Design Idea DI-84 ® TinySwitch-II 3 W Charger: <30 mW No-load Consumption Application Device Power Output Input Voltage Output Voltage Topology Charger TNY264P 3W 85-265 VAC 5 V, 600 mA Flyback Design Highlights The bias winding should provide enough current to fully disable 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. This allows a simple flyback winding to be used. Figure 2 shows that the bias winding and choice of R2 should provide approximately 600 µA at no-load to minimize consumption. • 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 • Meets CEC active mode efficiency with good margin Operation The circuit meets CISPR-22 Class B conducted EMI limits without a Y capacitor, and therefore has very low AC leakage current. Superior EMI performance is achieved via the TinySwitch-II frequency jitter, an output RC snubber, use of the bias winding as a shield, and careful selection of clamp Zener voltage. 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. Key Design Points 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. • Design bias winding circuit to provide approximately 600 µA at no-load. Figure 2 shows the details. • Minimize secondary circuit bias currents. Use low current feedback Zeners for best tolerance. The very low Zener bias current in this design will provide better than ±10% output voltage tolerance. • Design transformer with low reflected voltage to minimize clamp losses. A larger device (TNY266) may enable further reduction in VOR. • Wind transformer for lowest leakage inductance. Choose wire gauges to completely fill winding layers. This 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. The bias winding disables the internal high voltage current source, which normally powers the IC from the DRAIN pin, thereby further reducing power consumption. R6 33 Ω T1 T1 EE13 LP = 1.9 mH 1 L1 1.0 mH L RF1 8.2 Ω 1.0 W D1 1N4005 D2 1N4005 D5 1N4007G Fusible C1 4.7 µF 400V 85 - 265 VAC 8T 24 AWG T.I. 3 2 R1 200 Ω 1/2 W 4 15T 32 AWG C5 47 µF 16 V D6 1N4148 C2 4.7 µF 400V D U1 TNY264P TinySwitch-II N 7 D4 1N4005 L2 Ferrite Bead 5 V, 0.6 A C6 470 µF 10 V R3 1.5 kΩ R2 9.2 kΩ Q1 2N3906 C7 100 µF 10V EN/UV BP S D3 1N4005 C4 0.1 µF 50 V U2 PC817A Figure 1. TinySwitch-II 3.0 W Cell Phone Charger. DI-84 L3 Ferrite Bead D7 11DQ06 8 VR1 BZY97C130 102T 32 AWG C3 470 pF 100V www.powerint.com R4 820 Ω R5 2.4 Ω 2W VR2 BZX79B5V1 RTN PI-3659-060205 June 2005 DI-84 • Winding transformer with tape between primary layers further reduces intra-winding capacitance and no-load consumption. 115 VAC 230 VAC 50 40 30 20 10 0 300 PI-4013-060205 60 No Load Consumption (mW) 70 No Load Consumption 35 PI-3298-091402 80 33 31 29 27 25 23 21 19 17 15 400 500 600 700 800 85 105 125 145 165 185 205 225 245 265 900 Input Voltage (VAC) BYPASS Pin Current (µA) Figure 2. No-load Input Power vs. BYPASS Pin Current. PI-3684-082603 Output Voltage (VDC) 6 5 4 Figure 3. No-load Input Power vs. Line Voltage. TRANSFORMER PARAMETERS Core Material 115 VAC 230 VAC 3 2 Bobbin 1 Primary Inductance 0 0 EE13, 8 pin Winding Order (pin numbers) Limits for Output Voltage and Current 100 200 300 400 500 600 700 EE13 TDK PC40, or equivalent AL of 128 nH/T2 Primary: 1-2, tape, Bias: 3-4, tape, Secondary: 7-8, 5 V, tape 1.9 mH ±10% Primary Resonant 500 kHz (min) Frequency Output Current (mA) Leakage Inductance Figure 4. 5.0 VDC, 600 mA CV/CC Curve. 50 µH (max) Table 1. Transformer Construction Information. For the latest updates, visit 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. POWER INTEGRATIONS MAKES NO WARRANTY HEREIN AND SPECIFICALLY DISCLAIMS ALL WARRANTIES INCLUDING, WITHOUT LIMITATIONS, THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND NON-INFRINGEMENT OF THIRD PARTY RIGHTS. The products and applications illustrated herein (transformer construction and circuits external to the products) 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. Power Integrations grants its customers a license under certain patent rights as set forth at http://www.powerint.com/ip.htm. The PI logo, TOPSwitch, TinySwitch, LinkSwitch, DPA-Switch, EcoSmart, PI Expert and PI FACTS are trademarks of Power Integrations. Copyright 2005, Power Integrations Power Integrations MAIN PHONE NUMBER +1 408-414-9200 A 6/05 5245 Hellyer Avenue APPLICATIONS HOTLINE +1 408-414-9660 APPLICATIONS FAX +1 408-414-9760 www.powerint.com San Jose, California 95138 For a complete listing of worldwide sales offices, please visit www.powerint.com