Electrical transmission or interconnection systems – Switching systems
Reexamination Certificate
1998-02-25
2002-05-14
Fleming, Fritz (Department: 2836)
Electrical transmission or interconnection systems
Switching systems
C307S139000
Reexamination Certificate
active
06388343
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power supply unit and an electronic apparatus using the power supply unit. More particularly, the present invention relates to a power supply unit using a momentary type power switch and an electronic apparatus using the power supply unit. More particularly, the present invention pertains to a power supply unit realizing a remote power on/off scheme using the momentary switch and an electronic apparatus unit using the power supply unit.
2. Related Art
Due to a recent technical revolution, various small size and light weight electrical and electronic apparatuses with an excellent mobility, a notebook personal computer (PC) for example, have been developed. Among them, the notebook PC is designed and fabricated to be small size and light weight with taking consideration of a mobile environment, i.e. use in outdoor requiring portability and mobility. One example of the notebook PC is “IBM ThinkPad 760” series marketed by IBM Japan, Ltd (The “ThinkPad” is a trademark of International Business Machines Corporation). The ThinkPad 760 is a clam shell structure which contains a thin main body and a cover member pivotally mounted to about rear edge of the main body, as shown in the
FIG. 5. A
system board on which a CPU, a memory and various controller chips are mounted is contained within the main body. Also, a hard disk drive (HDD), a floppy disk drive (FDD), and a CD-ROM drive etc., as external storage device, are accommodated into the main body. Also, a key board unit as an input device is mounted on an upper surface of the main body. A liquid crystal display (LCD) unit is embedded within the cover member. An operator can perform a key input with seeing the LCD unit by opening the clam shell cover member. Also, by closing the clam shell cover member, the key board unit and the LCD unit are protectively placed within the personal computer for carrying it. Generally, the notebook PC is a battery powered type which is driven by the battery, since the PC is designed to use it in the mobile environment where a commercial power supply is not available.
Recently, a remote on/off scheme using a momentary type (return type) switch has been frequently used as the power supply on /off circuit scheme of these electronic apparatuses. For example, the above described notebook PC “ThinkPad” series uses the momentary switch as the power switch, to enable the control of the power on/off by a single hand.
The
FIG. 6
shows a block diagram of major parts of the on/off mechanism of a conventional power supply system using the momentary switch. As shown in the
FIG. 6
, a main power source of the electronic apparatus is a battery
20
, and the battery
20
is detachably and exchangeably connected through a connector. An output current of the battery
20
is supplied to a DC/DC converter
50
through a main power line
10
. The DC/DC converter
50
converts the DC voltage of the battery
20
to a level suitable for a system operation, and supplies it to various portions of a system load. A switch SW
2
is inserted on the way of the main power line
10
to turn on/off the output of the main power source. An example of the switch SW
2
is a P channel type FET switch.
A power switch (SW
1
) by which an user can indicate the power on/off of the apparatus is mounted on a surface of an outer wall of a housing of the electronic apparatus. If this power switch SW
1
is the momentary switch, the switch SW
1
returns to the original position when the user manipulation is terminated. Because the switch SW
1
stays at the same position, the switch SW
1
itself can not store the current manipulated state, i.e. the power on state or the power off state. To one end of the switch SW
1
, a latch circuit
30
is connected which stores the current manipulated state of the momentary switch SWI, and the on/off control of the switch SW
2
is performed by the output of the latch circuit
30
rather than the direct output of the momentary switch SW
1
. To be brief, the power on/off operation of the electronic apparatus is remotely made by the latch circuit rather than made directly by the momentary switch SW
1
.
The latch circuit
30
requires a drive voltage. In the example shown in the
FIG. 6
, the latch circuit
30
is applied with a drive voltage V
CC
from the main power line
10
. Even when the electronic apparatus is powered off, the drive voltage V
CC
is required to store the manipulated state of the momentary switch SW
1
. Therefore, the drive voltage V
CC
must be supplied from a node located at the upper stream, i.e. a source side, of the switch SW
2
, which is always powered even when the switch SW
2
is turned off, rather than a node located at the down stream, i.e. a drain side, of the switch SW
2
, which is powered off when the SW
2
is turned off. However, it means that a leak current continuously flows through the latch circuit
30
even when the apparatus is powered off, and that the supply of the drive voltage V
CC
causes an undesired power consumption. In the case that the electronic apparatus is a battery powered type, the leak current flowing from the battery during a long power off period of the electronic apparatus can not be ignored.
Particularly, a requirement has been recently increased to ship the electronic apparatus from a factory with the battery being accommodated into a battery room within the PC body. It is because a user wants to operate the PC at the time he or she opens the package to display system set up instructions on the display unit (it is called as “Instant On”) so that the usability is increased, and because a space in the package for packaging the battery becomes unnecessary thereby saving the costs. However, in the case that a delivery period from the factory to users exceeds several months, the over discharge of the battery may arise due to the leak current to the latch circuit as above described. The over discharge may causes the degradation of the characteristic of the battery, resulting in the increase of the claims by the users.
SUMMARY OF THE INVENTION
The object of the present invention is to provide an excellent electronic apparatus and a power supply unit used into the electronic apparatus which eliminate a leak current during a power off period.
The further object of the present invention is to provide an excellent electronic apparatus and a power supply unit used into the electronic apparatus which use a momentary type power switch.
The further object of the present invention is to provide an electronic apparatus and a power supply unit used into the electronic apparatus which realize a remote power on/off scheme using the momentary switch without a leak of current at a power off period.
The operation of the present invention is described with reference to the FIG.
1
. The
FIG. 1
schematically shows the power supply unit operated in the remote power on/off scheme which embodies the present invention.
The electronic apparatus containing the power supply unit uses a battery
20
as a main power source, and the battery
20
is detachably and exchangeably connected at a connector portion. An output current of the battery
20
is supplied to a DC/DC converter
50
through a main power line
10
. It is substantially the same as that of the prior circuit shown in the
FIG. 6
that the DC voltage from the battery
20
is converted to a voltage level by the DC/DC converter
50
and the voltage level is applied to the various portions of a system load
100
, and that a switch (SW
2
) for turning on/off the output of the main power supply is connected on the way of the main power line
10
. The switch SW
2
may be a P channel type FET, for example.
A momentary switch (SW
1
) by which an user controls the power on/off of the electronic apparatus is mounted on a surface of an outer wall of the electronic apparatus. One terminal of the momentary switch SW
1
is inputted to the latch circuit
30
and a switch drive circuit
40
, and the other terminal of the momentary switch SW
1
is conn
Michigami Toru
Naitoh Arimasa
Nakazawa Yukifumi
Drumheller Ronald L.
Fleming Fritz
International Business Machines - Corporation
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