1. Field
The present disclosure generally relates to a light-emitting diode (LED) driver circuit for use with LED bulbs, and more particularly, to and LED driver circuit with an improved power factor.
2. Description of Related Art
Despite the many benefits of LED bulbs, there are some challenges that have prevented LED bulbs from widely replacing incandescent and fluorescent bulbs in residential application. For example, electrically, LED bulbs operate differently than incandescent and fluorescent bulbs. LED bulbs are current controlled devices, meaning that the light output is control by changes in current as opposed to incandescent and fluorescent bulbs that are voltage controlled.
The difference in control requires that LED bulbs have special driver circuits that convert the standard AC voltage supplied in residential outlets to a current suitable for driving LEDs. These driver circuits, however, typically result in an LED bulb that interacts with the electrical grid very differently than incandescent bulbs.
Power factor is one significant parameter where LED bulbs differ from incandescent bulbs. Power factor is the ratio of real power flowing to a load to the apparent power. A load with a power factor of 1 means that the load is using all power being delivered to the load. Typically, purely resistive loads have a power factor of 1. A power factor of less than 1 indicates that there is energy storage in the load that may return power to the power supply out of phase with the power supply. The lower the power factor, the more wasted power.
LED bulb driver circuits typically have storage elements (e.g., capacitors) that may cause a lower power factor for the LED bulb as compared to an incandescent bulb. This results in an LED bulb that may put more strain on the power supply (i.e., the electrical grid) than is necessary.
LED bulb driver circuits may be modified with additional components or special circuits to improve the power factor. However, these modifications increase the volume occupied by the driver circuit. In space limited LED bulbs, it may be difficult to fit these additional components or special circuits. Additionally, the modifications may also make it more difficult for the LED bulb to work with common residential light dimmers.