Unequal PWM control for a current-fed dc-dc converter for battery application

An unequal pulse-width modulation (PWM) is proposed for the current-fed dual-active bridge (DAB) bidirectional DC-DC converter for battery charging/discharging applications when the battery voltage is wide. The difference of the effective duty cycles between the two sides is constant in spite of the battery voltage and the transferred power. With the proposed control, zero-voltage switching (ZVS) can be achieved for all switches within wide load range with low circulation loss. The converter with the proposed control has lower current ripples, circulation loss and peak current. The typical working mode is given. The system parameter optimal design including the fixed time delta and dead time is illustrated taking account into the magnetizing current of the high frequency transformer. The effectiveness of the proposed control is verified by the experimental results of a 1kW prototype.