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Hi,
I would like to implement an unusual synchronous rectification control for a specialized resonant converter. When the positive to negative zero crossing of the drain-source voltage (Vds) or current (Ids) of the SR MOSFET is detected (will likely be detected by an external comparator), the SR MOSFET should be turned on for a given amount of time ignoring the negative to positive zero crossing of Vds or Ids. This on time will be generated inside the DSP based on an internal reference or feedback from output.
For my specialized converter to work, I need to allow some reverse current to flow. I want to control this by controlling the total on time of the SR MOSFET. The duty cycle of the SR MOSFET need to be able to reach 100% (resulting in a complete short) for at least a couple of (primary side) switching cycles. There is only one SR MOSFET to be controlled in my converter.
I have limited experience with DSP. Any suggestions on how this can be done reliably?
Thanks
Here are some simplified waveforms showing how I expect the SR MOSFET to be driven. Forward or reverse voltage drop of SR MOSFET is not included in my figure, which I understand may be necessary for sensing.
On time of the SR MOSFET (t_on) needs to be programmable (t_on command would be generated inside the DSP). Duty cycle (t_on/T) need to be able to reach 100%.
