JP2007511062A - Method and apparatus for visual enhancement control of light emitting devices - Google Patents

Abstract

Embodiments of the present disclosure provide a method and apparatus for visual enhancement of a liquid crystal display. A microprocessor associated with the visual enhancement module or an embedded microcontroller allows a single inverter to control the illumination of an array of multiple CCFLs. The microcontroller continuously senses the operating current of all lamps and adjusts the illuminance variation of the individual lamps by switching in parallel capacitances that ensure that equal current is applied to each lamp. The microcontroller generates a suitable control signal and executes a digital servo control algorithm that modifies the current to make brightness adjustments.

Description

[Cross-reference of related applications]
This application is a practical modification of US Provisional Application No. 60 / 518,490 filed on November 6, 2003, and a modification of US Provisional Application No. 60 / 445,914 filed on February 6, 2003. International filing date partially continues with co-pending PCT application number PCT / US2004 / 003400 of February 6, 2004.

  Embodiments of the present disclosure generally relate to control of light emitting devices such as cold cathode fluorescent lamps and light emitting diodes. Specifically, the embodiment of the present disclosure relates to backlight control of a liquid crystal display.

  Cold cathode fluorescent lamps (CCFLs) are now commonly used as backlights for liquid crystal displays in notebooks, laptop computer monitors, car navigation displays, POS terminals, and medical devices. CCFLs have been rapidly introduced for use in notebook computers and various portable electronic backlights because of their superior lighting and cost efficiency. These applications generally require uniform display brightness and illuminance.

  Usually, the liquid crystal material is separated from the CCFL backlight device by the diffusion plate layer, and polarizes the light of each display pixel. Since this lamp requires a high alternating current (AC) operating voltage, a DC / AC inverter is required to drive the CCFL. As the size of the LCD panel increases, multiple lamps are required to provide the necessary illuminance. Therefore, an efficient inverter is required to drive multiple CCFL arrays.

  The intensity of the illumination is determined by the operating current applied to the CCFL by the inverter. In a conventional multiple lamp panel array, each lamp is driven by its own high-cost inverter, or one shared inverter has a current determined by the total current of all lamps set in advance to the operating current of all lamps. Must be driven by setting

  However, the brightness and intensity of each lamp varies with age, replacement, and inherent manufacturing variations. If the same reference current is applied to each lamp without adjusting the fluctuations of the individual lamps, a difference occurs in the illuminance of each lamp. Variations in lighting altitude cause the display of visible non-diffused lines. The conventional single inverter circuit cannot individually detect and adjust the operating current of each lamp in order to make the illuminance uniform across the plurality of lamp array display panels.

  As the market lowered the cost of CCFLs, the use of multiple lamp array display panels expanded as a result, increasing demand for inverter quality, economy, and functionality. Conventional backlights for LCD devices have insufficient uniformity of illuminance. Thus, there is a need for an economical inverter technology that can individually detect and adjust the current applied to the CCFL array in a multiple lamp LCD display.

  Embodiments disclosed herein address the above needs by providing a method and apparatus for a visual enhancement control module with a single CCFL inverter capable of maintaining individual current settings in a multiple lamp array. It is.

  A visual enhancement control module that uses a switching circuit includes a rectifier bridge, a transistor switch, and a microcontroller interface connected in series with the CCFL. Alternatively, a switched capacitor circuit is connected in series with the CCFL. A microprocessor executes servo control software for illuminance feedback information used to sense current and drive the current control circuit. The system software monitors the current and voltage across the lamps and determines the electrical capacity required for each lamp to obtain the amount of current. The visual enhancement control module comprises a single inverter that drives multiple lamp arrays while maintaining accurate control of the current and illuminance of each lamp.

  Accordingly, in one form, a current control method for multiple light emitting devices is disclosed. The method detects individual output information of each light emitting device in a multi-device array, and generates an individual current control signal used to adjust an operating current applied to each device through an individual inverter according to the current control signal. Process the output information for this purpose.

  In another form, a current control device for multiple light emitting devices is disclosed. The apparatus includes a sensor that detects individual output information of each light-emitting device in a multi-device array, a microcontroller that processes output information for generating individual current control signals for each device, a current equalization circuit, and Includes server control system software to adjust the operating current applied to each device through a single inverter according to the current control signal.

  As used herein, the term “typical” means “as an example, instance, or illustration”. Any case described herein as "typical" is not necessarily to be construed as preferred or advantageous over other cases.

  The disclosed case defines a method and apparatus for visual enhancement of a liquid crystal display. An embedded microprocessor associated with the macro processor or enhancement circuit module allows a single inverter to control the illumination of an array of multiple CCFLs. The microcontroller continuously senses the operating current of all the lamps, switches the capacitance in parallel, adjusts the lighting variation of the individual lamps, and ensures that an even current is applied to each lamp. The microcontroller generates a suitable control signal and executes a digital servo control algorithm that changes the current to make brightness adjustments.

  FIG. 1 represents a conventional CCFL control circuit 100 that requires an inverter 120 for each lamp 104 in the LCD backlight array. The fluorescent lamp 104 exhibits significant manufacturing variability. The lamp 104 is driven by an inverter control circuit 120 including a primary side circuit 106 and a secondary side circuit 108. The primary circuit 106 manages high current and low voltage and connects to the primary side of the transformer 110. Secondary circuit 108 is connected to the secondary of transformer 112, ballast capacitor 114, fluorescent lamp 104, current sensor 116, and potentiometer 118 to regulate the lamp current.

  When more than one lamp is driven by the same inverter 120, the current through each lamp is different because of lamp variation. As a result, the brightness of the entire LCD panel becomes non-uniform. The portion directly connected to the lamp of the inverter 120 (secondary voltage of the transformer 112) is a high voltage circuit. Because the magnitude of the voltage is related, the circuit 100 cannot be easily controlled to change the power applied to the lamp 104.

  Prior solutions solved the problem by using a separate inverter 120 for each lamp 104. By using an individual inverter 120 for each lamp 104, it is possible to adjust the current of the individual lamp with the potentiometer 118. A current sense signal is used to drive the switching circuit of the inverter 120 driven at low voltage (primary of the transformer). Conventional solutions are very costly because a plurality of inverters 120 are used in the LCD display.

  FIG. 2 shows the variation of the characteristic current with respect to the voltage 200 of the plurality of CCFLs driven by the conventional control circuit shown in FIG. Each lamp requires a threshold voltage (201, 202) to ionize the gas contained in the lamp and achieve a light emission output. As the lamp reaches the threshold voltage, each lamp exhibits a different voltage-current relationship as indicated by the operating voltage curve. (203,204)

  FIG. 3 shows the variation in characteristic current with respect to the conventional voltage when two CCFLs are driven by the same inverter. Each curve (305, 306) is different after the threshold voltage is obtained. If the target lamp current is equal to the nominal operating current of IOP 301 and the nominal sustaining voltage is equal to VSUS 302, the voltage applied to lamp 1 is to obtain the voltage across lamp 1 of VSUS minus the delta of V1 303 , It must be reduced by the delta of V1. Similarly, the voltage applied to the lamp 2 voltage must be reduced by the V2 delta in order to obtain the VSUS overall lamp 2 voltage minus the V2 304 delta. The overall lamp voltage reduction results in both lamps having the same IOP nominal operating current, resulting in uniform illumination.

  FIG. 4 is a block diagram illustrating a novel visual enhancement closed loop control system of an N CCFL401 array backlight, in accordance with one embodiment of the present invention.

  The microcontroller 402 executes one or more software modules that constitute program instructions for generating a current control signal 402 that is input from a non-volatile memory to a field programmable gate array (FPGA) 406. Software modules can be used in the form of microcontrollers, RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disks, removable disks, CD-ROMs or any other storage medium known in the art can do.

  The FPGA 406 delivers the current control signal 402 to the visual enhancement control module 408 with the individual CCF 401 assigned to the microcontroller 402. A visual enhancement control module 408 (detailed in FIGS. 6 and 7) drives each CCFL 401 with the amount of current specified in the microcontroller. The current sensor 410 continuously detects the actual individual lamp current for feedback to the microcontroller 402. The individual lamp current output by current sensor 410 is multiplexed by analog multiplexer 412 for input to microcontroller 402.

  The servo control algorithm software module executed by the microcontroller 402 continuously uses the multiplexed feedback information to adjust the settings of the visual enhancement control module 408 by the current sensor 410. These setting adjustments maintain individual lamp currents by continuously compensating for current variations due to age, replacement, inherent manufacturing variations, and temperature variations. The software module executed by the microcontroller 402 controls and coordinates the operation of the inverter 414 that simultaneously controls the secondary voltage output of the inverter 414 (see element 112 in FIG. 1). The secondary voltage output of the inverter is applied to CCFL 401.

  In various embodiments, any combination of microcontroller 402, inverter 414, memory, FPGA 406, multiplexer 412, current sensor 410 and control module 408 are integrated into a printed (PC) board or application specific integrated circuit (ASIC). can do. Alternatively, the microcontroller 402, FPGA 406, and multiplexer 412 can be integrated into the inverter assembly 414. The microcontroller 402, FPGA 406 function, and multiplexer 412 can also be integrated into the same or another single IC. Further, one or more control modules 408 can be integrated into a single integrated circuit that can also include a current sensor 410 or a light sensor (see FIG. 5, element 510).

  A modular graphical user interface supported by one or more software executed on the microcontroller 402 can be used at an initial current setting or optionally to later override the servo algorithm maintenance settings.

  FIG. 5 illustrates a multi-CCFL visual enhancement control system according to another embodiment of the present invention. The alternative visual enhancement control system 500 embodied in FIG. 5 uses one or more light sensors 510 rather than current sensors (see FIG. 4, element 410) to provide feedback information to the microcontroller 502. The servo control algorithm software module executed on the microcontroller 502 continuously uses the multiplexed feedback information provided by the light sensor 510 to adjust the visual enhancement control module settings. These setting adjustments maintain desired individual brightness levels by continuously compensating for variations due to age, replacement, inherent manufacturing variability, and temperature.

  As detailed in FIG. 4, the visual enhancement control module 508 sets the current of the CCFL 501. The amount of current applied to each CCFL 501 through the associated visual enhancement control module 508 is determined by a control signal from the logic block 506. The logic block 506 performs the same function as the FFPGA (see element 404 in FIG. 4). Logic block 506, microcontroller 502 and analog multiplexer 512 may be part of a single integrated digital controller circuit.

  Feedback to the visual enhancement loop control system 500 is provided by one or more light sensors 510. The light sensor 510 detects the amount of light output by the CCFL 501. The light sensor 510 generates a light output feedback signal for input to the analog multiplexer 512. The analog multiplexer 512 passes the light sensor feedback signal to an analog / digital (A / D) converter that can be built into the microcontroller 502. A closed loop servo control algorithm software module executed by the microcontroller 502 continuously maintains a predetermined brightness set point for each CCFL 501. As the CCFL 501 ages, the output accuracy is advantageously improved by determining the luminance output level with the light sensor 510.

  In addition to maintaining the individual current settings of the multiple lamp arrays at a constant brightness, embodiments of the visual enhancement control system described above can be operated to generate the visual effects of the backlight lighting device. The visual enhancement control system can be used to increase or decrease the light intensity of selected portions of the display. For example, a 3D effect can be created by increasing the light output level of the display portion of the video material where the explosion occurs, where the explosion occurs. Similarly, visual effects can be created on materials enhanced by shadows, such as dark alley scenes. Visual effects can be created by the disclosed control system using a software module that changes the amount of light output from the backlight device at a particular location on the display.

  FIG. 6 details the visual enhancement control module represented in the block diagrams of FIGS. 4 and 5 according to one embodiment of the present invention. The visual enhancement control module 600 adjusts the current applied to the individual CCFLs according to control signals generated externally by a microcontroller (not shown). Inputs 1 602 and 2 604 receive current control signals sent from the microcontroller by the system controller FPGA or logic block (not shown). The control signal can comprise a direct current (DC) voltage or a pulse width modulation (PWM) signal. The value of the control signal determines the amount of current through each CCFL of the multiple lamp array.

  The control signal is applied to an optical or photovoltaic device U1 606 that converts the control signal into an isolated control signal. Resistors R2 612 and R3 614 set a specified current proportional to the control signal applied to U1 606. The optical isolator sends a control signal to the secondary side of U1 610.

  If U1 is a photovoltaic inverter, the light generated by U1's output LED 626 is converted to a voltage by the secondary side of U1 610. Capacitor C1 618 filters the output of U1 to generate an isolated control signal corresponding to transistor Q1 622. Resistor R1 620 sets the impedance at the base of Q1 622 to a value that allows stable operation of Q1 622. Transistor Q1 622 can operate in switch mode or linear mode as required by the CCFL current response. A current control bridge consisting of diodes D1-D4 624 sends both polarities of alternating current (AC) current through Q1 622 to drive the CCFL.

  The current control signal received in this manner is converted into a proportional light output converted into a voltage, and a current specified by the control signal is generated. The current specified in the control signal is an output to the CCFL.

  FIG. 7 details the visual enhancement control module illustrated in the system block diagrams of FIGS. 4 and 5 in accordance with another embodiment of the present invention. In the alternative visual enhancement control module 700 illustrated in FIG. 7, two or more CCFLs (701, 702) are again driven by a single inverter 703. For simplicity, two typical CCFLs are shown. The visual enhancement control module 700 includes a current control circuit 704 in the CCFL1 701 and a current control circuit 705 in the CCFL2 702. The control circuit (704, 705) comprises a plurality of parallel capacitors 708 coupled by a switch 710. The microprocessor 706 controls the inverter 703. Other values of capacitor 708 can be used to change the current control effect.

  The very small capacitance values required by the CCFL make it difficult to design. The controller (704, 705) of the present invention overcomes these design difficulties by including a microcontroller 706 for executing calibration algorithms stored in non-volatile memory. The microcontroller performs a calibration procedure that measures current through each CCFL (401, 402) with an A / D inverter that can be placed inside the current sensor 712 and microcontroller 706. The microcontroller 706 then closes the appropriate switch 710 to obtain the correct capacitor combination to raise and lower the lamp voltage by the appropriate amount.

  The high voltage required by CCLF introduces additional design difficulties. These difficulties make the current control circuit (704, 705) of the present invention because the control circuit (704, 705) requires only a small enough voltage to change the CCFL (401, 402) operating point. Can be overcome as well.

  Since the ramp characteristic curve after reaching the threshold voltage is very steep, the voltage of the entire controller must be only a few hundred volts (see FIGS. 2 and 3). The voltage can be easily handled by readily available capacitor and switch technology (see Supertex Inc high voltage switch part number HV20220). The microcontroller can use PWM to control opening and closing the switch 710. The PWM duty cycle determines the exact capacitance value. This approach allows further fine tuning of the capacitor value.

  The disclosed visual enhancement control system using the disclosed visual control enhancement module provides a CCFL control circuit that is highly cost and performance optimized. All CCFLs in the array can exhibit equal (or specified) brightness and current while driven by the same inverter.

  Those skilled in the art will understand that the order and components of the steps shown in the above figures are not limited. The methods and components can be readily modified without departing from the scope of the disclosed examples by omission or reordering of the illustrated steps and components.

  Accordingly, a new and improved method and apparatus for controlling light emitting appliances in general and, in particular, example cathode trend lamps, is described. Those skilled in the art will appreciate that any of different techniques and techniques can be used to indicate information and signals. For example, data, commands, commands, information, signals, bits, symbols, and chips that may be referred to throughout the above description are voltages, currents, electromagnetic waves, magnetic fields or magnetic particles, optical fields or particles, or combinations thereof Can be represented by

  Those skilled in the art will further recognize that the various illustrative logical blocks, modules, circuits, and algorithm steps associated with the examples disclosed herein can be used as electronic hardware, computer software, or a combination of both. You will recognize. To clearly represent this hardware and software compatibility, various example components, blocks, modules, circuits and steps are generally described above in terms of functionality. Whether such functionality is used in hardware or software depends on the particular application and design constraints imposed on the overall system. Those skilled in the art will use the functions described in different ways for each particular application, but such use decisions should not be construed as departing from the scope of the present invention.

  Various illustrative logical blocks, modules and circuits related to the examples disclosed herein may be general purpose processors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), or It can be used or performed with other programmable logic devices, individual gates or transistor logic, individual hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, it may be any conventional processor, controller, microcontroller, or state machine. The processor can also be used as a combination of computer devices, i.e., a DSP and microprocessor combination, multiple microprocessors, one or more microprocessors connected to a DSP core, or any other such configuration. .

  The method or algorithm steps associated with the examples disclosed herein can be directly integrated into hardware, software modules executed by a processor, or a combination of the two. The software module can be used in the form of RAM memory, flash memory, ROM memory, EPROM memory, EEPROM memory, registers, hard disk, removable disk, CD-ROM or any other storage medium known in the art. . A typical storage medium is coupled to the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium may be integral to the processor. The processor and the storage medium can be provided in the ASIC. In the alternative, the processor and the storage medium may be provided as separate components.

  The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments without departing from the spirit and scope of the invention. can do. Accordingly, the present invention is not intended to be limited to the embodiments described herein but is to be accorded the widest scope consistent with the principles and new functions disclosed herein.

FIG. 1 shows a conventional inverter circuit for driving a single CCFL. FIG. 2 shows the conventional variation of characteristic current versus voltage of multiple CCFLs driven by a conventional individual inverter. FIG. 3 shows the conventional variation of characteristic current versus voltage of multiple CCFLs driven by a conventional shared inverter. FIG. 4 illustrates a visually enhanced closed loop control system for multiple CCFLs, according to one embodiment of the present invention. FIG. 5 illustrates a visual enhancement control system for multiple CCFLs according to another embodiment of the present invention. FIG. 6 illustrates a visual enhancement control module according to one embodiment of the present invention. FIG. 7 illustrates a visual enhancement control module according to another embodiment of the present invention.

Claims (21)

Detect the individual output information of each light emitting device of the multiple device array,
Process output information for generating individual current control signals for each light emitting device,
Adjust the operating current applied to each issuing device through a single inverter according to the current control signal,
A current control method for a plurality of light emitting devices.   The current control method for a plurality of light-emitting devices according to claim 1, wherein the light-emitting device is a cold cathode fluorescent lamp.   The method of claim 1, wherein the inverter is replaced with a driver, and the light emitting device is a light emitting diode. A sensor for detecting individual output information of each light emitting device of the multiple device array;
A microcontroller that processes output information for generating individual current control signals for each light emitting device;
Current control circuit and server control system software for adjusting the individual operating current applied to each light emitting device through a single inverter according to individual current control;
A current control device for a plurality of light emitting devices.   The current control device for a plurality of light-emitting devices according to claim 4, wherein the sensor is a current sensor.   The current control device for a plurality of light-emitting devices according to claim 4, wherein the sensor is a light sensor.   The current control device for a plurality of light emitting devices according to claim 4, wherein the light emitting device is a cold cathode fluorescent lamp.   The current control device for a plurality of light emitting devices according to claim 4, wherein the inverter is replaced with a driver, and the light emitting device is a light emitting diode. Receiving a current control signal from the microcontroller,
Separating the voltage control signal from the current control signal,
Filter the voltage control signal to generate a separate voltage control signal compatible with the transistor,
Set the impedance at the base of the transistor,
Operate the transistor according to the current response required by the light emitting device,
In addition to adding a current control signal to the transistor to generate an alternative current specified in the current control signal,
Passing both polarities of an alternative current through the light emitting device,
A method of changing the illuminance of multiple light emitting devices.   The method of changing illuminance of a plurality of light emitting devices according to claim 9, wherein the transistor operates in a linear mode.   The method for changing the illuminance of a plurality of light emitting devices according to claim 9, wherein the transistor operates in a switch mode.   The method for changing the illuminance of a plurality of light emitting devices according to claim 9, wherein the light emitting device is a cold cathode trend lamp. An isolator that receives a current control signal from the microcontroller and separates the voltage control signal from the current control signal;
A capacitor that filters the voltage control signal to generate an isolated voltage control signal compatible with the transistor;
A resistor to set the impedance at the base of the transistor;
A transistor for generating an alternative current specified by the current control signal from the voltage control signal;
A diode bridge that passes both electrodes of the alternative current through the light emitting device;
A circuit for correcting the illuminance of a light emitting device equipped with   The circuit for correcting the illuminance of a light-emitting device according to claim 13, wherein the isolator is an optical isolator.   14. The circuit for correcting the illuminance of a light emitting device according to claim 13, wherein the isolator is a photovoltaic converter that converts a current control signal into a proportional light output that is then converted into a voltage. Detects individual output information of individual light emitting devices in multiple device arrays,
Process the output information to generate the individual current control signal to the light emitting device,
In addition to adding a current control signal to multiple switches coupled to the parallel capacitor to generate an operating current specified in the current control signal,
Drive the light emitting device with operating current,
A method for correcting the illuminance of a light emitting device.   The method for correcting the illuminance of a light emitting device according to claim 16, wherein the light emitting device is a cold cathode fluorescent lamp.   The method for correcting the illuminance of a light emitting device according to claim 16, wherein the light emitting device is a light emitting diode. A sensor for detecting individual output information of individual light emitting devices of a multi-device array;
A microcontroller that processes the output information to generate individual current control signals to the light emitting devices;
A switch coupled to the parallel capacitor to generate an operating current specified in the current control signal;
A light emitting device driven by operating power;
A circuit for correcting the illuminance of a light emitting device comprising   The circuit for correcting the illuminance of the light emitting device according to claim 19, wherein the light emitting device is a cold cathode fluorescent lamp.   The circuit for correcting the illuminance of the light emitting device according to claim 19, wherein the light emitting device is a light emitting diode.

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