LEDs come in various types, but before examining some of those, it’s worth looking at the two main ways that white light is produced in bulbs and fixtures.
By far the most common way of producing white light from LED technology is to pass the bright light of a blue LED through a yellow phosphor. One thing that determines color temperature in the light source is the thickness of the yellow phosphor coating. The more dominant the blue light, the cooler the color temperature is. The wavelength of the blue LED also influences this.
A second method of producing white light is to blend the light of red, green and blue LEDs. This trio of LEDs is known as an RGB LED. It is used in the latest “smart bulbs” and enables a huge palette of 16.77 million colors. However, it is too complicated and expensive a technology for use in everyday LED products.
Having looked at the two main methods of producing white LED light, here are some of the physical LED types:
An SMD (Surface Mounted Device) LED is soldered flat to a surface and emits a bright directional light. It is often mounted in 360° arrays or clusters to produce an omnidirectional light. This type of high-power LED is commonly used in LED light bulbs.
DIP LEDs are recognizable for their domed indictor appearance and were common in the earlier days of LED technology. They’re still made, though tend not to perform as well as SMD LEDs in terms of energy efficiency, color rendering or lifespan. For this reason, they are usually cheaper.
COB (Chip-on-Board) LEDs consist of multiple tiny LED chips tightly packed onto a single module. This creates a particularly intense, smooth light that is often described as looking like halogen light. COB LEDs are normally used in wide-beam spotlights.
COG (Chip-on-Glass) LEDs include multiple tiny LED chips densely arranged on a transparent substrate. This type of LED is used in modern LED filament bulbs.