| Title |
PWM Dimming Characteristics of the MHz band LED Driver Using GaN HEMT for the Solution of Camera Image Flickering |
| Authors |
인치각(Chi-Gak In) ; 김준석(Joohn-Sheok Kim) ; 오용승(Yong-Seung Oh) ; 오원석(Won-Seok Oh) ; 조규민(Kyu-Min Cho) |
| DOI |
https://doi.org/10.5370/KIEE.2020.69.2.283 |
| Keywords |
Camera; Flickering; GaN HEMT; MHz; Image; LED Driver; PWM Dimming |
| Abstract |
In this paper, we analyze the cause of flickering for the still image and moving image of the camera to solve the flickering image problem under the LED lighting environment controlled by PWM. Through computer simulation, the exposure dose according to the operating conditions of the camera such as exposure time, moving picture frame rate, and shutter opening instant and dimming control conditions of the LED lighting such as PWM frequency and duty is derived. A high-speed PWM LED driver using GaN HEMT, a high-speed switching element, is proposed as a countermeasure, and its PWM dimming characteristics are evaluated.
Experiments with three kinds of LED boards are performed. As a result, it is confirmed that 55.5 V, 40 W LED board and 220 V, 170 W LED board have an excellent linear illuminance control characteristics in PWM dimming of the MHz band. Moreover, it is confirmed that the flickering image problem does not occur even in the high-speed 960 fps shooting video in case of high-speed PWM over 1 MHz. |