Ed is becoming the mainstream device for small and medium color display backlighting applications. The choice of led is the key factor in determining the best cost performance for the subsystem design. In addition, LED driver ICs can work with lower cost LEDs to improve the performance of existing LEDs in a variety of ways. In addition to brightness control, these driver ICs enable precise brightness matching or allow the use of a range of LEDs with different VF characteristics. This article describes various LED-based backlighting design options, as well as considering cost factors and various designs. How to optimize system performance under the premise of the advantages and disadvantages of the method.
When LED driver circuit designers choose LED driver circuits for portable applications, cost and performance factors are generally considered. One constraint in system design is available battery power and voltage. Other constraints include functional features such as tuning for ambient light and building an LED architecture.
LEDs can be screened for different parameters, including forward voltage and chromaticity and brightness for a specific forward current. For example, white LEDs typically have a forward voltage range of 3.5 to 4 volts and a typical operating current of 15 to 20 mA. When multiple LEDs are used in a backlighting device, these LEDs are typically matched to produce uniform brightness. Therefore, LED manufacturers provide "differentially screened" or matched LEDs whose VF or other parameters match within a certain voltage range. These flaws. The difference is usually 3.5*3.65V, 3.65*3.8V, and 3.81.0V. The specified voltage of Fairchild's latest products is 3丫. Low-profile "LED small display device applications, as for larger color displays, which usually require higher brightness, generally use medium to high VF LEDs. In general, LEDs are an important parameter in system design. Because they are powered by ordinary batteries. Portable products such as cellular phones use a single lithium-ion battery with a voltage range of 2.7*4.2V. If the system's battery operating voltage requirements are not less than 3V, designers can use as low as 3V directly. The regulated battery voltage drives the LED. Other matched levels of difference include luminous intensity and chromaticity. Chromaticity determines the color of the display, mostly related to the semiconductor process used to perform the design. Electrical operating conditions have a significant impact on chromaticity. Small. For luminous intensity, the screening process measures the intensity of the illumination at a given forward operating current.
Currently, there are driving ICs capable of driving multiple LEDs, the functions of which include voltage boosting to drive multiple series LEDs for current matching with multiple columns of LEDs containing one or more LEDs per column. The specific driver 1C provides accurate current matching independent of the LEDVF, and the use of such ICs eliminates the expense associated with VF differential screening. Another common feature is brightness control, which helps provide more features and improved power management.
Connect multiple LEDs together using CTé’†(4) flawless boost (to boost the drive circuit with additional series LEDs to match LEDs)
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