DN06011/D Design Note – DN06011/D 8 W Off-Line Non-Isolated Buck Regulator Device NCP1014 Application Input Voltage Output Power Topology I/O Isolation 90 to 270 Vac 8W Off-Line Buck None Industrial Control Other Specifications Output Voltage Ripple Nominal Current Max Current Min Current Output 1 Output 2 Output 3 Output 4 25 Vdc 200 mV max 325 mA 400 mA zero N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A PFC (Yes/No) No Minimum Efficiency 80% Input Connector Fuse 0.5 A fuse Operating Temp. Range Cooling Method/Supply Orientation 0 to +70°C Convection Circuit Description Key Features This off-line buck regulator is intended for industrial control or similar applications where a low power regulated output voltage is required, but ac mains isolation is not necessary. The buck circuit is designed around ON Semi’s NCP1014 series of integrated, monolithic switching regulators and will provide up to 400 mA peak output current with proper heatsinking on the regulator. Magnetic components are “off-the-shelf” parts from Coilcraft Inc. Zener diode D7 can be changed to produce other output voltages as required down to around 3 volts and as high as 50 volts with appropriate voltage rating changes for C4, C5 and D6. An input conducted EMI filter is included (C1, L1), as is a simple “failsafe” OVP zener (D6). R1 is an optional inrush limiting resistor. y Very simple and low cost circuit for low power, nonisolated off-line applications requiring a single output. y Off-the-shelf magnetic components. y Conducted EMI filter. y Output voltage can easily be tailored to application. y Over-current and over-temperature protection inherent in NCP1014 integrated regulator. September 2006, Rev. 1 www.onsemi.com 1 DN06011/D Schematic 1 R1 15, 2W AC input D1, 2, 3, 4 1N4007 x 4 4.7nF "x" 80 - 265Vac L2 L1, 1 mH C1 F1 0.5A C2 + 2.7 mH 500 mA C3 4.7uF, 400Vdc x2 C5 0.1uF 50V C4 330uF 35V D5 MUR160 D6 1N4751 (OVP) Output 25V, 325 mA _ D7 Vset 1N5252B (24V) NCP1014 (SOT-223) 3 R2 U1 2 4 4 1 + U2 1 R3 270 C6 C7 47uF 25V 1nF 47 3 opto 2 NOTES: 1. L1 is Coilcraft part RFB0807-102 (1 mH @ 250 mA) for EMI compliance. 2. L2 is Coilcraft part PCH-45-275L (leaded inductor) 3. U1 is 100 kHz version of NCP1014. 4. D7 zener sets Vout max: Vout = Vz + 0.85V. 5. D6 provides failsafe OVP clamping if U1 fails (F1 will open). 6. Pin 4 tab of U4 should be soldered to sufficient copper pcb clad for adequate heatsinking. 7. Crossed schematic lines are not connected. 8. CAUTION: Output is not isolated from AC input and represents lethal hazard. 8 Watt Off-Line Buck Converter (Non-Isolated) 1 © 2006 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 Frank Cathell, e-mail: [email protected] September 2006, Rev. 1 www.onsemi.com 1