Switching signal interface circuit based on double photoelectric isolation

Abstract

The invention relates to the technique of switching signal transmission in power electronic converters, aiming at providing a switching signal interface circuit based on double photoelectric isolation. The interface circuit comprises two photoelectric isolating circuits and an intermediate circuit; the first photoelectric isolating circuit receives a primary side switching signal and outputs a first intermediate switching signal according to the primary side switching signal; the intermediate circuit receives the first intermediate switching signal and outputs a second intermediate switching signal according to the first intermediate switching signal; and the second photoelectric isolating circuit receives the second intermediate switching signal and outputs a secondary side switching signal according to the second intermediate switching signal. The invention is applicable for the signal transmission of the switching signal with reliable electric isolation and interference shielding in the power electronic converters of relatively higher voltage class or relatively higher power class. The relatively long-distance isolation transmission can be achieved by the intermediate circuit, the influence of potential variation between high-voltage and low-voltage circuits on signal transmission is obviously inhibited as the potential of the intermediate circuit is relatively fixed; and one side of a sensitive control circuit can be far from high voltage.

Description

technical field [0001] The invention relates to a switching signal transmission technology in a power electronic converter, in particular to a switching signal interface circuit based on double photoelectric isolation. Background technique [0002] In recent years, power electronic converters have been widely used. The power electronic converter controls the on and off of the semiconductor devices in the power circuit through the weak current switch signal to realize power conversion, and at the same time the state switch signal in the power circuit is fed back to the control circuit. The so-called switch signal is a signal type different from the analog signal, which can be represented by two states of the circuit, such as two states of on and off, and two states of high level and low level. In power electronic circuits, switching signals are often used for drive control of switches such as power semiconductors and feedback of circuit status information. The control circu...

AI Technical Summary

Problems solved by technology

Among them, optical fiber isolation is mainly used in high-voltage and high-power power electronic converters, which can completely cut off the interference of power circuits on control circuits during signal transmission, but the cost of optical fiber isolation is relatively high

The traditional optocoupler isolation method cannot achieve long-distance isolation, and the control circuit and power circuit must be close to each other

In the power circuit, the voltage and current of the power semiconductor device change rapidly during the switching process, resulting in strong electromagnetic interference, which may have a great impact on the nearby weak current control circuit

This is reflected in the following aspects: (1) In high-power power electronic converters, the control circuit and the power circuit are required to have a long enough distance, but the traditional optocoupler isolation method still cannot separate the control circuit from the power circuit at a long distance. (2) There is still direct capacitive coupling between the primary and secondary sides of the optocoupler circuit, which cannot isolate the influence of the power circuit on the control circuit, and the interference signal in the power circuit will pass through the coupling capacitance between the primary and secondary sides of the optocoupler circuit (3) The sensor circuit on the high-voltage side will lead the high-voltage circuit interference signal to the low-voltage side circuit (similarly, the low-voltage side circuit may also interfere with the sensor circuit on the high-voltage side)

Images