Dimming is a commonly used technology in the lighting industry. For filament lamps, dimming technology can be easily realized on them in the case of low production costs. While LED dimming technology is much more difficult. For architects and ordinary families, they have no willing to lose the dimming function in the process of replacing traditional lamps with LED lighting products. In this article, we will give a small talk on LED dimming technology to provide some helpful information for someone needed them.
Power Factor (PF) is a rather important parameter among electrical appliances. A higher PF can effectively reduce the energy consumption of distribution network. Thus regulatory agencies around the world are striving to restrict the PF of their electrical appliances within a reasonable region. Energy Star Solid-state Lighting Efficiency Certificate is one famous example, in which the PF of residential electrical applications should be larger than 0.7 and the PF of commercial applications should be larger than 0.9.
There are three major methods for LED dimming technology. All of them realize the dimming function through changes of LED drives current. They also can be divided into simulated dimming and PWM dimming on the base of different circuit systems.
1) Dimming LED lights by modulating the derive current. Brightness of LED chips is proportional with the LED drive current, therefore it is available for us to dim LED lights by varying the input current.
2) Pulse Width Modulation (PWM). ① Convert the input current into square waves, increasing its pulse width; ② Adjust the constant lighting time by adjusting the pulse width, realizing the PF control and dimming at the same time. The dimming frequency is about 200Hz – 10KHz. Due to the visual lag of our eyes, flickers cannot be seen by us. PWM are good at improving cooling sections, which is the biggest advantage of it. However, it also has defects: the excessive input pulse may reduce the service life of LED chips. Currently, PWM is the most common method in LED dimming area.
3) VID (voltage ID) method. The linear increase or decrease of drive current will have less effect on LED chips. This method is a simulation of power-on/power-off state, also named linear dimming method.