Environmental concerns lead to stringent efficiency requirements when designing modern power supplies. Compactness and form factor are other drivers for high efficiency, while in all cases, cost-effectiveness remains a crucial requirement. These constraints dramatically affect the PFC stage and the EMI filter, which can easily consume from 3% to 6% of the output power at low line, full load.
The topic shows in the first step that the control scheme can help to optimize the efficiency over the load range while reducing the cost by a multi-mode concept. In the second step, the architecture aspect will be considered within particular the bridgeless and interleaved approaches. There is also a comparison of the respective merits of these solutions in a 300 W, wide-mains application.