the circuit of zero cross detection

Published:2011/5/27 8:20:00 Author:Ariel Wang | Keyword: zero cross , detection | From:SeekIC

The AC 220V goes to branch current circuit by resistor . Then the branch voltage goes to photocoupling.Let's suppose we input line-to-neutral voltage A .When line-to-neutral voltage A is converting from negative half period to positive half period. It will generates the pulse on the trailing edge.The pulse goes to ADμC812's INTO pin.That makes the system enter the suspending progress.When the micro system entering the suspending progress,it will give a sampling command. And it will read the value reactive current Iqm.The reactive current is A's reactive current.It will reach the max value through 1/4 cycle.At this time,if you sample the voltage,you will get UM. If UM=1.414U,you can get the virtual value U of the voltage.



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