DN06038/D Design Note – DN06038/D 18 to 24 Volt, 85 Watt, Off-line PSU with Short Term, High Surge Current Capability Device Application Input Voltage Output Power Topology I/O Isolation NCP1217 Industrial – motors, solenoids, etc. 90 to 265 Vac 85 Watts CCM Flyback Yes – 3 kV Other Specifications Output Voltage Ripple Nominal Current Max Current Min Current Others Output 1 Output 2 Output 3 Output 4 18 to 24 V Less than 1% 3.5 A 7–8A 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 85% Inrush Limiting / Fuse 3 A fuse, Thermistor inrush limiter Operating Temp. Range Cooling Method/Supply Orientation Signal Level Control 0 to +60°C Convection None High output surge current capability for several seconds. Circuit Description This Design Note is a modification/upgrade to ON Semiconductor’s Application Note AND8076. The NCP1217 current mode controller (100 kHz version) has been used to eliminate the additional discrete circuitry required by the original NCP1200/NCP1203 controller for ramp compensation and OVP functions. By using a continuous conduction mode (CCM) flyback topology, which has a constant power output characteristic, this power supply is capable of supplying short term, high surge currents of over 7 A for powering industrial equipment such as motors, solenoids or other inductive loads. Overcurrent protection is initiated at approximately 3.6 A. However, the output current will increase up to double this as the output voltage decreases due to the overload. At a threshold determined by the value of resistor R8, the supply will enter “hiccup” mode overcurrent protection for reduced dissipation in the event of a “hard” short circuit. For the given flyback transformer design, the output voltage is adjustable via R14 from 18 volts to about 24 volts to suit the intended application. The OVP trip level March 2008, Rev. 0 is determined by zener Z1. The overcurrent point is set by parallel resistors R6A and B, and ramp compensation for CCM operation is adjusted by R11. Additional details on basic circuit operation, critical components, and the NCP1217 characteristics can be found in the Application Note AND8076 and the data sheet for the NCP1217 controller. The CCM flyback transformer T1 is available from Coilcraft as part number Z9260-A or Z9007-B. EMI inductor L2 is Coilcraft E3505-AL (or similar), and L1 is an optional output ripple inductor that is Coilcraft part PCV-0472-05L. Key Features y 3.5 A continuous output with over 7 A surge capability with adjustability on the latter threshold y Overvoltage and overcurrent protection y Input EMI filter for conducted emissions attenuation y Thermistor input surge current limiting at turn-on y Measured efficiencies of 85% at 120 Vac and 87% at 230 Vac input at full load y Adjustable 18 to 24 volt output range (via R14) www.onsemi.com 1 DN06038/D Schematic 1 BD1 6A, 600V AC in L2 TH1 5 ohms 3A R1 0.33uf 1.0M "X2" 1/2W 0.33uf "X2" D2 R4 4.7K, 0.5W L1 4.7uH D4 MBR20100 + C9 C5 Q1 FQP6N60 C2 C1 T1 D1 MRA4007T C3 270uF 400Vdc MSD4148A F1 3A C4 R3 100nF R2 39K 2W x2 C7 C6 C8 0.1 18 - 24 V, 3.5 A output _ 2,200uF 35V x 3 R6A,B 0.27 ohm, 0.5W x2 R5 15 220uF C10 D3 2.2 nF "Y1" R7 MMSD4148A 10 R8 2.4K NCP1217 (100 kHz) R9 100 R13 C15 47uf 35V MMSZ5252BT 8 6 Z1 24V (OVP) 1.2K, 0.5W R11 2.4K 5 U1 SFH6156A-2 2 1 U2 4 R10 4.7K C13 47uF, 35V C14 0.1uF C12 1nf Opto R14 39K (20V) C11 U3 TL431A Notes: 1. Crossed schematic lines are not connected. 2. Heavy schematic lines indicate recommend ground plane areas. 3. Q1 and D4 require heatsinks. 4. R8 sets U1 Vcc level for overcurrent "hiccup" mode threshold. 5. R11 sets ramp compensation for U1. 6. R6A, B (paralleled resistors) set overcurrent trip level. 7. R14 sets Vout. 8. All resistors 1/8 or 1/4 watt unless otherwise noted. Vout Adj. R12 1K 3 0.1uf R15 5.6K 18 - 24 Vout, 85 Watt, Off-Line CCM Flyback Power Supply Additional collateral from ON Semiconductor y NCP1217: Current Mode Controller Fixed Frequency Operation y MMSD4148: 100 V Switching Diode y TL431A: Programmable Precision Reference y MBR20100: 20 A, 100 V Schottky Rectifier y Application Note AND8076: a 70 W Low Standby Power Supply with NCP120x Series 1 © 2008 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] March 2008, Rev. 0 www.onsemi.com 2