JP2001346390A - Drive controller for motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the efficiency of boosting operation, and to curtail power consumption too by performing required boosting in a booster circuit. SOLUTION: The booster circuit 25 boosts a supply voltage Bv from a battery using a pulse train signal supplied from a microcomputer 23, and supplies the boosted voltage to a motor driving circuit 24, and the rotation of an electric motor 14 is controlled. Being converted by an analog-to-digital converter 26, the supply voltage Bv is put into the microcomputer 23, and the microcomputer 23 lowers the frequency of the pulse train signal to be supplied to the booster circuit 25 according to the increase of the supply voltage Bv. Consequently, always-approximately-constant voltage boosted by the booster circuit 25 is supplied to the driving circuit 24, even when the supply voltage Bv varies.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor drive control device for controlling the drive of a motor.

[0002]

2. Description of the Related Art Conventionally, for example, Japanese Unexamined Patent Application Publication No.
As disclosed in Japanese Patent Laid-Open Publication No. 6-206, a power supply voltage from a battery is determined in advance in a motor drive circuit that controls a current flowing through a motor for applying an assist force to a steering wheel operation of the vehicle and rotates the motor. 2. Description of the Related Art There is known a motor drive control device which is provided with a booster circuit for boosting and supplying a boosted voltage by a predetermined ratio.

[0003]

In the above conventional device, the boosting ratio of the boosting circuit must be determined on the assumption that the voltage from the battery decreases, and the boosting ratio is large to some extent. there were. Therefore, when the power supply voltage from the battery rises, the voltage supplied to the motor drive circuit may become too high, and the boosted power supply is used so that a voltage higher than necessary is not applied to the motor drive circuit. A voltage protection circuit such as a zener diode for lowering the voltage has been provided. However, lowering the boosted power supply voltage wastes the boosting operation and eventually wastes the power consumption of the entire motor drive control device.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to address the above problems, and has as its object to improve the efficiency of the boosting operation by performing appropriate boosting as needed. An object of the present invention is to provide a motor drive control device that saves power consumption of the entire device.

In order to achieve the above object, the present invention comprises a motor drive circuit for controlling a current flowing through a motor to rotate the motor, and a booster circuit for boosting a power supply voltage and supplying the boosted voltage to the motor drive circuit. And a step-up control means for controlling an operation state of the step-up circuit in accordance with the magnitude of the power supply voltage to adjust a voltage supplied to the motor drive circuit. in this case,
Various voltages that directly or indirectly represent the power supply voltage can be used as the power supply voltage used to control the operation state of the booster circuit. Further, the step-up control means includes:
For example, when the power supply voltage increases, the boosting circuit may be controlled so as to reduce the boosting ratio of the power supply voltage.

In the present invention configured as described above,
The boost control means controls the operating state of the boost circuit according to the magnitude of the power supply voltage to adjust the voltage supplied to the motor drive circuit, so that even when the power supply voltage fluctuates, the motor drive circuit includes: A substantially constant voltage boosted by the booster circuit is supplied as it is. Therefore,
According to the present invention, the above-described conventional voltage protection circuit is not required, and unnecessary boosting operation is not required, and power consumption of the entire motor drive control device can be saved.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 schematically shows an example in which a motor drive control device according to the present invention is applied to an electric power steering device of a vehicle. Is shown.

In this electric power steering apparatus, the turning operation of the steering handle 11 is performed by the rack and pinion mechanism 1.
Steering shaft 1 transmitting to left and right front wheels FW1 and FW2 via
3 is provided with the electric motor 14 assembled. The electric motor 14 is constituted by a DC motor, and provides an assisting force to the turning operation of the steering handle 11 in accordance with its rotation. The rotation is transmitted to the steering shaft 13 via the speed reduction mechanism 15. It has become so.

The electric motor 14 is controlled by an electric control device 20. The electric control device 20
The vehicle includes a steering torque sensor 21, a vehicle speed sensor 22, a microcomputer 23, a motor drive circuit 24, a booster circuit 25, and an analog / digital converter (A / D converter) 26.

The steering torque sensor 21 is mounted on the steering shaft 13 and rotates with the steering shaft 1 as the steering wheel 11 rotates.
The steering torque (torsion) TM generated in the motor 3 is detected, and a detection signal representing the torque TM is supplied to the microcomputer 23. The vehicle speed sensor 22 detects the vehicle speed V and supplies a detection signal indicating the vehicle speed V to the microcomputer 23.

The microcomputer 23 is connected to a battery 27 through an ignition switch IG. The microcomputer 23 responds to a power supply voltage Bm supplied from the battery 27 when the switch IG is turned on, and every predetermined short time in FIG. , And the steering control program (not shown) is started to be repeatedly executed. The boost operation of the boost circuit 25 is controlled by executing the program of FIG. Further, by executing the steering control program (not shown), the electric motor 1 according to the steering torque TM and the vehicle speed V detected by the steering torque sensor 21 and the vehicle speed sensor 22, respectively.
4 is controlled. Battery 27
The battery 27 is driven by the engine of the vehicle.
Is also connected.

A power supply voltage Bv from a battery 27 is supplied to the motor drive circuit 24 and the booster circuit 25 via a fuse HU. As shown in detail in FIG. 2, the motor drive circuit 24 includes a bridge circuit having four sides of field effect transistors (FETs) 31 to 34 as switching elements. A power supply voltage Bv from the battery 27 is supplied to each drain of the FETs 31 and 32.
The sources of the FETs 33 and 34 are grounded. FET
The sources of the FETs 31 and 32 are connected to the drains of the FETs 33 and 34, respectively, and the electric motor 14 is connected between the sources of the FETs 31 and 32.

Drive circuits 35 and 36 are connected to the gates of the FETs 31 and 32, respectively. The drive circuits 35 and 36 are configured by FETs that are turned on / off by the microcomputer 23 and a switching control circuit that receives the boosted voltage Bu from the booster circuit 25 and includes transistors and resistors that are controlled by the FETs. The boosted voltage Bu is intermittently supplied to each of the gates of the FETs 31 and 32 in synchronization with the on / off control.
32 is turned on and off.

Drive circuits 37 and 38 are connected to the gates of the FETs 33 and 33, respectively. The drive circuits 37 and 38 are configured by an FET that is turned on and off by the microcomputer 23, and a switching control circuit that receives a power supply voltage Bv from the battery 27 and includes a transistor and a resistor that are controlled by the FET. By intermittently supplying the power supply voltage Bv to each gate of the FETs 33 and 34 in synchronization with the on / off control,
34 is turned on and off.

The booster circuit 25 has first and second capacitors C1 and C2. One end of the first capacitor C1 is supplied with a power supply voltage Bv from the battery 27 via a diode Di1, and the other end of the capacitor C1 is
It is connected to the connection point between the emitter of the PN transistor Tr1 and the emitter of the PNP transistor Tr2. The collector of the transistor Tr1 is supplied with the power supply voltage Bv from the battery 27 via the diode Di3, and the collector of the transistor Tr2 is grounded. A switching circuit including resistors r1 to r3 and a transistor Tr3 is connected to each base of the transistors Tr1 and Tr2.
The switching circuit turns on the transistor Tr1 and turns off the transistor Tr2 when the pulse train signal from the microcomputer 23 is at a low level, and turns off the transistor Tr1 when the pulse train signal is at a high level.
Is turned off and the transistor Tr2 is turned on. Second
One end of the capacitor C2 is connected to the first terminal via a diode Di2.
The capacitor C1 is connected to one end of the capacitor C2, and the other end of the capacitor C2 is grounded.

The A / D converter 26 converts the power supply voltage Bv from the battery 27 from analog to digital (A / D) and supplies it to the microcomputer 23.

Next, the operation of the embodiment configured as described above will be described. When the power supply voltage Bm is supplied from the battery 27 to the microcomputer 23 by turning on the ignition switch IG, the microcomputer 23
Starts to repeatedly execute the boost control program and the steering control program (not shown) in FIG. 3 every predetermined short time.

The execution of the boost control program is started at step 100 in FIG. 3, and at step 102, a signal representing the power supply voltage Bv from the battery 27 is converted to an A / D converter 26.
Enter from.

Next, at step 104, the cycle Tp corresponding to the power supply voltage Bv is determined by referring to the power supply voltage-period table. This power supply voltage-period table is stored in advance in the microcomputer 23, and as shown in FIG. 4, the period Tp increases as the power supply voltage Bv increases. After the processing in step 104, in step 106, the count value of the timer provided in the microcomputer 23 and continuously counting the elapsed time is equal to one half (Tp / 2) of the determined cycle Tp. ) It is determined whether or not it is above. If the count value is less than Tp / 2,
In step 106, “NO” is determined, and in step 11
At 8, the execution of the boost control program is terminated.

On the other hand, if the count value becomes equal to or more than the Tp / 2, it is determined "YES" in step 106, and the count value by the timer is reset to "0" in step 108. Next, at step 110, it is determined whether or not the current pulse level data PLEV is "1". If the current pulse level data PLEV is "1", step 110
Is determined to be "YES" in step 112, and the pulse level data PLEV is changed to "0" in step 112. If the current pulse level data PLEV is "0", "NO" is determined in step 110, and the pulse level data PLEV is changed to "1" in step 112. And step 11
In step 6, the level of the pulse train signal output from the microcomputer 23 to the booster circuit 25 is converted to pulse level data.
The level is changed from the low level to the high level or from the high level to the low level in accordance with PLEV, and in step 118, the execution of the boost control program is terminated. The changed level of the pulse train signal is maintained in the changed state until the process of step 116 is performed next.

When a time corresponding to Tp / 2 elapses from the change of the level of the pulse train signal, step 10
6. "YES" again, that is, when the count value is
It is determined that it is not less than p / 2, and steps 110 to 116 are performed.
The level of the pulse train signal output from the microcomputer 23 to the booster circuit 25 is changed from the high level to the low level or from the low level to the high level. By the operation of such a boost control program,
The booster circuit 25 is supplied with a pulse train signal that repeats a low level and a high level in a cycle that increases as the power supply voltage Bv increases. That is, a pulse train signal having a frequency that decreases as the power supply voltage Bv increases is supplied to the booster circuit 25.

In the booster circuit 25, as shown in FIG. 5A, when the pulse train signal output from the microcomputer 23 is at a high level, the transistor Tr2 is turned on, the transistor Tr1 is turned off, and the first capacitor is turned on. The other end of C1 (transistor Tr1, Tr2 side terminal) is at the ground potential. Thereby, the first capacitor C1 is
It is charged up to the power supply voltage Bv from the battery 27 via the diode Di1. Next, the microcomputer 23
Is low, the transistor Tr1 turns on and the transistor Tr2 turns off, and the other end of the first capacitor C1 becomes the power supply voltage Bv. As a result, the potential of one end of the first capacitor C1 (terminals on the diodes Di1 and Di2 side) becomes a voltage 2 · Bv that is twice the power supply voltage Bv, and the electric charge charged in the first capacitor C1 causes the second capacitor C2 Is charged. However, the time during which the transistors Tr1 and Tr2 are turned on and off is sufficiently longer than the time required to charge the first and second capacitors C1 and C2.

The transistors Tr1 and Tr2 are turned on / off by the pulse train signal from the microcomputer 23.
The voltage Bu at one end (diode Di2 side terminal) of the second capacitor C2 is reduced to a voltage 2.multidot.Bv that is twice the power supply voltage Bv, except for the consumption of the electric charge charged in the second capacitor C2 described later by the off control. To rise. Specifically, voltage 2 · B
The voltage rises to a voltage lower than v by the voltage drop of the diodes Di1 and Di2.

On the other hand, the microcomputer 23 executes a steering control program (not shown) to execute a steering torque TM detected by the steering torque sensor 21 and a vehicle speed sensor 22.
Drive circuits 35 to 38 based on the detected vehicle speed V
On / off control. In this case, the microcomputer 23 supplies a pulse train signal to the drive circuits 35 and 38 if the steering handle 11 is turned to the right and the electric motor 15 needs an assist torque in the same direction. As a result, the FETs 31 and 34 are controlled to be turned on and off, and the current based on the power supply voltage Bv from the battery 27 flows to the ground via the FET 31, the electric motor 14 and the FET 34, and the electric motor 14 rotates forward to rotate the steering wheel 1
1 acts to rotate rightward. Conversely, if the steering wheel 11 is turned to the left and the electric motor 15 needs assist torque in the same direction, the microcomputer 23 supplies a pulse train signal to the drive circuits 36 and 37. As a result, the FETs 32 and 33 are turned on and off, and the power supply voltage Bv
Current by the FET 32, the electric motor 14 and the FET 3
3, and the electric motor 14 acts to rotate the steering handle 11 to the left by rotating in the reverse direction.

In supplying the pulse train signal, the duty ratio of the pulse train signal is set to increase as the detected steering torque TM increases, and the duty ratio of the pulse train signal is set to decrease as the detected vehicle speed V increases. . Thus, when a large steering force is required by the driver, a large assist torque is obtained by the electric motor 14, and the driver can turn the steering handle 11 lightly. When the vehicle is running at high speed, the assist torque is controlled so as not to become too large, and careless turning operation of the steering wheel 11 is avoided, and the running stability of the vehicle is improved.

In the on / off operation of the FETs 31 and 32 by the drive circuits 35 and 36 as described above, a voltage Bu obtained by boosting the power supply voltage Bv from the battery 27 by the booster circuit 25 is supplied to the FETs 31 and 32. The drive circuits 37 and 38 turn on / off the FETs 33 and 34.
In the OFF operation, the power supply voltage Bv
Is supplied to the FETs 31 and 32. In this case, FET3
If high-side type FET elements are used as 1 and 32, the FETs 31 and 32 can be used without necessarily using the booster circuit 25.
It is also possible to ensure the on / off operation of 32. However, since the high-side type FET element has a large chip area and a high cost and a large on-resistance, all of the FETs 31 to 34 have a low-side type FE.
Generally, it is configured by a T element. Thus, FE
When a low-side type FET element is used as T31, T32, since the power supply voltage Bv is supplied from the battery 27 to the drain, even if the power supply voltage Bv is applied to the gate, the FETs 31, 32 are turned on. Operation cannot be maintained. Therefore, in this case, the power supply voltage Bv from the battery 27 is inevitably increased to
It is necessary to supply a higher voltage to the gates of the FETs 31 and 32 than the gate-source voltage of the FET.

In the on / off control of the FETs 31 to 34, the power supply voltage Bv from the battery 27 may decrease. Particularly, in a vehicle, the power supply voltage Bv decreases when the engine is started. Because
The booster circuit 25 needs to boost the power supply voltage Bv at a relatively large boost ratio. On the other hand, when the amount of charge stored in the second capacitor C2 in the booster circuit 25 is small and the amount of power generated by the generator 28 is sufficient, if the boost ratio is fixed, the booster circuit 25 There is a possibility that the voltage supplied to the drive circuits 35 and 36 from the power supply becomes excessively high.

However, if such a situation is expected in the present embodiment, the pulse period Tp is set to a large value by the processing of step 104 described above. As a result, the change cycle of the pulse level data PLEV in the processing of steps 106 to 114 is long, that is, as shown in FIG. 5B, the pulse train signal supplied from the microcomputer 23 to the base of the transistor Tr3 of the booster circuit 25. The cycle becomes longer. Therefore, as compared with the consumption of the charge stored in the second capacitor C2, the charging frequency of the second capacitor C2 by the charge charged in the first capacitor C1 is reduced, and one end of the second capacitor C2 (the diode Di2
Voltage Bu at the side terminal) is a voltage 2 · B that is twice the power supply voltage Bv.
v (more precisely, the diodes Di1, Di
(Voltage lower by 2 voltage drops).
That is, the boosting ratio of the boosting circuit 25 becomes a value smaller than “2”.

As can be understood from the above description, according to this embodiment, the power supply voltage Bv
The boosting ratio of the boosting circuit 25 is controlled in accordance with the magnitude of the power supply voltage Bv so that the voltage supplied from the boosting circuit 25 to the motor drive circuit 24 does not increase.
Is varied, the motor drive circuit 24 is always supplied with a substantially constant voltage boosted by the booster circuit 25 as it is. Therefore, according to the above-described embodiment, the voltage protection circuit is not required, and unnecessary boosting operation is not required, and power consumption of the entire device can be saved.

In the above embodiment, by changing the frequency of the pulse train signal supplied from the microcomputer 23 to the booster circuit 25, the boosting ratio of the booster circuit 25 is changed and controlled. However, the method of changing and controlling the boosting ratio is not limited to this, and a method shown in the following first or second modification may be adopted.

A first modification is the microcomputer 23
The duty ratio of the pulse train signal to be supplied to the booster circuit 25 is changed and controlled according to the magnitude of the power supply voltage. In this case, the microcomputer 23 is configured as shown in FIG.
Instead, the boost control program shown in FIG. 6 is repeatedly executed every predetermined short time. Other parts are the same as in the above embodiment.

The first modified example will be specifically described. The step-up control program shown in FIG.
Starting at 20, the signal representing the power supply voltage Bv from the battery 27 is input from the A / D converter 26 at step 122 as in the case of the above embodiment. Then, in step 124, the duty ratio RT corresponding to the power supply voltage Bv is determined by referring to the power supply voltage-duty ratio table. The power supply voltage-duty ratio table is stored in advance in the microcomputer 23, and as shown in FIG. 7, the duty ratio RT increases as the power supply voltage Bv increases.

After the processing in step 124, step 1
At 26, it is determined whether or not the current pulse level data PLEV is "1", similarly to the process of step 110 of the above embodiment. If the current pulse level data PLEV is "0", "YES" is determined in step 126, and the program proceeds to step 128 and subsequent steps. Step 128
In the above, the count value of the timer is changed from "1" to the predetermined duty ratio RT in a predetermined cycle Tpo.
(1-RT) · Tpo
It is determined whether or not this is the case. If the count value is less than the calculated value (1−RT) · Tpo, “NO” is determined in the step 128, and the execution of the boost control program is ended in the step 142. The count value is the above value
If (1−RT) · Tpo or more, “YES” is determined in step 128, and steps 130, 132, and 140 are determined.
In steps 108, 114, and 116 of the above embodiment,
Resets the count value of the timer to "0", changes the current pulse level data PLEV to "1", and lowers the level of the pulse train signal output from the microcomputer 23 to the booster circuit 25. Change from level to high level.

The current pulse level data PLEV is "
If “1”, it is determined “NO” in step 126 and the program proceeds to step 134 and subsequent steps. In step 134, the count value of the timer is set to the value R obtained by multiplying the predetermined cycle Tpo by the duty ratio RT.
It is determined whether or not it is T · Tpo or more. If the count value is less than the calculated value RT · Tpo, step 134
Is determined to be "NO" at step 142, and the execution of the boost control program is terminated at step 142. If the count value is equal to or greater than the value RT · Tpo, at step 134, “YE
S ”, and in steps 136, 138 and 140,
Similarly to the processing of steps 108, 112, and 116 in the above embodiment, the count value of the timer is reset to "0", the current pulse level data PLEV is changed to "0", and the microcomputer 23 sends the boosting circuit 25 Is changed from the high level to the low level.

By the processing of steps 126 to 140, a pulse train signal as shown in FIG.
Supplied to Therefore, also in this case, the booster circuit 2
When the pulse train signal output to 5 is at a high level, the first capacitor C1 is charged, and when the pulse train signal is at a low level, the second capacitor C2 is charged. However, in this case, if the period (1-RT) · Tpo during which the pulse train signal is at the low level is shortened, the second capacitor C2
Is not charged, that is, the charging voltage of the second capacitor C2 is equal to twice the power supply voltage Bv.
The capacitances of the first and second capacitors C1 and C2 and the frequency of the pulse train signal are determined so as not to increase to Bv.

In the first modification, the duty ratio RT is set so as to increase as the power supply voltage Bv increases in the process of step 124. Therefore, when the power supply voltage Bv becomes high, FIG.
As shown by the broken line, the period (1-RT) · Tpo in which the pulse train signal is at a low level is shortened, and the second capacitor C2
Is lower than the voltage 2 · Bv which is twice the power supply voltage Bv.

As can be understood from the above description,
Also in the first modification, the boosting ratio by the boosting circuit 25 is controlled by the boosting control program by the microcomputer 23 in accordance with the magnitude of the power supply voltage Bv from the battery 27, and the boosting circuit 25 supplies the motor to the motor drive circuit 24. Voltage does not increase. Therefore, this first
In the modified example, the same effect as in the above embodiment is expected.

In the second modified example, when the power supply voltage Bv from the battery 27 increases, the generation of the pulse train signal supplied from the microcomputer 23 to the booster circuit 25 is interrupted. In this case, the microcomputer 23 repeatedly executes the boost control program shown in FIG. 9 every predetermined short time instead of the above-mentioned FIG. Other parts are the same as in the above embodiment.

The second modified example will be specifically described. The step-up control program shown in FIG.
Starting at 50, a signal representing the power supply voltage Bv from the battery 27 is input from the A / D converter 26 at step 152 as in the case of the above embodiment. Then, in step 154, it is determined whether or not the power supply voltage Bv is equal to or higher than a predetermined value Bvo. If the power supply voltage Bv is less than the predetermined value Bvo, “NO” is determined in the step 154, and the program proceeds to the step 156 and subsequent steps. Step 15
The processing in steps 6 to 162, 166, and 168 is almost the same as the processing in steps 106 to 116 in the above embodiment. The difference is that the value Tp / 2 that changes in accordance with the power supply voltage Bv is used in the determination processing of step 106 in the case of the above embodiment, whereas in the case of the second modification, step 156 is used. Is that the fixed value Bvo is used in the determination processing of. Therefore, the cycle (frequency) of the pulse train signal output from the microcomputer 23 to the booster circuit 25 is constant.

On the other hand, when the power supply voltage Bv is a predetermined value B
If it is equal to or greater than vo, "YES" is determined in step 154, and the program proceeds to step 164. In step 164, the count value of the timer is reset. Then, in step 166, the pulse level data PLEV is set to "1", and in step 168, the level of the pulse train signal output from the microcomputer 23 to the booster circuit 25 is set to a high level corresponding to the pulse level data PLEV. . Thus, as shown in FIG. 10, as long as the power supply voltage Bv is equal to or higher than the predetermined value Bvo, the pulse train signal is maintained at the high level. In this state, the second capacitor C2 of the booster circuit 25
Since the charging operation is not performed, the booster circuit 25 supplies the motor drive circuit 24 with the value 2 · B twice the predetermined value Bvo.
The boost voltage Bu larger than vo is not applied. As a result, also in the second modification, the boosting ratio by the boosting circuit 25 is limited by the boosting control program by the microcomputer 23 in accordance with the magnitude of the power supply voltage Bv from the battery 27, so that the power supply voltage Bv varies. In this case, the voltage protection circuit becomes unnecessary and
Useless step-up operation is not required, and power consumption of the entire device can be saved.

In the above embodiment and its modifications, the power supply voltage Bv supplied from the battery 27 to the motor drive circuit 24 and the booster circuit 25 via the fuse HU is used.
Thus, the boost voltage Bu supplied from the boost circuit 25 to the motor drive circuit 24, that is, the boost ratio by the boost circuit 25 is controlled. However, instead of this, the boosted voltage Bu that changes in relation to the power supply voltage Bv is fed back, and the boosted voltage Bu supplied from the booster circuit 25 to the motor drive circuit 24, that is, the boosted voltage Bu, The boost ratio by the circuit 25 may be controlled. In this case, the boosted voltage Bu is set to A / D
In addition to inputting the voltage to the converter 26 and using the boosted voltage Bu in place of the power supply voltage Bv supplied from the battery 27 to the booster circuit 25 in each of the programs of the above-described embodiments and modified examples, The power supply voltage-period table and the power supply voltage-duty ratio table provided in the storage unit 23 also use a boosted voltage-period table and a boosted voltage-duty ratio table that store a period and a duty ratio that increase as the boosted voltage Bu increases. To

The boost voltage Bu supplied from the boost circuit 25 to the motor drive circuit 24, that is, the boost ratio by the boost circuit 25 may be controlled by the power supply voltage Bv and the boost voltage Bu. In this case, an added voltage Bvu (= Bv + Bu) obtained by adding the power supply voltage Bv and the boosted voltage Bu,
The larger voltage of the power supply voltage Bv and the boosted voltage Bu or the like may be used instead of the power supply voltage Bv, similarly to the case where the power supply voltage Bv is replaced with the boosted voltage Bu.

Further, if the voltage such as the terminal voltage of the battery 27 or the terminal voltage of the generator 28 is directly or indirectly related to the power supply voltage Bv supplied from the battery 27 to the booster circuit 25, the voltage of other circuit positions Voltage is also available. Also,
A value obtained by estimating the power supply voltage Bv from these voltages may be used.

Further, in the above-described embodiment and its modified example, the example in which the present invention is applied to the electric power steering device of the vehicle has been described. However, the present invention can also be applied to a drive control device for a motor that drives and controls an electric motor for other uses mounted on a vehicle. Also,
The present invention is not limited to vehicles, but may be applied to various motor drive control devices that drive and control an electric motor using a fluctuating power supply voltage.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram of an electric power steering device according to an embodiment of the present invention.

FIG. 2 is an electric circuit diagram showing a booster circuit and a motor drive circuit of FIG. 1 in detail.

FIG. 3 is a flowchart of a boost control program executed by the microcomputer of FIGS. 1 and 2;

FIG. 4 is a graph showing a relationship between a power supply voltage and a pulse period.

FIGS. 5A and 5B are waveform diagrams of a pulse train signal supplied from a microcomputer to a booster circuit.

FIG. 6 is a flowchart of a boost control program executed by a microcomputer according to a first modification of the embodiment.

FIG. 7 is a graph showing a relationship between a power supply voltage and a duty ratio.

FIG. 8 is a waveform diagram of a pulse train signal supplied from a microcomputer to a booster circuit according to the first modification.

FIG. 9 is a flowchart of a boost control program executed by a microcomputer according to a second modification of the embodiment.

FIG. 10 is a waveform diagram of a pulse train signal supplied from a microcomputer to a booster circuit according to the second modification.

[Explanation of symbols]

FW1, FW2: left and right front wheels, 11: steering wheel, 14
... Electric motor, 20 ... Electrical control device, 21 ... Steering torque sensor, 22 ... Vehicle speed sensor, 23 ... Microcomputer, 24 ... Motor drive circuit, 25 ... Boost circuit, 26 ... A
/ D converter, 27 ... battery.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B62D 119: 00 B62D 119: 00 F-term (Reference) 3D032 CC49 DA15 DA23 DA65 DD17 EA01 EB11 EC24 3D033 CA03 CA13 CA16 CA20 CA21 CA28 5H571 AA03 BB02 CC02 DD01 EE01 EE02 EE03 FF01 FF02 FF07 FF08 GG02 HA01 HA08 HA09 HA16 HB01 HC02 HD01 HD03 JJ03 JJ16 JJ18 KK05 LL23

Claims (2)

[Claims] 1. A motor drive control device comprising: a motor drive circuit that controls a current flowing through a motor to rotate the motor; and a booster circuit that boosts a power supply voltage and supplies the boosted power supply to the motor drive circuit. A motor drive control device, comprising: boost control means for controlling an operation state of the boost circuit in accordance with the magnitude of the voltage and adjusting a voltage supplied to the motor drive circuit. 2. The motor drive control device according to claim 1, wherein said step-up control means controls said step-up circuit so as to reduce a step-up ratio of said power supply voltage when said power supply voltage rises.