Design Idea DI-129 PeakSwitch 33 W (60 W Peak) PVR Power Supply Application Device Power Output Input Voltage Output Voltage Topology PVR PKS606P 33 W (60 W Pk) 195-265 VAC 3.3 V, 5 V, 17.5 V, 22 V Flyback Design Highlights • • • • • their set-point thresholds, U2 pulls additional current through the LED in U5. This in turn increases the base drive to Q1, increasing the current pulled out of the EN/UV pin of U6. Switching cycles are skipped once the EN/UV disable threshold current is exceeded. When the current out of the EN/UV pin falls below the disable threshold, switching cycles are re-enabled. Small, low-cost EF25 core size delivers 60 W peak Low component count: only 47 parts High efficiency: ≥76% at 33 W No-load power consumption <140 mW Meets EN55022 B conducted EMI limits Operation A bias winding (T1, pins 4 and 5) on the transformer is rectified and filtered by D15 and C21, and supplies operating current to U6, through R14. The frequency jitter function within U6 and a Y-type capacitor (C10) across T1 reduce the generation of conducted EMI so that a single common mode choke (L5) and a small X-capacitor (C13) allow the supply meet EN55022B limits with 6 dBµV or more of margin. A combination RCD-Zener clamp (R2, R15 C9, D10 and VR2) limits the peak drain-node voltage to below the 700 V rating of the MOSFET integrated within U6. The flyback converter shown in Figure 1 uses a member of the PeakSwitch family (U6, a PKS606P) to supply 33 W continuously and peak power pulses of up to 60 W. The controller in U6 receives feedback from the secondary through U5, and based on that feedback, enables or disables the switching of its integrated MOSFET to maintain regulation. A portion of both the 3.3 V and the 5 V outputs are fed into the TL431 (U2), which controls the current through the LED in U5. As the 3.3 V or the 5 V output voltages rise above C10 2.2 nF 1 kV VR2 1N4764A 100 V D5 1N4007 F1 2A D6 1N4007 1 C20 33 µF 400 V L5 19 mH 2 D10 FR106 C21 47 µF 35 V RV1 275 VAC R14 4.7 kΩ PeakSwitch U6 D PKS606P EN/UV BP S C16 2200 µF 16 V D9 STPS3150 D15 1N4148 8 D2 SB530 5 10 C17 2200 µF 16 V D3 1N4007 C12 220 nF 50 V C8 220 µF 10 V L3 3.3 µH L4 3.3 µH R13 15 Ω 1W EF25 U5B PC817D Q1 2N3904 C18 100 µF 50 V D13 1N4148 C22 100 nF 50 V D16 1N4148 R16 1 kΩ C2 10 µF 50 V RTN VR1 1N4733A 5.1 V R11 R10 3.92 kΩ 150 Ω 1% +17.5 V 670 mA +3.3 V 1.74 A 9 4 +22 V 360 mA +5 V 1.6 A C6 220 µF 10 V D7 SB520 R17 22 Ω D4 1N4007 C15 220 µF 35 V C14 150 µF 35 V 7 3 R2 22 Ω 1/2 W C13 100 nF 275 VAC 6 D8 STPS3150 C9 2.2 nF 1 kV R15 10 kΩ 1/2 W T1 R12 56.2 kΩ 1% -5 V 28 mA C11 100 nF 50 V R9 3.3 kΩ U5A PC817D U2 LM431A 2% R8 10 kΩ 1% PI-4522-110906 Figure 1. Circuit Diagram of a 33 W Continuous, 60 W Peak, PVR Power Supply. DI-129 November 2006 DI-89 DI-129 Resistor R16 provides the bias current for U2. Resistor R10 sets the gain. Capacitor C22 improves transient responsiveness. Capacitor C11 and resistor R9 roll off the high frequency gain of U2. Capacitor C2 performs a soft-finish function that prevents the 3.3 V and the 5 V output voltages from overshooting their regulation set points during the initial power up of the converter. 85 Efficiency (%) Key Design Points PI-4527-110706 95 All output windings are AC stacked and exhibit good cross regulation, due to the tight coupling within transformer T1. The –5 V output uses Zener diode VR1 as a post regulator. 75 • • 65 55 45 • 35 25 195 205 215 225 235 245 255 TRANSFORMER PARAMETERS Core Material PC40EF25-Z or equivalent Figure 2. Efficiency vs. Input Line Voltage at Full Load, Room Temperature, 50 Hz Line. Bobbin PI-4528-110906 110 105 All secondary winding should be wound in layers right next to each other, in order to assure the best cross regulation. Use foil for 3.3 V and 5 V secondary windings for the best cross regulation. The reflected output voltage (VOR) was set at 126 V to ensure good output voltages cross regulation. If tighter cross regulation is needed, a lower value of VOR could be used at the expense of reduced peak power delivery. The configuration of U5, Q1, R17 and D6 increases the speed of U5 and reduces pulse grouping. 265 AC Input Voltage Regulation (%) • 100 1/2 Primary: 32T, 31 AWG Bias: 9T, 0.45 mm Winding Details Secondary: Foil 2T, Foil 1T, 6T, 0.45 mm × 2 & 3T 0.25 mm 1/2 Primary: 32T, 31 AWG Winding Order (pin numbers) 95 90 Primary Inductance 3.3 V 5V -5 V 22 V 17.5 V 85 EF25 Horizontal Primary (3-2), Bias (5-4), Secondary (9-10, 10-8, 7-8, 6-7), Primary (2-1) 342 µH, ±10% Table 1. Transformer Design Parameters. TIW = Triple Insulated Wire, NC = No Connect, FL = Flying Lead 80 190 200 210 220 230 240 250 260 270 AC Input Voltage (VAC) Figure 3. Output Regulation vs. Input Line Voltage, Room Temperature, Full Load. 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Power Integrations 5245 Hellyer Avenue San Jose, CA 95138 Phone: 1-408-414-9200 Apps: 1-408-414-9660 Apps Fax: 1-408-414-9760 The PI logo, TOPSwitch, TinySwitch, LinkSwitch, DPA-Switch, PeakSwitch, EcoSmart, Clampless, E-Shield, Filterfuse, StackFET, PI Expert and PI FACTS are trademarks of Power Integrations, Inc. Other trademarks are property of their respective companies. ©Copyright 2006, Power Integrations, Inc. For a complete listing of worldwide sales offices, please visit www.powerint.com Rev. A 11/06