JPH01238438A - Uninterruptible power supply device - Google Patents

Abstract

PURPOSE:To prevent battery consumption at the time of power failure using a simple and inexpensive circuit by controlling the operation of an inverter according to an output of a current detecting transformer connected both to the input line of the commercial power supply and the output line of an uninterruptible power supply device. CONSTITUTION:A current detecting transformer 25 is commonly connected to the output line 23 of an uninterruptible power supply device and the input line 24 of the commercial power supply. The output of the current detecting transformer 25 is supplied to a current detection judging circuit 26. If it is judged that no current flows in the current detecting transformer 25, i.e., there is a failure and there is no load in the circuit, a stop signal is delivered from the current detecting judging circuit 26 to an inverter 13.

Description

[Detailed Description of the Invention] "Industrial Application Field" This invention is used as a power supply device for many electrical devices including computer equipment, which can always supply stable power to loads even if the commercial power supply is interrupted. This article relates to uninterruptible power supplies.

"Prior Art" A conventional uninterruptible power supply (hereinafter referred to as UPS) will be explained with reference to the block system diagram shown in FIG.

The commercial power supply power from the terminal 11 is rectified by the rectifier 12,
The rectified output is converted into AC power by an inverter 13 and output to an output terminal 14. The storage battery 6 is charged by electric power from the terminal 11 through the charger 15. During a power outage, power from the storage battery 16 is supplied to the inverter 13 through the backflow prevention diode 17,
3, it is converted into AC power and output.

Commercial power from the terminal 11 is supplied to a power outage detection circuit 19 via a signal isolation transformer 18, and when the power outage detection circuit 19 detects a power outage, it outputs an H level and supplies it to the NAND circuit 21. - The load current of the force output terminal 14 is detected by the current detector 2.
2, and when the detected current is 0 and there is no load, the current detector 22 outputs an H level and supplies it to the NAND circuit 21. If there is a power outage and there is no load, the NAND circuit 21
An in-harc stop signal is output from the output of the inverter 13, and the operation of the inverter 13 is stopped. In this way, you can
In the loaded state, the storage battery 16 is prevented from discharging.

"Problem to be Solved by the Invention" In a UPS, an inverter 13 is constantly operated with DC power obtained by rectifying a commercial power supply or with DC power from a storage battery 16.
The power failure detection circuit 19 and the signal isolation transformer 18 were used only to prevent the inverter 13 from operating without load during a power failure.

As the demand for lower costs for UPSs increases, there is a need to simplify circuits and reduce the number of parts.

"Means for Solving the Problem" According to the present invention, a current detection transformer is provided in common to the output current line of the uninterruptible power supply and the input terminal line of the commercial power supply, and a current flows through the current detection transformer. If the inverter is not running, that is, there is a power outage and there is no load, the current detection and determination circuit detects this, and the detection output stops the operation of the inverter.

"Example" An example of the present invention is shown in FIG. 5 in Figure 1
Parts corresponding to those in the figure are given the same reference numerals. In this invention, a current detection transformer 25 is provided in common to the output current line 23 of the uninterruptible power supply and the input current line 24 of the commercial power supply. The output of the current detection transformer 25 is supplied to the current detection judgment circuit 26, and when no current is flowing through the current detection transformer 25, that is, during a power outage and in a no-load state, the current detection judgment circuit 26 stops the inverter. A signal is output.

The current detection and determination circuit 26 is configured as shown in FIG. 2, for example. The current detection transformer 25 is connected to a comparator 27, the non-inverting input terminal of the comparator 27 is grounded, and the output terminal is connected to a positive power terminal 29 through a resistor 28 and to a negative power terminal 32 through a capacitor 31. The transistor 34 has a collector connected to the power supply terminal 29 and an emitter connected to the power supply terminal 32 .

When a current flows through either of the lines 23 and 24 passing through the current detection transformer 25, a voltage is generated at the output of the current detection transformer 25. This voltage is input to the comparator 27, and when a voltage higher than the + terminal is applied to one terminal of the comparator 27, the output of the comparator 27 becomes L level, and the capacitor 3
Discharge the charge accumulated in 1 (once per cycle)
. The constant of the resistor 28 that charges the capacitor 31 is such that the time constant CR of the capacitor 31 and the resistor 28 is 1 of the current to be detected.
Since the value is selected to be longer than the cycle time, even if there is a no-current period like the current waveform of the rectifier load (for example, the UPS input current waveform shown in FIG. 3), the voltage of the capacitor 31 is equal to the Zener voltage of the Zener diode 33. (Figure 3).

Even if the output of the UPS becomes no-load and no output current flows, the inverter inside the UPS performs no-load operation, so a small amount of UPS input current continues to flow. When a power outage occurs, the UPS input current also disappears, so the output of the comparator 27 becomes H level, the capacitor 31 is charged through the resistor 28, and the voltage gradually increases. When the voltage of capacitor 31 exceeds (Zener voltage of Zener diode 33) + (base-emitter voltage of transistor 34), transistor 34 turns on and generates an inverter stop signal (FIG. 3).

Note that both input terminals of the comparator 27 are voltage-free and the comparator 2
In the case of a comparator in which the output level of the comparator 27 is not stabilized at the H level, a bias voltage R is applied to the input of the comparator 27 as shown in FIG.

−v, × □ may also be applied. In the case of the fourth RI+R2, the output voltage of the current detection transformer 25 is the bias voltage (for example, VC=5V, R,=lOOΩ, R2=
When Ω is higher than -0, IV), it is determined that power is being received or a load current is flowing. Since the output voltage of the current detection transformer 25 is a much larger signal than the bias voltage, the difference in detected current is small.

Diodes 35 and 36 between the input terminals of the comparator 27 are for bypassing an excessive detection voltage signal and protecting the comparator 27.

"Effects of the Invention" According to the present invention, the storage battery discharge that occurs when a power outage occurs while the load device is not in use, such as on holidays,
This can be prevented with a simple and low-cost circuit. As a result, a specific U
The no-load operation prevention circuit that was limited to PSs is now available in regular UPSs.
It can also be installed on the battery, which reduces the number of discharge cycles of the storage battery, and is expected to extend the life of the storage battery.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of an uninterruptible power supply according to the present invention, FIG. 2 is a connection diagram showing a specific example of the current detection judgment circuit 26 in FIG. 1, and FIG. 4 is a connection diagram showing another example of the current detection/judgment circuit 26, and FIG. 5 is a block diagram showing a conventional uninterruptible power supply.

Claims (1)

[Claims] (1) While receiving commercial power, AC power is supplied to the load based on the commercial power supply, and during a commercial power outage, DC power from the storage battery is converted to AC power using an inverter and supplied to the load. In the uninterruptible power supply, there is a current detection transformer that is commonly provided to the output current line of the uninterruptible power supply and the input current line of the commercial power supply, and if no current flows through the current detection transformer, the inverter is stopped. An uninterruptible power supply device comprising a current detection and determination circuit.