Electric power unit operating in continuous and discontinuous conduction modes and control method therefor

摘要

An electronic power unit includes first and second MOS transistors and a digital control circuit. The first MOS transistor applies a voltage to the load. The second MOS transistor remains on while the first MOS transistor remains off and rectifies the current flowing in the load. The digital control circuit turns on the first transistor upon lapse of a first time interval from the time the second MOS transistor is turned off. The digital control circuit turns on the second MOS transistor upon lapse of a second time interval from the time the first MOS transistor is turned off. The digital control circuit controls the on-period of the first MOS transistor so that the voltage applied to the load is constant in a discontinuous conduction mode. The digital control circuit determines, while the voltage applied to the load is constant, an optimal value of the first time from the duty.