| Patent application number | Description | Published |
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| 20080246457 | Voltage up-conversion circuit - According to one exemplary embodiment, a voltage up-conversion circuit includes a modulated voltage generator circuit, where the modulated voltage generator circuit is configured to receive an input voltage and generate a modulated voltage, and where the modulated voltage generator circuit includes at least one transistor. The voltage up-conversion circuit further includes a switching circuit coupled to the modulated voltage generator circuit, where the switching circuit is configured to couple the modulated voltage to a load capacitor when the modulated voltage is at a high level and decouple the modulated voltage to the load capacitor when the modulated voltage is at a low level. In the voltage up-conversion circuit, the load capacitor reaches a voltage greater a breakdown voltage of the at least one transistor in the modulated voltage generator circuit. The breakdown voltage can be a reliability breakdown voltage. | 10-09-2008 |
| 20090108776 | CIRCUIT FOR PROVIDING AN APPROXIMATELY CONSTANT RESISTANCE AND/OR CURRENT AND METHOD THEREFOR - A circuit can provide an approximately constant resistance value that is virtually independent of process and temperature variations. A current control circuit may use a device that tracks the changes in a corresponding device over process and temperature variations. As a result, the behavior of device may be used to help determine the control information provided to device in order to maintain an approximately constant resistance Rm over process and temperature variations. The approximately constant resistance Rm may be used to provide an approximately constant current I | 04-30-2009 |
| 20090230874 | LED DRIVER WITH SEGMENTED DYNAMIC HEADROOM CONTROL - Techniques for dynamic headroom control in a light emitting diode (LED) system are disclosed. An output voltage is provided to drive a plurality of LED strings. A feedback controller monitors the tail voltages of the LED strings to identify the minimum tail voltage and adjusts the output voltage based on the lowest tail voltage. The LED strings grouped into subsets and the feedback controller is segmented such that, for a certain duration, a minimum tail voltage is determined for each subset. The minimum tail voltages of the subsets are used to determine the overall minimum tail voltage of the plurality of LED strings for the certain duration so as to control the output voltage in the following duration. The segments of the feedback controller can be implemented in separate integrated circuit (IC) packages, thereby facilitating adaptation to different numbers of LED strings by integrating the corresponding number of IC packages. | 09-17-2009 |
| 20090230891 | LED DRIVER WITH DYNAMIC POWER MANAGEMENT - Power management in a light emitting diode (LED) system having a plurality of LED strings is disclosed. A voltage source provides an output voltage to drive the LED strings. An LED driver monitors the tail voltages of the active LED strings to identify the minimum, or lowest, tail voltage and adjusts the output voltage of the voltage source based on the lowest tail voltage. The LED driver can adjust the output voltage so as to maintain the lowest tail voltage at or near a predetermined threshold voltage so as to ensure that the output voltage is sufficient to properly drive each active LED string with a regulated current in view of pulse width modulation (PWM) performance requirements without excessive power consumption. | 09-17-2009 |
| 20090273288 | LED DRIVER WITH DYNAMIC POWER MANAGEMENT - A light emitting diode (LED) system implements a LED driver to drive a set of one or more LED strings. The LED driver includes a voltage source to provide an adjustable output voltage to a head end of each LED string of the set for a first duration and a second duration following the first duration. The LED driver further includes a feedback controller to control the voltage source to adjust the output voltage for the second duration based on a digital code value generated from a minimum tail voltage of one or more tail voltages of the set at a sample point of the first duration. The LED driver further includes a power controller to temporarily enable one or more components of the feedback controller for a sample period of the first duration, the sample period comprising the sample point. | 11-05-2009 |
| 20090315481 | METHOD AND DEVICE FOR LED CHANNEL MANAGMENT IN LED DRIVER - Disclosed are example open channel detection techniques at a light emitting diode (LED) driver of an LED system. The LED driver does not enable its LED channels before normal operation so as to inhibit current flow through the LED channels during start-up. While the LED channels are disabled, the LED driver compares the voltages at the LED channel inputs with a predetermined voltage to determine whether an operational LED string of an associated LED panel is connected to the LED channel. In the event that an LED channel is determined to be an “open” channel, the LED driver further disables the LED channel for the following normal operational mode. Otherwise, if the LED channel is determined to be connected to an operational LED string, the LED driver enables the LED channel for the normal operational mode, during which the LED channel can be selectively activated for light output subject to display data for the LED panel. | 12-24-2009 |
| 20100026203 | LED DRIVER WITH FRAME-BASED DYNAMIC POWER MANAGEMENT - Disclosed are example techniques for frame-based power management in a light emitting diode (LED) system having a plurality of LED strings. A voltage source provides an output voltage to drive the LED strings. An LED driver generates a frame timing reference representative of the frame rate or display timing of a series of image frames to be displayed via the LED system. An update reference is generated from the frame timing reference. The LED driver monitors one or more operating parameters of the LED system. In response to update triggers marked by the update reference, the LED driver adjusts the output voltage of the voltage source based on the status of each of the one or more monitored operating parameters (either from the previous update period or determined in response to the update trigger), thereby synchronizing the updating of the output voltage to the frame rate (or a virtual approximation of the frame rate) of the video being displayed. | 02-04-2010 |
| 20100085295 | FREQUENCY SYNTHESIS AND SYNCHRONIZATION FOR LED DRIVERS - A PWM generation module generates a PWM data signal used to control a light emitting diode (LED) driver for one or more strings of LEDs of a display device. The PWM data signal is synchronized with the frame boundaries of the video content being displayed. The PWM generation module can configure the PWM data signal such that a new PWM cycle is initiated at the start of each successive frame, and further whereby those PWM cycles that would be prematurely terminated at frame boundaries are instead driven at a constant reference level until the frame boundary. With this configuration, a substantially linear average light intensity can be achieved across frames, thereby reducing or eliminating display distortion that is often present in other PWM cycle synchronization techniques. The PWM generation module can use a self-learning process to make adjustments to the expected number of completeable PWM cycles per frame in response to dynamic changes in the frame rate, PWM frequency, or other related display parameters. | 04-08-2010 |
| 20100156315 | LED DRIVER WITH FEEDBACK CALIBRATION - Power management in a light emitting diode (LED) system having a plurality of LED strings is disclosed. A voltage source provides an output voltage to drive a plurality of LED strings. An LED driver implements a feedback mechanism to monitor the tail voltages of the active LED strings to identify the minimum tail voltage and adjust the output voltage of the voltage source based on the lowest tail voltage. A loop calibration module of the LED driver calibrates the feedback mechanism of the LED driver based on a relationship between a digital code value used to generate a particular output voltage and another digital code value generated based on the minimum tail voltage resulting from the particular output voltage. | 06-24-2010 |
| 20100194308 | LED DRIVER WITH DYNAMIC HEADROOM CONTROL - A voltage source provides an output voltage to drive a plurality of light emitting diode (LED) strings. A LED driver adjusts the level of the output voltage so as to maintain the lowest tail voltage of the LED strings at or near a predetermined threshold voltage so as provide sufficient headroom voltages for current regulators for the LED strings. The LED driver operates in an operational mode and a calibration mode, which can be implemented in parallel with, or part of, the operational mode. During the calibration mode, the LED driver determines, for each LED string, a code value representative of the level of the output voltage necessary to maintain the tail voltage of the corresponding LED string at or near the predetermined threshold voltage. In the operational mode, the code values from the calibration mode are used to control the voltage source to provide an appropriate level for the output voltage. | 08-05-2010 |
| 20100201278 | SERIAL CONFIGURATION FOR DYNAMIC POWER CONTROL IN LED DISPLAYS - A power management technique in a light emitting diode (LED) system is disclosed. The LED system includes a plurality of LED driver connected in series, each LED driver configured to regulate the current flowing through a corresponding subset of a plurality of LED strings. Each LED driver determines the minimum tail voltage of the LED strings of the corresponding subset, compares the determined minimum tail voltage with an indicator of a minimum tail voltage of one or more other subsets provided from an upstream LED driver in the series, and then provides an indicator of the lower of the two tail voltages to the downstream LED driver. In this manner an indicator of the minimum tail voltage of the plurality of LED strings is cascaded through the series. A feedback controller monitors the minimum tail voltage represented by the cascaded indicator and accordingly adjusts an output voltage provided to the head ends of the plurality of LED strings. | 08-12-2010 |
| 20100201279 | SERIAL CASCADE OF MINIMIUM TAIL VOLTAGES OF SUBSETS OF LED STRINGS FOR DYNAMIC POWER CONTROL IN LED DISPLAYS - A light emitting diode (LED) system implements a power management technique. The LED system includes a plurality of LED drivers connected in series, each LED driver configured to regulate the current flowing through a corresponding subset of a plurality of LED strings. Each LED driver determines the tail voltages of the one or more LED strings of the corresponding subset. Each LED driver, except for the first LED driver in the series, also receives a voltage representative of the minimum tail voltage of the other subsets regulated by the upstream LED drivers. Each LED driver then provides the lowest of the voltage received from the upstream LED driver and the one or more tail voltages of the corresponding subset to the downstream LED driver. In this manner a voltage representative of the minimum tail voltage of the plurality of LED strings is cascaded through the series. A feedback controller monitors the minimum tail voltage represented by this cascaded voltage and accordingly adjusts an output voltage provided to the head ends of the plurality of LED strings. | 08-12-2010 |
| 20100264837 | PEAK DETECTION WITH DIGITAL CONVERSION - A peak detection/digitization circuit includes a plurality of level detect units, each having a comparator and a flip-flop with a clock input responsive to the output of the comparator. For a detection period, each level detect unit configures a data output signal of the flip-flop to a first data state responsive to a start of the detection period. Further, each level detect unit is configured to enable the comparator responsive to the data output signal having the first data state or a second data state, respectively. While the comparator is enabled during the detection period, the level detect unit configures the data output signal of the flip-flop responsive to a comparison of an input signal to a corresponding reference voltage level by the comparator. The data output signals of the flip-flops of the level detect units at the end of the detection period are used to determine a digital value representative of a peak voltage level of the input signal. | 10-21-2010 |
| 20110012519 | ANALOG-TO-DIGITAL CONVERTER WITH NON-UNIFORM ACCURACY - An analog-to-digital converter (ADC) implements non-uniform conversion accuracy so as to allow for high conversion accuracy for a select narrower input range while also accommodating a wider overall input range and requiring fewer conversion bits compared to conventional ADCs. The ADC includes an ADC core that receives an input signal and outputs a first digital value having a first number of bits, the first digital value based on the input signal and an accuracy configuration of the ADC core. The ADC also includes an encoder to generate a second digital value have a second number of bits, greater than the first number of bits, based on the first digital value and the accuracy configuration of the ADC core. The ADC further includes an accuracy controller to adjust the accuracy configuration of the ADC core based on a relationship between the first digital value and at least one threshold. | 01-20-2011 |
| 20110032008 | PULSE WIDTH MODULATION FREQUENCY CONVERSION - A pulse width modulation (PWM) frequency converter converts an input PWM signal to an output PWM signal having a different frequency while maintaining a substantially equal duty ratio. The PWM frequency converter samples the input PWM signal for a PWM cycle using a sampling clock. A filter module filters the resulting set of one or more PWM parameters to compensate for noise introduced by potential clock mismatch, clock jitter, ambient variations, and other non-deterministic issues, thereby generating filtered PWM parameters. The sampling employed by the filter module compares a difference between the one or more current PWM parameters and previous (or historical) PWM parameters from an earlier sampled PWM cycle to a predetermined change threshold in determining a filtered set of one or more PWM parameters. The filtered set of one or more PWM parameters then is used to generate one or more corresponding PWM cycles of the output signal. | 02-10-2011 |
| 20110121761 | SYNCHRONIZED PHASE-SHIFTED PULSE WIDTH MODULATION SIGNAL GENERATION - A pulse width modulation (PWM) signal generator generates multiple output PWM signals from an input PWM signal. The output PWM signals are synchronized to synchronization events. Each output PWM signal has a duty ratio substantially equal to the duty ratio of the input PWM signal, and each output PWM signal has a fixed phase-shift in relation to the other output PWM signals. The PWM signal generator samples an input PWM cycle to determine sample parameters representative of its duty ratio. The sample parameters are then used to generate a corresponding output PWM cycle for each of the output PWM signals. In response to a synchronization event, the PWM signal generator prematurely terminates the current PWM cycle and initiates the next PWM cycle while ensuring that the portion of the current output PWM cycle completed by the leading output PWM signal up to the point of the premature termination is replicated for the corresponding output PWM cycles of the other non-leading output PWM signals. | 05-26-2011 |
