Driver of an LED array

Patent metadata

Field	Value
Publication number	US-11051382-B2
Application number	US-201816762634-A
Country	US
Kind code	B2
Filing date	Oct 31, 2018
Priority date	Nov 10, 2017
Publication date	Jun 29, 2021
Grant date	Jun 29, 2021

Abstract

The invention describes a driver (1) of an array (2) of current-driven LEDs (20), comprising a voltage converter (10) arranged to generate a supply voltage (Vboost) to the LED array (2) and to adjust the supply voltage (Vboost) in response to a feedback signal (100); a number of current sources (CS1, . . . , CSn) arranged to drive the LEDs (20) of the LED array (2); and a monitoring arrangement (M) adapted to monitor a current source voltage (Vcs1, . . . , Vcsn) relative to a voltage headroom (H) and to generate the feedback signal (100) on the basis of the headroom monitoring results. The invention further describes a device (4) comprising an LED array (2) and an embodiment of the inventive driver (1). The invention further describes method of driving an LED array (2).

First claim

The invention claimed is:

1. A driver of an array of current-driven light emitting diodes (LEDs), comprising:
a voltage converter arranged to generate a supply voltage to the LED array and to adjust the supply voltage in response to a feedback signal;
a plurality of current regulators arranged to drive the LEDs of the LED array, wherein the cathode of each LED is connected to a current regulator; and
a monitoring arrangement adapted to monitor a current regulator voltage relative to a voltage headroom and to generate the feedback signal on the basis of headroom monitoring results, the monitoring arrangement comprising a plurality of window comparators, and wherein the cathode of each current-driven LED is also connected to an input of a window comparator, and wherein the window comparator is realized to generate a high comparator output when the LED cathode voltage is lower than a first input voltage defining a lower bound of the voltage headroom and to generate a low comparator output when that LED cathode voltage is higher than a second input voltage defining an upper bound of the voltage headroom, and wherein the feedback signal comprises bundled comparator outputs.

2. The driver according to claim 1 , wherein the current regulator comprises a controlled active device.

3. The driver according to claim 2 , wherein the current regulator comprises a bipolar transistor or a MOSFET.

4. The driver according to claim 1 , wherein the window comparator comprises:
a first operational amplifier and a first diode connected in forward direction between the output of the first operational amplifier and the comparator output; and
a second operational amplifier and a second diode connected in reverse direction between the output of the second operational amplifier and the comparator output.

5. The driver according to claim 4 , wherein
inverting inputs of the operational amplifiers are connected to an electrode of an LED;
a non-inverting input of the first operational amplifier is connected to the first input voltage; and
a non-inverting input of the second operational amplifier is connected to the second input voltage.

6. The driver according to claim 5 , wherein the window comparator comprises a resistor between the cathode of the first diode and the anode of the second diode so that a single comparator with a high output level on its first operational amplifier is adapted to push the feedback signal above a threshold level.

7. The driver according to claim 1 , wherein an electrode of each LED is connected to a dedicated current regulator.

8. A device comprising:
the LED array comprising a plurality of current-driven LEDs; and
the driver according to claim 1 , arranged to drive the LEDs.

9. The device according to claim 8 , wherein the LED array is realized as a segmented flash comprising at least nine LEDs.

10. The device according to claim 8 , in the form of a mobile phone.

11. The device according to claim 8 , wherein the voltage converter is realized as any of a boost converter, a buck converter, or a buck-boost converter.

12. The device according to claim 8 , comprising the plurality of current regulators, each configured to control the current through an LED of the LED array, and wherein an electrode of each LED is connected to a current regulator.

13. A method of driving the array of current-driven LEDs using the driver according to claim 1 , which method comprises:
increasing the supply voltage (V boost ) of the voltage converter when the feedback signal from the monitoring arrangement (M) is higher than a threshold level (V 20 ); and
decreasing the supply voltage (V boost ) of the voltage converter ( 10 ) when the feedback signal from the monitoring arrangement (M) is lower than a threshold level (V 20 ).

Assignees

• Lumileds Llc

Inventors

• Derks Henk

Classifications

• H05B45/3725

  Switched mode power supply [SMPS] · CPC title

• H05B45/46 Primary

  having LEDs disposed in parallel lines · CPC title

• H02M3/156

  with automatic control of output voltage or current, e.g. switching regulators · CPC title

• H05B45/38

  using boost topology · CPC title

• H05B45/375 Primary

  using buck topology · CPC title