DN06008/D Design Note – DN06008/D +/- 18 V, Dual Output Power Supply Device NCP1308 Application Input Voltage Audio Amp Power Supply +/-18V 90 to 270 Vac Output Power Topology I/O Isolation 45 W, 90 W peak Quasi Resonant Flyback Yes Other Specifications Output Voltage Ripple Nominal Current Max Current Min Current Others Output 1 Output 2 Output 3 Output 4 +18 V <100 mV 1.25 A 2.5 A zero - 18 V <100 mV 1.25 A 2.5 A zero N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A PFC (Yes/No) No Minimum Efficiency 75% Input Connector / Fuse 2 A fuse Operating Temp. Range Cooling Method/Supply Orientation 0 to +50°C Convection Tracking dual outputs Circuit Description Key Features A low cost 45 watt nominal, 90 watt peak, dual +/- 18 volt output power supply is presented here for powering audio amplifiers or similar applications. Because the sum of the outputs are sensed, good voltage regulation and tracking is provided despite the extremely simple zener and optocoupler voltage feedback circuit. The off-line power converter is implemented utilizing ON’s NCP1218 quasi-resonant (QR) flyback controller. This topology provides very high conversion efficiency and low noise generation because of the QR, zero voltage switching properties and the fact that the flyback switching operation is achieved in the discontinuous inductor current, critical conduction mode. The input circuit features common and differential mode conducted EMI filtering using off-the-shelf components. An auxiliary Vcc winding on the flyback transformer also provides for very low input standby power (less than 1 W) under no load conditions. Dual, tracking +/- 18 volt outputs. Very low cost, simple off-line power supply circuit. Quasi-resonant, critical conduction mode flyback topology for maximum efficiency. Input conducted EMI filter. Low output ripple (< 100 mV) NTC thermistor inrush limiting Very low EMI noise generation Inherent over-current and over-voltage protection August 2006, Rev. 0 www.onsemi.com 1 DN06008/D Schematic F1 AC Input 2A 250Vac C1 0.22uF "X2" 0.22uF "X2" L1 TH1 C5 220uF 400V T1 1 13 D2 MBR1100 R1 T Gnd BD1 C2 C6 270pF 2kV R2 120, 5W Q1 10 ohm 1.5A Chassis Gnd C3 C4 1Meg 0.5W R6 15K 2.2nF "Y2" x2 R5 R4 4.7 10K 9 R3 0.27 1W C11 C12 NCP1308 5 8 6 R8 27K 1 2 C8 1nF 4 D1 1N4148 3 C9 47uF 16V R9 1K C15 R7 100 L2 R10 C16 2.7K C17 100uF 25V 6 11 D3 2,200uF MBR1100 25V x 2 3 4 3 U2 68 1 L3 4.7uH D4 1N5258B (36V) R11 C10 100pF C7 10nF +18V 4.7uH C13 100uF 25V 4 7 U1 NOTES: 2,200uF 25V x 2 R12 220 C14 0.1uF 50V Com C18 0.1 -18V C19 0.1uF 50V Optional Chassis Gnd 2 1. Crossed lines on schematic are NOT connected. 2. Q1 is Infineon SP8N80C3 (8 amp, 800 volt) 3. U2 is Vishay H11A817A or equivalent optocoupler. 4. TH1 is NTC thermistor for inrush limiting. 5. L1 is Coilcraft BU15-7521R0BL EMI inductor. 6. L2 & L3 are Coilcraft PCV-0-472-05L (4.5uH, 5A) 7. Q1 will need a small heatsink. 8. BD1 can be 4 - 1N4005 rectifiers (ON Semi). 9. D1, D2, D3, D4, U1 are ON Semiconductor components 10. Output caps are radial lead, low impedance types (UCC LXV series or similar). 11. See drawing for T1 details. Suggested proto vendor is Mesa Power Systems, Escondido, CA (800-515-8514) 90 Watt Peak, Dual Output Quasi-Resonant Power Supply ON Semiconductor Design Center August 2006, Rev. 0 www.onsemi.com 2 DN06008/D 1 MAGNETICS DESIGN DATA SHEET Project : Dual output +/-18V, 45 watt (90 W peak) audio amplifier power supply Part Description: Quasi-resonant flyback transformer, 100W pk , 2 output Schematic ID: T1 Core Type: ETD29 (Ferroxcube 3C90 material or equivalent) Core Gap: Gap for 400 uH +/- 5% Inductance: 380 to 420 uH nominal across primary (pins 13 to 1) Bobbin Type: ETD 13 pin horizontal pc mount (Ferroxcube PC1-29H) Windings (in order): Winding # / type Turns / Material / Gauge / Insulation Data Aux winding (11 - 3) 7 turns of # 24HN spiral wound evenly over primary. Self-leads to pins. Insulate for 1 kV to next winding. Primary (13 - 1) 63 turns of #30HN over one layer; cuff ends with tape; Self-leads to pins; insulate for 3 kV to next layer. +/- 18V secondary (9 - 4, 7 - 6) 10 turns bifilar (2 strands) of #26HN with 1 strand a different color, flat wound over 1 layer with 0.20" end margins. Self-leads to pins with similar colors to same pin (see drawing below). Hipot: 2.7 kV primary/aux to all secondaries. Vacuum varnish. Schematic Lead Breakout / Pinout Bottom (pin side) view 1 Pri 13 Aux 11 3 1 2 3 4 5 6 9 +18V 4 7 6 Bifilar Wound -18V 13 12 11 10 9 8 7 1 © 2006 ON Semiconductor. Disclaimer: ON Semiconductor is providing this design note “AS IS” and does not assume any liability arising from its use; nor does ON Semiconductor convey any license to its or any third party’s intellectual property rights. This document is provided only to assist customers in evaluation of the referenced circuit implementation and the recipient assumes all liability and risk associated with its use, including, but not limited to, compliance with all regulatory standards. ON Semiconductor may change any of its products at any time, without notice. Design note created by: Frank Cathell, e-mail: [email protected] August 2006, Rev. 0 www.onsemi.com 3