DN06027/D Design Note – DN06027/D Universal Input, 5 W, LED Ballast Device Application Input Voltage Output Power Topology I/O Isolation NCP1013 Solid State Lighting 85 – 265 Vac 5W Flyback Yes Other Specifications Output 1 10 Vmax 700 mA Output Voltage Nominal Current PFC (Yes/No) No Target Efficiency 65 % at nominal load Max Size 58 x 30 x 19 mm Operating Temp Range Cooling Method/Supply Orientation Signal Level Control 0 to +70°C (open frame) Convection No Circuit Description Key Features The controller used in this application is a low cost monolithic design, the NCP1013. This, and the other members of the family, from the NCP1010 to the NCP1014, allow for the design of low cost, yet fully featured, switched mode powers supplies. They integrate many peripheral circuits, from start-up to current limit, whilst also adding the ability to run directly from the HV bus, thus obviating the need for a bias winding, and an overload feature ensuring low dissipation in overload and short –circuit. The design comprises and input filter, bridge rectifier (using low cost 1N4007 diodes), bulk capacitors and line inductor in π-filter arrangement, the power stage, rectifier diode and smoothing capacitors. Feedback is CVCC, constant current drive for the LED’s with a constant voltage in the event of an open circuit output. y Wide input voltage range – 85 Vac to 265 Vac y Small size, and low cost y Good line regulation y High efficiency y Overload and short circuit protection. Number of LED’s in series. LED Current 350 mA LUXEON® I 2 LUXEON® III 2 700 mA 1A #NOTE1 2 1 1 1 #NOTE1 2 2 1 2 2 1 Vz (D7) 9V1 8V2 5V1 R3 & R4 3R6 1R8 1R2 ® ® ® LUXEON V LUXEON K2 LUXEON Rebel #NOTE1: Out of LED specification. July 2008, Rev. 1 www.onsemi.com 1 DN06027/D Schematic LED Current The light output of an LED is determined by the forward current so the control loop will be constant current, with a simple Zener to limit the maximum output voltage. For a white LUXEON® K2 the VI characteristics are: IF VF 350 mA 3.42 V 700 mA 3.60 V 1000 mA 3.72 V 1500 mA 3.85 V I LED = 0.6V .........................................(Eq.1) RSENSE Total sense resistor power dissipation is: PD = I LED × 0.6V ....................................(Eq.2) Driving two LED’s at 700 mA thus gives an output power of 5.04 W at 7.2 V. Inductor selection In a flyback converter the inductance required in the transformer primary is dependant on the mode of operation and the output power. Discontinuous operation requires lower inductance but results in higher peak to average current waveforms, and thus higher losses. For low power designs, such as this ballast, the inductance is designed to be just continuous (or just discontinuous) under worst case conditions, that is minimum line and maximum load. The specification for this ballast is as follows: • Universal input – 85 VAC to 265 VAC • 5 W output power • 700 mA output current So for 700 mA we need a 0.9 Ω sense resistor capable of dissipating 420 mW, two 330 mW surface mount resistors, 1.8 Ω each in parallel, are used. allowance will be made for this by using 100 V as the minimum input voltage. Assuming efficiency (η) of 85% we get an input power of: PIN = POUT η = 5.9 W ...............................(Eq.3) At a switching frequency of 100 kHz this gives an energy per cycle requirement, that is the energy that must be stored in the primary inductance on each cycle, of: E= This gives us a minimum DC input voltage of 120 V, there will be some sag on the DC bulk capacitors so an July 2008, Rev. 1 The output current is sensed by a series resistance, once the voltage drop across this reaches the base-emitter threshold of the PNP transistor current flows in the optocoupler diode and thus in the FB pin of the NCP101x. The LED current is thus set by: P f SW = 5.9 = 59 µJ ................(Eq.4) 100 ×10 3 For an inductor: E = 12 LI 2 ................................................(Eq.5) www.onsemi.com 2 DN06027/D We therefore get N < 32 from (Eq.11) and N < 12.9 from (Eq.13), clearly we need to use the lower figure of 12.9. Also: V =L di ..................................................(Eq.6) dt Rearranging and combining (Eq.5) and (Eq.6) gives: Putting N=12.9 and VIN = 100 V into (Eq.9) we get δ = 0.499, and from (Eq.8), dt = 4.99 µs. This gives us, from (Eq.7), the minimum inductance required which is 2.1 mH. We shall use 2.3 mH. We can now establish the peak primary current and select the correct member of the NCP101x family. V 2 dt 2 L= ..............................................(Eq.7) 2E Where; V is VIN(min) = 100 V, E is the energy per cycle = 59 µJ dt = and dt is the on time; δ f SW Rearranging (Eq.6) we get: ...............(Eq.8) di = For a flyback topology the duty cycle is: δ= VOUT Thus di = 217 mA which, as stated earlier, is equal to IPK in discontinuous mode. .....................................(Eq.9) VIN + VOUT N where N is the transformer turns ratio. For the NCP101x family of regulators the turn’s ratio is determined from the constraints of not exceeding the 700 V maximum rating on the DRAIN pin, and also not taking the DRAIN pin below ground. N × (VOUT + V f ) + VIN (max ) + Vleak ≤ 700 (Eq.10) Or N≤ (700 − V (V IN ( max ) OUT − Vleak ) +Vf ) N × (VOUT + V f ) ≤ VIN (min) .....................(Eq.12) (V OUT +Vf ) IPK(nom) IPK(max) NCP1010 90 100 110 NCP1011 #1 225 250 275 NCP1012 #2 225 250 275 NCP1013 #2 315 350 385 NCP1014 #2 405 450 495 #1 22Ω FET #2 11Ω FET IC Consumption The IC internal consumption is quoted as a maximum 1.15 mA, typically 0.95 mA. This is dissipated as loss in the regulator itself and is in addition to our estimated 85% efficiency that just relates to the transformer throughput. This loss goes from typically 115 mW at 85 Vac to 356 mW at 265 Vac with a maximum, at 265 VAC, of 431 mW. Or VIN (min) IPK(min) #1 Whilst the NCP1011 has a current limit inception point between 225 mA and 275 mA there is little margin for spikes and parameter variances so the NCP1013 will be the regulator used. .................(Eq.11) And N≤ Vdt ...............................................(Eq.14) L ..................................(Eq.13) Where: VIN(max) is the maximum rectified input = 375 V. VIN(min) is the minimum rectified input = 100 V. VOUT is 7.2 V (5 W @ 700 mA). Vleak is the leakage spike associated with the leakage inductance of the transformer. A well constructed transformer with a low leakage inductance and some snubbing of the DRAIN pin will keep this value down. A figure of 80 V will allow for a safety margin. Vf is the forward drop of the output rectifier diode, in this case a Schottky so 0.5 V. July 2008, Rev. 1 www.onsemi.com 3 DN06027/D MAGNETICS DESIGN DATA SHEET Project / Customer: ON Semiconductor/Future Lighting Solution Part Description: 5 W Transformer Schematic ID: - Core Type: - Core Gap: Gap for 2.3 mH Inductance: 2.3 mH Bobbin Type: - Windings (in order): Winding # / type Turns / Material / Gauge / Insulation Data N1, Primary Start on pin 1 and wind 128 turns, of Grade 2 ECW, in one neat layer across the entire bobbin width. Finish on pin 2. N2, Secondary Start on pin 8 and wind 10 turns, of Tex E triple insulated wire or equivalent, distributed evenly across the entire bobbin width. Finish on pin 5. Sleeving and insulation between primary and secondary as required to meet requirements of double insulation. Primary leakage inductance (pins 5 and 8 shorted together) to be < 70 µH NIC part number: NLT181814W2NT128UT10P8C2F Hipot: 3 kV between pins 1,2 and pins 5,8 for 60 secs. Lead Breakout / Pinout Schematic (Bottom View – looking at pins) 1 N1 2 July 2008, Rev. 1 5 N2 4 5 3 6 2 7 1 8 Pins 6 & 7 Cropped flush with bobbin or removed 8 www.onsemi.com 4 DN06027/D Bill of Materials Ref. Part Type Qty. per Description Manufacturer 1 X2-class EMI suppression capacitor NIC C10 3.3nF, 250/275VAC 1µF, 16V 1 NIC C2 & C3 4.7µF, 400V 2 C4 220pF, 1kV 1 NIC C5 22µF, 16V 1 C6 1.0nF, 10V 1 Ceramic chip capacitor General purpose high voltage electrolytic Ceramic chip capacitor General purpose low voltage electrolytic Ceramic chip capacitor C7 1nF 1 Ceramic Y Capacitor Murata C8 & C9 470µF 2 Miniature low impedance electrolytic NIC D1 - D4 1N4007 4 D5 MBRA340 D6 MURA160 D7 C1 NIC NIC NIC Part No. Com m ent NPX332M275VX2 (Alt. SMD: NPX332M275VX2F) NMC1206X7R105K16 NREH4R7M400V10X16F (Alt. SMD: NACV4R7M400V10X10.8TR13F) NMC-H1210NP0221K1KVTRPF NRSA220M16V5X11F (Alt. SMD: NACE220M16V4X5.5TR13F) NMC0805X7R102K10 250VAC/275VAC X2 16V X7R 1kV 10V X7R DE1E3KX102MN4AL01 NRSH471M16V8X11.5F (Alt. SMD: NACK471M35V12.5X14TR13F) Y1 1N4007RLG 1000V 0.06Ohms 1 Axial Lead Standard Recovery Rectifier 1A, 1000V 40V 3A Schottky diode ON Semiconductor MBRA340T3G 1 600V 1A Ultrafast rectifier ON Semiconductor MURA160T3G 9V1 1 200mW SOD-323 Zener diode ON Semiconductor MM3Z9V1T1G 9.1V, 5% IC1 NCP1013 1 Self-Supplied Monolithic Sw itcher for ON Semiconductor Low Standby-Pow er Offline SMPS NCP1013ST100T3G NCP1013100T3G 100kHz IC2 HCPL-817 1 Opto-coupler HCPL-817 - Wide pitch Agilent HCPL-817-W0AE Wide pitch L1 1mH, 250mA 1 Pow er inductor Coilcraft ON Semiconductor Q1 BC857 1 General purpose PNP ON Semiconductor RFB0807-102L (Alt. SMD: NIC NPIS104T102KTRF) BC857ALT1G R1 15R, 1W 1 Axial lead carbon film resistor NIC NRC100J150TRF R2 91k, 1W 1 Axial lead carbon film resistor NIC NRC100J913TRF 1W R3 & R4 1.8R 2 Resistor thick film NRC NIC NRC25J1R8TR 0.33W R5 47R 1 Resistor thick film NRC NIC NRC10J470TR 0.125W R6 200R 1 Resistor thick film NRC NIC NRC10J201TR 0.125W TX1 Custom 1 5W Flyback transformer NIC NLT181814W2NT128UT10P8C2F 250mA 1W All parts can be ordered from Future Electronics Component locations Top view. July 2008, Rev. 1 Bottom view. www.onsemi.com 5 DN06027/D PCB Tracks Results Drain waveform at 110 VAC Drain waveform at 230 VAC I OUT vs VOUT Efficiency vs VOUT 0.9 80% 0.8 75% 0.7 70% 65% Efficiency IOUT (A) 0.6 0.5 0.4 0.3 230 VAC 0.2 110 VAC 0.1 60% 55% 50% 45% 230 VAC 40% 110 VAC 35% 0.0 30% 0.0 2.0 4.0 6.0 8.0 10.0 12.0 0.0 VOUT (V) July 2008, Rev. 1 2.0 4.0 6.0 8.0 10.0 12.0 V OUT (V) www.onsemi.com 6 DN06027/D 2 2 © 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 Anthony Middleton, e-mail: [email protected] July 2008, Rev. 1 www.onsemi.com 7