Aditya Engineering Co

In the past two years, LED street lights have been widely discussed since there exists a very large market and the LED’s power saving performance is obvious especially in replacing the 250 W or 400W mercury lamp. To build an LED street light, the key issue is needed to reach and meet a specific specification, for example, it needs to guarantee 5 years (since everyone knows LED life is 50,000 hours), the light pattern has a specific request to meet the roadway regulation specification, dust and water-resistant has to reach IP65, mechanism strength needs to be enough, etc. Based on these requests, to design the LED street light, one needs to consider the thermal, optical, power and mechanism. LED life depends on the LED junction temperature (Figure 1). Cree has announced data to show the relationship of life versus light maintenance for different junction temperatures. Therefore, to guarantee 50,000 hours life, the LED junction temperature has to be controlled under 75C. Fig. 3 (patent pending) As for the illumination uniformity of roadway, the batwing light pattern is inevitable. The cut-off light pattern for glare limitation is also required. The other important subject is about both the driver (power) design and LED light module design: we know that each LED has a little different drive voltage and we can not guarantee all of the same drive voltage LEDs have been built into the street light. So, a worse circuit design will induce a non-uniform current to drive the LED, which will impact each LED’s life. ADITYA knows all of the design issues that will directly affect the LED street light product quality, hence, ADITYA combined thermal/optical/power/mechanism to do a overall design to make sure of street light quality.