1. Field of the Invention
The aspects of the present disclosure relate generally to LED light sources, and in particular to an LED light source compatible with different phase control dimmers.
2. Description of Related Art
Most dimmers used in lighting applications, such as home lighting, commercial lighting, and traffic signaling, are designed for use on locally available AC grid voltage. These dimmers operate with higher power consumption lamps that generally present as resistive loads to their controllers. Recent advancements in lamp technology have led to development of Light Emitting Diode (LED) lamps with improved efficiency and significantly lower power consumption. These LED lamps typically require DC power and often consume less than ten watts. Thus these lamps are not directly compatible with existing lighting fixtures and dimmers.
Nearly all lamp dimmers designed for use with a local AC power grid include a triac device to reduce lamp power. A triac is a bidirectional thyristor device for alternating current which may be viewed as a switch that can conduct current in either direction. When these dimmers are used to drive LED lamp assemblies, flickering can occur due to the switching and high current peaks resulting from triac switching current fluctuations caused by interaction with an EMI input filter. This flickering can have detrimental effects on the triac device. Further, a typical LED lamp is not compatible with all types of phase controlled dimmers. The lack of universal compatibility will prevent or drastically reduce the introduction of LED lamps into the marketplace as replacements or retrofits for standard incandescent lamps.
Increasing the power consumption of LED lamps is one approach that has been used to adapt LED lamps to various LED lamp dimmers. However, increasing the power consumption can create thermal issues in the LED lamp and the associated circuitry and offsets many of the benefits that drive the move to low power LED lamps. For example, the increased temperatures can reduce the usable life of the LED lamp, and increased power consumption reduces cost benefits.
Other approaches for adapting LED lamps to various dimmers have included the use of digital integrated circuit solutions that detect a firing angle of the dimmers or triacs. However, LED lamps do not always present as a resistive load leading to inaccurate detection of firing angle. Although the use of specific drivers, specific integrated circuits or more expensive digital integrated circuits may provide certain solutions, these solutions are typically directed to specific LED lamps and will work with only a few, specific dimmers. It would be advantageous to be able to utilize LED lamps in a wide range of existing and new applications and with existing and new dimmers without concern for compatibility issues. It would also be advantageous to maintain the power factor of a LED lamp circuit near unity, when a LED lamp is directly connected to the local mains supply without a dimmer.
Accordingly, it would be desirable to provide LED lamps that solve at least some of the problems identified above.