Leakage Inductance Effects of Output Transformer on Current-Resonant Parallel Converter Characteristics

The effects of leakage inductance of the output transformer of a current-resonant parallel converter on the latter's characteristics were studied through simulations and experiments. As a parasitic resonance appears between the leakage inductance and the resonance circuit capacitor during the commutating period of the output rectifying circuit every half-cycle, the larger the leakage inductance and the output current become, the more the capacitor voltage is increased. Consequently the main resonance after the parastic resonance every half-cycle between the resonance reactor and the resonance capacitor is enlarged. Thus both the output voltage at large output currents and the maximum output power of the converter are increased. The controllability of the output voltage through the switching frequency is also improved. The maximum output power is increased by about 20% by making the leakage inductance equal to the inductance of the resonance circuit reactor for a 50 kHz-15 W class converter.