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EP-3991521-B1 - DIM-TO-WARM LED CIRCUIT

EP3991521B1EP 3991521 B1EP3991521 B1EP 3991521B1EP-3991521-B1

Inventors

  • QIU , Yifeng

Dates

Publication Date
20260506
Application Date
20200623

Claims (11)

  1. A dim-to-warm circuit apparatus, comprising: - an LED multi-colored array (630) comprising three LED arrays (631, 633, 635) of different colors; and - a hybrid driving-circuit (600) configured to be coupled to the LED multi-colored array (630), the hybrid driving-circuit (600) configured to receive a luminous-signal level and to adjust a color temperature and a corresponding luminous flux of the LED arrays (631, 633, 635) based on the received luminous-signal level: characterized in that the hybrid driving-circuit includes: an analog current-division circuit (610A) configured to divide an input current (lo) into a first current (I L ) and a second current (I R ) as output on a first branch-line (619L) and a second branch-line (619R); and a multiplexer array (620) coupled between the analog current-division circuit (610A) and the LED multi-colored array (630), the multiplexer array (620) being configured - to provide the first current (I L ) to a first LED array (631) and the second current (I R ) to a second LED array (633), substantially simultaneously, during a first portion of a time period; - to provide the first current (I L ) to the second LED array (633) and the second current (I R ) to a third LED array (635), substantially simultaneously, during a second portion of the time period; - to provide the first current (I L ) to the first LED array (631) and the second current (I R ) to the third LED array (635), substantially simultaneously, during a third portion of the time period; and wherein the analog current-division circuit (610A) includes - a first sense-resistor (615L) to sense a first voltage (V SENSE_R1 ) of the first branch line (616L) and a second sense-resistor (615R) to sense a second voltage (V SENSE_R2 ) of the second branch-line (616R); - a voltage-controlled current source (611) configured to supply current to the first branch-line (619L)and the second branch-line (619R); and - a computational device (610B, 650) configured to compare the first sensed-voltage (V SENSE_R1 ) and the second sensed-voltage (V SENSE_R2 ) to determine and supply a set voltage (V SET ), the set voltage (V SET ) being an input voltage to the voltage-controlled current source (611).
  2. The dim-to-warm circuit apparatus of claim 1, further comprising an LED driver (601) electrically coupled to a voltage regulator (603), the voltage regulator configured to provide a voltage signal for the LED multi-colored array (630), a combination of the LED driver and the voltage regulator to provide a stabilized current as the input current (lo) to the analog current-division circuit (610A).
  3. The dim-to-warm circuit apparatus of claim 1 or 2, wherein the multiplexer array (620) comprises at least four switching devices (621, 623, 625, 627).
  4. The dim-to-warm circuit apparatus according to any of the preceding claims, wherein the analog current-division circuit (610A) is configured to supply equal amounts of current to the three LED arrays (631, 633, 635).
  5. The dim-to-warm circuit apparatus according to any of claims 1 to 3, wherein the analog current-division circuit (610A) is configured to supply unequal amounts of current to the three LED arrays (631, 633, 635).
  6. The dim-to-warm circuit apparatus according to any of the preceding claims, wherein the computational device (610B, 650) further includes a resistive divider circuit (R upper . R lower ) and amplifier (612) configured to provide an amplified voltage signal (V SENSE_AMPLIFIED ), that is an amplified version of the set voltage (V SET ).
  7. The dim-to-warm circuit apparatus according to any of the preceding claims, wherein the hybrid driving-circuit is further configured to supply a pulse-width modulation time slicing signal to selected LED arrays (631, 633, 635) of the LED multi-colored array (630).
  8. The dim-to-warm circuit apparatus according to any of claims 1 to 5, wherein the computational device (650) comprises a microcontroller configured to map the received luminous-signal level to a correlated color temperature to provide an input to set the color temperature of the LED multi-colored array (630).
  9. The dim-to-warm circuit apparatus according to the preceding claim, wherein the microcontroller is configured to store a digitized correlated color temperature versus current curve based on the received luminous-signal level, the digitized CCT versus current curve to provide an input to set the color temperature of the LED multi-colored array (630).
  10. The dim-to-warm circuit apparatus according to any of the preceding claims, wherein the LED multi-colored array comprises at least one of: at least one red LED, at least one green LED, and at least one blue LED, or at least one desaturated red LED, at least one desaturated green LED, and at least one desaturated blue LED.
  11. A method of providing a dim-to-warm operation of an LED multi-colored array (630) comprising three LED arrays (631, 633, 635) of different colors, using the dim-to-warm circuit apparatus according to any of claims 1 to 10, comprising the steps of: determining a luminous flux level desired of the LED multi-colored array (630); correlating the luminous flux level to a color temperature of the LED multi-colored array (630); dividing an input current (lo) into a first current (I L ) and a second current (I R ); and based on a determination of the color temperature: providing the first current (I L ) to a first LED array (631) and providing the second current (I R ) to a second LED array (633) substantially simultaneously during a first portion of a time period; providing the first current (I L ) to the second LED array (633) and providing the second current (I R ) to a third LED array (635) substantially simultaneously during a second portion of the time period; and providing the first current (I L ) to the first LED array (631) and providing the second current (I R ) to the third LED array (635) substantially simultaneously during a third portion of the period.

Description

TECHNICAL FIELD The subject matter disclosed herein relates to color tuning of one or more light-emitting diode arrays (LEDs) that comprise a lamp operating substantially in the visible portion of the electromagnetic spectrum. More specifically, the disclosed subject matter relates to a technique to enable a single color-tuning device (e.g., a dimmer) controls a dim-to-warm color-tuning apparatus in which a color temperature of the LEDs decreases as the LEDs are dimmed in intensity. BACKGROUND Light-emitting diodes (LEDs) are commonly used in various lighting operations. It is often desirable to be able to dim an LED lamp, and the prior art considers various approaches such as proposed in US2014333216A1 and DE112013006888T5. The color appearance of an object is determined, in part, by the spectral power density (SPD) of light illuminating the object. For humans viewing an object, the SPD is the relative intensity for various wavelengths within the visible light spectrum. However, other factors also affect color appearance. Also, both a correlated color temperature (CCT) of the LED, and a distance of the temperature of the LED on the CCT from a black-body line (BBL, also known as a black-body locus or a Planckian locus), can affect a human's perception of an object. In particular there is a large market demand for LED lighting solutions, such as in retail and hospitality lighting applications, where a color temperature of the LEDs can be controlled. Specifically, there is an increasing market demand for dim-to-warm lights for home and office installations. Contemporaneous lighting systems have attempted to satisfy this dim-to-warm LED mark by using two control devices: one for light output (e.g., luminous flux), and a separate device for CCT control. However, having two devices is costly to install. It would be ideal to have the LED light change its color temperature in relation to an amplitude of the incoming current while using only a single control-device. The information described in this section is provided to offer the skilled artisan a context for the following disclosed subject matter and should not be considered as admitted prior art. BRIEF DESCRIPTION OF THE FIGURES FIG. 1 shows a portion of an International Commission on Illumination (CIE) color chart, including a black body line (BBL);FIG. 2A shows a chromaticity diagram with approximate chromaticity coordinates of colors for typical red (R), green (G), and blue (B) LEDs, on the diagram, and including a BBL;FIG. 2B shows a revised version of the chromaticity diagram of FIG. 2A, with approximate chromaticity coordinates for desaturated R, G, and B LEDs in proximity to the BBL, in accordance with various embodiments of the disclosed subject matter;FIG. 3 shows a color-tuning device of the prior art requiring a separate flux control-device and a separate CCT control-device;FIG. 4 shows an exemplary embodiment of a color-tuning device using a single control-device, in accordance with various embodiments of the disclosed subject matter;FIG. 5 shows an example of a graph indicating color temperature as a function of luminous flux, in accordance with various embodiments of the disclosed subject matter;FIG. 6A shows an exemplary embodiment of a color-tuning circuit, in accordance with various exemplary embodiments of the disclosed subject matter;FIG. 6B shows an exemplary embodiment of a microcontroller that may be used with the color-tuning circuit of FIG. 6A; andFIG. 7 shows an example of a method to provide a dim-to-warm operation of an LED light source in accordance with various exemplary embodiments of the disclosed subject matter. DETAILED DESCRIPTION The disclosed subject matter will now be described in detail with reference to a few general and specific embodiments as illustrated in various ones of the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the disclosed subject matter. It will be apparent, however, to one skilled in the art, that the disclosed subject matter may be practiced without some or all of these specific details. In other instances, well-known process steps or structures have not been described in detail so as not to obscure the disclosed subject matter. Examples of different light illumination systems and/or light emitting diode implementations will be described more fully hereinafter with reference to the accompanying drawings. Accordingly, it will be understood that the examples shown in the accompanying drawings are provided for illustrative purposes only and they are not intended to limit the disclosure in any way. Like numbers refer generally to like elements throughout. Semiconductor-based light-emitting devices or optical power-emitting-devices, such as devices that emit ultraviolet (UV) or infrared (IR) optical power, are among the most efficient light sources currently available. These devices may include light emitting diodes,