Patent ID: 8421420

Claim:
A battery charger that is connected between a 3-phase alternate current (AC) generator for generating a 3-phase AC power including U-, V-, and W-phases, and a plurality of batteries, said battery charger converting said AC power output from said 3-phase AC generator to a direct current (DC) power so as to supply said DC power to said plurality of batteries, the battery charger comprising: a rectification processor including a rectifier element that independently controls charge to each of said plurality of batteries; a charge state detector that detects a charge state of a battery of said plurality of batteries from a voltage thereof to select said battery for charging in a predetermined period in accordance with said detected charge state; a synchronous signal detector that detects a signal synchronized with each phase of said 3-phase AC power from said 3-phase AC generator to output a synchronous signal; and a charge controller that allows said rectification processor to control said charge in synchronization with said 3-phase AC generator in accordance with said synchronous signal so as to control a charge amount of said battery selected by said charge-state detector, wherein said charge state detector determines said charge state of said battery by comparing said voltage thereof with a predetermined threshold potential, selects said battery for charging in accordance with a predetermined determination reference, based on a combination result of said charge states of said plurality of batteries, and inputs an error signal obtained by comparing said voltage of said selected battery with said predetermined threshold potential reference potential, and a selection signal indicating said selected battery, to said charge controller; said synchronous signal detector outputs a rectangular waves each of which is synchronized with each phase of said 3-phase AC power, and triangular waves each of which is synchronized with each of said rectangular waves and monotonously increases within a half cycle thereof, as said synchronous signal; and said charge controller compares said error signal input from said charge state detector with said triangular wave input from said synchronous signal detector, thereby deems a moment when potentials of said error signal and each of said triangular waves match as a trigger for starting conduction of said rectifier element, and inputs a firing signal to said rectification processor in accordance with said selection signal input from said charge state detector.