/diy/ - Do It Yourself

>>1566844
I tried this with the LM2575-ADJ and it works very well as a switch-mode constant current source.

I improved on this circuit by replacing the "high-side" resistor/transistor network with a "low-side" sense resistor connected in series with the load. The sense resistor provides a voltage signal corresponding with the load current. The sense voltage is fed into an LM358N op-amp configured as a non-inverting amplifier with a gain of 2 or so. Its output then drives the FB pin of the LM2575. This allows to use a sense resistor with lower resistance value (lower power loss, better efficiency).

I'm looking for a way to drive a small low-voltage light bulb from a 12 V battery pack with high efficiency. I found this circuit that uses an LM2575 switching regulator to deliver a constant current into a load.

Is there any way to control the lamp current with cmos logic (or microcontroller i/o) pins? I'd like to (at least) be able to control the lamp current between two settings, namely: bright light for normal operation and power saving.