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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Not so, you absolutely need a higher Vce rating for your transistor. Current limit is applied to stop them blowing up. They are cleverly very simple: You also need to consider that if the low voltage power supply were to drop and the TL stop conducting then the transistor will see the full voltage on the collector due to forward leakage of the LEDs.

I am trying to get this well known circuit [. Here with each 2n Ib at uA, there is still 2. Under this condition, feedback can be applied from the Cathode and Ref pins to create a replica of the internal reference voltage. Consider that if you have 96 LEDs with a Vf of 2. What do you think of that? This is mains powered.

The TL is featured in www.

If I had to guess, your approach was just random shots without design and in all three cases you missed the target entirely and are wondering how it is supposed to work. Post Your Answer Discard By t3l41 “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. For the TL to work correctly, you need enough headroom. 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.

Beyond that, you will need whatever additional headroom is required for your eventual load, too. Led currents do not need to be super accurate. Papou I get it that you don’t have a fixed DC reference.

The circuit of Figure 38 seems non-ideal for your application if it’s a string of LEDs you want to drive rl341, and Figure 39 modified slightly may be better: The circuit of Figure 38 seems non-ideal for your hl341 if it’s a string of LEDs you want to driveand Figure 39 modified slightly may be better:.

Let’s take your last case, since you had sufficient to341 then. Just random remarks here and there plus 7.

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

I think the problem is that you didn’t ever operate the TL correctly, looking over your three cases. If you are using rectified AC without any capacitance, then you conduction angle will be small. The current that they can handle is a function of temp. So you’d need to have capacitance to reduce the ripple.

There are reasons for both approaches. Then, relative to lt341 ground, Vi will be higher. Sign up or log in Sign up using Google.

Is this supposed to eventually be a mains-powered thing? But I think you are just testing this, for now, by shorting both of them. I typically run 2 – 3ma and no more than 15ma into a tl Post as a guest Name. So, the best was to try R1 values and that took me here, thanks for your answers. You state the you want to run 96 LEDs If you want to run 96 LEDs as a string it might be done as below: 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.

So Vce would increase by 4.

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Configuring a TL current limitation Ask Question. T341 will try when I’ll have time and probably come back here. It only takes a few uA.

Component wires folded and 3 solder points, no need for soldering pads. So, there is no 36V maximum V in my case and no Vce increase etc. 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:. I have bought LEDs corn cob lamps.

I can tuck it inside a Hl341 lamp socket well immobile at the end of a hard wire. In this case, you can basically remove the TL and instead consider the circuit shown on the far right, above.

The voltage above R1 is constant and unrelated or impacted by Vce for the transistor.

So, I want a low Ik at 1 mA. Home Questions Tags Users Unanswered. When it is hotter you want to reduce current. Working out the resistors for the TL is very simple, consider this simplification from Figure 39 of the datasheet.

The guy who doesn’t understand anything has added an Update: Time to show a complete schematic for all three versions you are making.

As you can see, quite a lot less than you used.