Design Idea DI-13 ® TinySwitch-II ® 3 W Universal Adapter Application Device Power Output Input Voltage Output Voltage Topology 3 W Adapter TNY264 3W 85-265 VAC 9V Flyback Design Highlights This 3 W single output, universal input power supply is available as a Design Accelerator Kit (DAK-14) including samples and documentation. With 71% minimum efficiency at full load, compliance to CISPR22 Class B, small size, and low parts count, the DAK-14 showcases the significant advantages of TinySwitch-II in low power adapter applications. • No-load consumption less than 250 mW at 230 VAC • Compact design: 2.0” x 1.2” x 0.75” • Minimum parts count and single sided PC board ensures cost-effective solution • High frequency operation allows compact EF12.6 transformer • Enhanced ON/OFF control allows simple Zener reference and eliminates the need for loop compensation • Built-in circuitry practically eliminates audible noise with standard varnished transformer • No-load regulation achieved without pre-load resistor • Well defined frequency jitter feature reduces EMI–simple input π filter meets CISPR22 Class B/EN55022B • Self-protecting hysteretic thermal shutdown: power supply automatically recovers when fault is removed Operation The digital ON/OFF control scheme of TinySwitch-II allows tight regulation using a low cost secondary Zener reference and eliminates the need for loop compensation. In addition, no preload is required to maintain regulation at light load, helping to reduce measured no-load consumption to <250 mW at 265 VAC – see Figure 3. TinySwitch-II also provides autorestart to reduce output overload current during fault conditions. C5 2200 pF Y1 2 10T x2 D1 & D3 1N4007 C3 2.2 nF 1 kV R4 330 kΩ 1/2 W 1 96T 33 AWG 8 10T 28 AWG 5 D6 11DQ06 L2 Bead 9 V, 330 mA C9 220 µF 25 V C6 330 µF 16 V RTN 3 RF1 L 8.2 Ω C1 & C2 4.7 µF 400 V 85-265 VAC N D D1 & D4 1N4007 R2 4.7 kΩ 1/8 W VR2 BZX79-B8V2 D5 1N4937 U1 TNY264P BP U2 LTV817A S TinySwitch-II L1 1 mH EN/UV C4 0.1 µF PI-3074-091402 Figure 1. TinySwitch-II 3 W Universal Adapter. DI-13 www.powerint.com September 2002 DI-13 76% Efficiency (%) • Design transformer for low leakage inductance. • Varnish transformer to practically eliminate acoustic noise - gluing not required. • Maximum flux density of main transformer should be no more than 3000 gauss. • Use primary RCD clamp that allows no more than 600 V across the TinySwitch-II DRAIN and SOURCE pins. • Provide adequate copper area on PCB at the connection to the TinySwitch-II SOURCE pin, for heatsinking. PI-3075-080902 78% Key Design Points 74% 72% 70% 68% 85 Transformer Parameters 135 185 235 285 Input Voltage (VAC) Bobbin: Hical EF 12.6, 8 pin Winding Order Primary (3-1) Shield winding (1-2) Secondary (8-5) Primary Inductance 1.25 mH Primary Resonant 700 kHz (min) Leakage Inductance (all secondary windings shorted) 50 µH Table 1. Transformer Construction Information. 250 PI-3374-091402 Bobbin Figure 2. Efficiency vs. Input Voltage. Power Consumption (mW) Core Material Core: EF 12.6, gapped for AL of 135 nH/T2 200 150 100 50 0 75 95 115 135 155 175 195 215 235 255 275 Input Voltage (VAC) Figure 3. Efficiency vs. Input Voltage. 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. 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