Boost is an important task for LED drive circuits, and inductor boost and charge pump boost are two different topological modes. "Because LEDs are driven by current, and inductors have the highest efficiency in current conversion, the biggest advantage of the inductor boost method is high efficiency. If properly designed, it can exceed 90%; but its disadvantages are also obvious. Electromagnetic interference is very strong, and the system requirements for communication products such as mobile phones are very high. With the advent of charge pumps, the boost method using charge pumps will have lower efficiency than the inductor boost.
Whether in lighting applications or backlight applications, improving the conversion efficiency of drive circuits is a problem that product designers must face. Improving the conversion efficiency is not only conducive to extending the standby time of portable products, but also an important means to solve the problem of LED heat dissipation. In the field of lighting, it is particularly important to improve the conversion efficiency due to the use of high-power LEDs.
In addition to the LED drive circuit to meet safety requirements, the other basic functions should have two aspects:
The first is to maintain the constant current characteristics as much as possible, especially when the power supply voltage changes within ± 15%, the output current should still be maintained within the range of ± 10%. The main reasons are: 1. Avoid driving current exceeding the maximum rating Affects its reliability. 2. Obtain the expected brightness requirements and ensure the consistency of the brightness and chromaticity of each LED.
The second is that the LED drive circuit should keep its own power consumption low, so that the system efficiency of the LED can be maintained at a higher level.