Stabilized power unit

Details Stabilized power unit Stabilized power unit

2002-06-05

2003-09-23

Riley, Shawn (Department: 2838)

Electricity: power supply or regulation systems

Output level responsive

Using a three or more terminal semiconductive device as the...

C323S901000

Reexamination Certificate

active

06624619

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a switched-capacitor-type stabilized power unit.
BACKGROUND OF THE INVENTION
FIG. 19
shows a structure of a switched-capacitor-type stabilized power unit
101
for obtaining an output voltage twice as much as an input voltage. The stabilized power unit
101
is structured so as to include an integrated portion
101
a
, and a voltage-increasing capacitor C
101
, an input capacitor C
102
, an output capacitor C
103
, and voltage-dividing resistors R
101
and R
102
provided outside the integrated portion
101
a
. The integrated portion
101
a
is provided with switches S
101
, S
102
, S
103
, S
104
, a control section
111
, a comparator
112
, and a reference voltage source
113
. Further, the integrated portion
101
a
is provided with an output terminal T
101
outputting an output voltage V
o
, an input terminal T
102
to which an input voltage V
in
is inputted from a power source such as a battery, a feedback terminal T
103
for the output voltage V
o
, a GND terminal T
104
, a capacitor connection terminal T
105
to which an electrode C− having a lower potential of the voltage-increasing capacitor C
101
is connected, and a capacitor connection terminal T
106
to which an electrode C+ having a higher potential of the voltage-increasing capacitor C
101
is connected.
In the stabilized power unit
101
, a switched capacitor section is structured by the switches S
101
, S
102
, S
103
, S
104
, and the voltage-increasing capacitor C
101
. The control section
111
controls switching operation of the switches S
101
, S
102
, S
103
, S
104
in the switched capacitor section. When the control section
111
controls the switches S
101
and S
103
to be ON and the switches S
102
and S
104
to be OFF, and the input voltage V
in
is applied to the input terminal T
102
via the input capacitor C
102
, the voltage-increasing capacitor C
101
is charged. Next, when the control section
111
controls the switches S
101
and S
103
to be OFF and the switches S
102
and S
104
to be ON, the respective potentials of the electrodes of the voltage-increasing capacitor C
101
increase by the potential of the input terminal T
102
. The voltage increased by such an operation is outputted as the output voltage V
o
via the output capacitor C
103
.
The output voltage V
o
is detected by the voltage-dividing resistors R
101
and R
102
, and a voltage V
fb
101
at a point connecting the voltage-dividing resistors R
101
and R
102
is inputted to a non-reversal input terminal of the comparator
112
. The comparator
112
compares the voltage V
fb
101
with a reference voltage V
ref
101
generated by the reference power source
113
and inputted to a reversal input terminal. When the voltage V
fb
101
reaches the reference voltage V
ref
101
, the comparator
112
outputs a signal to the control section
111
so as to stop the switching operation of the switches S
101
, S
102
, S
103
, S
104
. The comparator
112
is a comparator having a hysteresis function, and when the switching operation is stopped and the output voltage V
o
decreases, that is, the voltage V
fb
101
decreases, the comparator
112
outputs a signal to the control section
111
so as to resume the switching operation of the switches S
101
, S
102
, S
103
, S
104
. By repeating the foregoing operation, the stabilized power unit
101
stabilizes the output voltage V
o
.
FIG. 20
shows a time chart on the operation of stabilizing the output voltage V
o
in the stabilized power unit
101
. At time t
0
, the switches S
101
and S
103
are ON and the switches S
102
and S
104
are OFF, and the input voltage V
in
is started to be applied, the voltage-increasing capacitor C
101
becomes charged, and the potential of the electrode C+ of the voltage-increasing capacitor C
101
becomes V
in
. Next, at time t
1
, the switches S
101
and S
103
are OFF and the switches S
102
and S
104
are ON, and the potential of the electrode C+ of the voltage-increasing capacitor C
101
becomes 2V
in
, a charge to the output capacitor C
103
is started, and the output voltage V
o
comes to be increased. At time t
2
, the respective switches are in the conditions identical to those at the time t
0
, and the potential of the electrode C+ of the voltage-increasing capacitor C
101
becomes V
in
again. At time t
3
, the respective switches are in the conditions identical to those at the time t
1
, and the potential of the electrode C+ of the voltage-increasing capacitor C
101
becomes 2V
in
, and the output capacitor C
103
becomes charged. In a period from the time t
2
to the time t
3
, since an output current flows from the stabilized power unit
101
to a load, a discharge from the output capacitor C
103
is carried out, and the output voltage V
o
is decreased.
The output voltage V
o
is increased by repeating such a charge and a discharge to and from the output capacitor C
103
in a predetermined duty. When the output voltage V
o
reaches a predetermined threshold level COM
1
, that is, when the voltage V
fb
101
at the point connecting the voltage-dividing resistors R
101
and R
102
reaches the reference voltage V
ref
101
, the comparator
112
outputs a signal for stopping the switching operation to the control section
111
. Suppose that this occurs at time t
k
, the switches S
101
and S
103
are ON and the switches S
102
and S
104
are OFF at the time t
k
, and the condition is maintained. After the time t
k
, the output voltage V
o
continues to be decreased until it declines to a predetermined threshold level COM
2
, where the comparator
112
outputs a signal for starting the switching operation to the control section
111
. Suppose that this occurs at time t
n
, the switches S
101
and S
103
are OFF and the switches S
102
and S
104
are ON at the time t
n
, and the switching operation is started. In such a manner, the stabilized power unit
101
shifts from start-up state to steady state.
However, in the foregoing conventional stabilized power unit
101
, when the output voltage V
o
increases very steeply, there is a possibility that the output voltage V
o
might overshoot and some load connected to the stabilized power unit
101
might fail to function properly.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a switched-capacitor-type stabilized power unit which can prevent an overshoot of an output voltage at start-up, in a structure having an output capacitor which outputs a charged voltage obtained through a plurality of charges by switching operation utilizing a voltage-increasing potential of a voltage-increasing capacitor at the start-up, as the output voltage.
To achieve the foregoing object, a stabilized power unit of the present invention is a switched-capacitor-type stabilized power unit structured so as to include:
an voltage-increasing capacitor which is charged based on an input voltage and whose voltage is increased after being charged;
switching section for carrying out switching operation to alternately switch a charge period and a voltage-increasing period of the voltage-increasing capacitor; and
an output capacitor which outputs a charged voltage obtained by being charged utilizing a voltage-increasing potential of the voltage-increasing capacitor in the voltage-increasing period, as an output voltage, and stabilizes the charged voltage within a range of the output voltage in steady state through a plurality of the voltage-increasing periods after a start-up is started,
wherein the stabilized power unit includes soft start means for controlling the switching section to carry out the switching operation so that the charged voltage always becomes not more than the output voltage in the steady state, at the start-up from when the start-up is started until when the charged voltage is stabilized within the range of the output voltage in the steady state.
According to the foregoing invention, at the start-up, the soft start means controls the switching section to carry out the switching operation so th

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