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| Design Idea DI-26 (R) TOPSwitch-GX 7 W Digital Video Broadcast-Terrestrial (DVB-T) Supply Application DVB-T Device TOP242P Power Output 7W Input Voltage 195 to 265 VAC Output Voltage 2.5 V / 3.3 V / 6.2 V / 30 V Flyback (R) Topology Design Highlights * Meets CISPR22B/EN55022B conducted EMI limits with output return grounded * <0.5 W input power at zero load * 132 kHz operation and programmable current limit allows small, low cost EF16 transformer for 7 W output * Low component count design occupies 80 x 30 x 16 mm * Integrated soft-start reduces start-up component stresses Operation The TOPSwitch-GX flyback supply provides 4 outputs, delivering 7 W from a 230 VAC 15% input. The TOP242P was selected for low cost, the DIP-8 package removing the need for an external heat sink. Resistor R7 programs the internal TOP242P current limit to 78% of nominal, just above the level needed for full load at low line. This feature allows a more continuous transformer design for better efficiency and cross-regulation, without requiring a larger core size. C15 2.2 nF Y1 D3 UF4002 T1 Resistor R12, C10 and L2 filter conducted EMI; R12 is a flame-proof fusible type, also functioning as a fuse. For lower cost, if the supply does not have to meet conducted EMI with the output connected to earth ground, the common mode choke can be replaced with a filter. A Zener clamp (D11 and VR1) was selected over an RCD clamp to minimize zero load consumption. Secondary side feedback is taken from the 3.3 V 5% output since this has the tightest tolerance requirement. The 2.5 V 5% output is derived directly from the 3.3 V output using D4. A 60 V Schottky was selected for D1, since the slightly higher forward drop centers the 6.2 V and 30 V outputs. Post-filters (L1/C3, L2/C12 and R1/C5) reduce output noise and ripple to <1% of the respective output voltage. A softfinish capacitor (C7) eliminates output turn-on overshoot. Key Design Points * The transformer is designed to operate in continuous mode for tight secondary cross-regulation. R1 150 L2 4.7 H 1.8 A C4 470 F 10 V C1, C2 220 F 35 V C5 10 F 50 V C12 L1 47 F 4.7 H 35 V 1.8 A C3 47 F 35 V R6 75 R5 1 k R2 15 k 1% 30 V, 5 mA 8 1 D7-D10 1N4005 VR1 P6KE200 7 D2 SB140 6.2 V, 0.4 A D11 BYW95C C9 6.8 F 400 V 2 D1 SR506 6 3.3 V, 0.5 A 2.5 V, 1 A D4 1N5400 RTN 5 L3 10 mH 0.1 A 3 TOPSwitch-GX U1 TOP242P C10 47 nF X2 R12 8.2 Fusible 195-265 VAC D M CONTROL C 4 D6 1N4148 C8 1 F 50 V U3 PC817 R7 10 k C6 0.1 F R4 3.3 k U2 LMV431 R3 9.1 k 1% PI-3023-0916102 S C13 100 nF R11 6.8 C14 47 F 10 V C7 10 F 16 V Figure 1. TOPSwitch-GX 7 W Multiple Output Supply for DVB-T. DI-26 www.powerint.com September 2002 DI-26 * Safety Y1 capacitor C15 is connected between secondary return and primary DC rail to minimize noise coupling during AC common mode line transients. * Good layout practices should be followed: - Locate C13, R11 and C14 close to U1, with grounds returned to the SOURCE pin. - Minimize the primary and secondary loop areas to reduce parasitic leakage inductance, improve EMI and cross-regulation. TRANSFORMER PARAMETERS Core Material Bobbin EF16 gapped for 190 nH/T2 EF16-8 pin Primary: 105T, 35 AWG Bias: 17T, 35 AWG 3.3 V Secondary: 4T, 4 x 26 AWG T.I.W. 6.2 V Secondary: 3T, 26 AWG T.I.W. 30 V Secondary: 29T, 30 AWG T.I.W. (T.I.W. = Triple Insulated Wire) Primary (1-2), Tape, Bias (3-4), Tape, 3.3 V (5-6), 5 V (6-7), 30 V (7-8) 4 Line Regulation (%) 3 2 1 0 -1 -2 -3 -4 -5 190 210 230 2.5 V 3.3 V 6.2 V 3.0 V 250 270 Line Voltage (VAC) Figure 2. Full Power Line Regulation. PI-3022-080202 Winding Details 80 70 60 QP Limit Line AV Limit Line Winding Order (Pin Numbers) Primary: 2.1 mH 10%, Leakge: 50 H (max.) Inductance Primary Resonant 650 kHz (minimum) Frequency Amplitude (dBV) 50 40 30 20 -10 0 -10 -20 0.15 Quasi-Peak Scan Average Scan Table 1. Transformer Construction Information. Load Range (%) -10 -7 10-100 10-100 10-100 100 Voltage (V) 2.5 3.3 6.2 30 Regulation (%) -4 -3 -2 -1 0 1 2 3 4 7 EN_V_QP EN_V_AV 1 10 PI-3021-080202 5 30 Table 2. Worst Case Output Cross-Regulation-all Outputs Taken from Minimum to Maximum Load. Frequency (MHz) Figure 3. Conducted EMI, 230 VAC, Full Power, Output Earth Grounded. For the latest updates, visit our Web site: www.powerint.com Power Integrations reserves the right to make changes to its products at any time to improve reliability or manufacturability. Power Integrations does not assume any liability arising from the use of any device or circuit described herein, nor does it convey any license under its patent rights or the rights of others. The products and applications illustrated herein 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. The PI Logo, TOPSwitch, TinySwitch and EcoSmart are registered trademarks of Power Integrations, Inc. PI Expert is a trademark of Power Integrations, Inc. (c)Copyright 2002, Power Integrations, Inc. WORLD HEADQUARTERS AMERICAS Power Integrations, Inc. San Jose, CA 95138 USA Customer Service: Phone: +1 408-414-9665 Fax: +1 408-414-9765 e-mail: usasales@powerint.com CHINA Power Integrations International Holdings, Inc. China Phone: +86-755-8367-5143 Fax: +86-755-8377-9610 e-mail: chinasales@powerint.com EUROPE & AFRICA Power Integrations (Europe) Ltd. United Kingdom Phone: +44-1344-462-300 Fax: +44-1344-311-732 e-mail: eurosales@powerint.com KOREA Power Integrations International Holdings, Inc. Seoul, Korea Phone: +82-2-782-2840 Fax: +82-2-782-4427 e-mail: koreasales@powerint.com SINGAPORE Power Integrations, Singapore Republic of Singapore 308900 Phone: +65-6358-2160 Fax: +65-6358-2015 e-mail: singaporesales@powerint.com JAPAN Power Integrations, K.K. Keihin-Tatemono 1st Bldg. Japan Phone: +81-45-471-1021 Fax: +81-45-471-3717 e-mail: japansales@powerint.com APPLICATIONS HOTLINE World Wide +1-408-414-9660 TAIWAN Power Integrations International Holdings, Inc. Taipei, Taiwan Phone: +886-2-2727-1221 Fax: +886-2-2727-1223 e-mail: taiwansales@powerint.com INDIA (Technical Support) Innovatech Bangalore, India Phone: +91-80-226-6023 Fax: +91-80-228-9727 e-mail: indiasales@powerint.com APPLICATIONS FAX World Wide +1-408-414-9760 A 9/02 www.powerint.com |
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