JPH0555739U - AC uninterruptible power supply - Google Patents

Abstract

(57) [Abstract] [Purpose] To prevent malfunction due to inrush current generated when switching from bypass circuit power supply to inverter power supply. [Switching] Switching between the output overcurrent detection circuit 9 and the power supply circuit changeover switch circuit 7 and output from the output overcurrent detection circuit 9 to the power supply circuit changeover switch circuit 7 when switching from bypass circuit power supply to inverter power supply A signal supply blocking circuit 10 that blocks the supply of signals is provided. The signal supply blocking circuit 10 does not operate while the inverter power supply is being performed. Further, an inverter output voltage detection circuit 11 is provided which detects the inverter output voltage during power feeding of the inverter and outputs a switching signal to the power feeding circuit changeover switch circuit 7 when the amount of voltage drop exceeds a predetermined value.

Description

[Detailed description of the device]

[0001]

[Industrial application]

 The present invention relates to improvement of an AC uninterruptible power supply.

[0002]

[Prior Art]

 Conventionally, the AC uninterruptible power supply has been configured as shown in FIG. 3, for example. In the figure, 1 is an AC input terminal connected to a commercial power source, 2 is an AC power input terminal connected to a commercial power source, 3 is a rectifier circuit for rectifying an AC input, and 4 is a storage battery that is floatingly charged by the output of this rectifier circuit. Reference numeral 5 denotes an inverter that converts DC power from the rectifier circuit 3 into AC power when the commercial power supply is not interrupted, and outputs DC power from the storage battery 4 to AC power when the commercial power supply fails, and 6 is connected to the AC input terminal 1 described above. An AC bypass circuit, 7 is a power supply circuit switching switch circuit for switching the AC power of the inverter 5 and the bypass circuit 6 and outputting it to the load 12. The power supply circuit changeover switch circuit 7 always selects the inverter power supply, switches the inverter power supply from the inverter 5 to the bypass circuit power supply from the bypass circuit 6 according to the switching signal, and switches from the bypass circuit power supply to the inverter circuit according to the release signal. Switch to power supply. Reference numeral 8 is a current transformer, 9 is an output overcurrent detected by the output from this current transformer, and outputs a switching signal to the changeover switch circuit 7, and when the output overcurrent state returns to a normal state, the release signal is output. Is an output overcurrent detection circuit for outputting.

In the power supply device of FIG. 3, AC power is constantly supplied from the inverter 5 to the load 12 through the power supply circuit changeover switch circuit 7, and the inverter 5 is turned on when the load 12 is turned on or when the load 12 suddenly changes. When an output overcurrent occurs in the output of the switch 2, the changeover switch circuit 7 is switched and controlled by the changeover signal from the output overcurrent detection circuit 9, and the bypass circuit 6 supplies the AC power to the load 12. When the output overcurrent detection circuit 9 detects that the output overcurrent has recovered to the steady value or less and a release signal is output from the circuit 9, the switching switch circuit 7 automatically returns to the original state. Restore inverter power supply.

[0004]

In the above conventional AC uninterruptible power supply, as shown in FIG. 4, when the power supply circuit is switched from the bypass circuit 6 to the inverter 5 after the output overcurrent is restored to the steady state. When the inverter peak voltage Ei is larger than the bypass peak voltage Eb, the inrush current Im flows into the load 12. When this inrush current Im is larger than the overcurrent reference value and is detected as an output overcurrent, a switching signal from the output overcurrent detection circuit 9 causes the power supply circuit changeover switch circuit 7 to perform a switching operation and a bypass circuit from the bypass circuit 6. Switch to power supply. In the bypass circuit power supply, the load current is already below the overcurrent detection value, so the output overcurrent detection circuit 9 outputs the release signal to the power supply circuit changeover switch circuit 7 again, and the inverter power supply is started. If the inrush current generated when the inverter power supply is restarted is smaller than the overcurrent reference value, the inverter power supply will be continued, and if the inrush current is larger than the overcurrent reference value, the same power supply circuit as above will be used again. Will be repeated. If such switching of power supply is repeated, the life of the semiconductor elements and the magnet switch circuit that constitute the power supply circuit changeover switch circuit 7 will be shortened, and the inverter output and the bypass circuit output will be asynchronous during repeated switching operation. In that case, there is a problem that the power supply to the load 12 is momentarily cut off.

An object of the present invention is to provide a load circuit without repeating the switching operation by the power supply circuit changeover switch circuit even if there is a voltage difference between the outputs of both parties when the power supply circuit is switched from the bypass circuit to the inverter. An object of the present invention is to provide an AC uninterruptible power supply device capable of stably supplying power and extending the life of a changeover switch circuit.

[0006]

[Means for Solving the Problems]

 In order to solve the above problems, the AC uninterruptible power supply of the present invention is charged with a rectifier circuit 3 for rectifying AC power from a commercial power source and an output of the rectifier circuit 3, as shown in FIG. Storage battery 4, a rectifier circuit 3 or an inverter 5 that converts the DC output of the storage battery 4 into an AC output and outputs the AC power, a bypass circuit 6 that supplies AC power from a commercial power source, and always select inverter power supply. Inverter power supply from the inverter 5 is switched to the bypass circuit power supply from the bypass circuit 6 according to the switching signal, and is switched from the bypass circuit power supply to the inverter power supply according to the release signal. It is provided with an output overcurrent detection circuit 9 that outputs a switching signal to the power supply circuit changeover switch circuit 7 when detected, and outputs a release signal when the output overcurrent state returns to a steady state. A signal that blocks the input of the switching signal output from the output overcurrent detection circuit 9 to the power supply circuit changeover switch circuit 7 when switching from bypass circuit power supply to inverter power supply for the purpose of improving the AC uninterruptible power supply It is provided with a supply blocking circuit 10 and an inverter output voltage detection circuit 11 which detects the output voltage of the inverter 5 during power feeding of the inverter and outputs a switching signal to the power feeding circuit changeover switch circuit 7 when the amount of voltage drop exceeds a predetermined value. It is characterized by

[0007]

[Action]

 Since the AC uninterruptible power supply of the present invention is provided with the signal supply blocking circuit 10, when the power feeding circuit changeover switch circuit 7 automatically returns from the bypass circuit power feeding to the inverter power feeding, the output of the inverter 5 and the bypass circuit 6 are provided. Even when a large inrush current is generated due to the voltage difference from the output of the power supply circuit and the switching signal is output from the output overcurrent detection circuit 9, the power feeding circuit switching switch circuit 7 does not perform the switching operation. As a result, the repeated switching operation of the power supply circuit changeover switch circuit 7 is suppressed, the power supply to the load is performed stably and favorably, and the life of the power supply circuit changeover switch circuit 7 is extended. Further, the inverter output voltage detection circuit 11 monitors the output voltage of the inverter in order to cope with the case where a true output overcurrent occurs while the signal supply blocking circuit 10 is operating. When an output overcurrent occurs, the output voltage of the inverter drops significantly. Therefore, when the inverter output voltage detection circuit 11 detects a large drop in the output voltage of the inverter, the switching signal is output regardless of the signal supply blocking circuit 10. Is output to switch the inverter power supply to the bypass circuit power supply. Therefore, even if the signal supply blocking circuit 10 is provided, the power feeding circuit can be switched over in response to the output overcurrent to the load.

[0008]

【Example】

 Embodiments of the present invention will be described below with reference to the drawings. Since FIG. 1 shows the embodiment, the same parts as those of the apparatus of FIG. 3 are designated by the same reference numerals to simplify the description. The output overcurrent detection circuit 9, like the output overcurrent detection circuit of FIG. 1, detects the output current to the load from the output from the current transformer 8 and compares it with a predetermined overcurrent reference value. When it is larger than the reference value, a switching signal for controlling the switching of the selector switch circuit 7 is output, and when the output current becomes smaller than the overcurrent reference value, a release signal is output. Reference numeral 10 is a signal supply blocking circuit connected between the output terminal of the output overcurrent detection circuit 9 and the control input terminal of the power supply circuit changeover switch circuit 7. In this signal supply blocking circuit 10, the switching signal output from the output overcurrent detection circuit 9 is sent to the power supply circuit changeover switch circuit 7 only when the power supply circuit changeover switch circuit 7 switches the power supply from the bypass circuit power supply to the inverter power supply. Block input. The signal supply blocking circuit 10 does not block the switching signal output from the output overcurrent detection circuit 9 from being input to the power feeding circuit switching switch circuit 7 after switching to the inverter power feeding.

FIG. 2 shows an example of a specific structure of the output overcurrent detection circuit 9 and the signal supply blocking circuit 10. In FIG. 2, 91 is a rectifier for full-wave rectifying the output of the current transformer 8, 92 is a reference voltage signal generator for generating a reference voltage signal corresponding to an overcurrent reference value, and 93 is a comparator. The signal supply blocking circuit 10 includes a timer driving circuit 101, a timer circuit 102, an inverting circuit 103, an AND circuit 104, and an output terminal 105. The timer drive circuit 101 is activated to the timer circuit 102 when the cancel signal (switch signal to inverter power supply) output from the comparator 93 (AND circuit 104) is output when switching from bypass circuit power supply to inverter power supply. Output a signal. When activated by the activation signal, the timer circuit 102 outputs a signal and starts counting a preset timer time. When the counting of the timer period is completed, the signal output is stopped. This timer period is set longer than the period during which the inrush current occurs, and is, for example, about one cycle of AC output. Bypass circuit When switching from the power feeding to the inverter power feeding, the output of the current transformer 8 decreases, and the cancellation signal (for example, 0) is output from the comparator 93. Before the release signal (0) is output, the AND circuit 104 does not operate, and the AND condition of the AND circuit 104 is not satisfied, and the AND circuit 104 outputs the same signal (O) as the release signal. In response to this signal (0), the power feeding circuit changeover switch circuit 7 performs a switching operation from bypass circuit power feeding to inverter power feeding. When the timer drive circuit 101 detects that the output of the AND circuit 104 has changed (changes from 1 to 0), it outputs a start signal to the timer 102. Then, the timer 102 starts counting for a time period, and the output of the inverting circuit 103 changes (change from 1 to 0). As a result, even if a large inrush current occurs at this time and the output of the comparator 93 changes (changes from 0 to 1), the AND condition of the AND circuit 104 does not hold. Therefore, the output of the AND circuit 104 does not change (remains 0), and as a result, the switching signal is not output. When the counting of the timer period of the timer circuit 102 is completed, the output of the inverting circuit 103 changes (from 0 to 1). Therefore, after the timer period ends, when the output overcurrent detection circuit 9 outputs the switching signal (1), the AND condition of the AND circuit 104 is satisfied and the switching signal (1) is output from the output terminal 105. It Therefore, according to this circuit, the supply of the switching signal is blocked for the predetermined time only when the switching from the bypass circuit power supply to the inverter power supply is performed.

Reference numeral 11 compares the output voltage of the inverter 5 with a predetermined reference voltage (a reference voltage determined in consideration of the voltage drop when an overcurrent occurs), and when the output voltage is lower than the reference voltage. It is an inverter output voltage detection circuit that outputs a switching signal and controls switching of the switch circuit 7 from the inverter 5 side to the bypass circuit 6 side. The inverter output voltage detection circuit 11 includes, for example, a rectifier that full-wave rectifies the output voltage of the inverter 5, a reference sine wave voltage generation circuit that outputs a reference sine wave that is synchronized with the output of the inverter 5, and the reference sine wave. It is composed of a rectifier for full-wave rectifying the reference sine wave voltage from the voltage generating circuit and a comparator for comparing the output voltage waveforms of the two rectifiers. The inverter output voltage detection circuit 11 determines that an overcurrent has flown when the difference (voltage drop amount) between the output voltage of the inverter 5 and the reference voltage becomes equal to or greater than a predetermined value. 13 are other loads added in addition to the load 12.

Next, the operation of this embodiment will be described. The power supply device of FIG. 1 constantly supplies the output of the inverter 5 to the load 12. When an output overcurrent occurs in the output of the inverter 5 when the load is turned on or when the load suddenly changes or increases, the output overcurrent detection circuit 9 detects it and outputs a switching signal. As described above, since the signal supply blocking circuit 10 does not perform the signal supply blocking operation during the inverter power feeding, the switching signal from the output overcurrent detection circuit 9 is input to the switching switch circuit 7, and the bypass circuit is bypassed. Power is supplied from 6 to the load. When the output overcurrent detection circuit 9 detects that the overcurrent has recovered to a steady value or less, a release signal is output, which causes the changeover switch circuit 7 to automatically recover and switch to inverter power supply, and also to prevent signal supply. The circuit 10 operates to prevent the switching signal output from the output overcurrent detection circuit 9 from being supplied to the switching switch circuit 7 for a predetermined short time (several seconds). As shown in FIG. 4, when the changeover switch circuit 7 is switched back to the original state, as shown in FIG. 4, even if the inverter peak voltage Ei is slightly larger than the bypass peak voltage Eb and a temporary rush overcurrent Im flows to the load, the overcurrent Since the detection output (switching signal) of the detection circuit 9 is not input to the changeover switch circuit 7, the changeover switch circuit 7 is prevented from being changed over again to the bypass circuit 6 side.

Next, the operation of the inverter output voltage detection circuit 11 will be described. As described above, if another load 13 happens to be turned on while the signal supply blocking circuit 10 is activated and the switching signal is blocked, the inverter output such as inrush current may be output. Overcurrent occurs. When this overcurrent is large, the output voltage of the inverter 5 drops. Then, the inverter output voltage detection circuit 11 detects the decrease in the output voltage, and when the voltage decrease becomes larger than a certain value, a switching signal is output and the switching switch circuit 7 is switched and controlled again. Switch from inverter power supply to bypass circuit power supply. As a result, even when the signal supply blocking circuit 10 is operating, it is possible to cope with the inverter output overcurrent due to the fluctuation or increase of the load.

[0013]

[Effect of the device]

 As described above, according to the present invention, since the signal supply blocking circuit is provided, when the power supply circuit changeover switch circuit automatically returns from the bypass circuit power supply to the inverter power supply, the output of the inverter and the output of the bypass circuit are changed. Even if a large inrush current is generated due to the voltage difference between the output overcurrent detection circuit and the switching signal is output from the output overcurrent detection circuit, the power feeding circuit switching switch circuit does not perform the switching operation, and the power feeding circuit switching switch circuit is repeatedly switched. There are advantages that the operation is suppressed, the power supply to the load is performed stably and favorably, and the life of the power supply circuit changeover switch circuit 7 is extended. In addition, the inverter output voltage detection circuit outputs the switching signal regardless of the signal supply blocking circuit and outputs the switching signal when the output overcurrent occurs while the signal supply blocking circuit is operating, and bypasses the inverter power supply. Therefore, even if a signal supply blocking circuit is provided, the power supply circuit can be switched in response to the output overcurrent to the load without any trouble.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration example of an output overcurrent detection circuit and a signal supply blocking circuit in the present invention.

FIG. 3 is a block diagram showing an example of a conventional AC uninterruptible power supply device.

FIG. 4 is a waveform diagram illustrating an operation of the power supply device.

[Explanation of symbols]

3 ... Rectifier circuit, 4 ... Storage battery, 5 ... Inverter, 6 ... Bypass circuit, 7 ... Feeding circuit changeover switch circuit, 9 ... Output overcurrent detection circuit, 10 ... Signal supply blocking circuit, 11 ... Inverter output voltage detection circuit, 12 , 13 ... Load.

Claims (1)

[Scope of utility model registration request] 1. A rectifier circuit for rectifying AC power from a commercial power source, a storage battery charged by the output of the rectifier circuit, and an inverter for converting the DC output of the rectifier circuit or the storage battery into an AC output for output. A bypass circuit that supplies AC power from a commercial power source and an inverter power supply that is normally selected to switch the inverter power supply from the inverter to the bypass circuit power supply from the bypass circuit according to the switching signal and the bypass circuit power supply according to the release signal. From the power supply circuit changeover switch circuit for switching from the power supply to the inverter power supply, and when the output overcurrent is detected, the switching signal is output to the power supply circuit changeover switch circuit, and when the output overcurrent state returns to the steady state, the release signal is output. In an AC uninterruptible power supply comprising a detection circuit, the bypass circuit power supply to the inverter power supply When switching, a signal supply blocking circuit that blocks the supply of the switching signal output from the output overcurrent detection circuit to the power supply circuit changeover switch circuit; and a voltage that detects the output voltage of the inverter during the power supply of the inverter. An AC uninterruptible power supply device, comprising: an inverter output voltage detection circuit that outputs the switching signal to the power supply circuit switching switch circuit when the amount of drop exceeds a predetermined value.