Controls for adjusting the level of artificial lighting are commonplace, ranging from the simple household dimmer switch to extensive lighting circuits used in stage productions. These lighting controls play a significant role in the ambiance of a room.
Early lighting controls relied on variable resistors to dissipate power, thereby “dimming” the lights. Although functional, these early lighting controls wasted power and generated significant heat. Modern lighting controls use triacs. Triacs function by varying the point that a load is turned on during each alternating current (AC) cycle (in the United States, AC current has 60 cycles per second). That is, triacs vary the time at which the load is switched on after zero-cross during each AC cycle. This rapid “switching” serves to reduce the total current being delivered to the lights. But this rapid switching can also cause a “buzzing” sound in the light, as well as electromagnetic interference. Accordingly, most triacs include circuits with an inductor choke and an interference capacitor.
While simple lighting controls, such as the household dimmer switch, may be suitable for controlling a few lights, other lighting circuits may require different current-capacity triacs. By way of example, a banquet hall may require one or more higher current capacity triacs than the reception area of an office. In addition, a single room may have multiple light circuits requiring different current capacity triacs. For example, a higher-current capacity triac may be provided for the main lighting circuit in a room, and another, smaller capacity triac may be provided for a perimeter lighting circuit (e.g., to illuminate artwork hanging on the walls) in the same room.
Although triacs produce less heat than the early variable resistor dimmer switches, triacs still produce heat. Logically, triacs carrying higher current produce even more heat that needs to be dissipated. Accordingly, triacs carrying higher current are provided with larger heat sinks (e.g., having fins), or even fans to dissipate the heat that is generated by the triac. However, large heat sinks and fans are not aesthetically pleasing and fans can be noisy, typically requiring that these triacs be installed in utility closets or the like.
Manufacturing different current capacity triacs is also expensive. Not only is the related circuitry (e.g., inductor chokes and interference capacitors) more expensive for higher current capacity triacs, but the manufacturer must also maintain a large inventory of different size parts for manufacturing each of the different current capacity triacs. These direct costs are passed onto the installer, who incurs further overhead by having to maintain an inventory of different current capacity triacs. Eventually, these costs are passed onto the consumer.