Today, LED lighting has become a mainstream technology. The technology is maturing, and one of the signs is the introduction of a large number of LED lighting standards and specifications. Strict efficiency requirements have existed for quite some time and will continue to improve in the future. Recently however, the working LED lighting designers but more difficult, because to meet the following two requirements: it is necessary to use a dimmer for incandescent lamp to achieve dimming control function, but also to achieve high power factor performance .
Dimming is a very common feature of lighting systems. For incandescent lamps, it can be easily implemented at low cost. The dimming of LED lights is difficult, but for architects and residential users, they are reluctant to lose the advantages of dimming control when switching to LED lighting.
Power factor is a very important factor because high power factor can reduce the loss of the distribution network. The most effective way to reduce the impact of electricity use on the environment is to reduce waste, so regulators around the world are further tightening their power factor specifications. An example of this is the Energy Star Solid State Lighting Energy Efficiency Specification (09/12/07), which states that the power factor (PF) for residential lighting products should be greater than 0.7 and the power factor (PF) for commercial lighting products should be greater than 0.9.
Figure 1 LED bulb construction diagram
LED bulb and luminaire manufacturers are responding to these requirements and naturally want their products to be as versatile as possible. Therefore, they are in great need of LED driver circuits compatible with various dimmers to achieve high efficiency and power factor of 0.9 or higher.
Dimming controller
The lighting controller operates in either line dimming or secondary side dimming. The simplest line dimming method is the leading edge thyristor controller. This is currently the most commonly used lighting control method, but unfortunately, the use of thyristor controllers to dim LED lights can cause a lot of problems. More advanced line dimmers are electronic leading or trailing edge dimmers. The secondary side electronically controlled dimmer is used in professional lighting systems.
The performance of thyristor controllers in incandescent lamps is impeccable, but there are various negative effects in LED lamps, including flicker, uneven illumination, audible noise, and flicker. To understand why, you must first understand how thyristor dimmers work.
Figure 2 Front edge thyristor dimmer
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