How to check a dinistor with a multimeter: test circuit using the thyristor ku 202n as an example, check without soldering

Dinistor is an important radioelement in electrical circuits. It is intended for circuits with automatic switching devices, pulse generators, high-frequency signal converters. Due to its low cost and simple design, such a radio component is considered ideal for use in power regulators.

But like any electronic element, it can fail. Therefore, it is extremely important to be able to correctly check the dinistor with a multimeter.

Dinistor assignment

Dinistor is a semiconductor element with two stable states: closed and open. It is made from a semiconductor single crystal with several p-n junctions. In the general case, it can be considered as an electronic key, when one of its state (closed) corresponds to low conductivity, and the other (open) - high.

The dynistor belongs to the "thyristor family" of radioelements and has no fundamental differences with the thyristor. The only thing that

it is distinguished by the conditions for a change in a stable state. Unlike a thyristor, which has three outputs, a dinistor has only two of them, that is, it does not have a control input.

Hence its second name - diode thyristor. The dinistor leads are called anode and cathode. The first is deduced from the extreme p-region, and the second from the n-region.

The invention of thyristors is associated with the name of the English physicist William Bradford Shockley. After the invention of the point transistor, the scientist devoted his experiments to creating a monolithic element. So, in 1949, a prototype of a junction transistor was presented, and the next year Sparks and Teal, assistants Shockley, managed to make a three-layer structure that allows the production of high-frequency radioelements based on p-n transitions. The scientist's research led to the creation of a semiconductor diode called the Shockley diode. Its construction is a four-layer element with a pnpn type structure.

In modern electronics, a dinistor is most often used in the circuit for starting energy-saving lamps and daylight control gears.

In the diagrams and in the literature, the element is designated using the Latin letters VD or VS, and for its graphic the designation is a triangle along with a straight line passing through its middle, symbolizing electrical circuit. As a result, a kind of arrow is formed, indicating the direction of the current flow. Two short lines are drawn perpendicular to a straight line in the middle and near the apex of the triangle. The first denotes the base region and the second denotes the cathode.

Principle of operation

Considering a dinistor as a four-structure element, it can be represented as two interconnected transistors n and p of the conductivity type. For the transistor to work, a current must appear at the base-emitter junction. If no voltage is applied to it, then no current will pass through the radio element. This is due to the fact that the opening of the transistors is controlled by each other. In other words, to open one of these transistors, it is necessary to transfer to the open state another.

A voltage of a certain magnitude must be present between the terminals of the dinistor, which makes it possible to transfer the operation of one of the two transistors to saturation mode. As a result, the second element will open, and the dinistor will begin to pass current.

To transfer the structure to the current cutoff mode, it will be necessary to lower the voltage value, which will lead to the disappearance of the bias current and, accordingly, the base current on the second transistor. The dinistor will stop passing current.

The polarity of the voltage applied to the terminals of the radio component also plays a significant role. When a minus is applied to the anode, the current practically does not pass through the element. This inclusion is called reverse. If the polarity is changed, then a small current will begin to flow through the device - the closing current. The voltage corresponding to it determines the highest value at which the dynistor is in the closed state. To open the dinistor, you need a voltage of the order of tens of volts.

Dinistors, like trinistors, only pass current in one direction. In order for the current to flow in both directions, they are switched on in an anti-parallel circuit. Also, a five-layer pnpnp type structure can be used for this.

Device characteristics

In order to correctly check a thyristor with a multimeter, it is necessary not only to understand the principle of its operation, but also to know its main characteristics. The most significant parameter of an element is its current-voltage characteristic (VAC). It clearly shows the dependence of the current flow through the device on the voltage applied to its terminals. The I – V characteristic of a dinistor is S-shaped. This characteristic is divided into six zones:

1. The site is open. In this gap, the element has practically no resistance to the current passing through it. Its conductivity is maximum. This zone ends with a point at which the current stops flowing.
2. Area of ​​negative resistance. It provokes the onset of an avalanche breakdown.
3. Breakdown of the collector junction. At this interval, the element operates in the avalanche breakdown mode, which causes a sharp decrease in the voltage at its terminals.
4. Direct connection section. In this region, the dinistor is closed, since the potential difference applied to its terminals is less than that required for a breakdown to occur.
5. The fifth and sixth sections describe the operation of the device in the lower half of the I - V characteristic and correspond to the states of reverse switching on and breakdown of the element.

Analyzing the I - V characteristic, we can conclude that the operation of a dinistor is similar to a diode, but, in contrast to the latter, to open it, it is necessary to apply a voltage that exceeds the diode value by several once. In this case, a dinistor is characterized by a number of parameters that determine its application in electrical circuits. Its main characteristics include the following values:

1. The potential difference in the open state. Usually indicated in relation to the value of the opening current. Volt is used as its unit of measurement.
2. The smallest on-state current. This value depends on the temperature of the device and decreases with its increase. Measured in milliamperes.
3. Switching time. It is characterized by a period of time during which the operating mode of the device changes from one stable state to another. This value is in microseconds.
4. Locked state current. Determined by the reverse voltage value and rarely exceeds 500 μA.
5. Capacity. This parameter characterizes the generalized parasitic capacitance arising in the element. Because of it, the use of the device in high-frequency circuits is limited and the speed of switching operating modes is reduced. It is measured in picofarads.
6. Holding current. Indicates the amount at which the dinistor is open. The unit of measurement is ampere.

Device diagnostics

When checking a radio element for serviceability, a multimeter is most often used. The ease of use of this measuring device is due to its versatility. With its help, you can ring an element for breakdown or measure the levels of threshold voltages. It does not matter if the analog or digital type of meter is used.

To obtain correct measurement results, you will need to prepare the multimeter for work. The whole essence of the preparatory operation comes down to checking the tester's battery. When working with a digital device it is necessary to pay attention to the icon of the flashing battery. If it is, then the battery needs to be replaced. For an analog device, before operation, the arrow is set to zero. If this is not possible, then the battery must be replaced.

For a reliable result when measuring with a multimeter, it is also advisable to monitor the ambient temperature. This is due to the fact that with increasing temperature, the conductivity of semiconductors increases. The optimum temperature for measurement is around 22 ° C.

Dial-up without watering

Due to the specifics of the device, it is not so easy to check the triac with a multimeter without unsoldering. For a complete check, an electrical circuit is used, which allows a number of necessary measurements to be carried out. The only thing that can be done with a multimeter is to check it for a clear breakdown.

To do this, the tester switches to the diode vertebrae mode, after which the measuring probes touch the dinistor leads. At any polarity, the tester should show an open circuit, which will indicate the absence of a breakdown in the cell. But this will not guarantee the serviceability of the device. If, during measurement, the multimeter shows a short circuit, then such a thyristor can no longer be checked, since it is faulty.

In this case, you should be aware that it will be incorrect to ring a radio element in the circuit, since other radio elements that affect the measurements can be connected in parallel with its output. By making a simple dial, it is necessary to disconnect at least one of the inputs of the dinistor from the printed circuit board. In order to check the dinistor without unsoldering, you can use the capabilities of the circuit in which it is installed.

It is known that the radioelement opens only when a certain voltage level is applied to its outputs, so you can try to reach this threshold value.

In this case, the multimeter switches to voltage measurement mode for testing. The measurement range is selected depending on the expected breakdown voltage. The measuring probes are connected in parallel to the element terminals, after which the signal level is measured. If a voltage jump occurs when the input signal changes, then this will indicate the breakdown voltage of the dinistor, that is, its performance.

Test circuit

To gain confidence in the performance of an element, radio amateurs use test circuits. They are of varying degrees of complexity, which ultimately affects the accuracy of the result. The simplest scheme consists of three elements:

• regulated power supply;
• resistor;
• indicator.

An LED can be used as the latter. Having assembled such a scheme, they begin to check. A tester is connected in parallel to the element in the voltage measurement mode.

For example, to check the KU202N thyristor with a multimeter, the output voltage level is first set to about twenty volts. In this case, the LED in the circuit should not light up. Then the level rises slowly until the LED lights up. The glow of the indicator indicates that the dinistor opened and an electric current began to pass through it. To close it, the voltage level is reduced.

The value of the potential difference at which the change in the operating mode occurs is the maximum opening voltage. In this case, the tester should show a value of about 50 volts, while the input signal level will be about 60 volts. Any type of resistor can be used. Its purpose is to limit the amount of current passing through the LED.

Knowing how to check the KU 202 thyristor, you can check any other type of thyristor, dinistor or triac. It should be noted that professionals use an oscilloscope instead of a multimeter. A test attachment is used in conjunction with it. The measured elements are connected to sockets X5 and X6. When using a thyristor, its control element is connected to socket X7. For elements with a control output, the voltage is changed using a variable resistor R4. If the radioelement is intact, then the oscillogram should be the same as in the figure.