NCL30000LED1GEVB 90-135 Vac up to 15 Watt Dimmable LED Driver Evaluation Board User's Manual http://onsemi.com EVAL BOARD USER’S MANUAL Introduction This manual also focuses on how the board can be modified to support alternate output currents and power levels. The NCL30000 datasheet contains additional information on operation of the controller and LED driver application. Application Note AND8451 details power stage design details and AND8448 provides specific information for dimming applications. Design calculations are covered in greater detail in these documents. The compact evaluation board is constructed with through-hole components on the top and surface mount components on the bottom side. This board was designed to meet safety agency requirements but has not been evaluated for compliance. When operating this board, observe standard safe working practices. High voltages are present on the board and caution should be exercised when handling or probing various points to avoid personal injury or damage to the unit. Figures 1 and 2 show the top and bottom sides of this evaluation board. AC input connects to the terminal block in the upper left corner. Terminals are marked “L” and “N” for Line and Neutral. The LED load connects to the terminal block in the upper right corner. Note the board is labeled “LED+” and “LED−“. Observe polarity when connecting LED loads. Never connect LEDs to the driver while it is running or before the output capacitors discharge after removing input power. In open load conditions the output capacitors charge to >56 V. Energy stored in the output capacitance can damage or shorten the effective life of the LEDs if improperly discharged into the LEDs. The NCL30000 is a power factor corrected LED driver controller. This evaluation board manual describes the setup and operation of the NCL30000LED1GEVB LED driver for 115 V input. The evaluation board implements an isolated single stage Critical conduction Mode (CrM) flyback converter providing a regulated constant current to an LED load. This board has been specifically configured to support leading and trailing edge line dimming and has been characterized across a range of commercially available dimmers. The output voltage range is suitable for nominal 4 to 15 high brightness power LEDs. Protection features include open load protection, over temperature protection, and overload limiting. As shipped, the evaluation board is set up for the following parameters: Evaluation Board Specifications Input Voltage Range: 90−135 Vac Output Current: 350 mA 5% Output Voltage Range: 12−50 Vdc Output Power: up to 17.5 W Full Load Efficiency: >83% Power Factor: >0.95 Typical 50C Ambient Operation Class B Conducted Emissions Compatible with Triac and Electronic Dimmers Semiconductor Components Industries, LLC, 2012 September, 2012 − Rev. 3 1 Publication Order Number: EVBUM2099/D NCL30000LED1GEVB Figure 1. Top Side of Board Figure 2. Bottom Side of Board http://onsemi.com 2 1 amp Line Neutral 1 J1-2 15 R1 R8 C1 Not Fitted F1 R9 6.2K C6 10uF Not Fitted 1 3 4 R11 100K 27mH L1 D8 5.1V BZX84C5V1 RT1 R10 6.2K D7 BAW56 1 2 4.7K R14 5K6 T Q1 MMBTA06 R13 47K R12 Not fitted R2 L2 470uH D9 MMBZ5245 15V R15 100K Q2 MMBTA06 R5 Zero RV1 D3 MRA4007 U1 ZCD C4 100nF R4 120 NCL30000 1 8 MFP Vcc 2 7 Comp DRV 3 6 Ct GND 4 5 CS C3 470nF C9 470pF C8 10uF D4 MRA4007 V275LA2 C7 1nF R17 100 D2 MRA4007 L3 800uH R3 5K6 C2 47nF D1 MRA4007 R16 47K R7 47K R20 0.33 OHM R18 100 U2 PS2561L_1 T1C T1B T1A R6 Not fitted Q3 NDD05N50 R19 10 D6 BAS21 D5 MURA160 C5 4700 pF C11 470uF 4 3 + R21 22K C13 100nF R22 1K D11 BZX84C5V6 5.6V C12 470uF + D10 MURD620 C10 4.7 nF T1E T1D 4 3 1 http://onsemi.com 3 Figure 3. Board Schematic 2 J1-1 D13 BAW56 D12 BZX84C56 56V R23 1K R24 47K Q5 MMBTA06 Q4 MMBTA06 IN1+ IN1IN2+ IN2GND 3 2 5 6 4 C15 220nF LM2904 8 VCC 1 OUT1 7 OUT2 U3 C14 100pF 1K R25 R28 470 R27 200 R26 16K 0.2 ohm R29 U4 TL431A R30 R31 24K 24K C16 100nF J2-1 J2-2 1 LED Cathode LED Anode 1 NCL30000LED1GEVB NCL30000LED1GEVB Board Configuration On-time Capacitor The evaluation board has been optimized for dimming with a 12 W load. Output current is regulated at 350 mA from 135 V rms down to a setpoint of about 108 V rms. When the input voltage is ~108 V rms, the control method changes from closed loop secondary side current control to primary side control. As the input voltage is reduced further the output current drops in a smooth fashion in response to the lower input voltage. This response matches the driver to a dimmer thus emulating the dimming response of an incandescent bulb. The following information details reconfiguring the evaluation board for alternate applications. The input voltage at which dimming or reduction of output current occurs is controlled by C9, power delivered to the LED load, and parameters from the evaluation board. The approximate value of C9 is calculated by the formula below: C9 [ 4 @ L pri @ P out @ I charge hȀ @ V 2 pk @ V Ctmax @ ǒ V pk N @ V out Ǔ )1 (eq. 1) Values in the equation above are described in Table 1 below: Table 1. VARIABLES FOR CALCULATING CT CAPACITOR Variable Description Lpri Transformer Primary Inductance Pout Power Output to LEDs Icharge h’ Vpk Vctmax N Vout Value for Evaluation Board 0.00157 12 Nominal On Time Capacitor Charge Current 275 mA Transformer/Secondary Efficiency 0.95 Dimming Point Peak Voltage 108 Vrms = 152.7 Vpk Nominal On Time Capacitor Peak Voltage 4.93 Transformer Turns Ratio 3.83 LED Load Voltage (12 LEDs) C9 [ 37 4 @ 0.00157 @ 12 @ 275m 0.95 @ 152.7 2 @ 4.93 @ 152.7 ) 1Ǔ + 394 pF ǒ3.83 @ 37 (eq. 2) Output Current Setup In practice, the value of capacitance calculated is an approximation of operating conditions and optimization is required. Empirical testing with a dimmer may be done to select the optimum input voltage for dimming to begin. A value of 470 pF was selected for C9 on the evaluation board to achieve desired results. Modifying this evaluation board for alternate LED configurations and power levels is straight forward. Using the equation above, enter the target LED power, LED voltage, and the target AC input voltage below which dimming should occur. Select a capacitor somewhat below the value returned by the approximate formula. Performance should be evaluated using the desired dimmers. Check operation by noting the conduction angle below which LED current reduces. Increasing the value of capacitor C9 lowers the conduction angle where dimming occurs. Performance can be optimized by selecting the value of C9. Figure 4 below is the bottom side of the evaluation board. Component locations are circled indicating those values that are most likely to be changed to optimize for a different power level. A particular driver application may require LED current other than 350 mA. Output current is controlled by R29 located in Figure 4. The following formula is used to set the output current. R29 + 0.07 I out (eq. 3) Dissipation for current sense resistor R29 is defined by the formula below. P R29 + 0.07 R29 2 (eq. 4) The secondary windings of power transformer T1 are connected in series to support the 50 V/350 mA output rating of the evaluation board. Applications below 25 V or greater than 450 mA output should have the transformer secondary windings configured in parallel. This helps maintain proper primary bias voltage and enhances current carrying capability of the transformer. Table 2 shows how to configure the transformer flying leads in the PCB holes for series and parallel configuration. Figure 5 is the top side of the circuit board highlighting the wire holes H1 − H6. Table 2. WINDING CONFIGURATION Winding Configuration H1 H2 H3 H4 H5 H6 Series (default) FL1 <open> FL2 FL3 <open> FL4 Parallel FL1 FL3 <open> <open> FL2 FL4 http://onsemi.com 4 NCL30000LED1GEVB Figure 4. Bottom Side PCB Component Locations Figure 5. PCB Holes for Transformer Leads http://onsemi.com 5 NCL30000LED1GEVB Primary Current Limit As built, the evaluation board is suitable for 17.5 W maximum. The transformer secondary windings will support up to 1 A of LED current with secondary windings configured in parallel. A 200 V output rectifier was selected for applications up to 50 V dc output and 135 V ac input. Lower voltage rectifiers are recommended for applications below 50 V dc and/or 135 V ac input. A lower forward voltage drop output rectifier will improve efficiency. Selecting a rectifier with a higher current rating typically provides lower forward drop at the currents of interest. A 6 A rectifier was selected for the evaluation board to provide low forward drop. Applications with sufficiently low output voltage and/or low maximum input voltage could benefit from a low forward voltage drop Schottky rectifier. Any change to the output rectifier requires verifying the maximum voltage rating is not exceeded. Maximum current in the switching FET Q3 is established by R20. The demo board components have been designed to support up to 17.5 W output at 90 V rms input. Note C9 has been preconfigured for 470 pF which limits the maximum power. If the application requires alternate power level or input voltage, the value of R20 can be adjusted. Lower power or high input line voltage applications my benefit from a higher value resistance which provides cycle-by-cycle current monitoring in the event of a fault. The formula below provides an estimated value for R20 which includes a 25% tolerance for components and start up conditions. R20 + 0.5 1.25 @ I pri (eq. 5) Open Load Protection The evaluation board includes a circuit to protect the output capacitors in the event of open load conditions. The output voltage will be limited when zener diode D12 exceeds the zener voltage plus ~0.7 V. D12 is presently 56 V which means the maximum output will be approximately 56.7 V. D12 can be changed to protect output capacitors of different voltage rating. Select D12 zener voltage to match open load requirements. The location of D12 is shown in Figure 4. Output Capacitor The evaluation board regulates constant current and therefore the output voltage is determined by the LED load characteristics at the set current level. Energy storage to maintain high power factor and low output ripple current requires relatively large output filter capacitors. The LED load can be modeled as a constant voltage source with some series impedance. In essence, the ripple current in the LEDs is controlled by the series impedance coupling the constant voltage nature of the filter capacitance and constant voltage characteristic of the LEDs in a complex relationship. Two 470 mF capacitors connected in parallel provide about 30% or 105 mA peak-to-peak ripple for a 350 mA average LED current. Increasing the output capacitance reduces the ripple current and conversely decreasing capacitance will increase the ripple. Applications requiring average output currents other than 350 mA can be scaled to this value. For example an application requiring 700 mA requires two 1,000 mF capacitors in parallel to provide 30% ripple. Typical Performance Data Figure 6 below displays the relationship between input voltage and LED current for a 12 LED, 13 W load. Higher input voltages allow the secondary side control loop to regulate 350 mA output current at 37 V nominal load. Note the inflection point where reduction in current begins as the input voltage is reduced below 110 V ac. This is the dimming inception point. http://onsemi.com 6 400 90% 350 80% 300 70% 250 60% 200 50% 150 40% 100 30% 50 20% 0 Efficiency LED Current (mA) NCL30000LED1GEVB 10% 20 30 40 50 60 70 80 90 Input Voltage (Vac) 100 110 120 130 Figure 6. Line Regulation and Efficiency for 13 W Load attention from utility companies and government agencies. Figure 7 below displays exemplary performance of the evaluation board. Data for 6 and 12 LED loads are shown. The EMI filter was designed for a 17.5 W load. The filter can be optimized for higher power factor in applications requiring less power. Efficiency performance is shown in Figure 6 as well. Note the efficiency remains above 70% until the output current drops to about 70 mA. The output voltage is about 34 V meaning the delivered power is about 2.4 W or less than 20% of the full power. As the current delivered is reduced, the fixed losses for startup and biasing begin to dominate the efficiency curve resulting in a steep drop off of efficiency. Power factor and input current Total Harmonic Distortion (THD) are performance factors receiving considerable http://onsemi.com 7 NCL30000LED1GEVB 20 1.00 18 0.98 14 12 0.96 10 8 0.94 Power Factor (PF) Percent Input Current THD (%) 16 6 4 THD 12 LED THD 6 LED PF 12 LED PF 6 LED 0.92 2 0 90 95 100 105 110 115 120 125 0.90 135 130 Input Voltage (Vac) Figure 7. Power Factor and THD of greater than 20:1 was demonstrated consistently with the exception being the trailing edge dimmer which has a limited range of conduction control inherent in the model tested. The evaluation board was tested with a variety of commercial dimmers. Figure 8 shows the dimming performance with several triac and electronic dimmers. Dimming control range varies by manufacturer, but a range 400 350 LED Current (mA) 300 250 Leviton Sureslide Leviton Electronic Cooper Aspire Lutron Skylark Leviton Illumittech Lutron Digital Fade Leviton Rotary GE DI 61 Lutron Toggler 200 150 100 50 0 0 20 40 60 80 100 Conduction Angles (degrees) 120 140 Figure 8. Performance of Evaluation Board with Various Line Dimmers http://onsemi.com 8 160 180 NCL30000LED1GEVB Table 3 lists commercial dimmers successfully tested with the evaluation board. The load is 12 LEDs (Vf = 37 Vdc) and nominal current is set for 350 mA. Table 3. DIMMER COMPATIBILITY CHART Manufacturer Dimmer Model Minimum Conduction Angle (degrees) Current at Minimum Conduction Angle (mA) Leviton Sureslide 6633-PLW 5.5 0 Leviton Electronic 6615-POW 55 71.5 Cooper Aspire 9530AA 5.8 0 Lutron Skylark S-600 6.3 0 Leviton Illumatech IPI06 19.4 13 Lutron Digital Fade MAW-600H 16 11.7 Leviton Rotary OC58I1 11.9 0 GE DI 61 5.4 0 Lutron Toggler TG-600PH 23 21.5 SCT YM-2508A 5.4 0 KUEI LIN AC 110V 500W 5.8 0 DING CHUNG DC-310 14.5 1.2 Configuration for 6.6 W, 6 LED Load Figure 9 shows line regulation data for this 6 LED load with C9 at the original value of 470 pF and the new value of 270 pF. Note the dimming inception voltage shifts up to about 110 V ac. This provides a wider dimming range as was demonstrated in Figure 6 for the 13 W LED load. Using the formula for C9 shown in the ON-time Capacitor section above, a new capacitor value based on a 6 LED load operating at 350 mA, 6.6 W is calculated. The formula gives 237 pF. A value of 270 pF is selected for optimum performance. 400 350 LED Current (mA) 300 250 200 150 6 LEDs − 470 pF 6 LEDs − 270 pF 100 50 0 20 40 60 80 Input Voltage (Vac) 100 Figure 9. Line Regulation for 6 LED Load http://onsemi.com 9 120 140 NCL30000LED1GEVB Conducted EMI Shown below in Figure 10 is a scan of conducted EMI for this demonstration board. This unit meets the requirements of CISPR 22 with at least 6dB margin. dBuV 80 70 60 EN 55022; Class B Conducted, Quasi−Peak EN 55022; Class B Conducted, Average 50 40 30 20 Average 10 0 −10 −20 1 10 2/17/2010 10:16:53 AM (Start = 0.15, Stop = 30.00) MHz Figure 10. Conducted EMI Scan Conclusion Additional Application Information and Tools The NCL30000LED1GEVB is a versatile dimmercompatible LED driver. This board provides rapid assessment of capabilities and serves as a basis for LED driver solutions. Smooth flicker-free dimming performance is demonstrated with a wide variety of commercially available dimmers. Full 350 mA LED current is provided at maximum dimmer setting. High power factor and high efficiency provide a cost effective solution for a dimmer compatible LED driver. The NCL30000LED1GEVB evaluation board, NCL30000 datasheet, AND8451 Power Stage Design Guidelines, Microsoft Excel Design Spreadsheet, and AND8448 TRIAC Dimming application note are available at www.onsemi.com. Microsoft and Excel are registered trademarks of Microsoft Corporation. ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC owns the rights to a number of patents, trademarks, copyrights, trade secrets, and other intellectual property. A listing of SCILLC’s product/patent coverage may be accessed at www.onsemi.com/site/pdf/Patent−Marking.pdf. SCILLC reserves the right to make changes without further notice to any products herein. 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