Over-current protection method and device

A method and device to protect a drive circuit ( 32 ) of a power assist motor ( 22 ) from an over-current condition. A sensor ( 24 ) takes instantaneous measurements of the current provided to the motor ( 22 ). A charge accumulation determining function ( 28 ) determines charge accumulation from the instantaneous current samples. When the current provided to the motor ( 22 ) exceeds a threshold value ( 40 ) and the determined charge accumulation exceeds a threshold charge accumulation ( 50 ), the current provided to the motor ( 22 ) is decreased. When the current provided to the motor ( 22 ) is less than the threshold current value ( 40 ) for more than a predetermined period, the determined charge accumulation is reduced by a predetermined factor. After the charge accumulation has been reduced below a predetermined threshold ( 92 ), the current provided to the motor ( 22 ) is increased.