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Color mixing for solid state lighting using direct AC drives

  • US 9,844,114 B2
  • Filed: 12/09/2016
  • Issued: 12/12/2017
  • Est. Priority Date: 12/09/2015
  • Status: Active Grant
First Claim
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1. A system for controlling light-emitting diode (LEDs) to produce light having a target color rendering index (CRI) across a range of color temperatures, the system comprising:

  • a power source capable of providing a voltage signal comprising a rectified alternating current (AC) signal;

    multiple LEDs capable of receiving the rectified signal from the power source, wherein;

    a first group of LEDs has a first range of color temperatures and a first CRI value above or equal to a target CRI level, wherein the target CRI provides an accurate perception of color, wherein the first CRI value is constant over the first range of color temperatures, anda second group of LEDs has a second range of color temperatures and a second CRI value different from the target CRI level, wherein a portion of the second range of color temperatures is cooler than the first range of color temperatures, wherein the second CRI value is constant over the second range of color temperatures; and

    a microcontroller capable of receiving the rectified signal and a control signal, wherein the microcontroller is configured to (i) produce a current based on the rectified signal, wherein a level of the current is based on a level of the control signal, (ii) provide the current to one or more of the groups of LEDs, and (iii) control the groups of LEDs to produce light based on the received control signal, such that;

    when the level of the control signal is above a first control threshold and below a second control threshold, the microcontroller provides current having a first level to the first group of LEDs, such that the first group of LEDs produces light having a first color temperature within the first range of color temperatures and having a first CRI level above or equal to the target CRI level, andwhen the control signal is above the second control threshold and below a third control threshold, the microcontroller provides current having a second level to the first and second groups of LEDs, such that the first and second groups of LEDs produce light having a second color temperature within the second range of color temperatures and having a second CRI level approximately equal to the target CRI level.

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