This paper proposes a new digital constant-current control method for high-power LED drive based on buck-boost topology. In this control system, buck-boost topology is used as the power conversion. The output voltage can be either higher or lower than the input voltage in buck-boost topology. Therefore, it solves the problem that in the buck topology the input voltage is required to be always higher than the output voltage. Furthermore, according to the input and output parameters, the duty cycle data which are used to maintain output current constant can be calculated in advance, and stored in the embedded chip. Thus, it can reduce the calculation of the embedded chip and solves the problem that the existing digital constant-current controllers need the high-speed analog-to-digital converter. In addition, in order to reduce the error generated in above calculation, the double threshold feedback circuit is used to fine-tune the duty cycle and makes the output current more steady and accurate. Meanwhile, due to adopting full-digital control, the brightness and flicker frequency of load LED can be conveniently regulated by modifying the system firmware. Therefore, this method can apply to the device of illumination, lighting decoration, visible light communication and so on.
Robust Tracking Control of a Three-Phase Charger under Unbalanced Grid Conditions
