JP2002112470A - Off-line ups system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an off-line UPS system which can prevent deteriorated contacts, welded contacts, and broken semiconductor elements in a relay. SOLUTION: This off-line UPS system has an AC/DC converter 5, a battery 6, a DC/AC inverter 7, a bypass circuit 3, a switch 4 to selectively output ac voltage from the bypass circuit 3 or from the DC/AC inverter 7, an output terminal 8 to supply the ac voltage selected by the switch 4, and a control circuit 9 which monitors the ac voltage inputted from the commercial ac power supply 1 and throw the switch 4 from the bypass circuit 3 to the DC/AC inverter 7 when the inputted ac voltage drops. The control circuit 9 has an output current detector to check the output current at the output terminal 8 and hold the switch 4 thrown to the bypass circuit 3 when the ac input voltage drops and the output current is an over current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an offline UPS.
(Uninterruptible Power Supply) system.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing an example of a conventional off-line UPS system. 3, the offline UPS system 1 includes a power switch 2, a bypass circuit 3, an output switching relay switch 4, an AC / DC converter 5, a battery 6, a DC / AC inverter 7, an output terminal 8, and a control circuit 9. . This off-line UPS system is different from the on-line system in which inverter power is supplied at both a normal time and a power failure, and outputs an AC voltage of the commercial AC power supply 10 at a normal time and a DC /
This is an off-line uninterruptible power supply that switches so as to output an AC voltage from the AC inverter 7.

A commercial AC power supply 10 is supplied to a contact 4 b of an output switching relay switch 4 via a power supply switch 2 and a bypass circuit 3, and is applied to an AC / DC converter 5. The DC voltage from the battery 6 is DC / A
The voltage is converted into an AC voltage by the C inverter 7 and supplied to the contact 4 c of the output switching relay switch 4.

The control circuit 9 comprises, for example, a microcomputer, monitors the input voltage from the commercial AC power supply 10 applied to the voltage monitoring port P1 via the power switch 2, and outputs the output switching relay switch 4 according to the state of the input voltage. A control signal for switching and controlling the common terminal 4a is output from the output port P2.

In the above configuration, during normal operation, the control circuit 9 switches the common terminal 4a of the output switching relay switch 4 to the contact 4b side based on detection of the input voltage from the commercial AC power supply 10. Therefore, the AC voltage of the commercial AC power supply 10 is supplied to the output terminal 8 through the bypass circuit 3 and the output switching relay switch 4. The battery 6 has an AC / D voltage of the commercial AC power supply 10.
The battery is charged by being converted into a DC voltage by the C converter 5 and applied.

On the other hand, when the commercial AC power supply 10 fails, the control circuit 9 detects that the input voltage from the commercial AC power supply 10 has dropped, and switches the common terminal 4a of the output switching relay switch 4 to the contact 4c side. Control. As a result, the DC voltage of the battery 6 is
The AC voltage converted by the / AC inverter 7 is supplied.

FIG. 4 is a flowchart showing the above operation. First, the control circuit 9 converts the input voltage from the commercial AC power supply 10 into a monitoring voltage level (step S2).
1) Then, the input voltage value Vin is confirmed (Step S2)
2). Next, it is determined whether or not the input voltage value Vin is equal to or more than the threshold value Vth (Vth <Vin) (Step S).
23).

If the answer to step S23 is yes, the control circuit 9 sets the output switching relay switch 4 to the bypass circuit 3
Side (step S24), and the commercial operation of supplying the AC voltage of the commercial AC power supply 10 to the output terminal 8 is performed (step S25).

On the other hand, if the answer to step 23 is no (for example, if the input voltage value Vin is, for example,
Control circuit 9 switches the output switching relay switch 4 to the DC / AC inverter 7 side (step S26), and changes the DC voltage of the battery 6 to D.
The AC voltage converted by the C / AC inverter 7 is output to the output terminal 8
(Step S27).

As described above, the off-line UPS system performs the commercial operation of supplying the AC voltage from the commercial AC power supply 10 to the output terminal 8 in a normal state, and performs the inverter operation of supplying power from the DC / AC converter 7 in the event of a power failure. Work as an off-line uninterruptible power supply.

[0011]

The above-mentioned offline UP
In the S system, an overcurrent may occur due to an inrush current of a load (not shown) connected to the output terminal 8 or an output short circuit. When such an overcurrent occurs, the input voltage drops due to the influence of the power supply impedance. As a result, the control circuit 9 detects the drop in the input voltage and switches the DC / AC inverter 7 from the commercial operation by the commercial AC power supply 10. Switch to inverter power supply.

However, if the output switching relay switch 4 is switched while an overcurrent is flowing, an arc or chattering occurs between the contacts, thereby causing the contacts of the output switching relay switch 4 to deteriorate or to be welded. Sometimes. In addition, the arc between the contacts causes the commercial AC power supply 10
However, there is a problem that a short circuit state occurs with the DC / AC inverter 7, which may cause a breakdown of a semiconductor element included in the DC / AC inverter 7.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an off-line UPS system for preventing the deterioration and welding of a relay contact and the destruction of a semiconductor element in view of the above-mentioned problems.

[0014]

In view of the above-mentioned object,
An off-line UPS system according to the present invention includes an AC / DC converter for converting an AC voltage from a commercial AC power supply into a DC voltage, a battery charged with the DC voltage from the AC / DC converter, and a DC voltage from the battery. DC / AC inverter, a bypass circuit for bypassing an AC voltage from a commercial AC power supply, switch means for selectively outputting an AC voltage from the bypass circuit and an AC voltage from the DC / AC inverter, and a switch means Monitoring the AC input voltage from the commercial AC power supply and the output terminal for supplying the AC voltage selected in the above step, and when detecting a decrease in the AC input voltage, switches the switch means from the bypass circuit side to the DC / AC inverter side. And a control circuit for switching control. The control circuit includes output current detection means for detecting an output current at the output terminal, and operates so as to maintain the switch means on the bypass circuit side when the AC input voltage decreases and the output current is in an overcurrent state.

Accordingly, it is possible to prevent deterioration and welding of the contacts of the switch means and breakage of the semiconductor element of the DC / AC converter.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing an embodiment of an offline UPS system according to the present invention. In FIG. 1, the same components as those of the conventional device of FIG.

The offline UPS system shown in FIG.
In addition to monitoring the input voltage of the commercial AC power supply 10 using the same components as in the conventional system of FIG. 3, the control circuit 9 monitors the output current flowing through the output terminal 8, and as an output switching condition, in addition to the abnormal input voltage, It has a feature in the configuration to which the output overcurrent is added.

That is, the control circuit 9 has a current monitoring port P3 as output current detecting means for monitoring the output current flowing to the output terminal 8.

In the above-described configuration, during normal operation, the control circuit 9 moves the common terminal 4a of the output switching relay switch 4 as the switch means to the contact 4b side based on detection of the input voltage and the output current within the normal range. Switching and maintaining. Therefore, the output terminal 8 is connected to the bypass circuit 3,
An AC voltage of the commercial AC power supply 10 is supplied via the output switching relay switch 4.

On the other hand, when the output current from the output terminal 8 is in an overcurrent state, the control circuit
At the same time, it is detected at 3 that the output current is in an overcurrent state, and at the same time, the voltage monitoring port P1 detects that the input voltage has dropped due to the influence of the power supply impedance as described above. In this case, the control circuit 9 does not switch the common terminal 4a of the output switching relay switch 4 to the contact 4c side, but maintains the common terminal 4a at the contact 4b side. As a result, the commercial operation in which the AC voltage of the commercial AC power supply 10 is supplied to the output terminal 8 is maintained.

When it is detected that the input voltage from the commercial AC power supply 10 has dropped and the output current is not in an overcurrent state (for example, during a power failure), the control circuit 9 Common terminal 4a of output switching relay switch 4
To the contact 4c side. As a result, the DC voltage of the battery 6 is supplied to the output terminal 8 by the DC / AC inverter 7.
Is supplied.

FIG. 2 is a flowchart showing the operation of the above-mentioned offline UPS system. First, the control circuit 9
Converts the input voltage from the commercial AC power supply 10 into a monitoring voltage level (step S1), and then converts the input voltage value V
Check in (step S2). Next, the input voltage value Vin
Is greater than or equal to a threshold value Vth (Vth <Vin) (step S3).

If the answer to step 3 is no (that is, the input voltage is low at the time of a power failure or the like), then the control circuit 9
Converts the output current at the output terminal 8 into a monitoring current level (step S4), and then outputs the output current value Iout
Is confirmed (step S5). Next, the output current value Iout
Is greater than or equal to a threshold value Ith (Ith <Iout) (step S6).

If the answer to step S6 is yes (ie, an output overcurrent state), or if the answer to step S3 is yes, the control circuit 9 switches the output switching relay switch 4 to the bypass circuit 3 side and maintains it ( Step S7),
The commercial operation of supplying the AC voltage of the commercial AC power supply 10 to the output terminal 8 is performed (step S8).

On the other hand, if the answer to step 6 is NO, the control circuit 9 switches the output switching relay switch 4 to the DC / AC inverter 7 side (step S9), and
An inverter operation for supplying an AC voltage obtained by converting the DC voltage by the DC / AC inverter 7 to the output terminal 8 is performed (step S10).

As described above, the off-line UPS system performs the commercial operation of supplying the AC voltage from the commercial AC power supply 10 to the output terminal 8 at the time of normal operation and overcurrent, and operates the output switching relay switch 4 at the time of power failure. The switching operation is performed to operate as an uninterruptible uninterruptible power supply for performing an inverter operation of supplying power from the DC / AC converter 7. Therefore, at the time of an overcurrent, the output switching relay switch 4 does not perform the switching operation, so that it is possible to prevent deterioration and welding of the contacts of the output switching relay switch 4 and destruction of the semiconductor element of the DC / AC converter 7.

As described above, the embodiments of the present invention have been described, but the present invention is not limited thereto, and various modifications and applications are possible.

For example, in the above-described embodiment, a relay switch is used as a switch for selectively outputting the AC voltage from the bypass circuit 3 and the AC voltage from the DC / AC inverter 7, but other switches are used. Elements can also be used.

The off-line UPS system of the present invention further comprises an overload protection device, for example, 110
Stop UPS operation at ~ 120% overload power, 4
At the time of an output overcurrent of 00 to 600%, the commercial operation can be maintained.

[0030]

According to the present invention, it is possible to prevent the deterioration and welding of the contacts of the switch and the destruction of the semiconductor element of the DC / AC converter at the time of overcurrent.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of an offline UPS system according to the present invention.

FIG. 2 is a flowchart showing an operation of the offline UPS system of FIG. 1;

FIG. 3 is a circuit diagram showing an example of a conventional off-line UPS system.

FIG. 4 is a flowchart showing an operation of the offline UPS system of FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Commercial AC power supply 3 Bypass circuit 4 Output switching relay switch (switch means) 5 AC / DC converter 6 Battery 7 DC / AC inverter 8 Output terminal 9 Control circuit P3 Current monitoring port (Output current detection means)

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Koichi Hirao 1-11-15 Higashi Gotanda, Shinagawa-ku, Tokyo Inside the Densei Lambda Co., Ltd. (72) Inventor Shinobu Ito 1-11 Higashi-Gotanda, Shinagawa-ku, Tokyo No. 15 Denpa Building Densei Lambda Co., Ltd. (72) Inventor Masayuki Kato 1-11-15 Higashi Gotanda, Shinagawa-ku, Tokyo Fukuda Building Densai Lambda Co., Ltd. F term (reference) 5G015 FA02 GA06 HA04 HA13 JA10 JA32 JA35 JA53 JA55

Claims (1)

[Claims] 1. An AC / DC converter for converting an AC voltage from a commercial AC power supply into a DC voltage, a battery charged with the DC voltage from the AC / DC converter, and a DC voltage from the battery converted to an AC voltage. DC to convert
/ AC inverter, a bypass circuit for bypassing the AC voltage from the commercial AC power supply, switch means for selectively outputting the AC voltage from the bypass circuit and the AC voltage from the DC / AC inverter, and the switch means Monitoring the AC input voltage from the commercial AC power supply and the output terminal for supplying the AC voltage selected in the above step, and when detecting a decrease in the AC input voltage, switches the switch means from the bypass circuit side to the DC / DC An off-line UPS system having a control circuit for switching control to an AC inverter side, wherein the control circuit includes output current detecting means for detecting an output current at the output terminal, wherein the AC input voltage is reduced and the output current is reduced. In the overcurrent state, the switch means is operated so as to be maintained on the bypass circuit side. Offline UPS system.