Blue LED Light Engine Design Considerations

Future Lighting's simpleLED light engine consists of three high- power warm-white LUXEON Rebel LEDs binned in ANSI with a correlated color temperature of 3000K, each producing a minimum luminous flux of 66 lumens. The light engine includes a Carclo three- lens base, a single-LED lens with a 20mm 35° frosted wide beam, and a Tyco Mini CT connector (Figure 4).

Figure 4 simpleLED light engine

White LED (WLED) deterioration over time

Traditional white LEDs are directly coated with yellow phosphor on blue LEDs . Since it is difficult to dissipate heat after white LEDs are lit, yellow phosphor is easily denatured under long-term high-temperature baking, resulting in poor color rendering index after long-term use. In LED lamps, if yellow phosphor is not directly coated on white LEDs, but made into a yellow phosphor color filter, and kept a certain distance from the blue LED in the lamp, the two can be used in combination to obtain the white or warm white light effect of LED lamps . Since the yellow phosphor color filter is far away from the LED heat source, it will not age and denature due to long-term high-temperature baking of the LED light source, and the CRI remains basically unchanged; the formula of the yellow phosphor color filter is adjustable, and the color and color temperature of the light can be adjusted according to the needs of customers, which can meet customized requirements and produce differentiated products.

Designing a blue LED light engine

The architecture design of the blue LED light engine is an innovative concept, completely different from the aforementioned white LED light engine. The blue LED light engine integrates the blue LED light source board, AC/DC constant current drive power supply board, and yellow phosphor color filter. Its architecture principle is shown in Figure 5. The AC/DC constant current drive power supply converts the mains power into a constant current DC to light up the blue LED light source. The blue light is filtered by the yellow phosphor color filter, so that the LED light engine emits white light or warm white light. The working principle is shown in Figure 6.

Figure 5: Blue LED light engine architecture

Figure 6 Working principle of blue LED light engine

Constant current drive power supply

The constant current driver is the power source of the entire light engine. Therefore, it is necessary to select a single-stage driver IC with powerful integrated functions and simple application circuits that can meet the light engine's requirements for the driver's energy efficiency, power factor, EMC , etc. The primary-stage controlled PSR power circuit can meet the needs and save space and production costs.

Figure 7 is a photo of the blue LED light engine designed and developed by Shanghai Sanpin Lighting. In a standard housing, the blue LED light source board is tightly mounted on the aluminum heat sink at the bottom. The circular PCB board is the constant current driver, and the power cord can be directly connected to AC. This blue LED light engine also has an intelligent control function for the internal temperature of the light engine. It has a built-in temperature sensor . When the temperature inside the light engine reaches the set protection temperature (75-80 ºC), the temperature control circuit starts to work and the output current decreases at a rate of 1/256 until the temperature of the lamp drops below the set protection temperature and the output current returns to normal. This is to protect the life of the LED light source and the driver. The constant current driver adopts a full voltage design, AC90-260V wide voltage range input, power factor (PFC)>0.9, efficiency>80-85%, color temperature of 2700-3000K, 5000-6000K, CRI>80 or above. If there are other color temperature and CRI requirements, they can be specially customized. There are two options: dimming and non-dimming. The outer side of the aluminum-based heat sink at the bottom is covered with an engineering heat-conducting plastic sheet imported from the Netherlands to enhance heat conduction. The external radiator can be conveniently locked through the three screw holes at the bottom of the aluminum-based heat sink. Figure 8 is the blue LED light engine series. To ensure quality, all yellow phosphor fluorescent filters are imported from the United States.

Traditional lighting fixture manufacturers and new LED lighting fixture companies can easily use this blue LED light engine in new LED lighting fixtures such as downlights, recessed lights, ceiling lights, etc. Blue LED light engines will be widely used in LED lamps for commercial lighting and indoor lighting, and the market prospects are very promising.

Figure 7: Actual photo of the blue LED light engine developed in Shanghai