KR20020014434A - A selectively current limiting apparatus with changing of currents and a high speed excess current sensing apparatus - Google Patents

Abstract

PURPOSE: A selective current limiting device according to changing of currents which prevents an excess current from being flown into a load and a high speed excess current sensing device which is capable of coping with the excess current by promptly sensing a fact that the excess current is generated are provided. CONSTITUTION: In a circuit device in which a load is connected to a constant voltage source, the selective current limiting device according to changing of currents is positioned between the constant voltage source and the load and comprises a reactor for limiting the excess current, two or more of diodes and a DC power supply in case that an excess current of a limit current or more by the constant voltage from the constant voltage source is impressed to the load, wherein the current limiting device comprises a reactor, a first diode, a second diode of free-wheeling diode, and a DC power supply, wherein the reactor is electrically connected to the constant voltage source and the load in series, the first and second diodes connected in series are electrically connected to the reactor in a row, and the DC power supply is impressed to both ends of the second diode, and wherein the selective current limiting device according to changing of the currents further comprises a voltage sensing circuit part, a high impedance op amp, a comparator, a pulse transformer and a CPU(central processing unit).

Description

A selective current limiting apparatus with changing of currents and a high speed excess current sensing apparatus}

The present invention is a selective current limiting device according to the change of the current value to prevent the flow of the transient current to the load, and a transient high-speed detection device that can quickly detect and cope with the occurrence of the transient current.

In general, when the output of the power supply is short-circuit such as a short (short), the load current is increased very rapidly. This current not only damages the load, but also has a great effect on the power supply.

For example, a plasma power supply frequently generates an arc phenomenon, which is a short state in the load. The power supply needs to detect the arc quickly and shut off the output. This is because arc energy due to excessive arc current degrades the characteristics and quality of the application load.

Selective current limiting device according to the current value change according to the present invention can improve the quality of the application load by limiting the current when an arc occurs in the load.

Conventionally, in order to detect an arc as soon as possible to cut off the output, a method for quickly detecting an arc is used. However, this method has a disadvantage in that the current rises sharply during the time between arc detection and output interruption, so that the magnitude of arc energy cannot be reduced absolutely.

Another method of the related art for achieving the above object is to insert a reactor at the output stage, a method of suppressing the rising slope of the arc current by inserting the reactor at the output side. However, this method also operates the reactor itself as part of the load irrespective of the arc phenomenon on the load side, so the ripple occurs in the output voltage due to the load change in the final output voltage.

In addition, when a load current needs to be changed, that is, when an output voltage and a current such as a pulse waveform are required, the operation becomes impossible.

SUMMARY OF THE INVENTION An object of the present invention is to provide a selective current limiting device according to a change in current value when a transient current occurs in a load by improving the problems of the prior art.

Another object of the present invention is to provide a device capable of detecting a transient current generated in a load at high speed in addition to the selective current limiting device.

1 is a circuit diagram showing a state in which the current limiting device according to the present invention is connected to a constant voltage source and a load.

FIG. 2 is a view showing a flow chart of an enlarged current limiting apparatus according to the present invention in FIG.

3 is a block diagram of the transient high speed detection device according to the present invention.

The selective current limiting device according to the present invention utilizes energy accumulated reactors to limit transient currents such as arc currents. As a result, during normal load operation, the output voltage of the power supply is transmitted to the load as it is, but when an arc occurs in the load, it acts as a general reactor to suppress an increase in output current.

Such a selective current limiting device according to the present invention uses the following basic principles. That is, the voltage across the reactor has a value of zero when there is no change in current with time. Therefore, if the current of the reactor is kept constant, since the voltage across the reactor is 0, two circuits to be connected at the equipotential can be connected using the reactor.

In addition, according to the present invention, the transient high-speed detection device uses a differential element of the arc current to detect the arc, so that it is possible to perform the blocking even if the current amount of the arc does not exceed a predetermined size.

In other words, when an arc occurs, the final load voltage is almost zero, and the output voltage of the power supply is mostly applied to the stray inductor and the resistor such as the bus and the bar of the power supply. Therefore, the slope of the current rises sharply. In this case, a reactor is inserted between the inside of the power supply or the outside of the power supply and the load terminal to suppress the current slope. In general, the arc detection method in such a system is designed to detect a load current and to perform a load shedding when a certain size or more is exceeded. In this case, however, the voltage detection technique can be used to detect arcing early. This means that an arc occurs and the current of the reactor rises when a certain amount of voltage (input voltage) is applied to the reactor. Therefore, the current can be cut off by achieving the detection speed of the arc very fast by detecting the arc using the rising motive current of current, compared to the conventional method of detecting the current through the comparator.

Selective current limiting device according to the current value change according to the present invention, the circuit device is a load connected to a constant voltage source is located between the constant voltage source and the load, the transient current beyond the limit current by the constant voltage from the constant voltage source When applied to the load, it consists of a reactor, at least two diodes, and a direct current power supply to limit the transient current.

The current limiting device includes a reactor, a first diode for preventing a current from the DC power supply from flowing backward and a transient current applied to a load to the reactor, and a second diode, free-wheeling. A diode and a DC power supply for accumulating electrical energy by supplying a constant voltage to the reactor are preferred.

More preferably, the reactor is electrically connected in series with the constant voltage source and the load, the first and second diodes are electrically connected in series with each other, and the first and second diodes connected in series are electrically connected in parallel with the reactor. The DC power supply is configured to be applied to both ends of the second diode.

In addition, the selective current limiting device according to the present invention

The selective current limiting device according to the current value change includes: a voltage sensing circuit unit configured to sense an input voltage and a load voltage of a reactor;

A high impedance op amp for receiving the voltage signal sensed from the voltage sensing circuit unit and preventing the input signal from being delayed by coupling with a power supply side;

A comparator input to the (+) side for the reactor input voltage and to the (-) side for the load voltage among the voltage signals outputted through the high impedance op amp;

A pulse transformer for minimizing delay of the output signal of the comparator and electrical isolation from the power supply side;

When it is determined that the transient current is generated by receiving the output value of the pulse transformer, the CPU further includes a central processing unit (CPU) for controlling the output to be cut off so that the transient current can be detected at a high speed.

1 is a circuit diagram showing a state in which the current limiting device according to the present invention is connected to a constant voltage source and a load.

2 is a view showing a flow chart of the current by expanding the current limiting device according to the present invention in FIG.

3 is a block diagram of the transient high speed detection device according to the present invention.

With reference to the drawings will be described the operation principle of the current limiting device and the transient current high speed detection device according to the present invention.

First, the operation principle of the current limiting device according to the present invention is divided into five modes.

Step 1: accumulate minimal energy in the reactor

Increase the output voltage of the DC-DC converter before connecting the load and starting operation.

This voltage is a low voltage of several volts. At this time, a current flows to the reactor through the second diode D2 of FIG. 2 (Ibi). At this time, the magnitude of the reactor current ILin is limited by R L , which is the internal resistance of the reactor as shown in Equation (1), and the rising slope is determined by LB as shown in Equation (2).

The current flows through the power supply + terminal → D1 → LB → power supply-terminal, in which case Ibal and ILin are the same.

Step 2: Current Accumulation Mode Over Load Current

The load current flows by supplying the output voltage to the load. At this time, as the load current increases, the ILin current increases and the current of the reactor is set to the size of Iload + Ibi. This is when the voltage is initially applied to the load in the DC mode, and at the time of the initial several pulses in the pulse mode. Of course, it is also possible to perform real-time control of ILin current by as much as Ibi than Iload current by current control.

In this operation, when a load larger than Ibi is initially applied, the current required by the load does not flow to the diode but flows to the reactor, so that the reactor current naturally rises to the load current size as shown in Equation (1). This can also be explained by the theory that the sum of the currents in a point from the node-equation must be zero.

When the initial current is supplied to the load, the reactor is near zero. Therefore, the load current will try to flow the load current to Vin. However, since the voltage at both ends of the reactor cannot change instantaneously, that is, the current of the reactor cannot increase rapidly, the load current flows through the first diode D1 and the DC power supply having low impedance. However, because Ibal cannot flow reversely, the load current eventually rises slowly through the reactor. That is, it operates as if the L-R load is connected at this time. In this state, as time elapses, the current of the reactor is further increased by Ibi, which is a current flowing through D1, by the same operation as the current accumulation mode by the voltage supplied from the DC power supply. Therefore, when the load current is Iload, the current of the reactor flows as much as Ibi than the load current Iload, and Ibi flows in the DC power supply. At this time, the voltage across the reactor becomes zero again. More precisely, the supply voltage of the DC power supply minus the diode voltage drop is about 1 to 2V.

Step 3; Reactor Both Ends Voltage 0 Mode (Normal Output Operation Mode)

As a next step, the voltage at both ends of the load may be transmitted as it is, 1000V, which is an input voltage of the device, and may have excellent output voltage characteristics. At this time, the magnitude of the load current that can guarantee zero voltage across the reactor is ILin, and the magnitude of the load current ripple is Ibi. This is because there may always be some ripple in the load current because these components flow through the low impedance DC power supply and the first diode rather than the larger impedance reactor. This is because the first diode is forward biased because Ibal is still positive when the ripple is less than Ibi. In this case, the operation is performed as if there is no reactor.

Even in the pulse mode for the above reason, Ibal is equal to Ibi in the section where the current flows, and similarly, the voltage across the reactor is 0, and Ibal becomes ILin in the section where no current flows. In this case as well, the voltage across the reactor is zero. When the load current flows again, Ibal is reduced to Ibi. Likewise, in this case, since the first diode D1 is forward biased, the voltage across the reactor is zero. As a result, in the pulse mode, the input pulse waveform of the designed device is transmitted without any delay, unlike the case where only a conventional reactor is inserted. This is because the current limiting device according to the present invention operates as if there is no reactor in the normal state, and the current path passes through the first diode D1 and the direct current power supply.

However, in the pulse mode, if the pulse frequency is low and the voltage off time is long, if the current of the reactor becomes smaller than the required load current due to the slight decrease of the current in the case of Ibal, the pulse voltage is momentarily reapplied. As in step 2, there is a current rising mode through the reactor, which causes an instantaneous voltage dip in the output voltage. Therefore, in this case, control should be performed so that the current of the reactor is not smaller than the load current. This is done by controlling the voltage of the DC power supply.

Step 4: Arc Current Limiting Mode

When an arc occurs in the load, the resistance of the load is almost zero, so the current rises rapidly. However, due to the same operation as in step 2, the arc current is restricted by the reactor.

In the event of an arc, the load current rises rapidly. At this time, the path of the load current is from the input side → the first diode (D1) → (+) of the DC power supply → (-) → load of the DC power supply. At this time, Ibal decreases. The path lasts until the Ibal current becomes zero, which decreases as the load current increases. In other words, the load current Iload is equal to the reactor current. The load current then wants to rise further, but to do so, Ibal must be negative, making it impossible as the first diode is reversed. As a result, the load current flows to the reactor and the load current rapidly decreases the rising slope of the current by the reactor. At this time, the path of current is connected to input → reactor → load. Ibal is zero. This is because current cannot flow as the first diode becomes reverse biased.

Step 5: Arc Recovery Mode

When the arc is extinguished at the load or the output load current is cut off by the arc detection, the reactor current becomes zero as the load current becomes 0.The reactor current is (-) of the DC power supply → (+) → first diode → reactor of the DC power supply Free-wheeling is used to restore normal operation. The current which rises with the load due to the arc is spontaneously reduced by the losses of the current limiting device according to the invention, including the reactor. Finally stabilized with Iload + Ibi.

Next, the transient high speed detection device according to the present invention has the following operation principle.

Step 1: Input Step of Voltage Sensor Signal

The reactor input voltage and output voltage (load voltage) are sensed for arc detection.

It is input into a high impedance op amp circuit consisting of voltage follow. This is to eliminate the delay of the sensor signal due to the coupling to the power supply side.

Step 2: Compare the Voltage Sensor Signals

The input signal is input to the comparator.

The positive reference of the comparator is used by dividing the input voltage by using a voltage divider resistor. The negative comparator input becomes the output voltage. In this state, if an arc occurs, the input voltage remains the same, and the output voltage (load voltage) becomes zero, and the output of the comparator becomes zero. This comparator output is generated as soon as an arc occurs.

Step 3: high speed transmission of detection signal

The detection signal is delivered to the CPU through a pulse transformer or photo-coupler to minimize delay while providing electrical isolation from the power supply. By using the signal, the CPU blocks the output.

The current limiting device according to the present invention minimizes arc energy according to limiting arc current when transient current (arc current) occurs without affecting the output characteristics of the load at all, thereby further enhancing the characteristics of the application product. Can be.

In addition, since the current limiting device according to the present invention can be used as an attachment to an existing device, even if the arc detection is applied to a late power supply device, not only can the output quality be improved due to the limited arc current, but also if the fast arc detection technique is mixed Extremely good characteristics can be obtained.

In addition, the transient current high speed detection device according to the present invention, which is added to the current limiting device, detects immediately at the time of occurrence of an arc, unlike a conventional device that detects after a current rise, so that high speed detection is possible, and the arc current is quickly blocked by the arc. It helps to minimize the damage caused by energy.

Claims (4)

In a circuit arrangement in which a load is connected to a constant voltage source, Located between the constant voltage source and the load, when a transient current greater than the limit current due to the constant voltage from the constant voltage source is applied to the load, to the reactor and at least two diodes and DC power supply to limit the transient current Selective current limiting device according to the configured current value change. 2. The current limiting device of claim 1, wherein the current limiting device is a reactor, a first diode for preventing a current from the DC power supply from flowing backward and allowing a transient current applied to a load to flow to the reactor, and a second diode. And a free-wheeling diode and a direct current power supply for accumulating electric energy by supplying a constant voltage to the reactor. The reactor of claim 2, wherein the reactor is electrically connected in series with the constant voltage source and the load, the first and second diodes are electrically connected in series with each other, and the first and second diodes connected in series are electrically connected in parallel with the reactor. And the direct current power supply is configured to be applied to both ends of the second diode. According to any one of claims 1 to 3, wherein the selective current limiting device according to the current value change includes a voltage sensing circuit for sensing the input voltage and the load voltage of the reactor; A high impedance op amp for receiving the voltage signal sensed from the voltage sensing circuit unit and preventing the input signal from being delayed by coupling with a power supply side; A comparator input to the (+) side for the reactor input voltage and to the (-) side for the load voltage among the voltage signals outputted through the high impedance op amp; A pulse transformer for minimizing delay of the output signal of the comparator and electrical isolation from the power supply side; And a central processing unit (CPU) for controlling to block the output when it is determined that the transient current is generated by receiving the output value of the pulse transformer.