Thyristor is a solid-state semiconductor device-key that detects two stable states with low and high conductivity and contains four semiconductor areas with different and alternating types of conductivity. Depending on the method of switching designs differ. The original thyristor is a dual semiconductor diode with a controlled electrode - in the understanding of the device developers.
The history of the creation of the thyristor
We agree, the definition of the thyristor is complex and can cause confusion. Among the developers of the device there was a view about the possibility of a controlled diode: a device that does not allow reverse current, conducting a direct line only on command. A classic thyristor is described. With one-sided conductivity and a controlled electrode, the current of which strongly influences the switching process( transition to the open state).
Wikipedia gives priority to the idea of a thyristor, William Shockley. Allegedly expressed in 1950 year. The authors searched and found a colorful story as opposed to that mentioned. In 2014, one of the founders of the thyristor, Frank "Bill", Gutzwiller shared his story with the public. A lot of questions:
- Who is considered a developer.
- Where to find the number of a patent for a thyristor.
The questions are surprising, because the device is actively pushing the transistor from the spheres of living space. These types are used as keys and regulators in the composition of household appliances. Gutzwiller joined General Electric in 1955.Then the engineer read lectures, considered the Holy Grail the embodiment of the idea of a controlled rectifier. The implication was not a solid-state semiconductor diode, but a device capable of controlling the current flow depending on the control voltage. It was presented as an analogue:
- Tiratrona. Indicates a group of devices, which differs from electronic tubes in the presence of a gas filler inside the tube. In the usual case, the middle grid electrode ignites an arc so that the current flows to the output. In vacuum tubes, the opposite occurs, where the negative potential of the control contact blocks the path of the electrons.
- Motor-generator. The term is incomprehensible to readers of Wikipedia, there is no such thing in a Russian-speaking house. In short, let's say this is a device for converting direct current into alternating current and vice versa. Moreover, the device isolates two circuits when the engine is not running. The concept is stated in the topic about welding inverters.
- Mesh controlled mercury valve. About the device said in the Big Encyclopedia, in the section of oil and gases. The principle of operation is similar to a thyratron. The potential of the control electrode controls the time of occurrence of the arc discharge in a gaseous environment.
So, the idea already existed at the time of 1955.This does not contradict the statement that William Shockley, the developer of the first transistor, could express it. According to Guttsviller, the new invention would replace the listed ones, opening up new areas of application of electronics, including areas of military orientation. The task was set, and when Bell Lab engineers published technical data on a pnpn diode, Gordon Hall enlightened that it resembled a solution to the problem. The staff began to try a novelty, eventually creating a power device with a third electrode, with which the effect on the switching process occurred.
Controlled Diode When Gordon brought a newly created controlled diode to Gutzwiller, thoughts of a better application appeared. For sampling chosen electric motor. The store bought a hand drill. Then the electric tool detected a single speed.
In the laboratory, Gutzwiller assembled a simple starting circuit, which included a potentiometer and a new invention. Power to the drill was supplied through the key. The engineer received the control circuit of the speed of the collector motor through the variable resistance of the thyristor switch. It is still used in food processors today. Rotating the potentiometer knob, the researcher noted the smooth acceleration of the spindle. Unheard of at the time.
Immediately a scientist assembled a dimmer and began to look at how a spiral changes an ordinary light bulb. Gordon and Ray York were delighted with the demonstration and immediately called back to Syracuse about their success. A group of engineers allowed to work exclusively on a new thyristor. In a few weeks, a variant was developed for a 120 V mains voltage for current control at 16 A. It is curious that the invention was not classified, and the world found out about it from free printing( even with photos).General Electronics announced the invention, a note soon appeared in Business Wick.
The scientist was filled up with phone calls in order to obtain details of the thyristor device. Gutzwiller began writing articles for magazines and newspapers, published a collection of first thyristor applications for 50 pages. Then the Controlled Rectifier Manual edition grew to 400 pages and underwent 9 editions. The translation was done in a limited number of languages, but those who wish will understand the essence of the original version.
Then they organized a whole department for research on this topic. A little later followed the invention of the triac. Let Guttsviller received 20 patents in this area, the authors do not see among them the main thing - the thyristor. There is every reason to say that the thyristor is an extremely mysterious invention.
thyristor works It is easy to imagine a pnpn thyristor as a pnp transistor, behind the collector junction of which is an additional layer n of semiconductor, or npn transistor, in front of which emitter is a p-region. As a result, the current flows in a single direction, and at the moment when there is a negative control voltage at the base. According to the characteristics of the device you can see: the higher the control potential, the lower the output voltage will flow.
A thyristor without a control electrode operates on the effect of reversible breakdown of a central pn junction. In this mode, by the way, silicon transistors are often used when they are connected to a circuit with two electrodes out of three. The current will flow until the voltage drops below the avalanche breakdown. The supply of control voltage significantly reduces the level of development of the phenomenon. Moreover, avalanche breakdown continues to go, even if the potential is finally removed from the base. These thyristors compare favorably with transistors, work in a fundamentally different style.
Once the avalanche breakdown effect persists, the voltage in the power circuit is supposed to be increased( to be enough), in addition, the energy of the control circuit is saved. Impulses are suitable for this purpose, appealing to digital electronics. In practice, non-sinusoidal signal generators are often used as such. To lock the thyristor, you need to apply a voltage of reverse polarity to the control electrode.
Readers ask why avalanche breakdown is possible only in a single direction. Indeed, the structure of the thyristor is symmetrical, however, exclusively in the picture. When a current of a different polarity is applied, it will be necessary to pierce two pn junctions, a similar effect has not yet been described in the literature. A lot of interest was also caused by the new invention of Gutzwiller.
The triac is much more interesting. In the Russian-language literature is called a triac from the term "symmetrical thyristor."The device is able to conduct in certain conditions, the current in any direction. The scientist says: once late at night, he thought that it was possible to similarly assemble a device from five alternating regions with different types of conductivity and a shortened emitter. Sketched a sketch, brought to the laboratory, where the performance was confirmed. The term comes from tri - the number of electrodes and ac - alternating current.
The circuit controlled both half-waves of the mains voltage. Today, most of the dimmers for lighting systems work on Triacs. Not bad, considering that at least four decades have passed. On the triac, in contrast to the thyristor, a patent was granted under the name of Gutzwiller under the number 3275909 dated September 27, 1966.In this we indirectly see the confirmation of what was written above - the true inventor did not stake out his own right to a controlled rectifier.
On a crystal, a triac represents two thyristors that are turned on, and physically separated. The base becomes the only common point. Each contact fits immediately to the regions of the two types n and p, to both thyristors simultaneously. The first operates on a positive half wave, and the second on a negative one. The base voltage controls both in turn. This is ac voltage from the phase anode, reduced nominal. Using a potentiometer, it is possible to adjust the resulting amplitude by changing the illumination intensity, engine rotation speed and other parameters.
The device is capable of working similarly in selected conditions and in avalanche breakdown mode. And in both directions. Leave the rest of the tale for professors. Triac was invented by a person who does not understand semiconductor technology. So, the operation of the device must be explained in other categories.
What is a diak
Often a triac goes hand in hand with a diac. Gutzwiller used similar technical solutions. It is a thyristor operating without a control electrode exclusively in avalanche breakdown mode. The design is identical. The origin of the term is clear: di - two electrodes + ac - alternating current. Avalanche test successfully occurs in both directions. The
Quadrac( translated by the author) is a combination of a triac and a diac. In practical applications it is convenient to use these devices together. In particular, the deacon would be able to form voltages for triac switching. It is logical to connect them in the general case. Keep silent about the origin of the term, it is obvious.