SU762183A1 - Transistorized switch control device - Google Patents

Description

621.384 (088.8)

(72) Authors

inventions

(71) Applicant

A. N. Piskarev, V. A. Sinitsyn and V. S. Tomasov Leningrad Institute of Precise Mechanics and Optics

(54) DEVICE TO CONTROL TRANSISTOR KEY

one

The invention relates to a pulse technique, can be used in voltage regulators, frequency converters, current and voltage inverters.

Known devices for controlling 5 keys, containing keys of switching on and off currents, diodes, capacitor and resistors [1].

Their disadvantage is the impossibility of limiting the instantaneous and average values of current u in case of overloads, short circuits and from through currents.

In addition, a device for controlling a transistor switch, containing a galvanic isolation unit, a protection unit and a matching unit, connected through an amplifier to the base of a transistor switch [2] ·

The disadvantages of this device are power losses, which reduce the efficiency of the 20 key and increase its heating, as well as the possibility of false triggering of the protection unit during actions of interference and parasitic oscillations when the load is disconnected, which reduces the reliability of its operation. 25

In order to increase efficiency and reliability in a device for controlling a transistor switch, containing a protection unit consisting of threshold elements, a matching unit, made on the elements of

VPTB

ladies

2 ............

AND — NOT, power source, capacitor and galvanic isolation unit, the output of which through the first element AND — NOT of the matching unit is connected to the first inputs of the second and third elements AND — NOT, the other inputs of the latter are connected to the outputs of the first and second threshold elements of the protection unit, respectively and the output to the second input of the second element AND — NOT and through the fourth element AND — NOT to the first input of the fifth element AND — NOT, the second input of which is connected to the output of the second threshold element of the protection unit, and the output to the input of the amplifier, first The second and second outputs of which are connected via the respective first and second resistors to the base of the transistor switch, a stand-by multivibrator, a thermal-dependent voltage divider, a display unit, diodes and additional resistors are introduced, the output of the second element AND — NOT the matching unit is connected to the other input of the first element AND —— NOT, the output of the display unit and through the multivibrator - with another, the input of the fourth element AND –NE; the output of the first element AND — NOT through the first diode is connected to the capacitor, the output of the third resistor and the first input of the first threshold element of the protection unit, the second input of which is through the corresponding 762183

Correspondingly, the fourth and fifth resistors are connected to the output of the fifth element AND — NOT and to the collector of the transistor switch. In addition, the first output of the amplifier through the second diode and the sixth resistor connected in parallel is connected to another output of the third resistor. At the same time, the positive bus of the power source is connected to the display unit and the thermo-dependent voltage divider, the midpoint of which is connected to the input of the second threshold element of the protection unit.

The drawing shows a circuit diagram of the device.

The galvanic isolation unit 1 is connected to the matching unit 2, which contains the elements J – NE 3–7. The protection unit 8 consists of threshold elements 9, 10. The circuit also includes a motor 11, an indication unit 12, a standby multivibrator 13, diodes 14, 15, a delay capacitor 16, a thermo-dependent voltage divider 17, resistors 18–23, a power source 24 and a transistor switch 25

The device works as follows.

In the absence of control current at the output of the galvanic isolation unit 1, a high voltage potential is established, corresponding to a logical unit, which, passing through the AND –NE elements 3, 4, 6, 7 and the amplifier 11, leads to the appearance of a blocking potential based on the transistor switch 25 and fast discharge of capacitor 16 through diode 14. When the control current appears, the potential of the voltage at the output of galvanic isolation unit 1 decreases to the level of logic zero. The state of the elements AND — HE 3, 4, 6, 7 and amplifier 11 is changed to the opposite, which leads to the appearance of an unlocking current in the base of the transistor switch 25 and the charge of the capacitor 16. In this case, the threshold element 9 does not work, because the voltage on the capacitor 16 in the process of charging reaches the level of the logical unit after unlocking the transistor switch 25 and the potential at its collector reaches approximately zero level.

In the case of a short circuit in the load of the transistor switch 25, it goes out of saturation, which is accompanied by an increase in the potential of its collector. In this case, a threshold element 9 is switched through a resistor 23, and a logical zero is set at its output. This leads to switching elements AND — NOT 4, 5, launching the standby multivibrator 13 and forming a pulse with a constant amplitude and 3-4 microseconds at its output, under the action of which the open state of the transistor switch 25 is maintained. This prevents the switch 25 from being triggered during short-term not exceeding the duration of the pulse at the output of the standby multivibrator 13, through currents in the presence of interference, as well as currents flowing through the recovering reverse diode and connected in series with it open transistor switch 25, thereby increasing the reliability of the device.

If the increase in the potential of the collector voltage of transistor switch 25 was not caused by a short-term action, but by a prolonged action of the current exceeding the duration of the output pulse of the waiting multivibrator 13, then in this case, by the time the output pulse of the waiting multivibrator 13 ends, the output of the AND-HE 4 and at one of the inputs of the element AND —— HE 3, a logical zero is set, which, together with the elements AND — HE 4, 6, 7 and amplifier 11, blocks the unlocking of the transistor switch 25, and it is locked. From this moment, the display unit 12 is triggered and the capacitor 16 starts to recharge slowly through resistors 21, 22. The control device will be in the unlocked state of transistor switch 25 until the release of the threshold element 9 even when the collector potential of transistor switch 25 drops below a certain voltage level having place with parasitic oscillations on the collector during load shedding.

Release protection occurs when the voltage on the capacitor 16 decreases to the level of release of the threshold element 9.

Thus, until the load short circuit is eliminated, the unlocking current of the base of transistor switch 25 will represent a sequence of pulses with a duration approximately equal to the duration of the output pulse of the waiting multivibrator 13, and the frequency determined by the parameters of the diodes 14, 15 and resistors 18, 21 and 22, which form time-dependent chains.

With a relatively slow heating of the power transistor switch 25 to the maximum allowable temperature, which may be due to changes in external conditions or some other reasons, the voltage at the output of the thermal-dependent potentiometer increases due to an increase in the thermal-dependent resistance installed on the radiator or in the body of the transistor, resulting in the triggering of the threshold element 10, the locking of the transistor switch 25 and through the elements AND — NOT 4, 5 - to the operation of the display unit 12. The normal operation of the transistor switch 25 is restored when the radiator (transistor) is cooled to a predetermined temperature and the threshold element 10 is released,

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The device provides an increase in the efficiency of the transistor switch by reducing losses in the key by 20%, increasing the reliability of operation by preventing the emergency mode due to current and temperature overloads, as well as by preventing false alarms under the action of short-term interference, parasitic voltage fluctuations on the transistor collector key when disconnecting the load and through currents.

Claims (1)

Claim A device for controlling a transistor switch, containing a protection unit consisting of threshold elements, a matching unit made on AND-NOT elements, a power source, a capacitor and a galvanic isolation unit, the output of which is connected to the first inputs of the second and of the third element AND –NE, the other inputs of the latter are connected to the outputs of the first and second threshold elements of the protection unit, respectively, and the output to the second input of the second element AND –– and through the fourth element –– ––– to n The first input of the fifth element is AND — NOT, the second input of which is connected to the output of the second threshold element of the protection unit, and the output to the input of the amplifier, the first and second outputs of which are connected to the base of the transistor switch through the corresponding first and second resistors, In order to increase the efficiency and reliability of the device, a stand-by multivibrator, a thermo-dependent voltage divider, a display unit, diodes and additional resistors are inserted in it, the output of the second element AND — NOT the matching unit is connected to another input the first element AND — NOT; the output of the display unit and through the multivibrator — with another input of the fourth element — AND — NOT; the output of the first element AND — NOT through the first diode is connected to the capacitor, the output of the third resistor and the first input of the first threshold element of the protection unit, the second the input of which through the fourth and fifth resistors respectively is connected to the output of the fifth element AND — NOT and to the collector of the transistor switch, in addition, the first output of the amplifier through the second diode connected in parallel and the sixth resistor is connected to the other at the conclusion of the third resistor, wherein the positive power supply bus is connected with a display unit and a temperature dependent voltage divider, the midpoint of which is connected to the input of the second threshold element protection unit.