DN05080/D Design Note – DN05080/D NCP1060, 12 Vout, 2W Off-line Buck Regulator Device Application Input Voltage NCP1060 Smart Meters, Electric Meters, White Goods 85 to 265 V Output Voltage Output Ripple Typical Current Max Current Min Current PFC (Yes/No) Efficiency Inrush Limiting / Fuse Operating Temp. Range Cooling Method / Supply Orientation Signal Level Control Topology Up to 2 W at 12 Vout Off-Line 100 kHz Buck I/O Isolation Non-isolated Output Specification 4 to 16 Vdc depending on selected Z1 zener value Less than 1% 100 to 150 mA for 12Vout 160 mA 0 mA No See plots below External fuse required 0 to +50°C (dependent on IC1 cooling) Convection None Circuit Description This design note describes a very simple, low power, constant voltage output buck power converter intended for powering electronics for power goods, electrical meters and industrial equipment where isolation from the AC mains is not required. The switching element in the converter is ON Semiconductor’s NCP106x series of monolithic switchers. In this reference design, the NCP1060 is utilized with a 60 kHz switching frequency and a maximum output current of 150 mA. This buck circuit utilizes a simple charge pump or “bootstrap” type of voltage sensing and regulation scheme composed of D2, C1. This simple sensing technique eliminates the use of an optocoupler in the feedback loop. Thanks an on chip voltage reference and error amplifier no external active components are necessary for regulation. Just simple resistor divider composed of R2, R5 and R6 to bring portion of external voltage to FB pin. This helps to achieve load regulation +/-5% September 2015, Rev.0 Output Power over the loads 100% down to 1% of maximum rated load. Below 1% the output voltage will rise to the value of the overvoltage clamping zener diode D4 across the output. For a 12 V output a typical value for zener diode will be 15 V and at no load the output will be clamped at this level. The sensed voltage produced on C5 is also used to power the NCP106x controller through D1 once converter has started. This auxiliary Vcc to run the chip improves the overall efficiency of the circuit and prevents the controller from running in DSS mode under normal load conditions. Although this is low power output converter, full bridge rectifier is used, to lower input peak current. C4, L2 and C5 form a conducted EMI filter. The 1.2 mH buck output inductor is available in several surface mount or through hole configurations from multiple vendor. This inductor should be designed to handle high voltage. www.onsemi.com 1 DN05080/D Schematic Figure 1 – Buck converter schematic Output Regulation Figure 2 – Output voltage dependency on output current September 2015, Rev.0 www.onsemi.com 2 DN05080/D Typical Efficiency versus Load for 110 V and 230 V Figure 3 – Efficiency of the Buck Converter Output Ripple – 150 mA load, 230 Vac Input Figure 4 – Output Voltage Ripple at Full Load September 2015, Rev.0 www.onsemi.com 3 DN05080/D References: ON Semiconductor Application Notes: AND8318, AND8328 ON Semiconductor Design Notes: DN05014, DN06011, DN06052, DN05058 ON Semiconductor NCP1060 High-Voltage Switcher for low Power offline SMPS. PC Board: Figure 5 - components position on PCB (top side) Figure 6 - components position on PCB (bottom side) September 2015, Rev.0 www.onsemi.com 4 DN05080/D Figure 7 – PCB’s bottom side Table 1– Bill of materials Designator Quantity Value Tolerance Footprint Manufacturer Manufacturer Part Number CAPACITOR ELECTROLYTIC CAPACITOR 150 nF 220 μF / 35 V 10% 0805 THROUGH HOLE Kemet C0805C154K5RACTU 100 nF 2.2 uF / 450 V 10 μF / 25 V 10% 39 nF 10% NU Description C1 1 C2 1 C3, C7 2 C4, C5 2 C6 1 CAPACITOR ELECTROLYTIC CAPACITOR ELECTROLYTIC CAPACITOR C8, C9 2 CAPACITOR CX1 1 CAPACITOR X2 D1 1 DIODE D2, D3 2 D4 Koshin KZH-35V221MG4 0805 THROUGH HOLE THROUGH HOLE Kemet United ChemiCon C0805C104K5RACTU Koshin KLH025V100ME3 Kemet C0805C393K5RACTU - 0805 THROUGH HOLE - MMSD4148 - SOD123 DIODE MURA160 - SMA 1 ZENER DIODE MMSZ15 5% SOD123 D5, D6, D7, D8 4 DIODE MRA4007 - SMA IC1 1 SWITCHER NCP1060 - SOIC10 L1 1 INDUCTOR 1.2 mH 10% L2 1 INDUCTOR 1.0 mH 10% (L,N,+12V,GND) 4 TERMINAL PIN 1.0 mm - R1 1 VARISTOR 820572711 - SMD/SMT THROUGH HOLE THROUGH HOLE THROUGH HOLE ON Semiconductor ON Semiconductor ON Semiconductor ON Semiconductor ON Semiconductor Würth Elektronik Würth Elektronik R2 1 RESISTOR 33 kΩ 1% 0805 R3 1 RESISTOR 20 Ω 5% 0613 R4 1 RESISTOR NU - 0805 R5 1 RESISTOR 13 kΩ 1% 0805 R6 1 RESISTOR 220 kΩ 1% 0805 September 2015, Rev.0 20% 20% 20% www.onsemi.com Ettinger Würth Elektronik Rohm Semiconductor VIshay BC Components Rohm Semiconductor Rohm Semiconductor EKMG451ELL2R2MJC5S MMSD4148T1G MURA160T3G MMSZ15T1G MRA4007T3G NCP1060AD060R2G 768775312 768772102 13.14.119 820572711 MCR10ERTF3302 AC03000002009JAC00 MCR10ERTF1302 MCR10ERTF2203 5 DN05080/D Figure 8 – PCB’s top side Figure 9 – PCB’s bottom side 1 © 2015 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 Jaromír Uherek, e-mail: mailto:[email protected] September 2015, Rev.0 www.onsemi.com 6