DN05018/D Universal AC Input, 12 V Output, 10 W E‐meter Power Supply www.onsemi.com DESIGN NOTE Table 1. DEVICE DETAILS Device Application Input Voltage Output Power Topology I/O Isolation NCP1075, NCP431 Smart Meters, Electric Meters, White Goods 85 to 300 Vac 5 to 10 W Flyback Isolated (3 kV) Characteristic Output Specification Output Voltage 12 Vdc Ripple 150 mV p/p @ Full Load Nominal Current 800 mA Max Current 1.0 A Maximum Min Current Zero PFC (Yes/No) No, (Pout < 25 W) Efficiency 77% per Energy Star Inrush Limiting/Fuse Inrush Resistor (R1) & Fuse Operating Temp. Range 0 to +50°C Cooling Method/Supply Orientation Convection Signal Level Control None Circuit Description Performance characteristics for efficiency, output ripple, and internal MOSFET drain switching characteristics 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 C2. This design note describes a simple, low power (10 W or less), universal AC input, constant voltage power supply intended for powering utility electric meters or similar industrial equipment or white goods where isolation from the AC mains is required and low cost and high efficiency is essential. The featured power supply is a simple flyback topology utilizing ON Semiconductor’s new NCP1075 SOT−223 monolithic switcher. This Design Note provides the complete circuit schematic details and transformer design for a 12 V, 800 mA amp power supply. Other output voltages from 3.3 Vdc up to 28 Vdc are easy to implement by modifying the values (or ratings) of a few of the secondary side output components and the flyback transformer’s secondary winding (T1). The simple input EMI filter is adequate to pass Level B for FCC conducted EMI compliance and the NCP431 plus optocoupler feedback scheme provides for excellent line and load regulation along with high input-to-output isolation. © Semiconductor Components Industries, LLC, 2015 January, 2015 − Rev. 1 Key Features • Universal AC Input Range (85–300 Vac). • Input Filter (Pi-network) for Conducted EMI • • • • 1 Attenuation and Input Transient Protection Very Low Standby (No Load) Power Consumption Frequency Foldback under Light Load and/or Over-current Conditions Secondary Circuit Easily Configured for Different Output Voltages Inherent Over-current, Over-voltage and Over-temperature Protection Publication Order Number: DN05018/D 4.7 ohms 3W R1 C1 0.1uF ”X” 1.5A F1 C2 1 mH 0.1uF ”X” L1B 1 mH L1A R2B 3.3M 3.3M R2A Primary Ground Plane www.onsemi.com 2 R4 C7 1nF 1K R3 D5 C4 1nF 1kV 4.7uF 50V D6 C6 10 MMSD 4148A R5 1N4937 68K 1/2W C8 T1 5,6 7,8 3 4 MBRS 260T3 D7 2 1 1K R7 R6 1K C10 U3 0.1uF 50V Secondary Ground Plane U2 1nF ”Y1” 2 3 4 1 10 W NCP1075 Power Supply with Universal AC Input C5 22uF 25V (100 kHz) NCP1075 1 22uF 400V U1 3 4 2 D1−D4 MRA4007 X4 C3 Notes: 1. Crossed lines on schematic are NOT connected. 2. R4 value dependent on AUX winding turns. 3. R1 is optional inrush limiting resistor. 4. U1 tab (pin 4) and D7 should have heatsinking clad pours. 5. Heavy lines indicate recommended ground plane areas. 6. L1A/L1B are Coilcraft RFB0810−102L. 7. U2 is Vishay SFH6156A−4 optocoupler or similar. AC Input J1 NCP431 10K 0.1 R10 C12 1000uF, 16V C9A C9B 10K R9 R8 39K 0.1uF 50V C11 + _ Vout J2 DN05018/D CIRCUIT SCHEMATIC DN05018/D 12 V Transformer Design Project/Customer: ON Semiconductor − NCP1075 10W PSU Part Description: 10 W Flyback Transformer, 100 kHz, 12 V/0.8 A Out Schematic ID: T1 Core Type: EF16 (E16/8/5); 3C90 Material or Similar Core Gap: Gap for 1.7 to 2 mH Inductance across Primary (Pins 1 − 4) Inductance: 1.85 mH ±5% Bobbin Type: 8 Pin Horizontal Mount for EF16 Windings (in order): Winding #/Type Turns/Material/Gauge/Insulation Data Primary (4 − 1) 100 turns of #35HN over 2 layers evenly. Insulate with a layer of Mylar tape. 12 V Secondary (7, 8 − 5, 6) 10 turns of #24 triple insulated wire over one layer. Self leads to pins per drawing. Insulate with a layer of Mylar tape. Vcc/Boost (3 − 2) 10 turns of #35HN spiral wound over 1 layer with 2 mm end margins. Insulate with tape for 3 kV. Varnish assembly Hipot: 3 kV from Vcc/primary to secondary. Schematic 1 4 3 Lead Breakout/Pinout (Bottom View − Facing Pins) 8 7 6 5 4 5 3 6 2 7 1 8 2 Note: Transformer is Wurth Electronics part #750312597 A 5 Vout version of this transformer is available on request. www.onsemi.com 3 DN05018/D Average efficiency for both 120 Vac and 230 Vac was 77%. Figure 1. Efficiency vs. Load Curves Standby (No Load) Input Power 120 Vac: 74 mW 230 Vac: 107 mW Figure 2. Full Load Output Ripple @ 120 Vac Input www.onsemi.com 4 DN05018/D Figure 3. MOSFET Drain Voltage (120 Vac Input, 12 V, 1 A Load on Output) Figure 4. MOSFET Drain Voltage (120 Vac Input, 12 V, 250 mA Output) dBuV NCP1075 Flyback 12V 800mA 120 v ac input 80 70 60 EN 55022; Class B Conducted, Quasi−Peak EN 55022; Class B Conducted, Average 50 40 30 20 10 0 Average −10 −20 1 10 9/14/2011 8:00:53 AM (Start = 0.15, Stop = 30.00) MHz Figure 5. EMI Profile www.onsemi.com 5 DN05018/D BILL OF MATERIALS Table 2. BILL OF MATERIALS FOR 12 Vout, 10 W NCP1075 FLYBACK Footprint Manufacturer Manufacturer Part Number Substitution Allowed 2 A, 60 V SMB ON Semiconductor MBRS260T3 No Designator Qty Description Value D7 (12 Vout) 1 Schottky Diode Tolerance D7 (5 Vout) 1 Schottky Diode 3 A, 40 V SMB ON Semiconductor MBRS2040L No D1, D2, D3, D4 4 Diode − 60 Hz 1 A, 800 V SMA ON Semiconductor MRA4007 No D5 1 Diode − Fast Recov. 1 A, 600 V Axial Lead ON Semiconductor 1N4937 No D6 1 Signal Diode 100 mA, 100 V SOD−123 ON Semiconductor MMSD4148A No U3 1 Programmable Zener 2.5 V SOIC8/ SOT23 ON Semiconductor NCP431A No U2 1 Optocoupler CTR >/= 0.5 4-pin Vishay or NEC SFH6156A−4 or PS2561L−1 Yes U1 1 Switcher IC − NCP1075 100 kHz SOT223 ON Semiconductor NCP1075ST100 No C1, C2 2 “X” Cap, Box Type 100 nF, X2 LS = 15 mm Rifa, Wima TBD Yes C8 1 “Y1” Cap, Disc Type 1 nF, Y1 LS = 7.5 mm Rifa, Wima TBD Yes C4 1 Ceramic Cap, Disc 1 nF, 1 kV 5% LS = 7.5 mm Rifa, Wima TBD Yes C7 1 Ceramic Cap, Monolythic 1 nF, 50 V 10% 1206 AVX, Murata TBD Yes C10, C11, C12 3 Ceramic Cap, Monolythic 100 nF, 50 V 10% 1206 AVX, Murata TBD Yes C3 1 Electrolytic Cap 22 mF, 400/450 V 10% LS = 7.5 mm, D = 16 mm UCC, Panasonic TBD Yes C6 1 Electrolytic Cap 4.7 mF, 50 Vdc 10% LS = 2.5 mm, D = 6.3 mm UCC, Panasonic TBD Yes C5 1 Electrolytic Cap 22 mF, 25 V 10% LS = 2.5 mm, D = 6.3 mm UCC, Panasonic TBD Yes C9A, C9B 2 Electrolytic Cap 1000 mF, 16 V 10% LS = 5 mm, D = 12.5 mm UCC, Panasonic TBD Yes R1 1 Resistor, 3 W, Wire Wound 4.7 W, 3 W 10% LS = 7.5 mm, D = 7 mm Ohmite, Dale TBD Yes R3 1 Resistor, 0.5 W, Metal Film 68 kW, 0.5 W 10% Axial Lead; LS = 12.5 mm Ohmite, Dale TBD Yes R2A, R2B 2 Resistor, 1/4 W SMD 3.3 MW 5% SMD 1206 AVX, Vishay, Dale TBD Yes R5 1 Resistor, 1/4 W SMD 10 W 5% SMD 1206 AVX, Vishay, Dale TBD Yes R4 1 Resistor, 1/4 W SMD 1 kW 5% SMD 1206 AVX, Vishay, Dale TBD Yes R9, R10 2 Resistor, 1/4 W SMD 10 kW 1% SMD 1206 AVX, Vishay, Dale TBD Yes R7 1 Resistor, 1/4 W SMD 1 kW 1% SMD 1206 AVX, Vishay, Dale TBD Yes R6 (12 Vout) 1 Resistor, 1/4 W SMD 1 kW 1% SMD 1206 AVX, Vishay, Dale TBD Yes R6 (5 Vout) 1 Resistor, 1/4 W SMD 240 W 1% SMD 1206 AVX, Vishay, Dale TBD Yes R8 (12 Vout) 1 Resistor, 1/4 W SMD 39 kW 5% SMD 1206 AVX, Vishay, Dale TBD Yes R8 (5 Vout) 1 Resistor, 1/4 W SMD 10 kW 1% SMD 1206 AVX, Vishay, Dale TBD Yes F1 1 Fuse, TR−5 Style 1.5 A TR−5, LS = 5 mm Minifuse L1A/B 2 Inductor (EMI Choke) 1 mH, 500 mA See Wurth Drawing LS = 5 mm, D = 8 mm T1 (12 Vout) 1 Transformer E20/10/6 Core See Mag Drawing Wurth Magnetics J1, J2 2 Screw Terminal LS = 0.2″ DigiKey NOTE: Grey indicates part change with Vout change. www.onsemi.com 6 Yes 7447728102 Yes Yes # 281−1435−ND Yes DN05018/D REFERENCES [3] ON Semiconductor Application Note AND8489/D [1] ON Semiconductor Data Sheet for NCP1251/D Controller in TSOP6 Package. [2] ON Semiconductor Design Notes DN05012/D, DN05014/D, DN05017/D. ON Semiconductor and the are registered trademarks of Semiconductor Components Industries, LLC (SCILLC) or its subsidiaries in the United States and/or other countries. SCILLC owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. SCILLC reserves the right to make changes without further notice to any products herein. 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