The scope of thyristors is not less extensive, than, for example, transistors in spite of the fact that they are not so popular. Nevertheless all thyristor schemes put into practice can be broken into four subgroups.
Schemes of switching of tension
Schemes of switching of alternating voltage are called differently power keys. The feature of use of thyristors in this role is that they disseminate the low power as in the course of work they or are closed, or when are open, tension given on them it is not enough. As a rule, in such switching schemes trinistor, that is triode thyristors are used. In this case the operating current moves respectively on the operating trinistor electrode. In a different way the organizations of the similar scheme use diodeof thyristor, that is the dynistor is. A basis of operation of such device is unlocking of the diode at value of tension of the given impulse is higher than unlocking.
Threshold devices
At design of these schemes the possibility of the thyristor to change the state depending on the given tension is used. In the devices constructed on this group of schemes only two parameters are important: time of unlocking and the unlocking tension. The first parameter is especially important in power schemes as in them unlocking is carried out during giving of tension on the thyristor. After a while tension decreases, and current on the thyristor increases. Thus quite big power dissipates.
Schemes of switching of a direct current or tension
Usually thyristors do not use in schemes on a direct current, however the fact that many thyristors have rather big power, is attractive to their application in chains of a direct current or tension. For this opportunity several cunning ways of creation of chains are thought up. For switching of a direct current use the locked thyristors. These devices for some time interrupt passing of current through themselves. One of such schemes is the scheme with two parallel thyristors. In this case the current impulse via one of thyristors is always twice more than current impulse through the second that provides switching of current.
Various experimental schemes
Those which use properties of the thyristor in transition processes and also on sites of negative resistance belong to experimental schemes in which thyristors are used. The fact is that volt-ampere characteristic of the thyristor has the site on which current falls down at increase in tension on it, that is the site with a negative resistance. It allows to use the thyristor as an element with a negative resistance, having set a working point on a branch of the volt-ampere characteristic having negative recession.