JP2000168605A - Motor driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor driving device which comprises a motor driving means for driving a motor, composed of two bridge circuits whose power source voltage and a motor load current are detected so as to change over the bridge circuits in order to efficiently and optimumly drive the motor for obtaining a large thrust force. SOLUTION: An electrically driven power steering device 11 is composed of a control means 2, a motor driving means 3 and a motor current detecting means 4, the motor driving means 3 being composed of two bridge circuits using six switching elements 6 such as FETs, that is, a first bridge circuit for supplying a first power and a second bridge circuit for supplying a second power, which are used being changed over in accordance with a power source voltage and a load current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a motor driving means for driving a motor which comprises two bridge circuits, detects a power supply voltage value of each bridge circuit or a drive current value of the motor, and switches the bridge circuit. The present invention relates to a motor drive device capable of efficiently and optimally driving a motor.

[0002]

2. Description of the Related Art In a conventional motor driving apparatus, motor driving means for driving a motor is constituted by a bridge circuit comprising four FETs (field effect transistors), and the FETs are controlled by a PWM (pulse width modulation) signal from a control means. 2. Description of the Related Art There is known an apparatus configured to drive and control a motor with a desired motor current in forward and reverse directions.

FIG. 7 shows a block diagram of a conventional motor driving device. In FIG. 7, the motor driving device 51 includes a control unit 52 and a motor driving unit 53. The control means 52 includes various arithmetic means based on a microprocessor,
It comprises a processing means, a signal generation means, a memory and the like, and includes a target current signal setting means 56 and a drive control means 57.

The target current signal setting means 56 is provided with a memory such as a ROM or the like. When a preset sensor signal Si is inputted, a correspondence data between a value corresponding to the sensor signal Si and a target current signal IMS is stored, A corresponding target current signal IMS is read based on the input value of the signal Si,
It is supplied to the drive control means 57.

The drive control means 57 includes a PID (proportional / integral / differential) controller for performing PID control on the target current signal IMS, a one-system ON signal VON and a two-system OFF signal based on the PID-controlled signal. Switching signal generator for generating VOF, PWM for generating PWM signal VPWM
M generator, etc., and outputs a PWM signal VPWM having a duty cycle corresponding to the PID signal and a hybrid signal of the ON signal VON and the OFF signal VOF to the motor control signal V0 (VPWM, VPWM
(ON, VOF) to the motor drive means 53.

The motor drive means 53 receives from the control means 52 a motor control signal V0 (VPWM, VON, VOF) as a composite signal of the one-system ON signal VON, the two-system OFF signal VOF, and the one-system PWM signal VPWM. Motor driving means 5
The switching elements are supplied to FETs (field effect transistors) Q1 to Q4 constituting the three switching elements.

For example, in order to rotate the motor 55 in the forward direction, an FET constituting a switching element of the motor driving means 53
(Field Effect Transistor) The ON signal V0N is applied to the gate G1 of Q1, the OFF signal VOF is applied to the gate G2 of Q2, the OFF signal VOF is applied to the gate G3 of Q3, and the PWM signal V is applied to the gate G4 of Q4.
PWM is supplied, Q1 is set to ON, Q2 and Q3 are set to OFF, Q4 is set to ON / OFF determined by the duty cycle of the PWM signal VPWM, and the motor current IM + is changed from power supply 12V → Q1 → motor 55 → Q4 → The motor 55 flows forward on the ground (ground) path and rotates forward.

On the other hand, to reverse the rotation of the motor 55, the gate G2 of the FET (field effect transistor) Q2 of the motor driving means 53 is connected to the gate G2 of the ON signal VON, Q1.
1 is an OFF signal VOF, and a PWM signal VPW is applied to a gate G3 of Q3.
An off signal VOF is supplied to the gates G4 of M and Q4, Q2 is set to on, Q1 and Q4 are set to off, and Q3
Is set to ON / OFF determined by the duty cycle of the PWM signal VPWM, and the motor current IM-
The electric motor 55 rotates in the reverse direction, flowing along the path of → Q2 → motor 55 → Q3 → ground (ground).

[0009]

However, when a conventional motor drive device is used as a drive device for a motor mounted on an automobile, the use of electric current increases with the increase in the number of automobile electrical components, and sufficient electric power is supplied. There is a problem that it cannot be obtained. Further, when a large current is applied to the motor to obtain a large thrust, there is a problem that a sufficient thrust cannot be obtained due to a voltage drop due to the large current and a back electromotive force of the motor. Furthermore, if the voltage supplied to the electric motor is increased to obtain a large thrust, it is necessary to control a small current, and there is a problem that the control is difficult.

[0010] The present invention has been made to solve such a problem, and an object of the present invention is to provide a first bridge circuit for supplying a first power supply and a second bridge circuit for supplying a second power supply. By switching and driving the motor according to the state of the power supply voltage or the state of the motor drive current, it is possible to increase the thrust due to the large current and finely control the small current, increase the efficiency of the motor, and increase the power supply voltage of each bridge circuit. Depending on the state, the first power supply and the second power supply are switched to drive the electric motor, so that the reliability of the device is improved.

[0011]

According to the present invention, there is provided an electric motor driving device comprising: a first bridge circuit connected between a first power supply and a ground; A second bridge circuit connected between the second power supply and ground (ground), and a motor driven by the bridge circuit, wherein the first bridge circuit is connected to ground (ground). One FET is shared with the FET on the ground side of the second bridge circuit, and drives the motor based on a control signal from the control means.

[0012] The motor driving means of the motor driving device according to the present invention comprises a first bridge circuit connected between the first power supply and ground (ground), and a second power supply and ground (ground). A second bridge circuit connected between the two bridges, and an electric motor driven by the bridge circuit, wherein the first bridge circuit is connected to ground (ground).
Is used in common with the FET on the ground side of the second bridge circuit, and drives the motor based on a control signal from the control means. Therefore, the two bridge circuits can be switched and driven under the control of the shared bridge circuit. .

Further, the control means according to the present invention comprises switching control means for switching to driving of the first bridge circuit when the voltage value of the second power supply falls below a predetermined value during driving of the second bridge circuit. It is characterized by having.

The control means according to the present invention includes the switching control means for switching to driving the first bridge circuit when the voltage value of the second power supply falls below a predetermined value during driving of the second bridge circuit. When the voltage drop of the second power supply voltage is large, the motor can be driven by the first power supply and the first bridge circuit.

Further, the control means according to the present invention comprises switching control means for switching between driving of the second bridge circuit or driving of the first bridge circuit according to the drive current value detected by the motor current detection means. Features.

The control means according to the present invention comprises switching control means for switching between driving of the second bridge circuit or driving of the first bridge circuit according to the driving current value detected by the motor current detecting means, so that the efficiency is high. Can control.

Further, the switching control means according to the present invention includes a duty ratio coefficient generating means for generating a coefficient signal inversely proportional to the voltage value detected by the power supply voltage detecting means.

Since the switching control means according to the present invention includes the duty ratio coefficient generating means for generating a coefficient signal inversely proportional to the voltage value detected by the power supply voltage detecting means, the same motor current can be obtained even when the power supply voltage changes. Can be shed.

Further, the motor driving means according to the present invention is characterized in that a backflow preventing diode is inserted between the first power supply and the first bridge circuit and between the second power supply and the second bridge circuit. And

In the motor driving means according to the present invention, a diode for preventing backflow is inserted between the first power supply and the first bridge circuit and between the second power supply and the second bridge circuit. During use of the power supply, it is possible to prevent a current from flowing back to the other power supply.

[0021]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In the present invention, the first bridge circuit for supplying the first power to the motor driving means for driving the motor and the second bridge circuit for supplying the second power are connected to the state of the power supply voltage or the load current. By switching and using depending on the state, the motor is driven by an increase in thrust due to a large current and fine control of a small current, so that the efficiency of the motor is increased. The power is switched to drive.

FIG. 1 is an overall configuration diagram of an embodiment in which an electric motor driving device according to the present invention is applied to an electric power steering device. In FIG. 1, a power steering device 1
Reference numeral 1 denotes a steering gear box 14 via a connecting shaft 13 having universal joints 13a and 13b on a steering shaft 12 provided integrally with a steering wheel 28.
15a of the rack & pinion mechanism 15 provided in the inside
To form the manual steering force generating means 16.

Rack teeth 17a meshing with the pinion 15a
The rack shaft 17 which reciprocates by meshing with the rack shaft 17 has left and right front wheels 19 as rolling wheels connected to both ends thereof via tie rods 18.

Thus, the steering wheel 2
At the time of 8 steering, the front wheels 19 are driven by manual steering via a normal rack and pinion type manual steering force generating means 16.
To change the direction of the vehicle.

In order to reduce the steering force by the manual steering force generating means 16, the electric motor 5 for supplying the steering assist force is arranged coaxially with the rack shaft 17, and the ball screw mechanism 21 provided coaxially with the rack shaft 17 is provided. And acts on the rack shaft 17 (ball screw shaft 21a).

A steering torque sensor 22 for detecting the direction and magnitude of a driver's manual steering torque is disposed in the steering gear box 14, and the steering torque of an analog electric signal corresponding to the steering torque detected by the steering torque sensor 22. The signal Ts is provided to the control means 2. The vehicle speed sensor 24 detects an electric pulse signal having a frequency corresponding to the speed of the vehicle, and provides the control unit 2 with a vehicle speed signal Vs.

The control means 2 generates a motor control signal V0 (a mixed signal of an ON signal, an OFF signal and a PWM signal) corresponding to a steering torque signal Ts corresponding to the vehicle speed signal Vs, and controls the driving of the motor drive means 3. .

The control means 2 feeds back the motor current signal IM0 from the motor current detection means 4 and outputs a motor control signal V0 to the motor drive means 3 so that the motor current IM always becomes a target value.

The motor driving means 3 is composed of two bridge circuits using six switching elements such as FETs (field effect transistors), and is composed of a switch on / off signal and a PWM signal provided from the control means 2. Two pairs of FETs consisting of two pairs with the motor control signal V0
By controlling the driving of each pair of
Set the voltage value and rotation direction of the motor voltage supplied to the motor.

The motor current detecting means 4 differentially amplifies a voltage drop of the motor current IM flowing through a current detecting element (for example, a resistor) connected in series with the motor 5, and outputs a motor current signal corresponding to the amplified output. It supplies IM0 to the control means 2.

FIG. 2 is a block diagram of a main part of an embodiment of an electric motor driving device of an electric power steering device according to the present invention. In FIG. 2, the electric power steering device 1
1 comprises a control means 2, a motor driving means 3, and a motor current detecting means 4.

The control means 2 comprises various arithmetic means, processing means, signal generating means, memory and the like based on a microprocessor. The target current signal setting means 6, deviation calculating means 20,
A drive control means 7 and a switching control means 8 are provided.

The target current signal setting means 6 has a memory such as a ROM, and stores corresponding data of the steering torque signal Ts and the target current signal IMS using the vehicle speed signal Vs set in advance as a parameter. Based on the detected vehicle speed signal Vs and the steering torque signal Ts detected by the steering torque sensor 22, a corresponding target current signal IMS is read and supplied to the deviation calculating means 20.

The deviation calculating means 20 has a subtraction function, calculates a deviation between the target current signal IMS and the motor current signal IM0 from the motor current detecting means 4, and calculates a deviation signal ΔI (= IMS-I
M0) is supplied to the drive control means 7.

The drive control means 7 includes a PWM generator for generating a PWM signal VPWM, a switching signal generator for generating a one-system ON signal VON and a two-system OFF signal VOF, a multiplier, and the like. The PID control is performed on the deviation signal ΔI (= IMS−IM0) between the target current signal IMS and the motor current signal IMO supplied from the means 20, and a PWM signal VP having a duty cycle corresponding to the PID signal IPID.
WM and a mixed signal of the ON signal VON and the OFF signal VOF
It is supplied to the switching control means 8 as a motor control signal V0 (VPWM, VON, VOF).

When the switching control means 8 receives the bridge switching signal J, the switching control means 8 switches to drive the first bridge circuit or the second bridge circuit based on the voltage value or the current value of the bridge switching signal J. Thereby, the motor control signal V0 (VPWM, VON, VOF) of the simultaneous input is supplied to the motor driving means 3 as the motor control signal V01 or the motor control signal V02.

The bridge switching signal J is output from the motor driving means 3
The first power supply voltage E01 (12V) and the second power supply voltage E02 (24V) or the motor current signal IM0.

The motor driving means 3 is composed of two bridge circuits using six switching elements such as FETs (field effect transistors), and FETs Q1, Q2, Q3, Q
4 together with the first bridge circuit.
5, Q6, Q3, and Q4 form a second bridge circuit.

The anode of the backflow prevention diode 9 is connected to the first power supply voltage E01 (12 V), and the drains of the FETs Q1 and Q2 are connected to the cathode of the backflow prevention diode 9. The sources of the FETs Q1 and Q2 are connected to the drains of Q3 and Q4 forming a first bridge circuit, and the sources of Q3 and Q4 are connected to ground.

Further, the anode of the backflow prevention diode 10 is connected to the second power supply voltage E02 (24 V), and the cathodes of the backflow prevention diode 10 are connected to the FETs Q5 and Q5.
6 are connected. In addition, FET Q5, Q
6 are connected to Q3, Q3 forming a first bridge circuit.
4, Q3 and Q4 are shared with the second bridge circuit. The FETs Q1 and Q1
Motor 5 between the source of Q5 and the drain of Q3 and the source of Q2 and the source of Q6 and the drain of Q4.
Is connected.

Further, the motor driving means 3 includes the control means 2
The voltage of the motor voltage VM to be supplied to the motor 5 by driving each pair of the two pairs of FETs with the motor control signal V0 consisting of the switch on / off signal and the PWM signal provided from Set the value and direction. The direction of the motor voltage VM is determined according to the polarity of the motor control signal V0 output from the control means 2.

For example, the electric motor 5 is connected to the first power supply voltage E01.
In order to drive the first bridge circuit supplying (12 V) to rotate forward, an FET (field effect transistor) Q constituting a switching element of the motor driving means 3
The gate G1 of 1 has an on signal VON, the gate G2 of Q2 has an off signal VOF, the gate G3 of Q3 has an off signal VOF, the gate G4 of Q4 has a PWM signal VPWM, the gate G5 of Q5 has an off signal VOF, and the gate G6 of Q6 has a gate G6. An OFF signal VOF is supplied, Q1 is set to ON, Q2, Q5, Q6 and Q3 are set to OFF, Q4 is set to ON / OFF determined by the duty cycle of the PWM signal VPWM, and the motor current IM is set to the first level. The electric power flows through a path of power supply voltage E01 (12 V) → Q1 → motor 5 → Q4 → ground (ground), and the motor 5 rotates forward.

The motor 5 is connected to the second power supply voltage E02 (2
In order to drive the second bridge circuit for supplying 4 V) to rotate forward, the ON signals VON and Q6 of the gate (G5) of the FET (field effect transistor) Q5 constituting the switching element of the motor driving means 3 are connected. The off signal VOF is supplied to the gate G6, the off signal VOF is supplied to the gate G3 of Q3, the PWM signal VPWM is supplied to the gate G4 of Q4, the off signal VOF is supplied to the gate G1 of Q1, the off signal VOF is supplied to the gate G2 of Q2, and the Q5 is turned on. Settings, Q6, Q1, Q2 and Q3
Is set to off, and Q4 is set to on / off determined by the duty cycle of the PWM signal VPWM.
M is the first power supply voltage E02 (24V) → Q5 → motor 5 →
Q4 → ground (ground) flows, and the motor 5 rotates forward.

On the other hand, the motor 5 is connected to the first power supply voltage E01 (1
In order to drive the first bridge circuit that supplies 2V) to rotate in the reverse direction, the ON signals VON and Q1 are supplied to the gate G2 of the FET (field effect transistor) Q2 constituting the switching element of the motor driving means 3. The off signal VON is supplied to the gate G1, the off signal VOF is supplied to the gate G4 of Q4, the PWM signal VPWM is supplied to the gate G3 of Q3, the off signal VOF is supplied to the gate G5 of Q5, and the off signal VOF is supplied to the gate G6 of Q6. Settings, Q1, Q5, Q6 and Q4
Is set to off, Q3 is set to on / off determined by the duty cycle of the PWM signal VPWM, and the motor current I
M is the first power supply voltage E01 (12V) → Q2 → motor 5 →
The electric motor 5 flows in the path of Q3 → ground (ground), and rotates in the reverse direction.

Further, the electric motor 5 is connected to the second power supply voltage E02.
In order to drive the second bridge circuit supplying (24 V) to rotate in the reverse direction, an FET (field effect transistor) Q constituting a switching element of the motor driving means 3
6, the ON signal VON to the gate G6, the OFF signal VOF to the gate G5 of Q5, the OFF signal VOF to the gate G4 of Q4, the PWM signal VPWM to the gate G3 of Q3, the OFF signal VOF to the gate G1 of Q1, and the gate G2 of Q2. An OFF signal VOF is supplied, Q6 is set to ON, Q5, Q1, Q2 and Q4 are set to OFF, Q3 is set to ON / OFF determined by the duty cycle of the PWM signal VPWM, and the motor current IM is set to the second. The electric motor E5 (24 V) → Q6 → motor 5 → Q3 → ground (ground) flows, and the motor 5 rotates in the reverse direction.

The first power supply voltage E01 of the motor driving means 3
The diode 9 connected between (12V) and the second bridge circuit has a diode (not shown) formed between the source and the drain of Q1 and Q2 with the anode and the drain formed in the direction of the cathode. Even when Q2 is off, a reverse current flows from the second power supply voltage E02 (24V), and connection is made to prevent the inflow of current from the second power supply voltage E02 (24V).

Further, a diode 10 connected between the second power supply voltage E02 (24 V) and the second bridge circuit
Since the source of the diode (not shown) is formed between the source and drain of Q5 and Q6 in the direction of the anode and the drain in the direction of the cathode, the voltage of the second power supply voltage E02 (24 V) drops even when Q5 and Q6 are off. Then, when the voltage becomes lower than the first power supply voltage E01 (12V), a reverse current flows from the first power supply voltage E01 (12V), and the inflow of current from the first power supply voltage E01 (12V) is prevented. To connect.

The motor current detecting means 4 is constituted by a differential amplifier comprising an operational amplifier and a current detecting resistor, and detects the motor current IM flowing through a current detecting element (for example, a resistor) connected in series with the motor 5. The voltage drop is differentially amplified, and a motor current signal IM0 corresponding to the amplified output is fed back (negative feedback) to the control means 2 to form a feedback path of a steering control system.

FIG. 3 is a block diagram of a main part of the switching control means according to the present invention. In FIG. 3, the switching control means 28
Is composed of an A / D converter, an operational amplifier, a memory, an arithmetic unit and the like, and includes a power supply voltage detecting unit 35, a duty ratio coefficient generating unit 36, a switching unit 40, and multipliers 37 and 38.

The power supply voltage detecting means 35 is composed of an A / D converter, a comparator, a memory such as a ROM, etc., and supplies the first power supply voltage E01 (12V) supplied to the two bridge circuits of the motor driving means 3 and the second power supply voltage. Each power supply voltage is detected based on the second power supply voltage E02 (24 V), the detected voltage value is converted into a digital voltage, and the first power supply voltage E01 (12 V) is detected.
V) and the second power supply voltage E02 (24 V), the detection voltage signal Vd of the power supply used for driving the electric motor is supplied to the duty ratio coefficient generation means 36.

The power supply voltage detecting means 35 is a comparator for converting the second power supply voltage E02 (24 V) to the first power supply voltage E01.
(12V) is compared. At this time, the second power supply voltage E02 (24 V) is changed to the first power supply voltage E01 (1
In the steady state higher than 2 V), the falling signal Hn is supplied to the switching means 40 at H level. Also, the second power supply voltage E
When the current load of 02 (24 V) increases and the voltage becomes lower than the first power supply voltage E01 (12 V), the falling signal Hn is supplied to the switching means 40 at L level.

The duty ratio coefficient generating means 36 is composed of a memory and an arithmetic circuit,
Coefficients for the power supply from 0 V to 25 V are stored, and when the detection voltage signal Vd from the power supply voltage detection means 35 is input, the coefficient becomes 1 at 12 V, and is inversely proportional to the voltage such that the coefficient becomes 0.5 at 24 V. Generate a coefficient signal Kd;
Output to the multipliers 37 and 38, respectively.

FIG. 4 shows the generation coefficient signal Kd and the detected voltage signal V
It is a graph showing the relationship with d. In FIG. 4, when the generation coefficient signal Kd is set on the vertical axis and the detection voltage signal Vd is set on the horizontal axis, the generation coefficient signal Kd becomes 1 when the detection voltage signal Vd is 12V, and becomes 1 when the detection voltage signal Vd is 24V. The generation coefficient signal Kd becomes 0.5, and in the case of the detection voltage signal Vd in the meantime, the generation coefficient signal Kd having an inversely proportional value is output.

The switching means 40 has a switch function of software control, and based on the H level switching signal Hn from the power supply voltage detecting means 35, the motor control signal V0 (ON signal, OFF signal and PWM
(The mixed signal of the signals) is switched to the control signal V02 and supplied to the second bridge circuit. The power supply voltage detecting means 3
The motor control signal V0 (mixed signal of the ON signal, the OFF signal and the PWM signal) input from the drive control means 7 is switched to the control signal V01 based on the L-level switching signal Hn from the first bridge 5 and the first bridge. Supply to the circuit. That is, when the second power supply voltage E02 (24V) is in a steady state higher than the first power supply voltage E01 (12V), the motor control signal V02 is supplied to the motor driving means 3 so as to drive the second bridge circuit. I do.

The multiplier 37 multiplies the output motor control signal V0 by the output coefficient signal Kd from the duty ratio coefficient generator 36 when the switching means 40 is in the state of 1, and outputs the multiplication result to the motor control. It is supplied to the motor driving means 3 as a signal V01. Further, the multiplier 38 includes a switching unit 40.
Is in the state of 2, the output motor control signal V0 is multiplied by the generation coefficient signal Kd from the duty ratio coefficient generation means 36, and the multiplication result is supplied to the motor drive means 3 as the motor control signal V02.

FIG. 5 is a block diagram of a main part of a mode of the switching control means of another embodiment according to the present invention. In FIG. 5, the switching control unit 44 includes a current comparison unit 39, a coefficient generation unit 41,
It comprises a multiplier 42 and switching means 43. The current comparing means 39 outputs the motor current signal I from the motor current detecting means 4.
When M0 is input, based on a predetermined value set in advance,
For example, when the motor current signal IM0 larger than the predetermined value is detected, the comparison signal Hm is supplied at the H level to the switching means 43, and the motor control signal V02 is transmitted to the motor driving means 3 so as to drive the second bridge circuit. Supply.

When the current comparing means 39 detects the motor current signal IM0 smaller than the predetermined value, it supplies the comparison signal Hm at L level to the switching means 43, The motor control signal V01 is supplied to the motor driving means 3 so as to drive the circuit. The predetermined value is set to a value corresponding to a motor current value flowing when the first bridge circuit is driven at, for example, 90% duty.

When the comparison signal Hm from the current comparison means 39 is supplied at L level, the switching means 43
Becomes 1 and supplies the motor control signal V0 as it is to the motor driving means 3 as the motor control signal V01.
When the comparison signal Hm from the current comparison unit 39 is supplied at the H level, the switching unit 43 switches to the state 2 and supplies the motor control signal V0 to the multiplier 42.

The coefficient generating means 41 is constituted by a memory such as a ROM or a RAM, and outputs a constant, for example, 0.5 from the memory and supplies it to the multiplier 42. The multiplier 42
When the switching means 43 is switched to the state 2 by the H level of the comparison signal Hm from the current comparing means 39, the output of the state 2 or the coefficient generation means 4 is added to the motor control signal V0.
Multiplying by a coefficient signal Hq from 1 (for example, a constant 0.5);
It is supplied to the motor drive means 3 as a motor control signal V02.

The multiplier 42 multiplies the motor control signal V0 (mixed signal of the ON signal, the OFF signal and the PWM signal) and a constant. In this case, the PWM signal is used without changing the ON signal and the OFF signal. Multiply only by VPWM
Is changing the duty.

FIG. 6 shows a characteristic diagram of the motor control signal V0 supplied to the first bridge circuit or the second bridge circuit. FIG. 6A is a characteristic diagram of the motor control signal VPWM supplied to the first bridge circuit, and FIG. 6B is a characteristic diagram of the motor control signal VPWM supplied to the second bridge circuit. . FIG. 6 shows that the first power supply voltage is 12 V,
A characteristic diagram when the second power supply voltage is 24 V is shown. As shown in FIG. 6, the duty ratio of the motor control signal VPWM supplied to the first bridge circuit is twice as high as that of the motor control signal VPWM supplied to the second bridge circuit. When the second power supply voltage is 24 V, the duty becomes half of the duty when the first power supply voltage is 12 V in inverse proportion to the voltage.

As described above, when the second power supply voltage drops below a predetermined value during use of the second bridge circuit, the motor drive device 1 can switch to driving of the first bridge circuit. Can be switched to the driving of the second bridge circuit or the driving of the first bridge circuit depending on the size of.

As a modified embodiment, the switching means 40, 4
3 can be switched every duty cycle to control the first and second bridge circuits to be driven every duty cycle.

[0064]

As described above, the motor driving means of the motor driving device according to the present invention comprises: a first bridge circuit connected between a first power supply and ground (ground);
A second bridge circuit connected between a second power supply and ground (ground), and a motor driven by the bridge circuit, wherein the first bridge circuit is connected to ground (ground). The FET is used in common with the FET on the ground side of the second bridge circuit and drives the motor based on a control signal from the control means, so that the two bridge circuits can be switched and used under the control of the common bridge circuit. .

Further, the control means according to the present invention comprises switching control means for switching to driving the first bridge circuit when the voltage value of the second power supply falls below a predetermined value during driving of the second bridge circuit. Therefore, when the voltage drop of the second power supply is large, the power supply can be switched, and optimum power can always be supplied.

Further, the control means according to the present invention has the switching control means for switching between driving of the second bridge circuit or driving of the first bridge circuit according to the driving current value detected by the motor current detecting means, so that the efficiency is improved. And good thrust can be obtained.

Further, the switching control means according to the present invention includes the duty ratio coefficient generating means for generating a coefficient signal inversely proportional to the voltage value detected by the power supply voltage detecting means. The combined PWM control can be performed.

Further, in the motor driving means according to the present invention, a diode for preventing backflow is inserted between the first power supply and the first bridge circuit and between the second power supply and the second bridge circuit. The backflow of the current to the other power supply during use of the power supply can be prevented, and the reliability of the device is improved.

Therefore, it is possible to provide a motor drive device which can obtain a large thrust, is efficient, and has excellent reliability.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of an embodiment in which an electric motor driving device according to the present invention is applied to an electric power steering device.

FIG. 2 is a block diagram of a main part of an embodiment of an electric motor driving device of the electric power steering device according to the present invention.

FIG. 3 is a block diagram of a main part of a switching control unit according to the present invention.

FIG. 4 is a graph showing a relationship between a generation coefficient signal Kd and a detection voltage signal Vd.

FIG. 5 is a block diagram of a main part of a switching control unit according to the present invention.

FIG. 6 is a characteristic diagram of a motor control signal Vo supplied to a first bridge circuit or a second bridge circuit according to the present invention.

FIG. 7 is a block diagram of a conventional motor driving device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Motor drive device, 2 ... Control means, 3 ... Motor drive means, 4 ... Motor current detection means, 5 ... Electric motor, 6 ... Target current signal setting means, 7 ... Drive control means, 8, 28, 44 ...
Switching control means, 9, 10,...
Deviation calculation means, 35 ... power supply voltage detection means, 36 ... duty ratio coefficient generation means, 37, 38, 42 ... multipliers, 39
... current comparing means, 40, 43 ... switching means, 41 ... coefficient generating means.

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3D032 CC21 CC49 DA15 DA23 DA64 DA65 DC01 DC02 DC03 DC33 DC34 DD02 DD10 DD17 EA01 EB11 EC23 EC25 GG01 3D033 CA03 CA13 CA16 CA20 CA21

Claims (5)

[Claims] 1. A motor drive device comprising: a control unit for controlling a motor; and a motor drive unit for driving the motor, wherein the motor drive unit includes a first power supply and a ground (ground).
And a second bridge circuit connected between a second power supply and ground (ground), and a motor driven by the bridge circuit, The two FETs whose first bridge circuit is connected to ground (ground) are shared with the ground-side FET of the second bridge circuit, and drive the motor based on a control signal of the control means. Motor drive device. 2. A power supply voltage detecting means for detecting a voltage value of the first power supply and a voltage value of the second power supply, wherein the control means controls the power supply of the second power supply during driving of the second bridge circuit. 2. The motor drive device according to claim 1, further comprising a switching control unit that switches to driving the first bridge circuit when a voltage value becomes equal to or less than a predetermined value. 3. A motor current detection means for detecting a drive current value of the motor, wherein the control means drives the second bridge circuit or the first bridge circuit based on the drive current value detected by the motor current detection means. 2. The motor driving device according to claim 1, further comprising a switching control unit that switches to driving of the bridge circuit. 4. The motor driving device according to claim 2, wherein said switching control means includes a duty coefficient generating means for generating a coefficient signal inversely proportional to the voltage value detected by said power supply voltage detecting means. 5. The motor driving unit according to claim 1, wherein a backflow preventing diode is inserted between the first power supply and the first bridge circuit and between the second power supply and the second bridge circuit. The electric motor drive device according to claim 1, wherein: