Uninterruptable power supply

An uninterruptable power supply in which, even if the consumed electric power of a load is increased, the voltage of a D.C. intermediate circuit is not decreased below a set voltage and the input electric power from an A.C. power source is limited to no more than a set value. The uninterruptable power supply includes: a rectifier for converting an alternating current into a direct current; an inverter for converting the direct current into an alternating current output to a load; a stepup/stepdown chopper for charging batteries and for discharging the batteries; a service interruption detector for detecting the service interruption of the A.C. power source; and a control circuit for operating the stepup/stepdown chopper as a stepdown chopper during non-interruption to charge the batteries, and as a boosting chopper to supply direct current with the batteries as the D.C. power source, wherein, when the input electric power exceeds a limit, the stepup/stepdown chopper operates as the boosting chopper to supply electric power from the batteries, reducing the electric power input from the A.C. power source.

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.fwdarw.the first transistor 11 the
 chopper reactor 10.fwdarw.the batteries 8.fwdarw.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.fwdarw.the
 batteries 8.fwdarw.the second free wheel diode 14.fwdarw.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.fwdarw.the chopper reactor 10.fwdarw.the second transistor 13.fwdarw.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.fwdarw.the first free wheel
 diode 12.fwdarw.the D.C. intermediate circuit 3.fwdarw.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 on the basis of the voltage detected by the voltage
 detecting means; and control means for operating the stepup/stepdown
 chopper as the stepdown chopper during the non-interruption on the basis
 of the signal detected by the service interruption detecting means to
 charge the batteries, while for operating the stepup/stepdown chopper as
 the boosting chopper during the detection of the service interruption to
 supply the direct current to the D.C. intermediate circuit with the
 batteries as the D.C. power source, characterized in that the control
 means, when the input electric power inputted from the A.C. power source
 exceeds the electric power for the limitation, operates the
 stepup/stepdown chopper as the boosting chopper to supply a part of the
 electric power which is supplied from the inverter to the load from the
 batteries, thereby suppressing the input electric power from the A.C.
 power source.
 In addition, according to another aspect of the present invention, the
 uninterruptive power supply further includes a D.C. intermediate circuit
 voltage detecting means for detecting the voltage developed across the
 D.C. intermediate circuit, characterized in that the control means detects
 on the basis of the voltage detected by the D.C. intermediate circuit
 voltage detecting means that the input electric power which has been
 inputted from the A.C. power source exceeds the electric power for the
 limitation.
 In addition, according to still another aspect of the present invention,
 the uninterruptive power supply further includes: a D.C. intermediate
 circuit voltage detecting means for detecting the voltage developed across
 the D.C. intermediate circuit; current detecting means for detecting the
 current which has been outputted by the rectifier; and input electric
 power detecting means for detecting the input electric power by
 multiplying the voltage detected by the D.C. intermediate circuit voltage
 detecting means by the current detected by the current detecting means,
 characterized in that the control means detects on the basis of the
 electric power detected by the input electric power detecting means that
 the input electric power which has been inputted from the A.C. power
 source exceeds the electric power for the limitation.
 In addition, according to a still another aspect of the present invention,
 the uninterruptive power supply further includes: a D.C. intermediate
 circuit voltage detecting means for detecting the voltage of the D.C.
 intermediate circuit; and input electric power detecting means for
 detecting the input electric power on the basis of the voltage detected by
 the D.C. intermediate circuit voltage detecting means, the voltage
 detected by the A.C. power source voltage detecting means, and the
 impedance of the input filter, characterized in that the control means
 detects on the basis of the electric power detected by the input electric
 power detecting means that the input electric power which has been
 inputted from the A.C. power source exceeds the electric power for the
 limitation.
 In addition, according to a still another aspect of the present invention,
 the uninterruptive power supply further includes: inverter output voltage
 detecting means for detecting the output voltage of the inverter; inverter
 output current detecting means for detecting the output current of the
 inverter; inverter output electric power detecting means for detecting the
 output electric power of the inverter by multiplying the voltage detected
 by the inverter output voltage detecting means by the current detected by
 the inverter output current detecting means; battery output voltage
 detecting means for detecting the output voltage of the batteries; battery
 output current detecting means for detecting the output current of the
 batteries; and battery output electric power detecting means for detecting
 the output electric power of the batteries by multiplying the voltage
 detected by the battery output voltage detecting means by the current
 detected by the battery output current detecting means, characterized in
 that the control means detects on the basis of the sum of the electric
 power detected by the inverter output electric power detecting means and
 the electric power detected by the battery output electric power detecting
 means that the input electric power which has been inputted from the A.C.
 power source exceeds the electric power for the limitation.
 In addition, according to a still further aspect of the present invention,
 it is characterized in that the stepup/stepdown chopper includes switching
 means provided between the batteries and the chopper reactor for the
 protection against the overcurrent, and circulation means for making the
 current, which is caused to flow due to the energy which has been
 accumulated in the chopper reactor in the opening of the switching means,
 circulate through the D.C. intermediate circuit.
 In addition, according to a still another aspect of the present invention,
 the stepup/stepdown chopper includes, as the chopper reactors, a charging
 chopper reactor which is provided in the charging path leading to the
 batteries and a discharging chopper reactor which is provided in the
 discharging path leading to the D.C. intermediate circuit, characterized
 in that the inductance of the charging chopper reactor is set to a large
 value, while the inductance of the discharging chopper reactor is set to a
 small value.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The preferred embodiments of the present invention will hereinafter be
 described in detail with reference to the accompanying drawings.
 (First Embodiment)
 FIG. 1 is a circuit diagram, partly in block diagram, showing the
 configuration of a uninterruptive power supply according to a first
 embodiment of the present invention.
 In FIG. 1, the same portions as those in the conventional example shown in
 FIG. 7 are designated by the same reference numerals and the description
 thereof is omitted here for the sake of simplicity. As for new reference
 numerals, reference numeral 21 designates an input filter which includes a
 reactor or both of a reactor and a capacitor for smoothing the A.C.
 current inputted to the rectifier 2 including the diodes from the A.C.
 power source 1, reference numeral 22 designates a voltage sensor for
 detecting the D.C. voltage of the D.C. intermediate circuit 3, and
 reference numeral 15a designates a chopper control circuit according to
 the first embodiment. The chopper control circuit 15a includes the first
 gate driving circuit 16 and the second gate driving circuit 17 which are
 the same in the configuration as those in the conventional example shown
 in FIG. 7, and also a pulse generating circuit 18a for outputting the gate
 pulse to the first gate driving circuit 16 and the second gate driving
 circuit 17 in accordance with the outputs of the service interruption
 detector 20 and the voltage sensor 22.
 Now, the above-mentioned pulse generating circuit 18a is configured in such
 a way as to detect on the basis of the voltage detected by the voltage
 sensor 22 that the input electric power which has been inputted from the
 A.C. power source 1 exceeds the electric power to be limited and in the
 detection thereof, to operate the stepup/stepdown chopper 7 as the
 boosting chopper to supply the exceeded electric power in the form of the
 D.C. electric power from the batteries 8 to the inverter 5 through the
 D.C. intermediate circuit 3. Also, the pulse generating circuit 18a is
 configured in such a way as to control the voltage of the D.C.
 intermediate circuit 3 to suppress the input electric power from the A.C.
 power source 1.
 The input electric power from the A.C. power source 1 can be determined on
 the basis of the impedance of the input filter 21, the voltage of the A.C.
 power source 1 and the voltage of the A.C. intermediate circuit 3, it can
 be detected on the basis of the voltage of the D.C. intermediate circuit 3
 detected by the voltage sensor 22 that ihe input electric power which has
 been inputted from the A.C. power source 1 exceeds the electric power to
 be limited, from the fact that the input electric power from the A.C.
 power source 1 becomes large as the voltage of the D.C. intermediate
 circuit 3 becomes lower, in other words, the voltage of the D.C.
 intermediate circuit 3 becomes low if the consumed electric power of the
 load 6 becomes large. In the detection thereof, the stepup/stepdown
 chopper 7 is operated as the boosting chopper to supply the exceeded
 electric power in the form of the D.C. electric power from the batteries 8
 to the inverter 5 through the D.C. intermediate circuit 3, thereby being
 able to suppress the input electric power from the A.C. power source 1.
 Next, the operation will hereinbelow be described.
 A pulse generating circuit 18a, when the service interruption detector 20
 has outputted the service interruption signal, outputs the same pulse as
 that in the conventional uninterruptive power supply shown in FIG. 7 to
 the second gate driving circuit 17. On the other hand, when the service
 interruption detector 20 does not output the service interruption signal
 and also the detected voltage of the D.C. intermediate circuit 3 which has
 been outputted by the voltage sensor 22 is higher than the setting
 voltage, the pulse generating circuit 18a outputs the same pulse as that
 in the conventional uninterruptive power supply to the first gate driving
 circuit 16. In addition, when the service interruption detector 20 does
 not output the service interruption signal and also the voltage of the
 D.C. intermediate circuit 3 which has been outputted by the voltage sensor
 22 is lower than the setting voltage, the pulse generating circuit 18a
 outputs the pulse, which has been determined in accordance with the
 magnitude of the deviation in such a way that the deviation between the
 setting voltage and the voltage of the D.C. intermediate circuit 3 becomes
 zero, to either the first gate driving circuit 16 or the second gate
 driving circuit 17. The setting voltage of the D.C. intermediate circuit 3
 on the basis of which the operation of the pulse generating circuit 18a is
 switched can be uniquely obtained from the electric power supplied from
 the A.C. power source 1 which is to be limited, the known voltage of the
 A.C. power source 1 and the impedance of the input filter 20.
 If the pulse generating circuit 18a which is operated as described above is
 employed, then the same function as that in the conventional
 uninterruptive power supply can be attained in which in the normal
 operation, the A,C. power source is supplied to the load 6 on the basis of
 the electric power supplied from the A.C. power source 1, and the first
 transistor 11 is turned ON or OFF to charge the batteries 8, while when
 the service of the A.C. power source 1 is interrupted, the second
 transistor 13 is turned ON or OFF to supply the load 6 with the A,C. power
 source on the basis of the electric power supplied from the batteries 8.
 In addition to that function, if it is detected from the deviation between
 the voltage of the D.C. intermediate circuit 3 and the setting voltage
 that the sum of the consumed electric power of the load 6 and the charging
 electric power for the batteries 8 exceeds the electric power of the A.C.
 input to be limited, then when the voltage of the D.C. intermediate
 circuit 3 is lower than the setting voltage, since the input voltage to be
 limited is exceeded, first of all, the pulse generating circuit 18a
 outputs the pulse to the first gate driving circuit 16 in such a way as to
 stop the charge for the batteries 8. When there is still the deviation for
 all that, i.e., when if the charge for the batteries 8 is stopped, the
 voltage of the D.C. intermediate circuit 3 is increased, but when the
 consumed electric power of the load 6 is large and also the D.C. voltage
 is lower than the setting voltage, the pulse generating circuit 18a
 outputs the pulse to the second gate driving circuit 17 to turn ON the
 second transistor 13 to operate the stepup/stepdown chopper 7 as the
 boosting chopper, thereby making the deviation zero.
 Therefore, according to the above-mentioned first embodiment, even if the
 consumed electric power of the load 6 is increased, the voltage of the
 D.C. intermediate circuit 3 does not lower than the setting voltage, and
 the input electric power from the A.C. power source 1 can be limited to
 the level equal to or lower than the setting electric power.
 (Second Embodiment)
 While in the above-mentioned first embodiment, the description has been
 given with respect to the case where in order to limit the input electric
 power from the A.C. power source 1, the operation of the pulse generating
 circuit is switched on the basis of only the detected voltage of the D.C.
 intermediate circuit 3 which has been outputted by the voltage sensor 22,
 when the power source voltage of the A.C. power source 1 fluctuates, the
 input electric power can not be detected on the basis of only the voltage
 of the D.C. intermediate circuit 3. Then, in a second embodiment, there is
 provided a uninterruptive power supply in which even if the voltage of the
 A. C. power source 1 fluctuates, the input electric power does not exceed
 the setting electric power and hence the input electric power from the
 A.C. power source 1 can be limited.
 FIG. 2 is a circuit diagram, partly in block diagram, showing the
 configuration of a uninterruptive power supply according to the second
 embodiment of the present invention.
 In FIG. 2, the same portions as those of the first embodiment shown in FIG.
 1 are designated by the same reference numerals and the description
 thereof is omitted here for the sake of simplicity. As for new reference
 numerals, reference numeral 23 designates a current sensor for detecting
 the current which has been outputted by the rectifier 2, and reference
 numeral 24 designates an input electric power detecting circuit for
 detecting the input electric power by multiplying the detected current
 which has been outputted by the current sensor 23 by the voltage of the
 D.C. intermediate circuit 3 which has been outputted by the voltage sensor
 22.
 Then, a pulse generating circuit 18b in the second embodiment is configured
 in such a way as to detect on the basis of the electric power detected by
 the above-mentioned input electric power detecting circuit 24 that the
 input electric power which has been inputted from the A.C. power source
 exceeds the electric power to be limited. When the service interruption
 detector 20 does not output the service interruption signal and also the
 input electric power which has been outputted by the input electric power
 detecting circuit 24 is higher than the setting electric power, the pulse
 generating circuit 18b outputs the pulse, which has been determined in
 accordance with the magnitude of the deviation, in such a way that the
 deviation between the setting electric power and the input electric power
 becomes zero to either the first gate driving circuit 16 or the second
 gate driving circuit 17.
 When the uninterruptive power supply is configured in the manner as
 described above, if the input electric power which has been outputted from
 the input electric power detecting circuit 24 to be inputted to the pulse
 generating circuit 18b exceeds the setting electric power of the A.C.
 input to be limited, then the pulse generating circuit 18b, first of all,
 outputs the pulse to the first gate driving circuit in such a way as to
 stop the charge for the batteries 8. When there is still the deviation for
 all that, the pulse generating circuit 18b outputs the pulse to the second
 gate driving circuit in such a way that the deviation becomes zero.
 Therefore, according to the second embodiment, even when the voltage of the
 A.C. power source 1 fluctuates, the input electric power does not exceed
 the setting electric power, and hence the input electric power from the
 A.C. power source 1 can be limited.
 (Third Embodiment)
 While in the above-mentioned second embodiment, the description has been
 given with respect to the case where the input electric power is detected
 by multiplying the voltage which has been outputted by the rectifier 2 by
 the current which has been outputted by the rectifier 2, the current
 sensor 23 for detecting the current which has been outputted by the
 rectifier 2 needs to be provided. In a third embodiment, there is provided
 a uninterruptive power supply which is inexpensive without requiring the
 current sensor 23.
 FIG. 3 is a circuit diagram, partly in block diagram, showing the
 configuration of a uninterruptive power supply according to the third
 embodiment of the present invention.
 In FIG. 3, the same portions as those of the second embodiment shown in
 FIG. 2 are designated by the same reference numerals and the description
 thereof is omitted here for the sake of simplicity. As for new reference
 numerals, reference numeral 25 designates an input electric power
 detecting circuit for detecting the input electric power on the basis of
 the voltage of the D.C. intermediate circuit 3 which has been detected by
 the voltage sensor 22, the voltage of the A.C. power source 1 which has
 been detected by the voltage sensor 19, and the impedance of the input
 filter 21. Also, the pulse generating circuit 18b according to the third
 embodiment is configured in such a way as to detect on the basis of the
 electric power detected by the input electric power detecting circuit 25
 that the input electric power which has been inputted from the A.C. power
 source exceeds the electric power to be limited.
 In the third embodiment, the input electric power detecting circuit 25, as
 shown in FIG. 3, is configured in such a way as to receive as its input
 the voltage of the D.C. intermediate circuit 3 which has been outputted by
 the voltage sensor 22 and the voltage of the A.C. power source 1 which has
 been outputted by the voltage sensor 19 to detect the input electric power
 with the voltage of the A.C. power source 1, the voltage of the D.C.
 intermediate circuit 3 and the impedance of the input filter 20 as the
 parameters. The pulse generating circuit 18b detects on the basis of the
 detected electric power which has been outputted by the input electric
 power detecting circuit 25 whether or not the input electric power which
 has been inputted from the A.C. power source 1 exceeds the setting
 electric power of the A.C. input to be limited. For this reason, the
 current sensor which was employed in the second embodiment and serves to
 detect the current which has been outputted by the rectifier 2 becomes
 unnecessary and hence the uninterruptive power supply becomes inexpensive
 and also is operated in the same manner as that in the second embodiment.
 (Fourth Embodiment)
 While in the first to third embodiments, the description has been given
 with respect to the case where the input electric power is detected and
 the chopper is operated in such a way that the input electric power does
 not exceed the electric power to be limited, in a fourth embodiment, the
 description will hereinbelow be given with respect to the case where the
 output electric power of the inverter 5 and the output electric power of
 the batteries 8 are both detected, it is detected on the basis of the
 relation between the two detected electric powers and the electric power
 of the A.C. power source 1 to be limited whether or not the input electric
 power which has been inputted from the A.C. power source 1 exceeds the
 electric power to be limited, and then the operation of the pulse
 generating circuit is switched.
 FIG. 4 is a circuit diagram, partly in block diagram, showing the
 configuration of a uninterruptive power supply according to the fourth
 embodiment of the present invention.
 In FIG. 4, the same portions as those of the first embodiment shown in FIG.
 1 are designated by the same reference numerals and the description
 thereof is omitted here for the sake of simplicity. As for new reference
 numerals, reference numeral 26 designates a current sensor for detecting
 the output current from the inverter 5, reference numeral 27 designates a
 voltage sensor for detecting the output voltage from the inverter 5,
 reference numeral 28 designates an output electric power detecting circuit
 for detecting the output electric power of the inverter by multiplying the
 output of the current sensor 25 by the output of the voltage sensor,
 reference numeral 29 designates a current sensor for detecting the output
 current of the batteries 8 within a stepup/stepdown chopper 7a according
 to the fourth embodiment, reference numeral 30 designates a voltage sensor
 for detecting the voltage of the batteries 8, and reference numeral 31
 designates a battery electric power detecting circuit for detecting the
 output electric power of the batteries 8 by multiplying the output of the
 current sensor 29 by the output of the voltage sensor 30. Also, a pulse
 generating circuit 18c according to the fourth embodiment is configured in
 such a way as to detect on the basis of the sum of the electric power of
 the inverter 5 detected by the output electric power detecting circuit 28
 and the electric power detected by the battery electric power detecting
 circuit 31 whether or not the input electric power which has been inputted
 from the A.C. power source 1 exceeds the electric power to be limited. In
 this connection, with respect to the electric power of the batteries 8,
 the charging direction for the batteries 8 is made positive, and the
 discharging direction thereof is made negative.
 In the fourth embodiment configured as shown in FIG. 4, when the service
 interruption detector 20 does not output the service interruption signal,
 and also the sum of the output electric power which has been outputted by
 the output electric power detecting circuit 28 and the battery electric
 power which has been outputted by the battery electric power detecting
 circuit 31 is higher than the setting electric power, the pulse generating
 circuit 18c outputs the pulse, which has been determined in accordance
 with the magnitude of the deviation in such a way that the deviation
 between the sum of the output electric power and the battery electric
 power, and the setting electric power becomes zero, to either the first
 gate driving circuit 16 or the second gate driving circuit 17.
 That is, at the time when the sum of the output electric power which has
 been outputted by the output electric power detecting circuit 28 to be
 inputted to the pulse generating circuit 18c and the battery electric
 power which has been outputted by the battery electric power detecting
 circuit 31 exceeds the setting electric power of the A.C. input to be
 limited, the pulse generating circuit 18c, first of all, outputs the pulse
 to the first gate driving circuit 16 so as to stop the charge for the
 batteries 8. When the electric power has still the deviation for all that,
 the pulse generating circuit 18c outputs the pulse to the second gate
 driving circuit 17 in such a way that the deviation becomes zero. In such
 a manner, the input electric power from the A.c. power source 1 can be
 limited.
 Now, the current sensors 26 and 29, the voltage sensors 27 and 30, and the
 electric power detecting circuits 28 and 31, for the measurement display
 or for the control of the inverter, are essential to the general
 uninterruptive power supply. Then, any of new constituent elements is not
 newly added, but those constituent elements are applied thereto, whereby
 the configuration of the circuit can be simplified.
 (Fifth Embodiment)
 While in the above-mentioned first to fourth embodiments, the description
 has been given with respect to the case where the smoothing capacitor 9 is
 provided in order to smooth the voltage of the batteries 8. Then, since
 even when the batteries 8 are removed due to the maintenance of the
 uninterruptive power supply or the exchange of the batteries 8, the same
 voltage as that of the batteries 8 still remains across the smoothing
 capacitor 9 and hence this is dangerous, the electric charges accumulated
 therein needs to be discharged. However, each of the batteries 8 has the
 capacitance component of the capacitor and hence if the voltage of the
 batteries 8 can be smoothed through the capacitance component thereof,
 then the smoothing capacitor 9 can be omitted. In the fifth embodiment,
 the description will hereinbelow be given with respect to a uninterruptive
 power supply including a stepup/stepdown chopper in which the smoothing
 capacitor 9 is omitted.
 FIG. 5 is a circuit diagram, partly in block diagram, showing the
 configuration of a uninterruptive power supply according to the fifth
 embodiment of the present invention.
 In FIG. 5, the same portions as those of the fourth embodiment shown in
 FIG. 4 are designated by the same reference numerals and the description
 thereof is omitted here for the sake of simplicity. As for new reference
 numerals, reference numerals 7b designates a stepup/stepdown chopper
 according to the fifth embodiment, and the stepup/stepdown chopper 7b
 further includes a fuse 32, as one of the switching means, which is
 provided between the batteries 8 and the chopper reactor 10 and which
 serves to carry out the protection against the overcurrent, and diodes 33
 and 34, as the circulation means, which serves to make the current flowing
 due to the energy accumulated in the chopper reactor 10, when melting
 (opening) the fuse 32, circulate to the D.C. intermediate circuit 3.
 As shown in FIG. 5, the battery output portion of the general
 uninterruptive power supply is provided with the fuse 32 for the
 protection against the overcurrent due to the accident or the like. Then,
 when no smoothing capacitor is provided, if the fuse 32 is blown when the
 current is being caused to flow through the chopper reactor 10, then the
 current is intended to be caused to flow continuously due to the energy
 accumulated in the chopper reactor 10, and hence the arc is generated
 across the fuse 32 to cause the calorification, which is dangerous. For
 this reason, the diodes 33 and 34 are provided in order to ensure the path
 through which the current flowing through the chopper reactor 10 is to be
 caused to flow continuously when the fuse 32 has been blown.
 As a result, at the time when the fuse 32 has been blown during the
 discharge of the batteries 8, the current flowing due to the energy
 accumulated in the chopper reactor 10 circulates through the path of the
 D.C. intermediate circuit 3.fwdarw.the diode 34.fwdarw.the chopper reactor
 10.fwdarw.the first free wheel diode 12.fwdarw.the D.C. intermediate
 circuit 3. On the other hand, at the time when the fuse 32 has been blown
 during the charge of the batteries 8, the current of the chopper reactor
 10 circulates through the path of the D.C. intermediate circuit
 3.fwdarw.the second free wheel diode 14.fwdarw.the diode 33.fwdarw.the
 D.C. intermediate circuit 3. Therefore, no arc is generated across the
 terminals of the fuse 32 and also the smoothing capacitor can be omitted.
 Therefore, the maintenance can be safely, readily carried out.
 In this connection, while as the means for cutting off the current path of
 the chopper reactor 10, the description has been given with respect to the
 case where the fuse is blown, this is also applied to the circuit breaker
 or other switches. In addition, the stepup/stepdown chopper 7b which is
 configured as shown in FIG. 5 may also be similarly applied to the first
 to fourth embodiments shown in FIGS. 1 to 4, respectively.
 (Sixth Embodiment)
 While in the above-mentioned fifth embodiment, the description has been
 given with respect to the case where the capacitance component of the
 batteries 8 is so sufficiently large as to be able to smooth the voltage
 of the batteries 8, and hence the smoothing capacitor can be omitted, each
 of the charging current and the discharging current of the batteries 8
 contains therein the ripple components due to the operation of the
 chopper. When no smoothing capacitor is provided, all of the ripple
 components are caused to flow into the batteries 8, and hence if the
 magnitude of each of the ripple components is large, this becomes the
 cause of degrading the batteries 8. In order to reduce each of the ripple
 components, the switching period of the chopper may be shortened or the
 inductance of the chopper reactor 10 may be increased. However, if the
 switching period is shortened, then the electric power loss due to the
 switching will be increased, while if the inductance of the chopper
 reactor 10 is increased, then since when preceeding from the charge to the
 discharge during the service interruption, it takes the discharging
 current of the batteries 8 time to flow by the corresponding electric
 power which needs to be supplied to the load 6, the supply of the electric
 power to the load 6 is stopped, or the capacitance value of the smoothing
 capacitor 4 needs to be increased. Therefore, this becomes expensive. In
 the sixth embodiment, the description will hereinbelow be given with
 respect to a uninterruptive power supply including a stepup/stepdown
 chopper in which the smoothing capacitor can be omitted and also each of
 the batteries can have the long life.
 FIG. 6 is a circuit diagram, partly in block diagram, showing the
 configuration of a uninterruptive power supply according to the sixth
 embodiment of the present invention.
 In FIG. 6, the same portions as those of the fifth embodiment shown in FIG.
 5 are designated by the same reference numerals and the description
 thereof is omitted here for the sake of simplicity. As for new reference
 numerals, reference numerals 10a and 10b, as chopper reactors, designate
 respectively a charging chopper reactor which is provided in the charging
 path leading to the batteries 8, and a discharging chopper reactor which
 is provided in the discharging path leading to the D.C. intermediate
 circuit 3. In this connection, the inductance of the charging chopper
 reactor 10a is set to a large value, while the inductance of the
 discharging chopper reactor 10b is set to a small value.
 As shown in FIG. 6, the chopper reactor is divided into the charging
 chopper reactor 10a and the discharging chopper reactor 10b, and the
 inductance of the charging chopper reactor 10a is set to a large value to
 reduce the ripple components of the charging current, while the inductance
 of the discharging chopper reactor 10b is set to a small value in such a
 way that the discharging current rises rapidly, whereby the smoothing
 capacitor can be omitted and also each of the batteries 8 can have the
 long life.
 In this connection, while in the sixth embodiment 6, the chopper reactor 10
 in the fifth embodiment shown in FIG. 5 is divided into the charging
 chopper reactor 10a and the discharging chopper reactor 10b, this can also
 be similarly implemented in the first to fourth embodiments shown in FIGS.
 1 to 4, respectively.
 As set forth hereinabove, according to the present invention, when the
 input electric power which has been inputted from the A.C. power source
 exceeds the electric power to be limited, the stepup/stepdown chopper is
 operated as the boosting chopper and a part of the electric power which is
 supplied from the inverter to the load is supplied from the batteries
 thereto, thereby suppressing the input electric power from the A.C. power
 source. Therefore, even if the consumed electric power of the load is
 increased, the voltage of the D.C. intermediate circuit is not decreased
 to the level lower than the setting voltage, and hence the input electric
 power from the A.C. power source can be limited to the level equal to or
 lower than the setting electric power.
 In addition, since it is detected on the basis of the voltage detected by
 the D.C. intermediate circuit voltage detecting means that the input
 electric power which has been inputted from the A.C. power source exceeds
 the electric power to be limited, it can be readily detected that the
 input electric power exceeds the electric power to be limited. Also, even
 if the consumed electric power of the load is increased, the voltage of
 the D.C. intermediate circuit is not decreased to the level lower than the
 setting voltage and hence the input electric power from the A.C. power
 source can be limited to the level equal to or lower than the setting
 electric power.
 In addition, since the input electric power is detected by multiplying the
 voltage detected by the D.C. intermediate circuit voltage detecting means
 by the current detected by the current detecting means and also it is
 detected on the basis of the detected electric power that the input
 electric power which has been inputted from the A.C. power source exceeds
 the electric power to be limited, even if the voltage of the A.C. power
 source fluctuates, the input electric power does not exceed the setting
 electric power and hence the input electric power from the A.C. power
 source can be limited.
 In addition, since the input electric power is detected on the basis of the
 voltage detected by the D.C. intermediate circuit voltage detecting means,
 the voltage detected by the A.C. power source voltage detecting means and
 the impedance of the input filter and also it is detected on the basis of
 the detected electric power that the input electric power which has been
 inputted from the A.C. power source exceeds the electric power to be
 limited, the current detecting means becomes unnecessary and hence it is
 possible to obtain an inexpensive uninterruptive power supply.
 In addition, the output voltages of the inverter and the batteries are
 respectively detected and also it is detected on the basis of the sum of
 the output electric power of the inverter and the output electric power of
 the batteries that the input electric power which has been inputted from
 the A.C. power source exceeds the electric power to be limited. Therefore,
 since the constituent elements for the measurement display or the control
 of the inverter are applied to the general uninterruptive power supply
 without adding any of new constituent elements, it can be readily detected
 with the simplified configuration that the input electric power exceeds
 the electric power to be limited. Also, even if the consumed electric
 power of the load is increased, the voltage of the D.C. intermediate
 circuit is not decreased to the level lower then the setting voltage and
 hence the input electric power from the A.C. power source can be limited
 to the level equal to or lower than the setting electric power.
 In addition, since the switching means for the protection against the
 overcurrent is provided between the batteries and the chopper reactor and
 also the stepup/stepdown chopper having the circulation means for causing
 the current flowing due to the energy accumulated in the chopper reactor
 when opening the switching means to circulate to the D.C. intermediate
 circuit is provided, no arc is generated across the terminals of the
 switching means and hence the smoothing capacitor can be omitted.
 Therefore, the maintenance can be safely, readily carried out.
 Furthermore, the stepup/stepdown chopper is provided having, as the chopper
 reactors, the charging chopper reactor provided in the charging path
 leading to the batteries and the discharging chopper reactor provided in
 the discharging path leading to the D.C. intermediate circuit, and the
 inductance of the charging chopper reactor is set to a large value, while
 the inductance of the discharging chopper reactor is set to a small value.
 Therefore, the inductance of the charging chopper reactor is set to a
 large value to reduce the ripple components of the charging current, and
 the inductance of the discharging chopper reactor is set to a small value
 to make the discharging current rise rapidly, whereby the smoothing
 capacitor can be omitted and also each of the batteries can have the long
 life.
 While the present invention has been particularly shown and described with
 reference to the preferred embodiments, it will be understood to those
 skilled in the art that the various changes and modifications will occur
 without departing from the scope and true spirit of the invention. The
 scope of the invention is therefore to be determined solely by the
 appended claims.