ac led driver circuit design
By limiting the level of LED power, usually need to drive multiple LEDs at the same time to meet the brightness requirements, therefore, need a special drive circuit to light the LED.
The use of flyback circuit, through the transformer in the secondary side of the DC level, and then through the optocoupler this level of the ripple back to the original side, and thus self-stabilization. Such circuits meet the safety requirements, and the output constant current accuracy is better, the conversion efficiency is higher. But because of the need for optocoupler and secondary constant current control circuit, resulting in complex system, large size, high cost. Has been gradually replaced by the original side program.
3, the original side of the program
The original side of the program is completely through the control of the output side of the power and current output, the most accurate can do 5% constant current accuracy, the secondary only a simple output circuit can be. The primary side relies mainly on the feedback of the auxiliary side to control the output voltage, relying on the current limiting resistor to control the primary current, and multiply the turns ratio to control the output current accuracy. The original side program inherits the advantages of the isolated flyback circuit, while the architecture is simple, can be small size and low cost, has become the mainstream drive.
The original side of the constant current accuracy problem: the production accuracy of the pressure is difficult to control, resulting in the original side of the program in the use of low-quality transformers, the output current drift larger. Therefore, the primary side of the program by improving the secondary side of the constant current control circuit, so that although the original side of the original program than the complex, but compared to the flyback program, you can still save the optocoupler, the system cost-effective.