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flowing through the LED, constant current control to achieve. Figure 3.1 MCU controlled constant current programs based on the overall block diagram of the 3.1 theoretical basis for the constant current control circuit topology of the circuit for the BUCK.
BUCK for the constant voltage output when the input voltage and output voltage relationship: type 3.1 can be seen from the output voltage and duty cycle and input voltage are proportional. In the closed-loop control, taking the output voltage feedback signal compared with the preset reference voltage when the input voltage is constant,display signs, if greater than reduce the duty cycle D, is less than the time when the opposite,LED billboard, increasing D, in order to achieve regulated effect.
So, when BUCK circuit for constant current control,display boards, as long as the voltage feedback signal into a current feedback signal can achieve constant results. 3.2 The advantages and disadvantages of the MCU control program of the constant current control of constant current, constant power control scheme for the problems can be a good solution; First, the deviation of the LED for the life and impact of color.
Constant current control scheme, when a deviation or as the temperature and working time changes,LED writing board, as long as D constant, the output current to the LED does not change much. Although LED forward current with temperature and working time change, but the deviation of each LED are not large, for the link up with multiple components of high-power LED LED lights, and will not the life of the LED and the color have any effect. Secondly, the use of closed-loop control, can achieve a high output current accuracy. Can guarantee the consistency of light. Again, the power of compatibility issues. MCU-compatible constant current control scheme below rated power LED lights.