Electronics > Beginners
wiring new PSU to a flickering LED lamp
smile:
The LR8K4-G chip is 20mA is there anything for 300mA at 11V or adjustable? LR8K4-G is linear so it should not flicker right?
mariush:
If you read the specifications, it's 20mA typical , maximum 30mA.
So "your mileage may vary" ... you can set the current to 25mA or 30mA and hopefully it will work, if not it will limit at lower current.
The limit is also because of thermals .. for example if you have 400v in and you output 10v then you have 390v differential... at 20mA that's 390v x 0.02A = ~ 8w of power dissipated in the chip.
I recommended that particular regulator chip because it's capable of working with high voltages, up to 450v so you can use the leds as you have them on the circuit board, in series - majority of linear regulators are designed to accept only up to 60v ("high voltage" versions of some linear regulators) or fr the majority of linear regulators, up to around 37v.
Of course there are plenty of linear regulators which can output 12v or whatever voltage you want at higher currents, but the input voltage will have to be smaller.
BUT the thing with leds is that you want to limit the CURRENT and adjust voltage based on current , because the forward voltage of the leds changes slightly as they heat up or cool down. It's also a bad practice to have multiple leds in parallel as i explained above.
If you have a smaller voltage,then it would make more sense to actually use LINEAR led driver ICs which can monitor the current and automatically adjust the voltage as forward voltage changes while in use (forward voltage varies with heat).. go on digikey.com or other similar sites, go to led driver ICs and filter them by "linear" regulation, select your maximum current, the voltage and then check out datasheets and see if you like a specific chip
smile:
--- Quote ---If you have a smaller voltage,then it would make more sense to actually use LINEAR led driver ICs which can monitor the current and automatically adjust the voltage as forward voltage changes while in use (forward voltage varies with heat).. go on digikey.com or other similar sites, go to led driver ICs and filter them by "linear" regulation, select your maximum current, the voltage and then check out datasheets and see if you like a specific chip
--- End quote ---
Thank you for your input, I will give the chinese LED driver another go, I have unsoldered the transformer and took it apart to put some liquid epoxy in effort to make it silent. Lets see how that goes.
smile:
So epoxy dried and now the inductor is silent :-+
However it seems the LEDs are not full brightness even without any resistors. They are capped by PSU output power of 290mA.
Is there easy tweak like put bigger output cap or something to make output like 350mA etc?
I used this driver https://www.ebay.com/itm/300mA-4-7x1W-Led-Driver-4-7W-Power-Supply-AC-85-V-265-V-110-V-220-V-For-Light/132727839097?hash=item1ee7321979:g:-p0AAOSwEfBbYsS0:rk:2:pf:1&frcectupt=true
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