Spectral shift control for dimmable AC LED lighting

• US 9,775,212 B2
• Filed: 06/27/2016
• Issued: 09/26/2017
• Est. Priority Date: 08/14/2009
• Status: Active Grant

• Current Assignee: Signify North America Corporation (Signify N.V.)
• Original Assignee: Once Innovations Inc. (Signify N.V.)
• Inventors: Grajcar, Zdenko, Klassen, Brad, Erickson, Leif
• Primary Examiner(s): PHAM, THAI N
• Application Number:
  US15/193,225
• Publication Number:
  US 20160381756A1
• Time in Patent Office: 456 Days
• Field of Search: 315185 R, 315192, 315291, 315294, 315307, 315312
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/37 Converter circuits
• CPC Class Codes: H05B 45/44 with an active control inside an LED matrix
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices
• CPC Class Codes: H05B 47/105 in response to determined parameters

Abstract

Apparatus and associated methods involve operation of an LED light engine in which a relative intensities of selected wavelengths shift as a function of electrical excitation. In an illustrative example, current may be selectively and automatically diverted substantially away from at least one of a number of LEDs arranged in a series circuit until the current or its associated periodic excitation voltage reaches a predetermined threshold level. The diversion current may be smoothly reduced in transition as the excitation current or voltage rises substantially above the predetermined threshold level. A color temperature of the light output may be substantially changed as a predetermined function of the excitation voltage. For example, some embodiments may substantially increase or decrease a color temperature output by a solid state light engine in response to dimming the AC voltage excitation (e.g., by phase-cutting or amplitude modulation).

Claims

1. A method of conditioning current in a light engine steps comprising:

providing a pair of input terminals that receive a periodic excitation voltage;

receiving a current of equal magnitude and opposite polarity into each one of the pair of terminals, said current flowing in response to the excitation voltage;

providing a plurality of light emitting diodes (LEDs) arranged in a first network, said first network arranged to conduct said current in response to the excitation voltage exceeding at least a forward threshold voltage associated with the first network;

providing a plurality of LEDs arranged in a second network in series relationship with said first network;

providing a bypass path in parallel with the second network;

diverting the current from the first network with dimming conditioning circuitry as a function of the waveform of the periodic excitation voltage; and

wherein a resistor within the dimming conditioning circuitry dynamically increases an impedance of the bypass path as a substantially smooth and continuous function of said current amplitude in response to said current amplitude increasing in the range above the threshold current.

2. The method of claim 1 wherein the current is diverted as the waveform of the periodic excitation voltage approaches zero volts.

3. The method of claim 1 wherein the dimming conditioning circuitry comprises at least one transistor in series with a resistor.

4. The method of claim 3 wherein the dimming conditioning circuitry further comprises at least one diode in series with the resistor.