I am trying to make the above circuit, which will operate at around Vac = 230V. The two MOSFETS are 12NM50's. I am not married to the idea of using these MOSFETS and can order different ones if they will better suite the application. I would like to drive the gates of the MOSFETS from a TC4427 MOSFET driver, which will be powered using a 7.5W 15VDC power supply, which will supply 15VDC to the VDD pin of the driver. The signal to the driver will be from the PWM output signal (of 3.3V) at 98kHz from a microcontroller. Simple question: where do I connect the DC ground to this AC circuit, so that I can have a good reference for the gate signal, so that the FETS will operate properly? I expect that the DC ground from the driver circuit should be connected at the ground point between CY1 and CY2; but I'm not sure. I feel that if If I connect the DC ground to the neutral wire of the AC circuit - the whole thing will blow up. I also cant afford to blow circuit components up as I have a limited amount of resources. I'm hoping that you guys might be able to help me prevent these catastrophic failures.
Also, should I drive the gates directly from the output of the MOSFET driver, or should there be some resistors inline? I'm following the typical installation diagram of the TC4427 datasheet and so a 1nF pull-down capacitor will be attached the output of the driver.
I should probably mention that this is my first project using MOSFETS; so any input and advice will be greatly appreciated.
One final question; should I run the output of the microcontroller through an opto-coupler to isolate the microcontroller from the driver/AC circuit? Just trying to be cautious, and I'm terrified of high voltage and MOSFETS.
Thank you all!
288.3 KB Views: 10