Patent number 8552656 is assigned to
The following quote was obtained by the news editors from the background information supplied by the inventors: "The present disclosure relates to alternating current (AC) light emitting devices and, more particularly, to an AC light emitting device operated by an AC voltage source, a driving device thereof, and a driving method thereby.
"A highly integrated light emitting diode (LED) chip or package includes a plurality of LED cells connected to each other and generally undergoes an increase of a threshold voltage in proportion to the number of LED cells connected to each other in a forward direction when used with an AC voltage source.
"FIGS. 1 and 2 are circuit diagrams explaining problems of a conventional AC LED.
"FIG. 1 is an equivalent circuit diagram where an AC LED 10, an AC voltage source V.sub.ac, and a resistor R.sub.1 are connected in series to one another. In the AC LED 10, an LED cell 12 is operated in a positive half-period of the AC voltage source V.sub.ac and an LED cell 14 is operated in a negative half-period of the AC voltage source V.sub.ac. The current across the AC LED 10 is dependent on the resistor R.sub.1.
"FIG. 2 is a graph depicting a voltage-current waveform of the AC LED shown in FIG. 1, in which g.sub.1 is a voltage curve of the AC voltage source V.sub.ac and g.sub.2 is a current curve of the current across the AC LED 10 in FIG. 1. The x-axis indicates time and the y-axis indicates voltage or current.
"Referring to FIGS. 1 and 2, in the positive half-period of the AC voltage source V.sub.ac, a current is allowed to flow and the LED cell 12 emits light when the voltage is greater than or equal to the forward threshold voltage of the LED cell 12. Similarly, in the negative half-period of the AC voltage source V.sub.ac, a current is allowed to flow and the LED cell 14 emits light when the voltage is greater than or equal to the forward threshold voltage of the LED cell 14.
"Such characteristics of the AC LED 10 operated only by application of the voltage greater than or equal to the forward threshold voltage cause several problems. In other words, when the applied voltage is greater than or equal to the forward threshold voltage of the LED cell 12 or 14 connected in the forward direction with respect to the applied voltage, an avalanche current flows through the AC LED 10 and a short operating region is provided to the AC LED 10 for a single period of the AC voltage source applied thereto, thereby causing a low power factor, an increase in total harmonic distortion (THD) (particularly, third-order harmonic distortion), excessive flickering, and deterioration in optical efficiency."
In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors' summary information for this patent: "An aspect of the present disclosure is to provide an AC light emitting device, a driving device thereof, and a driving method thereby, which solve problems such as low power factor, increase in total harmonic distortion, flickering, and deterioration in optical efficiency due to the operating characteristics of the AC LED during application of an AC voltage source.
Most Popular Stories
- NSA Defends Global Cellphone Tracking Legality
- Ad Counts Rise in 2013 for Hispanic Magazines
- Top Websites for U.S. Hispanics
- Networks Vie for U.S. Hispanic TV Viewers
- Saab Gets Back into the Game; U.S. Auto Sales Soar
- Apple Activates Customer-Tracking iBeacon
- Dell Offers Undisclosed Number of Employee Buyouts
- 2013 Tech Gift Guide: iPad Mini Still Hot; Chromecast a Great Low-Cost Option
- Authorities Close to Deal with JPMorgan Chase over Madoff Response
- A Biography of Jonathan Ive, Apple's Creative Chief