AC voltage under-voltage detecting circuit

Abstract

The AC undervoltage detecting circuit can fast detect the fast drop in AC voltage and slowly detect the slow drop in AC voltage to ensure the UPS inverter to output AC voltage matching the requirement to the load. The AC undervoltage detecting circuit has bridge rectifier with output connected to both the input of the fast filter and the input of the slow filter, the output of the fast filter and the output of the slow filter connected separately to the input of the fast detection circuit and the slow detection circuit separately, the output of the fast detection circuit and the output of the slow detection circuit connected to the inputs of the or-gate, and D-trigger with input connected to the output of the or-gate and output Q as detection result.

Description

technical field [0001] The invention relates to a detection circuit, more specifically, to an AC voltage detection circuit. Background technique [0002] UPS, uninterruptible power supply, must switch to bypass power supply when the inverter voltage is abnormal to ensure the load's power requirements. The inverter voltage change may drop from the rated value to very low or even zero instantly (such as reducing to zero within 1 / 4 cycle), or it may decrease slowly (such as reducing to 70--80% of the rated value within 5-10 cycles) . For the former change, the load requires the UPS to switch quickly, and for the latter, the load requires the UPS to switch after a certain period of time, so as to eliminate the small change of the inverter voltage caused by the sudden change of the load but does not need to switch. Generally, for the voltage analog detection in an uninterruptible power supply (UPS), the method of step-down-rectification-filtering-t...

AI Technical Summary

Problems solved by technology

It is difficult for the above-mentioned voltage detection circuit to detect the voltage change at the moment of failure, and the switch cannot immediately block the inverter and switch to the bypass power supply, resulting in an unbearable output voltage interruption for the load, resulting in unnecessary losses

At present, there is also a method of using digital signal processing to detect the signal to be detected and the sinusoidal voltage waveform of the template, but this method requires CPU or DSP chip processing, which is costly and complicated.

Or use the CPU or DSP to periodically sample the sampled sine wave, and it can be detected only after several cycles (generally, in order to prevent misoperation, the value of sampling 100ms for about 5 cycles and taking the average value) can be detected, which is far from meeting the requirements of computer load.

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