Reference Design Report for a 30 W Power TM Title Supply Using InnoSwitch 3-AQ INN3977CQ 30 VDC 550 VDC Input Specification 30 VDC 12 V / 0.85 A 60 VDC 12 V / 1.25 A 130-550 VDC 12 V / 2.5 A Outputs Application Wide Input Range For Automotive Author Applications Engineering Department Document RDR-840Q Number Date August 31, 2020 Revision 1.3 Summary and Features Wide input voltage range: 30 VDC to 550 VDC InnoSwitch3-AQ industry first AC/DC ICs with isolated, safety rated integrated feedback Built-in synchronous rectification for >85% efficiency All the benefits of secondary-side control with the simplicity of primary-side regulation o Insensitive to transformer variation o Extremely fast transient response independent of load timing 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-840Q 30 W 12 V, 2.5 A using INN3977CQ 31-Aug-20 Table of Contents 1 Introduction ......................................................................................................... 4 2 Power Supply Specification ................................................................................... 5 3 Schematic ............................................................................................................ 6 3.1 SR FET Version .............................................................................................. 6 3.2 Qspeed Diode Version .................................................................................... 6 4 Circuit Description ................................................................................................ 7 4.1 INN3977CQ IC Primary .................................................................................. 7 4.2 INN3977CQ IC Secondary .............................................................................. 7 5 PCB Layout .......................................................................................................... 8 6 Bill of Materials .................................................................................................. 10 6.1 Main Board .................................................................................................. 10 6.2 Mechanical Parts .......................................................................................... 11 7 Transformer Design ............................................................................................ 12 7.1 Electrical Diagram ........................................................................................ 12 7.2 Electrical Specifications ................................................................................ 12 7.3 Material List ................................................................................................ 12 7.4 Transformer Build Diagram .......................................................................... 13 7.5 Transformer Instructions .............................................................................. 13 7.6 Winding Illustrations .................................................................................... 14 8 Performance Data with SR FET version ................................................................ 20 8.1 Average Efficiency ....................................................................................... 20 8.1.1 30 VDC, 12 V 0.85 A (10 W) .................................................................. 20 8.1.2 60 VDC, 12 V 1.25 A (15 W) .................................................................. 21 8.1.3 130 VDC, 12 V 2.5 A (30 W) .................................................................. 22 8.1.4 400 VDC, 12 V 2.5 A (30 W) .................................................................. 23 8.1.5 550 VDC, 12 V 2.5 A (30 W) .................................................................. 24 8.2 Efficiency vs. Load and Line ......................................................................... 25 8.2.1 SR FET Version ..................................................................................... 25 8.2.2 Qspeed Version ..................................................................................... 26 8.3 No-Load Input Power ................................................................................... 27 8.4 Load and Line Regulation ............................................................................. 28 8.5 CV/CC ......................................................................................................... 29 9 Waveforms ........................................................................................................ 30 9.1 Switching Waveforms ................................................................................... 30 9.1.1 Drain Voltage and Current, Steady-State.............................................. 30 9.1.2 Drain Voltage and Current, Start-up..................................................... 32 9.1.3 SR FET Waveforms, Steady-State......................................................... 34 9.1.4 SR FET Waveforms, Start-up............................................................... 36 9.1.5 FWD Pin, Steady-State .......................................................................... 38 9.1.6 FWD Pin, Start-up ................................................................................. 40 9.1.7 Output Voltage and Current, Startup CR Load ......................................... 42 9.2 Output Ripple Measurements (SR FET) ......................................................... 44 9.2.1 Ripple Measurement Technique ............................................................. 44 Power Integrations, Inc. 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