Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
2002-08-27
2004-11-16
Hoff, Marc S. (Department: 2857)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
C700S296000, C700S306000
Reexamination Certificate
active
06820018
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a power control circuit for controlling on/off of a power source to an electronic device.
2. Description of the Prior Art
Conventionally, to turn on/off an electronic device, as shown in
FIG. 11
, a power on/off switch SW
1
is provided between a battery BATT
1
and a circuit block
54
to directly turn power supply on/off. If an automatic power-off function is required, as shown in
FIG. 12
, a power device Q
1
such as a power MOS and a power transistor is provided between a battery BATT
2
and a circuit block
54
, and the power device Q
1
is turned on or off in response to on or off of a power on/off switch SW
2
.
When such a power device is used in an electronic device, the power device must be controlled by monitoring a state of a power on/off switch in the electronic device continuously using a microcomputer, for example. In this case, supply of electrical power to a circuit block of the electronic device can be cut off. However, since the microcomputer must monitor the state of the power on/off switch continuously, electrical power is continuously supplied to the microcomputer to maintain the function of the microcomputer. In practice, the microcomputer monitors the state of the power on/off switch by using a power saving mode such as a sleep mode.
In the case of an example as shown in
FIG. 12
, the electric power supplies to the microcomputer
56
continuously, so the microcomputer
56
monitors a power on/off state of a power on/off switch SW
2
via a SW monitoring port continuously.
Here, if the power on/off switch SW
2
is turned off, the level of the SW monitoring port becomes low since the SW monitoring port is connected to ground via a resistive element R
1
. When the microcomputer
56
detects that the level of the SW monitoring port is low, the microcomputer
56
sets a circuit power-supply control port to a high level. Thus, a power device Q
1
is turned off, thereby stopping the power supply to a circuit block
54
. Namely, a power of the electronic device is turned off.
On the other hand, if the power on/off switch SW
2
is turned on, the level of the SW monitoring port becomes high. When the microcomputer
56
detects that the SW monitoring port is a high level, the microcomputer
56
sets the circuit power-supply control port to a low level. Thus, the power device Q
1
is turned on, thereby supplying power to the circuit block
54
. Namely, a power of the electronic device is turned on.
When the automatic power-off function mentioned above is provided in the electronic device, the electronic device must be constructed to be able to turn on and off of the electronic device by using a controller such as the microcomputer
56
.
However, in this configuration, if the power to the microcomputer
56
is turned off, the microcomputer
56
will not be able to turn on the power to the power device Q
1
, i.e., the power to the electronic device. Therefore, even if the power supply to the circuit block
54
is stopped, the electrical power must be supplied to the microcomputer
56
continuously.
Therefore, if the electronic device is equipped with an automatic power-off function, the controller such as the microcomputer
56
necessarily consumes the electric power. In particular, if the electronic device is battery-operated, there is a disadvantage to shorten an operating time of the electronic device because of power consumption by the controller.
Further, in the conventional electronic device as shown in
FIG. 12
, two ports, i.e., the SW monitoring port and the circuit power-supply control port, and the microcomputer
56
are need. In addition, as mentioned above, the microcomputer
56
needs a program for controlling a shift to a sleep mode after automatic power off as well as a program for monitoring the state of the power on/off switch SW
2
and controlling on and off of the power device Q
1
in response to an interrupt process. Therefore, the program for the microcomputer
56
becomes complicated, thus leading to the case that the incidence of bug in the program is increased.
SUMMARY OF THE INVENTION
In view of the stated problem of the conventional art, it is therefore an object of the present invention to provide a power control circuit having an automatic power-off function capable of reducing electrical power consumption if the power is turned off, of reducing the number of ports of a microcomputer, and of simplifying program of the microcomputer.
In accordance with one aspect of the present invention, in order to achieve the above object, the present invention is directed to a power control circuit that controls on/off of power of an electronic device including a power section and a predetermined circuit block. The power control circuit of the present invention comprises: a power on/off switch having a first switch and a second switch, the first and second switches adapted to be turned on or off simultaneously; a capacitive element connected to the power section via the first switch, said capacitive element adapted to be charged by the power section via the first switch when said power on/off switch is turned off and to be discharged when said power on/off switch is turned on; a first switching element connected to the power section via the second switch, said first switching element adapted to be turned off when said power on/off switch is turned off, and to be in a power-on state while an electric charge that has been charged in said capacitive element is being discharged when said power on/off switch is turned on; a microcomputer for controlling power on/off of said first switching element; and a second switching element provided between the power section and each of said microcomputer and the predetermined circuit block, said second switching element adapted to be turned off to stop power supply to said microcomputer and the predetermined circuit block when said first switching element is turned off, and to be turned on to supply power to said microcomputer and the predetermined circuit block when said first switching element is turned on. In this case, the microcomputer is programmed to control the power control circuit such that, when supplying power to said microcomputer, said microcomputer holds the power-on state of said first switching element before said first switching element is turned off because of the discharge of the electric charge charged in said capacitive element, and then, when said microcomputer detects that the predetermined circuit block has not operated for a given period of time, said microcomputer turns off said first switching element.
In one preferred embodiment of this invention, it is preferred that the power section includes one or more battery. It is also preferred that the first and second switching elements are transistors.
In this embodiment of the present invention, the power control circuit may further comprise a regulator provided between said second switching element and the predetermined circuit block for stabilizing a power-supply voltage supplied from the power section.
Further, in this embodiment of the present invention, the electronic device may be selected from a printer, a notebook type personal computer, a personal data assistant machine, a handy type game machine, and a battery-operated radio and audio equipment.
If the electronic device is a printer, the printer may be a Cycolor type printer. Also, the printer may comprise a head for exposure on which one or more light sources for emitting red light, one or more light sources for emitting green light, and one or more light sources for emitting blue light are provided. In this case, the printer is constructed to reproduce an image on a photosensitive printing paper by exposing the photosensitive printing paper by means of said head for exposure. Here, the photosensitive printing paper may contain a plurality of photosensitive microcapsules to be exposed by said head for exposure.
Moreover, the printer may further comprise: a first group of registers for setting ima
Akitaya Masato
Yamaguchi Yumiko
Barbee Manuel L.
Hoff Marc S.
Mitsumi Electric Co. Ltd.
Patents + TMS P.C.
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