JPH0287943A - Unieterruptble power supply - Google Patents

Abstract

PURPOSE:To protect a transistor, even if said transistor has a capacity only capable of withstanding a steady-state current, by driving at the starting time a thyristo resistant to a sure current. CONSTITUTION:A current quick shutdown circuit 13 is constituted as a semiconductor circuit composed of a transistor Q1 connected in series between a commercial power supply 1 (full-wave rectifier circuit 2) and a load 4 to form a breaking element, and of a transistor control circuit 14 controlling said transistor Q1. Further, an overcurrent protection circuit 17 composed of a thyristor (SCR) 15 connected in parallel with said transistor Q1 and SCR control circuit 16 driving said SCR 15 only at the starting time is added to said current quick shutdown circuit 13. According to said constitution, the SCR 15 resistant to a surge current is provided in parallel with the transistor Q1, and when said SCR 15 is driven and there is a rush surge current at the starting time, said surge current is bypassed by said SCR 15 so that said transistor Q1 is protected from the rush current.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an uninterruptible power supply device that uses a relay to switch between a normal power supply system and an emergency power supply system.

Conventional technology Conventionally, there is an uninterruptible power supply that uses commercial power to supply power to the load at all times, but in the event of an emergency such as a power outage, it uses a backup power supply by switching relay contacts. . This method has problems such as arcing and welding between the contacts when switching the relay contacts.

Therefore, in order to immediately interrupt the current at the time of switching, it is conceivable to add an immediate current interrupt circuit using a transistor as a semiconductor switching element. However, the load of this type of small uninterruptible 7u original device is, for example, a device with a built-in switching power supply, and since these are generally capacitor input type, inrush current (surge current) may exist. That is inevitable.

This rush current reaches 10 to 30 times the steady current. If such an inrush current occurs, it may damage the transistor as a switching element or require a transistor with a large capacity.

Problems to be Solved by the Invention Therefore, for example, in an uninterruptible power supply device rated for a load of 300VA with an input of 100V, considering this inrush current against a steady current of 3A, it is difficult to use as a interrupting element for immediate current interruption. The maximum rating of the transistor needs to be 100A, which is uneconomical in terms of cost and shape.

Means to Solve the Problem In an uninterruptible power supply that uses relay contact switching to switch connections between the commercial power supply system that supplies power to the load in normal times and the backup power supply system that supplies power to the load in an emergency, the commercial power supply and the relay contact, an over-market current protection circuit is connected in series with a current immediate cut-off circuit formed by a semiconductor circuit with a cut-off element as a transistor, and includes a thyristor connected in parallel to the transistor and is driven at startup. will be established.

When the action is started, the thyristor, which is strong against surge current, is driven, so that the current does not flow to the transistor, and is bypassed on the thyristor side. Therefore, even if the transistor has a capacity that can withstand a steady current, it is protected.

Example An embodiment of the present invention will be described based on the drawings.

First, a commercial power source 1 called AClooV is provided, and includes a full-wave rectifier circuit 2 to form a commercial power source system 3, which is configured to constantly supply power to a load 4. On the other hand, a backup power supply system 5 is provided for supplying power to the load 4 in the event of an emergency such as a power outage. This backup power system 5
Power is supplied by a backup generation circuit 7 using a battery 6 as a power source. Secondly, in order to switch the connection between the commercial power supply system 3 and this backup power supply system 5 for the load 4, the charging circuit 8 that is charged by the commercial power supply 1 is used as a power source and a signal from a detection signal generation circuit 9 such as a power outage is generated. A relay drive circuit 10 driven by the relay drive circuit 10 is provided, and a relay contact 11 that is opened and closed by the relay drive circuit 10 is provided. Also, when the relay contact 11 is switched, the relay contact 12 is simultaneously switched open and closed by this relay drive circuit l○.
is provided between the battery 6 and the backup output generating circuit 7.

In such a basic configuration, normally the relay contact 11
is switched to the commercial power supply system 3, and the load 4 is supplied with power by the commercial power supply 1.

At this time, the relay contact 12 is also in an open state. In the event of an emergency such as a power outage, the detection signal generation circuit 9 detects the power outage, the relay drive circuit 10 switches the relay contact 11 to the backup power supply system 5 side, and the backup output generation circuit 7 outputs the power to the load 4 based on the battery 6. Power is supplied to the

Therefore, in this embodiment, a current immediate cutoff circuit 13 is provided for the commercial power supply system 3. This instantaneous current cutoff circuit 13 is schematically constructed from a commercial power source 1 as shown in FIG.
This semiconductor circuit has a transistor Q1 which is connected in series between the full-wave rectifier circuit 2 and the load 4 and serves as a cutoff element, and a transistor control circuit 14 which controls the transistor Q1. This transistor control circuit 14 basically turns off the transistor Q1 so that the commercial power supply system 3 is immediately (instantaneously) cut off when switching from the commercial power supply state to the backup power supply state. Furthermore, the instant current cutoff circuit 13 of this embodiment has an overcurrent protection function, and the transistor Q
Thyristor (SCR) 15 connected in parallel to 1 and this 5
SCR control circuit 16 that drives CR15 only at startup
An overcurrent protection circuit 17 is added.

According to such a configuration, a 5CR15 that is resistant to surge current is provided in parallel with the transistor Q, and this 5CR15 is driven at startup, and when there is an inrush surge current, it is bypassed by this 5CR15. Transistor Q is protected from inrush current. That is, the transistor Q only needs to have a capacity that can withstand a steady current, and can be small and inexpensive. In this case, 5CR1
5 may also be small. Furthermore, switching between the 5CR15 and the transistor Q can be performed without momentary interruption, and does not affect the operation of the load 4 at all.

By the way, a specific example of the circuit configuration of the instant current cutoff circuit 13 with the overcurrent protection circuit 17 is shown in FIG. First, a transformer T, a diode D1, and a capacitor C1 are provided for taking power from the commercial power supply system 3 and rectifying and smoothing it. A phototransistor Q2, which is normally off but turned on during backup, is connected to both ends of this capacitor C1.
Two stages of transistors Q, , Q, are connected to the base side of the transistor Q, whose collector and emitter are connected between the output terminals of the full-wave rectifier circuit 2. A transistor Q is connected in series with the transistor Q4 to the base side of the transistor Q1.

In addition, in FIG. 2, phototransistors Q, ,Q.

To be more precise, what is shown is only the output stage of the photocoupler, the primary side of which is controlled in accordance with a power outage detection signal. Here, the on/off operation modes of these phototransistors Q, Q, are shown. Under normal conditions, both phototransistors Q2 and Q are off, but in an emergency (power outage, abnormal voltage), etc.), phototransistors Q2, Q, are both turned on.

This is the basic configuration of the instant current cutoff circuit 13. Normally, transistor Q6 is on, and transistors Q, , Q are also off due to phototransistor Q2 being off.
, the base is biased and turned on. That is,
The commercial power supply system 3 is maintained in a normal connection state with respect to the load 4.

Furthermore, in the event of an emergency such as a power outage, the power supply is switched to the backup power supply system 5 as described above, and at the time of this backup switching, the phototransistor Q is switched from the off state to the on state.

As a result, transistors Q, ,Q are also turned on.

Therefore, the base bias caused by transistor Q6 is short-circuited by transistor Q4, transistor Q1 is turned off, and commercial power supply system 3 is immediately cut off.

On the other hand, as the overcurrent protection circuit 17, the capacitor C
A phototransistor Q is connected to both ends of the transistor Q and is turned on during backup, a transistor Q7 is conductive when the phototransistor Q1 is off, a transistor Q is conductive when the transistor Q is turned on, and a transistor Q is turned on. A transistor Q3 that is turned on at certain times is provided. The transistor Q is a diode D
2 to the gate of the 5CR15.

Further, a transistor Q1°, which is turned on when the transistor Q is turned off, is connected to a downstream of the transistor Q, and is connected to a Zener diode ZD. This Zener diode ZD includes a transistor Q I 1 that is turned on by conduction of the Zener diode ZD, a transistor Q I □ that controls its on/off, and a transistor Q I that is on/off controlled by the transistor Q I l in parallel with the diode D1. 3 are connected sequentially.

In addition, the Zener diode ZD and the transistor Q l
A transistor Q + 4, which is turned on by the transistor Q1, is connected to the midpoint of the connection with the transistor Q1.

In such a configuration of the overcurrent protection circuit 17, since the phototransistor Q is in an off state during normal commercial power supply, the transistor Q? Although IQ,,Q, are in the on state, the transistors Q, 2°Q + 3 are also in the on state, and 5CR15 is not conductive (at this time, the transistor Q, is in the on state as described above). On the other hand, transistor Q? 1QIIQ3, Q8. turns on.

By the way, when the power is turned on, the transistor Q.

Q is turned on, and 5C is applied via resistor R1 and diode D2.
Give a gate signal to R15. However, immediately after the power is turned on, the transistor Q +++ Q+
In order to keep z off, transistor Q,
is also off. Therefore, since no base current is applied to transistor Q1, this transistor Q is in an off state. That is, during this period immediately after turning on, the current in the main circuit is 5
It flows through CR15. After a certain period of time due to the action of the time constant circuit, when the voltage of the capacitor C2 reaches a level that allows current to flow through the Zener diode ZI), the transistors Q, , Q, , Q, turn on, and the gate current flows through the SCR15. By blocking the flow of the transistor Q6 and turning on the transistor Q6, a base current is applied to the transistor Q1, and this transistor Q is turned on.
The current of the main circuit is also merged into the transistor Q. Then, when 5CR15 is turned off, the main circuit current flows through transistor Q1.

On the other hand, at the time of recovery startup when switching from backup power supply to commercial power supply, transistor Q1 etc. return to the on state, but at that time, when a large current flows due to an inrush current, transistor Q4 is turned on by detection resistor R2, and transistor Q1, etc. .

In order to keep Q　ff　off, 5CR15 is a resistor R.

Triggered via diode D2, turning on 5CR15. Therefore, the inrush current at the time of switching is bypassed by driving the 5CR15 in this manner. Then, when the inrush current decreases to the normal level, the transistor Q
+ 4 turns off and transistor Q l 1 turns on, turning on transistor Q t s and 5CR15
The gate trigger is no longer applied, and 5CR15 is turned off. On the other hand, the transistor Q1 is always base biased during this period.

It remains on, the load current flows through transistor Q1, and this switching is seemingly instantaneous.

Effects of the Invention As described above, the present invention includes a current immediate cutoff circuit formed by a semiconductor circuit with a transistor as a cutoff element connected in series between a commercial power source and a relay contact, and a thyristor connected in parallel to the transistor. Since we have provided an overcurrent protection circuit that is driven at startup, the thyristor, which is strong against surge currents, is driven at startup, so no inrush current flows to the transistor, and this thyristor is bypassed, so that the transistor remains in steady state. Even if it is synthetic and can withstand current, it will still be protected, so
A small and inexpensive current immediate cutoff circuit is sufficient.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a block diagram, and FIG. 2 is a circuit diagram of an immediate current cutoff circuit. ■...Commercial power supply, 3...Commercial power supply system, 4...Load, 5
... Backup power supply system, 13 ... Current immediate cutoff circuit, 15 - Thyristor, 17 ... Overcurrent protection circuit,
Q1 transistor

Claims (1)

[Claims] In an uninterruptible power supply that uses relay contact switching to switch connections between a commercial power supply system that supplies power to the load in normal times and a backup power supply system that supplies power to the load in an emergency, there is a connection between the commercial power supply and the relay contact. An uninterruptible device characterized in that instantaneous current cutoff circuits formed by semiconductor circuits are connected in series, with the cutoff element being a transistor, and an overcurrent protection circuit that includes a thyristor connected in parallel to the transistor and is driven at startup is provided. power supply.