DN05017/D Low Power, Ultra‐wide AC Input Range, E‐meter Power Supply www.onsemi.com DESIGN NOTE Table 1. DEVICE DETAILS Device Application Input Voltage Output Power Topology I/O Isolation NCP1251 Smart Meters, Electric Meters 70 to 520 Vac Up to 10 W DCM Flyback Isolated Characteristic Output Specification Output Voltage 12 Vdc Ripple 200 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) Minimum Efficiency See Efficiency Plots Below Inrush Limiting/Fuse Inrush Resistor (R1) Operating Temp. Range 0 to +60°C (Dependent on Q1 Heatsinking) Cooling Method/Supply Orientation Convection Signal Level Control None Circuit Description circuit provides for over power compensation (R11) as well as over-current and over-voltage protection. An input EMI filter is also provided that meets FCC Level B for conducted EMI. SPICE simulations of the input filter also indicates that it will also provide lightning transient protection with an optional TVS device (TVS1) across the input. Performance characteristics for efficiency, output ripple, hold-up time, EMI, and switching characteristics are shown in the figures below. This design note describes a simple, low power (10 W or less), ultra-wide AC input range, constant voltage power supply intended for powering the electronics for electric meters, Smart Grid or similar industrial applications where isolation from the AC mains is required along with a very wide input voltage range. The power supply is a simple flyback converter topology which operates in discontinuous conduction mode (DCM). The converter utilizes a 1.5 kV rated MOSFET (Q1) to allow for the extremely wide AC input range. The overall efficiency due to the ultra-wide range design is less than that of the universal AC input version (85 – 270 Vac) of a similar NCP1251 circuit presented in ON Semiconductor Design Note DN05012. This Design Note provides the complete circuit and transformer design details for a 12 V, 1 A power supply. Other output voltages from 3.3 up to 28 Vdc are easy to implement by modifying the values (or ratings) of R12, R16, D8, C10 and T1’s secondary turns. The NCP1251B control © Semiconductor Components Industries, LLC, 2015 January, 2015 − Rev. 2 Key Features • Ultra-wide AC Input Range (70–520 Vac) with 1.5 kV Rated MOSFET (Q1) • Input Filter (Pi-network) for Conducted EMI Attenuation and Input Transient Protection • Very Low Standby Power Consumption • Secondary Circuit Easily Configured for Different Output Voltages • Inherent Over-current, Over-voltage Protection and Optional Over-power Compensation 1 Publication Order Number: DN05017/D www.onsemi.com 2 10 W NCP1251 Power Supply with Ultra Wide AC Input Notes: 1. Crossed lines on schematic are NOT connected. 2. U2 is NEC PS2561L−1 or equivalent optocoupler (CTR > 50%) 3. R1 is for inrush limiting − use wire would resistor for high joule rating. 4. L1A/L1B are Coilcraft RFB0810−821L inductors (820 mH, 500 mA). 5. Output cap (C10) is radial lead, low impedance type (UCC LXV series or similar). 6. R11 is output power compensation resistor. 7. TVS1 is optional transient voltage suppressor for lighting protection. 8. C1 and C2 are 480 Vac rated “X” capacitors for ultra-wide AC input. 9 See drawing for T1 details. DN05017/D CIRCUIT SCHEMATIC DN05017/D 12 V Transformer Design Project/Customer: ON Semiconductor − 12 W, 12 Vout NCP1251 Flyback Part Description: Flyback Transformer, 12 Vout (Wurth Electronics part # 750312495) Schematic ID: T1 Core Type: EE20/10/6 Ferrite Core; 3C90 Material or Similar Core Gap: Gap for 190 ± 200 mH across Primary A (Pins 1 − 10) Inductance: 750 mH Total (±5%) Measured from Pin 1 to Pin 9 with Pins 2 and 10 Connected Bobbin Type: 10 Pin Horizontal Mount for EE20/10/6 Windings (in order): Winding #/Type Turns/Material/Gauge/Insulation Data Primary A (1 − 10) 30T of #28HN over 1 layer (25 TPL). Insulate for 1 kV to next winding. Self leads to pins. Vcc (3 − 8) 7 turns of #28 HN over 1 layer, spiral wound over primary A. Self leads to pins. Insulate to 1 kV to next winding with tape. 12 V Secondary (5 − 6) 6 turns bifilar of #24 triple insulated wire over one. layer (two strands). Self leads to pins. (Note: #26 is also acceptable here if the fit is too tight for one layer) Primary B (2 − 9) Same as Primary A. Insulate with tape and self-leads to pins. Hipot: 3 kV from primaries & Vcc to secondary for 1 minute. Schematic Lead Breakout/Pinout (Top View of Bobbin) 10 10 Pri A 1 9 Pri B 2 8 9 8 7 6 0.15″ Pin Separation (8 places) 5 12 V sec (bifilar) 0.60″ Pin Rows 6 Pri C 3 1 A 5 Vout version of this transformer is available on request. www.onsemi.com 3 2 3 4 5 DN05017/D Figure 1. Efficiency Plots Figure 2. Full Load Output Ripple (100 Vac Input) Figure 3. Full Load Output Ripple (480 Vac Input) www.onsemi.com 4 DN05017/D Figure 4. Full Load Hold-up Time at 120 Vac (10 W Output, C3/C4 = 47 mF) Figure 5. Full Load Hold-up Time at 230 Vac (10 W Output, C3/C4 = 47 mF) Figure 6. EMI Profile – Class B, Average (220 Vac Input, 10 W Output) www.onsemi.com 5 DN05017/D Figure 7. Q1 MOSFET Drain to Source Voltage Profile at 480 Vac Input (25% Rated Load) Figure 8. Q1 MOSFET Drain to Source Voltage Profile at 480 Vac Input (Full Load) www.onsemi.com 6 DN05017/D BILL OF MATERIALS Table 2. BILL OF MATERIALS FOR 10 W, NCP1251 ULTRA-WIDE INPUT FLYBACK Footprint Manufacturer Manufacturer Part Number Substitution Allowed SMC ON Semiconductor MBRS3100T3G No 3 A, 60 V SMC ON Semiconductor MBRS360T3G No 1 A, 1.5 kV DPAK Sanyo/ ON Semiconductor 2SK4177 No 1 A, 1 kV SMA ON Semiconductor MRA4007 No Diode − Fast Recov. 1 A, 600 V Axial Lead ON Semiconductor 1N4937 No Signal Diode 100 mA, 100 V SOD−123 ON Semiconductor MMSD4148A No 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 Controller − NCP1251B TSOP−6 ON Semiconductor NCP1251B No C1, C2 2 “X2” Cap, Box Type 7 x 16 x 26.5 mm; LS = 22.5 mm Kemet 474N31000001M Yes C13 1 Y1 Cap − Ceramic Disc 1 nF, 3 kV LS = 7.5 mm Rifa, Wima C5 1 Ceramic Cap, Disc 2.2 nF, 2 kV 5% LS = 7.5 mm Rifa, Wima TBD Yes C6 1 Ceramic Cap, Disc 1 nF, 50 V 10% 1206 AVX, Murata TBD Yes C11, C12 2 Ceramic Cap, Disc 100 nF, 50 V 10% 1206 AVX, Murata TBD Yes C7, C8 2 Ceramic Cap, Disc 100 pF, 50 V 5% 1206 AVX, Murata TBD Yes C3, C4 2 Electrolytic Cap 47 mF, 400 V 10% LS = 7.5 mm, D = 16 mm UCC, Panasonic TBD Yes C9 1 Electrolytic Cap 4.7 mF, 50 Vdc 10% LS = 2.5 mm, D = 6.3 mm UCC, Panasonic TBD Yes C10A, C10B 2 Electrolytic Cap 1000 mF, 16 V 10% LS = 5 mm, D = 12.5 mm UCC, Panasonic TBD Yes (5 Vout) 2 Electrolytic Cap 3300 mF, 6.3 V 10% LS = 5 mm, D = 12.5 mm UCC, Panasonic TBD Yes R1 1 Resistor, 5 W, Wire Wound 6.8 W, 5 W 10% LS = 7.5 mm, D = 7 mm Ohmite, Dale TBD Yes R2 1 Resistor, 1 W, Metal Film 47 kW, 1 W 10% Axial Lead; LS = 25 mm Ohmite, Dale TBD Yes R10 1 Resistor, 1/2 W Metal Film 1.2 W, 1/2 W 10% Axial Lead; LS = 12.5 mm Ohmite, Dale TBD Yes R6, R8, R15, R16 4 Resistor, 1/4 W SMD 1 kW 1% SMD 1206 AVX, Vishay, Dale TBD Yes R4A, R4B, R4C, R4D 4 Resistor, 1/4 W SMD 390 kW 5% SMD 1206 AVX, Vishay, Dale TBD Yes R3A/B, R5A/B 4 Resistor, 1/4 W SMD 1 MW 5% SMD 1206 AVX, Vishay, Dale TBD Yes R11 1 Resistor, 1/4 W SMD TBD 1% SMD 1206 AVX, Vishay, Dale TBD Yes R7 1 Resistor, 1/4 W SMD 0W 1% SMD 1206 AVX, Vishay, Dale TBD Yes R9, R13, R14 3 Resistor, 1/4 W SMD 10 kW 1% SMD 1206 AVX, Vishay, Dale TBD Yes R12 (12 Vout) 1 Resistor, 1/4 W SMD 39 kW 5% SMD 1206 AVX, Vishay, Dale TBD Yes R12 (5 Vout) 1 Resistor, 1/4 W SMD 10 kW 1% SMD 1206 AVX, Vishay, Dale TBD Yes R17, R18 2 Resistor, 1/4 W SMD 5.6 kW 5% SMD 1206 AVX, Vishay, Dale TBD Yes F1 1 Fuse, TR−5 Style 2A TR−5, LS = 5 mm Minifuse L1A/B 2 Inductor (EMI Choke) 820 mH, 500 mA Dia = 10mm, LS = 5mm Coilcraft Designator Qty Description Value D8 (12 Vout) 1 Schottky Diode 3 A, 100 V D8 (5 Vout) 1 Schottky Diode Q1 1 MOSFET − 2SK4177 D1, D2, D3, D4, D6 5 Diode − 60 Hz D5A, D5B 2 D7 1 U3 Tolerance 100 nF, 5200 Vac www.onsemi.com 7 Yes Yes RFB0810−1821L Yes DN05017/D Table 2. BILL OF MATERIALS FOR 10 W, NCP1251 ULTRA-WIDE INPUT FLYBACK (continued) Footprint Manufacturer Manufacturer Part Number Substitution Allowed E20/10/6 Core See Mag Drawing Wurth Magnetics 750312495 Yes E20/10/6 Core See Mag Drawing Wurth Magnetics 750312279 Yes LS = 0.2″ DigiKey # 281−1435−ND Yes Designator Qty Description Value T1 (12 Vout) 1 Transformer T1 (5 Vout) 1 Transformer J1, J2 2 Screw Terminal Tolerance NOTE: Grey indicates part change with Vout change 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. 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. 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