LED backlight driver module design circuit diagram

Circuit Analysis: The requirement of backlight driving is that the brightness of the backlight LED does not change under any conditions, that is, a constant current source circuit needs to be constructed. The backlight driving circuit shown in the figure is the simplest constant current source circuit. When the circuit operates, the voltage across the resistor R9 is equal to VLL1 plus the BE pole conduction voltage, which is a fixed voltage of about 1.7V, and the current flowing through R9 is also fixed. The current is approximately equal to the emitter current and collector current of Q2, so the current flowing through the backlight diode D1 is also a constant current, and the constant current driving of the backlight LED is realized. The driving current of the backlight LED is about 10 mA, and the value of R9 is 150 Ω.