The analog LED dimming design is simple and low cost, but it is not suitable for applications requiring stable color temperature; digital PWM dimming color temperature control is better, but it must be matched with MCU to increase system cost. Designers should consider the application requirements and choose the most suitable dimming solution to achieve the desired LED lighting color and brightness.
Color accuracy is important in lighting applications such as buildings, areas and xenon lamps, and light-emitting diodes (LEDs) are ideal for providing accurate color. LED color can vary with colors such as red, blue, green, yellow, and white; when multiple colors are mixed, the brightness must be adjusted. This article introduces the dimming techniques of various LED color mixing.
Accurate channel brightness control LED for rich color
Each LED crystal can only emit monochromatic light. If you want to create other colors, you can use the red, green and blue LED lights to mix, as long as you switch the red, green and blue LED channels, you can produce seven basic colors (red, Green, blue, yellow, purple, light green, white).
If you need more rich colors, you only need to control the brightness of the LED lights of the three primary colors to produce a variety of colors, including adjusting the brightness of each LED channel, and controlling the current control through the LED strings. When changing the color temperature of the LED white light, the red and white LED strings are usually adjusted.
There are two basic ways to adjust LED brightness: Analog and Pulse Width Modulation (PWM). Both control the average current through the LED string by installing a switch mode or a linear LED driver to change the brightness of the LED.
Figure 1 shows a dual-string LED driver that includes a buck switch and a linear regulator. Both LED strings can be selected analog or PWM, both of which have advantages and disadvantages. Most applications are based on the choice of color mixing performance.
Figure 1. A dual string dimmable LED driver with a buck converter and a linear regulator.
Analog dimming must master the magnitude of current change
LED analog dimming is to control the LED current reference voltage in the chip by controlling the constant current through the LED string, or to control the LED current sensing voltage outside the chip.
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