TOP BUCK

www.powerint.com Design Idea DI-11 TinySwitch-II Buck Converter August 2001DI-11 Figure 1. TinySwitch-II 12 V, 1.2 W Buck Converter. Application General Purpose TNY264P 12 V Power Output 1.2 W Input Voltage Output Voltage TopologyDevice 85-265 VAC Buck ® POWER INTEGRATIONS, INC. ® Design Highlights • Lowest cost non-isolated switch mode converter • Entirely producible in SMD (13 components) • No transformer required • Meets 2005 European 300 mW no-load consumption requirement • Meets EN55022B/CISPR22 • Universal input voltage range (85–265 VAC) • Short circuit and thermally protected • Excellent line and load regulation • Less than 10 ms startup time Operation The TinySwitch-II buck converter supply provides a non-isolated 12 V output rated at 100 mA. The design shown takes advantage of many of the built-in features of the TNY264. AC input voltage is rectified and filtered by D1, C1 and C2 to create a high voltage DC bus which is connected to the input of the buck stage. The fusible, flameproof resistor R1 is used in place of a fuse to reduce system cost and it also provides differential mode noise filtering. With the integrated frequency jitter it is possible to meet international conducted EMI requirements with a simple PI-filter formed by C1, L1 and C2. The freewheeling diode D2, the inductance L2 and the output capacitor C4 form the buck stage. Zener diode VR1 and the forward drop of the optocoupler diode U2 determine the output voltage. The built-in auto-restart function of TinySwitch-II protects the output in case of short circuit or an open control loop condition by reducing the delivered power to less than 6% of the nominal output power. Key Design Points • Preferred discontinuous mode of operation is accomplished by limiting the output current to 50% of the minimum internal current limit. • • The voltage rating of L2 has to be greater than √2 x V ACMAX . • Size capacitors C1 and C2 according to the output power and surge withstand requirements. • Optocoupler U2 provides level shifting only and therefore doesn't need to be safety rated. • Select output capacitor C4 according to the ripple requirement: ESR C4 ≤ V OUT_RIPPLE / I LIMIT . • Minimum recommended output voltage is 5 V (smaller voltages may cause non-preferred continuous mode operation.) • Diode D2 must be an ultrafast type t r r ≤ 35 ns. TinySwitch-II R1 8.2 Ω, 2 W Fusible C1 2.2 µF 400 V C2 2.2 µF 400 V D2 BYV26C C4 100 µF 16 V 12 V ±5% 100 mA RTN 85-265 VAC VR1 BZX79-B11 U2 D1 1N4007 L1 1.5 mH L2 820 µH 300 mA U1 TNY264P EN BP SD C3 0.1 µF 50 V U2 KP1010 PI-2780-081301 L 2 ≥ L MIN_PWR L MIN_SOA (see Table 1) www.powerint.comA8/01 DI-11 Figure 4. Load regulation at 85 VAC and 265 VAC. Table 1. LMIN_S0A and IO_MAX (discontinuous mode). 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 PI Logo, TOPSwitch, TinySwitch and EcoSmart are registered trademarks of Power Integrations, Inc. ©Copyright 2001, Power Integrations, Inc. KOREA Power Integrations International Holdings, Inc. Seoul, Korea Phone: +82-2-568-7520 Fax: +82-2-568-7474 e-mail: koreasales@powerint.com 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 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 TAIWAN Power Integrations International Holdings, Inc. Taipei, Taiwan Phone: +886-2-2727-1221 Fax: +886-2-2727-1223 e-mail: taiwansales@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 CHINA Power Integrations International Holdings, Inc. China Phone: +86-755-367-5143 Fax: +86-755-377-9610 e-mail: chinasales@powerint.com INDIA (Technical Support) Innovatech Bangalore, India Phone: +91-80-226-6023 Fax: +91-80-228-9727 e-mail: indiasales@powerint.com APPLICATIONS HOTLINE World Wide +1-408-414-9660 APPLICATIONS FAX World Wide +1-408-414-9760 Figure 2. Efficiency vs. input voltage. Figure 3. No-load input power vs. input voltage. 101% 100% 99% 0 20 40 60 80 100 Output Current (mA) P I- 2 7 8 3 -0 8 1 3 0 1 265 VAC 85 VAC N o rm a liz e d O u tp u t V o lt a g e 300 250 200 100 150 50 0 85 115 145 175 205 235 265 Input Voltage (VAC) P I- 2 7 8 2 -0 8 1 3 0 1 In p u t P o w e r (m W ) 90% 70% 80% 50% 60% 30% 40% 10% 20% 0% 85 115 145 175 205 235 265 Input Voltage (VAC) E ff ic ie n cy P I- 2 7 8 1 -0 8 1 3 0 1 Part No. I O_MAX 85-265 VAC 85-132 VAC L MIN_SOA L MIN_SOA TNY264 115 mA 820 µH 470 µH TNY266 162 mA 680 µH 330 µH TNY267 210 mA 560 µH 330 µH TNY268 256 mA 470 µH 220 µH L P V V V I f V VMIN PWR O ACMAX DS O LIMIT MIN SW MIN ACMAX DS _ _ _ ≥ ⋅ ⋅ ⋅ − −( ) ⋅ ⋅ ⋅ −( ) 2 2 22