Koninklijke Philips Corporation N.v.

Philips Electronics North America Corporation

Semtech Corporation

U.S. Philips Corporation

Chin Chang

Gert W Bruning

Subramanian Muthu

Joseph En-Cheng Chang

Shaomin Peng

Adan F Hernandez

Bernd Clauberg

Hao Peng

Da Feng Weng

James M Gaines

Roderick T Hinman

Yushan Li

Frank J Schuurmans

Jurgen M Willaert

Veter Chang

Theo Stommen

Roderick T Himman

A system and method for controlling a digital pulse-width modulated power converter achieves a fast large-signal transient response while maintaining a slow response near the steady-state operating point in order to assure stability and to reduce the system's susceptibility to noise. Digital output error samples are processed through a gain scheduling block that applies a non-linear gain function to produce a weak loop response when the system is near its steady-state equilibrium point and a strong loop response when large transients are encountered. The resulting system maintains a fast transient response to large error signals while reducing noise and loop jittering and assuring loop stability.

Digital control of PWM converters with nonlinear gain scheduling

An apparatus and method of controlling power converters is achieved that produces high light-load efficiency and reduced output voltage ripple while maintaining quiet operation that is free from audible noise. The inventive method includes a variable on-time control circuit that is applicable to a wide variety of switching mode converters, including, but not limited to, boost converters, buck converters, buck-boost converters, single-ended primary inductor (SEPIC) converters, and other converter topologies, both isolated and non-isolated.

Variable on-time control method for high light-load efficiency, small output voltage ripple, and audible-noise-free operation

RGB filter set and color estimation performance for RGB LED color sensing is provided. A criteria function describing an error between desired color matching functions and a spectral response of an RGB filter set is constructed. RGB filter set response characteristics based on the criteria function are then determined. Finally, color estimation parameters for substantially optimal color estimation with the RGB filter set are determined based upon the determined RGB filter set response characteristics. Computer readable code for constructing a criteria function is provided. Computer readable code for determining RGB filter set response characteristics is also provided. Finally, computer readable code for determining color estimation parameters is provided.

Transformation structures for approximating color matching functions

Methods and apparatuses are provided for monitoring an inductor output current delivered to a load by a power converter. For example, there is provided an apparatus comprising: at least one power switch operatively coupled to an input voltage source; an output inductor operatively coupled to the at least one power switch and to the load; and a current sensor operatively coupled to the output inductor, the current sensor providing a current sense signal corresponding to the inductor output current delivered to the load. In one embodiment, the current sensor comprises: a filter comprising a first resistor coupled in series with a first capacitor; and a second capacitor coupled in parallel with the first resistor, the first and second capacitors forming an AC voltage divider to increase the signal-to-noise ratio of the current sense signal.

Method and apparatus for improved current mode control for large conversion ratio synchronous buck converter with lossless current sense

Improved stability in a regulator having a sample-and-hold. Coupling an input voltage to an input node of the sample-and-hold circuit is provided. Activating the sample-and hold circuit in response to the input voltage and sensing an output voltage at an output node coupled to the sample and hold circuit is also provided. Determining whether the input voltage at the input node is greater than the output voltage at the output node and providing a sample-and-hold function based on the determination are also provided. A regulation circuit is provided. A sample-and-hold circuit coupled to input and output nodes is also provided. The transfer function of the sample-and-hold circuit is pseudo-all-pass if the input voltage at the input node is greater than an output voltage at the output node and is a substantially constant signal if the input voltage at the input node is less than the output voltage at the output node.

PWM LED regulator with sample and hold

A system and method for identifying primary color chromaticity coordinates of a red, green and blue light sources includes a tristimulus filter the receives the combined light generated by the light sources. The light sources are preferably a group of red, green and blue light emitting diodes. A processor is configured to generate a plurality of test control signals that sets a desired intensity value for each of the red, green and blue LEDs. Based on these test control signals, the system is configured to measure three sets of chromaticity coordinates corresponding to the combined light generated by these red, green and blue LEDs. The processor thereafter calculates the color chromaticity coordinates of the LEDs, based on the measured coordinates of the combined light, and the intensity values of the LEDs, and the intensity values of the combined light. This calculation in accordance with one embodiment of the invention is accomplished by solving a matrix equation. Once the color coordinates of the individual light sources is uniquely calculated, the system measures the intensity values of light for each of the light sources that is necessary to provide a combined light with a desired color chromaticity coordinates. These intensity values can be used in a feedback control circuit to maintain the desired combined light as the LEDs change their characteristics from batch to batch or over time.

RGB primary color point identification system and method

The liquid crystal display panel of the present invention provides rapid highlighting of the display. To provide highlighting, current to the backlighting lamp is increased from a normal current to a highlighting current. During the transition from the normal current to the highlighting current, the current to backlighting lamp is increased to an intermediate current above the highlighting current, and then decreased to the highlighting current. The increase to an intermediate current provides greater energy to the backlighting lamp than a direct increase from the low current to the highlighting current. The increased energy heats the backlighting lamp quickly to provide the increased light for highlighting. In addition, reducing the current to the backlighting lamp below the normal current when leaving the highlighting mode decreases the time to leave the highlighting mode.

Seamless highlighting in LCD monitors and LCD-TV

A backlight for an LCD display comprised of an array of LEDs. The backlight may be driven and controlled by a fast pulse power converter, thus providing a response time for the backlight on the order of microseconds. The backlight may thus be used for image display, for example, in the depiction of images in a video input to the LCD and removal of image artifacts.

Control and drive circuit arrangement for illumination performance enhancement with LED light sources

An improved electronic LCD backlighting inverter circuit for high frequency operation under low frequency pulse width modulation (PWM) for dimming control. The improved electronic LCD backlighting inverter is based on a voltage-fed push-pull LLC resonant inverter circuit configuration including a resonant inductor (L), magnetizing inductance of an output transformer (L), and resonant capacitor (C). For large values of magnetizing inductance the LLC circuit effectively becomes an LC resonant circuit. By synchronizing the high frequency switching signal and the low frequency modulation frequency using logic control circuitry, a wide dimming range and higher efficiency are achieved under PWM control.

Voltage-fed push LLC resonant LCD backlighting inverter circuit

An autonomous solid state lighting system has a charge mode which collects energy and produces electric power with a solid state energy source, converts the voltage of the electric power using a bi-directional power converter, and stores the power in an energy storage device. A discharge mode draws electric power from the energy storage device, converts the voltage of the electric power using the bi-directional power converter, and produces light from a solid state light source. A controller controls the charge and discharge modes. In one embodiment, the solid state energy source can be a solar cell panel, the solid state light source can be an LED module, and the energy storage device can be a battery pack.

Autonomous solid state lighting system

Apparatus and method for backlighting an electronic display with LEDs to control luminosity, radiometric power, and color levels by means of feedback control through a microprocessor, thereby maintaining white backlight at substantially constant levels, which can be chosen by an operator.

LED-based white-light backlighting for electronic displays

An apparatus for controlling overshoots in the switching of LED arrays in a system having a switching voltage converter providing the biasing voltage for the LED array. By synchronizing a switching converter to an LED turn-on signal, loading on the voltage converter can be controlled such that output conduction of the converter only occurs when LEDs that are to be displayed are switched on to provide loading to the output of the converter. A Sample and hold method is employed to effectively store the current information in a previous &ldquo;on&rdquo; interval and use it for the current control in a following interval with inhibited current overshoot.

Sample and hold method to achieve square-wave PWM current source for light emitting diode arrays

A solar cell array is provided having a lattice or matrix structure such that no two solar cell devices are connected purely in series or purely in parallel. Accordingly, if a single solar cell device fails, there is an alternate path by which the output power of all other solar cell devices may contribute to the total output power of the solar cell array. Also, the power output of the entire array is much less sensitive to a low voltage or current for a single solar cell device than in a conventional array where devices are connected in series and in parallel. Beneficially, current setting devices, such as resistors, are provided for better matching the voltages and currents within the array, although in some applications, the resistors can be eliminated, or set to zero. The lattice or matrix structures may be extended in one, two, and three-dimensional patterns.

Solar cell array having lattice or matrix structure and method of arranging solar cells and panels

An integrated LED driving device for multiple LED strings which employs a single linear regulator or other controller and a multiple-output current mirror which is almost independent of the DC input voltage source, almost independent of the transistor's or MOSFET's variations from the semiconductor integration process, and almost independent of temperature variation. The multiple-output current mirror includes a plurality of transistors or MOSFETs each of which are integrated on the same substrate, with identical width-to-length channel ratios and with identical source and gate connections. The integrated LED driving device provides for automatic current sharing in a DC mode and, alternately, with minimized phase delays in a PWM mode. The mirror-output current mirror may include mirror-cascode transistor pairs.

Integrated LED driving device with current sharing for multiple LED strings

The invention provides a method of determining tristimulus values for light emitting diode illuminants. A localized transformation matrix is determined based on a set of spectral responsivity data and a set of color-matching functions. A set of color responses associated with light emitted from the light emitting diode illuminants may be measured, and an estimate of tristimulus values based on the localized transformation matrix and the set of color responses may be determined.

Growing community of inventors

Yorktown Heights, NY, United States of America

Chin Chang