Integrated filters for switch-mode power supplies

A consequence of a maturing switch-mode power supply technology is an increasing standardisation of components and a smaller variation in switching frequency. Input and output filters account for a major portion of component cost and in the face of better devices, higher levels of silicon integration and improved packaging, it has become important to improve the filter technology. It is proposed that a range of integrated filters could be introduced using a few standardised cut-off frequencies. By careful design it may be possible to control the frequency domain transfer function sufficiently to integrate both of the series connected low frequency and high frequency low pass filters into a single component, The suitability of electrolytic, metal film and ceramic capacitor based integrated filters are investigated, and analysis and experimental results are also presented.