JPS63206165A - Uninterruptible power supply - Google Patents

Abstract

PURPOSE:To miniaturize a device and lighten the weight and suppress current, by using a non-insulation type filter circuit, and by changing the degree of a PWM modulation when the current of each line on the output side of an inverter circuit exceeds a constant value. CONSTITUTION:An uninterruptible power supply (UPS device) is composed of a step-up chopper circuit 3 to receive the output from a diode bridge 1, a smoothing capacitor 4, an inverter circuit 5, a battery 8, a charging circuit 7 for the battery, and the like, and the UPS supply power to a load L. A commercial power input terminal and AC output terminals are respectively connected through the respective switch circuits 10a, 10b. The control circuit of the inverter circuit 5 is composed of a current limitint signal circuit 16, a voltage regulating circuit 23, a comparator circuit 26, and the like, and the inverter circuit 5 is PWM-controlled under specified conditions. As a result, when each current on lines on the output side exceeds a constant value, then according to the scale and the direction of the detected current, the modulation degree on the inverter circuit 5 is changed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Title of the Invention (Field of Industrial Application) The present invention relates to an uninterruptible power supply device installed as a countermeasure against a power outage of a commercial power source.

(Prior Art) When a power outage during operation poses a major problem, such as when a computer performs important processing, an uninterruptible power supply (Uninterruptible PottorS) is used.
source: UPs (hereinafter referred to as UPS device) are used.

FIG. 7(a) shows a schematic configuration of such a conventional UPS device. In the figure, the input voltage ■ supplied from the commercial power supply is converted to a DC voltage by the diode bridge 1,
It is smoothed by capacitor 2. This DC voltage is boosted to a second DC voltage by a boost chopper circuit 3, and the boosted voltage is smoothed by a capacitor 4. The inverter circuit 5 includes FETs 5a to 5d for switching and diodes 58 to 5h for reverse voltage absorption connected in parallel to them.
Each of the FETs 5a to 5d is controlled to be turned on or off at predetermined timing by an inverter control circuit (not shown). This on/off control is controlled such that the second DC voltage across the capacitor 4 is PVM-modulated in synchronization with the input voltage V, so that the inverter circuit 5 outputs an AC voltage that is in phase with the input voltage V. The AC voltage is filtered by a filter circuit 6 consisting of an isolation transformer 6a and a capacitor 6b.
As a result, harmonic components of the AC voltage are removed and extracted as an AC output voltage of the UPS device.

The DC voltage output from the diode bridge 1 is also supplied to the battery 8 via the charging circuit 7, and the battery 8 is charged. On the other hand, if the commercial power supply fails, the battery 8
A DC voltage is input to the boost chopper circuit 3 via the diode 9, and an AC output voltage is taken out in the same manner as above.

By the way, when the commercial power supply is normal, the operation of the step-up chopper circuit 3 and the inverter circuit 5 can be stopped, and at this time, the input voltage ■ is directly bypassed to the AC output terminals a and b. Switch circuits 10a and 10b using triacs are provided to enable this.

(Problems to be Solved by the Invention) In the above configuration, the filter circuit 6 includes an isolation transformer 6.
However, the problem is that the isolation transformer 6a is large in size and weight, and is also expensive.

On the other hand, as shown in FIG. 7(b), the reactor 11a.

It is known that the filter circuit 11, which is composed of a capacitor 11b and a capacitor llc and whose input side and output side are not insulated, has the same effect as the filter circuit 6, and is small, lightweight, and inexpensive.

Therefore, consider a case where a filter circuit 11 is provided instead of the filter circuit 6. Now, assume that the commercial power supply is normal, the operation of the boost chopper circuit 3 and the inverter circuit 5 is stopped, the switch circuits 10a and 10b are turned on, and the input voltage ■ is directly output from the output terminals a and b. .

From this state, switch circuits 10a and 10b are turned off,
When switching to operate the boost chopper circuit 3 and the inverter circuit 5, the boost chopper circuit 3 and the inverter circuit 5 activate a control circuit (not shown).

A predetermined operation is started in a short time of 200 μs to 300 μs after startup. However, the switch circuits 10a and 10b
Since the triac uses a triac as a switching element, even if the gate current of the triac is controlled to turn it off, the on state continues until the input voltage V becomes zero.

That is, if the frequency of the input voltage ■ is 50t(z), in the worst case, the ON state will continue for a half cycle (ioIIg).

At this time, since the inverter circuit 5 has already started PWM modulation, a current flows due to the rotation when the FETs 5a and 5b and the FETs 5c and 5d are turned on alternately during the half cycle. That is, if the line on the U side of the commercial power supply is II + 14 and FETs 5b and 5c are on, the current flows through the switch circuit 10a.

Reactor lla, FET5b, diode bridge 1
The V member side diode flows to the V side of the commercial power supply, and the other beam flows through the axle 11a, the diode 5e, and the F side.
ET5c.

The current flows to the reactor 11b, the switch circuit 10b, and the V side of the commercial power supply V, causing the commercial power supply to be short-circuited and causing an excessive current to flow.

In order to prevent this excessive current, it is necessary to delay the start of operation of the inverter circuit 5. However, if this start of operation is delayed, there will be a momentary interruption in the AC output voltage when switching from the commercial power supply side to the inverter circuit side. There were problems that arose.

The present invention solves the above-mentioned problems, and is small, lightweight, and has an uninterrupted system that does not cause instantaneous interruptions! The purpose is to provide a source device.

[Configuration of the Invention (Means for Solving the Problems) Therefore, the present invention provides a current detector for each line on the output side of the inverter circuit, so that when the detected current exceeds a certain value, , the degree of modulation in PIjM (pulse width modulation) of the inverter circuit is changed according to the current value.

(Function) By changing the degree of modulation, excessive current flowing to the output side of the inverter circuit can be suppressed, so there is no need to delay the start of operation of the inverter circuit, and instantaneous interruptions in the AC output voltage can be eliminated.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an uninterrupted i! according to an embodiment of the present invention. power supply ffi
! (hereinafter referred to as UP, S device), the input side of a diode bridge 1 is connected to a commercial power supply via a commercial power supply input terminal, and the output side is connected to a smoothing capacitor 2 and a step-up chopper circuit. The output of the boost chopper circuit 3 is connected to the input of the smoothing capacitor 4 and the inverter circuit 5, while a series circuit of a battery 8 and a diode 9 is connected in parallel with the diode bridge 1. , a charging circuit 7 and a diode 9 are connected in parallel. In addition, each line of the commercial power input terminal and the AC output terminal is connected to a switch circuit 10.
A and 10b are connected to form a bypass line. These points are the same as the configuration in FIG. 7(a).

In this embodiment, each output line of the inverter circuit 5 is connected to an AC output terminal via the primary windings of current transformers 12a and 12b and the filter circuit 11, respectively.

Various devices are connected to this AC output terminal as a load. Here, the boost chopper control circuit 13 is a circuit that controls the boost chopper circuit 3. Resistors 14a, 14b
is for extracting a voltage signal proportional to the load resistance current of the current transformers 12a and 12b, the maximum value selection circuit 15 is a circuit that selects and outputs the higher input voltage, and the current limit signal circuit 16 is For example, it is a circuit in which two Zener diodes are connected in series, and when an input signal exceeds a certain level, it outputs a signal corresponding to the exceeded signal level.

The transformer 17 is for extracting the phase of the AC voltage of the commercial power supply, and the synchronous circuit 18 is a circuit that outputs a sine wave signal synchronized with the AC voltage.

The transformer 19 and the rectifier circuit 20 are circuits that detect the AC output voltage of the inverter, and the voltage setting circuit 21 is a circuit that sets the AC output voltage. The amplifier circuit 22, the voltage adjustment circuit 23, and the adder 24 are circuits for controlling the AC output voltage to a set constant voltage. Triangular wave generation circuit 2
5. Comparison circuit 26 and drive circuit 27 are circuits for PWM controlling inverter circuit 5 under predetermined conditions.

The power outage detection circuit 28 is a circuit that detects an abnormality in the commercial power supply such as a power outage. The switching control circuit 29 determines whether the commercial power supply is normal or abnormal, determines circuit failure based on the output signal of the drive circuit 27, controls on/off switching of the switch circuits 10a and 10b, and controls switching between operation and stop of the drive circuit 27. It is a circuit. The on/off switching of the switch circuits 10a, 10b and the activation/stopping of the drive circuit 27 can be performed forcibly by manual setting, or can be performed automatically when a failure of the commercial power source or the circuit is determined.

Next, the operation of the UPS device of this embodiment configured as described above will be explained. This UPS device always operates the inverter circuit 5 and outputs an alternating current voltage by setting an operation part (not shown), but the switch circuits 10a, 1Ob
You can freely choose whether to directly output commercial power via the

Now, assuming that the setting is made to output commercial power directly, the switching control circuit 29 is connected to the switch circuits 10a and 10b.
While turning on the triac circuits 10a and 10b,
The operation of the drive circuit 27 is stopped. At this time.

The input voltage (2) is applied to the loads via switch circuits 10a and 10b, and the loads, which are various devices, are operated by commercial power.

On the other hand, the DC voltage taken out from the diode bridge 1 is smoothed by a capacitor 2 and input to a boost chopper circuit 3. The boost timipper control circuit 13 includes a current detector 3
Switching control of the FET 3b is performed based on the current of the accelerator 3a and the output voltage of the step-up chopper circuit 3 detected by d. Thereby, the boost chopper circuit 3 boosts the input DC voltage to a constant voltage and applies it to the capacitor 4 and the inverter circuit 5.

At this time, since the operation of the drive circuit 27 is stopped,
The inverter circuit 5 does not operate, and no power is supplied from the inverter circuit 5 to the load. Note that at this time, the battery 8 is charged by the charging circuit 7.

Next, if the operation unit is set to operate the inverter circuit 5 to output an alternating current voltage, each circuit operates as follows. Namely.

The synchronization circuit 18 outputs a sine wave signal synchronized with the input voltage V. The amplifier circuit 22 amplifies the deviation between the set voltage of the voltage setting circuit 21 and the AC output voltage of the inverter, and outputs a deviation signal.

The voltage adjustment circuit 23 outputs a sine wave signal Vc synchronized with the input voltage V at a voltage level proportional to the deviation signal.

The adder 24 inputs and adds this sine wave signal Vc and its current limit signal vb, and outputs the result as a voltage adjustment signal Vd. Note that during steady operation, the current limit signal vb output from the current limit signal circuit 16 is output at 0 level.

The triangular wave generation circuit 25 outputs a triangular wave signal having a constant voltage and a constant frequency such as 10 KHz.

The comparison circuit 26 uses the triangular wave signal and the voltage adjustment signal Vd.
A predetermined PVM signal Ve is output by comparing the values. This PVM signal Ve is a known signal in which each pulse width of a constant period pulse signal changes depending on the instantaneous value of the voltage adjustment signal Vd, which is a sine wave signal. Drive circuit 2
7 indicates each F of the inverter circuit 5 according to the PWM signal Ve.
The ETs 5a to 5d are controlled on and off in a predetermined sequence.

The inverter circuit 5 outputs an alternating current voltage under the above control, and the alternating current voltage is outputted to a load via the filter circuit 11. The amplitude and phase of this AC output voltage are the input voltage V
will match. As a result, the load operates in the same way as in the case of commercial power supply.

At this time, the voltage taken out from the load resistors 14a, 14b of the current transformers 12a, 12b according to the load current is input to the maximum value selection circuit 15. Here, when the load current flows from the inverter circuit 5 to the load, the current transformers 12a and 12b are connected so that the above two voltages have the same polarity, and the maximum value selection circuit 15 selects the input voltage. The higher voltage among them is output as the current detection signal Va. The current limit signal circuit 16 inputs the current detection signal Va, and as shown in FIG. 2, when the current detection signal Va exceeds a certain value in the positive or negative direction, it limits the current according to the signal value. Outputs signal vb. At this time, which is during steady operation, the current limit signal vb is 0, as described above.

Next, a description will be given of the operation when a voltage drop in the input voltage V or a power outage occurs while the switch circuits 10a and 10b are currently turned on and the operation of the inverter circuit 5 is stopped.

The power failure detection circuit 28 detects the input voltage V via the transformer 17, and outputs a power abnormality signal when the voltage falls below a certain level. When the switching control circuit 29 receives this power supply abnormality detection signal.

While the gate signals to the triacs of the switches 10a and 10b are turned off, the drive circuit 27 is activated. As a result, the inverter circuit 5 operates and outputs a predetermined AC output voltage.

At this time, triacs are used in the switch circuits 10a and 10b as explained in FIG. 7(a).

After the triac gate signal is turned off to turn off the switch circuits 10a, 10b, it remains on for a half cycle of the input voltage V in the worst case.

Then, as described above, when the line on the U side of the commercial power source becomes II + 11, an excessive current 11 tends to flow from the switch circuit 10a toward the inverter circuit 5, as shown in FIG.

At this time, a voltage Vl corresponding to the current is output from the current transformer 12a.
is output, and the voltage is input to the maximum value selection circuit 15. On the other hand, since only a steady current according to the load is flowing in the line on the current transformer 12b side, the maximum value selection circuit 15 converts the voltage v1 output from the current transformer 12a into the current detection signal V
Output as a. At this time, the current limit signal circuit 16
According to the characteristics shown in FIG. 2, a current limit signal vb is output when Va exceeds a set value.

When the electric current 1 shown in FIG. 3 flows, each of the above voltages v1
．． vb is If + as shown in FIG. 4(a), respectively.
11 is output. This causes the adder 24 to output the signal V
By adding the current limit signal vb to c, the voltage adjustment signal Vd
increase the level of. The comparison circuit 26 changes the pulse width of each pulse of the PVM signal in accordance with the rise of the voltage adjustment signal Vd and outputs the same. The drive circuit 27 turns on the FEETs 5a and 5d using the PWM signal, while turning on the FETs 5b and 5c at the opposite timing, that is, during the period in which the FETs 5a and 5d are turned off. The fact that the pulse width of the above PVM signal changes is that Pl in the inverter circuit 5
i! This is because the modulation degree in M modulation changes, and this changes the current flowing through FETs 5a to 5d. When the current limit signal vb becomes positive, the currents Ia and Id of the FETs 5a and 5d increase as shown in FIG. 4(a).
increases, and the currents Ib and I of FETs 5b and 5c respectively
c is controlled to decrease.

Since the current Il flows through the FETs 5b and 5c as explained in FIG. 7(a), it is suppressed thereby, and an excessive current is prevented from flowing.

On the other hand, the currents Ia and Id of FETs 5a and 5d are controlled to increase, but since current 1 is flowing in the opposite direction to current 1, current 11 acts to decrease. At this time, a predetermined voltage is applied to the load from the commercial power source via the switch circuits 10a and 10b.

On the other hand, when the switch circuits 10a and 10b are turned off during a half cycle period of 41 + TI on the V side of the commercial power supply, an excessive current tends to flow in the direction indicated by I2 in FIG.

In this case, the voltage v2 is output from the current transformer 12b, this voltage v2 is input to the maximum value selection circuit 15 with negative polarity as shown in FIG. The signal vb is output as negative.

At this time, contrary to the above, the current I of FETs 5a and 5d
a and Id are decreased and the currents Ib and Ic of FETs 5b and 5c are controlled in the direction of increasing, so that the current I2 is suppressed from becoming excessively large, as described above.

With this operation, when the switch circuits 10a and 10b are turned off and the inverter circuit 5 is operated, the currents II and I2 flowing in the opposite direction are suppressed in this way, so there is no need to delay the activation of the inverter circuit. Therefore, power can be stably supplied to the load without causing momentary interruption of the AC output voltage.

In addition, when the abnormality in the commercial power supply recovers, the power failure detection circuit 28
The power supply abnormality detection signal is turned off, and at this time, the switching control circuit 29 turns on the switch circuits 10a and 10b and stops the operation of the inverter circuit 5. In this case, the switch circuits 10a and 10b are turned on and the inverter circuit 5 starts operating almost simultaneously, so that problems such as instantaneous interruptions and overcurrent do not occur.

By the way, during the operation of the inverter circuit 5, an excessive load current may flow due to a failure of a device that causes a loud noise. For example, as shown in FIG.
When the current transformers 13a and 13b try to flow, voltages Vl and V2, both positive and equal, are inputted to the maximum value selection circuit 15 from the current transformers 13a and 13b. At this time, the current limit signal circuit 16 outputs a positive current limit signal vb.

Since the current flow 3 to the load is the current Ib, Ic flowing from the FETs 5b, 5c, the load current I3 to the load is suppressed.

In addition, if an excessive load current I4, which is the opposite of the above, is about to flow during a certain half cycle period, the voltages Vl and V2 become negative as shown in FIG. 4(d), and the current limit signal vb becomes negative. As a result, the currents Ia of FETs 5a and 5d become negative,
Id.

In other words, the load current flow 4 is suppressed.

By the way, by setting the operating section, when the commercial power supply is normal, the switch circuits 10a and 1Ob can be turned off and the inverter circuit 5 can be operated. In this case, the switching control circuit 29 controls the P output from the drive circuit 27.
An abnormality in the νM signal is detected, and when the abnormality is detected, the operation of the inverter circuit 5 is stopped and the switch circuits 10a and 10b are turned on.

As a result, in the event of a circuit failure, power is automatically switched from the commercial power source to the load.

As described above, in this embodiment, current transformers 12a and 12b are provided on the output side of the inverter circuit 5 to detect current, and when each current in the output side line of the inverter circuit 5 exceeds a certain value. At this time, the degree of modulation in the inverter circuit 5 is changed depending on the magnitude and direction of the detected current. Due to this.

When switching off the switch circuits 10a and 10b and switching to operation of the inverter circuit 5, the switch circuits 10a and 10
Since the excessive current flowing back from the b side to the inverter circuit 5 is suppressed, there is no need to delay the operation of the inverter circuit 5 for a certain period of time as in the conventional case, so power can be supplied to the load without momentary interruption. Can be done.

Further, when the load current increases abnormally, the excessive current is suppressed, thereby improving safety.

In this embodiment, the voltages Vl and V2 detected by the current transformers 12a and 12b are input to the maximum value selection circuit 15 to select one of them, but as shown in FIG.
Current limit signal circuits 16a and 16b are provided, and the voltages Vl and V2 are inputted to each of the current limit signal circuits 16a and 16b.
, 16b may be configured to input each output signal to the adder 24, and the same operation can be achieved.

Furthermore, in this embodiment, when switching between the commercial power supply side and the inverter circuit 5 side, the operation of the inverter circuit 5 is started and stopped. However, as shown in FIG. 30a and 30b are connected to the output side of the filter circuit 11, while the break contact 3 is connected to the output side of the filter circuit 11.
0c and 30d are connected to a bypass line from a commercial power source to form switch circuits 31a and 31b.

A circuit that performs the above switching using a relay 30 is known. In this case, when extracting AC voltage from the inverter circuit 5, the relay 30 is energized.

The make contacts 30a and 30b are turned on and the break contacts 30c and 30d are turned off.On the other hand, when switching to the commercial power source side, the relay 30 is de-energized.

At this time, the make contacts 30a and 30b open first, and then the break contacts 3Qc and 30d close, causing a momentary disconnection. Therefore, triacs 32a and 32b are attached in parallel to each break contact 30c and 30d, and when the relay 30 is turned off, the switch circuits 31a and 3
By turning on 1b, the above instantaneous interruption can be eliminated.

Furthermore, when switching from the commercial power supply side to the inverter circuit 5 side, the relay 30 is energized to bring it to the above-mentioned initial state, but at this time, the triacs 32a and 32b are turned on during the period when the make contacts 30a and 3Qb are closed, and the relay 30 is completely turned on. Switch to the inverter after it has been activated. As a result, the above-mentioned switching can be performed without momentary interruption, as in the case described above.

In addition, by inserting a reactor on the commercial power input side of the diode bridge 1 in FIG. 1, it is possible to further reduce the excessive current flowing backward from the switch circuits IQa, 10b to the inverter circuit 5 side, and to change the waveform of the input current. Distortion can be reduced. Further, in the above embodiment, an example of a single-phase alternating current UPS device is shown, but a three-phase alternating current UPS device can be configured in the same way.

[Effects of the Invention] As described above, according to the present invention, the structure is made compact and lightweight by using a non-insulated filter circuit, and the current of each line on the output side of the inverter circuit is detected and the current is Since the degree of modulation in the PWM modulation of the inverter circuit is changed to suppress the current when it exceeds a certain value, there is no need to delay the start of operation of the inverter circuit, and momentary interruptions can be eliminated. Furthermore, by controlling the current to be suppressed, it is also possible to suppress an abnormal increase in the load current.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an uninterruptible power supply according to an embodiment of the present invention, Fig. 2 is a graph showing the input/output characteristics of the current limit signal circuit, and Fig. 3 is an explanatory diagram of the current flowing through the inverter circuit. , Fig. 4 is an explanatory diagram showing the overcurrent suppression operation, Fig. 5 is a block diagram showing another embodiment for current limiting, and Fig. 6 is an explanatory diagram showing another embodiment for current limiting. FIG. 7(a) is a block diagram of a conventional uninterruptible power supply, and FIG. 7(b) is a circuit diagram of a non-insulated filter circuit. 1... Diode bridge, 2, 4... Capacitor, 3... Boost chopper circuit, 5... Inverter circuit, 5a to 5d -FET, 5e to 5h, 9-... Diode, 6.11. ... Filter circuit, 7... Charging circuit, 8... Battery, 10a, 10b, 31a, 3
1b - switch circuit, 12a, 12b... current transformer,
13... Boost chopper control circuit, 14a, 14b.
...Resistance, 15...Maximum value selection circuit, 16.16a,
16b...-Current limit signal circuit, 17.19-...
Transformer, 18... synchronous circuit, 20... rectifier circuit. 21... Voltage setting circuit, 22... Amplification circuit, 23.
... Voltage adjustment circuit, 24 ... Adder, 25 ... Triangular wave generation circuit, 26 ... Comparison circuit, 27 ... Drive circuit, 28 ... Power failure detection circuit, 29 ... Switching control circuit ,
30... Relay. 30a, 30b...make contact, 30c, 30d
...Break contacts, 32a, 32b... Triac. Figure 2 Figure 3 Figure 4 Figure 5 Figure 1b Figure 6

Claims (1)

[Claims] an inverter circuit that inputs a commercial power source, extracts a DC voltage, converts the DC voltage into an AC voltage through switching control using pulse width modulation, and outputs it via a reactor; and switches between the output of the inverter circuit and the commercial power source. In an uninterruptible power supply equipped with a switch circuit,
A current detector detects the current of each line on the output side of the inverter circuit, and controls the degree of modulation in the pulse width modulation according to the maximum current value of each detected current, and controls the degree of modulation of each line on the output side. An uninterruptible power supply characterized by comprising: current limiting means for suppressing current.