What factors need to be considered when designing a small color LCD display? part one

Over the past few years, small color LCD displays have been integrated into an increasingly wide range of products. Color displays were once considered a luxury feature in mobile phones, but now they are standard even in entry-level phones. Fortunately, the economics of scale of the mobile phone industry (annual global mobile phone shipments are approaching 1 billion units) have reduced the cost of LCD color displays and enabled their integration in everything from portable medical devices to universal entertainment remote controls to digital photo frames/image viewers. devices, educational toys, or the latest WiFi-enabled VoIP cordless phones, among other products.

Color LCD matrix display requires white backlighting so that users can view them properly in any lighting environment. This backlight subsystem includes a high-brightness white light-emitting diode (LED) array, a diffuser to diffuse the light, and a backlight driver to stabilize the available power into a constant current to drive the LED. A 1 to 1.5-inch display might contain 2 to 4 LEDs, while a 3.5-inch display might easily contain 6 to 10 LEDs. For LEDs, the light output is directly proportional to the current, and since LEDs have a very steep current-voltage (I-V) curve, it is very important that the current flowing through the LED is closely matched to ensure a balanced backlight, since the LED is usually distributed in One side of the LCD display. In addition, software control is also needed to allow users to adjust brightness and compensate for the surrounding lighting environment. Depending on the current flowing through the LED, the color point of the LED may drift. Therefore, it is common to set the LED current to a fixed value and pulse-width modulate the LED to reduce the average light output. There are a number of factors that need to be considered when integrating a small color LCD display into a handheld product design and achieving the right balance of cost, performance and battery life.