Geschichte der TRIAC-Dimmung

Silicon controlled rectifier (SCR) is a high-power electrical component, also known as thyristor. It has the advantages of small volume, high efficiency and long service life. In the automatic control system, it can be used as a high-power driver to control high-power equipment with low-power controls.

In 1959 Joel Spira invented the SCR (silicon controlled rectifier) controlled dimmer and a year later Eugene Alessio announced a TRIAC (Triode for AC) controlled dimmer. These thyristor-based controls are the mainstay of dimmer technology today, although the IGBT (Insulated Gate Bipolar Transistor) is used in some of the newest dimmer designs because it is an easier device to drive and control.

All of these devices work by cutting off part of each half cycle of the AC line waveform. The amount that’s cut off is measured by the phase angle. A complete sine wave is 360 degrees in length; a half wave is 180 degrees. If the dimmer cuts off 90 degrees of each half cycle, the effective voltage applied to the lamp is reduced by half because only one half of the waveform or 180 degrees remains. Phase-cut dimmers can operate on the leading edge (forward phase-cut) or trailing edge (reverse phase-cut) of the waveform. Forward phase-cut developed naturally from the thyristor behavior. The SCR or TRIAC is triggered to turn it on and it turns off when the waveform crosses zero voltage. Reverse phase-cut dimming was developed to improve performance of low voltage halogen lamps operating on an electronic transformer, a type of switch mode power supply.

This technology has dominated the market for decades and there’s a huge installed base of these dimmers. For more than a century, the lighting industry has been relying on incandescent bulbs, and phase dimmer has become the main dimming control means in the past 50 years. Standard forward phase dimmer, also known as triac dimmer, is well known that it is difficult to connect directly with LED driver. To make matters worse, the performance of each dimmer varies greatly. Although newer and better reverse phase dimmers are available, standard positive phase dimmers still dominate the global power infrastructure, and LED lighting manufacturers can't simply avoid it.

TRIAC dimming comes along with the benefit of high efficiency, high adjustment accuracy, and lightweight, small compact size, and easy remote control. In the market, TRIAC dimming is dominating the form of dimmer and many products are designed with this kind of dimmer. The huge benefit of TRIAC dimmer is that when you use it with LED light, it has a low dimming cost.