JP6844388B2 - Electronic control device - Google Patents

Description

The present invention relates to an electronic control device including an H-bridge circuit for driving a motor mounted on a vehicle.

In general, it is known that a motor generates an induced voltage that is proportional to its rotation speed and in the direction opposite to the energization direction. For example, a valve for an internal combustion engine mounted on a vehicle (for example, a valve for air supply / exhaust) is opened / closed by using a motor which is a DC motor as a power source. As a drive circuit for driving a DC motor, an H-bridge circuit composed of four switching elements is generally used (see, for example, Patent Document 1).

Japanese Unexamined Patent Publication No. 2013-162701

In a configuration in which a valve for an internal combustion engine is opened by using a motor as a power source, energization of the motor is often PWM controlled. In the above configuration, when the valve is opened and closed, a high duty (on-duty) is set so that the energization period of the motor is long immediately after the start of the operation, whereby the valve body operates at high speed. Then, as the target opening degree is approached, the duty is gradually reduced so that the energization period of the motor is gradually shortened.

Here, during the off-duty period during which the energization of the motor is stopped, that is, during the non-energization period, a current flows in the direction opposite to the controlled energization direction due to the action of the induced voltage generated by the motor. The magnitude of the induced voltage varies depending on the specifications of the motor, etc., but in the case of a motor with a large induced voltage, a circuit (for example, a current detection circuit that detects the current of the motor, an H-bridge circuit) during this non-energized period. , Etc.), which may cause a failure of the circuit element due to a current flowing in excess of the current rating of the elements constituting the element.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electronic control device capable of protecting an element constituting a circuit from a current flowing due to the action of an induced voltage.

Electronic control equipment according to claim 1, 3, H-bridge circuit (3) for driving the motor (2) mounted on a vehicle, the drive control unit (4), a current limiting resistor (R3, R 4) and It is equipped with a switching unit (10, 23 ). The drive control unit controls the energization of the motor from the DC power supply by controlling the operation of the H-bridge circuit. The current limiting resistor is for limiting the current flowing through the motor during the non-energized period, which is the period during which the energization of the motor from the DC power supply is stopped. The switching unit switches between a limited state in which the current limiting resistor is interposed in the current path through which the current flows and a normal state in which the current limiting resistor is not interposed in the current path. The switching unit according to claim 1 includes switches (Tr5, Tr6) connected in series to the current limiting resistor, and the current limiting resistor and the series circuit of the switch are switching provided on the downstream side of the H bridge circuit. The upstream switching element (Tr1, Tr2), which is a switching element provided on the upstream side of the H-bridge circuit and is connected in parallel to the downstream switching element (Tr3, Tr4), transitions from on to off. At that time, the switch is turned on to switch to the restricted state. The switching unit (23) according to claim 3 includes switches (Tr5, Tr6) connected in series with respect to the current limiting resistor, and the current limiting resistor and the series circuit of the switch are provided on the upstream side of the H bridge circuit. The downstream switching element (Tr3, Tr4), which is a switching element provided on the downstream side of the H-bridge circuit, is connected in parallel to the upstream switching element (Tr1, Tr2), which is the switching element, is turned on. When transitioning to off, the switch is turned on to switch to the restricted state.

As described above, during the non-energization period when the energization of the motor is stopped, a current flows in the direction opposite to the energization direction controlled by the action of the induced voltage generated by the motor. Such a reverse current may become an excessive current depending on the specifications of the motor. Therefore, in the above configuration, the switching unit switches to the limited state, so that the reverse current is limited by flowing a current limiting resistor provided separately from the H bridge circuit. Therefore, in the above configuration, an excessive current that exceeds the current rating of each circuit element that constitutes a circuit such as an H-bridge circuit does not flow. Therefore, according to the above configuration, it is possible to obtain an excellent effect that the elements constituting the circuit can be protected from the current flowing due to the action of the induced voltage.

Further, the magnitude of the current flowing due to the action of the induced voltage differs depending on the specifications of the motor and the like. Therefore, when the magnitude of the current can be suppressed to less than the current rating of the circuit element, the switching unit may switch to a normal state in which the current limiting resistor does not intervene in the current path. In this way, the current limiting operation by the current limiting resistor is not performed unnecessarily, and as a result, the life of the current limiting resistor and the switch constituting the switching unit is improved.

The figure which shows typically the structure of the motor drive device which concerns on 1st Embodiment. The figure for demonstrating the circuit operation of the H-bridge circuit and the current limiting circuit which concerns on 1st Embodiment. The figure which summarized the circuit operation of the H bridge circuit and the current limiting circuit which concerns on 1st Embodiment Timing chart for explaining the operating state of each part when the motor according to the first embodiment is rotated in the forward direction. Timing chart for explaining the operating state of each part when the motor according to the first embodiment is rotated in the opposite direction. The figure which shows typically the structure of the motor drive device which concerns on 2nd Embodiment. The figure which shows typically the structure of the motor drive device which concerns on 3rd Embodiment. The figure which summarized the circuit operation of the H bridge circuit and the current limiting circuit which concerns on 3rd Embodiment

Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. In each embodiment, substantially the same configuration is designated by the same reference numerals and the description thereof will be omitted.
(First Embodiment)
Hereinafter, the first embodiment of the present invention will be described with reference to FIGS. 1 to 5.

The motor drive device 1 shown in FIG. 1 is provided in an electronic control device (ECU) mounted on a vehicle. The motor drive device 1 drives a motor 2 mounted on a vehicle, and includes an H-bridge circuit 3, a drive control unit 4, and a current limiting circuit 5. In the present embodiment, the motor 2 is a DC motor, which drives a valve for an internal combustion engine such as a throttle valve. A battery voltage VB output from an in-vehicle battery (not shown) is supplied to the motor drive device 1. The in-vehicle battery corresponds to a DC power supply.

The drive control unit 4 controls the energization of the motor 2 from the DC power supply by controlling the operation of the H-bridge circuit 3. The drive control unit 4 includes a microcomputer 6, a driver 7, and current detection circuits 8 and 9. The microcomputer 6 controls the overall operation of the device. An opening degree detection signal Sa and a current detection signal Sb are input to the microcomputer 6.

The opening degree detection signal Sa is output from an opening degree sensor that detects the opening degree of a valve (not shown), and is a voltage signal corresponding to the opening degree of the valve driven by the motor 2. Further, the current detection signal Sb is output from the current detection circuit 8 and is a voltage signal corresponding to the current flowing through the motor 2.

Based on each detection signal Sa, Sb, etc., the microcomputer 6 performs PWM control (DUTY control) of energization of the motor 2 so that the opening degree of a valve (not shown) becomes a desired opening degree. The microcomputer 6 generates a drive command so that the motor 2 can be energized in a desired state, and outputs the drive command to the driver 7. The driver 7 controls the operation of the H-bridge circuit 3 and the current limiting circuit 5 in accordance with a drive command given by the microcomputer 6.

The H-bridge circuit 3 is a motor drive circuit for driving a motor 2 which is a DC motor, and has a general configuration including four transistors Tr1 to Tr4. In the present embodiment, the transistors Tr1 to Tr4 are all N-channel type MOS transistors, and a body diode having the source side as an anode is connected between the source and drain of the transistors.

Each drain of the transistors Tr1 and Tr2 is connected to a power supply line Lb to which a battery voltage VB is applied. The sources of the transistors Tr1 and Tr2 are connected to the drains of the transistors Tr3 and Tr4, respectively. Each source of the transistors Tr3 and Tr4 is connected to the ground wire Lg to which the ground potential GND (= 0V), which is the reference potential of the circuit, is given.

The interconnection node N1 of the transistors Tr1 and Tr3 is connected to one terminal M1 of the motor 2 via a detection resistor R1 for detecting the current flowing through the motor 2. The interconnection node N2 of the transistors Tr2 and Tr4 is connected to the other terminal M2 of the motor 2. The motor 2 rotates in the forward direction when a current flows from the terminal M1 to the terminal M2, and rotates in the opposite direction when a current flows from the terminal M2 to the terminal M1. A drive signal output from the driver 7 is given to each gate of the transistors Tr1 to Tr4.

In the above configuration, the transistors Tr1 and Tr2 correspond to upstream switching elements which are switching elements provided on the upstream side of the H-bridge circuit 3. Further, the transistors Tr3 and Tr4 correspond to downstream switching elements which are switching elements provided on the downstream side of the H-bridge circuit 3.

The current detection circuit 8 detects the current flowing through the motor 2 and outputs a current detection signal Sb corresponding to the current. In this case, the current detection circuit 8 outputs a voltage signal obtained by amplifying the voltage between the terminals of the detection resistor R1 provided between the node N1 and the terminal M1 of the motor 2 as the current detection signal Sb.

The current limiting circuit 5 includes current limiting resistors R3 and R4 and transistors Tr5 and Tr6. The current limiting resistors R3 and R4 are resistors for limiting the current flowing through the motor 2 (hereinafter, also referred to as reflux current) during the non-energized period, which is the period during which the energization of the motor 2 is stopped. The transistors Tr5 and Tr6 are both N-channel type MOS transistors, and a body diode with the source side as the anode is connected between the source and drain of the transistors.

The current limiting resistor R3 is connected between the node N1 and the drain of the transistor Tr5. The source of the transistor Tr5 is connected to the ground wire Lg. That is, the series circuit of the current limiting resistor R3 and the transistor Tr5 is connected in parallel to the transistor Tr3 of the H-bridge circuit 3.

The current limiting resistor R4 is connected between the node N2 and the drain of the transistor Tr6. The source of the transistor Tr6 is connected to the ground wire Lg. That is, the series circuit of the current limiting resistor R4 and the transistor Tr6 is connected in parallel to the transistor Tr4 of the H-bridge circuit 3.

A drive signal output from the driver 7 is given to each gate of the transistors Tr5 and Tr6. The driver 7 drives the transistors Tr5 and Tr6 based on the drive command given from the microcomputer 6. Therefore, the driving of the transistors Tr5 and Tr6 is controlled by the microcomputer 6.

In the above configuration, the transistor Tr5 corresponds to a switch connected in series with the current limiting resistor R3. Further, the transistor Tr6 corresponds to a switch connected in series with the current limiting resistor R4. The switching unit 10 is composed of the transistors Tr5, Tr6, the microcomputer 6, and the driver 7.

The switching unit 10 switches between a limited state in which the current limiting resistors R3 and R4 are interposed in the path through which the reflux current flows, and a normal state in which the current limiting resistors R3 and R4 are not interposed in the path through which the reflux current flows. In this case, when the transistors Tr5 and Tr6 are turned on, the state is switched to the restricted state, and when the transistors Tr5 and Tr6 are turned off, the state is switched to the normal state. It should be noted that such a switching operation is controlled by the microcomputer 6.

In the present embodiment, when the transistor Tr1 of the H-bridge circuit 3 transitions from on to off, the switching unit 10 switches to the restricted state by turning on the transistor Tr5. Further, when the transistor Tr2 of the H-bridge circuit 3 transitions from on to off, the switching unit 10 switches to the restricted state by turning on the transistor Tr6.

However, the switching unit 10 switches to the restricted state on condition that the rotation speed of the motor 2 is equal to or higher than a predetermined threshold rotation speed. The rotation speed of the motor 2 can be estimated from the slope (differential value) of the opening degree detection signal Sa. The threshold rotation speed may be set to a value based on the specifications of the motor 2, the rating of the circuit elements constituting each circuit, and the like so that the effect of the present embodiment described later can be surely obtained. In the present embodiment, for example, the threshold rotation speed is a predetermined margin with respect to the rotation speed of the motor 2 when a recirculation current of the same magnitude as the current rating of the circuit element provided in the path through which the recirculation current flows flows. Is set to a low value.

Next, the operation of the above configuration will be described.
In the motor drive device 1, both the energization period in which the DC power supply energizes the motor 2 (hereinafter, also referred to as the ON DUTY period) and the non-energization period in which the energization from the DC power supply to the motor 2 is stopped (hereinafter, the OFF DUTY period). Call), and are repeated alternately. Further, a penetration suppression period for suppressing the generation of a penetration current is provided between the energization period and the non-energization period.

Hereinafter, the circuit operation in each of these periods will be described with reference to FIG. In this case, it is assumed that the motor 2 is rotated in the positive direction. Further, in FIG. 2, the transistors Tr1 to Tr4 are represented by simple switch symbols so that their ON / OFF (ON / OFF) can be clearly defined. Further, in FIG. 2, the motor 2 is equivalently represented as a resistor Ra, an inductance La, and an induced voltage Ec.

[1] ON DUTY period As shown in FIG. 2A, in the ON DUTY period, the transistors Tr1 and Tr4 are turned on and the transistors Tr2, Tr3, Tr5 and Tr6 are turned off. As a result, the current flows in the path indicated by the solid arrow in FIG. 2A, that is, the path “power line Lb → Tr1 → terminal M1 → terminal M2 → Tr4 → ground line Lg”, and the motor 2 rotates in the positive direction. To do.

[2] Penetration suppression period (at the time of transition from ON to OFF)
As shown in FIG. 2B, in the penetration suppression period provided in the transition period from the ON DUTY period to the OFF DUTY period, the transistors Tr1 to Tr3, Tr5, and Tr6 are turned off and the transistor Tr4 is turned on. As a result, the current flows through the path indicated by the solid arrow in FIG. 2B, that is, the path “ground wire Lg → Tr3 body diode → terminal M1 → terminal M2 → Tr4 → ground wire Lg”.

[3] OFF DUTY period (normal state)
When the condition for switching to the restricted state is not satisfied, that is, when the rotation speed of the motor 2 is less than the threshold rotation speed, the circuit operation is as shown in FIG. 2 (c). That is, in this case, the transistors Tr1, Tr2, Tr5, and Tr6 are turned off, and the transistors Tr3 and Tr4 are turned on.

As a result, at the beginning of switching to the period, the current flows through the route of "ground wire Lg-> Tr3-> terminal M1-> terminal M2-> Tr4-> ground wire Lg". However, after that, due to the action of the induced voltage Ec, a current starts to flow in the path opposite to the above path. That is, as shown by the solid arrow in FIG. 2C, the current flows in the path of “ground wire Lg → Tr4 → terminal M2 → terminal M1 → Tr3 → ground wire Lg”. As described above, in this embodiment, a so-called low-side reflux method is adopted in which reflux is performed by turning on the transistor on the downstream side constituting the H-bridge circuit 3.

[4] OFF DUTY period (restricted state)
When the condition for switching to the restricted state is satisfied, that is, when the rotation speed of the motor 2 is equal to or higher than the threshold rotation speed, the circuit operation is as shown in FIG. 2D. That is, in this case, the transistors Tr1 to Tr3 and Tr6 are turned off, and the transistors Tr4 and Tr5 are turned on.

As a result, at the beginning of switching to the period, the current flows through the route of "ground wire Lg-> Tr5-> current limiting resistor R3-> terminal M1-> terminal M2-> Tr4-> ground wire Lg". However, after that, due to the action of the induced voltage Ec, a current starts to flow in the path opposite to the above path. That is, as shown by the solid arrow in FIG. 2D, the current flows through the path of “ground wire Lg → Tr4 → terminal M2 → terminal M1 → current limiting resistor R3 → Tr5 → ground wire Lg”. During this period, the current flowing through the motor 2 is limited by flowing through the current limiting resistor R3.

[5] Penetration suppression period (at the time of transition from OFF to ON)
As shown in FIG. 2B, in the penetration suppression period provided in the transition period from the OFF DUTY period to the ON DUTY period, the transistors Tr1 to Tr3, Tr5, and Tr6 are turned off and the transistor Tr4 is turned on. As a result, the current flows through the path indicated by the broken line arrow in FIG. 2B, that is, the path “ground wire Lg → Tr4 → terminal M2 → terminal M1 → Tr1 body diode → power supply line Lb”.

FIG. 3 is a table summarizing such circuit operations. The items at the top of FIG. 3 represent each period, “ON” represents the ON DUTY period, “→” represents the penetration suppression period, and “OFF” represents the OFF DUTY period. Further, the item at the bottom of FIG. 3 is an item indicating whether or not the condition for switching to the restricted state is satisfied, and if the condition is satisfied, it is described as "1", and the condition is set. If it is not satisfied, it is described as "0".

As shown in FIG. 3, in the motor control device 1, the ON DUTY period and the OFF DUTY period are alternately repeated, whereby the current flowing through the motor 2 and the opening degree of the valve are controlled. Further, in the OFF DUTY period when the condition for switching to the limited state is satisfied, the transistor Tr5 is turned on and the current limiting operation by the current limiting resistor R3 is effective.

Subsequently, the operation waveform of each part when the motor 2 is rotated in the positive direction will be described with reference to FIG. In FIG. 4 and FIG. 5 described later, regarding the current flowing through the motor 2, the direction of current flowing from the terminal M1 to the terminal M2 is positive (+), and the direction of current flowing from the terminal M2 to the terminal M1 is negative (-). It is supposed to be. Further, when the opening degree detection signal Sa is 0 [V], the opening degree is the minimum value, that is, the valve is closed, and when the opening degree detection signal Sa is 5 [V], the opening degree is the maximum. The value state, that is, the valve is open.

The period before the time t1 is a period during which the motor 2 is not energized. At time t1, there is an instruction to perform forward rotation, and energization of the motor 2 is started. As described in the prior art, the valve body is swiftly operated so that the ON DUTY period becomes longer immediately after the start of operation, and the ON DUTY period is gradually reduced as the target opening is approached.

The period of time t1 to t2 is the ON DUTY period. During this ON DUTY period, the current of the motor 2 increases sharply in the positive direction at first, but then gradually decreases in proportion to the increase in the rotation speed of the motor 2 due to the action of the induced voltage. The period of time t2 to t3 is the OFF duty period. During this OFF DUTY period, the current of the motor 2 increases in the negative direction due to the action of the induced voltage, that is, a current flows in the direction (−) opposite to the controlled energization direction (+). The following time t3 to t4 is the ON DUTY period. During this ON DUTY period, the current of the motor 2 increases in the positive direction.

At times t4 to t12, the same operation as at times t2 to t4 is repeated. In this case, the ratio of the OFF DUTY period increases as the latter half progresses. Therefore, the current of the motor 2 increases in the negative direction as it progresses to the latter half, and becomes the maximum negative current at the time t11 when the target opening degree is approached.

Times t12 to t13 are OFF DUTY periods. However, at this time, since the rotation speed of the motor 2 is decreasing, the induced voltage is also decreased, so that the current of the motor 2 increases in the positive direction, that is, the negative current decreases. Times t13 to t14 are ON DUTY periods, and the current of the motor 2 increases in the positive direction. Then, at the time t14, there is an instruction to stop energization, and the energization of the motor 2 is stopped.

Subsequently, the operation waveform of each part when the motor 2 is rotated in the opposite direction will be described with reference to FIG. The period before the time t1 is a period during which the motor 2 is not energized. At time t1, there is an instruction to perform reverse rotation, and energization of the motor 2 is started. The period of time t1 to t2 is the ON DUTY period. During this ON DUTY period, the current of the motor 2 increases sharply in the negative direction at first, but then gradually decreases in proportion to the increase in the rotation speed of the motor 2 due to the action of the induced voltage. The period of time t2 to t3 is the OFF duty period. During this OFF DUTY period, the current of the motor 2 increases in the forward direction due to the action of the induced voltage, that is, a current flows in the direction opposite to the controlled energization direction (−) (+). The following time t3 to t4 is the ON DUTY period. During this ON DUTY period, the current of the motor 2 increases in the negative direction.

At times t4 to t12, the same operation as at times t2 to t4 is repeated. In this case, the ratio of the OFF DUTY period increases as the latter half progresses. Therefore, the current of the motor 2 increases in the positive direction as it progresses to the latter half, and becomes the maximum positive current at the time t11 when the target opening degree is approached.

Times t12 to t13 are OFF DUTY periods. However, at this time, since the rotation speed of the motor 2 is decreasing, the induced voltage is also decreased, so that the current of the motor 2 increases in the negative direction, that is, the positive current decreases. Times t13 to t14 are ON DUTY periods, and the current of the motor 2 increases in the negative direction. Then, at the time t14, there is an instruction to stop energization, and the energization of the motor 2 is stopped.

According to the present embodiment described above, the following effects can be obtained.
In a configuration in which the motor 2 is driven by using the H-bridge circuit 3 as in the motor drive device 1 of the present embodiment, during the OFF DUTY period when the energization of the motor 2 is stopped, the action of the induced voltage generated by the motor 2 causes the motor 2. A current flows in the direction opposite to the controlled energization direction. Such a reverse current may become an excessive current depending on the specifications of the motor 2.

Therefore, in the above configuration, when the switching unit 10 switches to the limited state, the reverse current is limited by flowing through the current limiting resistors R3 and R4 provided separately from the H bridge circuit 3. .. Therefore, in the above configuration, an excessive current exceeding the current rating does not flow to each circuit element constituting the circuit provided in the path through which the current flows in the opposite direction. Therefore, according to the above configuration, it is possible to obtain an excellent effect that the elements constituting the circuit can be protected from the current flowing due to the action of the induced voltage.

In the above configuration, a current detection circuit 8 and an H-bridge circuit 3 can be considered as circuits that may fail when the reverse current becomes an excessive current. In particular, the current detection circuit 8 includes an amplifier (amplifier) for inputting the voltage between the terminals of the detection resistor R1 provided in series with the path through which the current of the motor 2 flows, and when an excessive current flows, the amplifier causes the amplifier. There is a risk of malfunction or failure.

Further, when the voltage value of the induced voltage greatly exceeds the voltage value of the battery voltage VB, the reverse current flowing due to the action of the induced voltage flows through the transistors Tr3 and Tr4 constituting the H-bridge circuit 3. There is a possibility that the rated current may be exceeded, which may cause the H-bridge circuit 3 to fail. According to the present embodiment, as described above, it is possible to prevent the reverse current from becoming excessive, so that the occurrence of such a failure can be prevented.

Further, the magnitude of the current flowing due to the action of the induced voltage differs depending on the specifications of the motor 2, the rotation speed, and the like. Therefore, when the magnitude of the current can be suppressed to less than the current rating of the circuit element, the switching unit 10 may switch to a normal state in which the current limiting resistors R3 and R4 are not interposed in the current path. Specifically, in the present embodiment, the switching unit 10 switches to the restricted state on the condition that the rotation speed of the motor 2 is equal to or higher than the threshold rotation speed, in other words, the rotation speed of the motor 2 is the threshold rotation speed. If it is less than the number, it is switched to the normal state. In this way, the current limiting operation by the current limiting resistors R3 and R4 is not performed unnecessarily, and as a result, the current limiting resistors R3 and R4, the switches (transistors Tr5, Tr6) constituting the switching unit 10 and the like are not used. The effect of improving the life of the transistor can be obtained.

As shown in FIGS. 4 and 5, the magnitude of the current flowing due to the action of the induced voltage becomes maximum when the valve opening approaches the target opening. Therefore, the switching period to the restricted state described above may be set to at least a period including the timing when the valve opening approaches the target opening (time t11 in FIGS. 4 and 5). In this way, the above-mentioned effect of improving the life can be further enhanced. The timing described above can be detected based on the opening degree detection signal Sa.

The series circuit of the current limiting resistor R3 and the transistor Tr5 constituting the current limiting circuit 5 and the series circuit of the current limiting resistor R4 and the transistor Tr6 are connected in parallel to the transistors Tr3 and Tr4 of the H bridge circuit 3, respectively. .. According to such a configuration, by turning off the transistors Tr5 and Tr6, it is possible to completely disconnect each circuit element of the current limiting circuit 5 from the energization path of the motor 2. Therefore, the current limiting circuit 5 having the above configuration can play an action of limiting the return current without affecting the normal motor control.

(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to FIG.
As shown in FIG. 6, the motor drive device 21 of the present embodiment is different from the motor drive device 1 of the first embodiment in that the current limit circuit 22 is provided in place of the current limit circuit 5. Further, the motor drive device 21 employs a so-called high-side reflux method in which reflux is performed by turning on the transistors on the upstream side constituting the H-bridge circuit 3.

The current limiting circuit 22 includes the same circuit elements as the current limiting circuit 5. However, in this case, the connection form of each circuit element is different. That is, the current limiting resistor R3 is connected between the power supply line Lb and the drain of the transistor Tr5. The source of the transistor Tr5 is connected to the node N1. That is, the series circuit of the current limiting resistor R3 and the transistor Tr5 is connected in parallel to the transistor Tr1 of the H-bridge circuit 3.

Further, the current limiting resistor R4 is connected between the power supply line Lb and the drain of the transistor Tr6. The source of the transistor Tr6 is connected to the node N2. That is, the series circuit of the current limiting resistor R4 and the transistor Tr6 is connected in parallel to the transistor Tr2 of the H-bridge circuit 3.

In the above configuration, the switching unit 23 is configured by the transistors Tr5, Tr6, the microcomputer 6, and the driver 7. In this case, when the transistor Tr4 of the H-bridge circuit 3 transitions from on to off, the switching unit 23 switches to the restricted state by turning on the transistor Tr5. Further, the switching unit 23 switches to the restricted state by turning on the transistor Tr6 when the transistor Tr3 of the H-bridge circuit 3 transitions from on to off.

Even in the motor drive device 21 that employs the high-side recirculation method as in the present embodiment described above, the switching unit 23 switches to the restricted state as in the motor drive device 1 of the first embodiment. Therefore, the reverse current generated by the action of the induced voltage during the OFF DUTY period is limited by flowing through the current limiting resistors R3 and R4. Therefore, the same effect as that of the first embodiment can be obtained by this embodiment as well.

(Third Embodiment)
Hereinafter, the third embodiment will be described with reference to FIGS. 7 and 8.
As shown in FIG. 7, the motor drive device 31 of the present embodiment is different from the motor drive device 1 of the first embodiment in that the current limit circuit 32 is provided in place of the current limit circuit 5. The current limiting circuit 32 includes a current limiting resistor R31, which is a resistor for limiting the return current, and a switch SW31.

The current limiting resistor R31 is connected in series with the detection resistor R1 between the node N1 which is one output terminal of the H bridge circuit 3 and the terminal M1 of the motor 2. The switch SW31 is composed of a semiconductor switching element such as a MOS transistor, and is connected in parallel with the current limiting resistor R31. The on / off of the switch SW31 is switched by the switching signal given from the driver 7. The driver 7 turns on / off the switch SW31 based on the switching command given from the microcomputer 6. Therefore, the on / off of the switch SW31 is controlled by the microcomputer 6.

In the above configuration, the switching unit 33 is configured by the switch SW31, the microcomputer 6, and the driver 7. In this case, the switch SW31 is turned off to switch to the restricted state, and the switch SW31 is turned on to switch to the normal state. It should be noted that such a switching operation is controlled by the microcomputer 6.

The circuit operation of the motor drive device 31 of the present embodiment in each period is as shown in FIG. In this case, as in the first embodiment, it is assumed that the low-side reflux is performed and the motor 2 is rotated in the positive direction.

As described above, in the motor drive device 31 of the present embodiment, as in the motor drive device 1 of the first embodiment, the switching unit 33 switches to the restricted state, so that the induced voltage acts during the OFF DUTY period. The reverse current generated by the above is limited by flowing through the current limiting resistor R31. Therefore, the same effect as that of the first embodiment can be obtained by this embodiment as well.

Further, according to the configuration of the present embodiment, as the reflux method, not only the low-side reflux method but also the high-side reflux method can be supported, so that the effect of increasing versatility can be obtained. Further, the current limiting circuit 32 is composed of two circuit elements, that is, a current limiting resistor R31 and a switch SW31. Therefore, according to the present embodiment, it is possible to obtain an effect that the number of additional circuit elements for limiting the return current can be suppressed as compared with each of the above-described embodiments.

(Other embodiments)
It should be noted that the present invention is not limited to each of the above-described embodiments and described in the drawings, and can be arbitrarily modified, combined, or extended without departing from the gist thereof.
The motor driven by the H-bridge circuit 3 is not limited to the motor 2 that drives the valve for the internal combustion engine, and can be a general motor mounted on a vehicle.
The switching element constituting the H-bridge circuit 3 and the current limiting circuit 5 may not be limited to the N-channel type MOS transistor, and various switching elements such as a P-channel type MOS transistor, a bipolar transistor, and an IGBT may be used. Can be done.

The conditions for switching to the limited state can be appropriately changed as long as the reverse current flowing due to the action of the induced voltage can be prevented from exceeding the rated current of the circuit element. For example, the condition may be that the slope (differential value) of the opening detection signal Sa output from the opening sensor is equal to or greater than a predetermined threshold slope. Further, it may be a condition that a sensor (rotation speed detection unit) such as an encoder that detects the rotation speed of the motor 2 is provided and the rotation speed detected by the sensor (rotation speed detection unit) is equal to or higher than the threshold rotation speed. Further, it may be a condition that a voltage detection unit for detecting the induced voltage from the voltages of the terminals M1 and M2 of the motor 2 is provided, and the induced voltage detected by the voltage detection unit is equal to or higher than a predetermined threshold voltage.

In each of the above embodiments, the resistance values of the current limiting resistors R3, R4, and R31 are fixed, but the resistance values may be variable. In this way, the effect of limiting the reverse current generated by the action of the induced voltage can be adjusted to the optimum value according to the specifications of the motor 2.

Although the present disclosure has been described in accordance with the examples, it is understood that the present disclosure is not limited to the examples and structures. The present disclosure also includes various modifications and modifications within a uniform range. In addition, various combinations and forms, as well as other combinations and forms that include only one element, more, or less, are also within the scope of the present disclosure.

1, 21, 31 ... Motor drive device, 2 ... Motor, 3 ... H bridge circuit, 4 ... Drive control unit, 10, 23, 33 ... Switching unit, R3, R4, R31 ... Current limiting resistor, Tr1 to Tr6 ... Transistor ..

Claims (9)

The H-bridge circuit (3) that drives the motor mounted on the vehicle and
A drive control unit (4) that controls energization of the motor (2) from a DC power supply by controlling the operation of the H-bridge circuit.
Current limiting resistors (R3, R4) for limiting the current flowing through the motor during the non-energized period, which is the period during which the energization of the motor from the DC power supply is stopped.
A switching unit (10) that switches between a limiting state in which the current limiting resistor is interposed in the current path through which the current flows and a normal state in which the current limiting resistor is not interposed in the current path.
Equipped with a,
The switching unit is
A switch (Tr5, Tr6) connected in series to the current limiting resistor is provided.
The current limiting resistor and the series circuit of the switch are connected in parallel to the downstream switching elements (Tr3, Tr4) which are switching elements provided on the downstream side of the H-bridge circuit.
The switching unit is brought into the restricted state by turning on the switch when the upstream switching elements (Tr1, Tr2), which are switching elements provided on the upstream side of the H-bridge circuit, transition from on to off. Electronic control device that switches between. The switching unit is
Equipped with two of the above switches
The series circuit of the current limiting resistor (R3) and one of the switches (Tr5) is connected in parallel to one of the downstream switching elements (Tr3).
The series circuit of the current limiting resistor (R4) and the other switch (Tr6) is connected in parallel to the other downstream switching element (Tr4).
A claim for switching to the restricted state by turning on only the switch provided on the downstream side of the upstream switching element among the two switches when the upstream switching element transitions from on to off. Item 1. The electronic control device according to item 1. The H-bridge circuit (3) that drives the motor mounted on the vehicle and
A drive control unit (4) that controls energization of the motor (2) from a DC power supply by controlling the operation of the H-bridge circuit.
Current limiting resistors (R3, R4) for limiting the current flowing through the motor during the non-energized period, which is the period during which the energization of the motor from the DC power supply is stopped.
A switching unit (23) for switching between a limiting state in which the current limiting resistor is interposed in the current path through which the current flows and a normal state in which the current limiting resistor is not interposed in the current path.
Equipped with a,
The switching unit is
A switch (Tr5, Tr6) connected in series to the current limiting resistor is provided.
The current limiting resistor and the series circuit of the switch are connected in parallel to the upstream switching elements (Tr1 and Tr2), which are switching elements provided on the upstream side of the H-bridge circuit.
When the downstream switching elements (Tr3, Tr4), which are switching elements provided on the downstream side of the H-bridge circuit, transition from on to off, the switching unit is brought into the restricted state by turning on the switch. Electronic control device that switches between. The switching unit is
Equipped with two of the above switches
The series circuit of the current limiting resistor (R3) and one of the switches (Tr5) is connected in parallel to the one of the upstream switching elements (Tr1).
The series circuit of the current limiting resistor (R4) and the other switch (Tr6) is connected in parallel to the other upstream switching element (Tr2).
A claim for switching to the restricted state by turning on only the switch provided on the upstream side of the downstream switching element among the two switches when the downstream switching element transitions from on to off. Item 3. The electronic control device according to item 3. The electronic control device according to any one of claims 1 to 4 , wherein the switching unit switches to the restricted state on condition that the rotation speed of the motor is equal to or higher than a predetermined threshold rotation speed. The electronic control device according to any one of claims 1 to 4 , wherein the switching unit switches to the limited state on condition that the induced voltage of the motor is equal to or higher than a predetermined threshold voltage. The electronic control device according to any one of claims 1 to 6 , wherein the motor drives a valve for an internal combustion engine mounted on a vehicle. According to claim 7 , the switching unit switches to the restricted state on condition that the inclination of the opening degree detection signal output from the opening degree sensor for detecting the opening degree of the valve is equal to or greater than a predetermined threshold value inclination. The electronic control device described. The electronic control device according to any one of claims 1 to 8 , wherein the resistance value of the current limiting resistor is variable.

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