National Semiconductor Application Note 2069 Montu Doshi November 23, 2010 Introduction Key Features This demonstration board highlights the performance of a LM3445 based Flyback LED driver solution that can be used to power a single LED string consisting of 4 to 10 series connected LEDs from an 180 VRMS to 265 VRMS, 50 Hz input power supply. The key performance characteristics under typical operating conditions are summarized in this application note. This is a four-layer board using the bottom and top layer for component placement. The demonstration board can be modified to adjust the LED forward current, the number of series connected LEDs that are driven and the switching frequency. Refer to the LM3445 datasheet for detailed instructions. A bill of materials is included that describes the parts used on this demonstration board. A schematic and layout have also been included along with measured performance characteristics. • • • • Drop-in compatibility with TRIAC dimmers Line injection circuitry enables PFC values greater than 0.94 Adjustable LED current and switching frequency Flicker free operation Applications • • • • Retro-fit TRIAC Dimming Solid State Lighting Industrial and Commercial Lighting Residential Lighting Performance Specifications Based on an LED Vf = 3.4V Symbol Parameter Min Typ Max VIN Input voltage 180 VRMS 230 VRMS 265 VRMS VOUT LED string voltage 13 V 20 V 27 V ILED LED string average current - 350 mA - POUT Output power - 7.2 W - fsw Switching frequency - 67 kHz - Demo Board LM3445 - 230VAC, 6W- 15W Isolated Flyback LED Driver LM3445 - 230VAC, 6W- 15W Isolated Flyback LED Driver Dimming Characteristics 30126904 30126924 AN-2069 © 2010 National Semiconductor Corporation 301269 www.national.com AN-2069 LM3445 230VAC, 8W Isolated Flyback LED Driver Demo Board Schematic 30126901 Warning: The LM3445 evaluation board has exposed high voltage components that present a shock hazard. Caution must be taken when handling the evaluation board. Avoid touching the evaluation board and removing any cables while the evaluation board is operating. Warning: The ground connection on the evaluation board is NOT referenced to earth ground. If an oscilloscope ground lead is connected to the evaluation board ground test point for analysis and the mains AC power is applied (without any isolation), the fuse (F1) will fail open. For bench evaluation, either the input AC power source or the bench measurement equipment should be isolated from the earth ground connection. Isolating the evaliation board (using 1:1 isolation line isolation transformer) rather than the oscilloscope is highly recommended. Warning: The LM3445 evaluation board should not be powered with an open load. For proper operation, ensure that the desired number of LEDs are connected at the output before applying power to the evaluation board. www.national.com 2 AN-2069 LM3445 Device Pin-Out 30126902 Pin Description 10 Pin MSOP Pin # Name Description 1 ASNS PWM output of the triac dim decoder circuit. Outputs a 0 to 4V PWM signal with a duty cycle proportional to the triac dimmer on-time. 2 FLTR1 First filter input. The 120Hz PWM signal from ASNS is filtered to a DC signal and compared to a 1 to 3V, 5.85 kHz ramp to generate a higher frequency PWM signal with a duty cycle proportional to the triac dimmer firing angle. Pull above 4.9V (typical) to tri-state DIM. 3 DIM Input/output dual function dim pin. This pin can be driven with an external PWM signal to dim the LEDs. It may also be used as an output signal and connected to the DIM pin of other LM3445 or LED drivers to dim multiple LED circuits simultaneously. 4 COFF OFF time setting pin. A user set current and capacitor connected from the output to this pin sets the constant OFF time of the switching controller. 5 FLTR2 Second filter input. A capacitor tied to this pin filters the PWM dimming signal to supply a DC voltage to control the LED current. Could also be used as an analog dimming input. 6 GND Circuit ground connection. 7 ISNS LED current sense pin. Connect a resistor from main switching MOSFET source, ISNS to GND to set the maximum LED current. 8 GATE Power MOSFET driver pin. This output provides the gate drive for the power switching MOSFET of the buck controller. 9 VCC 10 BLDR Input voltage pin. This pin provides the power for the internal control circuitry and gate driver. Bleeder pin. Provides the input signal to the angle detect circuitry as well as a current path through a switched 230Ω resistor to ensure proper firing of the triac dimmer. 3 www.national.com AN-2069 Bill of Materials Designator AA1 Description Manufacturer Printed Circuit Board Part Number RoHS - Y U1 Triac Dimmable Offline LED Driver, PowerWise National Semiconductor LM3445MM Y C1 Ceramic, X7R, 250VAC, 10% Murata Electronics North America DE1E3KX332MA5BA01 Y C2 Ceramic, Polypropylene, 400VDC, 10% WIMA MKP10-.033/400/5P10 Y C3 CAP, CERM, 330pF, 630V, +/-5%, C0G/NP0, 1206 TDK C3216C0G2J331J Y C4 Ceramic, X7R, 250V, X2, 10%, 2220 Murata Electronics North America GA355DR7GF472KW01L Y C5 CAP, Film, 0.033µF, 630V, +/-10%, TH EPCOS Inc B32921C3333K Y C6 CAP, CERM, 0.015µF, 500V, +/-10%, X7R, 1812 Vishay/Vitramon VJ1812Y223KBEAT4X Y C7-DNP CAP, CERM, 0.1µF, 630V, +/-10%, X7R, 1812 MuRata GRM43DR72J104KW01L Y C8 CAP, CERM, 0.1µF, 630V, +/-10%, X7R, 1812 MuRata GRM43DR72J104KW01L Y CAP, CERM, 1µF, 50V, +/-10%, X7R, 1210 MuRata GRM32RR71H105KA01L Y C10 CAP, CERM, 0.47µF, 50V, +/-10%, X7R, 0805 MuRata GRM21BR71H474KA88L Y C12 Aluminium Electrolytic, 680uF, 35V, 20%, Nichicon UHE1V681MHD6 Y C13 CAP, CERM, 1µF, 35V, +/-10%, X7R, 0805 Taiyo Yuden GMK212B7105KG-T Y C14 CAP, CERM, 0.1µF, 25V, +/-10%, X7R, 0603 MuRata GRM188R71E104KA01D Y C15 CAP, TANT, 47uF, 16V, +/-10%, 0.35 ohm, 6032-28 SMD AVX TPSC476K016R0350 Y C16 CAP, CERM, 0.47µF, 16V, +/-10%, X7R, 0603 MuRata GRM188R71C474KA88D Y C17 CAP, CERM, 0.22µF, 16V, +/-10%, X7R, 0603 TDK C1608X7R1C224K Y C18 CAP, CERM, 2200pF, 50V, +/-10%, X7R, 0603 MuRata GRM188R71H222KA01D Y C20 CAP, CERM, 330pF, 50V, +/-5%, C0G/NP0, 0603 MuRata GRM1885C1H331JA01D Y D1 DIODE TVS 250V 600W UNI 5% SMD Littelfuse P6SMB250A Y D2 Diode, Switching-Bridge, 600V, 0.8A, MiniDIP Diodes Inc. HD06-T Y D3 Diode, Silicon, 1000V, 1A, SOD-123 Comchip Technology CGRM4007-G Y D4 Diode, Schottky, 100V, 1A, SMA STMicroelectronics STPS1H100A Y Diode, Zener, 13V, 200mW, SOD-323 Diodes Inc DDZ13BS-7 Y Diode, Zener, 36V, 550mW, SMB ON Semiconductor 1SMB5938BT3G Y Diode, Schottky, 100V, 150 mA, SOD-323 STMicroelectronics BAT46JFILM Y Fuse, 500mA, 250V, Time-Lag, SMT Littelfuse Inc 0443.500DR Y H1, H2, H5, H6 Standoff, Hex, 0.5"L #4-40 Nylon Keystone 1902C Y H3, H4, H7, H8 Machine Screw, Round, #4-40 x 1/4, Nylon, Philips panhead B&F Fastener Supply NY PMS 440 0025 PH Y C9, C11 D5, D10 D6 D7, D8, D9 F1 J1, J2 Conn Term Block, 2POS, 5.08mm PCB Phoenix Contact 1715721 Y L1, L2 Inductor, Radial Lead Inductors, Shielded, 4.7mH, 130mA, 12.20ohm, 7.5mm Radial, TDK Corporation TSL0808RA-472JR17-PF Y Terminal, 22 Gauge Wire, Terminal, 22 Guage Wire 3M 923345-02-C Y Q1 MOSFET, N-CH, 600V, 200mA, SOT-223 Fairchild Semiconductor FQT1N60CTF_WS Y Q2 Transistor, NPN, 300V, 500mA, SOT-23 Diodes Inc. MMBTA42-7-F Y Q3 MOSFET, N-CH, 650V, 800mA, IPAK Infineon Technologies SPU01N60C3 Y Q4 MOSFET N-CH 100V 170MA SOT23-3 Diodes Inc. BSS123-7-F Y LED+, LED-, TP7, TP8 R1 RES, 221 ohm, 1%, 0.25W, 1206 Vishay-Dale CRCW1206221RFKEA Y R2, R7 RES, 200k ohm, 1%, 0.25W, 1206 Vishay-Dale CRCW1206200KFKEA Y R3, R8 RES, 309k ohm, 1%, 0.25W, 1206 Vishay-Dale CRCW1206309KFKEA Y www.national.com 4 Description Manufacturer Part Number RoHS R4, R12 RES, 10k ohm, 5%, 0.25W, 1206 Vishay-Dale CRCW120610K0JNEA Y R5-DNP RES, 680 ohm, 5%, 1W, 2512 Vishay/Dale CRCW2512680RJNEG Y R6 RES, 820 ohm, 5%, 1W, 2512 Vishay/Dale CRCW2512820RJNEG Y R10 RES, 430 ohm, 5%, 1W, 2512 Vishay/Dale CRCW2512430RJNEG Y R11 RES, 49.9k ohm, 1%, 0.125W, 0805 Vishay-Dale CRCW080549K9FKEA Y R13 RES, 33.0 ohm, 1%, 0.25W, 1206 Vishay-Dale CRCW120633R0FKEA Y R14 RES, 10 ohm, 5%, 0.125W, 0805 Vishay-Dale CRCW080510R0JNEA Y R15 RES, 10.0k ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW060310K0FKEA Y R16 RES, 280k ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW0603280KFKEA Y R17 RES, 475k ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW0603475KFKEA Y R18 RES, 49.9k ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW060349K9FKEA Y R19 RES, 10 ohm, 5%, 0.1W, 0603 Vishay-Dale CRCW060310R0JNEA Y R20 RES, 1.91k ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW06031K91FKEA Y R21 RES, 2.70 ohm, 1%, 0.25W, 1206 Panasonic ERJ-8RQF2R7V Y R22 RES, 10.7 ohm, 1%, 0.125W, 0805 Vishay-Dale CRCW080510R7FKEA Y R23 RES, 324k ohm, 1%, 0.1W, 0603 Vishay-Dale CRCW0603324KFKEA Y RT1, RT2 Current Limitor Inrush, 60Ohm, 20%, 5mm Raidal Cantherm MF72-060D5 Y T1 FLBK TFR, 2.07 mH, Np=140T, Ns=26T, Na= 20T Wurth Elektornik 750815040 REV 1 Y Terminal, Turret, TH, Double Keystone Electronics 1502-2 Y Varistor 275V 55J 10mm DISC EPCOS Inc Y TP9, TP10 VR1 5 S10K275E2 www.national.com AN-2069 Designator AN-2069 Transformer Design Mfg: Wurth Electronics, Part #: 750815040 Rev. 01 30126909 Parameter Test Conditions Value D.C. Resistance (3-1) 20°C 1.91 Ω ± 10% D.C. Resistance (6-4) 20°C 0.36 Ω ± 10% D.C. Resistance (10-13) 20°C Inductance (3-1) 10 kHz, 100 mVAC 0.12 Ω ± 10% 2.12 mH ± 10% Inductance (6-4) 10 kHz, 100 mVAC 46.50 µH ± 10% Inductance (10-13) 10 kHz, 100 mVAC 74.00 µH ± 10% Leakage Inductance (3-1) 100 kHz, 100 mAVAC (tie 6+4, 10+13) 18.0 µH Typ., 22.60 µH Max. Dielectric (1-13) tie (3+4), 4500 VAC, 1 second 4500 VAC, 1 minute www.national.com Turns Ratio (3-1):(6-4) 7:1 ± 1% Turns Ratio (3-1):(10:13) 5.384:1 ± 1% 6 AN-2069 Demo Board Wiring Overview 30126903 Wiring Connection Diagram Test Point Name I/O Description TP8, TP10 LED + Output LED Constant Current Supply Supplies voltage and constant-current to anode of LED string. TP7, TP9 LED - Output LED Return Connection (not GND) Connects to cathode of LED string. Do NOT connect to GND. J1-1 LINE Input AC Line Voltage Connects directly to AC line or output of TRIAC dimmer of a 230VAC system. J1-2 NEUTRAL Input AC Neutral Connects directly to AC neutral of a 230VAC system. Demo Board Assembly 30126905 Top View 30126906 Bottom View 7 www.national.com (Note 1, Note 2, Note 3) Efficiency vs. Line Voltage Original Circuit 0.83 8 LEDs Efficiency vs. Line Voltage Modified Circuits 10 LEDs 0.97 0.81 EFFICIENCY EFFICIENCY 0.82 6 LEDs 0.80 0.79 4 LEDs 0.93 Mod C (10 LEDs) 0.89 Mod B (8 LEDs) 0.85 0.81 0.77 0.73 0.78 0.68 Original (6 LEDs) Mod A (4 LEDs) 0.77 0.64 0.76 180 190 200 210 220 230 240 250 260 0.60 180 190 200 210 220 230 240 250 260 INPUT VOLTAGE (VRMS) INPUT VOLTAGE (VRMS) 30126910 30126914 LED Current vs. Line Voltage Original Circuit LED Current vs. Line Voltage Modified Circuits 600 650 LED CURRENT (mA) LED CURRENT (mA) 450 550 4 LEDs 550 6 LEDs 350 250 8 LEDs 150 500 450 Mod C (10 LEDs) Mod B (8 LEDs) 400 350 300 250 200 150 10 LEDs Original (6 LEDs) Mod A (4 LEDs) 100 180 190 200 210 220 230 240 250 260 50 180 190 200 210 220 230 240 250 260 INPUT VOLTAGE (VRMS) INPUT VOLTAGE (VRMS) 30126911 30126915 Power Factor vs. Line Voltage Original Circuit Power Factor vs. Line Voltage Modified Circuits 0.956 10 LEDs 0.97 0.952 8 LEDs 0.93 0.944 4 LEDs 0.940 0.936 POWER FACTOR 0.948 POWER FACTOR AN-2069 Typical Performance Characteristics 6 LEDs 0.932 0.89 0.85 0.81 0.77 0.73 Mod C (10 LEDs) Mod B (8 LEDs) Original (6 LEDs) Mod A (4 LEDs) 0.928 0.68 0.924 0.64 0.920 180 190 200 210 220 230 240 250 260 0.60 180 190 200 210 220 230 240 250 260 INPUT VOLTAGE (VRMS) INPUT VOLTAGE (VRMS) 30126912 www.national.com 30126916 8 Output Power vs. Line Voltage Modified Circuits 12 10 9 8 25.0 22.5 10 LEDs 8 LEDs OUTPUT POWER (W) OUTPUT POWER (W) 11 AN-2069 Output Power vs. Line Voltage Original Circuit 4 LEDs 7 6 LEDs 6 5 4 20.0 Mod B (8 LEDs) 17.5 15.0 Mod C (10 LEDs) 12.5 10.0 7.5 5.0 3 2.5 2 180 190 200 210 220 230 240 250 260 Original (6 LEDs) 0.0 180 190 200 210 220 230 240 250 260 Mod A (4 LEDs) LINE VOLTAGE (VRMS) INPUT VOLTAGE (VRMS) 30126913 30126917 Line Voltage and Line Current (VIN = 230VRMS, 6 LEDs, ILED = 350mA) Output Voltage and LED Current (VIN = 230VRMS, 6 LEDs, ILED = 350mA) 30126918 30126920 Ch1: Line Voltage (100 V/div); Ch3: Line Current (20 mA/div); Time (4 ms/div) Ch1: Output Voltage (10 V/div); Ch3: LED Current (100 mA/div); Time (4 ms/div) Power MOSFET Drain and ISNS (Pin-7) Voltage (VIN = 230VRMS, 6 LEDs, ILED = 350mA) FLTR2 (Pin-5) and ISNS (Pin-7) Voltage (VIN=230VRMS, 6 LEDs, ILED = 350mA 30126921 30126922 Ch1: Drain Voltage (100V/div); Ch4: ISNS Voltage (500 mV/div); Time (4 µs/div) Ch1: FLTR2 Voltage (200 mV/div); ISNS Voltage (200 mV/div); Time (4 µs/div) Note 1: Original Circuit (6 LEDs operating at 350mA): R21 = 2.7Ω; Modification A (10 LEDs operating at 375mA): R21 = 1.8Ω; Modification B (8 LEDs operating at 350mA): R21 = 2.2Ω; Modification C (4 LEDs operating at 315mA): R21 = 3.9Ω Note 2: The output power can be varied to acheive desired LED current by interpolating R14 values between the maximum of 3.9 Ω and minimum of 1.8 Ω Note 3: The maximum output voltage is clamped to 36 V. For operating LED string voltage > 36 V, replace D6 with suitable alternative 9 www.national.com AN-2069 PCB Layout 30126907 Top Layer 30126908 Bottom Layer www.national.com 10 The LED driver is designed to accurately emulate an incandescent light bulb and therefore behave as an emulated resistor. The resistor value is determined based on the LED string configuration and the desired output power. The circuit then operates in open-loop, with a fixed duty cycle based on a constant on-time and constant off-time that is set by selecting appropriate circuit components. Like an incandescent lamp, the driver is compatible with both forward and reverse phase dimmers. NON-DIMMING PERFORMANCE In steady state, the LED string voltage is measured to be 20.5 V and the average LED current is measured as 350 mA. The 100 Hz current ripple flowing through the LED string was MEASURED EFFICIENCY AND LINE REGULATION (6 LEDS, NO TRIAC DIMMER) VIN (VRMS) IIN (mARMS) PIN(W) VOUT (V) ILED (mA) POUT (W) 180 31.73 5.35 19.67 221.64 4.36 Efficiency (%) Power Factor 81.4 0.9375 190 33.39 5.96 19.85 244.82 4.86 81.5 0.9394 200 35.11 6.61 20.04 269.16 5.39 81.6 0.9493 210 36.85 7.30 20.22 294.82 5.96 81.6 0.9493 220 38.53 8.01 20.40 321.26 6.55 81.8 0.9451 230 40.18 8.75 20.56 348.70 7.17 82.0 0.9463 240 41.75 9.50 20.74 375.70 7.79 82.0 0.9477 250 43..39 10.30 20.90 404.82 8.46 82.1 0.9490 260 45.07 11.14 21.05 434.48 9.15 82.0 0.9500 TRIAC dimmer and measuring the corresponding input and output parameters, the dimming performance of the demonstration board driving 6 LEDs is summarized in the table below. DIMMING PERFORMANCE The LED driver is capable of matching or exceeding the dimming performance of an incandescent lamp. Using a simple rotary TRIAC dimmer, smooth and near logarithmic dimming performance is achieved. By varying the firing angle of the MEASURED DIMMING PERFORMANCE VIN (VRMS) VO (V) ILED (mA) POUT (W) 229.39 20.51 343.1 7.04 220.47 20.35 320.8 6.53 210.24 20.16 294.8 5.94 199.05 19.98 266.8 5.33 190.32 19.80 245.8 4.87 180.33 19.61 222.7 4.37 170.51 19.42 200.1 3.89 156.39 19.31 187.4 3.62 149.11 19.15 171.6 3.29 140.35 18.97 154.0 2.92 129.61 18.75 133.1 2.50 119.7 18.53 115.3 2.14 110.17 18.33 99.1 1.82 100.55 18.11 83.5 1.51 90.75 17.87 68.8 1.23 79.72 17.59 53.1 0.93 70.42 17.34 40.8 0.71 60.91 17.08 30.1 0.81 49.94 16.77 19.8 0.33 45.04 16.64 16.0 0.27 11 www.national.com AN-2069 measured to be 194 mApk-pk at full load. The magnitude of the ripple is a function of the value of energy storage capacitors connected across the output port and the TRIAC firing angle. The ripple current can be reduced by increasing the value of energy storage capacitor or by increasing the LED string voltage. With TRIAC dimmers, the ripple magnitude is directly proportional to the input power and therefore reduces at lower LED current. The LED driver switching frequency is measured to be close to the specified 67 kHz. The circuit operates with a constant duty cycle of 0.21 and consumes near 8.75 W of input power. The driver steady state performance for an LED string consisting of 6 series LEDs without using a triac dimmer is summarized in the following table. Experimental Results AN-2069 30126924 Dimming Characteristics CURRENT THD of the fundamental current (as shown in the following figure) and therefore meets the requirements of the IEC 61000-3-2 The LED driver is able to achieve close to unity power factor Class-3 standard. (P.F. ~ 0.94) which meets Energy Star requirements. This design also exhibits low current harmonics as a percentage 30126923 Current Harmonic vs. EN/IEC61000-3-2 Class C Limits www.national.com 12 AN-2069 Circuit Operation With Rotary Forward Phase Triac Dimmer Input waveforms at full brightness setting Output waveforms at full brightness setting 30126925 30126928 Ch1: Input Voltage (100 V/div); Ch3: Input Current (20 mA/div); Time (4 ms/div) Ch1: Output Voltage (10 V/div); LED Current (100 mA/div); Time (4 ms/div) Input waveforms at half brightness setting (90° firing angle) Output waveforms at half brightness setting (90° firing angle) 30126926 30126929 Ch1: Input Voltage (100 V/div); Ch3: Input Current (20 mA/div); Time (4 ms/div) Ch1: Output Voltage (10 V/div); LED Current (100 mA/div); Time (4 ms/div) Input waveforms at minimum brightness setting Output waveforms at minimum brightness setting 30126927 30126930 Ch1: Input Voltage (100 V/div); Ch3: Input Current (20 mA/div); Time (4 ms/div) Ch1: Output Voltage (10 V/div); LED Current (100 mA/div); Time (4 ms/div) 13 www.national.com AN-2069 Electromagnetic Interference (EMI) The EMI input filter of this evaluation board is configured as shown in the following circuit diagram. 30126931 FIGURE 1. Input EMI Filter and Rectifier Circuit In order to get a quick estimate of the EMI filter performance, only the PEAK conductive EMI scan was measured and the data was compared to the Class B conducted EMI limits published in FCC – 47, section 15.(Note 4) 30126932 FIGURE 2. Peak Conductive EMI scan per CISPR-22, Class B Limits Note 4: CISPR 15 compliance pending www.national.com 14 AN-2069 ILED = 348 mA # of LEDs = 6 POUT = 7.2 W The results are shown in the following figures. Thermal Analysis The board temperature was measured using an IR camera (HIS-3000, Wahl) while running under the following conditions: VIN = 230 VRMS 30126933 FIGURE 3. Top Side Thermal Scan 30126934 FIGURE 4. Bottom Side Thermal Scan 15 www.national.com AN-2069 pin, the on-time can be made to be constant. With a DCM Flyback, Δi needs to increase as the input voltage line increases. Therefore a constant on-time (since inductor L is constant) can be obtained. By using the line voltage injection technique, the FLTR2 pin has the voltage wave shape shown in Figure 6 on it with no triac dimmer in-line. Voltage at VFLTR2 peak should be kept below 1.25V. At 1.25V current limit is tripped. C11 is small enough not to distort the AC signal but adds a little filtering. Although the on-time is probably never truly constant, it can be observed in Figure 7 how (by adding the rectified voltage) the on-time is adjusted. Circuit Analysis and Explanations INJECTING LINE VOLTAGE INTO FILTER-2 (ACHIEVING PFC > 0.94) If a small portion (750mV to 1.00V) of line voltage is injected at FLTR2 of the LM3445, the circuit is essentially turned into a constant power flyback as shown in Figure 5. 30126937 FIGURE 6. FLTR2 Waveform with No Dimmer For this evaluation board, the following resistor values are used: R3 = R8 = 309 kΩ R20 = 1.91 kΩ Therefore the voltages observed on the FLTR2 pin will be as follows for listed input voltages: For VIN = 180VRMS, VFLTR2, Pk = 0.78V For VIN = 230VRMS, VFLTR2, Pk = 1.00V For VIN = 265VRMS, VFLTR2, Pk = 1.15V Using this technique, a power factor greater than 0.94 can be achieved without additional passive active power factor control (PFC) circuitry. 30126935 FIGURE 5. Line Voltage Injection Circuit The LM3445 works as a constant off-time controller normally, but by injecting the 1.0VPk rectified AC voltage into the FLTR2 30126936 FIGURE 7. Typical Operation of FLTR2 Pin www.national.com 16 AN-2069 Notes 17 www.national.com LM3445 - 230VAC, 6W- 15W Isolated Flyback LED Driver Notes For more National Semiconductor product information and proven design tools, visit the following Web sites at: www.national.com Products Design Support Amplifiers www.national.com/amplifiers WEBENCH® Tools www.national.com/webench Audio www.national.com/audio App Notes www.national.com/appnotes Clock and Timing www.national.com/timing Reference Designs www.national.com/refdesigns Data Converters www.national.com/adc Samples www.national.com/samples Interface www.national.com/interface Eval Boards www.national.com/evalboards LVDS www.national.com/lvds Packaging www.national.com/packaging Power Management www.national.com/power Green Compliance www.national.com/quality/green Switching Regulators www.national.com/switchers Distributors www.national.com/contacts LDOs www.national.com/ldo Quality and Reliability www.national.com/quality LED Lighting www.national.com/led Feedback/Support www.national.com/feedback Voltage References www.national.com/vref Design Made Easy www.national.com/easy www.national.com/powerwise Applications & Markets www.national.com/solutions Mil/Aero www.national.com/milaero PowerWise® Solutions Serial Digital Interface (SDI) www.national.com/sdi Temperature Sensors www.national.com/tempsensors SolarMagic™ www.national.com/solarmagic PLL/VCO www.national.com/wireless www.national.com/training PowerWise® Design University THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. 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