the state detection unit is high, the filtering period is shortened compared to when the temperature detected by the state detection unit is low.

[0016] Furthermore, the drive device of this disclosure can also be materialized as follows, for example.

[0017] The state detection unit detects the terminal voltage, which is the voltage between the high-potential terminal and the low-potential terminal of the switch. The drive device shortens the filter period when the terminal voltage detected by the state detection unit is high compared to when the terminal voltage detected by the state detection unit is low.

[0018] The higher the terminal voltage when the switch is in the off position, the greater the short-circuit energy applied to the switch when a short-circuit current flows through it. Considering this, when the terminal voltage is high, it is desirable to set a shorter filter period from the perspective of switch protection.

[0019] In view of this point, 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.

Brief Description of the Drawings

[0020] [Figure 1] Overall configuration diagram of the control system. [Figure 2] Diagram showing the drive circuit and its peripheral configuration. [Figure 3] Diagram showing an example of the determination circuit. [Figure 4] Time chart showing the operation mode of the determination circuit. [Figure 5] Flowchart showing the procedure of short-circuit protection control. [Figure 6] Diagram showing the drive circuit according to the second embodiment and its peripheral configuration. [Figure 7] Diagram showing the drive circuit according to the third embodiment and its peripheral configuration.

Modes for Carrying Out the Invention

[0021] A plurality of embodiments will be described while referring to the drawings. In a plurality of embodiments, parts that functionally and / or structurally correspond and / or are associated may be assigned the same reference numerals, or reference numerals that differ in the hundreds place or more. For corresponding parts and / or associated parts, the description of other embodiments can be referred to.

[0022] <First Embodiment> Hereinafter, a first embodiment in which the drive device of the switch according to the present disclosure is embodied will be described while referring to the drawings.

[0023] As shown in Figure 1, the control system comprises a rotating electric machine 10, an inverter 20, and a control unit 23. In this embodiment, the rotating electric machine 10 has three-phase windings 11 connected in a star configuration. 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 vehicle's drive wheels so as to enable power transmission. The rotating electric machine 10 is, for example, a synchronous machine.

[0024] The rotating electric machine 10 is connected to a DC power supply 21 via an inverter 20. In this embodiment, the DC power supply 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.

[0025] The inverter 20 is equipped with 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.

[0026] Note that each switch may be an IGBT. In this case, a freewheeling diode must be connected in antiparallel to each switch SW. In an IGBT, the high-potential terminal is the collector, and the low-potential terminal is the emitter.

[0027] 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 for each phase is connected to the neutral point.

[0028] The control unit 23 is mainly composed of a microcontroller and controls the switching of each switch SW of the inverter 20 in order to control the control amount (e.g., torque) of the rotating electric machine 10 to a command value. The control unit 23 outputs drive signals G* corresponding to the upper and lower arm switches SW to the drive circuits Dr provided individually for the upper and lower arm switches SW in order to alternately turn the upper and lower arm switches SW on with a dead time in between. The drive signal G* takes the form of either an ON command that instructs the switch SW to be turned on, or an OFF command that instructs it to be turned off.

[0029] Next, the drive circuit Dr will be explained using Figure 2. The drive circuits Dr for the upper and lower arms in this embodiment are basically the same in configuration.

[0030] First, let's explain the switching control function of the switch SW. The drive circuit Dr is equipped with a charge switch 31 and a discharge switch 32. The first terminal of the charge switch 31 is connected to the power terminal Tvcc of the drive circuit Dr. A constant voltage power supply 30 is connected to the power terminal Tvcc. The DC voltage supplied from the constant voltage power supply 30 to the power terminal Tvcc becomes the power supply voltage VCC (for example, 15V) of the drive circuit Dr.

[0031] The second terminal of the charging switch 31 is connected to the gate of the switch SW via the output terminal Tg of the drive 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 discharge switch 32. The source of the switch SW corresponds to the ground.

[0032] 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. If the acquired drive signal G* is an ON command, the switching drive unit 33 performs a charging process. The charging process involves turning on the charging switch 31 and turning off the discharge switch 32. As a result of the charging process, the gate voltage of the switch SW becomes equal to or greater than the threshold voltage Vth of the switch SW, and the switch SW is switched to ON.

[0033] The switching drive unit 33 performs a discharge process if the acquired drive signal G* is an off command. The discharge process involves turning off the charge switch 31 and turning on the discharge switch 32. As a result of the discharge process, the gate voltage of the switch SW becomes less than the threshold voltage Vth, and the switch SW is switched to the off position.

[0034] The functions provided by the switching drive unit 33 can, for example, be provided by software recorded in a physical memory device and a computer, hardware, or a combination thereof that executes it.

[0035] Next, I will explain the overheat protection function of the switch SW.

[0036] The drive circuit Dr includes a temperature detection circuit 41. The output signal from 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. In this embodiment, the temperature sensor 40 is a thermosensitive diode and outputs a signal corresponding to the temperature of the switch SW. The temperature detection circuit 41 detects the temperature of the switch SW based on the output signal from the temperature sensor 40. In this embodiment, the temperature sensor 40 and the temperature detection circuit 41 correspond to the "state detection unit".

[0037] The drive circuit Dr includes an overheat protection comparator 42, a power supply 43, and an abnormal signal output circuit 50. The temperature of the switch SW detected by the temperature detection circuit 41 (hereinafter referred to as the detected 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 becomes the overheat threshold Tth. The overheat threshold Tth is set to the allowable upper temperature limit of the switch SW, or a value less than the allowable upper temperature limit of the switch SW.

[0038] The output terminal of the overheat protection comparator 42 is connected to the abnormal signal output circuit 50. When the detected temperature Tj is less than the overheat threshold Tth, the logic of the output signal St from the overheat protection comparator 42 to the abnormal signal output circuit 50 becomes L. On the other hand, when the detected temperature Tj exceeds the overheat threshold Tth, the logic of the output signal St from the overheat protection comparator 42 to the abnormal signal output circuit 50 switches to H. When the abnormal 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, by switching 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.

[0039] Next, I will explain the overcurrent (short-circuit current) protection function of the switch SW. This protection function protects against overcurrents that occur when the rotating electric machine 10 or the load is short-circuited. Specifically, for example, this protection function protects the switch on the self-arm side from short-circuit current when a short-circuit occurs in the upper and lower arm switches, where a short-circuit fault occurs in the switch on the opposing arm side of the upper and lower arm switches SW, causing the other switch on the self-arm side to be switched on.

[0040] The drive circuit Dr of this embodiment is equipped with a Desat-type overcurrent protection function, and more specifically comprises a diode 60, a resistor 61, a capacitor 62, a constant current power supply 63, a supply switch 64, and a reset switch 65.

[0041] The cathode of diode 60 is connected to the drain, which is the high-potential terminal of switch SW. The anode of diode 60 is connected to the first terminal of resistor 61. The second terminal of resistor 61 is connected to the first terminal of capacitor 62 and to the monitor terminal Tdesat of drive circuit Dr. The second terminal of capacitor 62 is connected to the source, which is the low-potential terminal of switch SW. Note that resistor 61 is not essential. In this case, the anode of diode 60 is connected to the first terminal of capacitor 62.

[0042] A constant current power supply 63 is connected to the monitor terminal Tdesat via a supply switch 64. The constant current power supply 63 is powered by a constant voltage power supply 30 and has the function of outputting a constant current. In addition, the source of a switch SW is 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 the "parameter detection unit".

[0043] The drive circuit Dr includes a first comparator 66, a first power supply 67, a second comparator 68, a second power supply 69, a determination 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 determination voltage Vdesat, which is the terminal voltage of 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 occurs in the upper and lower arms and whether a short-circuit current flows to the switch SW. In this embodiment, the first comparator 66 and the first power supply 67 correspond to the "current determination unit".

[0044] 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 greater than or equal to the threshold voltage Vth of the switch SW (specifically, for example, the Miller 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 the "voltage determination unit".

[0045] The output signal Sgv of the second comparator 68 is input to the determination circuit 70. The voltage determination signal Sgfv, which is the output signal of the determination circuit 70, and the current determination signal Sgc, which is the output signal of the first comparator 66, are input to the AND circuit 71. The AND circuit 71 outputs a logic H abnormal signal Sgt when the logic of both the voltage determination signal Sgfv and the current determination signal Sgc is H. The logic H abnormal signal Sgt indicates 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 a logic L abnormal signal Sgt when the logic of at least one of the voltage determination signal Sgfv and the current determination signal Sgc is L. The logic L abnormal signal Sgt indicates that no short-circuit current is flowing between the drain and source of the switch SW. The abnormal signal output circuit 50, when it determines that the logic of the abnormal signal Sgt of the AND circuit 71 has switched from L to H, inverts the logic of the fail signal Sf (for example, by switching it from L to H). In this embodiment, the determination circuit 70 and the AND circuit 71 correspond to the "signal output section".

[0046] The switching drive unit 33 controls the drive of the supply switch 64 and the reset switch 65. Specifically, 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 to 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.

[0047] If no short-circuit current flows through switch SW, the determination voltage Vdesat will not rise to the short-circuit threshold Vthsc1 during the period when the ON command is issued. On the other hand, if a short-circuit current flows through switch SW, the determination voltage Vdesat will exceed the short-circuit threshold Vthsc1 during the period when the ON command is issued. In this case, the logic of the current determination signal Sgc of the first comparator 66 switches from L to H.

[0048] The switching drive unit 33 temporarily turns on the reset switch 65 during the period when the drive signal G* is set to an off command. This resets the determination voltage Vdesat to 0.

[0049] The determination circuit 70 is a processing circuit that outputs the logic signal Sgv, which is output from the second comparator 68, with a delay of the filter period Lf. The determination circuit 70 is designed to suppress the occurrence of false judgments that a short-circuit current is flowing through the switch SW, while quickly protecting the switch SW if a short-circuit current actually flows.

[0050] In other words, the determination voltage Vdesat during the transient period when the switch SW is switched from the off state to the on state by the charging process may temporarily be higher than the determination 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, the state when the gate voltage of the switch SW reaches the power supply voltage VCC. In this case, even though no short-circuit current is flowing, the determination voltage Vdesat temporarily exceeds the short-circuit threshold Vthsc1, and the logic of the current determination signal Sgc of the first comparator 66 temporarily becomes high.

[0051] Here, after the charging process has started, the second timing at which the gate voltage exceeds the mask threshold Vthsc2 occurs later than the first timing at which the determination voltage Vdesat exceeds the short-circuit threshold Vthsc1. By utilizing the fact that the second timing occurs later than the first timing, the current determination signal Sgc of the first comparator 66 is not used to determine whether or not a short-circuit current is flowing during the period when the determination voltage Vdesat is temporarily large. To achieve this, it is necessary to properly adjust the filter period. Therefore, in this embodiment, the drive circuit Dr is equipped with a determination circuit 70.

[0052] In particular, the determination circuit 70 of this embodiment has a function to shorten the filter period Lf when the detected temperature Tj exceeds the temperature threshold Tfth (< overheating threshold Tth) compared to the filter period Lf when the detected temperature Tj is below the temperature threshold Tfth. This function is intended to suppress the occurrence of false determinations that a short-circuit current is flowing through the switch SW, while simultaneously enhancing the effectiveness of quickly protecting the switch SW when a short-circuit current actually flows.

[0053] In other words, a switch SW has the characteristic that the higher the temperature of the switch SW, the lower the switching speed and the lower the short-circuit withstand capability. The lower the switching speed, the shorter the period of temporary increase in the judgment voltage Vdesat during the transient period when the switch SW switches from the off state to the on state. Considering that the increase period is shorter and the short-circuit withstand capability is lower, it is desirable to set the filter period Lf to be shorter when the temperature of the switch SW is high.

[0054] On the other hand, the switch SW has the characteristic that the lower the temperature of the switch SW, the higher the switching speed and the greater the short-circuit withstand capability. The higher the switching speed, the longer the temporary increase period of the determination voltage Vdesat during the transient period when the switch SW switches from the off state to the on state. Considering that the increase period is longer and the short-circuit withstand capability is greater, it is desirable to set a longer filter period Lf when the temperature of the switch SW is low. Therefore, the determination circuit 70 adjusts the length of the filter period Lf based on the detected temperature Tj.

[0055] An example of the determination circuit 70 will be explained using Figure 3.

[0056] The determination circuit 70 includes a switch unit 72, a low-temperature processing circuit 80, a high-temperature processing circuit 90, a clock generation circuit 73, and an OR circuit 100.

[0057] The detected temperature Tj is input to the switch unit 72. The switch unit 72 is equipped with a high-temperature side switch 71H and a low-temperature side switch 71L. When the detected temperature Tj is less than or equal to 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.

[0058] The low-temperature side processing circuit 80 is a shift register circuit including m D-type flip-flop circuits 81. A clock signal CLOCK output from the clock generation circuit 73 is input to the C terminal of each D-type flip-flop circuit 81. Among each D-type flip-flop circuit 81, an output signal Sgv of the second comparator 68 is input to the D terminal of the uppermost D-type flip-flop circuit 81 via the switch unit 72. The D terminal of the lower-stage D-type flip-flop circuit 81 is connected to the Q terminal of the upper-stage D-type flip-flop circuit 81. Among each D-type flip-flop circuit 81, an OR circuit 100 is connected to the Q terminal of the lowermost D-type flip-flop circuit 81.

[0059] The high-temperature side processing circuit 90 is a shift register circuit including 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". Among each D-type flip-flop circuit 91 in the high-temperature side processing circuit 90, an OR circuit 100 is connected to the Q terminal of the lowermost D-type flip-flop circuit 91. 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 any one of the processing circuits 80, 90 may be one.

[0060] An output signal SgL of the low-temperature side processing circuit 80 (that is, an output signal of the Q terminal of the lowermost D-type flip-flop circuit 81) and an output signal SgH of the high-temperature side processing circuit 90 (that is, an output signal of the Q terminal of the lowermost D-type flip-flop circuit 91) are input to the OR circuit 100. When at least one of the logics 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 logics 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 are L, the OR circuit 100 outputs a voltage determination signal Sgfv of logic L.

[0061] Figure 4 shows the changes in the output signals of the determination circuit 70 when the detected temperature Tj is below 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 shown as tck. In the example shown in Figure 4, the logic of the current determination signal Sgc of the first comparator 66 is assumed to be H.

[0062] First, let's explain the case where the detected temperature Tj is below the temperature threshold Tfth.

[0063] 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.

[0064] Subsequently, at time t2, which is the time elapsed from time t0 by "(n-1) × tck" (i.e., one period of the clock signal CLOCK), the logic of the output signal SgH of the high-temperature processing circuit 90 is inverted to H, and as a result, the logic of the voltage judgment signal Sgfv of the OR circuit 100 is also inverted to H.

[0065] Next, we will explain the case where the detected temperature Tj exceeds the temperature threshold Tfth.

[0066] 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.

[0067] Subsequently, at time t3, which is the time elapsed from time t0 by "(m-1) × tck" (i.e., two periods of the clock signal CLOCK), the logic of the output signal SgL of the low-temperature processing circuit 80 is inverted to H, and as a result, the logic of the voltage judgment signal Sgfv of the OR circuit 100 is also inverted to H.

[0068] Next, we will explain the process of protecting the switch SW from short-circuit current using Figure 5.

[0069] In step S10, the switch unit 72 determines whether the detected temperature Tj exceeds the temperature threshold Tfth.

[0070] If the switch unit 72 determines that the detected temperature Tj exceeds the temperature threshold Tfth, it proceeds to step S11, where it turns on the high-temperature switch 71H and turns off the low-temperature switch 71L. On the other hand, if the switch unit 72 determines that the detected temperature Tj is less than or equal to the temperature threshold Tfth, it proceeds to step S12, where it turns on the low-temperature switch 71L and turns off the high-temperature switch 71H.

[0071] 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 high or low.

[0072] 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 high. If the AND circuit 71 determines that the logic of the current determination signal Sgc of the first comparator 66 is high, and the logic of the voltage determination signal Sgfv output from the determination circuit 70 is high, it inverts the logic of the abnormal signal Sgt to high. As a result, in step S16, the abnormal signal output circuit 50 inverts the logic of the fail signal Sf to high.

[0073] 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 by issuing an OFF command to the drive signal G* output to each drive circuit Dr. In this embodiment, the control unit 23 corresponds to the "switch protection unit".

[0074] As described in detail above, this embodiment makes it possible to quickly protect the switch SW when a short-circuit current actually flows, while suppressing the occurrence of erroneous judgments that a short-circuit current is flowing through the switch SW.

[0075] <Second Embodiment> The second embodiment will now be described, focusing on the differences from the first embodiment, with reference to the drawings. In this embodiment, the length of the filter period Lf is adjusted based on the drain-source voltage Vds of the switched-off switch SW, instead of the temperature of the switch SW.

[0076] Figure 6 shows the drive circuit Dr and its peripheral configuration according to this embodiment.

[0077] The control system includes multiple voltage divider resistors 44 as ladder detection circuits, and the drive circuit Dr includes a voltage detection circuit 45. The voltage divider 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 of the voltage between the drain and source of the switch SW. In this embodiment, the voltage divider resistors 44 and the voltage detection circuit 45 correspond to the "state detection unit".

[0078] The drive circuit Dr comprises a comparator 46 and a power supply 47. The non-inverting input terminal of the comparator 46 receives the detected voltage VHr from the voltage detection circuit 45. The inverting input terminal of the comparator 46 receives the voltage threshold VHth, which is the output voltage of the power supply 47.

[0079] The differences between the determination circuit 70 of this embodiment and that of the first embodiment will be explained.

[0080] The switch unit 72 of the determination circuit 70 receives the output signal of the comparator 46 and the drive signal G* as inputs. If the switch unit 72 determines that the logic of the output signal of the comparator 46 is H during the period when the drive signal G* was previously set to OFF, it 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.

[0081] On the other hand, if the switch unit 72 determines that the logic of the output signal of comparator 46 is L during the period when the drive signal G* was previously set to an OFF command, 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.

[0082] As described above, the same effects as in the first embodiment can be achieved, for example, when the power consumption of the equipment to which the DC power supply 21, such as a rotating electric machine 10, is supplied changes, or when the output voltage of the DC-DC converter changes in a control system in which a DC-DC converter is provided between the inverter 20 and the DC power supply 21.

[0083] <Third Embodiment> The third embodiment will be described below, focusing on the differences from the first embodiment, with reference to the drawings. In this embodiment, the configuration for adjusting the length of the filter period has been changed, as shown in Figure 7.

[0084] As shown in Figure 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. Let R1 be the resistance of the first resistor 51a, C1 be the capacitance of the first capacitor 51b, R2 be the resistance of the second resistor 52a, and C2 be the capacitance of the second capacitor 52b. 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.

[0085] The gate voltage Vg of switch SW is filtered in the first low-pass filter circuit and then received from the first detection terminal TV1 of the drive circuit Dr. Furthermore, the gate voltage Vg of switch SW is filtered in the second low-pass filter circuit and then received from the second detection terminal TV2 of the drive circuit Dr.

[0086] 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.

[0087] The non-inverting input terminal of comparator 175 receives the detected temperature Tj. The inverting input terminal of comparator 175 receives the temperature threshold Tfth, which is the output voltage of power supply 176. The output signal of comparator 175 is supplied to the high-temperature side switch 173H and the inverting circuit 174. The output signal of the inverting 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 section 172 correspond to the "signal output section".

[0088] Next, we will explain the operation of the switch unit 172.

[0089] When the detected temperature Tj is lower than the temperature threshold Tfth, and the logic of the output signal of comparator 175 becomes L, the low-temperature switch 173L is turned on and the high-temperature switch 173H is turned off. As a result, the gate voltage Vg, which has been low-pass filtered in the first low-pass filter circuit with a relatively small time constant, is input to the non-inverting input terminal of the second comparator 68.

[0090] On the other hand, when the detected temperature Tj exceeds the temperature threshold Tfth and the logic of the output signal of comparator 175 becomes high, the low-temperature switch 173L is turned off and the high-temperature switch 173H is turned on. As a result, the gate voltage Vg, which has been subjected to low-pass filtering in the second low-pass filter circuit with a relatively large time constant, is input to the non-inverting input terminal of the second comparator 68.

[0091] In this embodiment, the output signal Sgv of the second comparator 68 is input to the AND circuit 71. The AND circuit 71 outputs a logic H abnormal signal Sgt 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 a logic L abnormal signal Sgt 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.

[0092] According to the embodiment described above, the effects similar to those of the first embodiment can be achieved.

[0093] <Other Embodiments> Furthermore, each of the above embodiments may be implemented with the following modifications.

[0094] The length of the filter period may be adjusted in three or more stages, not just two. Furthermore, the adjustment of the filter period length may be continuous rather than stepwise.

[0095] In the first and third embodiments, the temperature sensor may be, for example, a thermistor.

[0096] 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 divider resistor 44 and the voltage detection circuit 45, but may also be, for example, a high-voltage monitor IC. The high-voltage monitor IC is, for example, a one-package integrated circuit having a first terminal and a second terminal, which 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.

[0097] The configuration for detecting the drain current flowing through an ON switch SW is not limited to the Desat method. For example, a configuration may be used in which the drain current is detected based on the sense voltage, which is the potential difference across the sense resistor, and a sense resistor that generates a voltage drop corresponding to the current flowing through the sense terminal is provided for the sense terminal. In this case, the sense voltage only needs to be input to the non-inverting input terminal of the first comparator 66 in Figure 2, for example.

[0098] The configuration of the judgment circuit 70 and other components of the drive circuit Dr is not limited to analog circuits, but may also be implemented using software that includes a processor and memory for storing programs, and in which the programs stored by the processor are executed.

[0099] The power conversion circuit to which the drive device of this disclosure applies is not limited to an inverter, but may also be, for example, a DC-DC converter equipped with an up / down arm switch (e.g., a step-up / step-down DC-DC converter). [Explanation of symbols]

[0100] 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

1. In a switch drive device that drives switches (SW) of upper and lower arms connected in series, A parameter detection unit (60-65) detects either the terminal voltage (Vdesat), which is the voltage between the high-potential terminal and the low-potential terminal of the switch when the switch is in the ON state, or the current flowing between the high-potential terminal and the low-potential terminal of the switch when the switch is in the ON state. The current determination unit (66, 67) determines whether the value detected by the parameter detection unit exceeds the short-circuit threshold (Vthsc1), A voltage determination unit (68, 69) determines whether the gate voltage of the switch exceeds a mask threshold (Vthsc2) after a charging current is supplied to the gate of the switch, When the current determination unit determines that the value detected by the parameter detection unit exceeds the short-circuit threshold, and the voltage determination unit determines that the gate voltage of the switch exceeds the mask threshold, a signal output unit (70, 71; 51a, 51b, 52a, 52b, 71, 172) outputs an abnormal signal (Sgt) indicating that a short-circuit current is flowing through the switch at a time when the voltage determination unit has determined that the gate voltage of the switch exceeds the mask threshold and a filter period (Lf) has elapsed since then, A state detection unit (40, 41) for detecting the temperature (Tj) of the switch, Equipped with, A switch drive device that shortens the filter period when the detected value of the state detection unit is high compared to when the detected value of the state detection unit is low.

2. In a switch drive device that drives switches (SW) of upper and lower arms connected in series, A parameter detection unit (60-65) detects either the terminal voltage (Vdesat), which is the voltage between the high-potential terminal and the low-potential terminal of the switch when the switch is in the ON state, or the current flowing between the high-potential terminal and the low-potential terminal of the switch when the switch is in the ON state. The current determination unit (66, 67) determines whether the value detected by the parameter detection unit exceeds the short-circuit threshold (Vthsc1), A voltage determination unit (68, 69) determines whether the gate voltage of the switch exceeds a mask threshold (Vthsc2) after a charging current is supplied to the gate of the switch, When the current determination unit determines that the value detected by the parameter detection unit exceeds the short-circuit threshold, and the voltage determination unit determines that the gate voltage of the switch exceeds the mask threshold, a signal output unit (70, 71; 51a, 51b, 52a, 52b, 71, 172) outputs an abnormal signal (Sgt) indicating that a short-circuit current is flowing through the switch at a time when the voltage determination unit has determined that the gate voltage of the switch exceeds the mask threshold and a filter period (Lf) has elapsed since then, A state detection unit (44, 45) detects the terminal voltage (VHr), which is the voltage between the high-potential terminal and the low-potential terminal of the switch, Equipped with, When the detected value of the state detection unit is high, the filter period is shortened compared to when the detected value of the state detection unit is low. A switch drive device wherein the mask threshold is greater than or equal to the Miller voltage of the switch and less than the power supply voltage supplied to the gate of the switch.

3. The current determination unit outputs a binary logic signal as the result of determining whether the current detected value of the parameter detection unit exceeds the short-circuit threshold. The voltage determination unit outputs a binary logic signal as the result of determining whether the current gate voltage of the switch exceeds the mask threshold. The signal output unit is, The circuit (70) has a determination circuit that delays the logic signal output from the voltage determination unit by the filter period and outputs it, Based on the logic signal output from the determination circuit and the logic signal from the current determination unit, the abnormality signal is output. The switch drive device according to claim 1 or 2, wherein when the detected value of the state detection unit is high, the filter period is shortened compared to when the detected value of the state detection unit is low.

4. The current determination unit outputs a binary logic signal as the result of determining whether the current detected value of the parameter detection unit exceeds the short-circuit threshold. The signal output section has filter circuits (51a, 51b, 52a, 52b) that apply a low-pass filter to the gate voltage of the switch and output it. The voltage determination unit outputs a binary logic signal as the determination result of whether or not the gate voltage that has undergone the low-pass filter processing in the filter circuit exceeds the mask threshold. The signal output unit is, When the detected value of the state detection unit is high, the filter period is shortened by making the time constant of the low-pass filter processing smaller than when the detected value of the state detection unit is low. A switch drive device according to claim 1 or 2, which outputs the abnormal signal based on the logic signal of the voltage determination unit and the logic signal of the current determination unit.

5. Equipped with a switch protection unit (23), The switch drive device according to claim 1 or 2, wherein the switch protection unit, upon receiving the abnormal signal, switches the drive signal to the switch to an off command.

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