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I have 12V CV driver. I need current regulator. But ı dont have much space on board run 2 -3 pieces rgbw led. as you know red light about 5V and blue 7V so if is there small package component? i can use it . Normally i can transistor but they cover much more area on board
You are corerct to drive with constant current, then brightness is
fairly well regulated. But that takes an active circuit. One of the
simplest is use a 3 terminal reg and a R to operate it in constant
current. But if you are delivering 350 mA into a load, say RED LED,
then LDO has to dissipate ( 12V - 5V) * .35 = ~ 2.5W, thats a lot of
power to dissipate, heat sink required.
If you dont want "active" regulation a resistor will do, except the current
will not be regulated.
Small board space .. and linear regulating constant current.
Are you aware that (input_voltage - LED_voltage) × LED_current is dissipated as heat?
No matter what circuit you use. Resistor, BJT, MOSFET...all the same power dissipation.
Then: the smaller the board space, the lees you can spread the heat ... resulting in high temperature.
Maybe too high.