A novel hysteretic controller for a bi-directional dc-dc converter with ZVS and interleaving for dual voltage systems in automobiles is presented. A variable frequency extended band hysteretic current control method is proposed. In comparison with classical fixed frequency current control PWM, the reverse polarity peak current needed for ZVS operation is kept constant Inductor current ripple decreases with load reduction. Automatic changes in operation between buck and boost modes are accomplished without transient currents. Converter simulations are carried out using Matlab/Simulink platform.