Design Improvement of Self-Oscillating Resonant Converters Accounting for Gate Charge in High-Frequency LED Drivers

Increasing the operation frequency of Self-Oscillating Resonant Converters (SORC) is a challenge due to reasons such as higher switching, magnetic component and driving circuit losses, but mainly due to the effects of the parasitic components of the switching devices and their impact on the precision between the operating and designed frequencies of the converters. This paper evaluates, both in SPICE and experimentally, two SORC models and design methodologies at frequencies higher than they were traditionally designed to operate, with the purpose of finding which constraints of such methodologies determine the frequency ceiling, i.e., the maximum achievable self-oscillating frequency of the converter as well as the deviation from the designed frequency when comparing traditional and improved methodologies. An improved design equation which considers the required gate-charge for the gate of the converter switching device is also considered as a condition for a sustained self-oscillation operation in higher frequencies, expanding the methodologies original frequency limitation.