JP2000287455A - Control of inverter circuit power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a method of controlling an inverter circuit that can acquire a charge pump power supply voltage without providing a power supply voltage monitor circuit. SOLUTION: In a motor control apparatus using a charge pump power supply C in a 3-phase inverter circuit to supply a voltage to a motor coil, a duty ratio of the PWM output waveform is determined by arithmetic process of a triangular wave signal, and the reference value for comparison with such triangular wave signal and an M microcomputer including a program for determining the ON/OFF timings of the upper/lower arms of a switching element of the inverter circuit generates the time to forcibly turn OFF the upper arm to prevent voltage drop of the charge pump power supply C, when the motor rotating speed is low (including the stop condition) and an operation torque is high so that the upper arm of the inverter circuit always becomes ON and thereby the duty ratio of the PWM output waveform does not become 100% even when the command torque rises.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control device using a charge pump power supply for an inverter circuit.

[0002]

2. Description of the Related Art In recent years, a charge pump power supply has been used for an inverter circuit of a motor control device.
As shown in the figure, by using a capacitor that is charged when the upper arm is OFF and the lower arm switching element is ON as the charge pump power supply C, the power supply of the gate drive circuits U, V, W of the upper arm switching elements is used. There is an advantage that the power supply of the drive circuits U, V and W can be reduced by three and the motor control device can be downsized.

[0003]

However, the charge pump power supply C is connected to the OF of the switching element of the lower arm.
If the F time becomes zero or becomes small, the voltage of the charge pump power supply C becomes zero or decreases, and there is a problem that control becomes impossible.

For this reason, the inverter circuit using the conventional charge pump power supply C shown in FIG.
A power supply voltage monitoring circuit A for monitoring the voltage of the power supply is required. When the voltage drops, control is performed to forcibly turn off the upper arm, and there is a problem that control cannot be performed without the power supply voltage monitoring circuit A.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a control method of an inverter circuit which can secure a charge pump power supply voltage without providing a power supply voltage monitoring circuit.

[0006]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention calculates a duty ratio of a PWM output waveform by arithmetically processing a triangular wave signal and a reference value to be compared with the triangular wave signal. A microcomputer equipped with a program for determining the ON / OFF timing of the upper and lower arms. When the motor rotation speed is low (including when the motor is stopped) and high torque operation is performed, the upper arm of the inverter circuit is always ON and the command torque is This is a method of controlling the inverter circuit power supply to prevent the voltage drop of the charge pump power supply by creating a time for forcibly turning off the upper arm so that the duty ratio of the PWM output waveform does not become 100% with the rise of the voltage.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to solve this problem, the present invention relates to a motor control device using a charge pump power supply for a three-phase inverter circuit for supplying a voltage to a motor winding. The reference value to be compared is calculated to determine the duty ratio of the PWM output waveform, and the upper and lower arms of the switching element of the inverter circuit are turned on and off.
A microcomputer equipped with a program to determine the OFF timing. The upper arm of the inverter circuit is always ON when the motor rotation speed is low (including when stopped) and high torque operation is performed.
This is a method of controlling the inverter circuit power supply to make a time for forcibly turning off the upper arm so that the duty ratio of the PWM output waveform does not become 100% as the command torque increases, thereby preventing a voltage drop of the charge pump power supply.

In addition, a program for creating a time for forcibly turning off the upper arm is such that after the charge pump power supply voltage is charged, the rotation speed of the motor is taken into the microcomputer via the receiving circuit from the pulse of the encoder, and is rotated by the microcomputer internal operation. The speed is calculated. If the calculation result is equal to or less than the specified speed, the triangular wave signal and a reference value to be compared with the triangular wave signal are arithmetically processed to reduce the duty ratio of the PWM output waveform to 80%.
100% if the speed is over the specified speed
2. The control method of an inverter circuit power supply according to claim 1, wherein the control calculation of the position and the speed is executed in a limited mode.

In this way, the upper arm of the inverter circuit is always turned on, and the time for forcibly turning off the upper arm is created so that the duty ratio of the PWM output waveform does not become 100% with the increase of the command torque. Voltage drop can be prevented.

Further, the rotational speed of the motor is taken into the microcomputer from the pulse of the encoder via the receiving circuit via the receiving circuit, and the rotational speed is calculated by microcomputer internal calculation. When the calculation result is less than the specified speed, the triangular wave signal and the triangular wave signal The reference value to be compared is calculated and the duty ratio of the PWM output waveform is set to the 80% limit mode, so that a time for forcibly turning off the upper arm can be secured.

[0011]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, C is a charge pump power supply,
U, V, and W are upper-arm gate drive circuits, X, Y, and Z are lower-arm gate drive circuits, RE is an encoder for detecting the speed of the motor, B is a receiving circuit that receives an encoder pulse of the encoder RE, M Is a microcomputer.

The microcomputer M converts a pulse input from the encoder RE through the receiving circuit B into a rotation speed by calculation. The microcomputer M controls the gate drive circuits U, V, W, X, Y, and Z by performing control calculations such as position and speed, and turns on and off the switching elements of the upper arm and the lower arm.
Controls the timing of the FF.

2, 3 and 4, reference numeral 2 denotes a triangular wave signal set inside the microcomputer M, and 1 denotes a reference value which is calculated and increased / decreased according to a change (increase / decrease) in the command torque. 1 and the triangular wave signal 2 are compared and processed to obtain PW
The duty ratio of the M output waveform is determined. Reference numeral 3 denotes the ON / OFF time of the lower arm, and 4 denotes the ON / OFF time of the upper arm. When the triangular wave signal 2 matches the reference value 1, the lower arm 3 is turned ON, and the upper arm 4 is turned ON. It is turned off.

FIG. 2 shows a case in which the motor is operated with a sufficiently low torque. When the upper arm 4 is OFF (T1), the lower arm 3 is turned ON, and the time for supplying the charge pump power supply C is sufficiently secured. I have.

FIG. 3 shows a case where the command torque increases (increases) and the voltage of the charge pump power supply C does not decrease. The OFF (T1) time of the upper arm 4 is longer than that of FIG. Becomes shorter.

FIG. 4 shows a case where the ON time of the lower arm 3 is lost because the command torque is further increased and the charge pump power supply C is charged, and the inverter circuit cannot be controlled continuously.

Here, the duty means the lower arm O / O cycle for one cycle T of ON / OFF of the lower arm shown in FIGS.
When the duty ratio is 80%, the ratio of one cycle T to the time of the 0FF of the lower arm is T: T1 =
1: 0.8.

In addition, the reason why the upper arm and the lower arm are displaced at this time is to prevent the upper and lower arms from being simultaneously turned on and the switching element from being destroyed.

FIG. 5 is a flowchart of a program for creating a time for forcibly turning off the upper arm. First, after the main power is turned on, the time for charging the charge pump power supply C using the counter function inside the microcomputer M is set to an initial counter value. Set as Until the counter value becomes 0, the charge pump power supply C is set in the initial charging mode, and a loop for subtracting 1 from the initial counter value is performed. When the counter value becomes 0, it is regarded that the charge pump power source C is in the initial charging completion mode.

Next, it is possible to receive an external command in the control start mode. At this time, the process ends when the main power is turned off.
Is received by the receiving circuit B, the rotation speed is calculated by the microcomputer M, and the position, speed and torque are controlled and calculated. The rotation speed of the control calculation result is compared with a specified value inside the microcomputer M. If the rotation speed is lower than the specified value, the PW of the inverter circuit
A mode in which the duty of M is limited. If the speed is faster than a specified value, the mode is unlimited. In both modes, control is performed until the pulse of the encoder RE is received. Is repeated to prevent a voltage drop of the charge pump power supply C which is an inverter circuit power supply.

In the present embodiment, the initial counter value is set to 15, the control is shifted to the control start mode after a lapse of 12.5 ms, and the specified value of the rotation speed is set to 1000 rpm.
Below 00 rpm, the duty ratio is limited to 80% to prevent a drop in the charge pump power supply voltage. The specified value of the rotation speed is set to 1000 rpm and the duty ratio is set to 80%. However, the present invention is not limited to these values.

[0023]

As is apparent from the above embodiment, according to the present invention, it is possible to prevent the charge pump power supply voltage from lowering even without a charge pump power supply voltage monitoring circuit, and to reduce the speed at low speeds and high torques. This also enables continuous inverter circuit control. Further, the size of the inverter circuit can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a charge pump power supply circuit in an inverter circuit of the present invention.

FIG. 2 is a PWM duty waveform diagram (for a low torque command).

FIG. 3 is a PWM duty waveform diagram (a boundary where the charge pump voltage does not decrease).

FIG. 4 is a PWM duty waveform diagram (charge pump voltage is zero)

FIG. 5 is a flowchart of a program according to the present invention.

FIG. 6 is a diagram showing a charge pump power supply circuit in a conventional inverter circuit.

[Explanation of symbols]

 1 Reference value 2 Triangular wave signal B Receiving circuit C Charge pump power supply M Microcomputer RE Encoder T1 Upper arm OFF time

Continuing from the front page (72) Inventor Kenichi Suzuki 1006 Kazuma Kadoma, Kazuma, Osaka Prefecture F-term in Matsushita Electric Industrial Co., Ltd. (Reference) 5H007 AA06 BB06 CA01 CB05 DB02 DB03 DB09 DB12 EA13 FA02 5H576 DD02 DD04 EE11 HB01

Claims (2)

[Claims] In a motor control device using a charge pump power supply for a three-phase inverter circuit for supplying a voltage to a motor winding, a triangular wave signal and a reference value to be compared with the triangular wave signal are processed to calculate a PWM output waveform. A microcomputer having a program for determining a duty ratio and for determining ON / OFF timings of upper and lower arms of a switching element of the inverter circuit. When the motor rotation speed is low (including when the motor is stopped) and high torque operation is performed, the inverter circuit is used. Inverter power supply to prevent the voltage drop of the charge pump power supply by making time to forcibly turn off the upper arm so that the duty ratio of the PWM output waveform does not become 100% with the increase of the command torque as the upper arm is always ON. Control method. 2. A program for creating a time for forcibly turning off the upper arm is configured such that after the charge pump power supply voltage is charged, the rotation speed of the motor is taken into the microcomputer via the receiving circuit from the pulse of the encoder and rotated by the microcomputer internal operation. Calculate the speed, and if the calculation result is below the specified speed,
The triangular wave signal and a reference value to be compared with the triangular wave signal are arithmetically processed to set the duty ratio of the PWM output waveform to the 80% limit mode. 2. The method according to claim 1, wherein the operation is performed.