Method and system for driving organic LED's

• US 8,928,240 B2
• Filed: 08/16/2011
• Issued: 01/06/2015
• Est. Priority Date: 08/16/2011
• Status: Expired due to Fees

• Current Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Original Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Inventors: Raj, Rashmi K.
• Primary Examiner(s): A, Minh D
• Application Number:
  US13/210,735
• Publication Number:
  US 20130043803A1
• Time in Patent Office: 1,239 Days
• Field of Search: 315/127, 315/241.R, 315/245, 315/246, 315/291, 315/307
• US Class Current: 315/241.R
• CPC Class Codes: H05B 45/60 Circuit arrangements for operating LEDs comprising organic material, e.g. for operating organic light-emitting diodes [OLED] or polymer light-emitting diodes [PLED]
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A method and system for driving an organic light emitting diode (OLED) with a regular LED driver without pre-charge are provided. In the examples, at least one passive element is included in parallel with the OLED across the output of the power supply. This passive element may be a capacitor. In one example, the effective series resistance (ESR) of the parallel capacitor may be substantially less than an ESR of the OLED at turn-on of the OLED. The turn-on delay of the OLED substantially is determined by the ESR of the parallel capacitor and is not substantially determined by the ESR of the OLED. In another example, the ESR of the parallel capacitor is less than or equal to 10% of an ESR of the OLED at turn-on of the OLED.

Claims

1. A light emitting apparatus, comprising:

an organic light emitting diode (OLED);

a power supply configured to drive the OLED without pre-charge, the OLED being connected across an output of the power supply;

a first capacitor connected in parallel with the OLED across the output of the power supply,

wherein an equivalent series resistance (ESR) of the first parallel capacitor is less than or equal to 10% of an ESR of the OLED at turn-on of the OLED; and

a second capacitor connected in parallel with the OLED,

wherein the first parallel capacitor has an ESR substantially lower than the second parallel capacitor, wherein the first parallel capacitor is a ceramic capacitor.

2. The light emitting apparatus of claim 1, wherein the power supply comprises a switch-mode driver.

3. The light emitting apparatus of claim 2, wherein the power supply further comprises a feedback circuit for stabilization.

4. The light emitting apparatus of claim 2, wherein the OLED is dimmable through pulse width modulation (PWM).

5. A light emitting apparatus, comprising

an organic light emitting diode (OLED);

a power supply configured to drive the OLED without pre-charge, the OLED being connected across an output of the power supply;

a first capacitor connected in parallel with the OLED across the output of the power supply; and

a second capacitor connected in parallel with the OLED, wherein;

an equivalent series resistance (ESR) of the first parallel capacitor is substantially less than an ESR of the OLED at turn-on of the OLED,

the first parallel capacitor has an ESR substantially lower than the second parallel capacitor, and

turn-on delay of the OLED is substantially determined by the ESR of the first parallel capacitor, and not substantially determined by the ESR of the OLED, wherein the first parallel capacitor is a ceramic capacitor.

6. The light emitting apparatus of claim 5, wherein the ESR of the first parallel capacitor is less than or equal to 10% of an ESR of the OLED at turn-on of the OLED.

7. The light emitting apparatus of claim 5, wherein the ESR of the first parallel capacitor is such that the delay in turn-ON of the OLED is less than or equal to 0.1 seconds.

8. The light emitting apparatus of claim 5, wherein the ESR of the first parallel capacitor is such that the delay in turn-ON of the OLED is less than or equal to 1 μ

s.

9. The light emitting apparatus of claim 5, wherein the power supply comprises a switch-mode driver.

10. The light emitting apparatus of claim 9, wherein the power supply further comprises a feedback circuit for stabilization.

11. A method of driving an organic light emitting diode (OLED), the method comprising:

applying power to the OLED without pre-charge; and

reducing a resistance of the OLED by providing a first capacitor in parallel with the OLED with an equivalent series resistance (ESR) that is less than or equal to 10% of an ESR of the OLED at turn-on of the OLED, wherein;

there is a second capacitor connected in parallel with the OLED, and

the first parallel capacitor has an ESR substantially lower than the second parallel capacitor, wherein the first parallel capacitor is a ceramic capacitor.

12. The method of claim 11, further comprising dimming the OLED through pulse width modulation (PWM).

13. A method of driving an organic light emitting diode (OLED), the method comprising:

applying power to the OLED without pre-charge; and

reducing a resistance of the OLED by providing a first capacitor in parallel with the OLED with an equivalent series resistance (ESR) of the parallel capacitor is substantially less than an ESR of the OLED at turn-on of the OLED, wherein;

there is a second capacitor connected in parallel with the OLED, and

the first parallel capacitor has an ESR substantially lower than the second parallel capacitor, and

turn-on delay of the OLED when power is applied to the OLED is determined substantially by the ESR of the first parallel capacitor, and not by the ESR of the OLED, wherein the first parallel capacitor is a ceramic capacitor.

14. The method of claim 13, wherein the ESR of the first parallel capacitor is less than or equal to 10% of an ESR of the OLED at turn-on of the OLED.

15. The method of claim 13, further comprising delaying turn-ON of the OLED by less than or equal to 0.1 seconds by the ESR of the first parallel capacitor.

16. The method of claim 13, further comprising delaying turn-ON of the OLED by less than or equal to 1 μ

s by the first parallel capacitor.

17. The method of claim 13, further comprising dimming the OLED through pulse width modulation (PWM).