An LED constant current driver is a voltage converter that transforms a power supply into a specific voltage and current to drive an LED. Its input typically includes high-voltage AC (mains power) or low-voltage DC, while the output is usually a constant current source whose voltage changes with the forward voltage drop of the LED.
Its core components typically include a switching controller, inductor, switching devices (such as MOSFETs), feedback resistor, input filter, output filter, and various protection circuits as needed. Based on the driving method, it can be mainly divided into two categories: constant current and regulated. The constant current driver circuit outputs a constant current, while the output DC voltage varies within a certain range depending on the load resistance, making it a more ideal method for driving LEDs.
The constant current control method of LED constant current drivers has evolved from feedback control using comparators to feedback control using A/D converters, the latter offering higher accuracy and lower ripple.
The core control chip has evolved from traditional secondary feedback schemes to primary-side constant current control (PSR) technology, simplifying peripheral circuitry. This has led to the emergence of single-stage APFC control chips with integrated power factor correction (PFC), improving power factor and efficiency. For example, BPSEMI launched the BP31XX series driver chips with primary-side constant current control (PSR) in 2011.
In terms of system architecture, distributed constant current technology has been proposed and developed. This technology advocates "constant voltage first, then constant current," combining constant voltage switching power supplies with distributed constant current technology.
Overall, LED driver power supplies are developing towards higher precision, higher efficiency, smaller size, fewer components, and greater intelligence. More refined control methods, such as individual channel constant current, are considered the future trend.
