LED lamps differential design highlights in intelligent control

LED rash and too much in haste so long, one of LED more and more people, closures, mergers and acquisitions can not change the people's enthusiasm for LED, do the traditional lighting to LED lighting energy-saving lamp, do to do LED lighting lighting industry, as long as detached came to do LED, in this environment, see differences in the design.

The appearance of LED lighting has changed the way of lighting, and the intelligent control and color matching function in LED lamps have created new opportunities for designers. The LED has the advantages of high efficiency, light adjusting ability, long service life, etc., and the utility model has the advantages of high efficiency, cost saving, and easy fabrication. Digital signal controller (DSC) can drive a variety of innovative applications, to achieve more efficient LED drive, more accurate color control and external communication with a better. The advantages of the above collection allows designers to have greater freedom to develop highly differentiated LED lighting fixtures.

Low power indicator LED is essential for many products, most engineers are familiar with its simple design. As long as a voltage source and a series resistor with the correct values, the LED current can be maintained at a level of less than 5 ma. Through the universal input and output connected to the microcontroller (GPIO) pin, can let LED flicker; however, to more than 350 Ma forward current is connected in series with the formation of high brightness, high current LED, the design will become quite complex. Designers in the temperature changes and the high temperature of the LED itself, but also need to face the challenge of current control.

Figure 1: the use of pulse current dimming, color change is not easy to detect

Figure two: driving single LED or LED lamp string step-down Technology

Current control

High brightness LED should be maintained at a relatively high current to maintain a certain brightness and color. The flux of LED is proportional to the forward current flowing through LED. To achieve the same color and light output, the key is the constant forward current. The forward current changes with the voltage source, causing the LED to emit light. Therefore, it is necessary to use a power supply which can actively regulate the forward current to drive.

temperature control

In general, the forward voltage of LED increases with increasing temperature, even if the forward current is constant and adjusted. High power LED will generate heat, resulting in reduced LED life and early failure. The forward current of LED can be controlled by the forward current of the target and the forward voltage. A method for monitoring temperature conditions using a temperature sensor.

Color control

LED can almost instantly change the output light, suitable for the need to quickly change the color of the lamp. Simply adjust the brightness of each LED, you can create red, green and blue LED lights string any color. Increasing or decreasing the forward current of each LED is one of the methods, but the change of the forward voltage will not only change the brightness, but also change the color of LED. Applications that require precise color will cause problems.

Another method is to use the pulse current (pulsedcurrent), this method can provide the same dimming effect, but will not let the color visible changes. The red dashed line in Figure 1 represents the brightness variation of the average pulse current, while maintaining the consistency of the LED forward voltage. No perceptible change in color.