A New Front-End Converter with Extended Hold-Up Time

A new front-end converter has been developed by the authors to make full use of the bulk capacitor energy to extent the hold-up time. The converter operates in the power factor correction (PFC) mode whe the ac line is normal and then switches into the hold-up boost dc-dc converter mode during the hold-up time as soon as the ac line is faulty. The theory of these two operation modes is introduced. The mathematic relationship between the hold-up time and capacitor energy is derived. Though the converter has two operation circuits, only one control circuit is required. Experimental prototype converter shows the hold-up time is extended to 2.5 times as those of conventional PFC circuit at a 220 VAC input, and a 56 VDC, 2.3 kW output. The test results agree well with the theory analysis.