DN0002 Design note 10W offline LED driver based on VIPER27 Designs from our labs describe tested circuit designs from ST labs which provide optimized solutions for specific applications. For more information or support, visit www.st.com By Luigi Galioto Main components VIPER27 Offline high voltage converter SEA05 Advanced constant voltage and constant current controller Specification 10W LED driver Wide input voltage range: 88Vac to 265Vac 300mA LED current Isolated SMPS Short circuit protection Circuit description The use of LEDs in lighting applications is becoming increasingly popular due to: rapid improvements in lighting efficiency, longer life, higher reliability and overall cost effectiveness. This converter is a simple example of an offline isolated LED application (10W). The LEDs are driven by the VIPER27 high voltage converter. The secondary side is managed by the SEA05 advanced CC/CV controller. Excellent results in terms of current control precision (±3%) and efficiency performance (η>80%), combined with the compact form factor which can fit in existing bulb housing, are key benefits. May 2012 DN0002 Rev 1 1/6 www.st.com Figure 1. Circuit diagram May 2012 DN0002 Rev 1 2/6 www.st.com Measurement results The board was tested in terms of efficiency, output voltage limitation and LED current regulation for a wide input voltage range. Table 1 shows the results obtained for a 30 minute test. High efficiency and excellent LED current regulation were obtained. Table 1. Experimental results Start up tests with Vin=110V and Vin=230V were also reported in full load and no load conditions. The behavior of Vout, Vcc and Iout were monitored. Figure 2. Test results: start up sequence at full load condition May 2012 DN0002 Rev 1 3/6 www.st.com Figure 3. Test results: start up sequence at no load condition The VIPER27 is protected against short circuits on the secondary rectifier and secondary winding, and a hard-saturation of the flyback transformer. Tests were conducted where the board was subject to short circuits and it protected itself well. The behavior shown in figure 3 illustrates the typical low frequency intermittent operation (hiccup- mode operation). May 2012 DN0002 Rev 1 4/6 www.st.com Figure 4. Test results: short circuit condition Support material Related design support material EVLVIP27-7WLED: 3.5W to 7W high power factor offline LED driver based on VIPer devices Gerber files for 10W LED driver http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_DIAGRAM/PCB_LAYO UT/10wled_pcb_layout.zip Documentation Magnetica, Switch Mode Transformer 10W 55kHz 980uH – see attachment at end of document. www.magnetica.eu Code 1715.0032 AN3212: 3.5W to 7W high power factor offline LED driver based on VIPer devices Revision history Date 15-May-2012 May 2012 Version 1 Changes Initial release DN0002 Rev 1 5/6 www.st.com Please Read Carefully Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at anytime, without notice. 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All other names are the property of their respective owners. © 2012 STMicroelectronics - All rights reserved STMicroelectronics group of companies Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel Italy - Japan - Malaysia - Malta - Morocco - Philippines - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America www.st.com May 2012 DN0002 Rev 1 6/6 www.st.com STP 21 Code: 1715.0032 Product Technical Specification Product: Switch Mode Transformer 10W 55kHz 980uH Customer: STMICROELECTRONICS Date : 27.04.12 Customer code: Revision: 01 Page 1 of 2 TYPICAL APPLICATION TECHNICAL DATA TRANSFORMER FOR FLYBACK POWER SUPPLIES IN INDUCTANCE APPLICATIONS WITH CONTROLLER VIPER28 (MEASURE 1KHZ, TA 20°C) PIN 3-1 CIRCUIT DIAGRAM PIN 4-5 PIN 8-7 980 uH ±15% 39 uH ±15% 179 uH ±15% RESISTANCE (MEASURE D.C, TA 20°C) 3-1 4-5 PIN 8-7 1.22 MAX 280 m MAX 250 m MAX PIN PIN 1 TRANSFORMER RATIO 8 (MEASURE 10KHZ, TA 20°C) PIN PIN 3-1 3-1 4-5 8-7 5 5% 2.36 5% 2.5 % NOM LEAKAGE INDUCTANCE (MEASURE 3-1 AND 4-5-7-8 IN S.C, F 10KHZ, TA 20°C) 14 PF NOM PARASITIC CAPACITANCE 3 (MEASURE 3-1, F 1MHZ, TA 20°C) 4 7 0.94AP MAX SATURATION CURRENT (MEASURE 3-1, BSAT 0.32T, TA 20°C) 0.85 AP MAX OPERATING CURRENT (MEASURE 3-1, PMAX 10W ,F 55KHZ, TA 20°C) 5 55 KHZ NOM OPERATING FREQUENCY (PMAX 10W , TA 20°C) -10°C +45°C OPERATING TEMPERATURE RANGE (PMAX 10W ) 4KV PRIMARY TO SECONDARY INSULATION (F 50HZ,DURATION TEST 2”, TA 20°C) 27X22XH18 mm MAXIMUM DIMENSIONS 12 g APPROX WEIGHT PIN DESCRIPTION PIN(*) PIN(*) FUNCTION 1 2 3 4 5 PRIMARY +VB 120-400VDC 6 NOT USED 7 PRIMARY DRAIN 8 AUXILIARY 9 +15V 15mA AUXILIARY GROUND (*)PIN WITH THE SAME SUBSCRIPT MUST BE CONNECTED TOGETHER ON PCB MOR&D0014-00 FUNCTION NOT USED SECONDARY GROUND SECONDARY NOT USED +33V 300mA Rev.00 02/09/08 MAGNETICA Via Marcora, 20 60022 Castelfidardo (AN) Tel +39 071 7823855 Copyright Magnetica, cannot be reproduced even partially without written authorization. STP 21 Code: 1715.0032 Product Technical Specification Product: Switch Mode Transformer 10W 55kHz 980uH Customer: STMICROELECTRONICS Date : 27.04.12 Customer code: Revision: 01 Page 2 of 2 DIMENSIONAL DRAWING LABEL 18 MAX 3.5 MIN 27 MAX 22 MAX 9 1 8 2 21 MAX 3 7 4 6 5 19.05 15.24 5.08 7.62 15.24 0.7 (X9), RECOMMENDED PCB HOLE 1.1 (X9) BOTTOM VIEW (PIN SIDE) DIMENSIONS IN MILLIMETERS, DRAWING NOT IN SCALE MOR&D0014-00 Rev.00 02/09/08 MAGNETICA Via Marcora, 20 60022 Castelfidardo (AN) Tel +39 071 7823855 Copyright Magnetica, cannot be reproduced even partially without written authorization.