Hybrid low frequency switching linear LED driver for controlling dimming range

Abstract

LED lighting has been widely utilized in different application scenarios. To save energy and cost, dimming technologies have also been developed so that the lighting can be dimmed in different situations. Wide dimming range is useful for accommodating very different operating conditions. Traditionally, there are different categories of dimming methods, including analog dimming and pulsed width modulation (PWM) dimming. In analog dimming, the amount of LED current used to drive the LED light is conventionally determined based on the amplitude of an analog signal. Since there is current level adjustment in analog dimming, inherently there is a disadvantage where colour temperature variation can occur. The use of analog dimming (especially at low dimming levels) is not recommended in applications where colour of the LED is critical. In PWM dimming, the amount of the LED current used for driving the LED light is usually determined based on the pulse width and period of a PWM signal. When the dimming level is decreased and the on-duty state of the LED current is shortened, human eyes perceive a flicker of light. Thus restricting the dimming range (threshold on minimum pulse width) to achieve predictable performance from the LED product. The main objective of this proposed work is to design and build a new hardware model of hybrid low frequency switching linear LED driver for controlling dimming range with respect to dimming levels by using suitable methods at particular level of dimming. The performance of the proposed system is verified through hardware testing and using LT-SPICE simulation tool.