Power-saving circuit

Details Power-saving circuit Power-saving circuit

2000-01-10

2001-12-04

Berhane, Adolf Deneke (Department: 2838)

Electric power conversion systems

Current conversion

Including d.c.-a.c.-d.c. converter

C363S016000

Reexamination Certificate

active

06327161

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a power-saving circuit for an electronic device. More specifically, the present invention relates to a power-saving circuit applied to the power supply circuit of a monitor. When the monitor is in a power-saving mode, this power-saving circuit can automatically turn off the power supply fed to the voltage booster of the monitor for reducing the power consumption of the monitor.
2. Description of the Related Art
In order to decrease wasted power, most computers in the current market can automatically detect usage
on-usage and enter a power-saving mode if required. Generally speaking, the power-saving mode can be further divided into several finer sub-modes. For the sake of clarity, however, only two modes, the normal mode and the power-saving mode, are discussed.
When a computer is set to enter the power-saving mode, the monitor of the computer is also notified. While in the power-saving mode, the monitor only provides power supply to essential circuitry that is used to continuously receive instructions from the computer and to quickly recover the normal mode when receiving the corresponding instruction.
Referring to
FIG. 1
(Prior Art), an ordinary computer system includes a computer mainframe
20
, a monitor
28
and other accessories. Computer mainframe
20
can detect the usage condition and decide, according to the detection result, whether or not the computer system enters the power-saving mode. When deciding to enter the power-saving mode, computer mainframe
20
does not only enter into power-saving mode itself, but also notifies monitor
28
to enter the power-saving mode.
The modern monitor usually includes a voltage booster at the entry point of the external power supply for dealing with different voltage specifications. The voltage booster is mainly comprised of booster controllers, triac devices and other related components. In addition, the voltage booster can detect the alternative current (AC) voltage supplied by the external power supply and selectively boost the AC voltage according to the detection result. For example, suppose that the internal circuit of a monitor is designed for 200~220 VAC. When detecting that the external power supply is 200~220 VAC, the voltage booster can directly connect the external power supply to the internal circuit. When detecting that the external power supply is 100~110 VAC, the voltage booster can boost the external power supply and then connect it to the internal circuit. Using the boosting scheme, this monitor can be used in various environments.
FIG. 2
(Prior Art) is a circuit diagram of the power supply circuit applied in the conventional monitor. As shown in
FIG. 2
, the power supply circuit includes a voltage booster
320
, a first rectifier
310
, a second rectifier
300
and a first power-saving circuit
370
. For the sake of clarity,
FIG. 2
only illustrates a partial circuit that provides 15 VDC as a second rectifier
300
located in the secondary winding of transformer T
1
. In reality, there are several different circuits in the secondary winding for providing different voltages, such as −15V and 5V. IC
1
represents a booster controller chip, which is used to detect the amplitude of the external power supply and decide whether the triac chip IC
4
should perform the boosting operation.
Suppose that the monitor in
FIG. 2
is designed for 200~220 VAC. The booster controller chip IC
1
can be implemented by AVS1AC or AVS1BC developed by SGS-Thomson and the triac chip IC
4
can be implemented by AVS08CB developed by SGS-Thomson. Nodes AC
1
and AC
2
are connected to two terminals of the external AC power supply, respectively. When detecting that the external power supply is 200~220 VAC, the booster controller chip IC
1
disables the triac chip IC
4
, and nodes A
1
and A
2
of the triac chip IC
4
are open-circuited. Therefore, the voltage on node A is about 200×{square root over (2)}~220×{square root over (2)}. On the other hand, when detecting that the external power supply is 100~110 VAC, the booster controller chip IC
1
enables the triac chip IC
4
, and nodes A
1
and A
2
of the triac chip IC
4
are close-circuited. Therefore, the voltage on node A can be boosted from the original voltage 100×{square root over (2)}~110×{square root over (2)} to 200×{square root over (2)}~220×{square root over (2)}. Using such scheme, the potential of node A can be maintained in 200×{square root over (2)}~220×{square root over (2)} in different operating environments. Accordingly, the monitor can be normally operated.
A mode-detection chip IC
3
is used to receive instructions indicating the current mode from computer mainframe
20
. When receiving an instruction indicating the normal mode, the mode-detection chip IC
3
outputs a logic high signal to turn on transistor Q
3
and transistor Q
4
. Then second rectifier
300
can provide power to the internal circuit of the monitor
28
. When receiving an instruction indicating the power-saving mode, the mode-detection chip IC
3
outputs a logic low signal to turn off transistor Q
3
and transistor Q
4
. Then the second rectifier
300
stops providing power to the internal circuit of the monitor
28
. Therefore, the conventional monitor saves power by stopping the power supply connected to the secondary windings of the transformer T
1
. However, since the voltage booster
320
is directly connected to the external AC power supply, it is inevitable that the voltage booster
320
still consumes a certain amount of power. In fact, the power consumption of the voltage booster
320
is quite large.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a power-saving circuit applied to an electronic device, which can turn off the voltage booster in the power-saving mode, thereby reducing power consumption.
The present invention achieves the above-indicated objects by providing a power circuit for an electronic device. It comprises a power terminal for connecting to an external power source of the electronic device, a voltage booster that is connected to the power terminal and powered by a power supply for selectively boosting the received external power source, a controller for generating a control signal indicating whether or not the electronic device is in power-saving mode, and a switch for disconnecting the power supply from the voltage booster when the control signal indicates that the electronic device is in power-saving mode. The controller and the switch can be used as a power-saving circuit for controlling the power supply of the voltage booster.
Further features and advantages of the present invention, as well as the structure and operation of various embodiments of the present invention, are described in detail below with respect to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements.


REFERENCES:
patent: 4782355 (1988-11-01), Sakai et al.
patent: 4945300 (1990-07-01), Sato et al.
patent: 5905491 (1999-05-01), Kim
patent: 5910891 (1999-06-01), Jo
patent: 36 21 212 C2 (1987-01-01), None
patent: 94/12969 A1 (1994-06-01), None
Sukumar, Vajapeyam, et al., “An Automatic Line Voltage Switching Circuit”,SGS-Thomson Microelectronics, pp. 1-6 (1995).

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