A new gate-driver scheme for synchronous rectifiers in auxiliary output magamp regulation circuits

Magnetic amplifier is a simple and high efficiency post regulator in auxiliary output of the multiple output power supplies. The Schottky diodes must be replaced by synchronous rectifiers (SRs) in low voltage output converters to improve the efficiency. In this paper, a new gate-driver scheme is proposed to maximize the efficiency of the synchronous rectifiers combined with magnetic amplifier post regulating. The forward converters with active clamp were chosen for the application. The new gate-driver scheme optimizes MOSFET turn-on and turn-off delays in synchronous rectifiers by measuring the current that pass through the magnetic amplifier. The additional current transformer detects the current and tries to prevent SRs body-diode conduction and continuously adjusts dead-time delays to minimize the conduction time interval. The operation principle will be explained first. The design guidelines and consideration are given following. A prototype of the proposed converter has been built and the experimental results are also presented.