LED driver dimming

Patent metadata

Field	Value
Publication number	US-11013077-B2
Application number	US-201716091187-A
Country	US
Kind code	B2
Filing date	Apr 21, 2017
Priority date	Apr 22, 2016
Publication date	May 18, 2021
Grant date	May 18, 2021

Abstract

An LED driver has outputs to drive LEDs in groups of different colour temperatures. An input is configured to receive setpoint information, and a control device is configured to determine a combined LED setpoint intensity for the groups and a combined LED setpoint colour temperature for the groups, from the LED setpoint information. If the LED setpoint intensity is above a threshold, the control device operates the LED driver outputs to mix the LED group outputs to jointly achieve the LED setpoint intensity and the LED setpoint colour temperature. If the LED setpoint intensity is below the threshold, the control device selects a single LED group, operates the LED driver output associated with the selected LED group to drive that one LED group at the LED setpoint intensity, and operates the remaining LED driver outputs to drive the remaining LED groups at zero LED intensity.

First claim

The invention claimed is:

1. An LED driver configured to drive a plurality of LEDs, the LEDs being arranged in groups having respective different colour temperatures, the LED driver comprising respective LED driver outputs, each LED driver output being connected to a respective one of the LED groups for driving that LED group,
wherein the LED driver comprises a setpoint input configured to receive setpoint information, and a control device, the control device being configured to operate the LED driver outputs so as to drive the LED groups in accordance with the setpoint information,
wherein the control device is configured to:
determine an LED setpoint intensity and an LED setpoint colour temperature from the LED setpoint information, the LED setpoint intensity representing a desired combined intensity of the LED groups, the LED setpoint colour temperature representing a desired combined colour of the LED groups; and
compare the LED setpoint intensity to a predetermined threshold;
in case the LED setpoint intensity is above the predetermined threshold:
operate the LED driver outputs to mix the LED groups to jointly operate at the LED setpoint intensity and the LED setpoint colour temperature;

in case the LED setpoint intensity is below the predetermined threshold:
deviate from the LED setpoint colour temperature representing the desired combined colour of the LED groups by selecting a colour temperature of a single one of the LED groups, the colour temperature of the single one of the LED groups being different from the LED setpoint colour temperature,
select the single one of the LED groups having the selected colour temperature;
operate the LED driver output associated with the selected single one of the LED groups to drive the selected single one of the LED groups at the LED setpoint intensity; and
operate the remaining LED driver outputs to drive the remaining LED groups at zero LED intensity.

2. The LED driver according to claim 1 , wherein the control device is configured to select the single one of the LED groups based on the LED setpoint colour temperature.

3. The LED driver according to claim 1 , wherein the control device is further configured to:
select the single one of the LED groups as having a warmer colour temperature than the LED setpoint colour temperature of the LED set point information.

4. The LED driver according to claim 1 , wherein the control device is further configured to:
select the single one of the LED groups as nearest to the LED setpoint colour temperature in a chromaticity diagram.

5. The LED driver according to claim 1 , wherein the control device is further configured to:
select the single one of the LED groups as a nearest warmer colour temperature than the LED setpoint colour temperature.

6. The LED driver according to claim 1 , wherein the control device is further configured to set the predetermined threshold at substantially 1%, 5% or 10% of a nominal intensity of the LED groups.

7. The LED driver according to claim 1 , wherein the predetermined threshold is formed by a threshold range between a lower threshold and an upper threshold, the LED driver further being configured to provide a transition region from the LED setpoint colour temperature to the single LED group colour temperature, the transition region extending between the upper threshold and the lower threshold.

8. The LED driver according to claim 1 , comprising a current source configured to generate an LED drive current, and a switching module electrically connected to the current source and configured to switch, in accordance with the LED driver outputs, the LED drive current generated by the current source into a selection of the LED groups.

9. The LED driver according to claim 8 , wherein the current source is a switched mode current source, wherein the control device is configured to control the current source so as to control a magnitude of the LED drive current, the control device being configured to drive the LEDs based on the setpoint information by controlling the magnitude of the LED drive current and controlling the switching module so as to drive the switches.

10. An LED illumination assembly comprising:
a plurality of LEDs, the LEDs being arranged in groups having respective different colour temperatures, and
an LED driver according to claim 1 , the LED driver being connected to the plurality of LEDs for driving the plurality of LEDs.

11. The LED illumination assembly according to claim 10 , further comprising a current source configured to generate an LED drive current and at least one switch to modulate at least one of the LED groups, wherein the illumination assembly is configured to enable a modulation by the at least one switch to operate asynchronously in respect of a generation of the LED drive current by the current source.

12. The LED driver according to claim 1 , wherein, as the LED setpoint information adheres to a setpoint colour temperature curve in a chromaticity diagram, whereby, at the LED setpoint intensity below the threshold, the LED setpoint colour temperature does not coincide with the colour temperatures of each one of the LED groups, the control device is configured to:
deviate from the LED setpoint colour temperature;
select the single one of the LED groups of which the colour temperature does not coincide with the LED setpoint colour temperature; and
drive the selected single one of the LED groups of which the colour temperature does not coincide with the LED setpoint colour temperature, at the LED setpoint intensity.

Assignees

• Eldolab Holding Bv

Inventors

• Saes Marc
• Lydecker Stephen Haight

Classifications

• Y02B20/30

  Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED] · CPC title

• H05B45/48

  having LEDs organised in strings and incorporating parallel shunting devices · CPC title

• H05B45/10 Primary

  Controlling the intensity of the light · CPC title

• H05B45/20 Primary

  Controlling the colour of the light · CPC title