A novice asks about the selection of optocouplers for PWM isolation control of MOS tubes

grove_armweak

A novice asks about the selection of optocouplers for PWM isolation control of MOS tubes [Copy link]

As the title says, if the PWM signal frequency is 46.875k, then the period is about 21.333us

Is it feasible to use pc817 optocoupler? The maximum frequency is 80khz and the response time is 18us. How to understand these two parameters?

If not, which model would be better?

grove_armweak

Is the TLP250 okay?

grove_armweak

tlp521 ps250

maychang

PC817, TLP521...are all not feasible.

Just look at these optocoupler datasheets and you will know.

maychang

grove_armweak posted on 2019-12-15 19:01 tlp521 ps250

This is part of the TLP521 characterization parameters.

Your PWM period is only 21us, but the typical delay time of TLP521 is 15us, and the shutdown time is 25us.

If you want to use optocoupler isolation to control power MOS tubes, you must use high-speed optocouplers.

grove_armweak

maychang posted on 2019-12-15 19:18 This is part of the TLP521 characteristic parameters. Your PWM cycle is only 21us, but the typical delay time of TLP521 is 15us, and the shutdown time is 25us. ...

Thank you, teacher. So for this application, should I choose a linear optocoupler or a nonlinear optocoupler?

maychang

grove_armweak posted on 2019-12-15 19:38 Thank you, teacher. In this application, should we choose linear optocoupler or nonlinear optocoupler?

"So for this application, should we choose a linear optocoupler or a nonlinear optocoupler?"

Your title says "control MOS tube", so I guess your MOS tube works as a switch. Since MOS tube works as a switch, why use linear optocoupler?

grove_armweak

maychang posted on 2019-12-15 19:44 "So for this application, should we choose linear optocoupler or nonlinear optocoupler?" Your title says "control MOS tube" ...

Thank you teacher