The Study And Design Of HB LED Driver

HB LEDs(High-brightness Light Emitting Diodes) have been used in wide applications, such as LCD background light, electronic bulletin board, traffic signals, indoor lighting, building lighting and automobile taillight because they have higher light brightness, higher efficiency, higher reliability, longer lifetime and multicolor. In these fields, adjustable light brightness function is required. So the design of HB LEDs driver becomes a hot point, which provides high integration, simple output circuits, high efficiency, high power and adjustable light brightness function.In this thesis, it focuses on designing an adjustable HB LED driver with mixed modulation. Based on the topological structure of conventional buck converters, the circuit switch on or off of power transistor is operated by sampling voltage obtained from high side current sensing circuit, then comparing it with internal reference voltage by the comparator with hysteresis characteristic. So the circuits reach stable state just one oscillation period rapidly. In the other hand, the current through the HB LED is precise and controllable because the sampling voltage is precisely controlled. Finally, to this chip, three methods for adjusting light brightness are presented. Single or multi-cascade HB LEDs can be easily driven by the circuit with some simple output component and good performance will be obtained.In this thesis, an adjustable HB LED driver has been done with BCD technology. The simulation of whole circuit indicates that the IC has achieved our expectation including function and parameter target. The circuits have been delivered for processing.