I am trying to generate 500 kHz sine wave of varying amplitude using full bridge transformer isolated DC/AC converter.
I decided to use a sine wave table to change the PWM duty cycle. More the values per cycle better the sine wave output. For 256 values per half sine wave, we need to update once every 3.9 ns which means MCU needs to run at 256 MHz rate at least.
Another constraint is that Mosfet driver needs to turn on/off the Mosfet really fast under 3.9 ns. Mosfet driver tc427 need at least 30 ns to turn on/off the MOSFET.
I am really confused on how to go about overcoming the constraints. Any suggestions please?
Best Answer
From a simple two stage LC filter you could get a response like this with just a basic square wave input at 500 kHz and no PWM and no sine look-up table: -
If you had some minimal attempt at PWM (changing duty every quarter of a cycle or 500 ns) you would get an even cleaner output and/or require less filtering. But you have to define load impedances across the whole range for this to be successful. At the moment I have tailored it to a 4000 ohm load but if you require loads down at 1000 ohm or less then the filters change.