LM3445

LM3445 - 230VAC, 6W- 15W Isolated Flyback LED Driver LM3445 - 230VAC, 6W- 15W Isolated Flyback LED Driver National Semiconductor Application Note 2069 Montu Doshi November 23, 2010 Introduction 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. Key Features • • • • 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 VIN VOUT ILED POUT fsw Parameter Input voltage LED string voltage LED string average current Output power Switching frequency Min 180 VRMS 13 V Typ 230 VRMS 20 V 350 mA 7.2 W 67 kHz Max 265 VRMS 27 V - Demo Board 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 # 1 2 Name ASNS FLTR1 Description 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. 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. 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. 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. 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. Circuit ground connection. LED current sense pin. Connect a resistor from main switching MOSFET source, ISNS to GND to set the maximum LED current. Power MOSFET driver pin. This output provides the gate drive for the power switching MOSFET of the buck controller. 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 DIM 4 5 6 7 8 9 10 COFF FLTR2 GND ISNS GATE VCC BLDR 3 www.national.com AN-2069 Bill of Materials Designator AA1 U1 C1 C2 C3 C4 C5 C6 C7-DNP C8 C9, C11 C10 C12 C13 C14 C15 C16 C17 C18 C20 D1 D2 D3 D4 D5, D10 D6 D7, D8, D9 F1 Description Printed Circuit Board Triac Dimmable Offline LED Driver, PowerWise Ceramic, X7R, 250VAC, 10% Ceramic, Polypropylene, 400VDC, 10% CAP, CERM, 330pF, 630V, +/-5%, C0G/NP0, 1206 Ceramic, X7R, 250V, X2, 10%, 2220 CAP, Film, 0.033µF, 630V, +/-10%, TH CAP, CERM, 0.015µF, 500V, +/-10%, X7R, 1812 CAP, CERM, 0.1µF, 630V, +/-10%, X7R, 1812 CAP, CERM, 0.1µF, 630V, +/-10%, X7R, 1812 CAP, CERM, 1µF, 50V, +/-10%, X7R, 1210 CAP, CERM, 0.47µF, 50V, +/-10%, X7R, 0805 Aluminium Electrolytic, 680uF, 35V, 20%, CAP, CERM, 1µF, 35V, +/-10%, X7R, 0805 CAP, CERM, 0.1µF, 25V, +/-10%, X7R, 0603 CAP, TANT, 47uF, 16V, +/-10%, 0.35 ohm, 6032-28 SMD CAP, CERM, 0.47µF, 16V, +/-10%, X7R, 0603 CAP, CERM, 0.22µF, 16V, +/-10%, X7R, 0603 CAP, CERM, 2200pF, 50V, +/-10%, X7R, 0603 CAP, CERM, 330pF, 50V, +/-5%, C0G/NP0, 0603 DIODE TVS 250V 600W UNI 5% SMD Diode, Switching-Bridge, 600V, 0.8A, MiniDIP Diode, Silicon, 1000V, 1A, SOD-123 Diode, Schottky, 100V, 1A, SMA Diode, Zener, 13V, 200mW, SOD-323 Diode, Zener, 36V, 550mW, SMB Diode, Schottky, 100V, 150 mA, SOD-323 Fuse, 500mA, 250V, Time-Lag, SMT National Semiconductor Murata Electronics North America WIMA TDK Murata Electronics North America EPCOS Inc Vishay/Vitramon MuRata MuRata MuRata MuRata Nichicon Taiyo Yuden MuRata AVX MuRata TDK MuRata MuRata Littelfuse Diodes Inc. STMicroelectronics Diodes Inc ON Semiconductor STMicroelectronics Littelfuse Inc Keystone Manufacturer LM3445MM DE1E3KX332MA5BA01 MKP10-.033/400/5P10 C3216C0G2J331J GA355DR7GF472KW01L B32921C3333K VJ1812Y223KBEAT4X GRM43DR72J104KW01L GRM43DR72J104KW01L GRM32RR71H105KA01L GRM21BR71H474KA88L UHE1V681MHD6 GMK212B7105KG-T GRM188R71E104KA01D TPSC476K016R0350 GRM188R71C474KA88D C1608X7R1C224K GRM188R71H222KA01D GRM1885C1H331JA01D P6SMB250A HD06-T STPS1H100A DDZ13BS-7 1SMB5938BT3G BAT46JFILM 0443.500DR 1902C Part Number RoHS Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Comchip Technology CGRM4007-G H1, H2, H5, H6 Standoff, Hex, 0.5"L #4-40 Nylon H3, H4, H7, H8 Machine Screw, Round, #4-40 x 1/4, Nylon, Philips panhead J1, J2 L1, L2 LED+, LED-, TP7, TP8 Q1 Q2 Q3 Q4 R1 R2, R7 R3, R8 Conn Term Block, 2POS, 5.08mm PCB Inductor, Radial Lead Inductors, Shielded, 4.7mH, 130mA, 12.20ohm, 7.5mm Radial, Terminal, 22 Gauge Wire, Terminal, 22 Guage Wire MOSFET, N-CH, 600V, 200mA, SOT-223 Transistor, NPN, 300V, 500mA, SOT-23 MOSFET, N-CH, 650V, 800mA, IPAK MOSFET N-CH 100V 170MA SOT23-3 RES, 221 ohm, 1%, 0.25W, 1206 RES, 200k ohm, 1%, 0.25W, 1206 RES, 309k ohm, 1%, 0.25W, 1206 B&F Fastener Supply NY PMS 440 0025 PH Phoenix Contact TDK Corporation 3M Fairchild Semiconductor Diodes Inc. Infineon Technologies Diodes Inc. Vishay-Dale Vishay-Dale Vishay-Dale 1715721 TSL0808RA-472JR17-PF 923345-02-C FQT1N60CTF_WS MMBTA42-7-F SPU01N60C3 BSS123-7-F CRCW1206221RFKEA CRCW1206200KFKEA CRCW1206309KFKEA www.national.com 4 AN-2069 Designator R4, R12 R5-DNP R6 R10 R11 R13 R14 R15 R16 R17 R18 R19 R20 R21 R22 R23 RT1, RT2 T1 TP9, TP10 VR1 Description RES, 10k ohm, 5%, 0.25W, 1206 RES, 680 ohm, 5%, 1W, 2512 RES, 820 ohm, 5%, 1W, 2512 RES, 430 ohm, 5%, 1W, 2512 RES, 49.9k ohm, 1%, 0.125W, 0805 RES, 33.0 ohm, 1%, 0.25W, 1206 RES, 10 ohm, 5%, 0.125W, 0805 RES, 10.0k ohm, 1%, 0.1W, 0603 RES, 280k ohm, 1%, 0.1W, 0603 RES, 475k ohm, 1%, 0.1W, 0603 RES, 49.9k ohm, 1%, 0.1W, 0603 RES, 10 ohm, 5%, 0.1W, 0603 RES, 1.91k ohm, 1%, 0.1W, 0603 RES, 2.70 ohm, 1%, 0.25W, 1206 RES, 10.7 ohm, 1%, 0.125W, 0805 RES, 324k ohm, 1%, 0.1W, 0603 Current Limitor Inrush, 60Ohm, 20%, 5mm Raidal FLBK TFR, 2.07 mH, Np=140T, Ns=26T, Na= 20T Terminal, Turret, TH, Double Varistor 275V 55J 10mm DISC Manufacturer Vishay-Dale Vishay/Dale Vishay/Dale Vishay/Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Vishay-Dale Panasonic Vishay-Dale Vishay-Dale Cantherm Wurth Elektornik EPCOS Inc Part Number CRCW120610K0JNEA CRCW2512680RJNEG CRCW2512820RJNEG CRCW2512430RJNEG CRCW080549K9FKEA CRCW120633R0FKEA CRCW080510R0JNEA CRCW060310K0FKEA CRCW0603280KFKEA CRCW0603475KFKEA CRCW060349K9FKEA CRCW060310R0JNEA CRCW06031K91FKEA ERJ-8RQF2R7V CRCW080510R7FKEA CRCW0603324KFKEA MF72-060D5 750815040 REV 1 S10K275E2 RoHS Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Y Keystone Electronics 1502-2 5 www.national.com AN-2069 Transformer Design Mfg: Wurth Electronics, Part #: 750815040 Rev. 01 30126909 Parameter D.C. Resistance (3-1) D.C. Resistance (6-4) D.C. Resistance (10-13) Inductance (3-1) Inductance (6-4) Inductance (10-13) Leakage Inductance (3-1) Dielectric (1-13) Turns Ratio Turns Ratio Test Conditions 20°C 20°C 20°C 10 kHz, 100 mVAC 10 kHz, 100 mVAC 10 kHz, 100 mVAC 100 kHz, 100 mAVAC (tie 6+4, 10+13) tie (3+4), 4500 VAC, 1 second (3-1):(6-4) (3-1):(10:13) Value 1.91 Ω ± 10% 0.36 Ω ± 10% 0.12 Ω ± 10% 2.12 mH ± 10% 46.50 µH ± 10% 74.00 µH ± 10% 18.0 µH Typ., 22.60 µH Max. 4500 VAC, 1 minute 7:1 ± 1% 5.384:1 ± 1% www.national.com 6 AN-2069 Demo Board Wiring Overview 30126903 Wiring Connection Diagram Test Point TP8, TP10 TP7, TP9 J1-1 J1-2 Name LED + LED LINE NEUTRAL I/O Output Output Input Input Description LED Constant Current Supply Supplies voltage and constant-current to anode of LED string. LED Return Connection (not GND) Connects to cathode of LED string. Do NOT connect to GND. AC Line Voltage Connects directly to AC line or output of TRIAC dimmer of a 230VAC system. AC Neutral Connects directly to AC neutral of a 230VAC system. Demo Board Assembly 30126905 Top View 30126906 Bottom View 7 www.national.com AN-2069 Typical Performance Characteristics Efficiency vs. Line Voltage Original Circuit 10 LEDs (Note 1, Note 2, Note 3) Efficiency vs. Line Voltage Modified Circuits 0.97 0.93 EFFICIENCY Mod C (10 LEDs) Mod B (8 LEDs) 0.83 0.82 EFFICIENCY 8 LEDs 0.89 0.85 0.81 0.77 0.73 0.68 0.64 0.81 0.80 0.79 0.78 0.77 6 LEDs 4 LEDs Original (6 LEDs) Mod A (4 LEDs) 0.76 180 190 200 210 220 230 240 250 260 INPUT VOLTAGE (VRMS) 30126910 0.60 180 190 200 210 220 230 240 250 260 INPUT VOLTAGE (VRMS) 30126914 LED Current vs. Line Voltage Original Circuit 650 550 LED CURRENT (mA) 4 LEDs LED Current vs. Line Voltage Modified Circuits 600 550 LED CURRENT (mA) 500 450 400 350 300 250 200 150 Original (6 LEDs) Mod A (4 LEDs) Mod C (10 LEDs) Mod B (8 LEDs) 450 350 250 6 LEDs 8 LEDs 150 10 LEDs 50 180 190 200 210 220 230 240 250 260 INPUT VOLTAGE (VRMS) 30126911 100 180 190 200 210 220 230 240 250 260 INPUT VOLTAGE (VRMS) 30126915 Power Factor vs. Line Voltage Original Circuit 0.956 0.952 POWER FACTOR 10 LEDs 8 LEDs Power Factor vs. Line Voltage Modified Circuits 0.97 0.93 POWER FACTOR 0.948 0.944 0.940 0.936 0.932 0.928 0.924 0.920 180 190 200 210 220 230 240 250 260 INPUT VOLTAGE (VRMS) 30126912 0.89 0.85 0.81 0.77 0.73 0.68 0.64 0.60 180 190 200 210 220 230 240 250 260 INPUT VOLTAGE (VRMS) 30126916 4 LEDs 6 LEDs Mod C (10 LEDs) Mod B (8 LEDs) Original (6 LEDs) Mod A (4 LEDs) www.national.com 8 AN-2069 Output Power vs. Line Voltage Original Circuit 12 11 OUTPUT POWER (W) 10 LEDs Output Power vs. Line Voltage Modified Circuits 25.0 22.5 OUTPUT POWER (W) 10 9 8 7 6 5 4 3 8 LEDs 4 LEDs 20.0 17.5 15.0 12.5 10.0 7.5 5.0 2.5 Mod B (8 LEDs) Mod C (10 LEDs) 6 LEDs 2 180 190 200 210 220 230 240 250 260 LINE VOLTAGE (VRMS) 30126913 Original (6 LEDs) 0.0 180 190 200 210 220 230 240 250 260 Mod A (4 LEDs) INPUT VOLTAGE (VRMS) 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) Power MOSFET Drain and ISNS (Pin-7) Voltage (VIN = 230VRMS, 6 LEDs, ILED = 350mA) Ch1: Output Voltage (10 V/div); Ch3: LED Current (100 mA/div); Time (4 ms/div) 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 AN-2069 Experimental Results 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 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. MEASURED EFFICIENCY AND LINE REGULATION (6 LEDS, NO TRIAC DIMMER) VIN (VRMS) 180 190 200 210 220 230 240 250 260 IIN (mARMS) 31.73 33.39 35.11 36.85 38.53 40.18 41.75 43..39 45.07 PIN(W) 5.35 5.96 6.61 7.30 8.01 8.75 9.50 10.30 11.14 VOUT (V) 19.67 19.85 20.04 20.22 20.40 20.56 20.74 20.90 21.05 ILED (mA) 221.64 244.82 269.16 294.82 321.26 348.70 375.70 404.82 434.48 POUT (W) 4.36 4.86 5.39 5.96 6.55 7.17 7.79 8.46 9.15 Efficiency (%) Power Factor 81.4 81.5 81.6 81.6 81.8 82.0 82.0 82.1 82.0 0.9375 0.9394 0.9493 0.9493 0.9451 0.9463 0.9477 0.9490 0.9500 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 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. MEASURED DIMMING PERFORMANCE VIN (VRMS) 229.39 220.47 210.24 199.05 190.32 180.33 170.51 156.39 149.11 140.35 129.61 119.7 110.17 100.55 90.75 79.72 70.42 60.91 49.94 45.04 VO (V) 20.51 20.35 20.16 19.98 19.80 19.61 19.42 19.31 19.15 18.97 18.75 18.53 18.33 18.11 17.87 17.59 17.34 17.08 16.77 16.64 ILED (mA) 343.1 320.8 294.8 266.8 245.8 222.7 200.1 187.4 171.6 154.0 133.1 115.3 99.1 83.5 68.8 53.1 40.8 30.1 19.8 16.0 POUT (W) 7.04 6.53 5.94 5.33 4.87 4.37 3.89 3.62 3.29 2.92 2.50 2.14 1.82 1.51 1.23 0.93 0.71 0.81 0.33 0.27 11 www.national.com 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 Thermal Analysis The board temperature was measured using an IR camera (HIS-3000, Wahl) while running under the following conditions: VIN = 230 VRMS ILED = 348 mA # of LEDs = 6 POUT = 7.2 W The results are shown in the following figures. 30126933 FIGURE 3. Top Side Thermal Scan 30126934 FIGURE 4. Bottom Side Thermal Scan 15 www.national.com AN-2069 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. 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. 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 Amplifiers Audio Clock and Timing Data Converters Interface LVDS Power Management Switching Regulators LDOs LED Lighting Voltage References PowerWise® Solutions Temperature Sensors PLL/VCO www.national.com/amplifiers www.national.com/audio www.national.com/timing www.national.com/adc www.national.com/interface www.national.com/lvds www.national.com/power www.national.com/switchers www.national.com/ldo www.national.com/led www.national.com/vref www.national.com/powerwise WEBENCH® Tools App Notes Reference Designs Samples Eval Boards Packaging Green Compliance Distributors Quality and Reliability Feedback/Support Design Made Easy Design Support www.national.com/webench www.national.com/appnotes www.national.com/refdesigns www.national.com/samples www.national.com/evalboards www.national.com/packaging www.national.com/quality/green www.national.com/contacts www.national.com/quality www.national.com/feedback www.national.com/easy www.national.com/solutions www.national.com/milaero www.national.com/solarmagic www.national.com/training Applications & Markets Mil/Aero PowerWise® Design University Serial Digital Interface (SDI) www.national.com/sdi www.national.com/wireless www.national.com/tempsensors SolarMagic™ THE CONTENTS OF THIS DOCUMENT ARE PROVIDED IN CONNECTION WITH NATIONAL SEMICONDUCTOR CORPORATION (“NATIONAL”) PRODUCTS. NATIONAL MAKES NO REPRESENTATIONS OR WARRANTIES WITH RESPECT TO THE ACCURACY OR COMPLETENESS OF THE CONTENTS OF THIS PUBLICATION AND RESERVES THE RIGHT TO MAKE CHANGES TO SPECIFICATIONS AND PRODUCT DESCRIPTIONS AT ANY TIME WITHOUT NOTICE. NO LICENSE, WHETHER EXPRESS, IMPLIED, ARISING BY ESTOPPEL OR OTHERWISE, TO ANY INTELLECTUAL PROPERTY RIGHTS IS GRANTED BY THIS DOCUMENT. TESTING AND OTHER QUALITY CONTROLS ARE USED TO THE EXTENT NATIONAL DEEMS NECESSARY TO SUPPORT NATIONAL’S PRODUCT WARRANTY. EXCEPT WHERE MANDATED BY GOVERNMENT REQUIREMENTS, TESTING OF ALL PARAMETERS OF EACH PRODUCT IS NOT NECESSARILY PERFORMED. NATIONAL ASSUMES NO LIABILITY FOR APPLICATIONS ASSISTANCE OR BUYER PRODUCT DESIGN. BUYERS ARE RESPONSIBLE FOR THEIR PRODUCTS AND APPLICATIONS USING NATIONAL COMPONENTS. PRIOR TO USING OR DISTRIBUTING ANY PRODUCTS THAT INCLUDE NATIONAL COMPONENTS, BUYERS SHOULD PROVIDE ADEQUATE DESIGN, TESTING AND OPERATING SAFEGUARDS. EXCEPT AS PROVIDED IN NATIONAL’S TERMS AND CONDITIONS OF SALE FOR SUCH PRODUCTS, NATIONAL ASSUMES NO LIABILITY WHATSOEVER, AND NATIONAL DISCLAIMS ANY EXPRESS OR IMPLIED WARRANTY RELATING TO THE SALE AND/OR USE OF NATIONAL PRODUCTS INCLUDING LIABILITY OR WARRANTIES RELATING TO FITNESS FOR A PARTICULAR PURPOSE, MERCHANTABILITY, OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT. LIFE SUPPORT POLICY NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS PRIOR WRITTEN APPROVAL OF THE CHIEF EXECUTIVE OFFICER AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: Life support devices or systems are devices which (a) are intended for surgical implant into the body, or (b) support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in a significant injury to the user. A critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or system or to affect its safety or effectiveness. National Semiconductor and the National Semiconductor logo are registered trademarks of National Semiconductor Corporation. All other brand or product names may be trademarks or registered trademarks of their respective holders. Copyright© 2010 National Semiconductor Corporation AN-2069 For the most current product information visit us at www.national.com National Semiconductor Americas Technical Support Center Email: support@nsc.com Tel: 1-800-272-9959 www.national.com National Semiconductor Europe Technical Support Center Email: europe.support@nsc.com National Semiconductor Asia Pacific Technical Support Center Email: ap.support@nsc.com National Semiconductor Japan Technical Support Center Email: jpn.feedback@nsc.com