Electrical computers and digital processing systems: support – Computer power control – Power conservation
Reexamination Certificate
2000-12-22
2004-07-27
Lee, Thomas (Department: 2116)
Electrical computers and digital processing systems: support
Computer power control
Power conservation
C713S300000, C713S310000, C713S320000, C713S322000, C713S323000, C345S211000, C345S212000
Reexamination Certificate
active
06769070
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the design of power supply circuits for electrical and electronic equipment. More specifically, the present invention pertains to the reduction of power consumption in a digital display device in standby mode.
2. Related Art
With the increasingly widespread use of computer systems in business and education and at home, it is important to conserve energy by reducing the power consumption of the display devices used with computer systems. Many display devices today provide a mechanism by which the appliance enters a “standby mode” after a period of inactivity, wherein the device remains “on” even though it is not currently being used. While in the standby mode, the device consumes less power than it does while in active use under normal operating conditions (the “main mode”). When activity resumes, the device exits its standby mode and reenters its main mode, and power consumption increases to the normal level. As such, power is conserved in standby mode, and the requisite power level for main mode operation is promptly restored upon the resumption of active use.
Recent regulations, such as those in Europe, stipulate that the power consumption of display devices in standby mode is to be less than one (1) watt (W), instead of the conventional three (3) watts. This and other similar regulatory changes, as well as the desire to conserve power, call for the industry to develop new circuits for implementing a standby mode in display devices that can meet current and pending power consumption requirements.
Several prior art circuits have been developed that use the synchronization (sync) signal(s) that are sent from the computer to the display device, such as the horizontal sync (h-sync) signal and vertical sync (v-sync) signal, as the trigger to switch between main mode and standby mode. In the display device art, it is known that when both the h-sync (horizontal) and v-sync (vertical) signals are present, either separately or in combination, the display device should be in main mode; that when only the v-sync signal is present, the display device should be in suspend mode; and that when only the h-sync signal is present, the display device should be in standby mode. Thus, a sync detect circuit can be used in conjunction with a microprocessor to monitor the sync signal(s) and control the voltage supplied to the monitor accordingly, thereby controlling the power it consumes.
Prior Art
FIG. 1
illustrates one prior art circuit
100
wherein two power supplies are used to implement switching between main mode and standby mode. More particularly, prior art circuit
100
has an alternating current (AC) power input
101
and two separate power supplies
110
and
120
, wherein AC input
101
is coupled to a main power supply
110
and a standby power supply
120
in parallel. Additionally, a microprocessor
130
is coupled between main power supply
110
and standby power supply
120
. Furthermore, a sync detect circuit
140
is coupled between standby power supply
120
and microprocessor
130
. Sync detect circuit
140
is also coupled to a computer
199
.
In this prior art circuit
100
, when the display device is operating in main mode, main power supply
110
provides power to the display device and other circuit elements (e.g., microprocessor
130
and sync detect circuit
140
) via outputs
111
,
112
,
113
and
114
. Typical values for these outputs of main power supply
110
are: +200 volts for output
111
, +80 volts for output
112
, +16 volts for output
113
, and −16 volts for output
114
. With these exemplary values, outputs
111
and
112
are typically coupled to the display device, and outputs
113
and
114
are typically coupled to the horizontal and vertical differentials (h-diff and v-diff) of the display device. In the same circuit
100
, when the display device is in standby mode and is inactive, standby power supply
120
provides power to microprocessor
130
via output
123
(e.g., 5 volts or 3.3 volts) and to sync detect circuit
140
via output
124
(e.g., 5 volts or 3.3 volts).
Still referring to Prior Art
FIG. 1
, sync detect circuit
140
serves as a buffer between computer
199
and microprocessor
130
. When sync detect circuit
140
no longer detects a sync signal
194
from computer
199
, sync detect circuit
140
sends a “no_sync” signal
143
to microprocessor
130
, which in turn sends an “off” signal
131
to main power supply
110
. In response to off signal
131
, main power supply
110
is turned off and the display device enters standby mode.
Note that standby power supply
120
remains on while the display device is in standby mode, in order to power microprocessor
130
and sync detect circuit
140
. In other words, standby power supply
120
is always on irrespective of whether the display device is in main mode or standby mode. As such, sync detect circuit
140
continues to monitor for sync signal
194
from computer
199
while the display device is in standby mode. Upon detecting the resumption of signal
194
from computer
199
, sync detect circuit
140
sends a “sync” signal
143
to microprocessor
130
, which in turn sends an “on” signal
131
to main power supply
110
. In response, main power supply
110
is turned on again and the display device thus resumes its main mode of operation.
One major disadvantage of prior art circuit
100
of
FIG. 1
is that standby power supply
120
remains on even when the display device is in standby mode. The constant presence of an active power supply in circuit
100
means that power loss due to the switching action of the power supply (switching loss) cannot be avoided. Consequently, it is difficult to achieve a low power consumption level using prior art circuit
100
. For example, with AC input
101
at approximately 230 volts (typical for European appliances), and with the exemplary values described above with respect to outputs
123
and
124
(5 volts or 3.3 volts), prior art circuit
100
cannot consistently achieve a standby power consumption of 1 W or less, as is required by the new European standard. Furthermore, prior art circuit
100
is also expensive to implement because an extra power supply (namely, standby power supply
120
) is always required in addition to main power supply
110
.
FIG. 2
illustrates another prior art circuit
200
wherein a single power supply is used to implement switching between main mode and standby mode. More specifically, prior art circuit
200
has an AC power input
201
and a power supply
210
, wherein AC input
201
is coupled to power supply
210
having four outputs
211
,
212
,
213
and
214
. Typical values for these outputs of power supply
210
while the display device is in main mode are: +200 volts for output
211
, +80 volts for output
212
, +16 volts for output
213
, and −16 volts for output
214
.
Outputs
211
and
212
are typically coupled to the display device, and outputs
213
and
214
are typically coupled to the horizontal and vertical differentials (h-diff and v-diff) of the display device. Output
211
is also coupled to a voltage drop circuit
250
, and output
213
is also coupled to a voltage regulator
260
. Voltage regulator
260
is coupled to a microprocessor
230
via line
263
, and to a sync detect circuit
240
via line
264
. Thus, voltage regulator
260
is coupled between power supply
210
and microprocessor
230
, as well as between power supply
210
and sync detect circuit
240
. Sync detect circuit
240
is further coupled to microprocessor
230
and to a computer
299
. Furthermore, microprocessor
230
is coupled to voltage drop circuit
250
, which is in turn coupled to voltage regulator
260
.
Referring to both Prior Art
FIGS. 1 and 2
, it is noted that prior art circuit
200
differs from prior art circuit
100
in that it utilizes a single power supply (namely, power supply
210
) to provide power to the display device and other circuit elements (e.g., microproce
Lee Thomas
Sony Corporation
Trujillo James K.
LandOfFree
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