DER-197 - 65W adapter

This engineering report introduces the notebook adapter power supply using Power Integrations® TOPSwitch®-HX TOP258EN. The power supply operates over a universal input range and provides a 19 V, 65 W output. It is designed and tested to operate in a sealed enclosure at external ambient temperatures up to 40 °C. The high voltage (700 V) rating of the MOSFETs in TOPSwitch-HX allows for an increased transformer primary to secondary turns ratio in this design (relative to designs using 600 V or 650 V MOSFETs). This allows the use of 60 V, 20 A Schottky output diodes instead of 100 V, 40A diodes; increasing efficiency and reducing cost. By design, TOPSwitch-HX maintains nearly constant efficiency over a very wide load range without the need for special operating modes to meet specific load thresholds. This optimizes performance of existing and emerging energy efficiency regulations. Maintaining constant efficiency ensures that the design is optimized for future changes in energy efficiency regulations without the need for redesign. TOPSwitch-HX's low MOSFET capacitance enables higher switching frequencies without the efficiency loss seen with standard discrete MOSFETs. The 132 kHz switching frequency (rather than the 70 kHz to 100 kHz used for discrete MOSFETs) reduces the required transformer size, thereby reducing cost.