LED lighting is changing the way people use lighting, which in turn opens up new opportunities for designers to incorporate intelligent control and color mixing into LED lighting. DSC can drive innovation in a wide range of applications: from car headlights and taillights to state-of-the-art lighting shows, which transform a public building into a work of art.
The unique combination of high energy efficiency, dimming and long life of LEDs makes color-changing lighting devices more efficient, less expensive and easier to implement. Combined with a digital signal controller (DSC), efficient LED driving and accurate color control as well as communication with the outside world can be achieved. All of these features provide a space for designers to develop distinctive next-generation LED lighting fixtures.
The higher the brightness, the more complicated
Low-power indicator LEDs are important in many products and most engineers are familiar with their simple design: all they need is a power supply and a series resistor with the appropriate resistance to keep the LED current below 5 mA. Typical value. The designer can connect the LED to the GPIO pin on the microcontroller to flash it. However, by connecting high-brightness, high-current LEDs (with forward currents in excess of 350 mA), simple LED designs can become quite complex. At this time, in addition to the temperature changes and the extremely high temperatures generated by the LED itself, designers are also faced with the challenge of controlling current.
Figure 1: Luminous flux is proportional to forward current
Intelligent current control
High-brightness LEDs need to maintain a relatively high constant current to maintain brightness and color. Figure 1 shows the proportional relationship between the luminous flux of an LED and the forward current (IF) flowing through the LED. Therefore, keeping the forward current constant is critical to achieving consistent color and light output. When using a simple resistor and LED series circuit, the forward current can be determined by the following formula:
IF = (VSource-VF)/R
When the supply voltage (VSource) changes, the forward current will change, causing the light energy emitted by the LED to also change. Therefore, it is necessary to use a power supply that can effectively regulate the forward current to drive the LED.
temperature control
In general, the forward voltage (VF) of an LED increases with increasing temperature, even when the forward current is constant and stable. Figure 2 shows the situation where the unregulated forward current is consistent with the forward voltage of the LED and explains why controlling the forward current through the LED is more important than controlling the forward voltage.
Figure 2: Effect of forward voltage change on forward current
The high amount of heat generated by the high-power LED itself can result in a significant reduction in LED lifetime and possible premature failure. For each design, effectively controlling the forward current of the LED requires determining the level of heat dissipation based on the target forward current and the predicted forward voltage. Temperature sensors can also be used to monitor possible overheating conditions.
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