The oscillation voltage (Ebm) is an important parameter of the characteristic constant of a high power microwave generator. When Ebm could be made high, it serves so as to improve the power conversion efficiency of a magnetron. Thus, the newly developed magnetron with 7% higher oscillation cut-off voltage than the present conventional one is manufactured by Matsushita Electric Industrial Co.Ltd, In addition to this, the utility AC power line current reduced harmonic type direct inverter AC-DC power converter suitable and acceptable for driving this magnetron is proposed in this paper. This direct high frequency inverter type soft switching PWM AC-DC converter has the voltage-boost function based on active clamp scheme with soft switching pulse modulation strategy topology. This paper describes a novel type active clamp AC-DC power converter circuit defined as direct high frequency inverter and the switching operation of this power converter is described and discussed on the basis of simulation and experimental results. The operating characteristics of this soft switching direct high frequency inverter type AC-DC power converter using IGBTs that incorporates the harmonic current improvement as well as power factor correction are evaluated and discussed from a practical point of view as compared with the conventional AC-DC power converter.