What is a Ballast and Why They are Not Used in LED Lights

Posted by James Cannon on 5/23/2017 to LED Parking Lot Lights
What is a Ballast and Why They are Not Used in LED Lights

What is a Ballast and Why They are Not Used in LED Lights

When light bulbs were a new invention, a device was placed within the bulbs. The purpose of this device was to limit the amount of current in an electrical circuit. This device is known as a Ballast. If this was not used in the light bulbs and T8 light bulbs (tube Lights), there remained a risk of current rising to a destructive level. Ballast is still used in bulbs and tube lights to avoid current rise in the lights. Metal halide, mercury vapor, and HID are also the prime examples of lights using ballasts. 

There are two main types of ballasts; magnetic ballast and electric Ballast (aka Electronic Ballast) and we will review both.

Magnetic Ballast 

Magnetic ballasts are basically inductors that provide the proper starting and operating electrical condition to power certain lamps.  The work as a transformer, providing clean and specific power.   Invented in the 1960’s, they say big usage in the 70-90s.   They are seen in Metal Halide, mercury vapory, florescent lamps, neon lamp, or High Intensity Discharge (HID) lamps.  Almost all major parking lot lights and street lights used this technology for about 30 years before LED started taking over around 2010.  

Electric Ballast

In an electric ballast, an electric circuit is used to limit the load or amount of current.   The electronic ballast attempted to maintain a more stable and precise current flow compared to the magnetic ones.   These became popular in the 90s and through today where they are still installed.  Believe it or not, even in 2017, some people are not buying LED light bulbs and still choosing old technologies.

Function of a Ballast 

A ballast regulates the current to the lamps and provides sufficient voltage to start the lamps.  Lamps have no regulator and can draw too much or too little power on their own.  The ballast makes sure that the amount of current being provided to the lamp is not more than the specification of the light. Without a ballast, a lamp or a bulb will rapidly increase its current draw and it can become uncontrollable as well. 

When a ballast is present in a lamp, the power becomes stable, and even if such lamps are connected to high power sources, the ballast will regulate the energy and avoid the current rise. 

Why LEDs don’t use a Ballast

LEDs don’t need a ballast because of a number of reasons. First, large amounts of current aren’t needed in LED bulbs. Also, the LEDs typically use Direct current (DC) and thus need an AC to DC converter.  This is why when retrofitting to LED Corn Light Bulbs you need to direct wire the socket.  Lastly, the size of LEDs is much smaller than bulbs and tube lights, which leaves no extra space for a ballast to fit in.  LED drivers can be engineered to be much smaller. Some technicians also believe that the absence of a ballast make LEDs energy efficient and they provide better light. 

The real answer here is that LEDs use a driver, which does many of the same things as a ballast but operates much more effectively.  

LED Driver inside a parking lot light


What is an LED Driver 

An LED driver is an electrical device which regulates the power to an LED light. It has the capacity to regulate power to a single LED Light or strings of LEDs. An LED driver responds effectively to the changing power needs of the LED.  The drier provides constant and uniform levels of power to the LED as its electrical properties change with temperature. LED drivers may become dim by means of pulse width modulation circuits and may have more than one channel for individual control of different LEDs. The power level of the LEDs is maintained at a constant level and it is done by the LED driver. The LED driver acts in the same way as the ballast but it is more efficient. 

 

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