Patent ID: 8415931

Claim:
A power supply device, comprising: a permanent-magnet generator including a rotor having a magnet for forming a magnetic field and a stator having a stator winding; a rectifier including a full-wave rectification circuit, for rectifying an AC current generated by the permanent-magnet generator into a DC current, whose low side elements are made of MOSFETs; an electrical load supplied with DC power output from the rectifier; and a control circuit including a load voltage detector for detecting a terminal voltage across the electrical load and an AC voltage detector for detecting an input terminal voltage from the permanent-magnet generator; wherein when the terminal voltage across the electrical load is lower than a predetermined value, if the input terminal voltage from the permanent-magnet generator connected to each MOSFET is positive, the control circuit turns off the each MOSFET, whereas if the input terminal voltage negative, the control circuit turns on the each MOSFET, thereby supplying power to the electrical load (full-wave rectification mode); meanwhile, when the terminal voltage across the electrical load is higher than the predetermined value, the control circuit turns on the MOSFETs, thereby short-circuiting input terminals of the permanent-magnet generator with each other, furthermore, the control circuit includes a power supply unit supplied with power from the permanent-magnet generator for driving the control circuit, and when the power for driving the control circuit is not secured, the power supply unit retains the full-wave rectification mode even if the terminal voltage across the electrical load is higher than the predetermined value.