CURRENT SPLIT CIRCUIT FOR EQUALLY SPLITTING CURRENT BETWEEN PARALLEL CONNECTED LED LUMINAIRE STRINGS

• US 20140252966A1
• Filed: 03/06/2013
• Published: 09/11/2014
• Est. Priority Date: 03/06/2013
• Status: Active Grant

• Current Assignee: Current Lighting Solutions, LLC (f/k/a GE Lighting Solutions, LLC) (American Industrial Partners)
• Original Assignee: General Electric Company
• Inventors: Balazs, Jeno, Szallasi, Szabolcs
• Granted Patent: US 9,119,258 B2
• Time in Patent Office: Days
• US Class Current: 315/186
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: H05B 45/35 Balancing circuits
• CPC Class Codes: H05B 45/397 Current mirror circuits
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

A system and method for equally splitting the current supplied to parallel connected strings of LEDs. The system and method includes a current splitting circuit such as a mirror circuit that divides the current substantially equally between two or more parallel connected strings of LEDs. The current splitting circuit ensures that illumination levels of the strings of LEDs are uniform without requiring the strings of LEDs to be binned. The current splitting circuit also allows the strings of LEDs to be dimmed in both pulse width modulation (PWM) and continuous modes.

Claims

1. A lighting circuit, comprising:

a first string of solid state lighting devices in communication with a power source, the first string of solid state lighting devices being connected in series with each other;

a second string of solid state light devices in communication with the power source, the second string of solid state light devices being connected in series with each other, the first and second string of solid state lighting devices being connected in parallel; and

a current split circuit in communication with the first and string of solid state lighting devices.

2. The lighting circuit according to claim 1, wherein the current split circuit includes:

a first transistor connected in series with the first string of solid state lighting devices; and

,

a second transistor in communication with the first transistor and connected in series with the second string of solid state lighting devices,

wherein the current split circuit are configured to divide a current substantially equally between the first string of solid state lighting devices and the second string of solid state lighting devices.

3. The lighting circuit according to claim 2, further comprising:

a third string of solid state lighting devices in communication with the power source, the third string of solid state lighting devices being connected in series; and

a fourth string of solid state lighting devices in communication with the power source, the fourth string of solid state lighting devices being connected in series; and

the current split circuit further comprising;

a third transistor in communication with the second transistor and connected in series with the third string of solid state lighting devices; and

,

a fourth transistor in communication with the third transistor and connected in series with the third string of solid state lighting devices, the current split circuit being configured to divide the current substantially equally between the third string of solid state lighting devices and the fourth string of solid state lighting devices.

4. The lighting circuit according to claim 3, wherein the current is divided substantially equally between the first string of solid state lighting devices, the second string of solid state lighting devices, the third string of solid state lighting devices, and the fourth string of solid state lighting devices.

5. The lighting circuit according to claim 1, wherein the power source is a constant voltage generator.

6. The lighting circuit according to claim 1, wherein the power source is a constant current generator.

7. The lighting circuit according to claim 1, wherein the first string of solid state lighting devices and the second string of solid state lighting devices each include multiple solid state lights.

8. The lighting circuit according to claim 1, wherein the solid state lighting devices are light emitting diodes.

9. The lighting circuit according to claim 2, wherein the first transistor and the second transistor form a mirror circuit that controls the illumination levels of the first string of solid state lighting devices and the second string of solid state lighting devices to be substantially uniform.

10. The lighting circuit according to claim 2, wherein the solid state lighting devices are unbinned.

11. The lighting circuit according to claim 1, wherein the first string of solid state lighting devices and the second string of solid state lighting devices are dimmable in at least one of a pulse width modulation mode and a continuous mode.

12. A lighting circuit, comprising:

a plurality of strings of light emitting diodes connected to a power source, the plurality of strings of light emitting diodes being connected in parallel with each other; and

a current split circuit connected to the plurality of strings of light emitting diodes, the current split circuit comprising a plurality of transistors, including;

a reference transistor connected in series with a first of the plurality of strings of light emitting diodes, and

one or more copy transistors connected to the reference transistor and in series with one of the plurality of strings of light emitting diodes, wherein the one or more copy transistors divides the current substantially equally between the plurality of strings of light emitting diodes.

13. The lighting circuit according to claim 12, wherein each of the plurality of strings of light emitting diodes includes multiple light emitting diodes.

14. The lighting circuit according to claim 12, wherein the power source is a constant voltage generator.

15. The lighting circuit according to claim 12, wherein the power source is a constant current generator.

16. The lighting circuit according to claim 12, wherein the current split circuit controls the illumination levels of the plurality of strings of light emitting diodes to be substantially uniform.

17. A lighting method, comprising:

providing a power source;

providing a plurality of strings of light emitting diodes in communication with the power source, the plurality of strings of light emitting diodes being connected in parallel with each other;

providing a current split circuit in communication with the plurality of strings of light emitting diodes, the current split circuit having a plurality of transistors that form a mirror circuit; and

dividing the current equally between each of the plurality of strings of light emitting diodes such that the light emitting diodes are illuminated at substantially the same level.

18. The lighting method according to claim 17, further comprising dimming the plurality of strings of light emitting diodes.

19. The lighting method according to claim 18, wherein the plurality of strings of light emitting diodes are dimmable in pulse width modulation mode.

20. The lighting method according to claim 18, wherein the plurality of strings of light emitting diodes are dimmable in continuous mode.