CN211478537U

CN211478537U - Test circuit and test system

Info

Publication number: CN211478537U
Application number: CN201922373426.2U
Authority: CN
Inventors: 范以训
Original assignee: Littelfuse Semiconductor (Wuxi) Co Ltd
Current assignee: Littelfuse Semiconductor (Wuxi) Co Ltd
Priority date: 2019-12-25
Filing date: 2019-12-25
Publication date: 2020-09-11
Anticipated expiration: 2029-12-25

Abstract

A test circuit and a test system, comprising: a triac comprising a gate electrode, a first electrode and a second electrode; an inductor having a first end electrically connected to the second electrode; a first electrode plate of the first capacitor is electrically connected with the second end of the inductor through a first node, and a second electrode plate of the first capacitor is electrically connected with the first electrode through a second node; a first resistor connected in parallel with the first capacitor between a first node and a second node; and a direct current power supply, the anode of which is electrically connected to the first node through the second resistor, and the cathode of which is electrically connected to the second node. By adopting the test circuit and the test system provided by the disclosure, the dynamic voltage rise rate (dynamic dv/dt) of the bidirectional thyristor can be conveniently and effectively tested.

Description

Test circuit and test system

Technical Field

The utility model relates to an electronic component tests the field, especially relates to a test circuit and test system.

Background

Among the selection parameters of the thyristor, the voltage rise rate (dv/dt) is an important consideration parameter of the thyristor. In the circuit containing the thyristor switch, due to the influence of lightning or operation and the like, steep waves are generated in a normally stable circuit, so that large voltage change is generated, and the voltage loaded on the thyristor also generates a large voltage change rate, so that the thyristor is switched from an off state to an on state. The resistance of a thyristor to such voltage variations (steep wave conditions) is generally expressed in terms of a parametric voltage-resistant rate of rise (dv/dt), which may also be referred to as a static voltage-resistant rate of rise.

However, as the switching element, in the whole process of the switch, in addition to the stage from off to on, the stage from on to off must be considered. That is, in the on state of the thyristor with a large current, there is a possibility that the thyristor which should be turned off will not be turned off, that is, cannot be turned off. Unlike the off-to-on state (the former is in the no-current state, where a steep wave occurs, i.e. a voltage change, which causes a turn-on action due to the voltage change), the latter is in the on-state with a large current, when the current drops below the thyristor holding current IH, the device will turn off, and a voltage is applied across the device, if the slope of the voltage change is too fast, the device will turn on again, and the capability of the thyristor to resist the voltage change in such a case from on to off is examined, which is called the dynamic voltage rise (dv/dt).

The static and dynamic voltage withstand rise rates are different because the states are different, and the test method and the consideration method cannot be used instead. The static voltage rise rate parameter of the thyristor is tested, and corresponding simple test tools or equipment are available on the market. However, for the dynamic voltage rise rate of the thyristor, no corresponding test tool or equipment is available in the market at present, and no corresponding consideration method is available.

SUMMERY OF THE UTILITY MODEL

Some embodiments of the present disclosure provide a test circuit, comprising: a triac comprising a gate electrode, a first electrode and a second electrode; an inductor having a first end electrically connected to the second electrode; a first electrode plate of the first capacitor is electrically connected with the second end of the inductor through a first node, and a second electrode plate of the first capacitor is electrically connected with the first electrode through a second node; a first resistor connected in parallel with the first capacitor between a first node and a second node; and a direct current power supply, the anode of which is electrically connected to the first node through the second resistor, and the cathode of which is electrically connected to the second node.

In some embodiments, the test circuit further comprises: and the gate control device is used for providing a starting signal for the gate.

In some embodiments, the turn-on signal is a pulsed signal.

In some embodiments, the dc power supply is a regulated dc power supply, and the voltage output by the regulated dc power supply is continuously adjustable.

In some embodiments, the test circuit further comprises: the bidirectional thyristor is connected between the first end of the inductor and the second node in parallel.

In some embodiments, the second capacitance is an adjustable capacitance.

In some embodiments, the test circuit further comprises: and the at least one branch circuit is connected with the bidirectional thyristor in parallel between the first end of the inductor and the second node, wherein each branch circuit comprises a switch, a resistor and a capacitor which are connected in series.

In some embodiments, the test circuit further comprises: and the diode is connected between the direct current power supply and the second resistor in series, wherein the anode of the diode is electrically connected with the anode of the direct current power supply, and the cathode of the diode is electrically connected with the second resistor.

In some embodiments, the first capacitor and the capacitor form a resonant circuit when the bidirectional thyristor is turned on, and a resonant frequency of the resonant circuit is equal to a mains frequency.

Some embodiments of the present disclosure provide a test system, comprising: the test circuit described in the previous embodiment; and an oscilloscope which displays a voltage between the first electrode side and the second electrode side of the triac and displays a current flowing through the first electrode.

By adopting the test circuit and the test system provided by the disclosure, the dynamic voltage rise rate (dynamic dv/dt) of the bidirectional thyristor can be conveniently and effectively tested.

Drawings

Other objects and advantages of the present invention will become apparent from the following description of the invention, which is made with reference to the accompanying drawings, and can help to provide a thorough understanding of the present invention.

FIG. 1 is a test circuit diagram provided by some embodiments of the present disclosure;

FIG. 2 is a schematic diagram of a test system provided by some embodiments of the present disclosure;

fig. 3 shows a graph of the voltage between the two electrode sides of the triac and the current flowing through the triac, which can be turned off during the test;

fig. 4 shows a graph of the voltage between the two electrode sides of the triac and the current flowing through the triac, wherein the triac cannot be turned off during the test;

fig. 5 shows a graph of the voltage between the two electrode sides of the triac and the current flowing through the triac, wherein the triac is in a critical state that is about to fail to turn off during the test;

FIG. 6 is an enlarged view of the portion indicated by the arrow in FIG. 5; and

fig. 7 is a test circuit diagram provided by some embodiments of the present disclosure.

Detailed Description

The technical solution of the present invention is further specifically described below by way of examples and with reference to the accompanying drawings. In the specification, the same or similar reference numerals denote the same or similar components. The following description of the embodiments of the present invention with reference to the accompanying drawings is intended to explain the general inventive concept and should not be construed as limiting the invention.

Furthermore, in the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the embodiments of the disclosure. It may be evident, however, that one or more embodiments may be practiced without these specific details.

It should be noted that, although the terms "first", "second", etc. may be used herein to describe various elements, components, elements, regions, layers and/or sections, these elements, components, elements, regions, layers and/or sections should not be limited by these terms. Rather, these terms are used to distinguish one element, component, element, region, layer or section from another. Thus, for example, a first component, a first member, a first element, a first region, a first layer, and/or a first portion discussed below could be termed a second component, a second member, a second element, a second region, a second layer, and/or a second portion without departing from the teachings of the present disclosure.

Thyristor (Thyristor) is called silicon controlled rectifier for short, and has the characteristics of silicon rectifier device, can work under the conditions of high voltage and large current, and its working process can be controlled, and can be extensively used in electronic circuits of controllable rectification, ac voltage regulation, contactless electronic switch, inversion and frequency conversion, etc.. A triac is a type of thyristor that includes a gate and two main electrodes that conduct with each other whenever a turn-on signal is input to the gate.

The present disclosure provides a test circuit, including: a triac comprising a gate electrode, a first electrode and a second electrode; an inductor having a first end electrically connected to the second electrode; a first electrode plate of the first capacitor is electrically connected with the second end of the inductor through a first node, and a second electrode plate of the first capacitor is electrically connected with the first electrode through a second node; a first resistor connected in parallel with the first capacitor between a first node and a second node; and a direct current power supply, the anode of which is electrically connected to the first node through the second resistor, and the cathode of which is electrically connected to the second node. The dynamic voltage rise rate (dynamic dv/dt) of the bidirectional thyristor can be conveniently and quickly tested by adopting an oscilloscope.

Fig. 1 is a test circuit according to some embodiments of the present disclosure, and as shown in fig. 1, the test circuit 10 includes a triac VT, an inductor L, a first capacitor C1, a first resistor R1, a second resistor R2, and a DC power source DC.

Specifically, the triac VT includes a gate G, a first electrode MT1 and a second electrode MT2, and when a turn-on signal is applied to the gate G, for example, a threshold voltage signal and/or a threshold current signal larger than the thyristor VT, the triac VT is in a conducting state as long as a voltage difference exists between the first electrode MT1 and the second electrode MT2, and flows through the triac VT from a side with a high voltage to a side with a low voltage.

The first end LE1 of the inductor L is electrically connected with the second electrode MT2 of the triac VT; the first electrode plate CE1 of the first capacitor C1 is electrically connected to the second terminal LE2 of the inductor L through a first node J1, and the second electrode plate CE2 of the first capacitor C1 is electrically connected to the first electrode MT1 of the triac VT through a second node J2.

A first resistor R1 is connected in parallel with the first capacitor C1 between the first node J1 and the second node J2, the positive pole of the DC power supply DC is electrically connected to the first node J1 through the second resistor R2, and the negative pole of the DC power supply DC is electrically connected to the second node J2.

In some embodiments, as shown in fig. 1, the test circuit 10 further includes a gate control device GC configured to provide a turn-on signal to the gate G of the triac VT to turn the triac VT on, and when the current drops below the thyristor holding current IH and the device is turned off, a voltage is applied across the device to test the dynamic voltage rise rate (dynamic dv/dt) of the triac VT.

In some embodiments, the turn-on signal is, for example, a pulse signal, in particular, a single pulse signal, which is lower than a threshold value required to trigger the turn-on of the triac VT after the triac VT is triggered to be in the on state. The gate control device GC may be a pulse current source or a pulse voltage source to provide the pulse signal.

In some embodiments, the DC power supply DC is a DC regulated power supply, and the voltage output by the DC regulated power supply is continuously adjustable, for example, continuously adjustable from 0V to 300V, for providing different voltages to the test circuit, so as to test the dynamic voltage rise (dynamic dv/dt) of the triac VT.

In some embodiments, the test circuit 10 further includes a first switch K1, a third resistor R3, and a second capacitor C2 connected in series, and the first switch K1, the third resistor R3, and the second capacitor C2 connected in series are connected in parallel with the triac VT between the first end LE1 of the inductor L and the second node J2. The resistance of the third resistor R3 may be 100 Ω -300 Ω, and the capacitance of the capacitor C2 may be adjustable within a range of 0.001 μ F-1 μ F, such as 0.001 μ F, 0.01 μ F, 0.1 μ F, etc.

In some embodiments, the test circuit 10 further includes a diode D connected in series between the DC power supply DC and the second resistor R2, an anode of the diode D is electrically connected to the positive electrode of the DC power supply DC, and a cathode of the diode D is electrically connected to the second resistor R2. The diode D is arranged to prevent the current in the second resistor R2 from flowing in the reverse direction to the positive pole of the DC power supply DC, and causing damage to the DC power supply DC.

Some embodiments of the present disclosure provide a test system 100, as shown in fig. 2, the test system 100 includes the test circuit 10 in any of the previous embodiments and an oscilloscope 20, the oscilloscope 20 is configured to display the voltage between the first electrode side and the second electrode side of the triac VT and display the current flowing through the first electrode MT 1. Specifically, two voltage probes of the oscilloscope 20 are respectively electrically connected to the wires on two sides of the triac VT, that is, the first electrode side wire and the second electrode side wire, and the current detection transformer is connected to the wire on the first electrode side of the triac VT, and then connected to the oscilloscope 20.

The working principle of the test system 100 will be described in detail below:

first, in the test circuit 10 shown in fig. 1, the dynamic voltage rise rate of the triac VT itself is tested with the first switch K1 in an open state.

Specifically, when the first switch K1 is in an open state, the branch circuit including the first switch K1, the third resistor R3 and the second capacitor C2 connected in series is not connected to the test circuit.

Before the gate control device GC provides a turn-on signal to the gate G of the triac VT, the triac VT is in a non-conducting state, which is equivalent to an open circuit between the first end LE1 of the inductor L and the second node J2, the first resistor R1 and the second resistor R2 are connected in series, the DC power supply DC charges the first capacitor C1, and the voltage charged by the first capacitor is equal to the divided voltage of the first resistor R1. The resistance of the first resistor R1 may be 10K Ω to 100K Ω, and the resistance of the second resistor R2 may be 1K Ω to 10K Ω. For example, in some embodiments, the resistance of the first resistor R1 is, for example, 100K Ω, and the resistance of the second resistor R2 is, for example, 1K Ω, and at this time, the divided voltage of the first resistor R1 is approximately equal to the voltage provided by the DC power source DC.

The gate control device GC then supplies a turn-on signal to the gate G of the triac VT, which is in a conducting state, and the current passing through the triac VT flows from the second electrode MT2 having a higher voltage to the first electrode MT1 having a lower voltage. The resistance of the triac VT is small when it is in the on state, and therefore, the first capacitor C1, the inductor L and the loop in which the triac VT is located form an LC tank, and the first resistor R1 is short-circuited, and since the second resistor R2 has a high resistance value, the current generated by the DC power supply DC through the second resistor R2, the inductor L and the triac VT is small, generally smaller than the holding current of the triac VT, and almost negligible.

In the LC oscillating circuit, the first electrode plate CE1 of the first capacitor C1 has a high potential, the second electrode plate CE2 has a low potential, the first capacitor C1 discharges, the electric field energy decreases, the magnetic field energy increases, the current in the circuit increases, the electric quantity in the first capacitor C1 decreases, the electric field energy is zero when the first capacitor C1 finishes discharging, the magnetic field energy reaches a maximum, the induced current in the circuit reaches a maximum, the first electrode plate CE1 and the second electrode plate CE2 of the first capacitor C1 have the same potential, then the first capacitor C1 is reversely charged, the electric field energy increases, the magnetic field energy decreases, the current in the circuit decreases, the electric quantity in the first capacitor C1 increases, wherein the first electrode plate CE1 has a lower potential relative to the second electrode plate CE 2. When the reverse charging of the first capacitor C1 is completed, the electric field energy is maximized, the magnetic field energy is zero, the induced current in the loop is 0, and since the induced current in the LC oscillating loop undergoes a process of gradually increasing to reach a peak value and then gradually decreasing to 0, when the induced current in the loop approaches 0, the current flowing through the triac VT (from the second electrode MT2 to the first electrode MT1) is smaller than the holding current of the triac VT, which usually causes the triac VT to turn off.

In the above process, the oscilloscope 20 displays the voltage V between the two electrode sides of the triac VT and the current I flowing through the triac VT as shown in fig. 3. Referring to fig. 2, the gate control device GC provides a turn-on signal to the gate G of the triac VT at time t0, the triac VT is in a turn-off state before time t0, a voltage V between two electrode sides of the triac VT is substantially equal to a voltage of the first capacitor C1 charged by the DC power supply DC and approximately equal to an output voltage of the DC power supply DC, the first electrode plate CE1 has a higher potential with respect to the second electrode plate CE2, a potential of the second electrode MT2 side is higher than a potential of the first electrode MT1 side, and a current I flowing through the triac VT is 0A. At time t0, the gate control device GC provides a turn-on signal to the gate G of the triac VT, the triac VT is turned on, the current I flows from the second electrode MT2 to the first electrode MT1 of the triac VT, the first capacitor C1 discharges from time t0 to time t1, the electric field energy decreases, the magnetic field energy increases, the current I gradually increases in the circuit, the electric quantity on the first capacitor C1 decreases, the electric field energy is zero when the first capacitor C1 finishes discharging at time t1, the magnetic field energy reaches a maximum, the current I reaches a peak value in the circuit, the first capacitor C1 is reversely charged from time t1 to time t2, the electric field energy increases, the magnetic field energy decreases, the current I gradually decreases in the circuit, the electric quantity on the first capacitor C1 increases, wherein the first electrode plate CE1 has a lower potential relative to the second electrode plate CE 2. From time t0 to time t2, the triac VT is in the on state, the resistance of the triac VT in the on state is small and substantially negligible, and the voltage V between the two electrode sides of the triac VT is substantially at 0V. At time t2, the current I in the loop decreases to a holding current of the triac VT, which is close to 0A, and at this time, the triac VT is turned off, so that after time t2, the voltage V between the two electrode sides of the triac VT is substantially equal to the voltage after the first capacitor C1 is reversely charged, which is approximately equal to the output voltage of the DC power supply DC, regardless of the loop energy loss, the first electrode plate CE1 has a lower potential with respect to the second electrode plate CE2, the potential on the second electrode MT2 side is lower than the potential on the first electrode MT1 side, and the current I flowing through the triac VT is 0A.

However, when the voltage of the DC power supply DC is high, in the test described above, as shown in fig. 4, before the time t2, the voltage V between the two electrode sides of the triac VT and the current I flowing through the triac VT change similarly to those shown in fig. 3, at the time t2, the current I in the circuit decreases to the holding current of the triac VT, which is close to 0A, at which the triac VT is turned off, the voltage V between the two electrode sides of the triac VT instantaneously changes from 0V to a higher voltage approximately equal to the output of the DC power supply DC, the potential on the second electrode MT2 side is lower than the potential on the first electrode MT1 side, at which the rate of change of the voltage, i.e., the rate of increase dv/dt, is high, causing the triac VT to be turned on again at the instant t2, i.e., at the time t2, the triac VT cannot be turned off due to the high rate of increase dv/dt, after t2, the voltage V between the two electrode sides of the triac VT is substantially at 0V, and the current I in the loop increases gradually in the opposite direction, flowing from the first electrode MT1 to the second electrode MT 2.

The test may be performed by gradually increasing the output voltage of the DC power supply DC with the first switch K1 in the open state, for example, by 0.5V each time, so that the critical output voltage of the DC power supply DC, at which the triac VT in the test circuit is about to fail to turn off, may be obtained.

When the critical output voltage of the DC power supply DC is used, the variation curve of the voltage V between the two electrode sides of the triac VT and the current I flowing through the triac VT is as shown in fig. 5, fig. 6 is an enlarged view of the arrow in fig. 5, and the variation rate dv/dt of the dropped voltage V as shown in fig. 6 can be regarded as the dynamic voltage rise rate of the triac VT itself.

In the above fig. 3-5, the upper curve is the curve of the voltage V between the two electrode sides of the triac VT and the lower curve is the curve of the current I flowing through the triac VT.

In some embodiments, the environment in which the triac VT is normally used is the mains voltage (for example, 220V, 50HZ alternating current), so that the resonant frequency of the resonant circuit formed by the first capacitor C1 and the capacitor L in the test circuit 10 when the triac VT is turned on can be made equal to the mains frequency, for example, 50 HZ.

Then, in the test circuit 10 shown in fig. 1, the dynamic voltage rise rate of the triac VT after being connected in parallel with the series branch of the third resistor R3 and the second capacitor C2 is tested in a similar manner when the first switch K1 is in a closed state, so as to simulate the dynamic voltage rise rate of the triac VT in a normal use, for example, in a case of connecting the capacitors in parallel.

And the dynamic voltage rise rate of the bidirectional thyristor VT when being connected with the capacitors with different capacitance values in parallel can be tested by adjusting the capacitance value of the second capacitor C2 in a similar way.

Some embodiments of the present disclosure provide a test circuit 10 'that is substantially the same as the test circuit 10 described in the previous embodiments, and the differences between the test circuit 10' and the test circuit 10 will be mainly described below.

As shown in fig. 7, the test circuit 10' comprises at least one branch, for example 3, connected in parallel with the triac VT between the first terminal LE1 of the inductance L and the second node J2. Each branch circuit comprises a switch, a resistor and a capacitor which are connected in series. The resistance values of the resistors in different branches are different or the same, and the capacitance values of the capacitors in different branches are different, for example, the resistors in the three branches are all 100 Ω, and the capacitors in the three branches are respectively 0.001 μ F, 0.01 μ F and 0.1 μ F. The parallel connection of the resistor and the capacitor in different branches with the thyristor VT can thus be selected by selectively closing the switches in the branches. The dynamic voltage rise rate of the bidirectional thyristor VT can be tested when the bidirectional thyristor VT is connected with capacitors with different capacitance values in parallel.

Although a few embodiments of the present general inventive concept have been shown and described, it will be appreciated by those skilled in the art that changes may be made in these embodiments, and combinations of the embodiments, without departing from the principles and spirit of the general inventive concept, the scope of which is defined in the appended claims and their equivalents.

Claims

1. A test circuit, comprising:

a triac comprising a gate electrode, a first electrode and a second electrode;

an inductor having a first end electrically connected to the second electrode;

a first electrode plate of the first capacitor is electrically connected with the second end of the inductor through a first node, and a second electrode plate of the first capacitor is electrically connected with the first electrode through a second node;

a first resistor connected in parallel with the first capacitor between a first node and a second node; and

and the anode of the direct current power supply is electrically connected to the first node through the second resistor, and the cathode of the direct current power supply is electrically connected to the second node.

2. The test circuit of claim 1, further comprising:

and the gate control device is used for providing a starting signal for the gate.

3. The test circuit of claim 2, wherein the turn-on signal is a pulsed signal.

4. The test circuit of claim 1, wherein the dc power supply is a regulated dc power supply, the voltage output by the regulated dc power supply being continuously adjustable.

5. The test circuit of any of claims 1-4, further comprising:

the bidirectional thyristor is connected between the first end of the inductor and the second node in parallel.

6. The test circuit of claim 5, wherein the second capacitance is an adjustable capacitance.

7. The test circuit of any of claims 1-4, further comprising:

at least one branch connected in parallel with the triac between the first terminal of the inductance and the second node,

each of the at least one branch circuit comprises a switch, a resistor and a capacitor which are connected in series.

8. The test circuit of any of claims 1-4, further comprising:

a diode connected in series between the DC power supply and the second resistor,

the anode of the diode is electrically connected with the anode of the direct current power supply, and the cathode of the diode is electrically connected with the second resistor.

9. The test circuit of any one of claims 1-4, wherein the first capacitor and the capacitor form a resonant circuit when the triac is conducting, a resonant frequency of the resonant circuit being equal to a mains frequency.

10. A test system, comprising:

the test circuit of any one of claims 1-9; and

and an oscilloscope which displays the voltage between the first electrode side and the second electrode side of the bidirectional thyristor and displays the current flowing through the first electrode.