Abstract: The main objectives in driving multiple LED strings include achieving uniform current control and high performance PWM dimming for all strings. This work proposes a new multiple string LED driver to achieve not only current balance, but also flexible and wide range PWM dimming ratio for each string. A compact single-inductor multiple-output topology is adopted in the driver, accompanied by synchronous integrators and variable dimming frequency, to achieve both high efficiency and high performance dimming. By using the proposed variable dimming frequency scheme, high dimming frequency is applied to a string with high dimming ratio, which helps to maintain the deviation of LED string current in an acceptable range, while low dimming frequency is applied to a string with low dimming ratio, which helps to achieve rectangular LED current waveform. Meanwhile, the new time multiplexing control scheme automatically optimizes the LED string's bus voltages, thus minimizes each string's power loss. A three string LED driver prototype is constructed to validate the effectiveness of the peoposed control scheme, where the three strings can have different dimming ratios between 4% and 100%.

Showing 1 to 1 of 1 Articles

Articles per page

Browse All Journals

Related Journals:

IEEE Journal of Solid-State Circuits IEEE Communications Surveys and Tutorials IEEE Transactions on Communications Electronics Letters IEEE Antennas and Wireless Propagation Letters IEEE Transactions on Circuits and Systems II: Express Briefs IET Electric Power Applications IET Radar, Sonar and Navigation IET Power Electronics IET Microwaves, Antennas and Propagation