JP2007124824A - Motor controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a motor controller which can avoid the burning of a switching element, when the grounding abnormality of a motor or short circuit abnormality between terminals occurs, precisely, using a simple configuration. <P>SOLUTION: This motor controller is equipped with a protection circuit 4 for normal rotation drive which switches off the first switching element, when a potential-difference-for-normal-rotation detecting circuit 6, which detects a high potential difference generation state where the potential difference between a power-side terminal T1s and a motor-side terminal T1d is larger than a prescribed voltage, detects a high potential difference generation state, in a state where a control means 3 is outputting an ON command to the first switching element SW1; and a protection circuit 5 for reverse rotation drive which switches off the third switching element when a potential-difference-for-reversal detecting circuit 7, which detects a high potential difference generation state where the potential difference between a power-side terminal T3s and a motor-side terminal T3d is larger than specified voltage, detects a high potential difference generation state, in a state where the control means 3 is outputting an ON command to the third switching element SW3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention includes a first switching element connected to the power supply side and the first terminal side for forward rotation of the motor, a second switching element connected to the ground side and the first terminal side of the motor, A third switching element connected to a power supply side and a second terminal side for reverse rotation of the motor; a fourth switching element connected to the ground side and the second terminal side of the motor; A rotation stop command state for outputting an off command to each of the switching element, the second switching element, the third switching element, and the fourth switching element; and the first switching element and the fourth switching element. A forward rotation driving command state that outputs an on command to the second switching element and outputs an off command to the second switching element and the third switching element, and the second Control means capable of switching to a reverse drive command state for outputting an ON command to the switching element and the third switching element and outputting an OFF command to the first switching element and the fourth switching element; The present invention relates to a motor control device provided with.

  As a conventional example of the motor control device, an abnormality (hereinafter referred to as a ground fault abnormality) in which the first terminal or the second terminal of the motor is connected to the ground side in the forward drive command state or the reverse drive command state. In some cases, when an abnormality in which the first terminal and the second terminal of the motor are connected (hereinafter referred to as a short circuit abnormality between terminals) occurs, a protection means is provided to prevent burning of the switching element (for example, (See Patent Document 1 and Patent Document 2.)

  In other words, when the control means is in the forward rotation driving command state, that is, the control means commands the first switching element to turn on, whereby the first switching element is turned on. The motor is in a normal rotation drive state. In this state, a voltage close to the power supply voltage is applied between the first terminal and the second terminal of the motor, and the on-resistance of the switching element is between the power supply side terminal and the motor side terminal of the first switching element. A slight potential difference due to is not generated.

  When the control means is in the normal rotation drive command state, for example, if a ground fault abnormality occurs at the first terminal of the motor, one end of the first switching element is on the power supply side and the other end is The potential difference between both terminals of the first switching element is a voltage close to the power supply voltage, and a voltage close to the power supply voltage is applied to the first switching element (high potential difference generation state). An overcurrent flows through the first switching element.

  In addition, when the control means is in the normal rotation drive command state, for example, if a short circuit between the first terminal and the second terminal of the motor causes a short circuit between the terminals, As in the case where the ground fault has occurred in the first terminal, one end of the first switching element is connected to the power supply side, and the other end is connected to the ground side via the fourth switching element in the ON state. When the potential difference between the power supply side terminal of the first switching element and the ground side terminal of the fourth switching element is a voltage close to the power supply voltage, and the magnitudes of the on-resistances of both elements are substantially equal, About half of the power supply voltage is applied to each of the switching elements (high potential difference generation state), and an overcurrent flows through the first switching element and the fourth switching element.

  The conventional motor control device is provided with voltage detection means and current detection means for detecting a high potential difference occurrence state when a high potential difference occurrence state as described above is provided. When a current flows, the control means configured by a microcomputer activates the protection means based on the detection information of the voltage detection means and the current detection means to cut off the overcurrent.

  Incidentally, the motor control device of Patent Document 1 includes a protection circuit 4 as protection means, a potential difference between the potential of the power supply side terminal in the first switching element and the potential of the motor side terminal, and the power supply side terminal in the third switching element. The first voltage detecting means 7 and the second voltage detecting means 8 as voltage detecting means for detecting a potential difference between the potential of the motor side terminal and the potential of the motor side terminal as a voltage value, and the voltage values detected by these voltage detecting means are There is provided a microcomputer 6 that judges whether it is normal or abnormal and outputs a control signal to the protection circuit 4, and a ground fault abnormality or a short circuit abnormality between terminals occurs and a high potential difference occurs and the switching element When an overcurrent flows, the microcomputer 6 determines that the voltage detected by the voltage detection means is abnormal, outputs a control signal, activates the protection circuit 4, and flows to the switching element. While it cuts off the overcurrent.

  In addition, the motor control device disclosed in Patent Document 2 includes a fail relay 16 as protection means, a first current detection circuit 15 as current detection means for detecting current flowing through the switching element, and detection by the first current detection circuit 15. And a control device 5 that determines whether the current value is normal or abnormal and outputs a control signal to the fail relay 16. When the overcurrent flows through the switching element, the control device 5 determines that the current detected by the first current detection circuit 15 is abnormal, outputs a control signal, and activates the fail relay 16. The overcurrent flowing through the switching element is cut off.

Japanese Patent Laid-Open No. 11-341851 Japanese Patent Laid-Open No. 04-046867

However, with the above-described conventional configuration, the control means outputs a control signal based on the detection information of the voltage detection means and the current detection means, and activates the protection means to stop the current flowing through the switching element. Since a considerable time corresponding to the processing time of the control means is required in addition to the response time of the hard circuit, there is a problem in that burning of the switching element may not be avoided depending on the processing speed of the control means.
Further, in the conventional configuration, it is necessary to separately provide protection means in the motor control device, and since the protection means needs to be configured so as to be able to cut off the overcurrent flowing through the switching element, the motor control device is complicated. There was an inconvenience that it would be large.

  The present invention has been made in view of the above circumstances, and its purpose is to accurately avoid burning of the switching element when a ground fault abnormality of the motor or a short circuit abnormality between terminals occurs. It is in the point which provides the motor control apparatus which can do.

The first feature of the motor control device of the present invention is:
A first switching element connected to the power source side and the first terminal side for forward rotation of the motor;
A second switching element connected to the ground side and the first terminal side of the motor;
A third switching element connected to the power supply side and a second terminal side for reverse rotation of the motor;
A fourth switching element connected to the ground side and the second terminal side of the motor;
A rotation stop command state that outputs an off command to each of the first switching element, the second switching element, the third switching element, and the fourth switching element, the first switching element, and the fourth switching element. A forward drive command state for outputting an on command to the switching element and outputting an off command to the second switching element and the third switching element; and the second switching element and the third Motor control provided with control means capable of switching to a reverse drive command state for outputting an ON command to the switching element and outputting an OFF command to the first switching element and the fourth switching element In the device
A forward potential difference detection circuit for detecting a high potential difference occurrence state in which the potential difference between the potential of the power supply side terminal and the potential of the motor side terminal in the first switching element is greater than a predetermined voltage;
A reverse potential difference detection circuit for detecting a high potential difference occurrence state in which the potential difference between the potential of the power supply side terminal and the potential of the motor side terminal in the third switching element is greater than a predetermined voltage;
When the forward rotation potential difference detection circuit detects a high potential difference occurrence state in a state where the control means outputs an on command to the first switching element, the first switching element is forcibly turned off. A forward drive protection circuit;
In a state where the control means outputs an ON command to the third switching element, when the reverse potential difference detection circuit detects a high potential difference occurrence state, the third switching element is forcibly turned off. A reverse drive protection circuit is provided.

According to the first feature of the present invention, when the potential difference between the potential of the power supply side terminal and the potential of the motor side terminal in the first switching element is in a high potential difference generation state larger than a predetermined voltage, the forward rotation potential difference detection circuit is in the high potential difference generation state. Thus, the forward drive protection circuit is activated and the first switching element is forcibly turned off. Therefore, when the motor is driven forward, a ground fault occurs at the first terminal of the motor. When an abnormality occurs or when a short-circuit abnormality occurs between the first terminal and the second terminal, the first switching is performed when the response time of the forward rotation potential difference detection circuit and the forward rotation drive protection circuit elapses. The element is turned off, and the overcurrent flowing through the first switching element is interrupted.
Similarly, when a ground fault abnormality occurs in the second terminal of the motor while the motor is driven in reverse rotation, or when a short-circuit abnormality between terminals occurs between the first terminal and the second terminal, reverse rotation is performed. When the response times of the potential difference detection circuit and the reverse drive protection circuit have elapsed, the third switching element is turned off, and the overcurrent flowing through the third switching element is interrupted.

That is, the time during which the overcurrent flows through the first switching element and the third switching element is the response time of the electronic circuit such as the forward rotation potential difference detection circuit, the forward rotation drive protection circuit, the reverse rotation potential difference detection circuit, and the reverse rotation drive protection circuit. Accordingly, the overcurrent flowing through the first switching element or the third switching element can be immediately stopped without waiting for the processing time of the program executed by the control means to elapse as in the conventional case. Further, since the overcurrent flowing through the switching element is cut off by turning the switching element off, it is not necessary to separately provide protection means configured to cut off the overcurrent.
Therefore, the present invention has led to a motor control device capable of accurately avoiding burning of the switching element when a motor ground fault or a short circuit between terminals occurs.

The second feature of the present invention is the first feature of the present invention,
The forward drive protection circuit is
While the control means outputs an ON command to the first switching element, the control means enters a latch state for holding the first switching element in an OFF state, and the control means outputs an ON command to the first switching element. Is not output, and the first switching element is configured to be in a non-latching state that releases the hold of the off state,
The reverse drive protection circuit comprises:
While the control means outputs an ON command to the third switching element, the control means enters a latch state for holding the third switching element in the OFF state, and the control means sends an ON command to the third switching element. Is not output, the third switching element is brought into a non-latching state in which the holding of the OFF state is released.

According to the 2nd characteristic of this invention, in addition to the effect | action similar to the 1st characteristic of this invention, there exist the following effects.
While the control means outputs the ON command to the first switching element, the forward drive protection circuit is in a latch state that holds the first switching element in the OFF state. For example, a ground fault occurs at the motor terminal. When the control means switches from the rotation stop command state to the normal rotation drive command state in a state where an abnormality or a short circuit abnormality has occurred, the normal rotation drive protection circuit forcibly turns off the first switching element, Hold that state. Further, for example, when a ground fault abnormality or a short circuit abnormality occurs at the motor terminal when the control means is in the normal rotation driving command state, the normal rotation driving protection circuit forcibly turns off the first switching element. , Hold that state. Therefore, after the first switching element is turned off by the forward drive protection circuit, the ground fault abnormality or the short circuit abnormality may be intermittently recovered by intermittently eliminating the cause of the abnormality. However, since the first switching element is held in the off state based on the ground fault abnormality or the short circuit abnormality that occurs first, the first switching element is not turned on.

  When the control means stops outputting the on command to the first switching element, the first switching element is brought into a non-latching state for releasing the hold of the off state. However, since the control means outputs the off command, the first switching element Remains off. In other words, the first switching element that is turned off based on the ground fault abnormality or the short circuit abnormality that is first generated continues to be turned off before and after the control unit does not output the on command to the first switching element.

  Thus, according to the second feature of the present invention, the first switching element that is turned on by the on command output from the control means is once latched off by the forward drive protection circuit. While the forward rotation driving protection circuit is activated, the control means is held in an off state while the on command is output. When the control means stops outputting the on command, the forward rotation driving protection circuit is in a non-latching state. The first switching element is turned off as it is based on the off command output from the control means.

  As for the third switching element, similarly to the above-described change between the on state and the off state of the first switching element, the third switching element that is turned on by the on command output by the control means is a reverse drive protection circuit. When the control means outputs the ON command, it is held in the OFF state by the operation of the latched reverse rotation drive protection circuit. When the control means stops outputting the ON command, the reverse drive is performed. The protection circuit is in a non-latching state, but the third switching element is turned off as it is based on the off command output from the control means.

  As described above, according to the second feature of the present invention, even if the ground fault abnormality or the short circuit abnormality may be intermittently recovered due to poor contact or the like, Based on this, since the first switching element or the third switching element is held in the off state, the first switching element or the third switching element is not turned on. Therefore, even if a ground fault abnormality or a terminal short-circuit abnormality occurs intermittently due to poor contact or the like, it is possible to prevent intermittent overcurrent from flowing through the switching element. Means suitable for doing so are obtained.

The third feature of the present invention is the second feature of the present invention,
The forward drive protection circuit is
A forward rotation delay circuit configured to delay the time when the control means switches to the forward drive command state from the reverse drive command state and to enter the latch state;
The reverse drive protection circuit comprises:
The control means includes a reverse-rotation delay circuit that delays the time when the control state is changed to the latch state in accordance with switching from the forward drive command state to the reverse drive command state.

According to the 3rd characteristic of this invention, in addition to the effect | action similar to the 2nd characteristic of this invention, there exist the following effects.
When the control means switches from the reverse drive command state to the forward drive command state, the forward potential difference detection circuit is increased by the back electromotive force due to the inertia of the motor immediately before the first switching element is turned on. The potential difference occurrence state is detected. When the first switching element is turned on by the ON command output from the control means, no high potential difference is generated between both terminals of the first switching element, so the forward potential difference detection circuit detects the high potential difference occurrence state. No longer.
On the other hand, when the forward rotation potential difference detection circuit detects a high potential difference occurrence state in a state where the control means outputs an ON command to the first switching element, the forward drive protection circuit turns the first switching element off. Although the latch state is maintained, since the forward rotation delay circuit is provided, the time from when the control means outputs an ON command to the first switching element until the forward drive protection circuit enters the latch state becomes longer. .
Therefore, the forward rotation potential difference detection circuit does not detect the high potential difference occurrence state until the forward rotation drive protection circuit is in the latch state, and thus the forward rotation drive protection circuit turns the first switching element off. Thus, it is possible to avoid the latching state.

  Similarly, when the control means switches from the forward drive command state to the reverse drive command state, the reverse potential difference detection circuit is in a high potential difference generation state until the reverse drive protection circuit is in the latch state. Therefore, the reverse drive protection circuit can be prevented from being in the latched state with the third switching element in the OFF state.

  Thus, according to the third feature of the present invention, when the control means switches from the reverse drive command state to the forward drive command state, or from the forward drive command state to the reverse drive command state. In addition, the forward drive protection circuit and the reverse drive protection circuit are prevented from operating even when the motor terminal ground fault abnormality or short circuit abnormality has not occurred, and the motor drive direction is switched. Can be appropriately performed, and therefore, means suitable for carrying out the present invention can be obtained.

  According to a fourth feature of the present invention, in any one of the first to third features of the present invention, the control means detects whether the forward potential difference detection circuit and the reverse potential difference detection circuit detect a high potential difference occurrence state. In other words, a detection signal indicating whether or not the signal is input is input.

According to the 4th characteristic of this invention, in addition to the effect | action similar to any one of the 1st-3rd characteristic of this invention, there exist the following effects.
Since the detection signal indicating whether the forward potential difference detection circuit and the reverse potential difference detection circuit are detecting the high potential difference occurrence state is input to the control means, the control means is based on the input detection signal, An abnormality of the motor terminal can be detected.

In other words, if the control means is in the rotation stop command state and all of the first to fourth switching elements are in the off state, if a ground fault abnormality occurs in the first terminal or the second terminal of the motor, The diversion potential difference detection circuit detects a high potential difference occurrence state.
Further, if the control means is in the rotation stop command state and all of the first to fourth switching elements are in the OFF state, if there is a ground fault abnormality in the first terminal or the second terminal of the motor M, the reverse rotation The potential difference detection circuit detects a high potential difference occurrence state.
In other words, if the control means is in the rotation stop command state and all of the first to fourth switching elements are in the OFF state, even if a ground fault abnormality occurs at the first terminal of the motor, the ground fault occurs at the second terminal. Even when an abnormality occurs, both the forward potential difference detection circuit and the reverse potential difference detection circuit detect the high potential difference occurrence state. Therefore, the control means detects a ground fault abnormality in the first terminal or the second terminal of the motor based on the detection state of the forward rotation potential difference detection circuit and the reverse rotation potential difference detection circuit in the rotation stop command state. Can do.

  As described above, according to the fourth aspect of the present invention, the control means uses the configuration for protecting the switching element to detect the ground fault abnormality of the motor terminal in advance before driving the motor in the normal rotation direction or the reverse rotation direction. Therefore, a highly functional motor control device can be obtained while suppressing an increase in cost.

  Embodiments of a motor control device according to the present invention will be described below with reference to the drawings. This motor control device drives a motor used for electronic control of the throttle valve of an engine mounted on a work machine such as a construction machine or a combine machine, and adopts a motor drive control system using an H-bridge circuit. Yes.

  As shown in FIG. 1, the H bridge circuit 1 of the motor control device includes a first switch SW1 and a third switch SW3 as switching elements connected to the power supply side, which are composed of p-channel MOS-FETs, and are grounded. The second switch SW2 and the fourth switch SW4 as switching elements connected to the side are constituted by n-channel MOS-FETs.

  The connection state of the high-side switch connected to the power supply side will be described. As shown in FIG. 1, the source terminal T1s of the first switch SW1 and the source terminal T3s of the third switch SW3 are both connected to the power supply 2. The drain terminal T1d of the first switch SW1 is connected to the first terminal Tm1 of the motor M, and the drain terminal T3d of the third switch SW3 is connected to the second terminal Tm2 of the motor M. Yes.

  The connection state of the low-side switch connected to the ground side will be described. As shown in FIG. 1, the source terminal T2s of the second switch SW2 and the source terminal T4s of the fourth switch SW4 are both grounded. The drain terminal T2d of the second switch SW2 is connected to the first terminal Tm1 of the motor M, and the drain terminal T4d of the fourth switch SW4 is connected to the second terminal Tm2 of the motor M.

  Gate terminals T1g to T4g of the first switch SW1 to the fourth switch SW4 are connected to a microcomputer 3 as control means via driver circuits D1 to D4, which will be described later, and according to an ON command and an OFF command output by the microcomputer 3 Each MOS-FET is switched between an on state and an off state.

  The microcomputer 3 operates in an active high state in which an on command is output as a high level signal and an off command is output as a low level signal. However, the microcomputer 3 operates on the high side composed of p-channel MOS-FETs. Active low signals are input to the gate terminals T1g and T3g of the switches SW1 and SW3 by the high-side driver circuits D1 and D3.

  The high-side driver circuits on the forward rotation side and the reverse rotation side of the motor control device have the same configuration. Specifically, as shown in FIG. 3, pnp junction bipolar transistors Tr1, Tr3, etc. It consists of The operation of the driver circuit when the microcomputer 3 outputs an ON command to the first switch SW1 to the fourth switch SW4 will be described below.

  For example, when the microcomputer 3 outputs an ON command by a high level signal to the first switch SW1, the transistor Tr1 of the high-side driver circuit D1 on the normal rotation side is turned on, and the gate terminal T1g of the first switch SW1 is connected to the ground line. Since the potential is more than the gate threshold voltage of the MOS-FET between the gate terminal T1g and the source terminal T1s connected to the power supply line E, the first switch SW1 is turned on. become.

  Further, when the microcomputer 3 outputs an ON command based on the high level signal to the third switch SW3, the transistor Tr3 of the high-side driver circuit D3 on the reverse side is turned on, and the gate terminal T3g of the third switch SW3 is connected to the ground line G. Since the potential difference equal to or higher than the gate threshold voltage of the MOS-FET is generated between the gate terminal T3g and the source terminal T3s connected to the power supply line E, the third switch SW3 is turned on. Become.

  On the other hand, the ON command output from the microcomputer 3 to the fourth switch SW4 operates the low-side driver circuit D4 on the forward rotation side to switch the gate terminal T4g of the fourth switch SW4 to the state connected to the power supply line E. . As a result, a potential difference equal to or greater than the gate threshold voltage of the MOS-FET is generated between the source terminal T4s and the gate terminal T4g connected to the power supply line E, so that the fourth switch SW4 is turned on.

  Similarly, the ON command output from the microcomputer 3 to the second switch SW2 activates the low-side driver circuit D2 on the reverse side to switch the gate terminal T2g of the second switch SW2 to the state connected to the power supply line E. . As a result, a potential difference equal to or greater than the gate threshold voltage of the MOS-FET is generated between the source terminal T2s and the gate terminal T2g connected to the power supply line E, so that the second switch SW2 is turned on.

When the microcomputer 3 detects the forward rotation drive command F, the reverse rotation drive command R, and the rotation stop command N commanded by the host controller C, the microcomputer 3 enters a command state corresponding to these commands.
That is, when the microcomputer 3 detects the rotation stop command N, the microcomputer 3 enters the rotation stop command state Sn, and each of the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4. An off command is output. Accordingly, as shown in FIG. 2, all of the first switch SW1, the second switch SW2, the third switch SW3, and the fourth switch SW4 are turned off, so that the first terminal Tm1 of the motor M and the second switch No voltage is applied to the terminal Tm2, and the rotational driving force of the motor M is not generated.

  Further, when the microcomputer 3 detects the forward rotation drive command F, the microcomputer 3 enters the forward drive command state Sf2, outputs an ON command to the first switch SW1 and the fourth switch SW4, and the second switch SW2. And an OFF command is output with respect to 3rd switch SW3. As a result, as shown in FIG. 2, the first switch SW1 and the fourth switch SW4 are turned on, and the second switch SW2 and the third switch SW3 are turned off, so that the first terminal Tm1 of the motor M is The second terminal Tm2 of the motor M is connected to the ground line G via the on-state fourth switch SW4. Therefore, a voltage close to the power supply voltage is applied between the first terminal Tm1 and the second terminal Tm2 of the motor M, and the motor is driven to rotate forward.

  When the microcomputer 3 detects the reverse drive command R, the microcomputer 3 enters the reverse drive command state Sr2, outputs an ON command to the second switch SW2 and the third switch SW3, and outputs the first switch SW1 and the first switch SW1. An off command is output to the 4 switch SW4. As a result, as shown in FIG. 2, the second switch SW2 and the third switch SW3 are turned on, and the first switch SW1 and the fourth switch SW4 are turned off, so that the second terminal Tm2 of the motor M is The power supply line E is connected through the third switch SW3 in the on state, and the first terminal Tm1 of the motor M is connected to the ground line G through the second switch SW2 in the on state. Therefore, a voltage close to the power supply voltage is applied between the second terminal Tm2 and the first terminal Tm1 of the motor M, and the motor is driven in reverse.

  Although detailed description is avoided, when the rotational speed control of the motor M is performed by PWM control, if it is in the forward rotation driving state, the on / off switching is performed while controlling the on time and the off time of the fourth switch SW4, and the reverse rotation driving is performed. In this state, the on / off switching is performed while controlling the on time and off time of the second switch SW2. Therefore, in the normal rotation driving state, the normal rotation driving command state Sf2 and the normal rotation preparation command state Sf1. Repeatedly appear, and in the reverse drive state, the reverse drive command state Sr2 and the reverse preparation command state Sr1 appear repeatedly.

  In general, in a motor control device having an H-bridge circuit, when driving a motor that is driven in reverse rotation, or when driving a motor that is driving in reverse rotation, Through current across the low-side switch (in this embodiment, both the first switch SW1 and the second switch SW2 are turned on, or both the third switch SW3 and the fourth switch SW4 are turned on. So that all switching elements of the H-bridge are turned off so that the current that flows when the power supply side and the ground side are short-circuited via two switches does not flow. And it is designed to switch off state.

  The microcomputer 3 of the motor control device is configured to switch from the forward drive command state Sf2 to the reverse drive command state Sr2 and when switching from the reverse drive command state Sr2 to the forward drive command state Sf2. The command state sequentially changes in the directions indicated by the arrow A indicated by the solid line and the arrow B indicated by the dotted line in FIG. 2 to change the on / off states of the switches SW1 to SW4.

  For example, when the microcomputer 3 switches the motor M in the normal rotation driving state to the reverse rotation driving state, the microcomputer 3 temporarily passes through the normal rotation driving command state Sf2 to the normal rotation preparation command state Sf1. Then, the rotation stop command state Sn is entered. As a result, of the first switch SW1 and the fourth switch SW4 that are in the on state in the normal rotation drive command state Sf2, the fourth switch SW4 that is the low side switch is first switched to the off state, and then the high side switch The first switch SW1 is switched to the OFF state.

  Then, the microcomputer 3 changes from the rotation stop command state Sn to the reverse rotation preparation command state Sr1 through the reverse rotation preparation command state Sr1. As a result, of the second switch SW2 and the third switch SW3 that are in the off state in the rotation stop command state Sn, the third switch SW3 that is the high side switch is first switched on, and then the low side switch A certain second switch SW2 is turned on.

  When the motor M in the reverse drive state is switched to the normal drive state, the microcomputer 3 reverses the above-described change order and changes the command state from the reverse drive command state Sf2 to the forward drive command state Sf1. Accordingly, the on / off states of the switches SW1 to SW4 are switched.

  The H bridge circuit of the motor control device includes a forward drive protection circuit 4 and a reverse drive protection circuit 5 with a latch function to prevent the switches SW1 to SW4 from burning out and abnormal operation of the motor 3.

  The forward drive protection circuit 4 is configured such that the forward side source-drain voltage monitoring circuit 6 serving as the forward rotation potential difference detection circuit generates a high potential difference when the microcomputer 3 outputs an ON command to the first switch SW1. When the state is detected, the potential of the gate terminal T1g of the first switch SW1 composed of the p-channel MOS-FET is returned to the state pulled up to the high level, and the potential of the gate terminal T1g and the potential of the source terminal T1s are restored. The first switch SW1 is forcibly turned off by eliminating the potential difference.

  The forward-side source-drain voltage monitoring circuit 6 monitors a potential difference generated between the source terminal T1s and the drain terminal T1d in the first switch SW1. Regardless of the on / off state of the first switch SW1, when the high potential difference generation state in which a potential difference of a predetermined voltage or more is generated between the source terminal T1s and the drain terminal T1d, the normal-side source-drain voltage monitoring circuit 6 A potential difference occurrence state is detected.

  In the reverse drive protection circuit 5, the reverse source-drain voltage monitoring circuit 7 as the reverse potential difference detection circuit is in a high potential difference generation state when the microcomputer 3 outputs an ON command to the third switch SW3. When detected, the potential of the gate terminal T3g of the third switch SW3 composed of the p-channel MOS-FET is returned to the high level, and the potential difference between the potential of the gate terminal T3g and the potential of the source terminal T3s is obtained. Instead, the third switch SW3 is forcibly turned off.

  The reverse-side source-drain voltage monitoring circuit 7 monitors a potential difference generated between the source terminal T3s and the drain terminal T3d in the third switch SW3. Regardless of the on / off state of the third switch SW3, when the high potential difference generating state in which a potential difference of a predetermined voltage or more is generated between the source terminal T3s and the drain terminal T3d, the reverse-side source-drain voltage monitoring circuit 7 Detect the occurrence state.

  The forward drive protection circuit 4 and the forward source / drain voltage monitoring circuit 6 of this motor control device are configured as shown in FIG. The reverse drive protection circuit 5 and the reverse side source / drain voltage monitoring circuit 7 have the same configuration as the forward drive protection circuit 4 and the forward side source / drain voltage monitoring circuit 6, and are arranged in the H-bridge. Therefore, the configuration and operation of the forward drive protection circuit 4 and the forward-side source / drain voltage monitoring circuit 6 will be described below as representatives.

  First, the forward-side source / drain voltage monitoring circuit 6 will be described. The forward-side source-drain voltage monitoring circuit 6 is provided with resistors R1 and R2 at both ends of the source terminal T1s and the drain terminal T1d of the first switch SW1, and connects the base of the transistor Tr2 to an intermediate connection point between these resistors. The emitter of the transistor Tr2 is connected to the power supply line E of the resistor R1, that is, the source terminal T1s of the first switch SW1, and the collector of the transistor Tr2 is connected to the forward drive protection circuit 4.

  The operation of the forward-side source / drain voltage monitoring circuit 6 will be described. For example, the first switch SW1 is in an off state (the microcomputer 3 is in the rotation stop command state Sn, the reverse rotation preparation command state Sr1, or the reverse drive command state Sr2. If the ground fault abnormality occurs at the first terminal Tm1 of the motor M, the power supply voltage is applied to the resistor R1 and the resistor R2 connected in series, so that the resistor R1 is connected between the emitter and base of the transistor Tr2. A potential difference corresponding to the voltage drop occurs, and a forward bias is generated between the emitter and base of the transistor Tr2. Accordingly, the transistor Tr2 is turned on.

  In addition, if the first switch SW1 is in the OFF state, even when a ground fault abnormality occurs at the second terminal Tm2 of the motor M, the resistance value of the motor M is sufficiently smaller than the resistance values of the resistors R1 and R2. The forward-side source-drain voltage monitoring circuit 6 responds in the same way as when the first terminal ground fault occurs, and the transistor Tr2 is turned on.

  Incidentally, when the first switch SW1 is in the OFF state, the microcomputer 3 is in the ON state because the microcomputer 3 is in the rotation stop command state Sn, the reverse rotation preparation command state Sr1, or the reverse drive command state Sr2. Therefore, even if the first terminal Tm1 and the second terminal Tm2 of the motor M are short-circuited and a short-circuit abnormality occurs between the terminals, the transistor Tr2 is not turned on. When a short circuit abnormality occurs between the terminals, the resistance of the resistor R1 is reached when the microcomputer 3 enters the normal rotation drive command state Sf2 through the normal rotation preparation command state Sf1 and the fourth switch SW4 is turned on. And a power supply voltage is applied to both ends of R2, and the transistor Tr2 is turned on.

  When the ground fault abnormality of the first terminal Tm1 of the motor M occurs when the first switch SW1 is in the on state and when the short circuit abnormality between the first terminal Tm1 and the second terminal Tm2 occurs, Thus, the power supply voltage is applied to both ends of the resistors R1 and R2, and the transistor Tr2 is turned on.

  Further, when the microcomputer 3 is in the reverse drive command state Sr2, the second switch SW2 is turned on, so that the motor M can be turned off even if there is no abnormality in either the first terminal or the second terminal. Since the power supply voltage is applied between the source and drain of the first switch SW1 in the state, the power supply voltage is applied to both ends of the resistors R1 and R2, and the transistor Tr2 is turned on.

  Furthermore, even if the reverse drive command state Sr2 changes to the rotation stop command state Sn, if the motor M generates a back electromotive force due to the rotational inertia moment in the reverse drive state, the OFF state of the first switch SW1 A certain amount of voltage is applied between the source and drain, and a certain amount of voltage is applied to both ends of the resistors R1 and R2 even if the ground fault or short circuit abnormality of the terminal of the motor M does not occur. Therefore, the transistor Tr2 may be turned on.

  The reverse drive state continues for the above-mentioned phenomenon in which the forward-side source-drain voltage monitoring circuit 6 detects the high potential difference occurrence state regardless of whether a ground fault abnormality or a short-circuit abnormality has occurred in the terminal of the motor M. However, when switching the driving state of the motor M, the microcomputer 3 switches from the rotation stop command state Sn to the forward rotation preparation command state Sf1 to turn on the first switch SW1. In this case, there is a possibility that the forward drive protection circuit 4 may malfunction, causing a problem. Therefore, the forward drive protection circuit 4 is provided with a delay capacitor 8 as described later.

  The resistance values of the resistors R1 and R2 of the forward-side source-drain voltage monitoring circuit 6 are such that the potential difference Vsd generated between the source terminal T1s and the drain terminal T1d of the first switch SW1 is generated by the on-resistance of the switch SW1. When the voltage is abnormally higher than the potential difference (for example, 30% of the power supply voltage) or higher, a value for turning on the transistor Tr2 is selected. In this embodiment, R1 = 2k [Ω] and R2 = 10k [Ω] with respect to the power supply voltage 12 [V].

  As described above, in the forward-side source-drain voltage monitoring circuit 6, the potential difference Vsd generated between the source terminal T1s and the drain terminal T1d of the first switch SW1 is set by the power supply voltage and the resistors R1 and R2. When the voltage exceeds the voltage, the transistor Tr2 is turned on to detect a high potential difference occurrence state. As a result, the input terminal Tin of the forward drive protection circuit 4 is connected to the power supply line E, so that the transistors Tr4 and Tr5, etc. of the forward drive protection circuit 4 have a high potential difference, as will be described below. The operation state is based on the generation state.

  Further, the collector terminal of the transistor Tr2 of the forward-side source-drain voltage monitoring circuit 6 is also connected to the microcomputer 3, and the microcomputer 3 is turned on when the transistor Tr2 is turned on and the signal line of the collector terminal is at the high level. Thus, it is possible to determine whether the transistor Tr2 is turned off and the signal line of the collector terminal is not at the high level. That is, the microcomputer 3 of the present motor control device is configured to receive a detection signal indicating whether or not the forward rotation potential difference detection circuit 6 detects a high potential difference occurrence state. Thereby, the microcomputer 3 can determine whether or not the ground fault of the terminal has occurred in the rotation stop command state Sn. In this motor control device, before driving the motor M, the terminal unit A ground fault abnormality can be detected.

  Next, the forward drive protection circuit 4 will be described. As shown in FIG. 4, the forward drive protection circuit 4 includes a transistor Tr4 that sets monitoring information of the forward-side source-drain voltage monitoring circuit 6 in the latch circuit 9, and a latch circuit 9 that holds the monitoring information. The transistor Tr5 and the transistor Tr6 that are turned on, the transistor Tr7 that resets the latch circuit 9 when turned on, the transistor Tr8 that forcibly turns off the first switch SW1 when turned on, and the like.

  The operation of the forward drive protection circuit 4 is performed between the first terminal and the second terminal when a ground fault abnormality occurs at the first terminal or the second terminal (when a ground fault occurs before driving). Operation when a short-circuit abnormality occurs between terminals (when a short circuit occurs before driving) and when a ground fault occurs after normal rotation driving is started in a normal state (when a ground fault occurs after driving) The operation will be described by classifying the operation into a short circuit state after normal rotation driving is started in a normal state (when a short circuit occurs after driving) and a normal operation.

  In the following, the operation of the forward drive protection circuit 4 when the microcomputer 3 changes from the rotation stop command state Sn to the forward drive command state Sf2 will be described. The same description applies to the operation of the reverse drive protection circuit 5 when the state Sn changes to the reverse drive command state Sr2.

[Operation when a ground fault occurs before driving]
First, a case where a ground fault abnormality has occurred in the first terminal Tm1 of the motor M will be described.
Since the microcomputer 3 is in the rotation stop command state Sn, the first switch SW1 to the fourth switch SW4 are all in the off state as shown in FIG.
Since the transistor Tr1 of the high-side driver circuit D1 on the normal rotation side is off, the base of the transistor Tr7 is not subjected to a pull-down action by the transistor Tr1, and is connected to the power supply line E side via a resistor, a diode, or the like. Therefore, a forward bias is generated between the base and emitter of the transistor Tr7 of the forward drive protection circuit 4. Therefore, the transistor Tr7 is on. Since the transistor Tr7 is on, the base of the transistor Tr6 is pulled down. Since the emitter of the transistor Tr6 is connected to the power supply line E, a forward bias is generated between the base and emitter of the transistor Tr6. Therefore, the transistor Tr6 is on. Since the transistor Tr6 is on, no forward bias is generated between the base and emitter of the transistor Tr8. Therefore, the transistor Tr8 is off.
Further, since the first terminal Tm1 of the motor M is grounded, as described above, the transistor Tr2 of the forward-side source-drain voltage monitoring circuit 6 is turned on. Therefore, since a forward bias is generated between the base and emitter of the transistor Tr4, the grounded transistor Tr4 is turned on. Therefore, since no forward bias is generated between the base and emitter of the transistor Tr5, the grounded transistor Tr5 is turned off.

  When the microcomputer 3 enters the normal rotation preparation command state Sf1, the transistor Tr1 of the high-side driver circuit D1 on the normal rotation side is turned on, so that the gate terminal T1g of the first switch SW1 is turned on at a low level and delayed. Due to the discharge of the capacitor 8, the transistor Tr7 is turned from on to off after a predetermined delay time Tdly has elapsed. When the transistor Tr7 is turned off, the base of the transistor Tr6 is not subjected to the pull-down action by the transistor Tr7, and since the transistor Tr5 is turned off, the transistor Tr5 is not subjected to the pull-down action. Therefore, no forward bias is generated. Therefore, the transistor Tr6 is turned off.

  When the transistor Tr6 is turned off, a forward bias is generated between the base and emitter of the transistor Tr8, the transistor Tr8 is turned on, and the gate terminal T1g of the first switch SW1 is connected to the power supply line E via the turned on transistor Tr8. Connected. Accordingly, since the potential of the gate terminal T1g of the first switch SW1 becomes substantially the same as the potential of the source terminal T1s, the first switch SW1 is turned off.

Next, a case where a ground fault abnormality has occurred at the second terminal Tm2 of the motor M will be described.
While the microcomputer 3 is in the rotation stop command state Sn, the forward-side source-drain voltage monitoring circuit 6 is in the same state as when the ground fault abnormality has occurred in the first terminal Tm1 described above. .
When the microcomputer 3 enters the forward rotation preparation command state Sf1 and the first switch SW1 is turned on, the second terminal Tm2 of the motor M is grounded, so the first between the power line E and the ground line G is the first. The switch SW1 and the motor M are connected in series. Since the ON resistance of the first switch SW1 is sufficiently smaller than the resistance value of the motor M, almost no voltage is generated between the source terminal T1s and the drain terminal T1d of the first switch SW1, and the forward bias is applied between the base and emitter of the transistor Tr2. , The transistor Tr2 is turned off, and the transistor Tr4 is also turned off. Since the transistor Tr6 is on at this point, the base of the transistor Tr5 is kept pulled up by the on transistor Tr6, and the transistor Tr5 is on.

  Thereafter, as described above, the transistor Tr7 is turned off from on, so that the base of the transistor Tr6 is not subjected to the pull-down action by the transistor Tr7. However, the transistor Tr6 is kept on because the transistor Tr5 is subjected to the pull-down action. To do. Accordingly, a forward bias is not generated between the base and emitter of the transistor Tr8 and is not turned on, so the first switch M1 is not turned off.

  Thus, even if the first switch SW1 is turned on when a ground fault has occurred at the second terminal Tm2 of the motor M, the forward drive protection circuit 4 does not turn off the first switch SW1, The microcomputer 3 enters the forward rotation drive command state Sf2 while the 1 switch SW1 is in the ON state. Incidentally, when the ground fault abnormality occurs in the second terminal Tm2 of the motor M, when the microcomputer 3 enters the reverse rotation preparation command state Sr1 and the third switch SW3 is turned on, the ground fault abnormality occurs in the first terminal Tm1. Is the state corresponding to the case where the microcomputer 3 enters the forward rotation preparation command state Sf1, and the reverse drive protection circuit 5 forcibly turns off the third switch SW3.

[Operation when short circuit occurs before driving]
In this case, as already described in the description of the operation of the forward-side source-drain voltage monitoring circuit 6, when the microcomputer 3 enters the forward drive command state Sf2 and the fourth switch SW4 is turned on. The transistor Tr2 of the forward-side source-drain voltage monitoring circuit 6 is turned on. Therefore, when the microcomputer 3 enters the normal rotation preparation command state Sf1, the transistor Tr2 does not turn on, so that the microcomputer 3 enters the normal rotation drive command state Sf2 while the first switch SW1 remains on.

  When the microcomputer 3 enters the forward rotation driving command state Sf2 and the transistor Tr2 is turned on, the transistor Tr4 is turned on from off, and the transistor Tr5 is turned on from off. Since the transistor Tr7 is already turned off when the microcomputer 3 enters the forward rotation driving command state Sf2, the transistor Tr6 is turned off from on when the transistor Tr5 is turned off. As a result, the transistor Tr8 is turned on, and the first switch SW1 is turned off in the same manner as the above-mentioned “operation when a ground fault occurs before driving”.

[Operation when ground fault occurs after driving]
Since the microcomputer 3 is in the forward rotation drive command state Sf2, the first switch SW1 and the fourth switch SW4 are in the on state. Also in this case, as already described in the description of the operation of the forward-side source / drain voltage monitoring circuit 6, the forward-side source / drain voltage monitoring circuit when the ground fault occurs at the first terminal of the motor M. 6 transistor Tr2 is turned on.
When the transistor Tr2 is turned on, the transistor Tr4 is turned from off to on, whereby the transistor Tr5 is turned from on to off. Since the microcomputer 3 is in the forward rotation driving command state Sf2, the transistor Tr7 has already been turned off. Therefore, when the transistor Tr5 is turned off, the transistor Tr6 is turned from on to off. As a result, the transistor Tr8 is turned on, and the first switch SW1 is turned off in the same manner as the above-mentioned “operation when a ground fault occurs before driving”.

  If the microcomputer 3 is in the forward rotation driving command state Sf2, the second terminal of the motor M is connected to the ground side by the fourth switch SW4 in the on state, so that the ground fault of the second terminal is present. Even if it occurs, since it is not distinguished from the fact that the fourth switch SW4 is in the ON state, the forward-side source-drain voltage monitoring circuit 6 cannot detect the ground fault abnormality of the second terminal. After the rotation stop command state Sn is reached, the ground fault abnormality of the second terminal can be detected at the time of transition to the normal rotation preparation command state Sf1. When the rotation stop command state Sn is changed to the reverse rotation preparation command state Sr1, the reverse side source / drain voltage monitoring circuit 7 can detect the ground fault abnormality of the second terminal.

[Operation when a short circuit occurs after driving]
Since the microcomputer 3 is in the forward rotation drive command state Sf2, the first switch SW1 and the fourth switch SW4 are in the on state. Also in this case, as already described in the description of the operation of the forward-side source / drain voltage monitoring circuit 6, the forward-side source / drain at the time when the short-circuit abnormality between the first terminal and the second terminal of the motor M occurs. The transistor Tr2 of the inter-voltage monitoring circuit 6 is turned on.
When the transistor Tr2 is turned on, the transistor Tr4 is turned from off to on, whereby the transistor Tr5 is turned from on to off. Since the microcomputer 3 is in the forward rotation driving command state Sf2, the transistor Tr7 has already been turned off. Therefore, when the transistor Tr5 is turned off, the transistor Tr6 is turned from on to off. As a result, the transistor Tr8 is turned on, and the first switch SW1 is turned off in the same manner as the above-mentioned “operation when a ground fault occurs before driving”.

  In any of the above cases, when the forward drive protection circuit 4 is activated and the first switch SW1 is turned off, the forward drive protection circuit 4 is turned on by the microcomputer 3 with respect to the first switch SW1. While outputting the command, the first switch SW1 is held in the off state, and when the microcomputer 3 stops outputting the on command to the first switch SW1, the holding of the off state of the first switch SW1 is released. It is configured.

  In other words, in order to switch off the transistor Tr8 holding the first switch SW1 in the off state, it is necessary to pull up the base of the transistor Tr8 to a high level by turning on the transistor Tr6. However, the forward bias between the base and emitter of the transistor Tr6 does not occur unless the transistor Tr5 connected to the base side is once turned off unless the transistor Tr7 connected to the base of the transistor Tr6 is also turned on. That is, even if the ground fault abnormality or short circuit abnormality of the terminal of the motor M is resolved and the transistor Tr2 of the forward-side source-drain voltage monitoring circuit 6 is turned off, the transistor Tr4 is turned off, but the transistor Tr7 is turned off. As long as the transistor Tr5 and the transistor Tr6 are turned off, the transistor Tr5 is not affected. That is, when the transistor Tr7 is turned off, the latch circuit 9 is in a latched state.

  When the transistor Tr7 is turned on and the transistor Tr6 is turned on, the transistor Tr5 is turned on or off according to the operation state of the transistor Tr4, that is, the normal-side source-drain voltage monitoring circuit 6. 6 is switched so as to follow the change in the operation state. That is, when the transistor Tr7 is turned on, the latch circuit 9 enters a non-latching state.

  As described above, the latch circuit 9 including the transistor Tr5, the transistor Tr6, and the like has a forward-side source-drain voltage monitoring circuit when the microcomputer 3 outputs an on command to the first switch SW1 and the transistor Tr7 is turned off. 6 is configured to be in a latch state that holds the abnormality detection information output first. Accordingly, the forward drive protection circuit 4 including the latch circuit 9 is in a latch state in which the first switch SW1 is held in the OFF state while the microcomputer 3 outputs the ON command to the first switch SW1, and the microcomputer 3 When No. 3 stops outputting an ON command to the first switch SW1, it is configured to be in a non-latching state in which the holding of the OFF state of the first switch SW1 is released.

  As a result, the forward drive protection circuit 4 of the motor control device detects a ground fault abnormality or a short circuit abnormality of the terminal of the motor M based on the output of the forward-side source-drain voltage monitoring circuit 6, and the first Once the switch SW1 is forcibly turned off, the first switch SW1 is held in the off state even if the output of the forward-side source-drain voltage monitoring circuit 6 changes thereafter. When a ground fault or short circuit occurs intermittently, such as when a harness is poorly connected, the first switch SW1 is turned on intermittently, causing the motor M to operate abnormally or intermittent overcurrent. Thus, the first switch SW1 and the fourth switching element SW4 can be prevented from being burned out.

  In addition, in the case where the rotational speed of the motor is controlled by PWM control that frequently turns on / off the fourth switch SW4, if a short circuit abnormality occurs between the terminals, the voltage on the forward-side source / drain is changed along with the on / off change of the fourth switch 4. Although the output of the monitoring circuit 6 changes, once the first switch is turned off, the first switch SW1 is held in the off state. Therefore, even if a short circuit abnormality occurs between the motor terminals during the PWM control, the abnormal operation of the motor M can be prevented and the first switch SW1 and the fourth switch SW4 can be prevented from being burned out. Can do.

  In the above, the operation of the forward drive protection circuit 4 when a ground fault abnormality or a short circuit abnormality has occurred in the terminal of the motor M has been described, but no ground fault abnormality or short circuit abnormality has occurred in the terminal of the motor M. As described above, when the driving direction of the motor M is switched in spite of the normal time, the forward-side source-drain voltage monitoring circuit 6 may detect a high potential difference occurrence state. Hereinafter, the operation of the forward drive protection circuit 4 when the motor M is switched from the reverse drive state to the forward drive state will be described with a focus on the action of the delay capacitor 8 provided as a countermeasure.

[Normal operation]
When the motor M is changed from the reverse drive state to the forward drive state, the microcomputer 3 sequentially switches the command state in the order indicated by the arrow B in FIG.
As shown in the timing chart of FIG. 5, when the microcomputer 3 changes from the reverse rotation drive command state Sr2 to the reverse rotation preparation command state Sr1, the second switch SW2 is turned off. Immediately after that, since the induced current of the coil of the motor M flows through the flywheel diode of the first switch SW1, the transistor Tr2 is turned off for a moment and the transistor Tr4 is also turned off for a moment. Due to the counter electromotive force, a certain voltage is generated between the source and drain of the first switch SW1, the transistor Tr2 is turned on again, and the transistor Tr4 is also turned on again.

  On the other hand, when the microcomputer 3 switches from the rotation stop command state Sn to the forward rotation preparation command state Sf1 and outputs an on command to the first switch SW1, the transistor Tr1 is turned on and the first switch SW1 is turned on. become. When the transistor Tr1 is turned on, the transistor Tr7 is turned off, and the latch circuit 9 is switched from the non-latching state to the latching state. However, at this time, if the transistor Tr4 is on, the normal rotation driving protection circuit 4 is in the latched state in this state, so that the transistor Tr5 of the latch circuit 9 is held off. The drive protection circuit 4 malfunctions and the first switch SW1 is forcibly turned off.

  Therefore, after the delay capacitor 8 is provided and the first switch SW1 is turned on, the potential difference between the potential of the source terminal T1s and the drain terminal T1d of the first switch SW1 becomes sufficiently small. The transistor Tr7 can be kept on until the transistor Tr5 is turned off and the transistor Tr5 that is turned off is reliably turned on by the transistor Tr6 that is turned on.

  Specifically, as shown in FIG. 5, a delay time Tdly has elapsed from the time when the transistor Tr1 is turned on so that the transistor Tr7 is not turned off during the period Tng when the transistor Tr5 is turned off from the time when the transistor Tr1 is turned on. After that, the transistor Tr7 is turned off.

  As described above, the forward drive protection circuit 4 of the motor control device delays the time when the microcomputer 3 switches to the latch state as the microcomputer 3 switches from the reverse drive command state Sr2 to the forward drive command state Sf2. A delay capacitor 8 is provided. That is, the delay capacitor 8 functions as a forward delay circuit. Thereby, in this motor control device, when the rotational drive direction of the motor M is switched from the reverse drive direction to the normal drive direction, the forward drive protection circuit 4 malfunctions and the motor M is not driven forward. Is prevented from occurring.

In the above description, the case where the motor M is driven in the forward direction has been mainly described. However, as described above, the case where the motor M is driven in the reverse direction can be explained in the same manner.
As described above, the present motor control device is configured so that a ground fault abnormality or a short-circuit abnormality occurs in the first terminal or the second terminal of the motor M, and an overcurrent flows through a switch constituting the H bridge. The current can be stopped in a short time compared to the conventional type that activates the protection means to stop the overcurrent, thus simplifying the burnout of the switching element in the event of a motor ground fault or short circuit abnormality With a simple configuration, it can be avoided accurately.

[Another embodiment]
Hereinafter, other embodiments are listed.
(1) In the above-described embodiment, the high-side switch is a p-channel MOS-FET and the low-side switch is an n-channel MOS-FET. It may be a FET, or a semiconductor device such as a bipolar transistor instead of a MOS-FET.
(2) In the above embodiment, the forward-side source / drain voltage monitoring circuit 6 and the reverse-side source / drain voltage monitoring circuit 7 are configured by the bipolar transistor Tr2, but may be configured by a comparator or the like. .
(3) In the above embodiment, the forward rotation potential difference detection circuit and the reverse rotation potential difference detection circuit are exemplified by a circuit that monitors the source-drain voltage of the switching element connected to the power supply side. A circuit that monitors a current flowing through a switching element connected to the power supply side, such as a circuit using a resistor or the like, may be used. In this case, the forward rotation potential difference detection circuit and the reverse rotation potential difference detection circuit may be provided separately, but may be a circuit configured in a shared mode.
(4) The configurations of the forward drive protection circuit 4 and the reverse drive protection circuit 5 may not have a latch function. Further, the circuit is not limited to the circuit exemplified in this embodiment, and can be appropriately changed.

Overall block diagram of motor controller Correspondence table between each command state of microcomputer and on / off state of each switch High-side driver circuit schematic Circuit diagram of forward drive protection circuit and reverse drive protection circuit Timing chart showing the operating state of each element when the motor is switched from the reverse drive state to the forward drive state

Explanation of symbols

SW1 first switching element SW2 second switching element SW3 third switching element SW4 fourth switching element T1s power supply side terminal T1d in the first switching element motor side terminal T3s in the first switching element power supply side terminal T3d in the third switching element Motor side terminal Tm1 First terminal side Tm2 Second terminal side E Power source side G Ground side M Motor Sf2 Forward drive command state Sn Rotation stop command state Sr2 Reverse drive command state 3 Control means 4 Forward drive Protection circuit 5 Reverse drive protection circuit 6 Forward rotation potential difference detection circuit 7 Reverse rotation potential difference detection circuit 8 Forward rotation delay circuit

Claims (4)

A first switching element connected to the power source side and the first terminal side for forward rotation of the motor;
A second switching element connected to the ground side and the first terminal side of the motor;
A third switching element connected to the power supply side and a second terminal side for reverse rotation of the motor;
A fourth switching element connected to the ground side and the second terminal side of the motor;
A rotation stop command state that outputs an off command to each of the first switching element, the second switching element, the third switching element, and the fourth switching element, the first switching element, and the fourth switching element. A forward drive command state for outputting an on command to the switching element and outputting an off command to the second switching element and the third switching element; and the second switching element and the third Motor control provided with control means capable of switching to a reverse drive command state for outputting an ON command to the switching element and outputting an OFF command to the first switching element and the fourth switching element A device,
A forward potential difference detection circuit for detecting a high potential difference occurrence state in which the potential difference between the potential of the power supply side terminal and the potential of the motor side terminal in the first switching element is greater than a predetermined voltage;
A reverse potential difference detection circuit for detecting a high potential difference occurrence state in which the potential difference between the potential of the power supply side terminal and the potential of the motor side terminal in the third switching element is greater than a predetermined voltage;
When the forward rotation potential difference detection circuit detects a high potential difference occurrence state in a state where the control means outputs an on command to the first switching element, the first switching element is forcibly turned off. A forward drive protection circuit;
In a state where the control means outputs an ON command to the third switching element, when the reverse potential difference detection circuit detects a high potential difference occurrence state, the third switching element is forcibly turned off. A motor control device provided with a reverse drive protection circuit. The forward drive protection circuit is
While the control means outputs an ON command to the first switching element, the control means enters a latch state for holding the first switching element in an OFF state, and the control means outputs an ON command to the first switching element. Is not output, and the first switching element is configured to be in a non-latching state that releases the hold of the off state,
The reverse drive protection circuit comprises:
While the control means outputs an ON command to the third switching element, the control means enters a latch state for holding the third switching element in the OFF state, and the control means sends an ON command to the third switching element. 2. The motor control device according to claim 1, wherein the motor control device is configured to be in a non-latching state in which holding of the off state of the third switching element is released when the output of the third switching element is stopped. The forward drive protection circuit is
A forward rotation delay circuit configured to delay the time when the control means switches to the forward drive command state from the reverse drive command state and to enter the latch state;
The reverse drive protection circuit comprises:
The reverse rotation delay circuit which delays the time which becomes the said latch state according to the said control means switching from the said normal rotation drive command state to the said reverse drive command state, It is comprised. Motor control device.   The detection signal indicating whether or not the forward potential difference detection circuit and the reverse potential difference detection circuit detect a high potential difference occurrence state is input to the control means. The motor control device according to any one of claims.

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