DER-237 - High Efficiency 18 W Power Supply

This document is an engineering report describing the adapter power supply using the TOPSwitch-JX TOP264VG. Intended as a universal evaluation platform for adapter applications, this power supply operates from a universal input and provides a 12 V, 18 W continuous output. PCB board size is 35mm x 50mm. By design, TOPSwitch-JX 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-JX'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 40 kHz to 60 kHz used for discrete MOSFETs) reduces the required transformer size, thereby reducing cost. The power supply meets Energy Star 2.0 >79% average efficiency, no-load <80 mW requirements at 230 VAC, and meets CISPR conducted EMI requirements with a margin of more than 6dB. The power supply provides thermal overload protection and utilizes large hysteresis for automatic recovery. It features primary-side sensing output overload and overvoltage protection even in the event of a single fault. This document provides complete design details including specifications, schematics, bill of materials, PCB layout, and transformer design and construction information. This information includes performance results related to regulation, efficiency, standby, transient load, power limit data, and conducted EMI scans.