News Column

Researchers Submit Patent Application, "Lighting Apparatus and Methods Using Oscillator-Based Dimming Control", for Approval

May 28, 2014



By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventor Hu, Yuequan (Morrisville, NC), filed on November 2, 2012, was made available online on May 15, 2014.

The patent's assignee is Cree, Inc.

News editors obtained the following quote from the background information supplied by the inventors: "Solid-state lighting arrays are used for a number of lighting applications. For example, solid-state lighting panels including arrays of solid-state light emitting devices have been used as direct illumination sources in architectural and/or accent lighting. A solid-state light emitting device may include, for example, a packaged light emitting device including one or more light emitting diodes (LEDs), which may include inorganic LEDs, which may include semiconductor layers forming p-n junctions and/or organic LEDs (OLEDs), which may include organic light emission layers.

"Solid-state lighting devices are also used in lighting fixtures, such as incandescent bulb replacement applications, task lighting, recessed light fixtures and the like. For example, Cree, Inc. produces a variety of recessed downlights, such as the LR-6 and CR-6, which use LEDs for illumination. Solid-state lighting panels are also commonly used as backlights for small liquid crystal display (LCD) screens, such as LCD display screens used in portable electronic devices, and for larger displays, such as LCD television displays.

"LEDs can be dimmed using, for example, linear dimming or pulse-width modulated (PWM) dimming, In a typical LED lighting apparatus, a microcontroller generates a PWM signal that is provided to a driver circuit that controls current passing through one or more LEDs. By varying the duty cycle of the PWM signal, the average current of the LEDs is proportionally changed, and the brightness of the LEDs varies accordingly. The PWM dimming control generally exhibits low appreciable color shift, and thus is widely used.

"Some conventional microcontroller-based dimming controllers implement linear dimming. Typically, the microcontroller samples a dimming control signal (e.g., from a commercial dimmer) and generates a PWM signal with its duty cycle varying with the dimming control signal. The PWM signal may be filtered with a low-pass filter, producing a DC voltage that is used to control a power stage of the driver circuit to adjust the LED current."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventor's summary information for this patent application: "Some embodiments provide an apparatus including a driver circuit configured to control a current through at least one LED responsive to a control signal. The apparatus further includes a modulated oscillator circuit configured to generate and modulate an oscillating signal responsive to a dimming signal and to generate the control signal responsive to the modulated oscillating signal.

"The modulated oscillator circuit may be configured to pulse width modulate the oscillating signal responsive to the dimming signal. The driver circuit may be configured to control the current through the at least one LED responsive to the pulse-width modulated oscillating signal. In further embodiments, the modulated oscillator circuit may include a filter configured to generate a voltage from the pulse-width modulated oscillating signal and the control signal may include the voltage.

"In some embodiments, the modulated oscillator circuit may include a sawtooth generator circuit configured to generate a sawtooth signal and a comparator configured to generate the pulse width modulated oscillating signal based on a comparison of the dimming signal to the sawtooth signal.

"According to additional embodiments, the modulated oscillator circuit may be configured to amplitude modulate the oscillating signal responsive to the dimming signal. In some embodiments, the modulated oscillator circuit may include a forward converter configured to generate a voltage responsive to the dimming signal and the control signal comprises the voltage.

"In some embodiments, the modulated oscillator circuit may be configured to galvanically isolate the control signal from the dimming signal. For example, the modulated oscillator circuit may be configured to galvanically isolate the control signal from the dimming signal using an opto-isolator or a transformer.

"In some embodiments, the driver circuit comprises an AC/DC converter, a DC/DC converter or a buck converter configured to control the current through the at least one LED responsive to the control signal. The dimming signal may include a voltage signal, such as a dimming signal produced by a commercial dimmer or occupancy sensor.

"Further embodiments provide apparatus as described above coupled to at least one LED.

"Additional embodiments provide methods of controlling a lighting apparatus. The methods include modulating an oscillating signal responsive to a dimming signal and controlling a current through at least one LED responsive to the modulated oscillating signal. Modulating an oscillating signal responsive to a dimming signal may include pulse width modulating the oscillating signal responsive to the dimming signal. Controlling a current through at least one LED responsive to the modulated oscillating signal may include filtering the pulse-width modulated signal to generate an voltage and controlling the current through the at least one LED responsive to the voltage. Pulse width modulating the oscillating signal responsive to the dimming signal may include comparing a sawtooth signal to the dimming signal to generate the pulse width modulated oscillating signal.

"In further embodiments, modulating an oscillating signal responsive to a dimming signal may include amplitude modulating the oscillating signal responsive to the dimming signal. Controlling a current through at least one LED responsive to the modulated oscillating signal may include generating a control signal from the modulated oscillating signal and controlling the current through the at least one LED responsive to the control signal, wherein the control signal is galvanically isolated from the dimming signal.

BRIEF DESCRIPTION OF THE DRAWINGS

"The accompanying drawings, which are included to provide a further understanding of the inventive subject matter and are incorporated in and constitute a part of this application, illustrate certain embodiment(s) of the inventive subject matter. In the drawings:

"FIG. 1 is a schematic block diagram illustrating an apparatus according to some embodiments;

"FIGS. 2-7 are schematic block diagrams illustrating different modulated oscillator circuits for the apparatus of FIG. 1 according to various embodiments; and

"FIGS. 8-11 are schematic block diagrams illustrating lighting apparatus according to various embodiments."

For additional information on this patent application, see: Hu, Yuequan. Lighting Apparatus and Methods Using Oscillator-Based Dimming Control. Filed November 2, 2012 and posted May 15, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=4975&p=100&f=G&l=50&d=PG01&S1=20140508.PD.&OS=PD/20140508&RS=PD/20140508

Keywords for this news article include: Cree Inc., Electronics, Microcontroller.

Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC


For more stories covering the world of technology, please see HispanicBusiness' Tech Channel



Source: Electronics Newsweekly


Story Tools






HispanicBusiness.com Facebook Linkedin Twitter RSS Feed Email Alerts & Newsletters