The single-switch forward converter represents a valid alternative to the single-switch flyback topology in isolated, off-line, step-down converters with high output current requiring galvanic isolation in the 100 to 300 W power range. Unlike flyback converters, in a forward converter energy transfers instantly to the transformer and does not rely on it for energy storage. Transformers can thus have higher magnetizing inductance and no air gap, providing better transformer utilization. The transformer’s secondary output is then L-C filtered to ensure lower output voltage ripple while peak current – and thus stress – on the active transistor is reduced.
On the flip side, compared to a flyback topology, the transformer must be reset after a few cycles to avoid saturation. In this case, a higher voltage rating for the primary power MOSFET, an extra output inductor and a freewheeling diode are needed.
We have a complete offer of primary-side PWM and synchronous rectification controllers, power MOSFETs and diodes together with a range of hardware and software evaluation and development tools including reference designs to help developers design high-efficiency, size optimized forward converters.
