DN05014/D Universal AC Input, Non‐isolated 6 W E‐meter Buck Power Supply www.onsemi.com DESIGN NOTE Table 1. DEVICE DETAILS Device Application Input Voltage Output Power Topology I/O Isolation NCP1219B, NCP431, NDD05N50 Smart Meters, Electric Meters 60 to 300 Vac 6 W Nominal Buck Converter Non-isolated Characteristic Output Specification Output Voltage 12 Vdc ±1% Ripple 100 mV p/p @ Full Load Nominal Current 500 mA Continuous Max Current 1.0 A Maximum (10 Second Surge) Min Current Zero PFC (Yes/No) No, (Pout < 25 W) Efficiency 77% at Nominal Load @ 120 Vac Inrush Limiting/Fuse Inrush Resistor (R1) Operating Temp. Range 0 to +60°C Cooling Method/Supply Orientation Convection Signal Level Control None Circuit Description The half-wave input rectifier section utilizes a pi-network, split bulk capacitor scheme which provides for both high input transient protection (with optional TVS1) and effective conducted EMI attenuation. The choice of the total bulk capacitance can be selected for the desired output hold-up time during line cycle outages or extreme brownout conditions. Hold-up time along with efficiency and output ripple plots are shown below. This design note describes a simple, low power, off-line, extended universal AC input buck power supply intended for powering utility electric meters or similar industrial equipment or white goods where isolation from the AC mains is not required and low cost and circuit simplicity is essential. The featured power supply is a simple buck regulator topology utilizing ON Semiconductor’s NCP1219B current mode PWM controller driving an external DPAK MOSFET (Q1). The controller circuitry is ground referenced to the freewheel diode’s cathode terminal which is a switched node. This allows for simple half-wave input rectification and a common AC input to dc output node. Because the NCP1219 controller and its associated circuitry are at a switched node, optocoupler feedback from the NCP431 output sensing amplifier is utilized to avoid regulation inaccuracies typically caused by charge pump and/or bootstrap type sensing schemes. Diode D4 also powers the control circuitry from the output voltage once the converter has started. © Semiconductor Components Industries, LLC, 2015 January, 2015 − Rev. 2 Key Features • Extended Universal AC Input Range (60–300 Vac) with up to 10 W Peak Output • Bulk Pi-network Filter for Conducted EMI Attenuation • • • 1 and Input Transient Protection AC Input to DC Output Common Node Inherent Over-current Protection and Optional Z1 Over-voltage Protection Clamp Simple, Low Cost Circuitry with Off-the-Shelf Output Inductor (L2) Publication Order Number: DN05014/D 2 5.1, 2W R1 C1 100nF ”x” 1K R2 47 uF, 400Vdc TVS1 C3 L1, 1 mH 0.6 A 47uF 400Vdc + C2 D1 MRA4007 D2 C9 1nF + 47uF 25V C8 2 6 8 3 4 1K MMSD4148A R3 R4 R5 U2 4 3 100pF 2 1 www.onsemi.com 1.5K R8 1K U3 NCP431 10K L2 0.1 C7 10K R11 R10 39K 1000uF 0.1uF 16V 50V C6 390uH, 1.3A R12 C10 MURS 260 D3 R7B 1.6 ohms R7A NDD05N50Z 1N4744B (15V/1W) Z1 _ Output 12V, 0.5A + 6W Off−Line Buck Converter Using NCP1219B65 With Optocoupler Voltage Sensing (Rev 5) R9 1K MURA160 D4 0.1 10K 10K U1 1 C4 R6 C5 5 1. Vout set by R10 & R11. 2. L1 is Wurth 744732102 or Coilcraft RFB1010−102L; L2 is Coilcraft PCX−45X−394LT. 3. Red lines indicate areas/traces that should be minimized for capacitance. 4. Q1 should be heatsunk via ground tab to as large as possible copper clad area. 5. D3 should have large pad areas for heatsinking. 6. R1 should be wire wound or carbon composition for high joule rating. 7. Z2 is optional output OVP zener. 8. Crossed schematic lines are not connected. 9. U2 is NEC PS2561L−1 optocoupler or similar (CTR > 0.5) 10. TVS1 is optional transient suppressor Notes: Neutral 85 − 270Vac AC input Line F1 1A NCP1219BD65 Q1 DN05014/D CIRCUIT SCHEMATIC DN05014/D Figure 1. Efficiency Plots at 120 Vac and 230 Vac Figure 2. Full Load Output Ripple Figure 3. Hold-up Time at 100 Vac with Cbulk = 94 mF www.onsemi.com 3 DN05014/D Figure 4. Hold-up Time at 230 Vac with Cbulk = 94 mF dBuV NCP1219 Buck 12V 10W 120 v ac input 80 70 Peak 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 – Peak (Blue) and Average (Red) Plots www.onsemi.com 4 DN05014/D BILL OF MATERIALS Table 2. BILL OF MATERIALS FOR 12 Vout, 6 W NCP1219 OFF−LINE BUCK CONVERTER Footprint Manufacturer Manufacturer Part Number Substitution Allowed 5 A, 500 V DPAK ON Semiconductor NDD05N50Z No Diode − 60 Hz, 1 A, 1 kV SMA ON Semiconductor MRA4007 No 1 Diode − Ultra Fast Recov 2 A, 600 V SMC ON Semiconductor MURS260 No D4 1 Diode − Ultra Fast Recov 1 A, 600 V SMA ON Semiconductor MURA160T3 D2 1 Signal Diode 100 mA, 100 V SOD−123 ON Semiconductor MMSD4148A Z1 1 Zener Diode − 15V 1 W, 15 V Axial Lead TBD 1N4744A U3 1 Programmable Zener 2.5 V SOIC8/SOT2 3 ON Semiconductor NCP431A No U2 1 Optocoupler CTR >/= 0.5 4-pin Vishay or NEC SFH6156A−4 or PS2561L−1 Yes U1 1 Controller − NCP1219BD65 65 kHz SOIC8 ON Semiconductor NCP1219BD65 No TVS1 1 Voltage Suppressor TBD (optional) Axial Lead; LS = 0.8″, Fat Leads ON Semiconductor TBD − optional Designator Qty Description Value Q1 1 Mosfet − NDD05N50Z D1 1 D3 Tolerance No C1 1 “X” Cap, Box Type 100 nF, X2 LS = 15 mm Rifa, Wima TBD Yes C2, C3 2 Electrolytic Cap 47 mF, 400 V 10% LS = 7.5 mm, D = 16 mm UCC, Panasonic TBD Yes C9 1 Ceramic Cap, Monolythic 1 nF, 50 V 10% 1206 AVX, Murata TBD Yes C4, C7, C10 3 Ceramic Cap, Monolythic 100 nF, 50 V 10% 1206 AVX, Murata TBD Yes C5 1 Ceramic Cap, Monolythic 100 pF, 50 V 10% 1206 AVX, Murata TBD Yes C8 1 Electrolytic Cap 47 mF, 25 Vdc 10% LS = 2.5 mm, D = 6.3 mm UCC, Panasonic TBD Yes C6 1 Electrolytic Cap 1000 mF, 16 V 10% LS = 5 mm, D = 12.5 mm UCC, Panasonic TBD Yes R1 1 Resistor, 5 W, Wire Wound 5.1 W, 5 W 10% LS = 7.5 mm, D = 7 mm Ohmite, Dale TBD Yes R4, R5, R11, R12 4 Resistor, 1/4 W SMD 10 kW 1% SMD 1206 AVX, Vishay, Dale TBD R7A, R7B 2 Resistor, 1/4 W SMD 1.6 W 1% SMD 1206 AVX, Vishay, Dale TBD Yes R2, R3, R6, R9 4 Resistor, 1/4 W SMD 1 kW 5% SMD 1206 AVX, Vishay, Dale TBD Yes R8 1 Resistor, 1/4 W SMD 1.5 kW 5% SMD 1206 AVX, Vishay, Dale TBD Yes R10 1 Resistor, 1/4 W SMD 39 kW 1% SMD 1206 AVX, Vishay, Dale TBD F1 1 Fuse, TR−5 Style 1A TR−5, LS = 5 mm Minifuse L1 1 Inductor (EMI Choke) 1 mH, 600 mA Dia = 11 mm, LS = 5 mm Coilcraft RFB1010−102L L2 1 Buck Inductor − 390 mH 390 mH, 1.3 A Axial Lead LS=26mm, Dia=11mm Coilcraft PCH−45X−394LT J1, J2 2 Screw Terminal LS = 0.2” DigiKey #281−1435−ND www.onsemi.com 5 Yes Yes Yes DN05014/D REFERENCES [3] ON Semiconductor Application Note AND8318/D. [1] ON Semiconductor data sheet for NCP1219 controller in SOIC8 package. [2] ON Semiconductor Design Notes DN06011/D, DN06037/D, DN06066/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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