Battery-charging device

A battery-charging device that charges a battery by using a rectified output of a magnet-type AC generator, comprising

• a full-bridge rectifier circuit which comprises a bridge circuit having upper arms and lower arms, each of the upper and lower arms constituting the bridge circuit being composed of a MOSFET, and the rectifier circuit further comprising input terminals to which an output of the generator is inputted, and the rectifier circuit further comprising a positive-side output terminal and a negative-side output terminal connected respectively to a positive terminal and a negative terminal of the battery,
• a battery voltage detection circuit that detects a voltage between the positive terminal and the negative terminal of the battery,
• an input potential polarity detection circuit that detects a polarity of a potential of each input terminal of the rectifier circuit, and
• a FET control unit that controls the MOSFETs of the rectifier circuit in accordance with an output of the battery voltage detection circuit and an output of the input potential polarity detection circuit;
• wherein
• the FET control unit is provided with a charging necessity determination means that determines whether the battery needs to be charged or battery charging needs to be paused based on the voltage detected by the battery voltage detection circuit;
• an ON/OFF state establishment means that performs an ON/OFF state establishment process based on the polarity of the potential of each of the input terminals detected by the input potential polarity detection circuit, establishes whether a state to be taken by each of the MOSFETs of the rectifier circuit is an ON state or an OFF state when the output of the generator is rectified and supplied to the battery;
• a during-charging FET control means that performs during-charging FET control, which controls the state of each MOSFET of the rectifier circuit so as to match the state to be taken established by the ON/OFF state establishment means when the charging necessity determination means has determined that the battery needs to be charged;
• a short-circuit control means that performs short-circuit control, which simultaneously sets the MOSFETs constituting all of the upper arms of the rectifier circuit to an ON state or simultaneously sets the MOSFETs constituting all of the lower arms of the rectifier circuit to an ON state to cause short-circuiting between output terminals of the generator when the charging necessity determination means has determined that battery charging needs to be paused;
• and a FET OFF means that causes a FET OFF time period in which all of the MOSFETs of the rectifier circuit are an OFF state to be generated in a set cycle at least when short-circuit control is performed;
• and
• the ON/OFF state establishment means is configured so as to perform the ON/OFF state establishment process based on the polarity of the potential of each input terminal of the rectifier circuit detected by the input potential polarity detection circuit during the FET OFF time period, also while the short-circuit control means is performing short-circuit control.