Design of 4th Order Resonance Filter for 5.4 W 20 MHz Buck Converter with PCB Integrated Inductor

Size reduction of passive components in power converters especially magnetic components is essential to reduce the overall size of the converter and achieve higher power densities. For that purpose, this paper presents a detailed design procedure of a 4^th order resonance output filter to show the advantages it provides in terms of passives size and loss reduction. A design study comparison is presented between 2^nd order, 4^th order and 4^th order resonance filters in a 5.4 W, 20 MHz buck converter with PCB integrated solenoid inductors. The comparison considers the same circuit specifications and PCB manufacturing capabilities for the PCB inductors. It is found that there is potential for a total inductor size reduction of 38% with a corresponding increase in full load inductor efficiency of 2.1% and full load circuit efficiency of 1.3% provided by the 4^th order resonance filter compared to a standard 2^nd order filter in a 5.4 W buck converter switching at 20 MHz.