Results in a too small LED current range. The suggested Z-diode can be better used to create a suitable low operating voltage for LED. To reduce the current drawn from 200V to the minimum (= LED current), a high voltage transistor can be used with the auxilary regulator.R11 should be connected directly to the +200V ouput.
can you design every rating for my control circuit?FvM said:
Initially, I design IF=3mA and Ic=2.5mA then using 1K for phototransistor
Obviously, the typical Ic bias point should be shifted to a considerable lower value. Or use an optocoupler with tighter tolerances.Determine the respective minimum and maximum LED current according to the optocoupler CTR
would it be better if I use PC817 that min CTR=80%FvM said:I don't see a clear criterion to define TL431 operating voltage, however R3 modfies the regulator gain. I think that it can work, as you proposed. R4 must have at least a 2W rating. To be able to shut down the PWM in idle operation in case of minimum 20 % CTR, R6 must be dimensioned above 2.5k, very important.
Yes. But it can work with 4N25 as well, using approriate dimensioning.[/quote]would it be better if I use PC817 that min CTR=80%
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