Method for reducing power consumption in a portable electronic device with a liquid crystal display screen

• US 5,890,799 A
• Filed: 11/10/1997
• Issued: 04/06/1999
• Est. Priority Date: 05/18/1995
• Status: Expired due to Term

• Current Assignee: Freescale Semiconductor, Inc. (NXP Semiconductors NV)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Yiu, Hing Leung, Wong, Harvey, Reed, Wendy
• Primary Examiner(s): MOISE, EMMANUEL LIONEL
• Application Number:
  US08/966,831
• Time in Patent Office: 512 Days
• Field of Search: 364/707, 395/560, 395/750.01-750.08, 345/90, 345/206, 345/207, 327/143
• US Class Current: 713/321
• CPC Class Codes: G06F 1/3218 of display devices

Abstract

A method and apparatus for reducing power consumption in a portable electronic device (100) with an LCD screen (104) and operating with a CPU (114) switchable between a high power mode and a low power mode. When input commences on a surface of the LCD screen (104), an interrupt signaler (108) generates a first interrupt signal to an interrupt controller (112). Upon receiving the first interrupt signal, the interrupt controller (112) switches the CPU (114) from the low power mode to the high power mode, turning on at least one detection panel (106) coupled to the LCD screen (104) and to an ADC (110). When input ceases on the surface, the interrupt signaler (108) generates a second interrupt signal to switch the CPU (114) from the high power mode to the low power mode, turning off the at least one detection panel (106) and the ADC (110).

Claims

1. A portable electronic device having a liquid crystal display screen wherein the portable electronic device receives inputs from a surface of the liquid crystal display screen further wherein the liquid crystal display screen includes at least, the portable electronic device comprising:

a central processing unit;

an interrupt signaler, including at least one detection panel of the liquid crystal display screen and a transistor, coupled to a bus, wherein the interrupt signaler generates a first interrupt signal on the bus when input commences on the surface and generates a second interrupt signal on the bus when input ceases on the surface, as detected by the at least one detection panel, and wherein the interrupt signaler is activated when the transistor is switched to a first logic state; and

an interrupt controller, coupled to the bus, for switching the central processing unit from operating at a low power mode to a high power mode in response to reception of the first interrupt signal on the bus and for switching the central processing unit from operating at a high power mode to a low power mode in response to reception of the second interrupt signal on the bus.

2. The portable electronic device of claim 1 wherein the transistor is a P-channel junction field effect transistor.

3. A portable electronic device comprising:

a liquid crystal display screen having a surface for receiving inputs and coupled to at least one detection panel for detecting the inputs on the surface;

an analog to digital converter for converting the inputs to digital signals; and

a central processing unit, operating at either a high power mode or a low power mode, wherein the central processing unit activates the at least one detection panel and the analog to digital converter in the high power mode, the central processing unit comprising;

a transistor, coupled to a bus and to the at least one detection panel, for generating a first interrupt signal on the bus when input commences on the surface and for generating a second interrupt signal on the bus when input ceases on the surface; and

an interrupt controller, coupled to the bus, for switching the central processing unit from operating at the low power mode to the high power mode in response to reception of the first interrupt signal on the bus and for switching the central processing unit from operating at a high power mode to a low power mode in response to reception of the second interrupt signal on the bus.

4. The portable electronic device of claim 3 wherein the transistor is a P-channel junction field effect transistor.

5. The portable electronic device of claim 3 wherein the at least one detection panel comprises a first detection layer detecting the inputs in a first direction.

6. The portable electronic device of claim 5 wherein the at least one detection panel further comprises a second detection layer detecting the inputs in a second direction.

7. A method for reducing power consumption in a portable electronic device wherein the portable electronic device includes a central processing unit operating at either a low power mode or a high power mode, a liquid crystal display screen having a surface for receiving inputs detected by at least one detection panel, and an analog-to-digital converter for converting the inputs to digital signals, the method comprising the steps of:

generating a first interrupt signal when input commences on the surface, wherein the first interrupt signal is generated by an interrupt signaler within the central processing unit coupled to the surface;

switching the central processing unit from the low power mode to the high power mode in response to reception of the first interrupt signal, wherein, while operating in the high power mode, the central processing unit inactivates the interrupt signaler, activates the at least one detection panel and the analog to digital converter to receive the inputs, and reactivates the interrupt signaler when the central processing unit is processing the received inputs;

generating a second interrupt signal in response to voltage variation on a node within the interrupt signaler caused by the input ceasing on the surface, wherein the first interrupt signal is generated by the interrupt signaler; and

switching the central processing unit from the high power to the low power mode and inactivating the at least one detection panel and the analog to digital converter, in response to the second interrupt signal.