Zero-voltage control circuit for small signals

Abstract

The invention relates to a zero-voltage control circuit for small signals. The circuit comprises a first operational amplifier, a second operational amplifier, a third operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a first transistor, a first exclusive-OR gate, a second exclusive-OR gate, a third exclusive-OR gate, an optical coupler, a first power source and a second power source. The zero-voltage control circuit for the small signals achieves zero-voltage detection on the small signals, detection accuracy is high, various isolation protection means are adopted, and therefore no interference will happen to an external circuit, the signal deviation problem does not exist, and zero-voltage control over data output is achieved well.

Description

technical field [0001] The invention relates to the field of control, in particular to a zero-voltage control circuit for tiny signals. Background technique [0002] Zero voltage control technology is a kind of soft switching technology, which is mainly used to protect MOSFET, electromagnetic relay, thyristor, IGBT and other switching tubes from high voltage impact. [0003] Common zero-voltage control circuits currently using zero-voltage control technology such as figure 1 shown. [0004] The input signal is directly connected to two optocouplers (such as pc817) for zero voltage detection. The defect of this circuit is also obvious. [0005] 1. The requirements for the input signal are high, the voltage must be above 0.7V, and the current is at the mA level; [0006] 2. The accuracy of zero-crossing detection is low. Since the voltage drop of the diode is about 0.7V, the detection signal is offset, so the zero-voltage position detected by the circuit is actually the pos...

AI Technical Summary

Problems solved by technology

[0005] 1. The requirements for the input signal are high, the voltage must be above 0.7V, and the current is at the mA level;

[0006] 2. The accuracy of zero-crossing detection is low. Since the voltage drop of the diode is about 0.7V, the detection signal is offset, so the zero-voltage position detected by the circuit is actually the position of plus or minus 0.7V;

[0007] 3. Zero voltage detection cannot be performed on tiny signals;

[0008] 4. Interference with the original circuit

[0009] Due to the above-mentioned defects in the circuit, it is only suitable for zero-voltage detection of large signals or power supplies

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