[zilog]

I want to have a SMPS PSU for my UcD, and to avoid bus pumping effects I want to use synchronous rectification. I mean this in the sense that the rectifier conducts in both directions during the smps switch period and thus can both feed the power rails with voltage as well as shave off the extra voltage caused by bus pumping. The advantage of using this approach in contrary to using passive regulators to control voltage is that excess energy from one rail is transferred magnetically through the transformer to the opposite rail and thus keeps the rail volgtages equal to the transformer winding output voltages during each switching period.

The problem with this approach as what I have heard is that the rectifier transistors will feed the transformer the full amount of energy stored in the bus capacitors when the smps is powered off or if the duty cycle falls to zero, this must be taken provisions against with elaborate control circuitry.

I still dont know if I will take this approach or simply leave some margin for bus pumping, will sure be easier but easy is no fun