MP8030 SSR Optocoupler Bias Resistor

DC-DC Power Converters
1

Hello,
we are currently evaluating the MP8030 for a 70W+ SSR Flyback application with 24V output voltage.
Unfortunatly the application examples do not include SSR Flyback.
I’m not quite sure how to calculate the optocoupler bias resistor (R29 in your datasheet).
Can you please provide some hints?

MP8030_opto_bias
MP8030_opto_bias2293×1214 217 KB

2

Hello @d.zelosko,

The selection of bias resistor depends on the COMP pin current or opto-transistor current, CTR(Current transfer ratio) of the optocoupler, Vout and reference voltage. By calculating the current through the FB pin and opto-diode via CTR, the value of the bias resistor can be determined. Usually, the bias resistor is around 10-50k ohm.

Hope this helps.

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