This paper proposes a novel inverter drive system to improve input power factor of the single-phase diode rectifier. Conventional rectifier needs a high frequency switching devices and a reactor to improve input power factor. However, the proposed power converter doesn’t need the switching device, the electrolytic capacitor and the reactor. By making many ripples across the dc-bus voltage and then, the input power factor can be improved. The proposed system consists of an only single-phase diode rectifier, small film capacitor, three-phase inverter and motor. The proposed system adopts an interior permanent magnet (IPM) synchronous motor. The IPM motor is well known as a high efficiency motor and can get field weakening. The basic ideas of the inverter control method are based on two following operations. First, the inverter’s controlled synchronous with the dc-bus ripple voltage by field-weakening method.The other is direct active power feeding from the source side to the motor without smoothing the dc-bus voltage. This paper describes that the proposed method can obtain the input power factor 97.3% by experimental tests, and realize the small size and the long life of the system.