LIGHT-EMITTING DIODE NETWORK

• US 20120306392A1
• Filed: 10/14/2011
• Published: 12/06/2012
• Est. Priority Date: 06/02/2011
• Status: Abandoned Application

• Current Assignee: Epistar Corporation
• Original Assignee: Taiwan Semiconductor Manufacturing Company Limited
• Inventors: YOUNG, Whu-Ming, CHIU, Ko-Chih, TARN, Jacob C.
• Application Number:
  US13/273,785
• Publication Number:
  US 20120306392A1
• Time in Patent Office: Days
• US Class Current: 315/192
• 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: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

LED devices or circuits include a number of serially connected LED segments, which may additionally include parallel branches, which are switched on or off depending on an input voltage to the LED segments. As the input voltage varies, none, different portions, or all of the LEDs are lit. The input voltage to the LED segments may be an output voltage from a bridge rectifier in response to an alternate current (AC) power. The LED devices or circuits include no inductors, transformers and electrolytic capacitors.

Claims

1. A light emitting diode (LED) apparatus comprising:

a plurality of LED segments, wherein each of the plurality of LED segments comprises one or more LED branches, wherein each LED branch comprising a plurality of LED dies connected in series, wherein LED branches within a LED segment are connected in parallel;

switches configured to couple the plurality of LED segments; and

,

a controller configured to operate the switches and to control a stepping current based on a input voltage to the plurality of LED segments,

wherein the LED device includes no transformers, inductors, or capacitors.

2. The LED device of claim 1, wherein the plurality of LED segments is three or more segments and the first LED segment comprises more LED branches than the second LED segment.

3. The LED device of claim 1, wherein the controller is configured to perform an operation comprising:

driving a first current through a first LED segment when an input voltage reaches a first voltage;

driving a second current larger than or equal to the first current though the first LED segment and a second LED segment when the input voltage reaches a second voltage larger than the first voltage; and

,

driving no current through the plurality of LED segments when the input voltage is less than the first voltage.

4. The LED device of claim 3, wherein the first voltage is a forward voltage for the first LED segment at the first current.

5. The LED device of claim 1, wherein the LED dies in each LED segment have different areas.

6. The LED device of claim 1, wherein a maximum current density with all LED segments switched on is above a rated current density for the LED dies.

7. The LED device of claim 1, wherein a power efficiency ratio of the LED device is about 90% or greater.

8. An LED circuit comprising:

a bridge rectifier;

a plurality of LED segments, wherein each of the plurality of LED segments comprises a plurality of LED junctions and each of the plurality of LED segments are on one die module;

switches configured to couple the plurality of LED segments; and

,

a controller configured to operate the switches based on a varying output voltage from the bridge rectifier,

wherein a forward voltage for a total number of LED junctions for all LED segments is less than a maximum output voltage from the bridge rectifier, and

wherein the LED device includes no transformers, inductors, or capacitors.

9. The LED circuit of claim 8, wherein the plurality of LED segments are on one die.

10. The LED circuit of claim 8, wherein each of the plurality of LED segments comprises one or more LED branches connected in parallel.

11. The LED circuit of claim 8, wherein the plurality of LED segments is three or more segments.

12. The LED circuit of claim 8, wherein the controller is configured to

switch on a first LED segment when the output voltage from the bridge rectifier reaches a first voltage, wherein the first voltage is a forward voltage for the first LED segment;

switch on a second LED segment in addition to the first LED segment when the output voltage from the bridge rectifier reaches a second voltage, wherein the second voltage is a forward voltage for the first and second LED segment; and

,

switch off all LED segments when the output voltage from the bridge rectifier is less than the first voltage.

13. The LED circuit of claim 12, wherein the controller is further configured to drive a constant current through the plurality of LED segments.

14. The LED circuit of claim 8, wherein a power efficiency ratio of the LED circuit is about 90% or greater.

15. A method comprising:

receiving a varying input voltage;

switching on a first LED segment and driving the first LED segment at a first current density when the input voltage increases to a first voltage, wherein the first voltage is a forward voltage of the first LED segment at the first current density;

switching on a second LED segment and driving the first and second LED segments at a second current density when the input voltage increases to a second voltage, wherein the second voltage is a forward voltage of the first and second LED segments at the second current density;

switching on a third LED segment and driving the first, second, and third LED segments at a third current density when the input voltage increases to a third voltage, wherein the third voltage is a forward voltage of the first, second, and third LED segments at the third current density; and

,

switching off all LED segments when the input voltage is less than the first voltage.

16. The method of claim 15, further comprising

switching off the third LED segment when the input voltage decreases to the third voltage and driving the first and second LED segment at the second current density;

and,

switching off the second LED segment when the input voltage decreases to the second voltage and driving the first LED segment at the first current density.

17. The method of claim 15, wherein the first current density is about the rated current density for the first LED segment.

18. The method of claim 15, wherein the third voltage is more than about 70% of a maximum input voltage.

19. The method of claim 15, further comprising:

switching on a fourth LED segment and driving the first, second, third, and fourth LED segments at a fourth current density when the input voltage increases to a fourth voltage, wherein the fourth voltage is a forward voltage of the first, second, third, and fourth LED segments at the fourth current density.

20. The method of claim 19, wherein the fourth current density is about or less than a maximum current density.