Improved active clamp for secondary circuits

The paper describes improvements to an active clamp for secondary circuits in isolated converter topologies. The active clamp provides both voltage clamping of the secondary diodes and the recycling of diode reverse recovery energy stored in the leakage inductance of the transformer secondary winding. An isolated winding on the recycling circuit permits variation in the location of the output choke, which is shown to provide a possible 10 dB reduction of common mode noise. Results from a 700 W telecommunications rectifier using a planar transformer are presented