led driver using tnyswitch 3
Hi,
can anybody suggest me how to build a constant current source for driving led of 1wx15=15watts, schematic of cv using zener has been successfully built, waiting for constant current source to drive the leds
specs:
in:85-265vac
0ut: 53V/350mA
please suggest the circuit as soon as possible,
Comments
hi,
is it not possible with common emitter configuration using transistor , does the transistor need to have vceo of 50V> or whether i can select the lower value of vceo, please help in this regards
Thanking You
Hi.
I don't exactly which configuration you will want to use, but assuming that any transistor that is in parallel with the zener (even if there's a resistor in series with it) may need to have more than 50V, especially if CV mode is allowed (when it can be assumed the transistors may be off, and therefore you will have the full output voltage across CE).
Hi.
There are several different circuits, depending on your requirements of precision/efficiency/cost. Here are some examples:
DER173 - very precise output, low losses (for secondary side control), but relatively high cost. Btw, you can easily turn this into an isolated design by replacing Q1 with an optocoupler.
DI113 - still high efficiency, cheaper, but the tolerance is dependent on transistor (although it is temperature compensated, which improves the tolerance somewhat).
DI118 - very simple design, and cheap too, but with worst efficiency
You may also want to look at at our LED design center, where LNK-PH family of primary side control doesn't require any feedback components on the secondary side for very high efficiency. Follow this link.