Light load analysis and topology morphing between full-/half-bridge DC-to-DC converter

ABSTRACT To retain high efficiency in a wide output voltage range and reduce the conduction and switching losses for a DC power supply, this work makes use of topology morphing between full- and half-bridge converters. The operation of the converter is better as a phase-shift modulated (PSM) full-bridge converter for a high output voltage and as the asymmetrical pulse-width modulated (APWM) half-bridge counterpart for a low output voltage. The light load operations of PSM full-bridge and APWM half-bridge DC converter are analysed in detail to account for the voltage gain variation as well as the switching and conduction losses. A suitable control algorithm is also proposed to facilitate smooth morphing transitions and eliminates the unwanted voltage and current overshoot. A laboratory converter circuit rated at outputs up to 60 V, 1.8 kW with 180 V input voltage is designed and built to verify the operation with topology morphing. The experimental results have demonstrated by adapting the PSM full-bridge DC converter to the APWM half-bridge DC converter at the low voltage range that the circuit efficiency can be effectively improved and enhanced 6% for the best.