Constant Current – Constant Voltage – Low Voltage LEDs and Their Driving Circuits


As LED technology develops and new solutions appear on the market almost every week, it is getting more difficult to find out which solution is the best for your applications and most importantly, what features you have to pay attention to during purchase. In my previous article at about general features of LED transformers I already mentioned that LEDs require special transformers features.

LEDs are highly sensitive to changes both in voltage and current, so if you are dealing with low voltage LED lights, wire-wound, stabilized transformers are the safe solution. As indicated in the article, the majority of household LED lights operating at low voltage require constant voltage drivers for their operation. However, recently, with the increase of high power LED technology, constant current circuit solutions are becoming more frequent. Below, I will give a short description of how these circuits work, and why it is necessary to pay attention to details at the purchase of the driver for these applications.

Three components matter in the operation of LED lights: voltage, current and heat. LEDs are highly sensitive to a change in all three of these, so their regulation is very important for gaining a long lifespan. Current is often looked at as an exponential function of voltage, therefore even a small volume of change in voltage can result in a large change in the current. This is exactly why the majority of the LED lights need stabilized constant voltage power supply. However, current load can also increase with the increase of heat. To avoid overloading, LEDs are driven from low voltage DC via a current limiting regulator or constant current regulators. Another additional solution is the cooling of the LEDs with heat sinks. Not all LEDs are attached to heat sinks though, which is why the limit on the hours of application is so important. If LEDs are operated longer than they are supposedly to, they overheat, increasing the current (even if within the range limited by the resistor), and lose some of their lifespan.

Constant current circuits are especially safe for high power LED lights, as they are suitable for 24/7 operation. If the LED light is manufactured with constant current circuit, the current is fixed by the stabilized transformer, and it does not generate further heat inside the LED light. By less heat generation, the LED gains a longer lifespan. Also, constant current source keeps the LEDs brightness constant. These constant current lights are, however, not suitable for operation with 12V batteries, since batteries are constant voltage power supplies.

There are obviously advantages of both circuits, and as usual we could conclude that details matter. Never use a light requiring constant current with batteries or constant voltage power supplies. Always check this feature of your light, and buy the necessary transformer. And if you would like to know more about LED lights, check out the rest of my articles or contact us at

Source by Anita Samuelis

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