Electric power conversion systems – Current conversion – Including an a.c.-d.c.-a.c. converter
Reexamination Certificate
2000-04-28
2001-01-16
Han, Jessica (Department: 2838)
Electric power conversion systems
Current conversion
Including an a.c.-d.c.-a.c. converter
C363S124000, C307S066000
Reexamination Certificate
active
06175511
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a uninterruptive power supply for supplying uninterrupted A.C. power to a load.
2. Description of the Related Art
FIG. 7
is a circuit diagram, partly in block diagram, showing the configuration of a conventional uninterruptive power supply which is disclosed in Japanese Patent Application Laid-Open No. Hei 7-87686 for example.
In
FIG. 7
, reference numeral
1
designates an A.C. power source, reference numeral
2
designates a rectifier for rectifying an alternating current from the A.C. power source
1
into a direct current, reference numeral
3
designates a D.C. intermediate circuit which is connected to a D.C. output of the rectifier
2
, reference numeral
4
designates a smoothing capacitor for smoothing the voltage developed across the D.C. intermediate circuit
3
, reference numeral
5
designates an inverter for converting a direct current from the D.C. intermediate circuit
3
into an alternating circuit, and reference numeral
6
designates a load.
Reference numeral
7
designates a stepup/stepdown chopper for supplying the electric charges from the D.C. intermediate circuit
3
to batteries
8
and for discharging electric charge from the batteries
8
to the D.C. intermediate circuit
3
. The stepup/stepdown chopper
7
includes the batteries
8
having the lower voltage than the voltage across the D.C. intermediate circuit
3
, a smoothing capacitor
9
, a chopper reactor
10
, a first transistor
11
, a first free wheel diode
12
, a second transistor
13
and a second free wheel diode
14
.
In addition, reference numeral
15
designates a chopper controlling circuit for operating the above-mentioned stepup/stepdown chopper
7
as the stepdown chopper during the non-interruption to charge the above-mentioned batteries
8
, while for operating the above-mentioned stepup/stepdown chopper
7
as the boosting chopper during the detection of the service interruption to supply the direct current to the above-mentioned D.C. intermediate circuit
3
with the above-mentioned batteries
8
as the D.C. power source. The chopper controlling circuit
15
includes a first gate driving circuit
16
, a second gate driving circuit
17
, and a pulse generating circuit
18
for outputting the gate pulse to the first gate driving circuit
16
and the second gate driving circuit
17
depending on whether or not the service interruption has been detected. In addition, reference numeral
19
designates a voltage sensor for detecting the voltage of the A.C. power source
1
, and reference numeral
20
designates a service interruption detector for detecting the service interruption of the A.C. power source
1
on the basis of the output of the voltage sensor
19
.
Next, the operation will hereinbelow be described.
Normally, the rectifier
2
rectifies the alternating current from the A.C. power source
1
into the direct current to output the resultant direct current to the D.C. intermediate circuit
3
. The inverter
5
converts the direct current from the D.C. intermediate circuit
3
into the alternating current to apply the resultant A.C. output to the load
6
.
At this time, if the service interruption detector
20
for detecting the service interruption of the A.C. power source
1
has not detected the service interruption on the basis of the output from the voltage sensor
19
for detecting the voltage of the A.C. power source
1
, then the pulse generating circuit
18
outputs the pulse to the first gate driving circuit
16
in such a way that the first transistor
11
carries out repeatedly the ON/OFF operation.
That is, at the time when the pulse generating circuit
18
has operated the first gate driving circuit
16
to turn ON the first transistor
11
on the basis of the gate signal from the first gate driving circuit
16
, the charging current is caused to flow into the batteries
8
through the path of the D.C. intermediate circuit
3
→the first transistor
11
the chopper reactor
10
→the batteries
8
→the D.C. intermediate circuit
3
. Next, at the time when the first transistor
11
has been turned OFF, the current which has been caused to flow through the chopper reactor
10
circulates through the path of the chopper reactor
10
→the batteries
8
→the second free wheel diode
14
→the chopper reactor
10
so that the stepup/stepdown chopper
7
operates as the well known stepdown chopper including the first transistor
11
, the chopper reactor
10
, and the second free wheel diode
14
with the D.C. intermediate circuit
3
as the D.C. power source to charge the batteries
8
.
On the other hand, at the time when the service of the A.C. power source
1
has been interrupted, the service interruption detector
20
outputs the signal to the pulse generating circuit
18
which outputs, in turn, the pulse to the second gate driving circuit
17
in such a way that the second transistor
13
carries out repeatedly the ON/OFF operation.
That is, at the time when the pulse generating circuit
18
has operated the second gate driving circuit
17
to turn ON the second transistor
13
on the basis of the gate signal from the second gate driving circuit
17
, the current is increasingly caused to flow through the path of the batteries
8
→the chopper reactor
10
→the second transistor
13
→the batteries
8
with the batteries
8
as the power source. Next, at the time when the second transistor
13
is turned OFF, the current is caused to flow through the path of the chopper reactor
10
→the first free wheel diode
12
→the D.C. intermediate circuit
3
→the inverter
5
and hence the stepup/stepdown chopper
7
operates as the well known boosting chopper including the second transistor
13
, the chopper reactor
10
, and the first free wheel diode
12
with the batteries
8
as the D.C. power source to supply the direct current to the D.C. intermediate circuit
3
so that the inverter
5
supplies the alternating current to the load
6
in the uninterruptive manner.
Since the conventional uninterruptive power supply is configured as described above, the power source for supplying the load
6
with the electric power is either the A.C. power source
1
in the normal case, or the batteries
8
when the service interruption occurs. Therefore, there arises the problem in that the power consumption of the load
6
is increased, and hence when exceeding the supply ability of the A.C. power source
1
or adjusting the demand electric power on the A.C. power source
1
side, the electric power supplied from the A.C. power source
1
, i.e., the input of the rectifier
2
can not be limited.
SUMMARY OF THE INVENTION
The present invention has been made in order to solve the above-mentioned problems, and therefore has an object to obtain a uninterruptive power supply which is capable of limiting the A.C. input and also of supplying the predetermined electric power from an inverter.
In order to attain the above-mentioned object, according to one aspect of the present invention, there is provided a uninterruptive power supply including: an A.C. power source; an input filter for smoothing an A.C. current from the A.C. power source; a rectifier for converting an alternating current which has been inputted through the input filter into a direct current to output the resultant direct current to a D.C. intermediate circuit; an inverter for converting a direct current which has been inputted through the D.C. intermediate circuit into an alternating current to output the resultant alternating current to a load; a stepup/stepdown chopper having batteries for charging the electric charges through a chopper reactor from the D.C. intermediate circuit to the batteries and for discharging the electric charges from the batteries to the D.C. intermediate circuit through the chopper reactor; an A.C. power source voltage detecting means for detecting the voltage of the A.C. power source; service interruption detecting means for detecting the service interruption
Han Jessica
Leydig , Voit & Mayer, Ltd.
Mitsubishi Denki & Kabushiki Kaisha
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