Electricity: power supply or regulation systems – Output level responsive – Using a three or more terminal semiconductive device as the...
Reexamination Certificate
2002-02-15
2004-03-30
Sherry, Michael (Department: 2838)
Electricity: power supply or regulation systems
Output level responsive
Using a three or more terminal semiconductive device as the...
C307S043000, C307S077000, C363S065000
Reexamination Certificate
active
06713992
ABSTRACT:
FIELD OF THE INVENTION
This patent specification relates to a power supply method and apparatus, and more particularly to a power supply method and apparatus that effectively reduces power consumption.
BACKGROUND OF THE INVENTION
Conventionally, a power supply apparatus that reduces a direct current supplied from a direct current power source (e.g., a battery) to a predetermined voltage is classified into two types; one type using a voltage regulator and the other type using a DC-to-DC converter.
FIG. 1
shows an exemplary circuit of a background power supply apparatus using a voltage regulator
100
. In the voltage regulator
100
of
FIG. 1
, a P-channel-type MOS (metal oxide semiconductor) transistor
102
(hereinafter referred to as a P-MOS transistor
102
) and resisters
103
and
104
are connected in series between a power source terminal applied with a power source voltage VDD by a direct current
101
(e.g., a battery including a secondary battery) and ground. The resisters
103
and
104
divide a voltage Vout which is compared by a voltage comparator
106
with a predetermined reference voltage Vref generated by a reference voltage generator
105
. Based on a comparison result, an operation of the P-MOS transistor
102
is controlled so that the voltage Vout is held at a desired value. In
FIG. 1
, a CPU
107
is an exemplary system that requires power from the voltage regulator
100
.
However, the above-described voltage regulator has a drawback that the P-MOS transistor
101
consumes a great amount of electric power for a reduction of the power source voltage VDD to the voltage Vout. More specifically, when the CPU
107
consumes a current of 100 mA, for example, and a voltage regulator
100
reduces the power source voltage VDD from 3.6 volts, for example, to 2 volts, for example, the P-MOS transistor
101
consumes the power of 0.16 W. That is, the voltage regulator consumes a difference of the battery voltage and the CPU's operational voltage. Such voltage regulator is undesirable for a system aiming a low power consumption since the CPU's operational voltage has been lowered in the recent years.
Accordingly, as shown in
FIG. 2
, a DC-to-DC converter is used in place of the voltage regulator as a power supply in a system (e.g., the CPU
107
) using a battery. In
FIG. 2
, a DC-to-DC converter
110
reduces the power source voltage VDD to a predetermined voltage Vout and supplies the voltage Vout to the CPU
107
.
In general, a system using a battery as a source of power is provided with a sleep function or temporarily stopping the operations of the system to reduce an electrical power consumption on an as needed basis. In the case of the power supply apparatus of
FIG. 2
, it is attempted to reduce the power consumption by changing the output terminal of the DC-to-DC converter
110
to the CPU
107
in the sleep mode from a ground level to a high impedance level. This is because the DC-to-DC converter
110
is used as an apparatus that directly controls the power source required by the system (e.g., the CPU
107
).
On the other hands, the DC-to-DC converter
110
is required to be always in an active state in the case the system (e.g., the CPU
107
) in the sleep mode is intermittently activated to control certain components on an as needed basis. In such a case, the power consumption by the DC-to-DC converter
110
shares a large part of the total system power consumption.
SUMMARY OF THE INVENTION
This patent specification describes a novel power supply apparatus. In one example, this novel power supply apparatus includes a DC-to-DC converted and a voltage regulator. The DC-to-DC converter is arranged and configured to perform a voltage conversion for converting a voltage of a power source supplied from a direct current power source to a first predetermined voltage. The first predetermined voltage is lower than the voltage of the power source. The voltage regulator is arranged and configured to carrying out a voltage regulation for regulating the first predetermined voltage of the power source to at least a second predetermined voltage. The second predetermined voltage is lower than the first predetermined voltage.
The DC-to-DC converter may be turned into a non-active state to stop the voltage conversion and straight passes the voltage of the power source when an operation mode is changed to a sleep mode.
The DC-to-DC converter may include a switching circuit, a smoothing circuit, and a controller. The switching circuit is arranged and configured to perform a switching operation for switching the power source and to output a pulsating current voltage. The smoothing circuit is arranged and configured to smooth the pulsating current voltage output by the switching circuit and to output a smoothed voltage to the voltage regulator. The controller is arranged and configured to detect the smoothed voltage output from the smoothing circuit and to control the switching circuit to change a performance of the switching operation in response to a detection result of the smoothed voltage so that the smoothed voltage output by the smoothing circuit is substantially equal to the first predetermined voltage. The controller is turned into a non-active state to cause the switching circuit to stop the switching operation so as to pass the voltage of the power source through the switching circuit and to output the voltage of the power source to the smoothing circuit when the operation mode is changed to the sleep mode.
The DC-to-DC converter may output the voltage of the power source without performing the voltage conversion when the operation mode is changed to the sleep mode.
The converter may include a switching circuit, a smoothing circuit, and a controller. The switching circuit is arranged and configured to perform a switching operation for switching the power source and outputting a pulsating current voltage. The smoothing circuit is arranged and configured to smooth the pulsating current voltage output from the circuit and to output a smoothed voltage to the voltage regulator. The controller is arranged and configured to detect the smoothed voltage output from the smoothing circuit and to control the switching circuit to change a performance of the switching operation in response to a detection result of the smoothed voltage so that the smoothed voltage output from the smoothing circuit is substantially equal to the first predetermined voltage. The controller causes the switching circuit to stop the switching operation so as to pass the voltage of the power source through the switching circuit and to output the voltage of the power source to the smoothing circuit when the operation mode is changed to the sleep mode.
The controller may connect a load to an output terminal of the smoothing circuit and controls a current flowing the load so as to reduce the voltage output from the smoothing circuit to the first predetermined voltage when the voltage output from the smoothing circuit is lower than the first predetermined voltage and when the operation mode is changed to a normal operation mode.
The controller may include a transistor, a comparator, and a current control circuit. The transistor operates as the load. The comparator performs a first comparison for comparing the voltage output from the smoothing circuit with the first predetermined voltage when the operation mode is changed to the normal operation mode and outputs a first comparison result. The current control circuit is arranged and configured to control the transistor to produce a current flowing therethrough in response to the first comparison result of the comparator when the operation mode is changed to the normal operation mode.
The current control circuit may control the transistor to increase the current at a first predetermined pace when the voltage output from the smoothing circuit is determined as greater than the first predetermined voltage based on the first comparison result performed by the comparator.
The current control circuit may control the transistor to continue to increase th
Matsuo Masahiro
Nitta Shohichi
Dickstein , Shapiro, Morin & Oshinsky, LLP
Laxton Gary L.
Ricoh & Company, Ltd.
Sherry Michael
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