LED constant current driver

1. Introduction:
The constant current regulation module for the light source driver includes a voltage reference, comparator amplifier, regulating transistor, sampling resistor, and balancing resistor. In the light source current regulation module, this system uses a three-terminal adjustable shunt regulator TL431 as the circuit's reference voltage source. It has excellent thermal stability; connecting the reference terminal to the cathode results in the output voltage being the reference terminal voltage, providing a stable 2.5V reference source. An AD8552 is used as the comparator amplifier. This chip is a zero-drift dual-channel rail-to-rail operational amplifier, single-supply driven, with a noise voltage of 0.32μV, input voltage drift of 0.003UV/℃, and an ultra-low input bias current of 20PA. It requires virtually no external circuitry and excels in drift suppression, commonly used in high-precision systems. For the large current required by the light source, an N-channel enhancement-mode MOS transistor IRF520 is used for current regulation. The IRF520 features high power, high speed, high gain, and high voltage withstand capability, along with a wide safe operating area and good heat dissipation stability. The on/off module of the driver circuit uses analog switches, optocouplers, and other components. For dual light sources, the dual-channel P-channel Mose chip Fds6875 is used, offering a very fast switching speed. Meanwhile, to reduce interference from the light source driver module circuitry to subsequent digital module circuits, a dual-channel controllable optocoupler TLP521-2 is employed, completely isolating the front end from the subsequent load and increasing circuit safety.