Universal AC input high density power adapter design with a Clamped Series Resonant Converter

In this paper, we present the design and fabrication of a high density laptop adapter with a Clamped Series Resonant Converter (CSRC), as a possible alternative to traditional Flyback converters for power adapters in portable electronics. The target is to design for universal AC input up to a power of 100 W with power density of 6-7 W/in³. The converter is frequency controlled, and all switches exhibit Zero-Current Switching (ZCS). In this paper, we show that by utilizing the magnetizing inductance, the converter can be tuned for Zero Voltage Switching (ZVS), and by adding a switched capacitor circuit to extend the input voltage range, we can realize a very compact design that is suitable for power adapters with or without power factor correction. Low transformer stresses compared to Flyback type designs enable high densities, even with a resonant magnetic. Prototype test results with a 45 W laptop adapter are presented. Our initial testing with diode rectification indicated very good efficiency. Versions with synchronous rectification promise higher efficiencies by at least 1%, which will be ideal for energy saving low power devices.