Patent Grant
8537099
The present invention relates to power electronics integrated circuitry, in particular, to systems and methods for integration of power management circuitry and timing controller for LCD applications.
The use of active liquid-crystal display (LCD) panels has increased at a fast pace in the last decade. The panel's size extends from only a couple of inches for a handheld device to tens of inches for a HDTV display. The multimedia phenomenon has become part of everybody's daily life, and with that there is need for innovative displays able to deliver the content to various market segments. Generally, an active matrix flat panel display includes a LCD screen containing a plurality of pixels for displaying images, a backlight, a timing controller for the driving circuits to control display signals, and a power management circuitry for the backlight. The LCD panel displays the images by controlling the luminance of each pixel according to given display information. Each pixel of the active light-emitting device includes a light-emitting element, a driving transistor for driving it, a switching transistor for applying a data voltage to the driving transistor, and a capacitor for storing the data voltage. The driving transistor outputs a current which has a magnitude depending on the data voltage. The light-emitting device emits light having intensity depending on the output current of the driving transistor, thereby displaying images.
Optimizing power consumption of an LCD display has been a long-standing consideration in the design of LCD electronic products, especially for battery dependent mobile display devices. Proper management of power consumption in display panels is imperative for achieving energy efficiency and better battery life.
Therefore, there is a need to develop a truly integrated time controlled power delivery system for LCD panels.
Therefore, there is a need to develop a truly integrated time controlled power delivery system for LCD panels. Consistent with some disclosed embodiments, an integrated circuit voltage supply for liquid crystal display (LCD) is disclosed. In some embodiments, an IC voltage supply for an LCD can include a DC voltage regulator coupled between a positive voltage and a negative voltage, the DC regulator receiving a reference voltage and a feedback voltage and providing an output voltage; a resistor network that includes a plurality of parallel branches, each branch having at least one resistor and one node, coupled to the output voltage of the DC voltage regulator; an LCD module coupled to each of the nodes of each parallel branch; and a plurality of diodes each disposed between the node of each branch and a common feedback diode, the common feedback diode coupled to provide the reference voltage, wherein the DC voltage regulator keeps the feedback voltage from each LCD module not lower than the reference voltage independently of each module's consumption of current.
Consistent with the disclosed embodiments, an IC multiple voltage supply system for LCD is described, the multiple voltage supply comprises a timing controller controlling image data scanning timing on LCD; a digital-to-analog converter (DAC) outputting a plurality of reference voltages; a plurality of IC voltage supplies, each IC voltage supply including a DC voltage regulator having one reference voltage input from the DAC reference voltages and a feedback voltage input; a positive voltage pin and a negative voltage pin providing power to the DC voltage regulator; a network of resistors comprising a plurality of parallel branches, each branch having at least one resistor and one node; a plurality of LCD modules supported by the DC voltage regulator, each module connecting to the node of each parallel branch; a plurality of diodes each formed between the node of one module and a feedback diode; and the feedback diode connected to the feedback voltage input of the DC voltage regulator, wherein the DC voltage regulator keeps the voltage for each LCD module not lower than the reference voltage, regardless of each module's consumption of current.
Consistent with the disclosed embodiments, a method of managing a voltage supply for an LCD display is disclosed. The method includes: providing a DC voltage regulator; supplying a reference voltage input signal to the first input terminal of the DC voltage regulator; connecting a plurality of LCD modules in parallel on the output of the DC voltage regulator; and connecting a plurality of diodes each between at least one LCD module and the second input terminal of the DC voltage regulator, wherein the diodes provide a feedback voltage input for the DC voltage regulator.
Consistent with the disclosed embodiments, a method of managing a multiple voltage supply for an LCD display includes: providing a timing controller and outputting to a digital-analog-converter (DAC); generating a plurality of reference voltage signals from the DAC; providing a plurality of DC voltage regulators, each DC voltage regulator comprising; applying one of the plurality of reference voltage signals to a first input terminal of the DC voltage regulator; connecting a plurality of LCD modules in parallel to the output of the DC voltage regulator; and connecting a plurality of diodes each between at least one LCD module and a second input terminal of the DC voltage regulator, wherein the diodes provide a feedback voltage input for the DC voltage regulator.
These and other embodiments are further discussed below with respect to the following figures.
Some embodiments of the present invention will be described more fully below with reference to the accompanying drawings. This invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein.
In the following description, specific details are set forth describing some embodiments of the present invention. It will be apparent, however, to one skilled in the art that some embodiments may be practiced without some or all of these specific details. The specific embodiments disclosed herein are meant to be illustrative but not limiting. One skilled in the art may realize other material that, although not specifically described here, is within the scope and the spirit of this disclosure.
The following description provides details for a thorough understanding of the present invention. Though, several typical circuits are employed to describe certain aspects of the present invention, it should not limit the present invention to these typical circuits. Those circuits which are obvious to those skilled in the art may be omitted although they are implemented in the present invention. In other instances, the well-known circuits may be shown in block diagram form in order not to obscure the present invention in unnecessary detail.
A backlight such as backlight 114 is a form of illumination used in LCD systems such as system 100. Backlight 114 illuminates LCD panel 113 from the side or back of the display panel, unlike frontlights which are placed in front of a LCD panel. Backlights such as backlight 114 are often used in monitor displays or laptop displays to produce light in a manner similar to a CRT display. More recently, light-emitting-diodes are applied as backlights for mobile devices, such as handheld PCs, laptops, or cell phones.
Simple types of LCD displays are built without an internal light source, requiring external light sources to convey the display image to the user. Modern LCD screens, however, typically include an internal light source. Such LCD screens consist of several layers. Backlight 114 is usually the first layer from the back. In order to create screen images, backlight 114 can include a mechanism to regulate the light intensity of the screen's pixels. For this purpose, timed light valves that vary the amount of light reaching the target by blocking its passage in some way can be used. The most common such element is a polarizing filter to polarize light from the source in one of two transverse directions and then to pass it through a switching polarizing filter, to block the path of undesirable light.
As shown in
Pulse-width modulation (PWM) is a very efficient way of providing intermediate amounts of electrical power between fully-on and fully-off. As comparison, a simple power switch with a typical power source provides full power only when switched on. PWM works well with digital controls, which can easily set the needed duty cycles because of their on/off nature. PWM can be used to reduce the total amount of power delivered to a load without losses normally incurred when a power source is limited by resistive means. This is because the average power delivered is proportional to the modulation duty cycle. With a sufficiently high modulation rate, passive electronic filters can be used to smooth the pulse train and recover an average analog waveform. PWM is also often used to control the supply of electrical power to another device such as in brightness control of light sources and in many other power electronics applications.
However, in a standard LCD panel, the interaction between the discrete Timing Controller 120 and PMIC 130 is generally limited to discrete handshakes, such as an enable signal, and for example, the LED dimming control is often provided by a PWM signal. Therefore, in a conventional LCD panel, image timing control and panel illumination power management are integrated as discrete circuits, leaving the system bulky and energy inefficient.
A more efficient integration would be an integration of these two functions, power management and timing controller, in a single-chip solution. When integrated with the PMIC, the timing controller 120 is able to dynamically adjust its power supply based on a number of system inputs on the same chip, improving the overall performance of the LCD system. The present invention discloses a method for the timing controller to dynamically adjust its power supply based on system inputs when integrated with the PMIC.
In
In
DC-DC regulator 320 can be a linear voltage regulator or a switching voltage regulator. A voltage regulator is an electrical regulator designed to automatically maintain a constant voltage level. All active modern electronic voltage regulators operate by comparing the actual output voltage to some internal fixed reference voltage. Any difference is amplified and used to control the regulation element in such a way as to reduce the voltage error. Active regulators, including linear and switched regulators, employ at least one active (amplifying) component such as a transistor or operational amplifier. A linear regulator maintains the desired output voltage by dissipating excess power in ohmic losses (e.g., in a resistor or in the collector-emitter region of a pass transistor in its active mode). A linear regulator regulates either output voltage or current by dissipating the excess electric power in the form of heat, and hence its maximum power efficiency is voltage-out/voltage-in since the volt difference is wasted. In contrast, a switched-mode power supply regulates either output voltage or current by switching ideal storage elements, like inductors and capacitors, into and out of different electrical configurations. Ideal switching elements (e.g., transistors operated outside of their active mode) have no resistance when “closed” and carry no current when “open”, and so the converters can theoretically operate with 100% efficiency, i.e. all input power is delivered to the load; no power is wasted as dissipated heat. The duty cycle of the switch sets how much charge is transferred to the load. This is controlled by a similar feedback mechanism as in a linear regulator. Switching regulators are also able to generate output voltages which are higher than the input, or of opposite polarity—something not possible with a linear design. Switching regulators are used as replacements for the linear regulators when higher efficiency, smaller size or lighter weight is required. Therefore, switched regulators have found broad applications in personal computers, laptops and mobile device chargers.
The present invention applies to any type of voltage conversion including but not limited to switching and linear regulators. The timing controller 300 controls several LCD modules represented in
A Node point in each branch is located between the module and its closest resistor. For example, Node 332 is set between R1331 and Module 1340, Node 335 is set between R2334 and Module 2350, and Node 339 is set between Rn 338 and Module n 360. Resistors 331, 333, 334, 337, and 338 can be made of elemental Ohmic resistors or can be formed from parasitic metal resistances associated with process metal layers at the integrated circuits chip level. The voltage dropout across each Ohmic resistor or a layer of parasitic metal resistance is proportional to the current consumed by each relevant module. The current amount in each module varies according to the timing controller mode of operation; therefore some modules may actually be supplied with a voltage less than required if the DC-DC regulator 320 utilizes only one feedback point.
A multiple feedback system is formed of a number of diodes D1-Dn 341, 351, . . . , 361 and a reference diode Dref 366, coupled together at the same terminal, for example, the anode as shown in
System 400 shown in
A state machine, also called a finite-state machine or finite-state automaton, is a mathematical abstraction or a behavior model that is composed of a finite number of states, forming a bit number. A state machine is often used to design digital logic or computer programs, to solve a large number of problems, among which electronic design automation, communication protocol design, parsing and other engineering applications. In a digital circuit, a state machine can be built using a programmable logic device, a programmable logic controller, logic gates and flip flops or relays.
Power management systems in diagram 400 of
Each power grid 430 or 479 includes several LCD modules. The first power grid 430 includes Module 11440, Module 12450, through Module 1n 460. Each of modules 450 through 460 is powered by the supply voltage VDD12425 through a power grid PM1430 represented by resistors R1431, R2434, R12433, through resistor Rn 438 and Rmn 437, which form a number of parallel resistance branches. Each branch supports one module. For example, resistor R1431 and Module 11440 form the first branch, R2434, R12433, and Module 12440 form the second branch, resistors Rmn 437, Rn 438, and Module in 460 form the nth branch. A Node point in each branch is located between the module and its closes resistor. For example, Node 432 is set between R1431 and Module 1440, Node 435 is set between R2434 and Module 2450, and Node 439 is set between Rn 438 and Module n 460. Resistors 431, 433, 434, 437, and 438 can be made of elemental Ohm resistors or can be formed from parasitic metal resistances associated with the process metal layers. The voltage dropout across each elemental Ohmic resistor or parasitic metal resistance is proportional to the current consumed by each relevant module. A multiple feedback system is formed of a number of diodes D1-Dn 441, 451, . . . , 461 and a reference diode Dref 466, coupled together at the same terminal, for example, the anode. The other terminals of diodes D1-Dn 441, 451, . . . , 461 each couple to the node points in each branch. For example, the cathode of diode D1441 is coupled to Node 1432, the cathode of diode D2451 is coupled to Node 2435, and the cathode of diode Dn 461 is coupled to Node n 439. The anodes of the diodes are coupled to the positive power rail VDD1421 and the cathode of the reference diode Dref 466 is coupled to a feedback voltage signal FBB 424, which is used as the feedback voltage input to the DC-DC regulator. Diodes are biased through I1427 and I2426 such that the voltage at node 1432, node 2435, through node n 439 is no less than the reference voltage Vref1423. The feedback voltage FBB 1424 always follows the lowest node voltage among all node points. The DC-DC regulator 420 dynamically adjusts its output voltage VDD12425 to make sure that the lowest node voltage among all branches, therefore the feedback signal FBB1424, is not lower than the internally fixed reference voltage Vref1423, regardless of the current consumption of each module. The currents I1427 and I2426 can be in any relationship for example, I2=2×I1 if all diodes are of the same type and size. Thus, power grid PM1430 can adjust its power supply VDD12425 on the fly according to an algorithm based on the modes of operation. A stand-by state for this system 430 is determined by the Timing Controller State Machine 410 and enabled by the converted reference voltage Vref1423, therefore the power supply voltage VDD12425 is adjust to a minimum to reduce the power consumption.
The second power managed system, formed by DC-DC regulator 470 and power grid PM2479, functions similarly to the first power managed system, formed by DC-DC regulator 420 and power grid PM1430. Second power grid 479 includes Module 21470, Module 22480, through Module 2n 490. Each module is powered by the supply voltage VDD12475 through a power grid PM2430 represented by resistors R1481, R2484, R12483, through resistor Rn 488 and Rmn 487, which form a number of parallel resistance branches. Each branch supports one module. For example, resistors R1481 and Module 21470 forms the first branch, R2484, R12483, and Module 22480 form the second branch, resistors Rmn 487, Rn 488, and Module 2n 490 form the nth branch. A Node point in each branch is located between the module and its closes resistor. For example, Node 482 is set between R1481 and Module 21470, Node 485 is set between R2484 and Module 22480, and Node 489 is set between Rn 488 and Module 2n 490. Resistors 481, 483, 484, 487, and 488 can be elemental Ohm resistors or can be formed as parasitic metal resistances associated with the process metal layers. The voltage dropout across each elemental Ohmic resistor or parasitic metal resistance is proportional to the current consumed by each relevant module. A multiple feedback system is formed of a number of diodes D1-Dn 491, 493, . . . , 495 and a reference diode Dref 496, coupled together at the same terminal, for example, the anode. The other terminals of diodes D1-Dn 491, 493, . . . , 495 each are coupled to the node points in each branch. For example, the cathode of diode D1491 is coupled to Node 1482, the cathode of diode D2493 is coupled to Node 2485, and the cathode of diode Dn 495 is coupled to Node n 489. The anodes of the diodes are coupled to the positive power rail VDD1421 and the cathode of the reference diode Dref 496 is coupled to a feedback voltage signal FBB 474, which is used as the feedback voltage input to the DC-DC regulator. Diodes are biased through I1477 and I2476 such that the voltage at node 1482, node 2485, through node n 489 is no less than the reference voltage Vref2473. The feedback voltage FBB2474 always follows the lowest node voltage among all node points. The DC-DC regulator 470 dynamically adjusts its output voltage FDD22475 to make sure that the lowest node voltage among all branches, therefore the feedback signal FBB2474, is not lower than the internally fixed reference voltage Vref2473, regardless of the current consumption of each module. The currents I1477 and I2476 can be in any relationship for example, I2=2×I1 if all diodes are of same type and size. Thus, power grid PM2479 can adjust its power supply VDD22475 on the fly according to an algorithm based on the modes of operation. A stand-by state for this system 479 is determined by the Timing Controller State Machine 410 and enabled by the converted reference voltage Vref2473, therefore the power supply voltage VDD22475 is adjusted to a minimum to reduce the power consumption.
As discussed above, system 400 can include any number of power managed systems. Each of the power managed systems can be as described above.
The above detailed description of integrated timing controller and voltage supply is provided to illustrate specific embodiments of the present invention and is not intended to be limiting. Numerous variations and modifications within the scope of the present invention are possible. The present invention is set forth in the following claims.
| Number | Name | Date | Kind |
|---|---|---|---|
| 20070097067 | Yoo | May 2007 | A1 |
| 20070195025 | Korcharz et al. | Aug 2007 | A1 |
| 20100156879 | Hong et al. | Jun 2010 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 20120056864 A1 | Mar 2012 | US |
