Hello Team,
I would like to check with you what is the distinct difference between active clamp forward converter and self resonant forward converter?
Both use the same technique to reset the magnetizing transformer inductance, for example using the capacitor from SW node to ground (add 1 more P-CH fet for active clamp in series with the resonant cap).
It would be helpful if you could kindly provide me the pros,cons and also some explanation on them.
Thanks a lot!
Best Regards,
Ernest Yong
Hi Ernest,
There are definite similarities between active clamp (ACF) and self-resonant forward (SRF) converters but you also highlighted one of the major differences. The ACF topology requires two MOSFETs while the SRF uses only a single, ground referenced MOSFET. This difference also has implications on the controller that can be used: the ACF requires a specific, dual output D, 1-D PWM controller such as UCC2897A, while the SRF can use any single output, general purpose controller such as UCC28C44. There are many more controller options for SRF compared to ACF.
For some applications SRF is better compared to RCD or third winding forward reset techniques. SRF can resonate the drain-source as high as 2xVIN, so it is not well suited for off-line applications due the high voltage stress on the MOSFET VDS but it does recycle the rest energy and at least transfer a portion to the secondary side - third winding and RCD rest are both dissipative and incur higher losses in the clamp. SRF is also a hard switched topology compared to ACF which offers fixed frequency ZVS.
I've summarized below some of the key pros/cons comparing the four major forward converter rest techniques:
Regards,
Steve
