RDK-736

Reference Design Report for a 7 W, Wide Range Input, Dual Output, Non-Isolated Title TM Flyback Converter Using LinkSwitch -XT2- 900 LNK3696P 85 VAC 440 VAC Input Specification 12.0 V / 500 mA, 5.0 V / 200 mA Outputs Application Embedded Power Supply Author Applications Engineering Department Document RDR-736 Number Date June 30, 2020 Revision 1.2 Summary and Features Highly integrated solution with 900 V rated power MOSFET Output voltage regulation: 12 V 10%, 5 V 5% Programmable current limit selection feature of LinkSwitch-XT2-900 Extremely fast transient response independent of load timing >80% efficiency at full load condition <120 mW no-load input power at 230 VAC >6 dB conducted EMI margin No optocoupler or Zener diode required for regulation Can withstand up to 450 VAC line input 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-736 7 W Dual Output Power Supply Using LNK3696P 30-Jun-20 Table of Contents 1 Introduction ............................................................................................................ 4 2 Power Supply Specification ...................................................................................... 5 3 Schematic ............................................................................................................... 6 4 Circuit Description ................................................................................................... 7 4.1 Input Rectifier and Filter ................................................................................... 7 4.2 LinkSwitch-XT2 Primary-Side ............................................................................. 7 4.3 Primary RCD Clamp .......................................................................................... 7 4.4 Output Rectification .......................................................................................... 7 4.5 Output Feedback .............................................................................................. 8 4.6 Output Overvoltage Protection .......................................................................... 8 4.7 Line Overvoltage Protection ............................................................................... 8 5 PCB Layout ............................................................................................................. 9 6 Bill of Materials ..................................................................................................... 10 7 Transformer Specification ...................................................................................... 11 7.1 Electrical Diagram ........................................................................................... 11 7.2 Electrical Specifications ................................................................................... 11 7.3 Material List ................................................................................................... 11 7.4 Transformer Build Diagram ............................................................................. 12 7.5 Transformer Construction ................................................................................ 12 7.6 Transformer Winding Illustrations .................................................................... 12 8 Transformer Design Spreadsheet ........................................................................... 16 9 Performance Data ................................................................................................. 20 9.1 No-Load Input Power ...................................................................................... 20 9.2 Efficiency ....................................................................................................... 21 9.2.1 Efficiency vs Line ..................................................................................... 21 9.2.2 Efficiency vs Load .................................................................................... 22 9.2.3 Average Efficiency .................................................................................... 23 9.3 Output Voltage Regulation .............................................................................. 24 9.3.1 5 V Load Regulation with Balanced Load ................................................... 24 9.3.2 12 V Load Regulation with Balanced Load.................................................. 25 9.3.3 5 V Load Regulation with Unbalanced Load ............................................... 26 9.3.4 12 V Load Regulation with Unbalanced Load .............................................. 28 9.3.5 Line Regulation ........................................................................................ 30 10 Waveforms ........................................................................................................... 32 10.1 Output Voltage Ripple ..................................................................................... 32 10.1.1 Ripple Measurement Technique ................................................................ 32 10.1.2 Ripple Waveforms at Full Load .................................................................. 33 10.1.3 Ripple Waveforms at No-Load ................................................................... 34 10.1.4 Ripple vs. Load ........................................................................................ 35 10.2 Switching Waveforms ...................................................................................... 37 10.2.1 V and I .............................................................................................. 37 DS DS 10.2.2 5 V Output Diode Voltage and Current ...................................................... 38 Power Integrations, Inc. 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