0
\$\begingroup\$

I'm looking to run four 3 W high-intensity LEDs in a series circuit using a 12 V battery, for an outdoor lighting setup.

My intention was to use an adjustable buck/boost converter, as I've used to run a single 2 W LED. But I've heard that if I supply too much current I'll ruin the LEDs.

The LEDs each have a max. forward voltage of 4.5 V and a max forward current of 750 mA, so I assume I'll need to supply around 14 V and 600 mA, to run the LEDs at a little less than full capacity (for longevity).

I'm new to electronics, but I think I can run these with an adjustable buck/boost converter with the faciltity to adjust current too, such as this one.

Am I understanding this right?

\$\endgroup\$
1
  • \$\begingroup\$ I think that converter might work for this, but you will need to experiment a little. It says it has a constant-current mode. If that's true, it should work fine. I would crank down the current pot to the minimum, and set the voltage for somewhere around 20V (4x4.5V plus a little extra) to start. Then, slowly increase the CC pot until you reach your desired current. You may have to fiddle with the voltage some. \$\endgroup\$
    – Troutdog
    Jun 30, 2023 at 19:36

3 Answers 3

1
\$\begingroup\$

When using an LED you need to be able to regulate the current also, use a series resistor for current limit at minimum. But a resistor will burn up some of your power is heat. A better way if you want to save some power would be to use a DC to DC converter that has a current control function and to put the DC to DC controller in a constant current mode.

\$\endgroup\$
1
\$\begingroup\$

Yes, you can run your LEDs with a regulator like this, provided the regulator is up to its specs.

What you need to set is a voltage slightly above the total expected voltage over all LEDs (4 x 4.5V = 18V so something like 20V) and a current limit at how much you expect to drive them (600mA). When connected, the LEDs will pull the voltage lower.

Be sure to adjust the current limit with some dummy load first - if you start with 3A for 0.75A diodes, they will die in milliseconds.

p.s. a total of 12W LEDs will need to dissipate some 10W as heat. You need an adequate radiator(s) for them or they will overheat.

\$\endgroup\$
1
\$\begingroup\$

LEDs are current devices not voltage devices. Controlling the voltage will work but in a very narrow range. At 14V they will not be very bright if they light. You need to limit the current and let the LEDs determine what the voltage will be. They make constant current modules designed specifically to drive LEDs, they work well and are not that expensive. Search for: "led driver module". Using a SEPIC (Buck/Boost) converter not designed for this application will eventually fry the LEDs. Reason The current will fold back to slow over driving the LEDs.

\$\endgroup\$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.