Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE Application Note Revision 1.1, 2012-08-03 Power Management & Multimarket Edition 2012-08-03 Published by Infineon Technologies AG 81726 Munich, Germany © 2012 Infineon Technologies AG All Rights Reserved. Legal Disclaimer The information given in this document shall in no event be regarded as a guarantee of conditions or characteristics. With respect to any examples or hints given herein, any typical values stated herein and/or any information regarding the application of the device, Infineon Technologies hereby disclaims any and all warranties and liabilities of any kind, including without limitation, warranties of non-infringement of intellectual property rights of any third party. Information For further information on technology, delivery terms and conditions and prices, please contact the nearest Infineon Technologies Office ( www.infineon.com). Warnings Due to technical requirements, components may contain dangerous substances. For information on the types in question, please contact the nearest Infineon Technologies Office. Infineon Technologies components may be used in life-support devices or systems only with the express written approval of Infineon Technologies, if a failure of such components can reasonably be expected to cause the failure of that life-support device or system or to affect the safety or effectiveness of that device or system. Life support devices or systems are intended to be implanted in the human body or to support and/or maintain and sustain and/or protect human life. If they fail, it is reasonable to assume that the health of the user or other persons may be endangered. AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE ICL8002G Revision History: 2012-08-03, Version 1.1 Previous Version: 1.0 Page Subjects (major changes since last revision) 15 Add “Production tolerance and distribution” Application Note 3 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 2 List of Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 Technical Specification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4 4.1 4.2 4.3 4.4 4.5 Demo Board Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Demo Board PCBA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 TRIAC Based Dimmer Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Single Stage Power Factor Correction . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . 7 Line Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5 5.1 5.1.1 5.1.2 5.2 5.3 5.4 5.5 5.6 5.7 5.7.1 5.7.2 5.7.3 5.8 5.9 5.9.1 5.9.2 5.10 Setup and Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . 8 Input / Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ,. . . . . . . . . . . . . . . . . . . . . . 8 Input . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Power Up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 MOSFET Operation Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Constant Output Power Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Output Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . 11 Input Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Phase Cut Dimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Test set-up . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Waveforms during dimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 List of compatible phase cut dimmers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 System Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Protection Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Output Open Circuit Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Output Short Circuit Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 Conducted EMI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 6 Production Tolerance and Normal Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 7 Board Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 8 8.1 8.2 BOM and Transformer Spec . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Bill of Material . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 9 Design Customization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 10 10.1 10.2 11 Common Questions and Troubleshooting Hints . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . 20 Q&A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 Troubleshooting hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . 20 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 Application Note 4 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 1 Introduction ICL8002G is a quasi-resonant PWM controller specially designed for high efficient offline LED driving application. It can be configured for different topologies such as flyback and buck converter. This demo board demonstrates its functions in dimmable LED bulb application with isolated flyback topology. Its quasi-resonant operation mode, primary side control, integrated PFC and phase-cut dimming control, and various protections make it an outstanding system solution for dimmable LED bulbs. Compared with ICL8001G demo board, the new ICL8002G demo board shows significant improvement in terms of dimming performance & output power and hence output current stability. The improvement in compatibility with TRIAC based phase cut dimmers has been achieved by adding damping and bleeding circuit blocks. The output power stability over a wide input voltage range has been increased by an additional line regulation circuit. Despite the additional circuit blocks the BOM still remains in a very competitive range. This demo board can be ordered with the sales code EVALLED-ICL8002G-B1. 2 • • • • • • • • • • List of Features Smooth dimming curve with high dimmer compatibility High efficiency (>85%) with quasi-resonant flyback operation Very high power factor with low THD (<20%) Compact single stage design Primary side control with high accuracy Tight lumen output tolerance Integrated power cell for short time to light Built-in digital soft-start Comprehensive protection functions Low system BOM cost for dimmable bulbs 3 Technical Specification Table 1 lists the performance specification of the EVALLED-ICL8002G-B1 demo board. The input voltage refers to the RMS voltage without modification by means of phase cut dimmer. Since this demo board solution is based on constant power control, the output power is fixed. As a result, the output current is determined by the output voltage, whose range is specified in the table below. Table 1 Design Specification Parameter Value Unit Input voltage 196-265 V Line frequency 50 Hz Input power 13 W Output power 11 W Output voltage 36-42 V Output current* 300 mA Power factor >0.9 THD <20% Efficiency** >85% *: Actual output current depends on output voltage **: Efficiency is measured at 230Vac with output of 38V/290mA Application Note 5 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 4 Demo Board Design 4.1 Demo Board PCBA Both top and bottom side of the demo board designed with ICL8002G are shown in Figure 1. Figure 1 EVALLED-ICL8002G-B1 demo board 4.2 Schematic Figure 2 shows the schematic for a 13W dimmable LED bulb application designed with ICL8002G. Figure 2 EVALLED-ICL8002G-B1 schematic Application Note 6 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 4.3 TRIAC Based Dimmer Compatibility TRIAC based dimmers can work smoothly with resistive loads such as incandescent lamps. When they work with non-resistive loads such as switch mode LED drivers, flickering issue can happen primarily due to insufficient hold-up current as well as current oscillation especially during TRIAC firing. Therefore, to improve the compatibility with TRIAC based dimmers, usually bleeder circuit and damping circuit are implemented in the LED drivers. In this design, a passive bleeder circuit formed by C1 and R4 is incorporated to maintain input current above the hold-up current threshold of the TRIAC. Two damping resistors, R1 and R6, are used to damp the oscillation as well as reduce inrush current. As the damping resistors can cause significant power loss, they can be bypassed shortly after the TRIAC firing so as to improve efficiency. This is achieved with circuit formed by R5, C2, and thyristor Q1. Each time when TRIAC turns on, due to the time delay produced by R5 and C2, thyristor Q1 will remain off and as a result the inrush current is limited by R6. When Q1’s gate voltage is charged to its triggering level, it will turn on and bypass R6. Thereafter Q1 will remain in conduction until the current drops below its holding current level at the end of each cycle. 4.4 Single Stage Power Factor Correction Single stage power factor correction (PFC) helps realizing highly efficient cost effective and compact LED driver design. In this demo board design, PFC is achieved with sensing the input mains voltage (via R8, R9, R12, and Q2 as shown in Figure 3) and regulating the peak current of the primary winding during each switching cycle to be approximately proportional to the voltage-sensing signal at VR pin of ICL8002G. As a result, input current is shaped to be more or less sinusoidal and thus high power factor is achieved, with input current harmonics fulfilling the requirements of EN 61000-3-2 standard. 4.5 Line Regulation The power factor correction scheme described above also indicates that with higher input voltage, the output power will increase due to higher primary current. To produce a constant power, the primary current should be smaller with higher input voltage. Therefore to produce a stable output power (and lumen output) versus mains voltage variations it is necessary to implement some compensation scheme to achieve good line regulation. In this design, the line regulation is achieved by the IC’s integrated foldback correction function as well as the circuitry formed by R13, C6, D1, and R14. C6, together with D1 and the auxiliary winding of the flyback transformer will produce a negative voltage which is proportional to the rectified input voltage. With choosing proper value of R13, the peak voltage level at the base of Q2, and thus VR pin’s voltage, will remain more or less constant against line voltage variation. The circuit formed by R10, R11 and ZD1 will add a DC offset to the base of Q2 so as to prevent it from going down to negative voltage. It will also determine the peak level of VR’s voltage and in turn determine the output power. The ZCV pin is able to detect the input voltage through R16 and the auxiliary winding and this allows IC to vary primary current sense voltage limit according to the input voltage. This means the primary current will be decreased when the input voltage increases. The extent of the compensation can be adjusted with varying the value of R16. Fine tuning of resistance value of R13 is necessary to provide optimum compensation to the line variation. As a rule of thumb, R13 can be calculated with the following formula. (1) where Naux and Np are the number of turns of the auxiliary winding and the primary winding respectively. Application Note 7 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 5 Setup and Results ATTENTION: LETHAL VOLTAGES ARE PRESENT ON THIS DEMO BOARD. DO NOT OPERATE THE BOARD UNLESS YOU ARE TRAINED TO HANDLE HIGH VOLTAGE CIRCUITS. DO NOT LEAVE THIS BOARD UNATTENDED WHEN IT IS POWERED UP. 5.1 Input / Output 5.1.1 Input Connect AC line (196V-265V) to the red (Live) and black (Neutral) wires. For dimming operation the phase cut dimmer should be connected to the input according to the dimmer’s instructions by its manufacturer. 5.1.2 Output Connect LED module (36V~42V/300mA) to the pink (positive) and white (negative) wires from the demo board. 5.2 Power Up The ICL8002G integrates a start-up cell to charge up the Vcc capacitor until it starts up successfully. Figure 3 demonstrates the start-up waveforms from mains voltage switch-on to light output. Start-up time of 350ms for a Vcc capacitance of C7 = 22uF is observed. Figure 3 Start-up: Rectified mains input voltage (C2, red), Controller Vcc (C1, yellow), output voltage (C3, blue), and output current (C4, green) Application Note 8 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 5.3 MOSFET Operation Waveforms The ICL8002G is a quasi-resonant PWM controller, which will turn on MOSFET when its drain voltage drops to the valley point. This helps to reduce current spike as well as switching loss and thus improve both efficiency and EMI performance. Figure 4 shows typical switching waveforms of the MOSFET Q1 on the primary side. Figure 4 Typical switching waveforms: Gate Drive voltage (C2, red), shunt signal VCS (C1, yellow) and Drain Source Voltage VDS (C3, blue) showing quasi-resonant switching 5.4 Constant Output Power Control This ICL8002G based single stage flyback solution produces constant output power against input voltage and output voltage variation. For LED bulb application, the output voltage variation is limited as the number of LEDs is fixed and this means the output current is relatively constant. Please refer to Figure 5 for the measured output power regulation characteristic. Output power variation vs. input voltage 12 11 10 Output Power (W) 9 8 7 6 5 4 3 2 1 0 185 205 225 245 265 Line Voltage (V) Figure 5 Output power vs. line voltage Application Note 9 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE With fixed output power, the LED load will operate at the point (current and voltage) where its I-V characteristic curve crosses the constant power curve. Figure 6 shows how the LED’s operating point is determined. I Constant power LED’s I‐V curve curve LED’s operating point ILED Vf 0 V LED Figure 6 LED operating point with constant power control Figure 7 shows the measured LED current versus line voltage. The maximum current deviation is limited to 2.5% across the whole input voltage range (196Vac-265Vac). 0.3 3.0% 0.25 2.0% 0.2 1.0% 0.15 0.0% 0.1 ‐1.0% 0.05 ‐2.0% Tolerance Output Current (A) Output current variation vs. input voltage Output current Current Tolerance ‐3.0% 0 185 205 225 245 265 Line Voltage (V) Figure 7 LED current vs. line voltage Compared with constant current control, which will produce higher output power with higher LED forward voltage, the constant power control allows stable output power regardless of LED forward voltage. As the system thermal design is mainly determined by the output power, high thermal design margin is not necessary due to stable output power. And this enables easy and optimized heatsink design and thus helps reduce system cost. Another benefit of constant power control is that it helps maintain constant lumen output versus LED module’s luminous tolerance and temperature variation. Application Note 10 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 5.5 Output Waveforms The single stage PFC design inevitably produces double mains frequency ripple at the output. Increasing output capacitance value helps reduce output ripple. However, this is often at the expense of the system’s form factor. In this demo board design, the output capacitor (C11 and C12) is sized for an output current ripple which exhibits no visible light modulation. Figure 8 shows the measured waveforms of output voltage and output current. The modulation depth of the current ripple is about 25%. Figure 8 Typical waveforms: Output voltage (C2, red) and output current (C4, green) 5.6 Input Waveforms Figure 9 shows the waveforms of input voltage, input current, and the current shunt voltage during normal operation at 230Vac and full load. The measured power factor is above 0.93 and the input current harmonics amplitudes fulfil the requirements of EN 61000-3-2 standard. Figure 9 Input voltage Vin (C3, blue), Input current Iin (C4, green) and shunt voltage Vcs (C2, red) Application Note 11 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 5.7 Phase Cut Dimming 5.7.1 Test set-up When evaluating dimming performance, the phase cut dimmer should be connected according to Figure 10. LED Module Offline LED Driver Vac AC Phase cut dimmer Designed with ICL8002G Figure 10 Phase cut dimming arrangement 5.7.2 Waveforms during dimming Figure 11 shows the waveforms of input voltage, input current, and the LED module’s current when the LED driver is operated with a leading edge phase cut dimmer. Figure 11 Input voltage Vin (C3, blue), Input current Iin (C4, green) and LED current (C1, yellow) 5.7.3 List of compatible phase cut dimmers Some phase cut dimmers tested with flickering free on this demo board are listed in Table 2. Table 2 Compatible phase cut dimmers tested at input 230 Vac / 13 W Manufacturer Model Type Power limit Dimming range BUSCH JAEGER 2200UJ-212 Leading edge 400 W 21– 100 % BUSCH JAEGER 2200 Leading edge 400 W 27 – 100 % Application Note 12 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE Table 2 Compatible phase cut dimmers tested at input 230 Vac / 13 W Manufacturer Model Type Power limit Dimming range BUSCH JAEGER 2247U Leading edge 500 W 23 – 100 % BUSCH JAEGER 2250U Leading edge 600 W 15 – 100 % CLIPSAL 32E450LM Leading edge 450 W 11 – 100 % CLIPSAL 32E450UDM Trailing edge 450 W 26 – 100 % CLIPSAL 4062E450UDM Trailing edge 450 W 26 – 100 % SIEMENS 5TC8 256 Leading edge 400 W 2 – 100 % SIEMENS 5TG0752-1NC1 Leading edge 400 W 27 – 100 % SIEMENS 5UH8022-3NC01 Leading edge 500 W 31 – 100 % LUMEO LICHTREGLER T10 Leading edge 300 W 1 – 100 % TCL NA Leading edge 630 W 1 – 100 % GZQS NA Leading edge 630 W 17 – 100 % NVC NA Leading edge 400 W 24 – 100 % OPPLE E068101 Leading edge 300 W 1 – 100 % PDL CAT634LM Leading edge 450 W 17 – 100 % MANK NA Leading edge 200 W 24 – 100 % FLEXALITE NA Leading edge 630 W 3 – 100 % DIGITRAC NA Leading edge 400 W 14 – 100 % HPM 400T Trailing edge 400 W 1 – 100 % BERKER 23010 Leading edge 400 W 21 – 100 % OPUS 852.39 Leading edge 400 W 19 – 100 % 5.8 System Efficiency Figure 12 shows the LED driver system’s efficiency versus line voltage, which exhibits high efficiency (>84%) over the whole input voltage range due to the quasi-resonant operation. Efficiency vs. input voltage 90.0% Efficiency 88.0% 86.0% 84.0% 82.0% 80.0% 185 205 225 245 265 Line Voltage (V) Figure 12 LED Driver efficiency vs. input voltage Application Note 13 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 5.9 Protection Functions The protection functions listed in Table 3 are provided with ICL8002G. Table 3 ICL8002G protection functions VCC Overvoltage Auto Restart Mode VCC Undervoltage Auto Restart Mode Output Overvoltage Latched Off Mode Output Short Circuit Auto Restart Mode Short Winding Latched Off Mode Over temperature Auto Restart Mode 5.9.1 Output Open Circuit Protection When the output is left open during operation, the output voltage will rise and accordingly the voltage produced by the auxiliary winding when MOSFET turns off will increase. This voltage is detected by ZCV pin of ICL8002G via R16 and R17. Output overvoltage protection will be triggered once this voltage reaches the OVP threshold (Vzcovp = 3.7V) and IC will go into Latched Off Mode. On the other hand, the voltage produced by the auxiliary winding will supply to Vcc and Vcc overvoltage protection will be triggered if it reaches the threshold (Vvccovp = 25V). In this demo board design, Vcc overvoltage protection will be triggered when the output is left open and IC will go into Auto Restart Mode. The power consumption during Auto Restart Mode is below 0.5W. 5.9.2 Output Short Circuit Protection In the case of an output short circuit, the IC will switch to Auto Restart Mode by means of VCC undervoltage detection. Total input power consumption in this mode is kept well below 1W. 5.10 Conducted EMI The conducted EMI test is performed at 230Vac with full load condition. The EMI’s peak value is plotted against quasi-peak limit of the EN55015(CISPR15). There is approximately 10dB margin observed. Live Figure 13 Tested at 230Vac with full load (Live). EN55015 B limit. Application Note 14 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE Neutral Figure 14 Tested at 230Vac with full load (Neutral). EN55015 B limit. 6 Production Tolerance and Normal Distribution In total 72 demo board samples have been tested and the output power of each board was recorded at the o same test condition (line voltage of 230Vac and ambient temperature of 25 C) to check the production tolerance, which is contributed by both the IC and external components tolerance. Figure 15 shows the distribution data of output power. The result indicted that the output power tolerance is within +3%, and standard deviation is 0.15W. Figure 15 Production variation of output power (board to board deviation) Application Note 15 Version 1.1, 2012-08-03 2 5 . 6 m m AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 7 Board Layout A single layer PCB with 0.8mm thickness is used for this demo board. The maximum height of the demo board (at C11) is 23.2mm. It is able to fit into many different lamp fixtures like A19 bulb and PAR30. This demo board is designed to meet UL safety standard for galvanic isolation but was not submitted for safety certification. 39.1mm 15.4mm 15.1mm 58.2mm Figure 16 EVALLED-ICL8002G-B1 - Top Layer Figure 17 EVALLED-ICL8002G-B1 - Bottom Layer Application Note 16 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 8 BOM and Transformer Spec 8.1 Bill of Material Number Reference Value Description Package Part Number Manufacturer 1 U1 ICL8002G LED DRIVER IC 2 BR1 600V 0.5A Bridge Diode SO8 ICL8002G INFINEON TO-269AA MB6S-E3/80 3 C1 275VAC 0.15uF Film Cap, 10mm Pitch VISHAY R46KF315000P0M 4 C2 50V 150nF MLCC, X7R 0603 C0603C154K5RACTU KEMET KEMET 5 C3 630V 15nF MLCC, X7R 1206 GRM31CR72J153KW03L MURATA 6 C4 520V 0.15uF Film Cap, 15mm Pitch B32672Z5154K EPCOS 7 C5 50V 10nF MLCC, X7R 0603 GRM188R71H103KA01D MURATA 8 C6 50V 4.7uF MLCC, X7R 1206 GRM31CR71H475KA12L MURATA 9 C7 25V 22uF MLCC, X7R 1210 GRM32ER71E226KE15L MURATA 10 C8 50V 330pF MLCC, X7R 0603 C1608X7R1H331K TDK 11 C10 250V 1nF MLCC, X7R 0805 C0805C102KARACTU KEMET 12 C11 50V 180uF Electrolytic Cap, Lo=9000H 8 x 20 EEUFR1H181L PANASONIC 13 C12 50V 120uF Electrolytic Cap, Lo=8000H 8 x 15 EEUFR1H121L PANASONIC 14 C13 250VAC 2.2nF Ceramic Cap, Dielectric Str 4kV DE1E3KX222M MURATA 15 D1,D2 75V 0.2A Switching Diode SOD323 BAS16HT1G ONSEMI 16 D4 150V 3A Schottky Diode SMB STPS3150U ST 17 F1 250V 5A Fuse, Fast Acting 0263005.MXL LITTELFUSE 18 JP2, JP3 19 L1 45mH 0.18A Common mode choke 750311650 Würth Elektronik 20 L2 1.5mH 0.19A Filter Choke 7447462152 Würth Elektronik 21 Q1 600V 0.8A SCR TO92 MCR100-8 ONSEMI 22 Q2 45V 0.1A NPN Transistor SOT23 BC857B INFINEON 23 Q3 800V 2A MOSFET DPAK SPD02N80C3 INFINEON 24 R1 100R 2W Metal Film Resistor, 5% 4 x 10 MFP2-100R JI WELWYN 25 R4 1.2kOhm 2W Metal Film Resistor, 5% 4 x 10 MFP2-1K2 JI WELWYN 26 R5 1MOhm 1W Metal Film Resistor, 5% 2.5 x 6.2 MFP1-1M JI WELWYN 27 R6 100R 1W Metal Film Resistor, 5% 2.5 x 6.2 MFP1-100R JI WELWYN 28 R7 4.7kOhm Metal Film Resistor 1% 0805 29 R8 1.1MOhm Metal Film Resistor, 1% 1206 30 R9 1MOhm Metal Film Resistor, 1% 1206 31 R10 5.1kOhm Metal Film Resistor, 1% 0805 32 R11 82kOhm Metal Film Resistor, 1% 0603 33 R12 25.5kOhm Metal Film Resistor, 1% 0603 34 R13 160kOhm Metal Film Resistor, 1% 0603 35 R14, R15, R19 10R Metal Film Resistor, 1% 0805 36 R16 20kOhm Metal Film Resistor, 1% 0603 37 R17 3.3kOhm Metal Film Resistor, 1% 0603 38 R20 2R Metal Film Resistor, 1% 0805 39 R21 56kOhm Metal Film Resistor, 1% 0805 40 R23 0R Metal Film Resistor, 1% Transformer, Lp = 3.9mH, 0805 Jumper, Lead Dia = 0.6mm 41 T1 Np:Ns:Naux = 139:24:12 EF20 750845151 Würth Elektronik 42 VR1 470V Varistor,19J, 300Vrms 5mm Disc MCFT000231 Multicomp 43 ZD1 15V Zener Diode, 2% SOD323 PDZ15B,115 NXP 44 ZD2 4.7V Zener Diode, 2% SOD323 PDZ4.7B,115 NXP Figure 18 Bill Of Material Application Note 17 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 8.2 Transformer Figure 19 EVALLED-ICL8002G-B1 Transformer Design Application Note 18 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 9 Design Customization To facilitate design customization for different output voltage and/or output current than given in this demo board, Infineon offers an interactive online design solution, the Infineon Light Desk. With this cloud-based design tool, users are able to specify the system requirements, create the schematic and BOM, run simulation, and generate a design summary report. Users are advised to verify and tune the design for key performances such as efficiency, PF, EMI, and dimming compatibility with prototyping before finalizing their product design. Figure 20 and Figure 21 show some snap shots of the Infineon Light Desk. Figure 20 Infineon Light Desk - Selection of solutions Figure 21 Infineon Light Desk - Interactive web schematic Application Note 19 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE 10 Common Questions and Troubleshooting Hints 10.1 Q&A How does ICL8002G realize dimming control and power factor correction? Both dimming control and PFC are achieved with the input mains voltage sensing with the VR pin. This signal is used to set the peak current of the primary winding and consequently allows for both PFC and phase-cut dimming functionality by regulating the cycle energy. How does the ICL8002G regulate the output LED current? ICL8002G does not regulate the output current directly. Instead it produces a constant output power. The LED load will operate at the point (current and voltage) where its I-V characteristic curve crosses the constant power curve. Is it possible to test the demo board with different LED modules with big variations in total forward voltages? The operation range of output voltage is specified in Table 1. The demo board will switch into protection mode when tested with LED load with out-of-range forward voltage either due to Vcc overvoltage protection or Vcc undervoltage protection. Modification on the transformer design is necessary for applications with different output voltage. What will happen under no-load conditions? Under no-load conditions this demo board will go into auto restart mode with output voltage reaches higher than 45V. It is therefore advised to connect proper LED loads before switching on the power. 10.2 Troubleshooting hints Why is there no light output after the LED load is connected and power is on? Please verify the following: • • • • Connectivity of AC input and LED load LED module’s polarity Whether LED module’s forward voltage is out of the range specified in Table 1 Conductivity of fuse How to change output current? With fixed LED load, the output current is proportional to output power, which is a function of primary current. Therefore by adjusting the VR pin’s voltage and shunt resistor the desired output current can be set. However, great care must be taken to ensure that the transformer is not driven into saturation with high primary current. Moreover, the VR pin’s voltage should be kept below 3.7V for maximum power factor. How to change the open circuit protection mode to Latched Off Mode? If Latched Off Mode is preferred for output open circuit protection, R16 and/or R17 can be adjusted so that OVP threshold (Vzcovp = 3.7 V) is reached first before the Vcc overvoltage threshold (Vvccovp = 25V) is reached. Please note that with changing R16, the voltage foldback correction will be affected and as a result the line regulation will be affected. In this case R13 can be tuned for better line regulation. Why is the LED flickering in my dimming application? How to improve? Flickering can be either caused by IC auto-restart or by dimmer's uneven conduction phase angle. For the autorestart case, the ICL8002G’s Vcc voltage should be maintained between Vvccovp and Vvccoff over the whole dimming range. This can be achieved by proper transformer turn ratio design and, if necessary, a voltage regulation circuit for the Vcc. For dimmer’s uneven conduction case, it is advised to tune the damping and bleeder circuits. Application Note 20 Version 1.1, 2012-08-03 AN-EVALLED-ICL8002G-B1 Phase Cut Dimmable Isolated Flyback Converter for LED Retrofit Bulb with ICL8002G & CoolMOS™ 800V CE How to further improve efficiency? Efficiency can be improved by reducing the value of damping resistors R1 and R6, and bleeder capacitor C1. However the dimming performance may be affected. Switching frequency can be reduced so as to minimize the switching loss and this may require bigger transformer size. Low ESR capacitor can be used for the output capacitor to improve efficiency. Using a higher current rated MOSFET for Q3, however, may not necessarily produce higher efficiency as the switching loss may dominate the total power loss of the MOSFET. How to improve power factor and THD? Reducing capacitance value of C1 and C4 can help to increase power factor and to reduce THD. Do note that both dimming and EMI performance can be affected. Increasing reflection voltage of the transformer can also help to improve power factor. Care must be taken to ensure the MOSFET Q3’s breakdown voltage is not exceeded under worst case operation. How to reduce BOM cost? For low cost application, the active damper circuit formed by R5, R6, C2, and thyristor Q1 can be removed. A 600V rated MOSFET can be used for Q3 and this requires the transformer to be designed with lower reflection voltage and as a result power factor may be reduced. 11 References ICL8002G Datasheet at www.infineon.com/ledoffline Design Guidelines for ICL8001G/ICLS8082G at www.infineon.com/ledoffline Infineon Light Desk at www.infineon.com/lightdesk Application Note 21 Version 1.1, 2012-08-03 www.infineon.com Published by Infineon Technologies AG