Optoelectronics Buck-boost converter


Buck-boost LED drivers regulate LED current from a supply that is higher or lower than the total LED string voltage. The converter modulates the high-side switch connected to the input voltage in the step-down mode and the low-side on the output-side in step-up mode. This topology is the most complex but also the most flexible. VIN and VOUT ranges are only limited by the controller IC. This is a good choice for matrix applications.


Conclusion


Automotive LED lighting systems can be driven with switching regulators in many


Figure 9. Buck-boost converter.


Benefits to Buck-Boost LED Drivers


Most versatile topology


May use matrix to short entire string


May use the same driver for multiple applications


Trade-Offs to Buck-Boost LED Drivers


A minimum of two switches and two freewheeling diodes is required


Typically, the lowest conversion efficiency


Typically, the lowest (worst) EMI performance


Applications High beam/low beams Turn signal


Daytime running lights Short safe systems


Table 5. Advantages and trade-offs of using buck-boost converters as LED drivers


different ways. Depending on the application, the selection of switching topology and configuration allows the lighting designer to create complete subsystems for the different lighting requirements throughout an automobile. Selecting the correct power conversion switching topology and configuration for the system optimises requirements such as complexity, efficiency, EMI, and safety.


https://www.analog.com/en


Figure 10. Buck-boost example: LT8391.


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