A Self-Oscillated Feedback Network for PushPull Resonant Power Converters

This article proposes a self-oscillated feedback network for push-pull resonant topologies. Resonant topologies such as Class E power amplifiers are suitable for very high frequency (VHF) switching applications as they ideally have no switching losses. However, since VHF gate driving still requires complex and expensive auxiliary circuits, a self-oscillated driving method can be considered. Conventional self-oscillated feedback networks are only applicable to single-ended topologies, which are limited to low-power applications. On the other hand, the proposed self-oscillated feedback network is expandable to push-pull topologies and can significantly increase power handling capability. The proposed circuit maintains complementary symmetry by utilizing the coupled inductor and virtual ground characteristics and satisfies the oscillation criteria for all operating conditions. The proposed circuit is experimentally verified through a 3.3 MHz, 30 W push-pull power oscillator prototype.