Isolation type accurate zero-crossing detection circuit

Abstract

The invention provides an isolation type accurate zero-crossing detection circuit. The circuit comprises a waveform positive and negative detection circuit, an isolation circuit and a signal generation circuit; an alternating current signal of an alternating current detection source is transmitted into the waveform positive and negative detection circuit, and the waveform positive and negative detection circuit controls the isolation circuit and transmits a waveform positive and negative cycle signal to the signal generation circuit. The zero-crossing detection circuit has the advantage that zero-crossing detection of an alternating current source is achieved, large detection errors existing in normal zero-crossing detection are avoided, and isolation of the circuits is realized by utilizing an optocoupler.

Description

technical field [0001] The invention relates to the field of electronic technology, in particular to a zero-crossing detection circuit. Background technique [0002] Zero-crossing detection refers to the detection made by the system when the waveform passes through the zero position when the waveform changes from the positive half cycle to the negative half cycle in the AC system. Zero-crossing detection can be used as switching circuit or frequency detection. It is widely used in power factor correction of rectifier circuits, synchronous grid connection of isolated grid islands, and synchronization of circuit loads. [0003] However, the existing zero-crossing detection circuit has the following deficiencies: [0004] 1. Ordinary photocoupler zero-crossing detection circuit sends pulses at the zero-crossing point of the AC detection source, which cannot distinguish between positive and negative half cycles, and the zero-crossing pulse width cannot be controlled and adjust...

AI Technical Summary

Problems solved by technology

[0004] 1. Ordinary photocoupler zero-crossing detection circuit sends pulses at the zero-crossing point of the AC detection source, which cannot distinguish between positive and negative half cycles, and the zero-crossing pulse width cannot be controlled and adjusted

[0005] 2. Although the cost of the zero-crossing detection circuit is effectively controlled through the triode, the accuracy of the zero-crossing detection is very low and it is easily interfered by clutter

[0006] 3. Zero-crossing detection is performed by a comparator, which cannot really achieve effective electrical isolation, and is susceptible to interference

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