Volt-ampere characteristics of LED

High-power LED 1W red light, imitation lumens LED Sanan 30mil gold wire, copper bracket, 40

When designing a high-quality LED driver, it's essential to have a solid understanding of the electrical characteristics of the LED itself. LEDs are nonlinear devices, meaning their behavior is not as straightforward as resistors or capacitors.

As illustrated in the graph below, an LED with a rated current of 20 mA and a forward voltage of 3.3 V shows a highly non-linear volt-ampere curve. This means that even small changes in voltage can result in large variations in current. Since the brightness of an LED is directly proportional to the current flowing through it, maintaining a stable current is crucial for consistent performance and longevity.

To achieve this, a constant current driver is typically used. This type of driver ensures that the current remains steady regardless of fluctuations in input voltage or temperature. One example of such a driver is the 029967 constant current control chip from 02MICRO, a leading company in CCFL inverter and LED driver technology.

This chip was used in the design of an LED driver solution for a 32-inch LCD TV backlight. The system uses a 6-channel driver capable of handling 120 mA per channel. A total of 150 white LEDs were arranged in series, with 25 LEDs per channel, providing efficient and uniform lighting for the display.