JP2002238290A - Motor drive control apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect a conduction current to a motor for operating a DC motor in left and right drive directions by specific output. SOLUTION: When a first arm upper switching element is set to an element A, a first arm lower switching element is set to an element B, a second arm upper switching element is set to an element C, and a second arm lower switching element is set to an element D, a motor application voltage or a motor current is controlled by turning the element A on, and by allowing the element D to be subjected to PWM drive when conduction is made from a first arm toward a second one, and the polarity of current for energizing the motor M is changed by turning on the element B, and by allowing the element C to be subjected to PWM drive when conduction is made from the second arm toward the first one. A shunt resistor RS is inserted between the arm formed by the switching elements A and B and the motor M, and voltage that is generated at both the ends of the shunt resistor RS is amplified, thus detecting the value of current that flows in the motor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive control circuit for a DC motor, and more particularly, to feedback control of a current value while making it possible to switch between a forward direction and a reverse direction of a motor.
The present invention is suitable for application to a device required to control the direction and magnitude of the torque generated by a motor, for example, an electric power steering device.

[0002]

2. Description of the Related Art A permanent magnet or an electromagnet is arranged on a yoke to form a stator, and a magnetic circuit is formed so that a current flows through a coil wound around a rotor via a rectifying brush.
The C motor has a feature that the rotation direction and the generated torque can be easily controlled in accordance with the energizing direction and the energizing current, and is widely used as a servomotor in an application field requiring control of the torque and the rotating direction. For example, as an actuator for a power steering of an automobile, a generated torque and an assist direction are controlled by current-controlling a DC motor to realize a function similar to that of a conventional hydraulic torque assist device.

Here, in order to control the direction of the current applied to the DC motor and the energizing current, as shown in FIG.
It comprises two sets of arms consisting of switching elements C and D,
A so-called H-bridge circuit that drives the DC motor M from the midpoint of each arm (nodes 1 and 2) is used.

In the H-bridge circuit shown in FIG. 8, the upper switching element on the left arm is element A, the lower switching element on the left arm is element B, the upper switching element on the right arm is element C, and the lower switching element on the right arm is element D. .
At this time, pulse width modulation (hereinafter referred to as PWM) is controlled by an arbitrary diagonal switching element, that is, an element A and an element D or an element B and an element C, and the opposite diagonal switching element is turned off. This changes the effective value of the power supply voltage applied to the DC motor, thereby controlling the motor drive current value.

In order to reverse the driving direction, P
This is realized by exchanging a set of switching elements that perform the WM switching operation.

When actually performing the PWM operation of the switching element, both the diagonal elements, that is, the element A (C) and the element D
Even if the element (B) is subjected to PWM switching, only one of the elements A (C) is subjected to PWM switching, and the element D
(B) may be turned on. In the following description, (element) in parenthesis is interchangeable with the immediately preceding element.

[0007] Due to the difference in the PWM drive method, the duration of recirculation of the motor current when the PWM switching is OFF, the switching loss of the switching element of the H-bridge circuit, and the heat generation change. A selection is made.

FIG. 9 shows operation waveforms of various parts when the element A (C) is driven by PWM and the element D (B) is turned on. If the ON resistance of the switching element and the forward voltage drop of the flywheel diode are neglected, the electric time constant determined by the self-inductance of the armature of the motor, the winding resistance, the voltage drop of the brush, etc.
The motor current pulsates according to the PWM carrier frequency and the energization duty. At this time, paying attention to the terminal voltage of the motor at the node 1 (2), the voltage becomes + Vb when the element A (C) is switched on by PWM. On the other hand, when the element A (C) is turned off, the voltage of the node 1 (2) becomes a voltage near 0 V clamped by the diode of the element B (D) and the flywheel current flows because the motor is an inductive load. Therefore, the terminal voltage of the node 1 (2) pulsates at the PWM frequency with the amplitude of the power supply voltage Vb. On the other hand, the terminal voltage of the node 2 (1) is stable at 0V because the element D (B) is constantly driven ON.

By the way, in order to control the flowing current,
It is necessary to detect the current flowing through the motor and perform feedback control on the target current. For this reason, a current detecting means is provided. To detect the motor drive current,
(1) A method of directly reading the current of the motor drive line with a Hall element, (2) A method of inserting a shunt resistor in series in the motor line and amplifying the voltage across the shunt to detect the current, (3)
A method of detecting and amplifying a current flowing through the GND or + B line bus of the H-bridge circuit by an absolute value using a shunt resistor, or the like can be considered.

(1) The current detection method using the Hall element has an advantage that the motor drive current can be directly detected, but the cost of the Hall element is higher than that of an amplifier circuit using an OP amplifier. There is. In addition, variations in detection sensitivity due to the working accuracy of the installation of the Hall element are likely to occur, and it is necessary to take measures against deterioration in accuracy such as drift due to detection offset, temperature, and magnetization.

(2) In the case of a method in which a shunt resistor is inserted in series in a motor line to differentially amplify the voltage across the shunt, as described above, the voltage of the motor line with respect to the GND is changed at the period of the PWM carrier frequency. Since the voltage is fluctuated, in such a conduction mode, there is a problem that the detection accuracy is deteriorated if the common-mode voltage rejection ratio of the differential amplifier circuit cannot be sufficiently ensured.

For example, when the PWM operation frequency of the H-bridge circuit is about 20 KHz, when the amplifier is operated by a single power supply and differentially amplified by an LM324 type OP amplifier widely used in vehicles, the gain bandwidth product is Since the frequency is about 1 MHz, sufficient suppression of common-mode noise due to harmonic components of the PWM carrier frequency cannot be obtained, and differential amplification does not operate correctly, which is not practical.

(3) According to the method of amplifying the current flowing through the bus of the GND or + B line of the H bridge circuit by detecting the absolute value with a shunt resistor, a sample-and-hold circuit for removing the influence of the regenerative current of the PWM. , The detection voltage of the GND or + B line can be
It can be amplified and detected by a general amplifier circuit using a P-amplifier, etc., and has the advantage that the circuit can be easily configured. On the other hand, the current value is detected as an absolute value, so the direction of current flow is unknown. Also, the current flowing through the bus is not the motor current itself, but the detection accuracy is easily deteriorated by the influence of the through current in the upper and lower arms of the switching element and the regenerative current when the PWM is turned off. There's a problem.

[0014]

As described above, according to the prior art, if the current of the motor wire is directly detected, it is disadvantageous in terms of cost, but it is realized by using a Hall element. Alternatively, it has to be realized by configuring a differential amplifier circuit employing an expensive OP amplifier having particularly excellent gain bandwidth product.

To configure a current detection circuit using a general OP amplifier, a shunt resistor for detection is inserted into the + B line or the GND line of the H bridge circuit, and the bus current is sampled and held for detection. Therefore, an error due to the influence of the through current of the H-bridge circuit occurs due to the operation principle, and an operation for calculating an average current for each driving cycle is required.
It is difficult to detect the current in the regenerative mode, and there is a problem that the accuracy is inferior to the case where the current value of the motor line is directly read.

The present invention has been made to solve such a problem, and a circuit capable of directly detecting a drive current value of a motor driven by PWM by an H-bridge circuit using an inexpensive general-purpose OP amplifier. The purpose is to provide a scheme.

[0017]

A motor drive control device according to the present invention includes two sets of arms each comprising two serially connected switching elements, and each of the arms has a D point from the midpoint of each arm.
In a motor drive control device using a so-called H-bridge circuit configured to drive a C motor, a first arm upper switching element is element A, a first arm lower switching element is element B, a second arm upper switching element is element C, When the lower switching element of the second arm is the element D, the element A is turned on when the current is supplied from the first arm to the second arm, and the motor D is driven by PWM to control the motor applied voltage or motor current. When current is supplied from the second arm to the first arm,
N and the element C are PWM-driven to switch the polarity of the current supplied to the motor and to control the voltage or current applied to the motor.

Further, in the motor control device according to the present invention, when the polarity of the switch is switched to switch the motor driving direction, all the switching elements (switches) are switched before the transition from the energizing direction before switching to the energizing direction after switching. A ~
A predetermined dead time for turning off D) is provided.

Also, a shunt resistor is connected between the middle point of the elements A and B and the motor, and a voltage generated at both ends of the shunt resistor is amplified according to the motor current, thereby detecting the motor drive current. It is configured to include a detecting means.

Further, the motor current control is performed by feeding back a detection value detected by the current detection means to a motor drive current command value.

Further, the motor drive current value is monitored to be within a predetermined range by using the detection value detected by the current detection means, and the motor drive is prohibited in the event of an abnormality.

Further, the apparatus is configured so as to correct the offset error of the current detection value in accordance with the polarity of the current supplied to the motor.

In order to measure the offset of the current detection circuit in accordance with the polarity of the current supplied to the motor, only the element A is turned on at the time of start-up to supply a current from the first arm to the second arm. The detection offset is measured, and then only the element B is turned on to measure the detection offset when power is supplied from the second arm to the first arm. Based on the measured value, the error of the offset of the current detection value is measured. Is corrected.

Further, a nonvolatile storage means capable of storing correction data without backup of a power source is provided, and the nonvolatile storage means holds an offset compensation value of a current detection value corresponding to each of the energizing directions of the motor, and based on the value, It is configured to correct an offset error of a current detection value.

Further, an N-channel type power MOSFET is used as a switching element.

Further, a P-channel type power MOSFET is used for the element A and the element C and an N-channel type power MOSFET is used for the element B and the element D as the switching element.

Further, an NPN-type bipolar transistor is used as a switching element.

Further, as the switching elements, PNP type bipolar transistors are used for the elements A and C, and NPN type bipolar transistors are used for the elements B and D.

Further, the PWM carrier frequency is set higher than the audible frequency.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, a motor drive control device according to a first embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing a motor drive control device according to the first embodiment. In the H-bridge circuit of FIG. 1, the left-arm upper switching element is element A, the left-arm lower switching element is element B, the right-arm upper switching element is element C, and the right-arm lower switching element is element D. In this embodiment, N-channel enhancement type MOSs are used as the switching elements A to D.
Use FET. That is, the drain and the G
Two sets of M connected in cascade so as to become sources at the ND side potential
An arm 1 (first arm) composed of the OSFET elements A and B and an arm 2 (second arm) composed of the elements C and D are provided, and a midpoint between the arms 1 and 2 (nodes 1 and 2 respectively) ) Of the motor M.

Each of the switching elements A to D is connected to the source when the gate applied voltage is 0 V with respect to the source voltage.
The continuity between the drains is cut off and turned off. Also, if the gate applied voltage is sufficiently higher than the source voltage than the threshold voltage Vth, there is sufficient conduction between the source and the drain to turn ON.
It becomes.

Further, a shunt resistor Rs is placed between the motor M and the motor drive terminal output from the arm 1 formed by the switching elements A and B, and a voltage corresponding to the current flowing through the motor M is applied to both ends of the shunt resistor Rs. Is to be detected.

The voltage across the shunt resistor Rs is equal to the resistor R1
The signal is input to an OP amplifier (OPA1) via a resistor R2. The positive-phase input of OPA1 is connected to a reference power source (for example, 5
V3) and GND so that the midpoint voltage (2.5 V) becomes the zero point of the detected current value with a resistance value of R3 = R4. The resistor R5 performs feedback from the output terminal of the OPA1 to the negative phase input, and R5 × 2 = R3 =
The value is selected to be R4. The resistor R6 and the capacitor C1 are a first-order lag LPF circuit, and have an object of removing a PWM carrier included in the detection current as necessary.

By feeding back this output as a feedback signal for the target current, the FET drive direction and drive duty are controlled, and current feedback control is performed.

Now, when the motor drive current flowing from the arm 1 to the arm 2 is positive and Im (A), a voltage of Im × RS (Equation 1) is generated at both ends of the shunt resistor RS. , OPA1
id = Vid = 2.5 + Im × RS × R5 / R2 (V) (Equation 2)

Next, a method of driving the gate of each FET in the motor drive control device of the present embodiment will be described in detail. First, when the driving of the motor is stopped, the switching elements A to D are all turned off by setting the gate supply voltages of all the FETs to 0 V, and the motor is not driven.

Next, when a current is supplied in the direction from the arm 1 to the arm 2 (right drive), among the switching elements A to D, as shown in FIG. Is OFF, the element C is OFF, and the element D is PWM. By operating each gate drive in this manner, the voltage between both terminals of the motor is changed according to the duty of the PWM of the element D, and the energized current is changed. At this time,
The output of the arm 1, that is, the potential of the shunt resistor RS connection point, is substantially VB during the PWM operation because the element A is ON.
It is stable.

Conversely, when a current is supplied from the arm 2 to the arm 1 (to be driven left), as shown in FIG. 3, the element A is turned off, the element B is turned on, the element C is PWM, and the element C is PWM. D is turned off, the voltage between both terminals of the motor is changed according to the duty of the PWM of the element C, and the energizing current is changed. Therefore, when a current is supplied from the arm 2 to the arm 1, the output of the arm 1, that is, the potential of the connection point of the shunt resistor RS is always approximately 0 V during the PWM operation because the element B is ON, which is stable. .

By driving each of the switching elements A to D as described above, the common-mode voltage component generated between the two terminals of the shunt resistor RS becomes +
VB, 1/2 of the reference voltage when the motor is off, and 0 V when driving left, so that no high-frequency common-mode voltage derived from the PWM carrier is generated.

Therefore, in the differential amplifier circuit composed of the OPA1 and R1 to R5, it is not necessary to design a high common mode voltage rejection ratio at a high frequency, so that the current pulsation due to the switching is prevented from being heard as the operation sound of the motor. Even when the design is performed with an external PWM frequency, an excellent effect is obtained in that the motor drive current can be measured reliably and easily with an inexpensive general-purpose OP amplifier.

Embodiment 2 In the second embodiment of the present invention, when the motor driving direction is switched, a pause time (dead time) for turning off all the switching elements A to D for a predetermined time is always provided.

For example, in the motor drive control device shown in FIG. 1, in order to set the drive direction to the right (right drive), among the switching elements A to D, the element A is turned on, the element B is turned off, the element C is turned off, The operation is realized by applying a right drive current to the motor M with the element D as a PWM. When the driving direction is reversed from this state to the left (left driving),
The element A is turned off, the element B is turned on, the element C is switched between PWM and the element D is turned off. However, due to a delay in the operation of the switching element, the elements A and B and the elements C and D are switched.
The upper and lower elements of each arm are simultaneously turned on, and as a result, a large through current may flow through each arm.
Therefore, a dead time during which all the switching elements A to D are turned off is provided at the time of driving switching in consideration of the switching delay of the elements, so that a through current does not occur.

Assuming that the PWM drive duty is generated by a micro control unit (MCU) (not shown), the PWM duty is updated along with the drive direction every predetermined control cycle by the function of a timer built in the MCU, and the output PWM timer is output. Is set to Therefore,
When the previous driving direction is different from the current driving instruction direction, for example, after turning off all the switching elements for one control cycle and completely turning off the switching elements, the energization is restarted in the next control cycle. Just fine.

Here, the element A and the element B are ON / OFF.
Since only the operation is performed, the turn ON and the turn O
Although the speed of the FF may be low, it is needless to say that the drive circuits preceding the elements A and B should be driven so that at least the turn-off is completed within the control cycle.

Embodiment 3 In the third embodiment of the present invention, the output value of the differential amplifier circuit is monitored, and if the current detection value is abnormal, the current feedback control is turned off and the motor drive is stopped.

According to the circuit configuration of FIG. 1, the operational amplifier OP
The current detection signal appearing through the differential amplifier including A1 and the resistors R1 to R5 and the low-pass filter including the resistor R6 and the capacitor C1 is 2.5 V when the motor current is zero, and increases as the right current increases. For example, the detection voltage should increase toward 5V, and if the left conduction current increases, the detection voltage should decrease toward 0V. However, if the current detection value indicates an incorrect value deviating from 2.5 V even when the motor drive is OFF due to a failure of the current detection circuit, the current detection circuit may determine that the current detection circuit is abnormal and turn off the motor drive.

For accuracy, when the motor is rotated by an external force to generate an induced voltage, if the voltage is larger than the voltage of the + B line, the element A and the element D or the element B and the element C depending on the rotation direction. Since a current that flows back to the power supply via the flywheel diode is generated, erroneous detection may occur. Therefore, for example, as shown in FIG. 4, a motor terminal voltage monitoring means is provided to monitor the motor terminal voltage,
Only when the voltage between the motor terminals is lower than the power supply voltage VB, the failure of the current detection circuit may be determined.

Embodiment 4 In the fourth embodiment of the present invention, the resistors R1 to R5 and each OP
A detection error caused by variations in elements such as an offset voltage inherent to the amplifier is measured in advance, and the current feedback signal is corrected according to the operation of the H-bridge circuit and the power supply voltage.

In the circuit of FIG. 1, R3 = R4 and R3
The operation has been described assuming that 5 × 2 = R3 = R4 and there is no offset of the OP amplifier (OPA1). However, in practice, there is a value error in the resistors constituting the circuit, and the offset variation also occurs in the OP amplifier. Therefore, the detection value has an error due to these effects.

In the circuit of FIG. 4, R3 // R4 = R
4 ′, R1 = R2 + dR2, R4 ′ = R5 + dR
5 is assumed. However, dR2 and dR5 are dR2 << R2,
It is a small constant value that satisfies dR5 << R5. The voltage on the R1 side of the shunt resistor is V1, and the voltage on the R2 side of the shunt resistor is V
2. Assuming that the OPA offset voltage is Vf and the output voltage is Vo, Vo is approximately given by the following equation.

Vo {R5 / R2 × (V1-V2) + 1 / R2 × {dR5 + R5 / (R2 + R5) × (dR2 + dR5)} × V1 + Vbias × (1 + dR5 / R2 + R5 / R2 × (dR2 + dR5) / (R2 + R5) − (R2 + R5) R2 + R5) / R2 × Vf ｆDifferential voltage amplification + In-phase voltage amplification + Bias voltage + OP amplifier offset component amplification (Equation 3)

However, differential voltage amplification = R5 / R2 × (V1-V2) (Equation 4) In-phase voltage amplification {1 / R2 × {dR5 + R5 / (R2 + R5) × (dR2 + dR5)} × V1 (Equation 5) Bias voltage ΔVbias × (1 + dR5 / R2 + R5 / R2 × (dR2 + dR5) / (R2 + R5) (Equation 6) Vbias = R4 / (R3 + R4) × Vcc (Equation 7) OP amplifier offset component amplification = − (R2 + R5) / R2 × Vf (Equation 8)

The following holds. Since the characteristics required as the current detection value are the differential voltage amplification (Equation 4) and the accurate bias voltage component (Equation 7), it may be corrected to suppress other remaining error components.

If the motor drive is turned off, the motor current value is zero, so that V1 = V2 = Vbias (Equation 9)

The detection offset determined by each term component of (Equation 5) to (Equation 8) under the condition of (1) can be learned. This offset value is for all switching elements (elements A to D)
Is applicable when is OFF.

Next, the element B is turned on, and the elements A, C, and D are set to O.
If FF is set, the common mode voltage V1 = V2 while the motor is off
= 0V, and the detection error (Ver_l) of the current detection circuit at the time of the left drive in the first embodiment can be measured.
At the time of the main measurement, the bias voltage (Equation 6) and the OP amplifier offset component (Equation 9) can be measured because the common-mode voltage is 0 V.

Further, the element A is turned on, and the elements B, C, and D are set to O.
If it is FF, the motor is OFF and the common mode voltage V1 = V2 =
The state becomes VB, and the detection error (Ver_h) of the current detection circuit at the time of right driving in the first embodiment can be measured. This detection error consists of the common-mode voltage amplification (Equation 5), the bias voltage (Equation 6), and the OP amplifier offset component (Equation 9).

Accordingly, since only the common-mode voltage amplification (Equation 5) included in Ver_h has the power supply voltage dependency, the power supply voltage VB is successively measured during motor control.

Ver_h ′ = (Ver_h−Ver_l) × VB / VB0 + Ver_1 (Equation 10) where VB0 is the power supply voltage at the time of measuring Ver_h.

In this case, it is possible to obtain a feedback signal in which the detection error is appropriately corrected according to the power supply voltage.

Here, Ver_h and Ver_l may be measured by an initial check when the motor drive control device is powered on. Further, the measurement may be performed at the time of shipment of the motor drive control device, and may be written to the nonvolatile memory and stored.

In the above description, the ON resistance of the switching elements A and B was ignored and the node 1 voltage when the motor was turned off was equal to the power supply voltage VB or 0 V. However, the ON resistance could not be ignored. Even when the voltage of the node 1 fluctuates from VB or 0 V due to a voltage drop due to the flowing current, if the voltage VM + of the node 1 is directly monitored and changed to the above VB and substituted into (Equation 10) to calculate the detection error, the accuracy is obtained. A simple detection error can be easily obtained.

Embodiment 5 In the first to fourth embodiments, the switching elements A to D are all NchMOS
Although the description has been made on the assumption that the FET is used, the element A and the element C may be Pch MOSFETs as shown in FIG. In this case, the drains of the respective elements are connected to the node 1 and the node 2 serving as the motor drive output terminals, and in the right drive and the left drive, a symmetric switching operation is performed in which all the switching elements operate with the source grounded. The operation method of each of the elements A to D is the same as the operation of the corresponding element A to D in the first embodiment of FIG.

Embodiment 6 FIG. A bipolar transistor may be used as a switching element. FIG. 6 shows a circuit constituted by NPN transistors. FIG. 7 shows a case where a PNP transistor is used on the power supply line side and an NPN transistor is used on the GND side. The operation method of each of the elements A to D is the same as the operation of the corresponding elements A to D in the first embodiment of FIG.

In the above embodiment, the motor is used as the load. However, when the present invention is applied to the driving of another actuator element such as a linear solenoid which needs to switch the driving direction, the same as when the motor is driven. Current control is possible.

[0067]

Since the motor drive control device of the present invention is constructed as described above, it has the following effects.

First, in a motor drive control device using a so-called H-bridge circuit, which includes two sets of arms each including two serially connected switching elements, and drives a DC motor from the midpoint of each arm, When the upper arm switching element is element A, the first lower arm switching element is element B, the second upper arm switching element is element C, and the second lower arm switching element is element D, the first arm to the second arm The element A is turned on when the current is supplied to the first arm, the motor applied voltage or the motor current is controlled by driving the element D by PWM, and the element B is turned on when the current is supplied from the second arm to the first arm. The polarity of the current supplied to the motor is switched by PWM driving C and the voltage or current applied to the motor is switched. It was configured to control.

As a result, the PWM switching is always performed at the second
Since the operation is performed by the element C or the element D of the arm, there is obtained an effect that the carrier frequency component of the PWM does not greatly appear in the output potential of the first arm in the PWM operation in either the left or right energizing direction.

Further, a current detecting means is provided in which a shunt resistor is connected between the middle point of the elements A and B and the motor, and a motor drive current is detected by amplifying a voltage generated at both ends thereof in accordance with the motor current. Means, it is possible to easily suppress high-frequency components derived from the PWM carrier at the stage of the signal input to the differential amplifier, and to use a general-purpose differential amplifier circuit having the same performance as the common-mode voltage rejection ratio. Also, only the detected current component can be easily amplified.

Further, when the polarity of the switch is switched to switch the motor driving direction, all switching elements (A to D) are turned off before shifting from the energizing direction before switching to the energizing direction after switching. Since the dead time is provided, it is possible to prevent a through current from flowing when the upper and lower elements of each arm of the H-bridge circuit overlap and turn on at the same time even when the direction of the current supplied to the motor is reversed.

Further, it is possible to provide a means for directly detecting the motor energizing current value, which is more accurate than the current flowing through the bus such as the power supply side and the GND side of the H bridge circuit which has been widely performed conventionally. Since the energized current value in any operating state such as powering, regenerative braking, and braking of the motor can be detected, the control performance of the current feedback with respect to the motor drive current command value is improved.

Also, by using the detection value detected by the current detection means to monitor that the motor drive current value is within a predetermined range and to prohibit the motor drive in the event of an abnormality, the circuit is controlled from the abnormal current. Can be prevented from being burned out and short-circuiting of the element can be prevented.

Further, since the error of the offset of the detected current value is corrected in accordance with the polarity of the current supplied to the motor, the influence of the detection error due to the DC common mode voltage component generated in each driving direction can be canceled. Thus, highly accurate current feedback control can be realized.

At the time of startup, only the element A is first turned on to measure a detection offset when power is supplied from the first arm to the second arm. Then, only the element B is turned on and the second arm is turned on. Since the detected offset when energizing toward the arm is measured and the error of the offset of the current detection value is corrected based on each measured value, the offset voltage due to the variation of the elements of the current detection circuit is corrected. It is possible to improve the accuracy of the current detection value by self-correcting the individual difference for each device.

Further, there is provided a non-volatile storage means capable of storing correction data without backup of the power supply, and the non-volatile storage means holds an offset compensation value of a current detection value corresponding to each of the energizing directions of the motor, and based on the value, Since the offset error of the current detection value is corrected, the accuracy of the current detection value can be improved by measuring the offset voltage in each energizing direction, such as in the manufacturing stage of the device, and storing the correction value.

Further, since the power supply voltage during motor control is monitored and the offset error is calculated according to the read value, the detection error caused by the fluctuation of the power supply voltage can be corrected, and the accuracy of the current detection value can be improved. Can be improved.

Further, since the motor terminal voltage during motor control is monitored and the offset error is calculated according to the read value, the influence of the ON resistance of the switching element constituting the H bridge circuit of the motor drive circuit is obtained. Therefore, even if the voltage applied to the motor decreases, the fluctuation of the detection error due to the reduction can be estimated, so that the compensation can be easily performed. Therefore, the accuracy of the current detection value can be improved.

Further, according to the present invention, the N-channel type power M
A motor drive circuit can be realized using OSFET, and +
The switching element on the power supply side is a P-channel type power M.
OSFET and Nch power MOSFET on GND side
TPN or all of the H bridge circuits are NPN
It can be applied to various power elements such as a circuit using a bipolar transistor, a switching element on the + power supply side as a PNP bipolar transistor, and a circuit using an NPN bipolar transistor on the GND side.

Even if the PWM carrier frequency is set higher than the audible frequency, the common-mode voltage component generated between the two terminals of the shunt resistor RS is determined by + VB during right driving and the reference when the motor is off according to the driving direction. Since the voltage is １ ／ of the voltage and becomes 0 V at the time of the left driving, a high frequency common mode voltage derived from the PWM carrier is not generated. Therefore, the differential amplifier circuit including the OPA1 and R1 to R5 is designed to have a high common mode voltage rejection ratio at high frequency. It is not necessary to perform the operation, and even if the design is made to have a PWM frequency outside the audible frequency so that the current pulsation due to switching is not heard as the motor operation sound, the motor drive current can be measured reliably and easily by using an inexpensive general-purpose OP amplifier. It becomes possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a circuit configuration of a motor drive control device according to Embodiments 1, 2, and 3 of the present invention.

FIG. 2 shows an H-bridge circuit element D according to the first embodiment.
FIG. 6 is a diagram for explaining operating voltage / current waveforms of each unit when PWM operation is performed.

FIG. 3 shows an H-bridge circuit element C according to the first embodiment.
FIG. 6 is a diagram for explaining operating voltage / current waveforms of each unit when PWM operation is performed.

FIG. 4 is a diagram showing a circuit configuration of a motor drive control device according to a fourth embodiment of the present invention.

FIG. 5 is a diagram showing a circuit configuration of a motor drive control device according to a fifth embodiment of the present invention.

FIG. 6 is a diagram showing a circuit configuration of a motor drive control device according to a sixth embodiment of the present invention.

FIG. 7 is a diagram showing a circuit configuration of a motor drive control device according to a sixth embodiment of the present invention.

FIG. 8 is a circuit diagram showing a conventional H-bridge circuit for PWM driving a motor.

FIG. 9 is a diagram for explaining operating voltage / current waveforms of each unit in the operation of the conventional H-bridge circuit.

[Explanation of symbols]

1 1st arm, 2nd arm, A, B, C, D switching element, M motor, R1-R6 resistor, RS
Shunt resistor, C1 capacitor, OPA1 operational amplifier.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H571 AA03 CC02 DD01 EE02 GG04 HA09 HC01 HD02 JJ25 LL22 MM02 5J055 AX27 AX44 AX55 AX56 AX64 AX65 AX66 BX16 CX20 CX28 DX04 DX05 DX13 DX14 DX15 DX22 DX60 EZ01 FX10 EZ01 FX04 GX04

Claims (15)

[Claims] 1. An arm having two sets of two switching elements connected in series, each of which has a center point D
In a motor drive control device provided with an H bridge circuit adapted to drive a C motor, a first arm upper switching element is element A, a first arm lower switching element is element B, and a second arm upper switching element is element C. When the lower switching element of the second arm is the element D, the element A is turned on when energizing from the first arm to the second arm, and the motor applied voltage or motor current is controlled by driving the element D by PWM. When current is supplied from the second arm to the first arm, the element B is turned on, and the element C is PWM-driven to switch the polarity of the current supplied to the motor and to control the motor applied voltage or motor current. A motor drive control device, characterized in that: When switching the polarity of a switch to switch a motor driving direction, a predetermined turning-off of all switching elements (A to D) is performed before a transition from an energizing direction before switching to an energizing direction after switching is performed. The motor drive control device according to claim 1, wherein a dead time is provided. 3. A current detection for detecting a motor drive current by connecting a shunt resistor between the midpoint of the switching elements A and B and the motor, and amplifying a voltage generated at both ends according to the motor current. The motor drive control device according to claim 1, further comprising a unit. 4. The motor drive control device according to claim 3, wherein the motor current control is performed by feeding back a detection value detected by the current detection means to a motor drive current command value. 5. The method according to claim 3, wherein a motor drive current value is monitored to be within a predetermined range by using a detection value detected by the current detection means, and when an abnormality is detected, driving of the motor is prohibited. Item 5. A motor drive control device according to item 4. 6. The apparatus according to claim 3, further comprising a current detecting means for correcting an offset error of a current detection value in accordance with a polarity of a current supplied to the motor.
The motor drive control device according to any one of claims 1 to 5. 7. At the time of startup, only the element A is first turned on and the first
The detection offset when energizing from the arm to the second arm is measured, and subsequently, only the element B is turned ON to measure the detection offset when energizing from the second arm to the first arm. 7. The motor drive control device according to claim 6, wherein the error of the offset of the current detection value is corrected based on the obtained value. 8. A nonvolatile storage device capable of storing correction data without a backup of a power supply, wherein the nonvolatile storage device holds an offset compensation value of a current detection value corresponding to each of the energizing directions of the motor, and based on the value. 7. The apparatus according to claim 6, wherein an error in the offset of the detected current value is corrected.
3. The motor drive control device according to claim 1. 9. The motor drive control device according to claim 7, wherein a power supply voltage during motor control is monitored, and an error of the offset is calculated according to the read value. 10. The motor drive control device according to claim 7, wherein a motor terminal voltage during motor control is monitored, and an offset error is calculated according to the read value. 11. The motor drive control device according to claim 1, wherein an N-channel type power MOSFET is used as the switching element. 12. The switching device according to claim 1, wherein a P-channel type power MOSFET is used for the element A and the element C, and an N-channel type power MOSFET is used for the element B and the element D. 3. The motor drive control device according to claim 1. 13. The motor drive control device according to claim 1, wherein an NPN-type bipolar transistor is used as the switching element. 14. The switching element according to claim 1, wherein a PNP transistor is used for the element A and the element C, and an NPN transistor is used for the element B and the element D. Motor drive control device. 15. The motor drive control device according to claim 1, wherein the PWM carrier frequency is set higher than the audible frequency.