Patent Application Titled "Multichannel Lighting Unit and Driver for Supplying Current to Light Sources in Multichannel Lighting Unit" Published Online
The assignee for this patent application is
Reporters obtained the following quote from the background information supplied by the inventors: "Illumination devices based on semiconductor light sources, such as light-emitting diodes (LEDs), offer a viable alternative to traditional fluorescent, HID, and incandescent lamps. Functional advantages and benefits of LEDs include high energy conversion and optical efficiency, durability, lower operating costs, and many others. Recent advances in LED technology have provided efficient and robust full-spectrum lighting sources that enable a variety of lighting effects in many applications. Some of the fixtures embodying these sources feature one or more lighting units, including one or more LEDs capable of producing different colors, e.g. red, green, and blue, as well as a processor for independently controlling the output of the LEDs in order to generate a variety of colors and color-changing lighting effects. These lighting units may employ two or more groups or 'channels' of LEDs which produce light of different colors, each supplied with the proper current to enable generation and mixing of light to produce a desired lighting effect, for example, as discussed in detail in U.S. Pat. Nos. 6,016,038 and 6,211,626, incorporated herein by reference.
"In some lighting units, the first channel may include a first plurality of white LEDs (e.g., four LEDs) in series with each other, and the second channel may include a second plurality of red LEDs (e.g., two LEDs) in series with each other. A desired color effect of the lighting unit may be controlled by adjusting the current through the two channels. In some lighting units the channels are connected in series so that a single stream or channel of current flows through all the LEDs, and a shunt is provided across selected LEDs (e.g., the LEDs of the second channel) to divert the current away from selected LEDs to yield the desired color effect.
"Unfortunately, this arrangement typically entails a loss of energy and/or a complicated control scheme. For example, if the shunt is a linear shunt, it can result in additional unwanted power losses. A switching or puke-width modulated (PWM) shunt can be employed, but the known arrangements require a complicated drive scheme.
"Thus, there is a need in the art to provide a lighting unit with multiple ED channels which can be driven efficiently to achieve a desired lighting effect."
In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventor's summary information for this patent application: "The present disclosure is directed to a lighting unit and a driver for a lighting unit. For example, the present disclosure describes a lighting unit that includes at least two channels of light sources, and a driver for the light sources. The driver includes a DC/DC converter and a control arrangement for controlling the current supplied to at least one of the two channels in response to a control signal produced by the DC/DC converter. Beneficially, a feedback loop controls a switching device in the DC/DC converter to maintain the light level produced by the light sources at a desired level regardless of changes in the supply voltage and the load.
"Generally, in one aspect, an apparatus includes: a first channel of first light emitting devices (LEDs) connected in series with each other; a second channel of second LEDs connected in series with each other; and a driver for driving the first and second channels of LEDs. At least one of the second LEDs has a different color or color temperature than at least one of the first LEDs. The driver includes: a flyback converter, a buck converter, a pulse width modulator, and a feedback device. The flyback converter is configured to receive a first DC voltage and to output a second DC voltage, The buck converter is configured to receive the second DC voltage and to generate an output voltage that causes a first current to flow through the first channel of LEDs and a second current to flow through the second channel of LEDs. The pulse width modulator is configured to control the second current flowing through the second channel of LEDs in response to a control signal. The control signal is produced from an inductor winding in one of the flyback converter and the buck converter. The feedback device is configured to sample at least one of the first current and the second current and in response thereto to control a switching operation of the buck converter.
"In some embodiments, the first channel of LEDs is connected in series with the second channel of LEDs. The driver may include a temperature sensor configured to sense a temperature of at least one of the LEDs, and in response thereto to generate a feedback signal for adjusting the output voltage of the DC/DC converter. The driver may also include a light sensor configured to sense light produced by the LEDs, and in response thereto to generate a feedback signal for adjusting the output voltage of the DC/DC converter.
"Generally, in another aspect, an apparatus includes a first group of light sources connected in series with each other, a second group of light sources connected in series with each other, and a driver for driving the first and second groups of light sources. At least one of the light sources of the second group has a different color or color temperature than at least one of the light sources of the first group. The driver includes a DC/DC converter and a control device. The DC/DC converter is configured to receive a first DC voltage and to output an output voltage. The output voltage causes a first current to flow through the first group of light sources and a second current to flow through the second group of light sources. The control device is configured to control the second current provided to the second group of light sources in response to a control signal. The DC/DC converter produces the control signal.
"In some embodiments, the control device includes a pulse width modulator hat controls the second current flowing through to the second group of light sources by shunting the second current across one or more of the second light sources in response to the control signal. Also, the second light sources may have a different color or color temperature than the first light sources.
"In one embodiment, the DC/DC converter includes a flyback converter. The control signal for controlling the current flowing through the second group of light sources is produced by a winding of a transformer in the flyback converter. in another embodiment, the DC/DC converter includes a buck converter. The control signal for controlling the current flowing through the second group of light sources is produced by an inductor winding in the buck converter.
"Further, the driver may include a feedback device configured to sample at least one of the first current and the second current and in response thereto to control a switching operation of the DC/DC converter. Additionally or alternatively, the driver may include a sensor sensing a temperature or a light emitted by at least one of the first and second light sources, and in response thereto generates a feedback signal for adjusting the output voltage of the DC/DC converter.
"Generally, in still another aspect of the invention, a driver supplies a current to a plurality of light sources. The driver includes: a DC/DC converter and a control device. The DC/DC converter is configured to receive a first DC voltage and to output an output voltage. The output voltage causes a current to flow through the light sources. A control device is configured to control the current flowing through a portion of the light sources in response to a control signal. The control signal is produced by the DC/DC converter.
"In many embodiments, the control device includes a pulse width modulator that controls the current flowing through the portion of the light sources by shunting the current across one or more of the light sources in response to the control signal. In one embodiment, the DC/DC converter includes a flyback converter. The control signal is produced by a winding of a transformer in the flyback converter. In another embodiment, the DC/DC converter includes a buck converter. The control signal is produced by an inductor winding in the buck converter.
"The driver may include a feedback device configured to sample the current and in response thereto to control a switching operation of the DC/DC converter,
"As used herein for purposes of the present disclosure, the term 'LED' should be understood to include any electroluminescent diode or other type of carrier injection/junction-based system that is capable of generating radiation in response to an electric signal. Thus, the term LED includes, but is not limited to, various semiconductor-based structures that emit light in response to current, light emitting polymers, organic light emitting diodes (OLEDs), electroluminescent strips, and the like. In particular, the term LED refers to light emitting diodes of all types (including semi-conductor and organic light emitting diodes) that may be configured to generate radiation in one or more of the infrared spectrum, ultraviolet spectrum, and various portions of the visible spectrum (generally including radiation wavelengths from approximately 400 nanometers to approximately 700 nanometers). Some examples of LEDs include, but are not limited to, various types of infrared LEDs, ultraviolet LEDs, red LEDs, blue LEDs, green LEDs, yellow LEDs, amber LEDs, orange LEDs, and white LEDs (discussed further below). It also should be appreciated that LEDs may be configured and/or controlled to generate radiation having various bandwidths (e.g., full widths at half maximum, or FWHM) for a given spectrum (e.g., narrow bandwidth, broad bandwidth), and a variety of dominant wavelengths within a given general color categorization.
"For example, one implementation of an LED configured to generate essentially white light (e.g., a white LED) may include a number of dies which respectively emit different spectra of electroluminescence that, in combination, mix to form essentially white light. In another implementation, a white light LED may be associated with a phosphor material that converts electroluminescence having a first spectrum to a different second spectrum. In one example of this implementation, electroluminescence having a relatively short wavelength and narrow bandwidth spectrum 'pumps' the phosphor material, which in turn radiates longer wavelength radiation having a somewhat broader spectrum.
"It should also be understood that the term LED does not limit the physical and/or electrical package type of an LED. For example, as discussed above, an LED may refer to a single light emitting device having multiple dies that are configured to respectively emit different spectra of radiation (e.g., that may or may not be individually controllable). Also, an LED may be associated with a phosphor that is considered as an integral part of the LED (e.g., some types of white LEDs). In general, the term LED may refer to packaged LEDs, non-packaged LEDs, surface mount LEDs, chip-on-board LEDs, T-package mount LEDs, radial package LEDs, power package LEDs, LEDs including some type of encasement and/or optical element (e.g.., a diffusing lens), etc.
"The term 'light source' should be understood to refer to any one or more of a variety of radiation sources, including, but not limited to, LED-based sources (including one or more LEDs as defined above , incandescent sources (e.g., filament lamps, halogen lamps), fluorescent sources, phosphorescent sources, high-intensity discharge sources e.g., sodium vapor, mercury vapor, and metal halide lamps), lasers, other types of electroluminescent sources, pyroluminescent sources (e.g., flames), candle-luminescent sources (e.g., gas mantles, carbon arc radiation sources), photo-luminescent sources (e.g., gaseous discharge sources), cathode luminescent sources using electronic satiation, galvano-luminescent sources, crystallo-luminescent sources, kine-luminescent sources, thermo-luminescent sources, triboluminescent sources, sonoluminescent sources, radioluminescent sources, and luminescent polymers.
"A given light source may be configured to generate electromagnetic radiation within the visible spectrum, outside the visible spectrum, or a combination of both. Hence, the terms 'light' and 'radiation' are used interchangeably herein. Additionally, a light source may include as an integral component one or more filters (e.g., color filters), lenses, or other optical components. Also, it should be understood that light sources may be configured for a variety of applications, including, but not limited to, indication, display, and/or illumination. An 'illumination source' is a light source that is particularly configured to generate radiation having a sufficient intensity to effectively illuminate an interior or exterior space. In this context, 'sufficient intensity' refers to sufficient radiant power in the visible spectrum generated in the space or environment (the unit 'lumens' often is employed to represent the total light output from a light source in all directions, in terms of radiant power or 'luminous flux') to provide ambient illumination (i.e., light that may be perceived indirectly and that may be, for example, reflected off of one or more of a variety of intervening surfaces before being perceived in whole or in part).
"The term 'spectrum' should be understood to refer to any one or more frequencies (or wavelengths) of radiation produced by one or more light sources. Accordingly, the term 'spectrum' refers to frequencies (or wavelengths) not only in the visible range, but also frequencies (or wavelengths) in the infrared, ultraviolet, and other areas of the overall electromagnetic spectrum. Also, a given spectrum may have a relatively narrow bandwidth (e.g., a FWHM having essentially few frequency or wavelength components) or a relatively wide bandwidth (several frequency or wavelength components having various relative strengths). It should also be appreciated that a given spectrum may be the result of a mixing of two or more other spectra (e.g., mixing radiation respectively emitted from multiple light sources).
"For purposes of this disclosure, the term 'color' is used interchangeably with the term 'spectrum.' However, the term 'color' generally is used to refer primarily to a property of radiation that is perceivable by an observer (although this usage is not intended to limit the scope of this term). Accordingly, the terms 'different colors' implicitly refer to multiple spectra having different wavelength components and/or bandwidths. It also should be appreciated that the term 'color' may be used in connection with both white and non-white light. The term 'color temperature' generally is used herein in connection with white light, although this usage is not intended to limit the scope of this term. Color temperature essentially refers to a particular color content or shade (e.g., reddish, bluish) of white light. The color temperature of a given radiation sample conventionally is characterized according to the temperature in degrees Kelvin (K) of a black body radiator that radiates essentially the same spectrum as he radiation sample in question. Black body radiator color temperatures generally fall within a range of from approximately 700 degrees K (typically considered the first visible to the human eye) to over 10,000 degrees K; white light generally is perceived at color temperatures above 1500-2000 degrees
"The term 'lighting unit' is used herein to refer to an apparatus including one or more light sources of same or different types. A given lighting unit may have any one of a variety of mounting arrangements for the light source(s), enclosure/housing arrangements and shapes, and/or electrical and mechanical connection configurations. Additionally., a given lighting unit optionally may be associated with (e.g., include, be coupled to and/or packaged together with) various other components (e.g., control circuitry) relating to the operation of the light source(s). An 'LED-based lighting unit' refers to a lighting unit that includes one or more LED-based light sources as discussed above, alone or in combination with other non LED-based light sources. A 'multi-channel' lighting unit refers to an LED-based or non LED-based lighting unit that includes at least two light sources configured to respectively generate different spectrums of radiation, wherein each different source spectrum may be referred to as a 'channel' of the multi-channel lighting unit.
"It should be appreciated that all combinations of the foregoing concepts and additional concepts discussed in greater detail below (provided such concepts are not mutually inconsistent) are contemplated as being part of the inventive subject matter disclosed herein. In particular, all combinations of claimed subject matter appearing at the end of this disclosure are contemplated as being part of the inventive subject matter disclosed herein. It should also be appreciated that terminology explicitly employed herein that also may appear in any disclosure incorporated by reference should be accorded a meaning most consistent with the particular concepts disclosed herein.
BRIEF DESCRIPTION OF THE DRAWINGS
"In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention.
"FIG. 1. shows a functional block diagram of a lighting unit, according to various embodiment of the invention.
"FIG. 2 illustrates a first embodiment of a lighting unit.
"FIG. 3 illustrates one embodiment of a buck converter.
"FIG. 4 illustrates a second embodiment of a lighting unit.
"FIG. 5 illustrates a third embodiment of a lighting unit."
For more information, see this patent application: MOSS, Timothy B. Multichannel Lighting Unit and Driver for Supplying Current to Light Sources in Multichannel Lighting Unit. Filed
Keywords for this news article include: Electronics, Semiconductor, Light-emitting Diode,
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