Tech Primer
LEDs are gradually replacing traditional incandescent lamps in many applications, both domestically and commercially due to their high efficiency and long lifetime, which results in lower running and service costs. One notable application in which LEDs are gaining favour is traffic signs and signaling, specifically traffic lights. Different countries have different requirements for the saturation, brightness and scattering angle of traffic lights, as well as the electric properties such as power consumption and efficiency, mandatory regulations that must be followed during the design of a traffic light. Traffic lights use high brightness LEDs connected in a combination of series and parallel to build an LED cluster, to realize a specific lighting distribution intensity additional optical design (lenses and / or diffusers) maybe necessary.
Owing to the AC power supply that is usually used for traffic lights, a DC to DC converter is required to provide the DC power that the LED cluster requires. Typically a Buck or Buck-Boost DC-DC converter is used to provide the necessary conversion. Care should be taken to ensure that the power factor of the converter is acceptable and ideally the power factor should be corrected to achieve a high P.F. Consideration should also be given to the operating temperature as excessive heat will degrade the LEDs output and life expectancy.
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