DAK-71A Power Integrations

Engineering Prototype Report for EP-71 6.6 W DC-DC Converter Using Title DPA-Switch (DPA423G) Specification 36-72 VDC Input, 3.3 V, 2 A Output Standby Supply for Distributed Power Application Architectures Author Power Integrations Applications Department Document EPR-71 Number Date 19-Jul-2005 Revision 1.2 Summary and Features High efficiency, low cost, low component count solution Ideally suited as a standby supply in a larger 48 V input system The DPA-Switch IC integrates PWM controller and 220 V MOSFET switching device Accurate 400 kHz trimmed internal oscillator Accurate OV/UV protection Hysteretic thermal shutdown Overload, open loop and short-circuit protection Cycle skipping for regulation at no-load without a minimum load Small footprint 1.85 1 , low overall height 0.9 , two-layer PCB 100% surface mount construction The products and applications illustrated herein (including circuits external to the products and transformer construction) 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.comT. Power Integrations 5245 Hellyer Avenue, San Jose, CA 95138 USA. Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com EP-71 3.3 V, 2 A DC-DC Power Supply 19-Jul-2005 Table Of Contents 1 Introduction..................................................................................................................3 2 Power Supply Specification.........................................................................................4 3 Schematic ...................................................................................................................5 4 Circuit Description .......................................................................................................6 4.1 DPA-Switch Primary............................................................................................6 4.2 Output Rectification .............................................................................................6 4.3 Output Feedback.................................................................................................7 5 PCB Layout .................................................................................................................7 6 Bill of Materials............................................................................................................8 7 Transformer Specification ...........................................................................................9 7.1 Electrical Diagram ...............................................................................................9 7.2 Electrical Specifications.......................................................................................9 7.3 Materials..............................................................................................................9 7.4 Transformer Build Diagram ...............................................................................10 7.5 Transformer Construction..................................................................................10 8 Transformer Spreadsheets........................................................................................11 9 Performance Data .....................................................................................................13 9.1 Efficiency...........................................................................................................13 9.2 Regulation .........................................................................................................14 9.2.1 Load...............................................................................................................14 9.2.2 Line................................................................................................................14 9.3 Peak Power.......................................................................................................15 10 Waveforms ................................................................................................................15 10.1 Drain Voltage and Current, Full Load Operation ...............................................15 10.2 Output Voltage Start-Up Profile.........................................................................16 10.3 Drain Voltage and Current Start-Up Profile .......................................................16 10.4 Load Transient Response (75% to 100% Load Step) .......................................16 10.5 Output Ripple Measurements............................................................................18 10.5.1 Ripple Measurement Technique ....................................................................18 10.5.2 Output Ripple Measurements ........................................................................19 11 Thermal Performance................................................................................................20 12 Control Loop Measurements .....................................................................................22 12.1 36 VDC Maximum and Nominal Load ...............................................................22 12.2 57 VDC Maximum Load ....................................................................................23 13 Revision History ........................................................................................................24 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 isolated source to provide power to the prototype board. Power Integrations Tel: +1 408 414 9200 Fax: +1 408 414 9201 www.powerint.com Page 2 of 28