Partially resonant active filter using the digital PWM control circuit with the DSP

The partially resonant active filter, as a pre-regulator, using the digital PWM control circuit with the DSP is proposed to improve the power factor and input current harmonic distortion factor. The steady-state and dynamic characteristics of this active filter are analysed and the relationship among the circuit parameters, variables and performance characteristics such as the pre-regulation of the output voltage, input power factor, input current harmonic distortion, boundaries of stability and so forth are defined. Using the partially resonant active filter, high power efficiency over 91% is obtained and the high frequency switching noise is suppressed. Also, the digital control with the DSP is versatile and consequently, the power factor over 0.99 and total harmonic distortion factor less than 1% are easily realized.