Capacitor bootstrap drive circuit and method of switched reluctance motor

Abstract

The invention discloses a capacitor bootstrap drive circuit of a switched reluctance motor, consisting of an upper switching tube drive circuit and a lower switching tube drive circuit. The upper switching tube drive circuit consists of a first charging circuit, a first discharging circuit and a bootstrap capacitance circuit, and the lower switching tube drive circuit consists of a second charging circuit and a second discharging circuit. The invention also discloses a drive method using the drive circuit. By charging a bootstrap capacitor to the drive power supply voltage only when a lower switching tube is turned on and turning on an upper switching tube with the voltage of the bootstrap capacitor, the method avoids the problem that the motor works abnormally since the upper switching tube has a deficient grid voltage due to the voltage raising of a terminal b and is failed to be turned on when a phase winding of the motor is turned on. With the bootstrap drive circuit constituted by a bootstrap capacitor, a diode, a commonly-used resistor, a triode and other elements, the switching tubes can be driven in real time with driving signals. The invention has advantages of simple circuit structure and strong practicability.

Description

technical field [0001] The invention relates to a switched reluctance motor, in particular to a driving circuit and a driving method of the switched reluctance motor. Background technique [0002] Switched reluctance motors have some unique advantages, such as simple structure, firmness, maintenance-free, large torque and low current at start-up and low speed; wide range of high-speed constant power range, good performance, and excellent performance in a wide range of speed and power. High output and high efficiency; it can operate with phase loss and has strong fault tolerance; it can be flexibly controlled and can easily realize four-quadrant operation; it has strong regenerative braking ability, etc. This makes the switched reluctance motor system widely used in household appliances, general industry, servo and speed control systems, traction motors, high-speed motors, aerospace and other fields. A switched reluctance motor is an electromechanical energy conversion devic...

AI Technical Summary

Problems solved by technology

The disadvantage of this circuit is that the structure of the multi-power supply circuit is complex and the circuit cost is high.

The principle of the single power supply drive circuit formed by the bootstrap diode is to design the relative delay circuit of the bootstrap diode and the upper and lower tubes, and use the principle of reverse cut-off of the diode, combined with the delay signal to realize the first opening of the lower switch tube, Then turn on the control sequence of the upper switching tube to avoid the high voltage generated in the motor coil when the upper and lower switching tubes are turned on at the same time, causing the reference voltage of the upper switching tube to be larger than the control power supply voltage, so that the upper switching tube cannot be driven normally

The key point of this circuit is to use the reverse cut-off principle of the diode, but the problem is that it can only realize the opening action of the upper switch tube once. If the motor works in the pulse width modulation (PWM) mode, it needs to be in a commutation cycle. When the upper switch tube is turned on frequently, since the diode is not an energy storage element, it cannot provide the charge for the subsequent turn-on of the upper switch tube, so it cannot work normally and continuously

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