WO2002021500A1

WO2002021500A1 - Single liquid crystal display with dynamic scan and split backlights and method of using same

Info

Publication number: WO2002021500A1
Application number: PCT/US2001/026759
Authority: WO
Inventors: Franky So; Thomas Swirbel
Original assignee: Motorola Inc.
Priority date: 2000-09-05
Filing date: 2001-08-28
Publication date: 2002-03-14
Also published as: AU2001286836A1

Abstract

An electronic hand held device (200), such as a cellular phone, a pager, and personal digital assistant, includes display (202, 204) and a display lighting system that operate in two modes. In a first mode, the display (210) shows limited text such as for phone numbers or directory listings which utilizes only a few lines of text. In a second mode, display (210) may be used as an Internet browser display that utilizes a larger display area to show a full page of information such as including text and graphics. The device conserves power consumption by lighting, or backlighting, the display according to the two different modes.

Description

SINGLE LIQUID CRYSTAL DISPLAY

WITH DYNAMIC SCAN AND SPLIT BACKLIGHTS

AND METHOD OF USING SAME

Field Of The Invention

This invention generally relates to handheld devices and wireless communication devices that display information for users. In particular, this invention relates to improvements in power savings for the aforementioned devices with displays and display lighting systems.

Background Art

Moderately complex liquid crystal displays capable of displaying graphics on a display panel that include either alphanumeric characters or icon segments, or both, are common place today in a variety of electronic devices. The graphics are formed from pixels. The information as to the state of each pixel is hereinafter referred to as the pixel information. Such liquid crystal displays typically have orthogonal electrodes on the front and back planes of the display panel, wherein the pixels are generated in one of two states at each crossing of the front and back electrodes. The back plane electrodes are typically driven with a set of scanning signals, each of which is a different periodic signal. The waveforms of the scanning signals are independent of the pixel information to be displayed. The front plane electrodes are typically driven with a set of information signals. The information signal of each front electrode is dependent on the pixel information to be displayed at the crossings of the front electrode and the back electrodes, and the waveform of each information signal is not necessarily different from the waveforms of other information signals. In particular, when the pixel information to be displayed on any two front plane electrodes is the same, the information signals for the two electrodes are the same.

In a battery operated electronic device such as a pager or cellular phone, it is highly desirable to achieve the smallest possible average power drain, because the average power drain determines the battery life of the pager. Typical pagers, for example, have a standby mode, which is a low power mode during which the user is not manipulating controls on the pager and during which the pager is awaiting a message from a paging system. The average power drain during the standby mode often dominates in the determination of the average power drain, and thus often dominates the determination of the battery life. When a battery operated electronic device incorporates such a moderately complex liquid crystal display, the power drain of the display and the display lighting circuits can be a significant portion of the standby power drain.

FIG. 1 (100) is a telecommunication device like a call radio found in the prior art within which the invention may be practiced. As is known to one of ordinary skill in the art, a display driver can selectively energize a portion of the LCD display as described in US Patent No. 5,859,625, the teachings of which are herein incorporated by reference. The selective call radio (100) includes an antenna (116) for intercepting an outbound radio signal. The antenna (116) is coupled to a conventional receiver (104) wherein the intercepted signal (118) is received. Receiving includes filtering to remove undesirable energy at off channel frequencies, amplification of the filtered signal, frequency conversion of the signal (118), and demodulation of the signal (118) in a conventional manner. The receiver (104) thereby generates a demodulated signal that is coupled to a processing system (120). The processing system (120) is coupled to a graphics display (114), an alert (124), and a set of user controls (122). The processing system (120) comprises a microprocessor (108) which is coupled to an analog to digital converter (ADC 106), a random access memory (RAM 110), an electrically erasable read only memory (128) and a read only memory (ROM 112). The demodulated signal (126) is coupled to the ADC (106), which converts the demodulated signal (126) from an analog signal to a digital signal in a conventional manner, for processing by the processing system (120). A bit recovery function converts the demodulated digital signal to binary data in a conventional manner. A message processor function decodes outbound words from the bits and processes an outbound message when an address received in the address field of the outbound signaling protocol matches an embedded address stored in the EEPROM (128) in a manner well known to one of ordinary skill in the art for a selective call radio (100). An outbound message that has been determined to be for the selective call radio (100) by address matching is processed by the message processor function according to the contents of the outbound message and according to modes set by manipulation of the set of user controls (122), in a conventional manner. An alert signal is typically generated when an outbound message includes user information. The alert signal is coupled to the alert device (124), which is typically either an audible or a silent alerting component.

When the outbound message includes alphanumeric or graphic information, the information is displayed on the graphics display (114) in a conventional manner by a display function at a time determined by manipulation of the set of user controls (122). When the user selects a standby mode or when the user does not manipulate any controls for a predetermined duration, the processing system (120) changes the selective call radio (100) to the standby mode, in which the alphanumeric portion of the graphics display (114) is turned "off" and becomes blank. A row of icons remains active while the selective call radio (100) is in the standby mode. The icons show mode information, such as whether the alert is set for silent or audible operation, whether there are messages stored in the selective call radio (100), a low battery indication, or the equivalent. The selective call radio (100) is similar to a MEMO EXPRESS model radio, manufactured by Motorola, Inc., of Schaumburg, HI. All portions of the selective call radio (100) are conventional, except for the graphics display (114) and the display control functions and pixel information generated by the processing system (120) and coupled to the graphics display (114). The display panel LCD panel (114) is designed using conventional techniques and technology. The microprocessor organizes and stores graphic information that can be displayed on the LCD panel (114). The graphic information is encoded information which is a combination of alphanumeric (or ideographic) and icon information, such as ASCII (American Standard for Coded Information Interchange) encoded characters and binary encoded icon states. The processor converts the encoded information into pixel information, comprising bits organized into bytes, each bit representing a state of a pixel on the LCD panel (114), in a manner well known to one of ordinary skill in the art. i this invention, the pixel can be a dot within an alphanumeric/ideographic portion of the LCD panel (114), or an icon or an icon segment within an icon portion of the LCD panel (114).

Further, hand held devices such as cell phones, pagers, and personal digital assistants, often incorporate displays that operate in two modes. For example, a cell phone display would show simple text for phone numbers or directory listings which requires only a few lines of text. In other instances, the cell phone might be used as an Internet browser which requires a larger display area to show full page text and graphics. Currently, most devices have a single display to meet these requirements for two modes of operation. However, while a single large display is capable of meeting the text, messaging, and graphics requirements, these larger displays have high power consumption because of the high number of scan lines and higher voltage drive schemes. In addition to the display, the display lighting circuits, such as the display backlight, is usually ON when the device is activated. When a large display is used, the backlight is equally as large as the display and if only a few lines of text or single line phone number is going to be shown, backlighting the entire panel is unnecessary and needlessly drains the battery. Therefore, what is needed is a display device and lighting system that reduces power consumption and at the same time permits full text, messaging and browsing requirements.

Brief Description of Drawings

The features of the invention believed to be novel are set forth in the claims. The invention itself, however, may be best understood by reference to the following detailed description of certain exemplary 'embodiments of the invention, taken in conjunction with the accompanying drawings in which:

FIG. 1 is a telecommunication device found in the prior art. FIG. 2 is a liquid crystal displa^ showing sections of a display for different uses. FIG. 3 is a flow diagram that illustrates the invention as practiced in a device utilizing the liquid crystal display of FIG. 2.

Disclosure of the Invention

While this invention is susceptible of embodiment in many different forms, there are shown in the drawings and will herein be described in detail specific embodiments, with the understanding that the present disclosure is to be considered as an example of the principles of the invention and not intended to limit the invention to the specific embodiments shown and described. Further, the terms and words used herein are not to be considered limiting, but rather merely descriptive. In the description below, like reference numbers are used to describe the same, similar, or corresponding parts in the several views of the drawings.

A preferred embodiment of the present invention solves the aforementioned problems with the current art for displays in portable products and increases the battery life of a hand held device by using dynamic scanning of the display panel. The multiplex ratio of a display depends upon the amount of information to be displayed. For example, the display functions in two modes 1) regular phone mode and 2) Internet browser. When the device is used as a phone, only two lines of text (up to 32 rows, for example) is needed and no graphical or gray scale is required. To drive a display in this mode, no more than 9N is required and the power consumption is very low. When the device is used as a browser more line scans (180-240) and gray scale (or color) are required. Under this situation, the display controller dynamically changes the scanning for the entire panel as needed. This mode requires 15-20 volts (N) to drive the display. However, the higher voltage is only needed when the entire display is being used. As a result more than 80% of display panel power savings can be realized; typically 1 millimeter (mW) for the partial panel versus 5 millimeters(mWs) for the entire panel for a reflective display.

To complement the dynamic scanning drive scheme, two sets of backlights are incorporated into the display; one to power the display used in text mode (upper portion of the display) and the other to power the rest of the panel. For example, a white backlight to illuminate a 3" LCD panel to display an internet browser consumes more than 200 mWs of power while a similar backlight to illuminate a 1" panel consumes about 50 mWs, which is a 75% savings in power consumption. A typical cell phone STΝ LCD with three to four lines of text has a power consumption of less than a few millimeters and the backlight (LED or EL) has a power drain of 40-50 mWs. Also, a Personal Data Assistant (PDA) size LCD panel has power consumption of less than a lOmWs while its backlight can consume 150-200 mWs. In general, the backlight power consumption is more than ten times the oower consumption of the LCD panel itself. Therefore, selective use of the backlight in conjunction with the dynamic scanning will result in significant power savings.

To achieve this, it is highly desirable to split the backlight into two parts, one to illuminate the display when the device is functioning as a radio or cell phone, and the other one to illuminate the entire panel when it is functioning as a PDA. This invention utilizes existing driver and lighting, e.g., backlighting, technology. However, it uses new software to control the different display modes of operation. In standby or phone only mode, only a small portion of a display panel is powered and a partial backlight is ON. In browser or Personal Digital Assistant (PDA) mode, the entire panel is driven and the complete backlight is energized.

FIG. 2 (200) is a liquid crystal display (212) showing sections of a display for different uses. The display is broken up into two sections (202, 204) for selective backlighting (214, 216) of the display including electrode front-plane (210) and back-plane (206) drivers. When the microprocessor (208) senses that the device is in a first mode of operation, for example, phone only mode, then only a portion (202, lamp 214) of the backlight (214, 216) is turned ON by the microprocessor. When the microprocessor senses that the display is in browser or Personal Digital Assistant mode of operation, then the entire display panel, including both sections (202, 204), is backlit by the backlights (214, 216). The lighting sources, e.g., backlights (214, 216), may comprise any combination of the following: an electroluminescent panel with a voltage pump (70V), a lamp driven from a power source via a switch like a FET, or an LED with a diffuser lens to spread the light over the entire portion of the panel being illuminated.

FIG. 3 is a flow diagram that illustrates an operational sequence (300) that can be followed by the invention as practiced in connection with the processor controlled liquid crystal display device of FIG. 2 (200). First, a determination (302) is made by a processor as to whether or not a device is in a first mode of operation. If it is in a first mode of operation then a first backlight section, for example, is illuminated (304). Otherwise, the process continues with a determination of whether or not the device is in a second mode of operation (306). If it is in a second mode of operation then the entire backlight is energized (308); otherwise, a determination is made as to whether or not the device is turned OFF (310) or in standby mode. If it is turned OFF or in standby mode then the backlights are turned OFF (312). Later, a particular determination is made as to whether the device is turned OFF or in standby mode (314). If the device is turned OFF then the process ends; otherwise, if it is in a standby mode then a check is made as to whether or not the standby mode has ended (316). If it has ended then the backlighting appropriate to the mode of operation is restored (steps 302-308); otherwise, the process cycles through (steps 310-314) tests to wait for the standby mode to end. It will be appreciated that the present invention will provide the power saving benefits described herein when used in electronic devices other than pagers, including portable electronic devices such as portable telephones and other personal communication devices.

By now it should be appreciated that there has been provided an electronic device having a graphic display, an LCD driver which uniquely drives a set of scanning electrodes of an LCD panel with one of at least two sets of scanning signals, depending on a mode of the electronic device, and that in one mode of the electronic device the set of scanning signals significantly reduces the power drain of the LCD driver and LCD panel combination compared to another mode.

The present invention, as would be obvious to one of ordinary skill in the art in view of the discussion above could be produced in hardware or software, or in a combination of hardware and software. The system, or method, according to the inventive principles as disclosed in connection with the preferred embodiments, may be produced in a single computing system or device, or it may be arranged in a distributed computing system, interconnected by any suitable means as would be known by one of ordinary skill in art.

According to the inventive principles as disclosed in connection with the preferred embodiment, the invention is not limited to any particular kind of computing system but may be used with any general purpose computer, as would be known to one of ordinary skill in the art, arranged to perform the functions described and the method steps described. The operations of such a computer, as described above, may be according to a computer program contained on a medium for use in the operation or control of the computer, as would be known to one of ordinary skill in the art. The computer medium which may be used to hold or contain the computer program product, may be a fixture of the computer such as an embedded memory or may be on a transportable medium such as a disk, as would be known to one of ordinary skill in the art.

The invention is not limited to any particular computer program or logic or language, or instruction but may be practiced with any such suitable program, logic or language, or instructions as would be known to one of ordinary skill in the art. Without limiting the principles of the disclosed invention any such computing system can include, inter alia, at least a computer readable medium allowing a computer to read data, instructions, messages or message packets, and other computer readable information from the computer readable medium. The computer readable medium may include non-volatile memory, such as ROM, Flash memory, floppy disk, Disk drive memory, CD-ROM, and other permanent storage. Additionally, a computer readable medium may include, for example, volatile storage such as RAM, buffers, cache memory, and network circuits. Furthermore, the computer readable medium may include computer readable information in a transitory state medium such as a network link and/or a network interface, including a wired network or a wireless network, that allow a computer to read such computer readable information.

While the preferred embodiments of the invention have been illustrated and described, it will be clear that the invention is not so limited. Numerous modifications, changes, variations, substitutions, and equivalents will occur to those of ordinary skill in the art without departing from the spirit and scope of the present invention as defined by the following claims.

What is claimed is:

Claims

1. A method for backlighting a display associated with a user device having a processing unit, the method characterized by the steps of: determining whether a user device is in a first mode of operation; and if the user device is in a first mode of operation then performing the sub-step of: backlighting a first portion of the display.

2. The method as defined in claim 1 , wherein if the user device is not in a first mode of operation then performing the sub-step of: determining if the user device is in a second mode of operation; and if the user device is in a second mode of operation then performing a secondary sub-step of: backlighting a second portion of the display.

3. The method as defined in claim 1 , wherein if the first portion of the display is backlit then performing the sub-step of: determining if the user device is in a second mode of operation.

4. The method as defined in claim 3, wherein if the user device is in a second mode of operation then performing the secondary sub-step of: backlighting a second portion of the display.

5. The method as defined in claim 1, wherein the first portion of the display comprises only a partial area of the display.

6. The method as defined in claim 2, wherein the second portion of the display comprises an entire area of the display.

7. The method as defined in claim 1, wherein the display comprises a Liquid Crystal Display (LCD).

8. The method as defined in claim 1, wherein the user device is at least one of: a wireless communication device, a pager, a hand-held device, a portable device, a personal digital assistant, a cellular phone, a two-way portable radio, and a digital phone.

9. The method as defined in claim 6, wherein the second portion of the display comprises a display area used for uses selected from the uses group of: personal digital assistant information display and Internet browsing display.

10. The method as defined in claim 1, wherein the first portion of the display comprises a display area used for phone messages.

11. A user device characterized by: a display; a lighting circuit for lighting first and second portions of the display; a controller, electrically coupled to the display and to the lighting circuit; for displaying information on the display and for controlling the lighting of the first and second portions of the display; and a memory electrically coupled to the controller, the memory storing instructions for the controller to perform functions associated with the user device as follows: determining if the user device is in a first mode of operation; and if the user device is in a first mode of operation then controlling the lighting circuit for lighting a first portion of the display.

12. The user device as defined in claim 11, wherein the first portion of the display comprises only a partial area of the display.

13. The user device as defined in claim 11, wherein the lighting circuit comprises a backlighting circuit for backlighting the first portion of the display, and wherein the controller determines whether the user device is in a first mode of operation, and if the user device is in a first mode of operation then the controller controls the lighting circuit for backlighting the first portion of the display.

14. The user device as defined in claim 11 , wherein the memory includes further instructions for the controller to perform functions as follows: the controller determines whether the user device is in a second mode of operation, and if the user device is in a second mode of operation then controlling the lighting circuit for lighting a second portion of the display.

15. The user device as defined in claim 14, wherein the lighting circuit comprises a backlighting circuit for backlighting the second portion of the display, and wherein the controller determines whether the user device is in a second mode of operation, and if the user device is in the second mode of operation then the controller controls the lighting circuit for backlighting the second portion of the display.

16. The user device as defined in claim 14, wherein the first portion of the display comprises only a partial area of the display and the second portion of the display comprises an entire area of the display.

17. The user device as defined in claim 14, wherein the first portion of the display comprises a display area used for displaying phone messages, and a second portion of the display comprises a display area used for displaying at least one of: personal digital assistant information and Internet browsing information.

18. The user device as defined in claim 11, wherein the display comprises a Liquid Crystal Display (LCD).

19. The user device as defined in claim 11, wherein the user device is at least one of: a wireless communication device, a pager, a hand-held device, a portable device, a personal digital assistant, a cellular phone, a two-way portable radio, and a digital phone.

20. A computer readable medium including instructions for a controller to control a backlighting circuit for backlighting a display associated with a user device, the instructions on the computer readable medium characterized by instructions for the controller as follows: determining whether the user device is in a first mode of operation; and if the user device is in a first mode of operation then performing the sub-step of: backlighting a first portion of the display.

21. The computer readable medium as defined in claim 20, wherein the computer readable medium further includes instructions for the controller as follows: if the user device is not in a first mode of operation then performing the sub-step of: determining whether the user device is in a second mode of operation; and if the user device is in a second mode of operation then backlighting a second portion of the display, and wherein the first portion of the display is less than an entire area of the display and the second portion of the display comprises an entire area of the display.