I've recently started a project that has some pretty loose specifications. I need to develop an LED driver that can take an input of somewhere between 7.2 and 24V, and drive an LED panel at 30V with a max of 0.7A. However, via a microcontroller I need to be able to adjust the output current to alter the brightness of the panel.
I've had a look around and I can't really see any sort of boost converter that will allow me to easily adjust the current, so I'm a bit stuck in terms of the parts I'd have to use for this.
My thoughts so far are possibly a configurable boost regulator strung in line with a constant current source, linked to a digital potentiometer. This seems a little messy though, there's surely an easier way…?
Best Answer
What you normally do is configure the LED driver to output the current that corresponds to maximum brightness and use PWM dimming from the microcontroller when you need a lower brightness, without changing the driver's current. It is easier to implement and avoids the issue that the color of a LED changes at very low currents, eg. a nice warm white LED could look greenish. With PWM dimming the current and therefore color is always the same, you only change the duty cycle.
So what you need ideally is a 0.7 A boost LED driver (current-regulated) with a PWM dimming input. Are you looking for a ready-to-use module or a chip that you'll integrate into your own circuit?
You could use a voltage-regulated boost converter followed by a step-down current regulator/LED driver, but in this case the losses will add up, eg. if your regulators are 85% efficient each you will have an overall efficiency of 72% only.