November 19, 2018


You state the you want to run 96 LEDs is that a string of LEDs in series? If it is then you have other problems with a 20 mA constant current. PubChem CID: Chemical Names: ; N,N-Bis(2-chloroethyl) allylamine; ALLYLAMINE, N,N-BIS(2-CHLOROETHYL)-; TL ; BRN ; . tl has been an eBay member since Jun and has % positive feedback. Check out tl’s full profile.

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Whatever the number of LEDs in the string, the only thing the circuit sees of it is a current. Let’s start with an overview schematic for the two simpler constant current topologies for the TL I’m using an SCR symbol for the TL here on the left side, below:.

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The 2N is only 40 V Vce. Now, this gets back to the question tl31 how you intend to operate it eventually. But the value of R1 is not clear and I found no simple howto on the Web. I am trying to get this well known circuit [ work inserted in a series of 69 LEDs to protect them according to this specification. So I think this tells you one important fact — the TL is effectively “out of the circuit.

I will try when I’ll have time and probably come back here. Current limit is applied to stop them blowing up. Is this supposed to eventually be a mains-powered thing? What do you think of that? For a moment, let’s consider the case where the TL doesn’t admit any significant current because it doesn’t have enough headroom to work with.

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In this case, you can basically remove the TL and instead consider the circuit shown on the far right, above. I am trying to get this well known circuit [.

So your circuit looks like the middle one, shown above. Sign up using Facebook. You must have reversed C and E leads. The voltage above R1 is constant and unrelated or impacted by Vce for the transistor.

I suspected over-voltage peaks and that current limiting is something to try. So, I want a low Ik at 1 mA.

N,N-Bis(2-chloroethyl)propenamine | C7H13Cl2N – PubChem

Let’s hl341 your last case, since you had sufficient voltage then. You can drive multiple strings with just one TL as shown below now you might understand why I set the Ik at 5 mA in my scenario. You state the you want to run 96 LEDs The load can be inserted into either of the two locations shown, given that the other location is shorted when there is no load there. Another concern is that rather much less that 19mA flows in RCL.

I typically run 2 – 3ma and no more than 15ma t,341 a tl By clicking “Post Your Answer”, you acknowledge that you have read our updated terms of serviceprivacy policy and cookie policyand that your continued use of the website is subject to these policies.

The circuit of Figure 38 seems non-ideal for your application if it’s a string of LEDs you want to driveand Figure 39 modified slightly may be better: If you are using rectified AC without any capacitance, then you conduction angle will be small. For the TL to work correctly, you need enough headroom.


Working out the resistors for the TL is very simple, consider this simplification from Figure 39 of the datasheet. The TL is featured in www. Consider that if you have 96 LEDs with a Vf of 2.

tl – Configuring a TL current limitation – Electrical Engineering Stack Exchange

Under this condition, feedback can be applied from the Cathode and Ref pins to create a replica of the internal reference voltage. Led currents do not need to be super accurate. You could also use a more capable power FET instead of a transistor, but this increases the complexity of the design in terms of minimum voltage etc.

I think the problem is that you didn’t ever operate the TL correctly, looking over your three cases. Not so, you absolutely need a higher Vce rating for your transistor. I would suggest that you put forth a full schematic, with the leds forward voltage and current specified.

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