Method and apparatus for controlling light emitting diodes

• US 20040164685A1
• Filed: 02/20/2003
• Published: 08/26/2004
• Est. Priority Date: 02/20/2003
• Status: Active Grant

• Current Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Original Assignee: Visteon Global Technologies Incorporated (Visteon Corporation)
• Inventors: Dygert, Gregory J.
• Granted Patent: US 6,864,641 B2
• Time in Patent Office: Days
• US Class Current: 315/224
• CPC Class Codes: H05B 45/38 using boost topology
• 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 light emitting diode (“LED”) circuit includes a plurality of light emitting diodes connected in a hybrid parallel-series configuration, and a current regulating circuit that includes a current regulating element connected to a first chain of the plurality of chains of LEDS, and a plurality of current mirroring elements, each current mirroring element being connected to a respective chain of the plurality of chains of LEDs.

Claims

1. A light emitting diode (“

LED”

) circuit, comprising;

a plurality of chains of LEDs connected in parallel, each chain of LEDs including a plurality of LEDs connected in series; and

a current regulating circuit including a current regulating element connected to a first chain of the plurality of chains of LEDS, and a plurality of current mirroring elements, each current mirroring element being connected to a respective chain of the plurality of chains of LEDs.

2. The LED circuit of claim 1, wherein the current regulating circuit maintains a uniform current in the plurality of chains of LEDs as a direct function of the level and duty ratio of a control signal supplied to the current regulating circuit.

3. The LED circuit of claim 2, wherein the control signal is a pulse width modulated (“

PWM”

) signal.

4. The LED circuit of claim 1, further comprising a monitoring/regulating circuit connected to the plurality of chains of LEDs and the current regulating circuit, the monitoring/regulating circuit monitoring the voltage drop across the current regulating and mirroring (“

CRM”

) elements, or across the chains of LEDs, and adjusting a supply voltage to the plurality of chains of LEDs based on the monitored voltage drops.

5. The LED circuit of claim 4, wherein the monitoring/regulating circuit includes a boost regulator and a boost converter, the boost regulator monitoring the voltage drop across the CRM elements, or across the chains of LEDs, and providing a feedback signal to the converter, the converter adjusting the supply voltage to the plurality of chains of LEDs in response to the feedback signal.