Light emitting device for AC power operation

• US 8,716,946 B2
• Filed: 10/20/2010
• Issued: 05/06/2014
• Est. Priority Date: 06/28/2005
• Status: Active Grant

• Current Assignee: Seoul Viosys Co., Ltd. (Seoul Semiconductor Co., Ltd.)
• Original Assignee: Seoul Optodevice Company Limited (Seoul Semiconductor Co., Ltd.)
• Inventors: Lee, Chung Hoon, Speck, James S., Kim, Hong San, Kim, Jae Jo, Kim, Sung Han, Lee, Jae Ho
• Primary Examiner(s): Owens, Douglas W
• Assistant Examiner(s): Chen, Jianzi
• Application Number:
  US12/908,692
• Publication Number:
  US 20110031891A1
• Time in Patent Office: 1,294 Days
• Field of Search: 315/185.R, 315/186, 315/192, 315/193, 315/185.S, 315/200.R, 315/201, 315/203, 315/200.A, 315/209.R, 315/210, 315/226, 315/294, 315/295, 315/312, 315/313, 315/317, 315/320, 315/323, 315/360, 315/362, 362/217, 362/219, 362/221, 362/222, 362/223, 362/227, 362/249, 362/251, 362/252, 362/362, 362/363, 362/375, 362/800, 362/806, 362/812
• US Class Current: 315/209.R
• CPC Class Codes: H01L 2224/48137 the bodies being arranged next to each other, e.g. on a common substrate
• CPC Class Codes: H01L 2224/49107 on the semiconductor or solid-state body
• CPC Class Codes: H01L 2224/73265 Layer and wire connectors
• CPC Class Codes: H01L 27/153 in a repetitive configuration, e.g. LED bars
• CPC Class Codes: H01L 27/156 two-dimensional arrays
• CPC Class Codes: H05B 33/02 Details
• CPC Class Codes: H05B 45/14 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/40 Details of LED load circuits
• CPC Class Codes: H05B 45/42 Antiparallel configurations
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices
• CPC Class Codes: H05B 47/155 Coordinated control of two or more light sources

Abstract

Disclosed is an improved light-emitting device for an AC power operation. A conventional light emitting device employs an AC light-emitting diode having arrays of light emitting cells connected in reverse parallel. The arrays in the prior art alternately repeat on/off in response to a phase change of an AC power source, resulting in short light emission time during a ½ cycle and the occurrence of a flicker effect. An AC light-emitting device according to the present invention employs a variety of means by which light emission time is prolonged during a ½ cycle in response to a phase change of an AC power source and a flicker effect can be reduced. For example, the means may be switching blocks respectively connected to nodes between the light emitting cells, switching blocks connected to a plurality of arrays, or a delay phosphor. Further, there is provided an AC light-emitting device, wherein a plurality of arrays having the different numbers of light emitting cells are employed to increase light emission time and to reduce a flicker effect.

Claims

1. A light emitting device, comprising:

a light emitting cell array configured to receive an input voltage and comprising a plurality of light emitting cells connected in series on a substrate,

the plurality of light emitting cells to emit light in response to the input voltage, the input voltage to periodically change during a period and to have a first voltage value, which does not turn on the plurality of light emitting cells, after a first peak value,

wherein the light emitting device emits light comprising a periodically changing luminous intensity in response to the input voltage, the periodically changing luminous intensity of the light emitting device has a second peak value and a minimum value, the minimum value of the periodically changing luminous intensity is greater than zero when the input voltage has the first voltage value, and

wherein each light emitting cell comprises an inclined side surface.

2. The light emitting device of claim 1, further comprising a switching device configured to control the number of light emitting cells that emit light in response to the input voltage.

3. The light emitting device of claim 1, further comprising a bridge rectifier connected to the light emitting cell array and configured to receive the input voltage.

4. The light emitting device of claim 1, wherein the light emitting device comprises a plurality of light emitting cell arrays.

5. The light emitting device of claim 1, wherein the plurality of light emitting cell arrays each comprise a different number of light emitting cells from one another.

6. The light emitting device of claim 1, wherein each light emitting cell comprises a roughened surface on a top surface thereof.

7. The light emitting device of claim 6, wherein the top surface of the light emitting cell comprising the roughened surface comprises an n-type semiconductor.

8. A light emitting device, comprising:

a light emitting part to emit light in response to an input voltage, the input voltage to periodically change during a period and to have a first voltage value, which does not turn on the light emitting part, after a first peak value; and

at least one phosphor to absorb the light emitted from the light emitting part and to emit light comprising a different wavelength than the absorbed light,

wherein the light emitting part comprises a first light emitting part that emits light at a first range of the input voltage, and a second light emitting part that emits light at a second range of the input voltage, the second range of the input voltage being mutually exclusive of the first range of the input voltage.

9. The light emitting device of claim 8, wherein the first light emitting part and the second light emitting part each comprise different numbers of light emitting cells.

10. The light emitting device of claim 8, wherein the at least one phosphor comprises a delay phosphor to delay light conversion.