Universal Input, 20 W, LED Ballast Evaluation Board User's Manual
Contents
1. 2 OSRAM Platinum 12 Out of LED Specification Target Efficiency 80 at Nominal Load Max Size 125 x 37 35 Operating Temp Range 0 to 70 C Cooling Method Supply Orientation Convection Signal Level Control No Semiconductor Components Industries LLC 2012 1 Publication Order Number February 2012 Rev 3 EVBUM2059 D SCHEMATIC http onsemi com NCP1351LEDGEVB 20 5 H auozz amp 4 m 60 82 9 gt lt ns 1 30022 21 ais Kir MW 2007 00 zal Avobep 6 92 AN 9 o mi bla AGE 912 ad oa zo L j eae ISELIN 21 oy ear 5 cece ZX uaz anozy t ov pe 90 at an pri osana 0 gt gt L Aan ta mW d 7 9 wl za 1 h Yv yvy ANEP ESZ 4001 3907 aost 1H NCP1351LEDGEVB LED Current The light output of an LED is determined by the forward current so the control loop will be constant current with a simple Zener to limit the maximum o2. 90 NCP1351LEDGEVB TYPICAL EVALUATION RESULTS 80 70 60 50 40 Efficiency 30 115 Vac 20 230 Vac 10 0 5 10 15 20 25 LED Voltage Vdc Figure 6 Efficiency vs Line and Load 700 mA 21 C 70 F 7 10 5 14 17 5 21 24 5 28 31 5 LED Forward Voltage Vdc Figure 7 Current Regulation vs Forward Voltage 700 mA 21 C 70 F hitp onsemi com 9 35 NCP1351LEDGEVB Modifying the Board for Other LED Currents The constant current constant voltage secondary control loop is very flexible and is implemented using a PNP Q3 with a pair of current sense resistors R12 amp R13 to regulate the current and provide control of the optocoupler to the NCP1351 In addition there is a maximum voltage control loop that is implemented using zener D10 To modify this circuit for alternate current voltage configurations these components should be modified The table on the front page shows several other possible configuration options Note because this design is ultimately power limited based on the transformer design and FET used as the current decreases the maximum voltage capability increases For example for 20 W output the maximum voltage at 350 mA could be as high as 57 Vdc Under UL1310 Class 2 power supplies for use in dry
3. Assuming 80 Efficiency 20 W Output Power 700 mA Output Current 100 kHz Operation at Full Load This gives us a minimum DC input voltage of 120 V there will be some sag on the DC bulk capacitors so an allowance will be made for this by using 80 V as the minimum input voltage including MOSFET drop etc First we need to calculate the turn s ratio this is set by the MOSFET drain rating line voltage and reflected secondary voltage Since this is a constant current circuit we are designing with a varying output voltage we need the maximum output voltage Vin max is the Maximum Rectified Input 375 V VIN min is the Minimum Rectified Input 80 V e Vout is 35 20 W 700 mA is 29 plus a Margin for Safety With a 600 V MOSFET and derating of 80 our maximum allowable drain voltage is 600 0 8 480 V eq 3 max And thus headroom for the reflected secondary voltage and leakage spike of Votamp 480 375 105 V Good results are obtained if we set at 150 of the reflected secondary eq 4 Votame X _ 1 5 eq 5 0 7 as we will need High Voltage Diode Re arranging for N _ 1 5 x 35 0 7 _ 105 0 51 eq 6 We will use a ratio of 0 5 or 2 1 this will give a good transformer construction We can now calculate the maximum duty cycle running in
4. CCM Vout ViNmin N 35 0 7 180x05 047 eq 7 lave 1 21 Tsw Looking at the waveform of the current flowing in the primary of the inductor above if we define a term k equal to k Al a eq 8 hitp onsemi com NCP1351LEDGEVB And use the equation 2 _ Vinin Smax KP in eq 9 Then we can determine the inductance we require If k 2 then we are in boundary conduction mode as the ripple current equals twice the average pulse current so setting k to 2 _ 80 0 47 100 x 103 x 2 0 x 25 Thus we can now find the primary ripple current assuming operation in boundary conduction mode 283 uH 10 2 V L Lfsw Al eq 11 80 0 47 ae 283 10 6 x 100 x 103 ee The average input current I Ayp is 25 lave 25 313 12 AVE 80 eq The average pulse current 1 is l _ 0 313 _ 662 mA eq 13 0 47 Smax Demonstrating that does equal twice 11 and that the peak primary current is 1 32 A We can calculate the RMS current in the MOSFET and sense resistor for dissipation purposes For a stepped sawtooth waveform of this type the equation is 2 1 lams 1 vd 1 109 Thus Iams 0 665 0 47 x jt t 1 32 3 2x eq 15 eq 14 2 526 mA We can also determin
5. NCP1351LEDGEVB Universal Input 20 W LED Ballast Evaluation Board User s Manual ON Semiconductor hitp onsemi com EVAL BOARD USER S MANUAL Circuit Description In order to stay below IEC6100 3 2 Class C the design The NCP1351 controller provides for a low cost variable has been optimized at lt 25 W so assuming 80 efficiency frequency flyback converter It incorporates a very low the maximum output power is 20 W quiescent current allowing for high value resistors to be used as a Start up circuit direct from the HV rail Key Features The design comprises and input filter bridge rectifier Wide Input Voltage Range 85 Vac to 265 Vac using low cost 1N4007 diodes bulk capacitors and line Small Size and Low Cost inductor in arrangement the power stage rectifier Good Line Regulation diode and smoothing capacitors Feedback is CVCC High Efficiency constant current drive for the LED s with a constant voltage in the event of an open circuit output Overload and Short Circuit Protection Figure 1 NCP1351 Board Application Input Voltage Output Power Topology NCP 1351 Solid State Lighting 85 265 Vac Flyback Table 1 OTHER SPECIFICATIONS 350 700 1A 1 LUXEON III 10 10 11 6 LUXEON Rebel 10 6 LUXEON 2 6 Output 1 Maximum Output Voltage 33 V Ripple Not Given Nominal Curretn f e Cree XLamp XR E Cree XLamp
6. damp environments are allowed to have a maximum output voltage of 60 Vdc On the demo board Q3 is implemented using a BC857 transistor which has a maximum Vcgo of 45 Vdc If a higher operating voltage is required this transistor can be changed to a BC856 maximum of 65 Vdc The figure below shows the current regulation performance for a nominal 350 mA output current with the component changes as noted R12 amp R13 3 6 each 010 MMSZ5263B 56 BC856 0 40 0 35 0 30 0 20 LED Current A 0 15 0 25 0 10 0 05 0 00 0 5 10 15 20 25 30 35 40 45 50 55 60 LED Forward Voltage Vdc Figure 8 Typical Current Regulation vs Load 21 C 70 F LUXEON is a registered trademark of Philips Lumileds Lighting Company and Royal Philips Electronics of the Netherlands Platinum DRAGON LED is a registered trademark of OSRAM Opto Semiconductors Inc XLamp is a registered trademark of Cree Inc ON Semiconductor and are registered trademarks of Semiconductor Components Industries LLC SCILLC SCILLC reserves the right to make changes without further notice to any products herein SCILLC makes no warranty representation or guarantee regarding the suitability of its products for any particular purpose nor does SCILLC assume any liability arising out of the application or use of any product or circuit and specifically disclaims any and all liabil
7. e the current sense resistor allowing for a drop across the resistor of 0 8 V Vorop 0 8 Rsense lx 1 32 0 61 Q 16 The total power dissipation is 2 Poysense Irus X Reense 0 526 0 61 eq 17 I 170 mW Two 1 2 Q resistors in parallel will be used as sub 1 Q resistors typically cost more The threshold voltage for the current sense is set by an offset resistor this has a bias current of 270 UA in it so we can determine the resistor value 0 8 270 x 10 6 Vsense Rorrset 3 0 kQ eq 18 Rectifier Snubber Testing demonstrated the need for snubbing on the rectifier as there was a large amount of ringing present after the rectifier turns off The snubber consists of a resistor and capacitor in series and knowing the junction capacitance and ringing frequency we can determine the necessary values L Rs eq 19 2 R eq 20 Knowing that f 1 eq 21 2 LC We can determine L the stray inductance which then allows us to calculate the necessary snubber resistor f 14 5 MHz Measured on Oscilloscope 80 pF Datasheet Figure for MUR840 at 62 V 1 4 1 1 2 5 eq 22 4 x 80 10 12 x x x 14 5 x 105 1 51 uH 1 51 10 6 Re eo x STR eq 23 c _ 2x m x 1 51 x 10 6 x 80 x 10 12 _ S 137 eq 24 504 pF The nearest standard values are 470 pF and 140 Q inserting these into t
8. ery ON Semiconductor 1N4007RLG 1N4007 1000 V Axial Axial Lead Standard Recovery ON Semiconductor 1N4007RLG 1N4007 1000 Axial Axial Lead Standard Recovery ON Semiconductor 1N4007RLG MMSD4148 200 mA 100 V 00 123 Switching Diode ON Semiconductor MMSD4148T1G 20V 1 5W SMA Zener Diode ON Semiconductor 1SMA5932BT3G MURA160 600 V SMA Ultrafast Rectifier ON Semiconductor MURA160T3G MMSD4148 200 mA 100 V 00 123 Switching Diode ON Semiconductor MMSD4148T1G MUR840 400 V TO 220 Ultrafast Power Rectifier ON Semiconductor MUR840G MUR860 Alt hitp onsemi com 6 NCP1351LEDGEVB Table 3 BILL OF MATERIALS Ref Part Type Comment Footprint Description Manufacturer Part Number Value 0 5 W 5 Metal Film Resistor Vishay SFR2500001004J R500 R7 0 125 W 5 0805 Resistor Thick Film NRC NIC NRC10J222BF 0 25 W 5 1206 Resistor Thick Film NRC NIC NRC12J100F of a f ews Txi 25 W LED NIC 10 Pin Vertical 25 W Flyback Transformer NIC NLT282224W3P4020S5P10F Transformer COMPONENT PLACEMENT AND PCB LAYOUT 8 ee eee J C4 Il 8 i E Figure 3 Bottom View hitp onsemi com 7 NCP1351LEDGEVB TYPICAL OPERATIONAL RESULTS Figure 5 Turn off in Detail at 120 Vac 230 Vac and 265 Vac hitp onsemi com 8 LED Current
9. he circuit eliminated the ringing due to the rectifier Auxiliary Winding Normally in a flyback converter the auxiliary winding would be in the form of a flyback winding i e in phase with the output winding and thus provide a semi regulated voltage to supply the controller As this ballast is current controlled and the output voltage can vary over a considerable range depending on the number of LED s connected a forward phased winding is used The auxiliary will therefore vary with line rather than output voltage Since neither option could supply sufficient volts at low input output voltage whilst still staying below the maximum Vcc figure of 28 V a voltage regulator is used formed by Q1 and D6 Below 20 V the regulator does nothing other than act as a small volt drop however as the voltage rises it clamps the voltage to around 20 7 V since the current is very low into the pin there is very little loss http onsemi com 4 NCP1351LEDGEVB MAGNETICS DESIGN DATA SHEET Project Customer ON Semiconductor Part Description 25 W Transformer Schematic ID Core Type EE25 Core Gap Gap for 250 uH Inductance 250 uH Bobbin Type NIC 10 Pin Vertical Windings In Order Winding Type Turns Material Gauge Insulation Data N1 Primary Start on pin 1 and wind 20 turns of 0 28 mm triple insulated wire e g Tex E in one neat layer across the entire bobbin width Finish on pin 2 N2 Secondary Start on pi
10. ity including without limitation special consequential or incidental damages Typical parameters which may be provided in SCILLC data sheets and or specifications can and do vary in different applications and actual performance may vary over time All operating parameters including Typicals must be validated for each customer application by customer s technical experts SCILLC does not convey any license under its patent rights nor the rights of others SCILLC products are not designed intended or authorized for use as components in systems intended for surgical implant into the body or other applications intended to support or sustain life or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application Buyer shall indemnify and hold SCILLC and its officers employees subsidiaries affiliates and distributors harmless against all claims costs damages and expenses and reasonable attorney fees arising out of directly or indirectly any claim of personal injury or death associated with such unintended or unauthorized use even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part SCILLC is an Equal Opportunity Affirmative Action Employer This literature is subject to all applicable copyright laws and is not for resale in any manne
11. ns 9 amp 10 and wind 20 turns of 0 8 mm Grade II ECW distributed evenly across the entire bobbin width Finish on pins 6 amp 7 N3 Primary Start on pin 2 and wind 20 turns of 0 28 mm triple insulated wire e g in one neat layer across the entire bobbin width Finish on pin 3 N4 Primary Aux Start on pin 4 and wind 5 turns of 0 28 mm triple insulated wire in one neat layer spread evenly across the entire bobbin width Finish on pin 5 Sleeving and insulation between primary and secondary as required to meet the requirements of double insulation Primary leakage inductance pins 6 amp 7 and 9 amp 10 shorted together to be lt 6 uH NIC part number NLT282224W3P4020S5P10F Hipot kV between pins 1 2 3 4 amp 5 and pins 6 7 8 9 amp 10 for 60 seconds Schematic Lead Breakout Pinout 5 N1 6 7 4 2 N2 N3 9 10 3 3 2 4 1 4 5 15 hitp onsemi com 5 NCP1351LEDGEVB Table 3 BILL OF MATERIALS Ref Part Type Comment Description Manufacturer Part Number Value C1 220 nF X2 275 VAC 18x 10 X class EMI Suppression Capacitor NPX224M275VX2MF 15 mm Pitch C2 47 uF 400 V General Purpose High Voltage Electrolytic NIC NRE H470M400V16X31 5F 7 5 mm Pitch C10 1 kV JOHANSON 102S41W103KV4E C12 1nF Murata DE1E3KX102MN4AL01 C13 470 uF 212 5 mm Miniature Low Impedance Electrolytic NIC NRSZ471M63V12 5X25F 5 mm Pitch 1N4007 1000 Axial Axial Lead Standard Recov
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13. utput voltage Typical forward voltages vary by LED supplier below are the nominal forward voltage characteristics of the LUXEON 2 at different operating currents C 350 3 42 V 700 mA 3 60 V 1000 mA 3 72 V 1500 mA 3 85 V Driving eight LED s at 700 mA thus gives an output power of 20 2 W at 28 8 V The output current is sensed by a series resistance once the voltage drop across this reaches the baseemitter threshold of the PNP transistor current flows in the opto coupler diode and thus in the FB pin of the NCP1351 The LED current is thus set by 0 6 V eq 1 LED Ronse eq 1 Total sense resistor power dissipation is Pp liep 0 6 V eq 2 So for 700 mA we need 0 9 sense resistor capable of dissipating 420 mW two 330 mW surface mount resistors 1 8 Q each in parallel are used Inductor Selection In a flyback converter the inductance required in the transformer primary is dependant on the mode of operation and the output power Discontinuous operation requires lower inductance but results in higher peak to average current waveforms and thus higher losses For low power designs such as this ballast the inductance is designed to be just continuous or just discontinuous under worst case conditions that is minimum line and maximum load The specification for this ballast is as follows Universal Input 85 Vac to 265 Vac 25 W Maximum Input Power PFC Limit
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