SU1241430A1 - Magnetic multivibrator - Google Patents

Abstract

The invention relates to a pulse technique. It can be used in measuring and computing devices as low-power electrical power devices, driving frequency generators, and powering devices for high-power voltage converters. The purpose of the invention — to increase the efficiency of the multivibrator — is achieved by eliminating the continuous power dissipation of the power circuit on the elements of the autoprobe circuit, AjLAysJ from overloads. To achieve this goal, the current transformer (t) is made on a core with a rectangular hysteresis loop, as controlled active elements used thyristors, and between the bases of the switching transistors and the common conclusions of the corresponding thyristors and the first current-limiting resistors are additionally connected to the second current ichivayuschie resistors. The drawing shows: switching transistors 1 and 2, tiristot 3 and 4, power T with all; magnetic; water 5 and windings 9 and 10, T current on the core 6 with a rectangular hysteresis loop, having windings 17 and 18, 19 and 20, resistors 13–16. In the description of the invention, a second embodiment of a multivibrator is given, in which the T current contains an additional second pair of secondary windings. 1 hp f-ly, 4 ill. c & (L

Description

The invention relates to electrical engineering and is intended for using 1) in measuring and computing devices and electric automation devices as low-power power devices, driving high-frequency generators, and devices for driving high-voltage voltage converters. The purpose of the invention is to increase the efficiency of the multivibrator by eliminating the continuous power dissipation of the power circuit on the elements of the overload protection circuit.

FIG. The electrical circuit of the magnetic multivibrator is shown; in fig. 2 - connection of the third pair of current transformer windings; in fig. 3 and 4 - diagrams of processes in both versions of the multivibrator.

The magnetic multivibrator (Fig. 1) contains a pair of switching transistors 1 and 2j, a pair of thyristors 3 and 4, a power transformer with a saturating magnetic actuator 5 and a transformer on a core with a rectangular hysteresis loop 6, through the primary windings of which 7 and 8 collectors switch chapters x transistors 1 2 are connected to the primary windings 9 and 10 of the power transformer 5, the secondary windings of which are 11 and 12 through the first current-limiting resistors 13 and 14 and the second current-limiting resistors 15. and 16 are connected to the base terminals of the switching transistors 1 and 2 and the junction point of the first and second current-limiting resistors are connected to the anodes of thyristors 3 and 4 to .upravl yuschim inputs of which are connected, respectively, their shunt resistors 17 and 18 and secondary windings 19 and 20 of the transformer 6.

I

In the second variant of the multivibrator (Fig. 2), an additional pair of windings 21 and 22 is connected in transformer 6, connected respectively between the bases of the switching transistors 1 and 2 and the second current-limiting resistors 15 and 16.

The operation of the magnetic multivibrator, which is a relaxation generator with one inductive energy storage, falls into two stages.

iia medical stage of operation one of the switching tra} 1zistors, for example, I, is open, the other - respectively

2 - closed. The main npoii.KCC.oM at this stage is the accumulation of magnetic field energy in the inductance Lp of the primary winding of the power transformer 5 and its magnetic reversal under the influence of the supply voltage E applied through the open switching transistor 1 to the primary winding 9. The current through the transistor 1 (ikl) contains the load current component ij reduced to the primary winding and the amplitude-increasing second current component IL, determined by the inductance of the coil 9 of the transformer 5 in the reshma. . the magnetic circuit of the latter on the steep section of the characteristic (see Fig. 3). The indicated current (ii ,. |) is chosen below the starting value of the transformer core, therefore the magnetic core of the latter is in the state of the previous magnetization and the voltage on its windings is absent. Developed by

 Thereby, the voltage on the winding 11 of the transformer 5, through the current-limiting resistor 13 and 15, ensures that the current values are fixed to the base of the switching transistor, which is kept in its effective state. B variant of a multivibrator. (Fig. 2) by transmitting .fixed current of the base circuit by the transistor 1 through the winding 2 of the transformer 6 in its core

5, a holding magnetic field (see FIG. 4) is created, the counter field of the power circuit. Due to this, in the transformer 6, cores with low coercive current values can be used (and the starting core or the same core can be used in multivibrators of different power with a corresponding change in the size of the field-holding turns of the choice of windings of the third pair. Using the base circuit current switchable transistors to create a holding magnetic field possibly due to a fixed value

50 of this current, independent of the load current and determined by the supply voltage of the multivibrator, the constant transformation of this voltage into the base winding of the power transformer and the constant resistance of the current-limiting resistors in the base circuit, as well as due to the synchronous change of polarity

3

The voltage of the base windings causing this current when switching the arms of the multivibrator.

The slow stage of operation of the multivibrator continues in the general case until the collector current of the switching transistor reaches a certain limit value, defined by the circuit and equal to either the product of the base current of the transistor and its gain factor, or the specified resistance of the power circuit. The last variant is used for devices of insignificant power, and the limiting of the power current by the amplifying properties of transistors results in the use of linear power transformers to sign. transistor overloads when approaching the moment of current limiting in the circuit, in this case, the value of this current varies significantly with variations in the gain of transistors versus ambient temperature, etc., which leads to significant changes in the half-period duration of the generated oscillations. In addition, these processes have a strong dependence on the magnitude of the load current. In this connection, power transformers with a saturable magnetic core are used predominantly, while the period of the generated oscillations is practically determined only by the volt-second capacity of the primary winding and the magnitude of the supply voltage, and the fast stage of operation of the multivibrator during the last switching processes of the arms of the latter practically begins with the moment of a sharp increase in the collector current at the presence of the transformer core.

The slow stage of the multivibrator operation ends when the magnetic core of the power transformer 5 reaches a saturated state — the magnetic circuit transitions from the steep portion of its magnetization characteristic to the gentle portion where the inductance of the collector winding decreases sharply (to the saturation inductance L, comparable in magnitude to the inductance LP windings) and, accordingly, the rate of increase of the collector current sharply increases (

t ,, in the diagrams of FIG. 3 and

four). WITH

15

5, About - about

moment in the scheme begins the processes of the fast stage of work, which is completed by switching the arms of the multivibrator. With the beginning of this stage, the rise of the collector current of the open switching transistor I occurs by increasing the rate of increase of the inductive component of the current - component ii, goes into component i (), the rate of increase of which ensures the rapid achievement of the starting current value (i start

25

thirty

50

5s

transformer core 6, after which the magnetization reversal of the latter begins, and the voltage developed on the secondary winding causes a current in the control electrode circuit of the thyristor 3, leading to its activation with some g-hold, defined by 20 characteristics of the thyristor, with respect to time t, . An open thyristor shunts the input of the control circuit of the switching transistor 1, thereby providing a sharp, abrupt decrease in the base current of the latter — the residual current value decreases to a value determined by the resistance of the second current-limiting resistor 15 and the open thyristor threshold voltage difference emitter junction switching transistor. In addition, the current increases. power circuit by increasing current, jj. taken from the winding 11 (see fig.Z). In accordance with the diagrams of FIG. 4, flashing processes in the second variant of the multivibrator, at this time interval, due to the removal of the 40 holding magnetic field, the magnetization of the transformer 6 core increases and the current in the control electrode of the thyristor increases accordingly; however, a 45% decrease in the base current of the transistor 1, in its base region, a high concentration of minority carriers is maintained in connection with the practically applied lateral power transistors mode, therefore its collector current will continue respectively increase growth inductive component i (),

at time t, the magnetization reversal of the core of the transformer 6 is completed with the continuing increase in the collector current of the transformer 1.

At time t due to the depletion of minority carriers of the base area of the switching transistor V and the associated increase in the resistance of its collector circuit, the current of the transistor reaches an extremum and then begins to decrease, resulting in a polarity change in the base windings. 1 and 12 power transformer. Due to this, the polarity-changing voltage on the winding 11 becomes locking and forces the extension of the base region of the transistor 1, a. also leads to the calculation of the thyristor 3; the voltage from the winding 12 opens the second arm of the multivibrator: - switching transistor 2 - at time t, Depending on the frequency properties of the selected switching transistors in the interval from t / to t, a through-current mode can be observed, limited by the values of the inductances rassb. nor in each of the shoulders.

In the absence of a load current (or at its reduced value), processes when switching shoulders occur in a similar way, with the only difference that the time interval increases significantly — in the current diagram, (FIG. 3), this case is shown by a dash-dotted line, The process diagrams in the multivibrator according to the second variant are presented separately for the cases (FIG. 4a) and i 0 (FIG. 4b) and are shown on the same time scale.

In the short circuit mode of the load circuit (which is equivalent to shunting the equivalent inductances L and, accordingly, the Lg primary windings of the power transformer with the load winding dissipation inductance), the multivibrator arms are in emergency switching mode, while the processes in the circuit with time saving this mode are limited only alternating (in accordance with the switchings of pc (ech) fast stages of the multivibrator operation, the function of the current-limiting element in the open transistor collector circuit The torus in this case performs the inductance of the dissipation of the primary winding of the power transformer - the multivibrator goes into ge0 mode.

five

0

five

0

five

0

five

0

five

non-high frequency. The positive inverse, supporting the autogeneration mode, is ensured due to the interconnection between the collector and base windings, which is shunted by the indicated scattering inductance. In this way, a voltage divider is formed from series-connected inductances of the scattering collector winding Lp and reduced: the base winding of the scattering inductance of the load winding Lp ,,,, with the latter through the scattering inductance of the base winding and the limiting resistors basic transistor junction. This mode, which is the most severe for the operation of the multivibrator, allows you to choose the relationship between the parameter-. elements of the auto-protection circuit, ensuring the functioning of the multivibrator in all relasim,

As a result, in the auto-multicast circuit, the pulsed nature of the negative current feedback of the switching transistors is pulsed. The switching of the core with the rectangular loop of gesteresis, on which the transformer 6 is made, takes place on a full cycle until the switching of the arms of the multivibrator is completed; however, the specified transformer, due to its implementation on the core with a rectangular hysteresis loop, performs the functions of a current sensor, a power circuit and a threshold: element, determining the overload moment, and does not dissipate power, thereby achieving the aim of this technical solution, reduction Efficiency of the device. The introduction of additional windings in the transformation-. The torus 6 is forced to re-magnetize the transformer core, which shortens the time of its magnetization reversal. In addition, it expands the possibility of technical regula- tion of the proposed devices with a limited range of cores with a rectangular hysteresis loop,

- Thus, the magnetic multivibrator, compared to the known one, has a higher efficiency value due to the exclusion of: continuous power scattering of the cth circuit as elements of the auto-setup circuit.

Claims (1)

1. Magnetic multivibrator, containing two switching transistors, two control active elements, a power transformer and a current transformer, through the respective primary windings of which the collectors of the switching transistors are connected to the first terminals of the primary windings of the power transformer, the secondary windings of which are connected to the base- emitter circuits of switching transistors and output electrodes of control active elements, parallel to the inputs to connected in parallel are connected resistors and secondary windings of the current transformer, the second terminals of the primary windings of the power transformer are connected to the power bus, the emitters of the switching transistors are connected A ww i. -L eight to a common busbar, characterized by the fact that, in order to improve efficiency by eliminating the continuous power dissipation of the power circuit at the elements of the auto-protection circuit against overloads, the current transformer is high on the core with a rectangular hysteresis loop, as ipravix ix active elements thyristors are used, and between the bases of the switching transistors and the common terminals of the corresponding thyristors and the first current-limiting resistors, the second current-limiting resistors are additionally connected. I. 2, Multivibrator according to claim 1, I, o t - l., Due to the fact that the current transformer additionally contains 20 second pairs of secondary windings, which are connected to the corresponding circuits of the switching transistor bases in series with the second current limiting resistors. (.2 tpat.S a nepff atH. FIG. If