High-frequency switched mode power with small capacity filter inverters

This paper proposes a high frequency switched mode power amplifier which incorporates small capacity filter inverter. PWM inverters require low-pass filters in order to reduce switching harmonics. However, in the high frequency systems such as class D power amplifiers, the cut-off frequency of low-pass filter must set at considerably high-frequency. Thus, harmonic distortion of the output voltage enlarges. Increasing output voltage level is effective to reduce harmonic distortion of the output voltage and low-pass filter size. The proposed systems are consisted of 5-level inverter and cascade connected several low voltage full bridge inverters without isolated DC power sources for filtering output voltage. The 5-level inverter generates a stepwise waveform with 5-level voltage and the low voltage filter inverter superimposes harmonic components to compensate for the voltage waveform distortion. Therefore, the proposed system can reduce total switching loss and can increase output voltage levels. In this paper, effectiveness of the proposed systems are verified through several experimental tests.