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| Design Idea DI-28 (R) TinySwitch-II 3 W Charger: <30 mW No-load Consumption Application Charger Device TNY264P Power Output 3W Input Voltage 85-265 VAC Output Voltage 5 V, 600 mA Flyback (R) Topology Design Highlights * Less than 30 mW no-load power consumption (for 115/230 VAC input) * Meets CISPR-22 Class B without Y capacitor * Low cost, low component count solution the internal current source at no-load. Other load conditions are not important as the device will be powered from the DRAIN pin if bias is lost, allowing a simple flyback winding to be used. Figure 2 shows that the bias winding and choice of R2 should provide approximately 550 A at no-load to minimize consumption. The circuit meets CISPR-22 Class B conducted EMI limits without a Y capacitor and therefore has very low AC leakage current. TinySwitch-II frequency jitter, use of the bias winding as a shield and capacitor C3 to soften leakage inductance spikes combine to provide the EMI performance. Operation The TinySwitch-II flyback converter in Figure 1 generates a constant voltage, constant current (CV/CC) 5 V, 600 mA output. Typical applications include wall-mounted chargers for cell phones, PDAs and other battery powered portable equipment. The key performance characteristic of the circuit shown is the extremely low no-load consumption of <30 mW. A linear transformer charger of similar rating will typically consume 1 W to 4 W at no-load. At $0.12/kWh, the TinySwitch-II can therefore reduce energy costs by $1 to $4 per year. The no-load performance is achieved by using a transformer bias winding as a low voltage source for TinySwitch-II operating current. Even without this winding, a TinySwitch-II circuit will consume <300 mW at no-load. However, by providing external bias, the internal high voltage current source, which normally powers the IC from the DRAIN pin, is disabled and a further reduction in consumption is therefore achieved. The bias winding should provide enough current to fully disable 1 L1 1.0 mH D1 1N4005 D2 1N4005 VR1 BZY97C200 D5 1N4937 C3 2.2 nF 1 kV 105T 33 AWG 2 8 Key Design Points * Design bias winding circuit to provide approximately 550 A at no-load. Figure 2 shows the details. * Minimize secondary circuit bias currents. Use low current feedback Zeners for best tolerance. The very low bias current in this design will provide approximately 10% output voltage tolerance. A precision reference (e.g. TL431) can be used to reduce this if required. * Design transformer with low reflected voltage to minimize clamp losses. A bigger device (TNY266) may help to further reduce VOR. * Wind transformer for lowest leakage inductance. Choose wire gauges to completely fill winding layers. * Winding transformer with tape between primary layers further reduces intra-winding capacitance and no-load consumption. D7 11DQ06 C6 470 F 10 V L3 Ferrite Bead +5 VDC 8T 24 AWG 7 D6 1N4148 3 R3 1.5 k RF1 8.2 1.0 W L 85 - 265 VAC 13T x2 C5 31 AWG 47 F 16 V 4 R2 5.1 k Q1 2N3906 C7 100 F 10 V C1 4.7 F 400 V C2 4.7 F 400 V TinySwitch-II U1 TNY264P D EN BP N R4 820 VR3 BZX79B5V1 D3 1N4005 D4 1N4005 U2 C4 0.1 F 50 V U2 PC817A R5 2.7 2W RTN L2 Bead 2.2 H S Figure 1. TinySwitch-II 3.0 W Cell Phone Charger. DI-28 PI-3079-091402 www.powerint.com September 2002 DI-28 PI-3298-091402 PI-3081-090402 80 70 30 25 20 15 10 5 0 No Load Consumption 60 50 40 30 20 10 0 300 115 VAC 230 VAC No Load Consumption 400 500 600 700 800 900 85 110 135 160 185 210 235 260 BYPASS Pin Current (A) Input Voltage (VAC) Figure 3. No-load Input Power vs. Line Voltage. Figure 2. No-load Input Power vs. BYPASS Pin Current. PI-3080-091402 6 5 4 3 2 1 0 0 TRANSFORMER PARAMETERS Core Material EE13 TDK PC40, or equivalent AL of 128 nH/T2 EE13, 8 pin Primary (1-2), tape, Bias (3-4), tape, Secondary (7-8), 5 V, tape 1.9 mH 10% 500 kHz (minimum) 50 H (maximum) Output Voltage (VDC) 115 VAC 230 VAC Bobbin Winding Order (pin numbers) Primary Inductance Primary Resonant Frequency 100 200 300 400 500 600 700 Leakage Inductance Output Current (mA) Figure 4. 5.0 VDC, 600 mA CV/CC Curve. Table 1. Transformer Construction Information. 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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