SU426324A1 - KEY - Google Patents

Description

one

This invention relates to the field of automation and measuring technology.

Known keys, in particular, are those in which noise reduction in the load is achieved by circuit complexity. In the known keys containing a controlled blocking generator, a rectifier with a filter and a key on two electrical resistors, in order to reduce the interference from the blocking generator between the connection point of the collectors of the transistors of the key and the common switch, the capacitor is bounded by an additional transistor bypassing which is connected to the control input of the key via a throttler and a delay element. In this way, the reduction of interference from the blocking generator in the load is achieved by significantly complicating the circuit, introducing an additional transistor, capacitor, as well as the driver and delay line; The presence of a feedback circuit between the auxiliary transistor and the input of the switch does not allow for reliable galvanic isolation between the input source and the output.

The aim of the invention is to simplify the key scheme and increase its noise immunity.

This is achieved by the fact that in the proposed key, the output of the controlled generator through

The rectifier and filter are connected to the base of the control transistor, the collector of which is connected via a diode and resistor to another resistor in parallel, connected to the power bus, the latter through the first resistor and the series-connected diodes connected to the base of the switching transistor, the collector of which is connected to By another power supply, the emitters of the control and switching transistors are connected to a common power supply and rectifier emitters, which through resistors are connected to the bases of both transistors .

The drawing shows the scheme of the proposed key.

It contains the terminals 1 and 2 of the input signal, transistors 3 and 4 of a controlled oscillator of rectangular oscillations connected according to a circuit with a common emitter, a boosting capacitor 5, a limiting resistor 6, an isolation transformer 7, diodes 8-11 of a two-loop bridge type rectifier , resistor 12 and capacitor 13 U C-filter, resistors 14 and 15, which ensure reliable locking of the control transistor 16 and the powerful switching transistor 17, resistor 18, which provides protection against arising interference at the output of the control transistor in a closed state,

diodes 19, 20, and 21, providing noise immunity, resistor 22, power control terminal 23 of the control transistor, load 24, power switch terminal 25 of the switching transistor, and a common switch power terminal 26.

The operation of the key is as follows.

Rectangular oscillations from the controlled oscillator through an isolation transformer 7 after straightening and filtering are fed to the base of the control transistor 16, which then becomes saturated. The potential at the connection point of resistor 22 and diodes 19, 20 decreases as a result of current flowing from the power source (terminal 23) through resistor 22, diode 19 and collector-emitter junction of transistor 16. Its value is the level at which by means of bias diodes 20, 21 and the resistor 15 ensures reliable locking of the switching transistor 17. In the absence of a control signal at the key input and the closed transistor 16, the transistor 17 opens with a positive bias applied to its base, which is removed from the resistive-diode divides l, consisting of resistors 15, 22 and diodes 20, 21, the transistor 17 is included

in saturation and closes the chain of passage: the current in the load 24.

Subject invention

A key containing a controlled oscillator of rectangular oscillations, a full-wave bridge type rectifier with a C-filter, control and switching transistors, characterized in that, in order to simplify the circuit and increase noise immunity, the output of the controlled oscillator is connected to the rectifier and filter the base of the control transistor, the collector of which through a diode and a resistor, to which another resistor is connected in parallel, is connected to a power supply connected through the first resistor and series-connected diodes

To the base of the switching transistor, whose collector is connected via a load to a different power supply bus, the emitters of the control and switching transistor are connected to a common power supply and rectifier bus, which is connected to the bases of both transistors through resistors.