Relay protection circuit based on high-precision zero-cross detection

Abstract

The invention discloses a relay protection circuit based on high-precision zero-cross detection, which comprises a rectification circuit, a signal generation circuit, a filter circuit, a shaping circuit and a processor which are electrically connected in sequence, and is characterized in that the rectification circuit is used for converting alternating current into positive waveform voltage; the signal generation circuit comprises a first diode, a first capacitor, a ninth resistor, a first transistor and an optocoupler, and the on-off of the optocoupler is realized by controlling the on-off of the first transistor; the processor is connected with at least one relay and is used for receiving the output signal and recording the action times of the relay, receiving the first output signal when the optocoupler is switched off, receiving the second output signal when the optocoupler is switched on, and judging an alternating current zero point when detecting that the second output signal is changed into the first output signal; the relay is controlled to be switched on and off at an alternating current zero point. The device can realize accurate on-off of the relay at an alternating current zero point, can simultaneously control a plurality of relays to act, and is long in service life, high in precision, small in size, low in cost, stable and reliable.

Description

technical field [0001] The invention belongs to the technical field of relay protection, in particular to a relay protection circuit based on high-precision zero-crossing detection. Background technique [0002] With the continuous improvement of the level of industrialization, the number of intelligent household appliances is increasing, and it is more and more inseparable from the control of relays. For example, for a long time, the heating system of kitchen appliances has often used relays to control the heating components, but because the kitchen appliances are powered by the mains, the relay contacts are often damaged due to ignition and arcing, which makes the relay invalid and the product cannot be used, which seriously affects Reliability and service life of kitchen appliances. [0003] Most of the current relays are by adding a zero-crossing detection circuit. By detecting the zero-crossing point, the relay is turned on at the zero-crossing point to avoid the rela...

AI Technical Summary

Problems solved by technology

However, the existing zero-crossing detection circuit has the following defects: First, the product circuit structure is simple, such as directly connecting a resistor and an optocoupler in series on the mains, because the range of the current transfer ratio (CTR) of the optocoupler is relatively large, and the optocoupler will increase when the voltage rises. The rate of conduction and cut-off in the process of voltage drop will be different, so that the signal received by the processor has a large error range, resulting in inaccurate detection; second, the output of the optocoupler is usually directly connected to the processor through a resistor. The change signal (such as falling edge) received by the processor will have a relatively large inclination angle, which will easily cause the processor to misjudge

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