DN05064/D Design Note – DN05064/D Universal AC Input, 5 Volt Output, 10 Watt Power Supply Device Application Input Voltage Output Power Topology I/O Isolation NCP1124 NCP431 Smart Meters, Electric Meters, White Goods 85 to 265 Vac 10W CCM Flyback Isolated ( 3 kV) Output Specification Output Voltage Ripple Nominal Current Max Current Min Current 5 Vdc nominal 100 mV p/p @ full load 2 Amps continuous 2.2 A maximum zero PFC (Yes/No) Input Protection Operating Temp. Range No(Pout ≤ 10 watts) Fuse 0 to +50°C Cooling Method Convection Standby Power 30 mW at 115 Vac 80 mW at 230 Vac Circuit Description This design note describes a simple 10 watt, universal AC input, constant output voltage power supply intended for AC adapters, industrial equipment, or white goods, where isolation from the AC mains is required, and low cost, high efficiency, and low standby power are essential. Performance characteristics for efficiency, output ripple, and internal MOSFET drain switching characteristics (Vds, Id) are shown in the figures and plots below. Enhanced input transient protection (lightning, etc.) can be accomplished with the addition of an appropriate TVS device across the input of the diode bridge. . The featured power supply is a simple CCM flyback topology utilizing ON Semiconductor’s new NCP1124 monolithic with with integral 9ohm, vertical channel MOSFET in a PDIP7 package (U1). This Design Note provides the complete circuit schematic details and BOM for 5V, 2A power supply. The simple input EMI filter (C1, L1) is adequate to pass Level B for FCC conducted EMI compliance. The NCP431 programmable zener is used as an error amplifier (U3), plus an optocoupler feedback scheme (U2) provides for excellent line and load regulation with high input-to-output safety isolation. April 2014, Rev. 0 Key Features Universal AC input range (85 – 265 Vac). Input filter for conducted EMI attenuation. 650V Avalanche rated MOSFET. Input filter for conducted EMI attenuation. Very low standby (no load) power consumption. Frequency foldback under light load. Inherent over-current, over-voltage and over temperature protection. www.onsemi.com 1 DN05064/D For optimum thermal characteristics, the printed circuit board should be laid out to include clad “pours” around pins 5 and 6 of the DIP8 package (MOSFET drain pins). Resistors 9 sets the peak current limit point for the internal overcurrent protection circuit of U1 and can be adjusted for desired max output current. For output voltages other than 5 volts, typical circuit changes include the transformer turns ratio for both the secondary and the primary aux winding, the value of R17 in the output voltage sense divider, and selecting appropriate voltage ratings for output rectifier D8 and output capacitors C9A, B & C. Depending on the transformer aux winding characteristics, it may be necessary to change R11 to a higher value resistance value to adjust the nominal Vcc voltage. Z1 can be added as an option in the event that the compliance range of the Vcc over the output load range exceeds the OVP trip point on pin 1 of U1 (28 volts). Such a scenario would be the result of a transformer with high leakage inductance. Circuit Schematic NCP1124 06 R9 0 6W 10k NOTES: 1. Crossed lines on schematic are NOT connected. 2. U2 is NEC PS2561L-1 or equivalent optocoupler(CTR>50%). 3. R1 is optional for increased inrush limiting- use wire wound only. 4. L1A/L1B are Wurth #7447728215 inductors (820uH, 500mA). 5. Output caps(C9A/B/C) are radial lead, low impedance types(UCC LXV series or similar). 6. R11 is for Vcc trimming(<28Vmax), typically zero ohms. 7. R9A/B sets max output current. 8. Heavy schematic lines indicate recommended ground plane areas. 10 Watt NCP 1124 Power Supply With Universal AC Input Circuits Optimized for 650V 9𝛀MOSFET (compared to MOSFET NCP1126/NCP1129) A single 0.6 W, 1.5Ω resistor with 1% tolerance is used to limit the maximum current flowing through the MOSFET, instead of paralleling two 1.8Ω,1/2W resistors with 5% tolerance. April 2014, Rev. 0 www.onsemi.com 2 DN05064/D T1 Transformer Designs (Available from ICE Components Inc. and Wurth Electronics) 5V/2A, 65 kHz Version (ICE # TO0915-1, Wurth Electronics #750313860 Rev 01) Core: E25/10/6 (812E250) Primary A: 55 turns of 0.25mm mag wire 5V Secondary: 11 turns bifilar of 0.6mm Triple Insulated Wire (2 layers) Aux/Vcc: 25 turns of 0.15mm mag wire spiral wound over 1 layer Primary B: 55 turns of 0.25mm mag wire Primary Inductance (Pri A and B in series): 2 mH +/- 10% (gap in center leg) Leakage Inductance (5Vsec & Aux shorted): 40 uH max 5 Volt Efficiency vs Output Load Curves 0.81 0.8 0.79 0.78 115Vac 0.77 230Vac 0.76 0.75 0.74 0.73 0.5 1 1.5 2 Board Picture April 2014, Rev. 0 www.onsemi.com 3 DN05064/D Full Load Output Ripple @ 120 Vac Input 10mV/div, 12.5us/div MOSFET Drain Voltage (120 Vac Input) Full Load 100V/div, 10us/div April 2014, Rev. 0 www.onsemi.com 4 DN05064/D 0.5 Amp Load 100V/div ,10us/div Mosfet Drain Current (120 Vac Input) Full Load 600mV/div ,10us/div 0.5 Amp Load 600mV/div 10us/div April 2014, Rev. 0 www.onsemi.com 5 DN05064/D Conducted EMI Plot dBuV 80 70 EN 55022; Class B Conducted, Average EN 55022; Class B Conducted, Quasi-Peak 60 50 40 30 20 10 1124_Demo_N_AVG 0 -10 -20 1 10 1/16/2014 10:43:19 AM April 2014, Rev. 0 (Start = 0.15, Stop = 30.00) MHz www.onsemi.com 6 DN05064/D Bill of Materials April 2014, Rev. 0 www.onsemi.com 7 DN05064/D References ON Semiconductor data sheet for NCP1126, 1129 monolithic switcher. ON Semiconductor Design Notes DN05012, DN05017, DN05018, DN05028, DN05029, DN05043/D ON Semiconductor Application Note AND8489 1 © 2014 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 Le Du, e-mail: [email protected] Frank Cathell email: [email protected] April 2014, Rev. 0 www.onsemi.com 8