NOVELTY - The charger has a snubber circuit unit (50) which is provided with a first capacitor and a second capacitor connected to an output terminal of a rectifier diode (40) to charge a surge voltage from the rectifier diode. A first diode, a second diode, and a third diode are connected while forming a closed looped with the first capacitor and the second capacitor to form a closed loop discharge path of surge voltages discharged from the first capacitor and the second capacitor.    USE - Onboard charger for charging battery of vehicle. Uses include but are not limited to motor car such as passenger car, sport utility vehicle (SUV), bus, truck and wagon, watercraft such as boat and ship, aircraft, hybrid vehicle, electric car, plug in hybrid electric vehicle, hydrogen propulsion vehicle, fuel cell vehicle, gasoline-claimant and electrical claimant vehicles.    ADVANTAGE - The output current ripple is reduced by improving snubber circuit unit of the on-board charger. The surge voltage generated in rectifier diode and output current ripple are reduced by arranging two capacitors and three diodes in the transformer secondary rectifier of the on-board charger. The snubber circuit unit reduces the ripple of output current while minimizing surge voltage of rectifier diode and preventing the lifespan reduction of the output capacitor and the high voltage battery.    DETAILED DESCRIPTION - The charger has a full bridge input unit (20) that is connected to a power factor compensator (10) connected to an alternating current (AC) normal power supply to convert a direct current (DC) voltage into an AC voltage. A main transformer (30) boosts the AC voltage from the full bridge input unit. The rectifier diode converts the boosted AC voltage into a DC voltage. The snubber circuit unit removes a surged high voltage generated upon turning off the rectifier diode. An output inductor (60) converts an output voltage into DC voltage with a ripple reduced together with an output capacitor (70). The output capacitor converts the output voltage into the DC voltage with the ripple reduced together with the output inductor. An INDEPENDENT CLAIM is included for a method for charging the battery.    DESCRIPTION OF DRAWING(S) - The drawing shows a circuit diagram of the onboard charger.    Power factor compensator (10)    Full bridge input unit (20)    Main transformer (30)    Rectifier diode (40)    Snubber circuit unit (50)    Output inductor (60)    Output capacitor (70)