JP2014155412A - Motor Drive circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that, in a motor drive circuit in which a motor is provided, a first switching element and a second switching element are provided and a gate driver circuit is provided which generates a drive signal for driving the first switching element and the second switching element, a malfunction may occur in the gate driver circuit sometimes and an overcurrent may flow sometimes by simultaneously turning on the first switching element and the second switching element.SOLUTION: A short-circuit protection circuit (7) has a function for automatically turning off a second switching element (5) when an ON signal of the first switching element (4) is outputted from a gate driver circuit (IC) (6). The short-circuit prevention circuit (7) also has a function for stopping a malfunction by powering off the gate driver circuit (IC) (6) when the malfunction occurs in the gate driver circuit (IC) (6).

Description

  The present invention relates to a motor drive circuit, and more particularly to a motor drive circuit that shuts off the power supply of the gate driver circuit when the gate driver circuit malfunctions.

Conventionally, for example, in a motor drive circuit mounted on an electric vehicle, an overcurrent or overheat signal is output to a control means (CPU), and an output current is reduced by the control means (CPU), or an overcurrent, An overheat signal is detected to cut off the transistor drive voltage.
Such a motor drive circuit is provided with a gate driver circuit (IC) (LSI: integrated circuit). This gate driver circuit has an inverter function that changes the voltage while switching transistors (FET, IGBT, etc.), and switches to a voltage that can drive the transistor in response to a switching instruction from the control means (CPU). Output a signal.

  Conventionally, as shown in FIG. 3, the inverter circuit 102 for driving the traction motor 101 is a technique for a DC motor driving circuit such as an electric vehicle, and in particular, a gate driver circuit (IC) 103 and a control means (CPU). ) 104 is used to change the motor voltage by switching the transistors (FET, IGBT, etc.) T1 to T6, and there is a structure for preventing a short circuit of the switching element.

As shown in FIG. 4, in the gate driver circuit 201, when driving a high-side FET (corresponding to the first switching element), an ON / OFF signal is input from the control means (CPU) to the HIN 202. The In response to the response, a pulse signal is generated from the pulse oscillator 203. The RS latch circuit 204 receives this pulse signal and fixes the output. In response to the response, the HO 205 outputs a signal for driving the high-side FET (corresponding to the first switching element).
On the other hand, in driving a low-side FET (corresponding to a second switching element), an ON / OFF signal is input to the LIN 206 from the control means (CPU). A signal for driving the low-side FET (corresponding to the second switching element) is output from the LO 208 according to the response via the delay circuit 207.
When the output of the RS latch circuit 204 is fixed to “H” due to a malfunction of the pulse oscillator 203 or some electrical noise in the drive portion of the high-side FET (corresponding to the first switching element). Regardless of the input of the gate driver circuit 201, the high-side FET (corresponding to the first switching element) is kept on.
In order to release such unintended output fixing by the RS latch circuit 204, it is effective to once shut off the power supply to the gate driver circuit 201.
Furthermore, there are the following prior art documents as such a motor drive circuit.

Japanese Patent No. 4556906

  The gate driver and the motor driving device including the gate driver according to Patent Document 1 control the conduction / cutoff current of the power transistors connected in series, and prevent an increase in the gate voltage during switching. This prevents a short circuit of the power transistors connected in series.

However, in the conventional motor drive circuit, the gate driver circuit malfunctions, and the high-side FET (corresponding to the first switching element) and the low-side FET (corresponding to the second switching element) are simultaneously turned on. As a result, a short-circuit current (overcurrent) is caused to flow, leading to a failure such as damage to the transistor.
As countermeasures to solve such problems, a circuit structure that detects an overcurrent at the output stage of the transistor and shuts off the output of the gate driver circuit, or a circuit structure that prevents upper and lower ON signals from entering the input stage. There are things.
However, since the signals at the input stage and the output stage of the gate driver circuit are cut off, the gate driver circuit continues to be cut off when the gate driver circuit malfunctions, and there is a problem that the switching function continues to stop.

  Therefore, the present invention has been made in view of the above problems, and when the gate driver circuit malfunctions, the motor drive capable of shutting down the gate driver circuit power supply and stopping the malfunction of the gate driver circuit. An object is to provide a circuit.

  In order to achieve the above object, the present invention provides a motor, a first switching element and a second switching element, and drives the first switching element and the second switching element. In the motor drive circuit provided with the gate driver circuit for generating the drive signal, when the on signal of the first switching element is output from the gate driver circuit, the second switching element is automatically turned off. A short circuit protection circuit having a function is provided.

  According to the present invention, when the gate driver circuit malfunctions, the power supply of the gate driver circuit can be cut off and the malfunction of the gate driver circuit can be stopped.

FIG. 1 is a system configuration diagram of a motor drive circuit. Example 1 FIG. 2 is a system configuration diagram of the motor drive circuit. (Example 2) FIG. 3 is a system configuration diagram of the traction motor and the inverter circuit. (Conventional example 1) FIG. 4 is a system configuration diagram of the gate driver circuit. (Conventional example 2)

  The present invention realizes the purpose of shutting down the power supply of the gate driver circuit and stopping the malfunction of the gate driver circuit when the gate driver circuit malfunctions, without simultaneously turning on two switching elements. .

FIG. 1 shows Embodiment 1 of the present invention.
As shown in FIG. 1, a motor 1 for driving the electric vehicle and a motor drive circuit 2 for driving the motor 1 are mounted on the electric vehicle.
This motor drive circuit 2 includes a motor drive power supply (battery) 3 that supplies power to the motor 1, a first switching element 4, a second switching element 5, a gate driver circuit (IC) 6, and a short circuit. And a protection circuit 7.
The first switching element 4 is a transistor and is a high side FET.
The second switching element 5 is a transistor and is a low-side FET.
The gate driver circuit (IC) 6 is a field effect transistor, and is composed of an integrated circuit (LSI).

The motor drive power supply 3 includes a first line 9 connected to the motor 1 from the plus terminal via the first connection portion 8, and a second line 10 connected to the motor 1 from the minus terminal via the first connection portion 8. And are connected.
The first switching element 4 is interposed in the middle of the first line 9 and includes a gate (G), a source (S), and a drain (D). The drain (D) of the first switching element 4 is connected to the first line 9 on the plus terminal side of the motor driving power source 3. The source (S) of the first switching element 4 is connected to the first line 9 on the first connection portion 8 side.
The second switching element 5 is interposed in the middle of the second line 10 and includes a gate (G), a source (S), and a drain (D). The source (S) of the second switching element 5 is connected to the second line 10 on the negative terminal side of the motor driving power source 3. The drain (D) of the second switching element 5 is connected to the second line 10 on the first connection portion 8 side.

The gate driver circuit (IC) 6 generates a drive signal for driving the first switching element 4 and the second switching element 5.
The gate driver circuit (IC) 6 is connected to the first connection portion 8 by a third line 11 passing through the short circuit protection circuit 7.
The gate driver circuit (IC) 6 is connected to the gate (G) of the first switching element 4 by a fourth line 12 that passes through the short circuit protection circuit 7, and a fifth line 13 that passes through the short circuit protection circuit 7. To the gate (G) of the second switching element 5.
The gate driver circuit (IC) 6 is connected to a circuit (IC) power supply 15 by a sixth line 14 that passes through the short circuit protection circuit 7.
The gate driver circuit (IC) 6 is connected to the second connection portion 17 of the second line 10 by a seventh line 16 that passes through the short-circuit protection circuit 7. In addition, a ground (GND) 18 is connected to the second connection portion 17.

In the short-circuit protection circuit 7, a first resistor (high side gate resistor) 19 is interposed in the middle of the fourth line 12, and a second resistor (low side gate resistor) is placed in the middle of the fifth line 13. 20 is interposed, and a third resistor 21 is interposed in the middle of the sixth line 14.
In the short circuit protection circuit 7, a short circuit preventing switching element 22 is disposed between the third line 11 and the fourth line 12. The short-circuit preventing switching element 22 includes a gate (G), a source (S), and a drain (D). The gate (G) of the short-circuit prevention switching element 22 is connected to the third connection portion 23 of the third line 11. The source (S) of the short-circuit prevention switching element 22 is connected to the fourth connection portion 24 of the fourth line 12 between the first resistor 19 and the gate (G) of the first switching element 4.
Further, in the short-circuit protection circuit 7, a power cutoff switching element 25 is disposed between the sixth line 14 and the seventh line 16. The power cutoff switching element 25 includes a gate (G), a source (S), and a drain (D). The drain (D) of the power cutoff switching element 25 is connected to the fifth connection portion 26 of the sixth line 14 between the gate driver circuit (IC) 6 and the third resistor 21. The source (S) of the power shut-off switching element 25 is connected to the sixth connection portion 28 of the seventh line 16 by the eighth line 27.
A comparator 30 is connected to the gate (G) of the power shut-off switching element 25 by a ninth line 29. The plus terminal of the comparator 30 is connected to the seventh connection portion 32 of the fifth line 13 between the gate driver circuit (IC) 6 and the second resistor 20 by the tenth line 31. The negative terminal of the comparator 30 is connected to the eighth connection portion 34 of the fifth line 13 between the second resistor 20 and the gate (G) of the second switching element 5 by the eleventh line 33.

In the short circuit protection circuit 7, a bipolar transistor (BPT) 35 is disposed between the fifth line 13 and the seventh line 16. The bipolar transistor 35 includes a base (B), a collector (C), and an emitter (E). The base (B) of the bipolar transistor 35 is connected to the drain (D) of the short-circuit preventing switching element 22 by a twelfth line 36. The collector (C) of the bipolar transistor 35 is connected to the eighth connection portion 34 of the fifth line 13. The emitter (E) of the bipolar transistor 35 is connected to the ninth connection part 37 of the seventh line 16 between the second connection part 17 and the sixth connection part 28.

In this motor drive circuit 2, the source (S) of the short-circuit prevention switching element 22 is connected between the gate driver circuit (IC) 6 and the gate (G) of the first switching element 4, so that the short-circuit prevention switching is performed. The drain (D) of the element 22 and the base (B) of the bipolar transistor 35 are connected, and the gate (G) of the short-circuit prevention switching element 22 is connected to the source (S) of the first switching element 4. The collector (C) of the bipolar transistor 35 is connected to the gate (G) of the second switching element 5, and the emitter (E) of the bipolar transistor 35 is connected to the ground (GND) 18.
With this structure, when a voltage for turning on the first switching element 4 is output from the gate driver circuit (IC) 6, the short-circuit preventing switching element 22 is turned on. A current flows between the source (S) and the drain (D), and the bipolar transistor 35 is turned on. At this time, even if a voltage for turning on the second switching element 5 is output, the gate (G) of the second switching element 5 is connected to the ground (GND) 18 through the bipolar transistor 35. The upper and lower short-circuits prevent the voltage from being simultaneously applied to the gate (G) and the source (S) of the first switching element 4 and the second switching element 5 without the second switching element 5 being turned on. It functions as a prevention circuit.

In the motor driving circuit 2, both ends of the second resistor 20 are connected to the comparator 30.
With such a structure, when a short circuit signal for turning on the first switching element 4 and the second switching element 5 is output from the gate driver circuit (IC) 6, the gate (G) of the second switching element 5 is Since it is connected to the ground (GND) 18, a voltage is generated across the second resistor 20. As a result, the output of the comparator 30 becomes “H”. That is, the output of the comparator 30 is determined based on the presence or absence of a voltage drop of the second resistor 20.

Further, in the motor drive circuit 2, a third resistor 21 is disposed between the circuit (IC) power source 15 used for the power source of the gate driver circuit (IC) 6 and the gate driver circuit (IC) 6. The third resistor 21 and the gate driver circuit (IC) 6 are branched to connect the drain (D) of the power shut-off switching element 25. The source (S) of the power cutoff switching element 25 is connected to the ground (GND) 18, and the output of the comparator 30 is connected to the gate (G) of the power cutoff switching element 25.
With this structure, when a short circuit signal for turning on the first switching element 4 and the second switching element 5 is output from the gate driver circuit (IC) 6, the power supply voltage of the gate driver circuit (IC) 6 is reduced. It can be dropped to the ground (GND) 18. At this time, the gate driver circuit (IC) 6 stops its operation and the output is simultaneously cut off, so that the short circuit signal stops. For this reason, the switching element 22 for short-circuit prevention and the bipolar transistor 35 are also turned off, and the output from the comparator 30 becomes “L”. Then, the power cutoff switching element 25 is turned off, the power to the gate driver circuit (IC) 6 is turned on again, and the gate driver circuit (IC) 6 is restarted.

As a result, in this motor drive circuit 2, the short circuit protection circuit 7 automatically turns off the second switching element 5 when the ON signal of the first switching element 4 is output from the gate driver circuit (IC) 6. It has a function to make.
As a result, the two switching elements 4 and 5 are not turned on at the same time, so that the motor drive circuit 2 can be prevented from being short-circuited.
The short circuit protection circuit 7 has a function of detecting a short circuit signal output from the gate driver circuit (IC) 6 and a function of shutting off the power source of the gate driver circuit (IC) 6 in response to the generation of the short circuit signal. Prepare.
Thereby, when the gate driver circuit (IC) 6 outputs a short circuit signal, the power supply of the gate driver circuit (IC) 6 can be forcibly cut off, and the output of the short circuit signal can be stopped. When the output of the short circuit signal is stopped, the gate driver circuit (IC) 6 can be temporarily stopped completely, and then the gate driver circuit (IC) 6 can be restarted.

That is, in this embodiment, when the gate driver circuit (IC) 6 which is a component of the motor driving circuit 2 malfunctions, the malfunction is detected by shutting off the power supply of the gate driver circuit (IC) 6 by detecting the malfunction. Can be stopped. Further, a short circuit signal from the gate driver circuit 6 that causes overcurrent is shut off (off) in advance (the bipolar transistor 35 is turned on and the gate (G) of the second switching element 5 is set to 0 volt), A vertical short circuit can be prevented.
Therefore, it is a circuit structure in which a short circuit does not occur even if a short circuit signal is output, rather than a disconnection after an overcurrent caused by a short circuit signal or the like as in the known technique described in the above cited reference, It is possible to shut off the short circuit signal by shutting off the power supply of the gate driver circuit (IC) 6 that is provided.
Further, the short circuit signal is detected from the voltage drop of the second resistor 20. Thus, generally, the second resistor 20 is a circuit necessary for the motor drive circuit 2 and can detect a short circuit without adding a new circuit, thereby simplifying the structure.

FIG. 2 shows a second embodiment of the present invention.
In the second embodiment, portions that perform the same functions as those of the first embodiment will be described with the same reference numerals.
The features of the second embodiment are as follows. That is, as shown in FIG. 2, in the structure of the motor drive circuit 2 of FIG. 1, the short circuit protection circuit 7 is used as the first short circuit protection circuit 41, and the second short circuit protection circuit 42 and the control means (CPU) 43. And are newly added.
The second short circuit protection circuit 42 is disposed between the gate driver circuit (IC) 6 and the control means (CPU) 43.
The gate driver circuit (IC) 6 and the control means (CPU) 43 are connected by a thirteenth line 44 and a fourteenth line 45 that pass through the second short circuit protection circuit 42.
The control means (CPU) 43 is connected to the tenth connection portion 47 of the sixth line 14 before the circuit (IC) power supply 15 by the fifteenth line 46 passing through the second short circuit protection circuit 42.
The control means (CPU) 43 is connected to the eleventh connection portion 49 of the seventh line 16 by a sixteenth line 48 passing through the second short circuit protection circuit 42.

The control means (CPU) 43 gives an instruction to drive control of the first switching element 4 and the second switching element 5 to the gate driver circuit (IC) 6.
The second short circuit protection circuit 42 has a function of detecting a short circuit signal output from the control means (CPU) 43 and a function of shutting off the power supply of the control means (CPU) 43 in response to the generation of the short circuit signal. .
As a result, a malfunction from the control means (CPU) 43 is detected and the power supply to the control means (CPU) 43 is shut off, causing the control means (CPU) 43 to malfunction and the gate driver circuit (IC) 6. It is also possible to prevent a short circuit signal from being sent to the terminal.
As a result, in the structure according to the second embodiment, when the malfunction of the control means (CPU) 43 is detected, the power of the control means (CPU) 43 is forcibly cut off, so that the gate driver circuit (IC) 6 The short circuit signal can be stopped and the motor drive circuit 2 can be prevented from being short-circuited.

  The motor drive circuit according to the present invention can be applied to various electric vehicles.

DESCRIPTION OF SYMBOLS 1 Motor 2 Motor drive circuit 3 Motor drive power supply (battery)
4 First switching element (high-side FET)
5 Second switching element (low-side FET)
6 Gate driver circuit (IC)
7 Short-circuit protection circuit 15 Power supply for circuit (IC) 18 Ground (GND)
19 First resistor (high-side gate resistor)
20 Second resistor (low-side gate resistor)
21 Third resistor 22 Short-circuit prevention switching element (FET)
25 Switching element for power shutdown (FET)
30 Comparator 35 Bipolar Transistor (BPT)
41 1st short circuit protection circuit 42 2nd short circuit protection circuit 43 Control means (CPU)

Claims (3)

  A motor drive circuit provided with a motor, provided with a first switching element and a second switching element, and provided with a gate driver circuit for generating a drive signal for driving the first switching element and the second switching element And a short-circuit protection circuit having a function of automatically turning off the second switching element when an ON signal of the first switching element is output from the gate driver circuit. Driving circuit.   The short circuit protection circuit includes a function of detecting a short circuit signal output from the gate driver circuit, and a function of shutting off a power source of the gate driver circuit in response to the generation of the short circuit signal. The motor drive circuit according to 1.   A gate driver circuit configured to provide a motor, provide a first switching element and a second switching element, and generate a drive signal for driving the first switching element and the second switching element; In a motor drive circuit provided with a control means for giving a command to execute drive control of the first switching element and the second switching element to the circuit, an ON signal of the first switching element is output from the gate driver circuit. Then, a first short-circuit protection circuit having a function of automatically turning off the second switching element is provided, a function of detecting a short-circuit signal output from the control means, and the occurrence of the short-circuit signal And a second short circuit protection circuit having a function of shutting off the power supply of the control means. Circuit.

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