KR200301670Y1 - Electrical load - Google Patents

Abstract

The disclosed electronic load includes a comparator for comparing a difference between a reference voltage and a feedback voltage, a first transistor on / off controlled by the output of the comparator, a second transistor on / off controlled by the first transistor, and connected to the EUT. And a control block for outputting a transistor and a feedback voltage and for switching the first transistor to an off state upon disconnection of the test object and the switching means. When the test object of the electronic load is switched from the on state to the off state, the generation of an arc due to the inrush current at the contact point of the test object is prevented, and thus the burnout of the contact point is prevented.

Description

Electronic load {ELECTRICAL LOAD}

The present invention relates to an electronic load that implements the function of the actual load such as a resistor, a coil, a capacitor, and the like using a semiconductor device such as a transistor.

1 is a circuit diagram illustrating an example of a conventional electronic load. The conventional electronic load includes a comparator A1, a first transistor TR1, and a second transistor TR2.

The comparator A1 receives the reference voltage Vr and the feedback voltage Vf from the second transistor TR2 side. The first transistor TR1 is switched controlled by the comparator A1, and the second transistor TR2 is switched controlled by the first transistor TR1. The second transistor TR2 is connected to the power source BT2 through the test object S1. The diode D1 is connected between the output terminal of the comparator A1 and the input terminal of the first transistor TR1.

When the contact is to be tested by the conventional electronic load, the reference voltage Vr maintains the set voltage at the moment when the contact of the test object S1 is cut off, and the voltage across the resistor Rs decreases as the current decreases. . Accordingly, the voltage Vf is lowered, the potential difference between the voltage Vr and the voltage Vf is generated, the difference value thereof is increased to the + potential, and the diode D1 is turned off to conduct the transistor TR1. When transistor TR1 conducts, transistor TR2 operates in a direction in which current increases. However, at the moment when the contact point of the test object S1 is cut off, since the current operates in the direction of decreasing current, the voltage across the resistor Rs decreases and the voltage Vf becomes lower. As a result, the transistor TR2 is brought into a completely conducting state. Therefore, an arc is generated at the moment when the contact falls due to the flow of the maximum current through which the load can flow, and the contact of the object under test S1 is burned out.

The present invention has been made to solve the above problems, the object of the present invention is to detect the moment when the contact point of the test object is cut off the voltage to cut off the transistor connected to the test object before the arc occurs, To provide an electronic load that prevents arcing when the contact of specimen under test is interrupted.

1 is a circuit diagram showing an example of a conventional electronic load,

2 is a circuit diagram of an electronic load according to the present invention, and

3 is a detailed block diagram of the control block of FIG. 2.

Explanation of symbols on the main parts of the drawings

Vr: reference voltage Vf: feedback voltage

D1 to D4: Diodes A1, A2: Comparators

K: control block TR1, TR2: transistor

S1: Test object C1: Capacitor

R1 ~ R10: Resistor BT1, BT2: Power

An electronic load according to the present invention for achieving the above object, a comparator for comparing the difference between the reference voltage and the feedback voltage; Switching means connected to a power supply through an object under test, controlled on / off by an output of the comparator, and in which an electric current flows to generate the feedback voltage from a voltage supplied from the power supply; And a control block outputting a control voltage for switching the switching means to the off state when the connection between the test object and the switching means is disconnected.

Here, the switching means, the first transistor to which the output of the comparator is input; And a second transistor connected to the power source through the test object and controlled on / off by an output of the first transistor. In this case, the control voltage output from the control block is input to the first transistor.

Preferably, the electronic load according to the present invention, the first diode is disposed between the input terminal of the first transistor and the output terminal of the comparator; And a second diode disposed between an input terminal of the first transistor and an output terminal of the control block.

The control block includes: a pair of voltage distribution circuits for dividing a voltage from the power supply and outputting a pair of different distribution voltages, respectively; A second comparator for comparing the difference between the pair of distribution voltages; And a capacitor connected in parallel to any one of the pair of voltage distribution circuits. Preferably, a diode is disposed between the voltage distribution circuit connected to the capacitor and the input terminal connected to the power supply.

According to the present invention, the arc generation by the inrush current at the contact point of the test object is prevented when the test object of the electronic load is switched from the on state to the off state, thereby preventing the burnout of the contact point.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings. In the description of the present invention, the same reference numerals are given to the same parts as the conventional electronic load shown in FIG.

2 is a circuit diagram of an electronic load according to the present invention.

The electronic load according to the present invention includes a first comparator A1, a first transistor TR1, a second transistor TR2, and a control block K.

The first comparator A1 is implemented using an operational amplifier, and the reference voltage Vr and the feedback voltage Vf are input to the non-inverting terminal and the inverting terminal of the first comparator A1, respectively. In addition, the output of the first comparator A1 is fed back to the inverting terminal through the resistor R1. The first comparator A1 amplifies and outputs a difference between two input voltages Vr and Vf.

The reference voltage Vr is obtained by dividing the voltage of the power source BT1 by using the variable resistor VR1. The feedback voltage Vf is the voltage of the resistor Rs described later.

The first transistor TR1 is a BJT transistor, and a resistor R4 and a resistor R5 are connected in parallel to the emitter, and a resistor R2, a first diode D1, and a second diode D2 are connected to the base. ) Is connected and a resistor (R3) is connected to the collector. A predetermined driving voltage V + is applied to the base and the collector through the resistors R2 and R3, respectively. The anodes of the first diode D1 and the second diode D2 are connected to the emitter of the first transistor TR1. In addition, the cathode of the first diode D1 is connected to the output terminal of the first comparator A1, and the cathode of the second diode D2 is connected to the output terminal h of the control block K.

The second transistor TR2 is a FET-type transistor. The resistor R5 is connected to the gate, the contact of the object S1 is connected to the drain, and the resistor R6 and the resistor Rs are connected to the source. It is connected in series. The third diode D3 is connected between the node and the gate between the resistor R6 and the resistor Rs.

The control block K is connected in parallel to the second transistor TR2, which is connected in series, to the resistor R6 and the resistor Rs. Therefore, the first input terminal f of the control block K is connected to one contact point of the test object S1 together with the drain of the second transistor TR2, and the second input terminal of the control block K is connected. (g) is connected to ground (G) together with the resistor (Rs). Both ends of the second power source BT2 are connected to the other contact point of the test object S1 and the ground G which is a common contact point of the second input terminal g of the control block K and the resistor Rs, respectively. have. As described later, the control block K outputs a control voltage for turning off the second transistor TR2 when the connection between the test object S1 and the second transistor TR2 is disconnected.

3 is a detailed circuit diagram of the control block K. FIG.

The control block K is composed of a second comparator A2, a fourth diode D4, a capacitor C1, and a plurality of resistors R8, R9, R10, and R11.

The resistor R8 and the resistor R9 are connected in series between the first input terminal f and the second input terminal g of the control block K. The resistor R8 and the resistor R9 serve to distribute the voltage between the first input terminal f and the second input terminal g in accordance with the ratio of the resistance values. The node A between the resistor R8 and the resistor R9 is input to the non-inverting terminal of the second comparator A2.

In addition, the resistor R10 and the resistor R11 are connected in series between the first input terminal f and the second input terminal g of the control block K. The resistors R10 and R11 are connected in parallel with the resistors R8 and R9, and the voltage between the first input terminal f and the second input terminal g is changed according to the ratio of the resistance values. Function to distribute The node B between the resistor R10 and the resistor R11 is input to the inverting terminal of the second comparator A2.

The fourth diode D4 is disposed between the first input terminal f of the control block K and the resistor R10. At this time, the anode of the fourth diode D4 is connected to the first input terminal f side, and the cathode is connected to the resistor R10.

In addition, the capacitor C1 is provided between the cathode of the fourth diode D4 and the second input terminal g. The second comparator A2 is composed of a differential amplifier circuit using an operational amplifier or the like. The second comparator A2 amplifies the difference between the voltages of the nodes A and B and outputs them to the output terminal h. The output of the second comparator A2 becomes the output of the control block K.

Hereinafter, the operation of the electronic load according to the present invention having the circuit configuration as described above when the object under test S1 is in an OFF state, the object under test S1 is in an ON state, and It will be described separately by dividing the test object S1 from the ON state to the OFF state.

(1) The test object S1 is in the off state

When the object under test S1 is in the off state, the electronic load does not operate and no current flows.

(2) When the test object (S1) is in the on state

First, the operation of the control block K will be described.

The positive voltage of the second power source BT2 is applied to the first input terminal f of the control block K through the test object S1, and the second power source BT2 is applied to the second input terminal g. A negative voltage of is applied, and accordingly, a predetermined voltage is applied to the nodes A and B in the control block K. At this time, the voltage applied to the node A is the voltage divided by the resistor R8 and the resistor R9, and the voltage applied to the node B is the voltage charged to the capacitor C1 through the fourth diode D4. The voltage divided by the resistor R10 and resistor R11 is obtained.

In the output terminal h of the second comparator A2, a voltage obtained by amplifying the difference between the voltages of the nodes A and B is output. At this time, when the voltage of the node A is set to be higher than the voltage of the node B, the second comparator A2 is positively biased so that the control voltage output from the second comparator A2 becomes positive (+). Therefore, since the positive voltage is applied to the cathode of the second diode D2, the second diode D2 is turned off. Accordingly, the first transistor TR1 is not connected to the second diode D2, and the first transistor TR1 is operated only by the state of the first diode D1.

Next, parts other than the control block K will be described.

The voltage of the second power source BT2 is applied to both ends of the second transistor TR2 through the test object S1. Since a constant reference voltage Vr is applied to the first comparator A1, assuming that there is no feedback voltage Vf or that the feedback voltage Vf is smaller than the reference voltage Vr, the comparator A1 is configured to have a reference voltage Vr. Forward biased, comparator A1 outputs a positive voltage.

As a result, a positive voltage is applied to the cathode of the first diode D1, and the first diode D1 is biased in the reverse direction, so that the first diode D1 is turned off. When the first diode D1 is turned off, a positive voltage is applied to the base of the first transistor TR1 through the resistor R2 to conduct the first transistor TR1. Accordingly, current flows in the first transistor TR1 to generate a voltage in the resistor R4, and the voltage of the resistor R4 is applied to the gate of the second transistor TR2 through the resistor R5. Accordingly, the second transistor TR2 is turned on so that a constant voltage is applied to the resistor R5 and the resistor Rs, respectively, and the voltage applied to the resistor Rs is the feedback voltage Vf of the first comparator A1. Feedback to the inverting terminal. As this process is repeated, when the reference voltage Vr and the feedback voltage Vf input to the first comparator A1 are the same, the first comparator A1 stops amplifying.

On the other hand, assuming that the voltage Vf fed back from the resistor Rs is greater than the reference voltage Vr, the first comparator A1 is reverse biased and the output becomes negative (-). As a result, the first diode D1 is turned on so that a current flows through the resistor R2 toward the comparator A1. Therefore, the first transistor TR1 is turned off. Since the resistor R4 is connected to the negative voltage V− side, the negative voltage is applied to the gate of the second transistor TR2 through the resistor R4 and the resistor R5. Therefore, the second transistor TR2 is turned off so that no current flows through the second transistor TR2. Accordingly, since no current flows through both ends of the resistor Rs, no voltage is generated. Accordingly, the magnitude of the feedback voltage Vf fed back to the first comparator A1 decreases, so that the input of the first comparator A1 is reduced. There is a car. Accordingly, the first comparator A1 turns off the first diode D1 by outputting a positive voltage. Accordingly, the above operation is performed again.

By repeating the above operation, the reference voltage Vr and the feedback voltage Vf are kept the same so that the current flowing in the second transistor TR2 is controlled to be constant.

Here, the resistor R3 is a load resistor during the operation of the first transistor TR1. The third diode D3 is an input protection diode and functions to protect the input together with the resistor R5. The resistor R6 is also a resistor for limiting the current and is a resistor for maintaining the stability of the second transistor TR2.

(3) When the test object S1 is switched from the on state to the off state

At the moment when the connection of the specimen under test S1 is interrupted, the current simply flows in the load using a general resistance or the like, and the state is not changed. However, at the electronic load, control is performed according to the difference between the reference voltage Vr and the feedback voltage Vf of the first comparator A1. That is, when the test object S1 is blocked, the first comparator A1 amplifies the difference between the reference voltage Vr and the feedback voltage Vf at the moment of interruption, and according to the above-described operating principle, the second transistor TR2. We are going to operate so that current flows through).

However, when the test object S1 is cut off and the voltage between the first input terminal f and the second input terminal g of the control block K drops, the node divided by the resistor R8 and the resistor R9 is divided. The voltage of (A) immediately drops, but the voltage of node B divided by resistor R10 and resistor R11 does not drop immediately, but the voltage charged in capacitor C1 is equal to capacitor C1 and resistors R8, It gradually falls to the time constant time value according to R9). Accordingly, the first comparator A2 is directly reverse biased, and a negative control voltage is output from the output terminal h of the second comparator A2. As a result, the second diode D2 becomes a forward bias, and current flows and is conducted.

When the second diode D2 is turned on, a current input to the base of the first transistor TR1 through the resistor R2 flows through the second diode D2, and thus the base of the first transistor TR1. Since the potential becomes low, the first transistor TR1 is turned off. Accordingly, the second transistor TR2 is also turned off. That is, at the moment when the test object S1 is blocked, both the first transistor TR1 and the second transistor TR2 are turned off and no current flows through them. In addition, in the state where the second diode D2 is turned on, the operation of the first comparator A1 controlled through the first diode D1 has no effect. Therefore, a problem in the prior art, that is, since the control block (K) of the present invention does not exist, since the current flows momentarily rapidly when the test object (S1) is blocked, the arc generation of the contact is This prevents burnout of the contact.

On the other hand, when voltage is applied to the input terminals f and g of the control block K, the fourth diode D4 serves to supply a voltage to the capacitor C1, and the voltage of the input terminals f and g. At the time of extinction, since the fourth diode D4 is reverse biased and shut off, the fourth diode D4 serves to prevent voltage from being applied to the resistors R8 and R9.

In the present invention, although the comparators A1 and A2 have been described as an example of an operational amplifier, various types of comparison circuits capable of outputting a difference between two inputs may be employed in addition to the operational amplifier.

In addition, in the present invention, the first and second transistors TR1 and TR2 are used to implement an electronic load, but the type of each transistor is not limited to the BJT or FET as described above, and a switching circuit using a simple transistor. In addition, various types of switching circuits for performing a switching operation by a control voltage may be used.

As described above, according to the present invention, arc generation by the inrush current at the contact point of the test object S1 when the test object S1 of the electronic load is switched from the on state to the off state is prevented, Therefore, the burnout of the contact is prevented.

Although the above has been illustrated and described with respect to preferred embodiments of the present invention, the present invention is not limited to the specific embodiments described above, those skilled in the art within the scope not departing from the gist of the present application Various modifications may be made and such modifications fall within the scope of the utility model registration claims in the present application.

Claims (5)

A comparator for comparing the difference between the reference voltage and the feedback voltage; Switching means connected to a power supply through an object under test, controlled on / off by an output of the comparator, and in which an electric current flows to generate the feedback voltage from a voltage supplied from the power supply; And a control block for outputting a control voltage for switching the switching means to an off state when the connection between the test object and the switching means is disconnected. The method of claim 1, The switching means, A first transistor to which an output of the comparator is input; And And a second transistor connected to the power supply through the test object and controlled on / off by an output of the first transistor. And the control voltage output from the control block is input to the first transistor. The method of claim 2, A first diode disposed between an input terminal of the first transistor and an output terminal of the comparator; And And a second diode disposed between the input terminal of the first transistor and the output terminal of the control block. The method of claim 3, wherein The control block, A pair of voltage distribution circuits for dividing a voltage from the power supply and outputting a pair of divided voltages respectively; A second comparator for comparing the difference between the pair of distribution voltages; And And a capacitor connected in parallel to any one of the pair of voltage distribution circuits. The method of claim 4, wherein And a diode disposed between the voltage distribution circuit connected to the capacitor and the input terminal connected to the power supply.