JPH1052083A - Control circuit for drive of multiphase motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a motor from being rotated almost with no load in three- phase motor drive circuit. SOLUTION: A power device FET is provided in each phase of a motor M on the high side and on the low side. These power devices are controlled by a high-side pre-driver circuit 2 and a low-side pre-driver circuit 3, respectively. Transistors Q5, Q6, Q7 that are turned on/off according to the input of drive signals are added to the high-side pre-driver 2. A supply voltage for the high-side pre-driver obtained by adding the output of a 12-V regulator 5 to the voltage of a battery BT, is applied to the gate of the power device FET 1 through series-connected resistors R1, R2 by turning on the transistor Q7. Current flowing to the signal line through Zener diodes ZD2, ZD3 for gate breakdown voltage protection through the other power devices that are turned on according to position signals, and a motor, is reduced by means of the resistors R1, R3 to a value equal to or below the motor current at no load. Motor rotation is thereby prevented.

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 polyphase motor such as an AC motor, a brushless motor and an induction motor.

[0002]

2. Description of the Related Art When driving and controlling a multi-phase motor having three phases in a motor such as an AC motor, a brushless motor, or an induction motor, it is general to provide three semiconductor switch elements each for a high side and a low side. . In addition, when a power MOS-FET is used, there is an advantage that an element having a low resistance at the time of ON can be obtained. Therefore, an N-ch product may be selected on both sides. An example is disclosed in JP-A-5-328792. In this drive control circuit, the position of the rotor is detected by a Hall element, and based on this detection signal, the logic operation unit turns on / off the corresponding FET via each output buffer to drive the motor. Generally, a withstand voltage protection element is provided between the gate and the source.

[0003]

FE in the above circuit
In the case of T, 1 corresponding to the output signal of the Hall element
One is turned on, but the intermediate transistor that controls the last transistor of the driving output buffer of the FET in the off state is turned on. Therefore, when the current is
The motor flows slowly from the ET through the motor, through the withstand voltage protection element provided in the drive output buffer of the FET in the OFF state, and through the intermediate transistor of the output buffer. The problem of rotation occurs.

[0004]

SUMMARY OF THE INVENTION In order to solve such a problem and to prevent the rotation of the motor at substantially no load in the multi-phase motor drive circuit, the present invention provides a multi-phase motor drive circuit. A power element provided for each phase for driving a drive current for each phase of the motor; and a pre-driver circuit provided for each phase for selectively turning on / off the power element. And a sneak current suppression for suppressing a current sneaking through another power element and the motor to an on / off signal line corresponding to the power element of the pre-driver circuit to a no-load current of the motor or less. For use.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to specific examples shown in the accompanying drawings.

FIG. 1 is a diagram showing a main part of a drive control circuit for a three-phase motor to which the present invention is applied. FIG. 1 shows a three-phase motor M as an example of a polyphase motor to be controlled by the present invention.
Total of 6 arranged on the power side and the ground side for each phase
Power elements FET1, FET2, FET3, FET
Power element drive circuit 1 composed of 4 • FET5 • FET6
And a high-side pre-driver circuit 2 for controlling the power elements FET1, FET3, and FET5 on the high side of the power element drive circuit 1, and a low-side for controlling the power elements FET2, FET4, and FET6 on the low side of the power element drive circuit 1. A pre-driver circuit 3 and a charge pump circuit 4 for controlling and supplying a power supply voltage of the high-side pre-driver circuit 2 are provided.

The pre-drivers 2 and 3 have the same structure for each phase, and one of the pre-drivers 2 and 3 is shown in FIG. Although a 24 V battery is used as the battery BT as a power supply, a 12 V regulator 5 is provided for supplying each power supply voltage of the charge pump circuit 4 and the low-side pre-driver circuit 3.

The charge pump circuit 4 includes a clock circuit 4
The clock circuit 4a outputs a high level (Hi) and a low level (Lo) at a predetermined cycle (for example, 10 kHz). The charge pump circuit 4 has four transistors Q1, Q2, Q
3.Q4 is provided, and H of the clock circuit 4a is provided.
At the i output, the transistor Q1 turns on and the transistor Q3 turns on, and the transistor Q2 turns on and the transistor Q4 turns off. At the Lo output, the transistor Q1 turns off and the transistor Q3 turns off, and the transistor Q2 turns off. The transistor Q4 turns on.

The transistor Q3 is connected to the power supply line (24 V) of the battery BT,
2 is connected to the output (12V) line of the 12V regulator 5. Between the output line of the 12V regulator 5 and the transistor Q4, a capacitor C1 is charged when the transistor Q3 is turned off and the transistor Q4 is turned on, and discharged when the transistor Q1, Q2, Q3 is turned on and the transistor Q4 is turned off. Is connected. The positive side of the capacitor C1 is connected to diodes D1 and D1 connected in series to the output line of the 12V regulator 5.
2 is connected to a node between them. Therefore, the discharge voltage of the capacitor C1 is equal to the voltage of the battery BT (24
V) and is supplied to the high-side pre-driver circuit 2 as a power supply voltage.

The high-side pre-driver circuit 2 is turned on / off by input of a drive signal based on a position signal from a position sensor (for example, a Hall IC) (not shown) provided in the motor M, forward / reverse rotation, regenerative command, and torque command. A transistor Q5 is provided. A transistor Q6 that turns on when the transistor Q5 turns off and turns off when the transistor Q5 turns on is provided, and a transistor Q7 that turns off / on when the transistor Q6 turns on / off is provided. Further, when the transistor Q7 is turned on, the power supply voltage for the high side pre-driver, which is obtained by adding the output (12V) of the 12V regulator 5 to the voltage (24V) of the battery BT, becomes the resistor R1 as a sneak current suppressing resistor. And a resistor R2 connected in series to the gate of the corresponding power element FET1.

The resistor R1 is connected to the power supply side (collector) of the transistor Q6 via a diode D1 and a resistor R3 which are connected to the transistor side in the forward direction. The resistor R2 is provided between the resistor R1 and the gate of the power element FET1, and a diode D2 connected in parallel with the resistor R2 and in a direction in which a current flows to the resistor R1 is provided. I have. Here, the resistors R1 and R2 and the diode D2 are for switching control of the power element FET1.

A Zener diode ZD is provided between the drain and the gate of the power element FET1 to prevent surge voltage.
1 and a diode D3, and Zener diodes ZD2 and ZD3 connected in series in opposite directions for gate breakdown voltage protection between the gate and the source of the power element FET1.

Similarly to the above, the low-side pre-driver circuit 3 receives a position signal from the position sensor, a drive signal based on forward / reverse rotation, regenerative command and torque command, and a transistor Q which is turned on / off by the input signal.
8 are provided. Further, a transistor Q9 similar to the transistor Q6 is provided, and a transistor Q10 similar to the transistor Q7 is provided. A diode D1 similar to the diode D1 is used.
4 is provided, and a resistor R4 similar to the resistor R1 is connected to the resistor R2.
And a resistor R5 and a diode D similar to the diode D2.
5 are provided.

The low-side pre-driver circuit 3
The drain of the power element FET2 driven and controlled by
Zener diode Z between gates for surge voltage suppression
D4 and diode D6 are provided, and FE
A Zener diode ZD5 is provided between the gate and the source of T2 for gate withstand voltage protection.

In this circuit configured as described above, the high-side pre-driver circuit 2 has a power supply voltage of 1 to the voltage (24 V) of the battery BT as described above.
A high-side pre-driver power supply voltage obtained by adding the output (12 V) of the 2 V regulator 5 is supplied.
When a high-level drive signal is input, the transistor Q5 is turned on, the transistor Q6 is turned off, and the transistor Q7 is turned on.
T1 turns on. When the drive signal goes low, the transistor Q5 turns off, the transistor Q6 turns on, and the transistor Q7 turns off, turning off the power element FET1.

The low-side pre-driver 3 operates in the same manner as described above when a drive signal is input. However, the low-side pre-driver 3 is controlled by taking the logic with the PWM signal.

The rotation of the motor during the 0% duty control in the low-side PWM control, which is a conventional problem, is described. For example, since a commutation pattern due to a position signal input is generated in the high-side power element, When the element FET3 is on, the current becomes
3 through the motor M and the zener diodes ZD2 and ZD3 to pass through the transistor Q6 in the ON state. If a current flows through this line, the motor M will rotate at substantially no load regardless of the duty 0% control.

On the other hand, in the circuit according to the present invention, the resistors R1 and R3 are provided in
By optimizing the value of 1 · R3, the no-load current of the motor M is prevented from flowing through the line. Specifically, from the maximum voltage of the battery BT, the power element FET
1 (FET3, FET5), the Zener diode ZD3, the forward voltage of the Zener diode ZD3, the forward voltage of each of the diodes D2, D1, and the voltage obtained by subtracting the sum of the ON voltages of the transistor Q5 from the sum of the resistors R1 and R3. The values of the resistors R1 and R3 are set such that the current value obtained by the division is smaller than the no-load current of the motor M.

The PWM control on the low side causes a problem of switching loss if the gate resistance is increased. However, the high side is driven by a commutation pattern corresponding to the number of revolutions. If heat generation and insufficient gate voltage are not a problem,
The value of the resistor R1 may be increased to eliminate the resistor R3. Also, in this specific example, a three-phase motor has been described.
The present invention is not limited to a three-phase motor, but an event occurs in a two-phase motor, and the present invention can be applied to a multi-phase motor equal to or more than a two-phase motor.

[0020]

As described above, according to the present invention, the duty of 0% when the PWM control is performed in the control of the polyphase motor is performed.
In the control, even if the current sneaks into the signal line for the corresponding power element of the pre-driver through the other power elements and the motor which are turned on in response to the position signal, the sneak current is applied to the no-load current of the motor. With a simple circuit configuration provided with a sneak current suppressing resistor for suppressing the following, it is possible to prevent the motor from rotating at substantially no load.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part of a drive control circuit for a three-phase motor according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power element drive circuit 2 High side pre-driver circuit 3 Low side pre-driver circuit 4 Charge pump circuit 4a Clock circuit 5 12V regulator

Claims (1)

[Claims] 1. A power element provided for each phase of a multi-phase motor to supply a drive current to each phase, and a power element provided for each phase to selectively turn on / off each power element. A pre-driver circuit, and a current flowing around the on / off signal line for the corresponding power element of the pre-driver circuit via another power element and the motor is set to be equal to or less than a no-load current of the motor. A drive control circuit for a polyphase motor, comprising a sneak current suppressing resistor for suppressing the sneak current.