Hi,
Long story short: I'm trying to find a suitable regulator for dimming LED:s in a boat. The boat previously had halogens with a simple potentiometer dimmer. The bulbs were replaced with voltage-regulated dimmable LED:s. However, as expected, the old dimmer isn't suitable for the low-current LED:s. First, I looked into replacing the pots, but with the relatively high power dissipation in a semi-enclosed space, I realized that the approach probably wasn't suitable.
PWM-controlled LED:s could be an option, but flickering is a problems since the frequency would have to be low because of RF-interference.
Now I'm searching for a suitable buck-converter module, but find myself lost in the jungle of options. My two worries: low enough "forward voltage" ie, 1.5V drop won't allow full brightness on half-full batteries. The other is output noise - there is VHF and FM-radios close to the dimmers and interference is understandably unwanted.
Switching converters would allow for better efficiency and lower Vf (if i understand correctly), while linear converters wouldn't be noisy. However, my understanding is, that for example the LM317 has a Imin of over 1A and a Vf of 1.5V, and the dissipated heat would have to be accounted for.
Vin: 12.5-13.5V
Vout: around 7-12V
Imax: around 170 mA @ 12V - drops to 4.2mA @ 8.2V
I haven't got around to building my adjustable PSU yet, so the measurements were done using power bricks and resistors, therefore the missing values at lower voltages