LED technology (light-emitting diode) consists of a p–n junction diode that emits light when power is applied to its two connections. When power is applied, electrons are able to recombine with electron holes within the LED, releasing energy in the form of photons. This effect is called electroluminescence.
While LEDs appear to run cooler at the front than more traditional lighting sources such as HID or quartz halogen, what many people don’t realise is that large amounts of heat are discharged into the rear of the lighting unit. This is where well designed, heavy duty heat-sinking becomes a critical part of the LED system. Without it, the LED would start to overheat with a drop in light output and product lifespan as a result.
HID technology (high intensity discharge) consists of a globe, starter and ballast connected to power. The globe is a quartz tube filled with Xenon gas, with tungsten electrodes housed at each end. The bulb functions by running 23,000 volts through the tube (generated by the starter) that ignites the gas and produces an arc of light between the electrodes. Once ignited, the ballast regulates the voltage back to 85 volts to keep the arc running.
Standard headlights use 55 watt quartz halogen globe types and have an average lifespan of 200 hours of operation. 35 watt HID globes in comparison generate around 3 times the light output of a 55 watt quartz halogen while using a third less power. They also have a lifespan of about 2000 hours—about ten times that of quartz halogen.
In short HID globes are brighter, last longer, use less power, and produce light that is closer to daylight in colour as compared to traditional quartz halogen globe types.