MCU를 이용한 POWER LED의 효과적인 Dimming 제어

Abstract

Analog, PWM(Pulse Width Modulation) and FM(Frequency Modulation) control have included the dimming methods for POWER LED. Analog dimming is achieved by adjusting forward current of POWER LED. Although it is possible to adjust linearly brightness levels between 0 % and 100% by analog dimming, it makes a variation of wavelength by changing the POWER LED's forward current. PWM dimming is achieved by applying full current to the POWER LED at a reduced duty cycle. Generally, it is known that PWM dimming doesn't make variation of wavelength. However, it makes difficult to adjust linearly bright level between 0 % and 10%. Frequency Modulation Dimming method that maintains the average duty cycle in a specified time period can be used to dim POWER LED. Although Frequency Modulation dimming method is same to dimming result by PWM in aspect of wavelength, this method has problem of flickering at low level dimming. In order to complement disadvantages of existing dimming methods, an optimal dimming method was proposed in this paper. Proposed Dimming method uses PWM Dimming method at Dimming Range Between 10% and 100% and it uses the Analog dimming method changing the amplitude of PWM waves below 10%. Experimentally, proposed Dimming method was shown to be possible to adjust linearly brightness levels between 0 % and 100% and represented a constant wavelength output in various Dimming levels between 10% and 100%.