RDK-506

Reference Design Report for a 1.44 W Non- Title Isolated Buck Converter Using TM LinkSwitch -TN2 LNK3204D/P/G Input: 85 VAC 265 VAC Specification Output: 12 V, 120 mA Application Small Appliance Author Applications Engineering Department Document RDR-506 Number Date June 02, 2017 Revision 1.1 Summary and Features Highly integrated solution Lowest possible component count No optocoupler or Zener diode required for regulation Thermal overload protection with automatic recovery <30 mW no-load consumption >75% efficiency at full load <3% load regulation PATENT INFORMATION The products and applications illustrated herein (including transformer construction and circuits external to the products) may be covered by one or more U.S. and foreign patents, or potentially by pending U.S. and foreign patent applications assigned to Power Integrations. A complete list of Power Integrations patents may be found at www.powerint.com. Power Integrations grants its customers a license under certain patent rights as set forth at <RDR-506 1.44 W 12 V, 120 mA LNK3204D 02-Jun-17 Table of Contents 1 Introduction ...................................................................................................... 3 2 Power Supply Specification ................................................................................. 4 3 Schematic ......................................................................................................... 5 4 Circuit Description .............................................................................................. 6 4.1 Input EMI Filtering ....................................................................................... 6 4.2 LinkSwitch-TN2 IC Primary ........................................................................... 6 4.3 Output Rectification ..................................................................................... 7 4.4 Output Feedback ......................................................................................... 7 5 PCB Layout ........................................................................................................ 8 6 Bill of Materials .................................................................................................. 9 7 Transformer Design Spreadsheet ....................................................................... 10 8 Performance Data ............................................................................................ 11 8.1 Efficiency vs. Line ...................................................................................... 11 8.2 Efficiency vs. Load ..................................................................................... 12 8.3 No-Load Input Power ................................................................................. 13 8.4 Load Regulation ........................................................................................ 14 8.5 Line Regulation at Full Load ....................................................................... 15 9 Open Case Thermal Performance ...................................................................... 16 10 Waveforms ................................................................................................... 17 10.1 Switching Waveforms ................................................................................ 17 10.1.1 LNK3204D Waveforms ......................................................................... 17 10.1.2 LNK3204D Drain Voltage and Current Waveforms During Start-up .......... 17 10.1.3 Drain Current and Output Waveform During Output Short ...................... 18 10.1.4 Freewheeling Diode Waveforms ........................................................... 18 10.1.5 Output Voltage and Current Waveforms During Start-Up ........................ 19 10.2 Output Ripple Measurements ...................................................................... 20 11.2.1 Ripple Measurement Technique ............................................................... 20 10.2.2 Measurement Results .......................................................................... 21 10.2.3 Ripple Voltage Waveforms ................................................................... 22 11 Conductive EMI ............................................................................................ 23 11.1 120 mA Resistive Load, Floating Output (QPK / AV) ...................................... 23 11.1.1 Line ................................................................................................... 23 11.1.2 Neutral ............................................................................................... 25 12 Lighting Surge .............................................................................................. 27 12.1 Differential Mode Test ................................................................................ 27 13 Revision History ............................................................................................ 28 Important Note: Although this board is designed to satisfy safety isolation requirements, the engineering prototype has not been agency approved. Therefore, all testing should be performed using an isolation transformer to provide the AC input to the prototype board. Power Integrations, Inc. Tel: +1 408 414 9200 Fax: +1 408 414 9201 Page 2 of 29 www.power.com