Integrated Drivers Manage Multiple LEDs in Complex Displays

摘要

The growing demand for color displays in cell phones, digital cameras and PDAs has created a huge market for white LEDs as backlights in these applications. Because white LEDs require low dc voltage between 3V and 4V, and provide the miniaturization needed, they are becoming the light source of choice in color LCD displays employed in myriad small handheld electronic devices. Unlike their CCFL counterparts, which require a very high (200 to 500Vrms) ac waveform and an expensive and bulky transformer-based circuit for power, white LEDs' relatively low dc voltage means that simple inductor-based or capacitor-based circuits can be used to drive them. As more features are added to these handheld gadgets, associated color displays also are getting more complex with all kinds of LEDs lighting the screen. As a result, the chips driving and controlling white and other LEDs in a single display system have evolved over the last few years. In fact, these simple LED drivers are now complete lighting management solutions on a single chip. Several suppliers have emerged to grab a piece of this growing pie