® Design Idea DI-41 ® TOPSwitch-GX 43 W, 100/115 VAC Multi-output Set-top Box Power Supply Application Device Power Output Input Voltage Output Voltage Topology Set-top Box TOP247Y 43 W cont. / 57 W pk 90-132 VAC 3.3 V, 5 V, 12 V, 18 V, 33 V Flyback Design Highlights Operation • Low cost, low component count solution • Excellent output voltage tracking and cross-regulation - no linear regulators required • High efficiency, >71% at 90 VAC • Line undervoltage detection (UV) and power system surge protection (OV) • Meets CISPR22B/EN55022B conducted EMI limits • Differential and common mode surge immunity to 4 kV (EN61000-4-5) • 100 kHz ring wave immunity to 4 kV (IEEE C62.41) The design in Figure 1 utilizes the TOP247Y and takes advantage of many of the TOPSwitch-GX features. Line UV and OV (100 V and 450 V, respectively) are implemented using a single 2 MΩ resistor (R1). Undervoltage eliminates output glitches and overvoltage provides protection for both short duration transients and long duration power system surges. Resistor R4 programs the internal current limit of U1 to 80% of nominal, limiting overload power. T1 R6 10 Ω 14 D7 UF4003 L7 Bead 8 C24 R15 0.1 µF 10 Ω 50 V C5 R2 68 kΩ 1 nF 2 W 1 kV C6 2.2 nF Y1 D10 BYV32-200 1 VR1 P6KE200 D2 3, 4 D1 C13, C14 1200 µF 35 V D11 MBR1045 C22 0.1 µF 50 V C16, 17 1200 µF 35 V 18 V, 0.5 A 12 V, 0.6 A/1.8 A pk C12 100 µF 25 V 11 10 C10 220 µF 25 V L3 3.3 µH, 5 A C11 390 µF 35 V 9 D1-D4 RL206 2 A, 800 V 33 V, 0.03 A C8 10 µF 50 V L2 3.3 µH, 5 A C9 1000 µF 25 V D9 UF5402 12 L6 33 µH, 0.2 A C7 47 µF 50 V D8 UF5402 13 The key performance characteristic of the circuit shown is the excellent output voltage tracking and cross-regulation. Two techniques are used to properly center the output voltages. The extra voltage drop of the ultra-fast rectifier D10 (used instead of a Schottky) centers the 5 V output at precisely 5 V R14 5.6 kΩ 0.5 W L4 3.3 µH 5A 5 V, 3.2 A L5 C15 3.3 µH 220 µF 5A 16 V 3.3 V, 3 A C18 220 µF 16 V RTN D5 1N4937 D4 D3 L1 20 mH 1.3 A C1 0.22 µF X2 t° 90 - 132 VAC 7 D RT1 10 Ω 3.2 A L D6 1N4148 S X 6 C3 1 µF 50 V F R8 1 kΩ C19 0.1 µF 50 V R10 9.53 kΩ 1% R12 18 kΩ R13 15 kΩ 1% C C3 0.1 µF 50 V R3 6.8 Ω C20 22 µF 50 V C5 47 µF 16 V N Figure 1. TOPSwitch-GX 43 W Continuous, 57 W Peak Set-Top Box Power Supply. DI-41 C21 0.1 µF 50 V U2 LTV817 TOPSwitch-GX CONTROL U1 TOP247Y R4 9.09 k 1% R7 150 Ω 5 R1 2 MΩ 1/2 W RV1 275 V 14 mm F1 3.15 A L C2 150 µF 200 V www.powerint.com R9 3.3 kΩ U3 TL431CLP R11 10 kΩ 1% PI-3389-091702 September 2002 DI-41 and DC stacking is used to improve the regulation of 12 V, 18 V, and 30 V outputs. Ferrite bead L7 is placed in series with the 12 V, 18 V and 30 V output windings to improve centering and cross-regulation of these outputs. TRANSFORMER PARAMETERS Core Material ERL28, Nippon ceramic NC-2H material or equivalent, gapped for ALG = 128 nH/T2 Bobbin ERL28 vertical, 14 pins, Jinbo Industrial JB-0039 or equivalent Winding Details Primary: 30T + 23T, 25 AWG Shield: 1T, 0.6" x 0.001" Cu foil Bias: 7T, 2 x 27 AWG 3.3 V: 2T, 0.6" x 0.005" Cu foil 5 V: 1T, 0.6" x 0.005" Cu foil 12 V: 4T, 2 x 27 AWG 18 V: 3T, 2 x 27 AWG 33 V: 6T, 27 AWG (2 x 27 AWG = Bifilar 27 AWG) Winding Order (Pin Numbers) Apply 3.2 mm tape margin to both sides of bobbin Primary (4-3), tape, Shield (1-NC), tape, Bias (6-7), 3 x tape, 5 V (9-11), 3.3 V (11-10), tape, 12 V (12-8), 18 V (13-12), 33 V (14-13), 3 x tape, Primary (3-1), 3 x tape Inductance Primary: 356 µH, Leakage: 11 µH (maximum) Primary Resonant Frequency 650 kHz (minimum) Frequency jittering provides large EMI margins with simple filtering. Primary soft-start minimizes component stress during start-up and a soft-finish capacitor (C20) eliminates start-up output overshoot. Key Design Points • Use KRP (Ripple-to-peak current ratio) in the range of 0.4–0.6 for higher efficiency, and tighter cross-regulation. Use VOR (reflected output voltage) of 90 V to 110 V for optimum performance. • PCB traces which carry high switching currents should be short and wide to reduce EMI. • Reduce leakage inductance and improve cross-regulation by filling each winding layer across the entire width of the bobbin. • Resistor R14 provides a small amount of pre-load on the 33 V output to prevent peak charging due to leakage spikes. • R5 and C5 reduce power dissipation in VR1. Voltage Load (V) 3.3 5 12 30 Range (Amp) -8 -7 -6 1-3 1-3.2 0.3-0.6 0.01-0.03 Regulation (%) -5 -4 -3 -2 -1 0 Table 1. Transformer Design Parameters. 1 2 3 Table 2. Worst Case Output Cross Regulation - Outputs Taken from Minimum to Maximum Load and Line from 85 VAC to 132 VAC. 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. ©Copyright 2002, Power Integrations, Inc. WORLD HEADQUARTERS AMERICAS Power Integrations, Inc. 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