Design of a dual half bridge DC-DC converter for an ultra-capacitor based auxiliary power source in electric vehicles

This paper proposed a dual half bridge (DHB) DC-DC converter used for ultra-capacitor power management in electric vehicles. Different from conventional DHB converters, a PWM plus phase shift (PPS) control strategy is introduced here due to the variable voltage operation mandates of an ultra-capacitor. This novel combination will be discussed from following two aspects in this paper. In the theory level, a minute operation principle analysis of this PPS based DHB converter is presented, and so is the principle of ZVS. In the industry implementation level, firstly an optimal rated phase shift angle selection strategy is introduced to reduce conduction losses and device current ratings. Then, to extend the ZVS range, the method to decide input DC inductance is proposed. Finally, an adjustment rules for dead band time is also discussed to avoid negative effect of dead band and a detailed mechanism of a re-resonance phenomenon in dead band transient is analyzed. A 9-21V/240W hardware prototype is built up to prove validity of this work.