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All   >>  LED Lighting   >>   General Lighting Applications   >>   Questions
 

PN:NUD4011 Reference Firure 6 of the NUD4011 specification. CKT: Prior to the diode briode bridge, I will have a series impedance (0.44 ufd cap.) on the L1 side of the AC Line, and a 10 ohm MOF resistor on the N side of the line. I will have a cap (small value lytic) at the output of the diode bridge. I plan on using a TVS to limit the max voltage seen by the NUD4011, clamping at 65 volts after the diode bridge. I would like to know if I can connect two strings of LED's (14 LED's in series per string) @ 6 ma current. One LED string would connect to Iout1 with a forward voltage drop of 41 volts dc. The second LED string would connect to Iout2 with a forward voltage drop of 53 volts. This represents the min and max forward voltage drop of the LED's. The goal is to reduce the total voltage seen by How will the NUD4011 respond to the two different voltages on its output? Where should pin 4 be connected? How is the power dissipation calculated? Is it the drop per driver channel for its respective LED string? I plan on using a TVS to limit the max voltage seen by the NUD4011, clamping at 65 volts. Are there any other precautions I should look at?

1) Yes, it is possible to connect series parallel LED arrays with the NUD4011. However, it is important to understand that the output pins of the NUD4011 device (pins 5,6,7 and 8) are not independent but they all are the same output. The device was designed to have the output tied to these four pins so that the heat can be dissipated faster. When series parallel LED arrays are used, the current flowing to each of the arrays may be slightly different due to the different Vf values of each of the LED legs. 2) The NUD4011 datasheet provides extensive information about the power dissipation calculations and typical schematic diagrams. Please see the datasheet and refer to page 4 for power dissipation calculations, and to pages 5 ; 6 for your question about pin 4. Answered by:
ON Semiconductor
2011-05-27 00:59:32.0