RDK-737

Reference Design Report for 1.44 W Non- Title Isolated Buck Converter Using 900 V TM LinkSwitch -TN2 LNK3294G/P Specification 85 VAC 440 VAC Input 12 V, 120 mA Output Application Small Appliance / Metering Application Author Applications Engineering Department Document RDR-737 Number Date June 9, 2020 Revision 1.1 Summary and Features 900 V maximum drain voltage Highly integrated solution Lowest possible component count No optocoupler required for regulation Thermal overload protection with automatic recovery <30 mW no-load consumption >73% efficiency at full load <5% 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.power.com. Power Integrations grants its customers a license under certain patent rights as set forth at RDR-737 1.44 W 12 V, 120 mA LNK3294G/P 09-Jun-20 Table of Contents 1 Introduction ......................................................................................................... 4 2 Power Supply Specification ................................................................................... 5 3 Schematic ............................................................................................................ 6 4 Circuit Description ................................................................................................ 7 4.1 Input EMI Filtering ......................................................................................... 7 4.2 900 V LinkSwitch-TN2 .................................................................................... 7 4.3 Output Rectification ....................................................................................... 8 4.4 Output Feedback ........................................................................................... 8 4.5 Optional Components ..................................................................................... 8 5 Bill of Materials .................................................................................................. 10 6 Design Spreadsheet ............................................................................................ 11 7 Performance Data .............................................................................................. 13 7.1 Efficiency vs. Line ........................................................................................ 13 7.2 Efficiency vs. Load ....................................................................................... 14 7.3 Average Efficiency ....................................................................................... 15 7.3.1 85 VAC / 60 Hz ..................................................................................... 15 7.3.2 115 VAC / 60 Hz ................................................................................... 15 7.3.3 230 VAC / 50 Hz ................................................................................... 15 7.3.4 265 VAC / 50 Hz ................................................................................... 15 7.3.5 440 VAC / 50 Hz ................................................................................... 15 7.4 Standby Mode Efficiency .............................................................................. 16 7.4.1 0.2 W Input Power ................................................................................ 17 7.4.2 0.3 W Input Power ................................................................................ 17 7.4.3 0.5 W Input Power ................................................................................ 17 7.4.4 1.0 W Input Power ................................................................................ 17 7.5 No-Load Input Power ................................................................................... 18 7.6 Load Regulation .......................................................................................... 19 7.7 Line Regulation at Full Load ......................................................................... 20 8 Open Case Thermal Performance ........................................................................ 21 9 Waveforms ........................................................................................................ 22 9.1 Switching Waveforms ................................................................................... 22 9.1.1 LNK3294P Waveforms ........................................................................... 22 9.1.2 LNK3294P Drain Voltage and Current Waveforms During Start-Up ........... 23 9.1.3 Drain Current and Output Waveform During Output Short ....................... 23 9.1.4 Freewheeling Diode Waveforms ............................................................. 24 9.1.5 Output Voltage and Current Waveforms During Start-Up (CC mode) ........ 25 9.2 Output Ripple Measurements ........................................................................ 26 9.2.1 Ripple Measurement Technique ............................................................. 26 9.2.2 Measurement Results ............................................................................ 27 9.2.3 Ripple Voltage Waveforms ..................................................................... 28 9.2.4 Ripple Voltage Waveforms Using 100 F Output Capacitor ...................... 29 10 Conductive EMI ............................................................................................... 30 10.1 120 mA Resistive Load, Floating Output (QPK / AV) ....................................... 30 Power Integrations, Inc. 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