SU1582256A1 - Device for protection of load from overvoltages - Google Patents

Abstract

This invention relates to electrical engineering and is intended to protect electronic circuits. The purpose of the invention is to simplify and improve the reliability of the device. When overvoltage occurs, comparator 12 will operate and will give a control signal to the input of thyristor 4, including it. The current flowing through the low-impedance resistor 5 creates a voltage drop across it sufficient to create a current through the winding 3 of the relay causing its contact 2 to trip. Thus, double protection is performed — first the thyristor turns on, shunts the consumer, and then triggers relay and disconnects, using pin 2, the power source from the consumer. 1 hp f-ly, 1 ill.

Description

one

(21) / 1373560 / 24-07

(22) 28J2.87

(46) 07/30/90. Bul 28 (72) V.D. Kharitonov

(53) 621.316.925 (088.8)

(56) USSR Copyright Certificate No. 864411, cl. H 02 H 3/20, 19/9.

USSR Author's Certificate No. 801172, cl. H 02 H 3/20, 1979 (54) DEVICE FOR PROTECTION OF LOAD OVER VOLTAGE

(57) The invention relates to electrical engineering and is intended to protect electronic circuits. The purpose of the invention is to simplify and improve reliability.

operation of the device. When overvoltage occurs, comparator 12 will operate and will give a control signal to the input of thyristor 4, including it. The current flowing through the low-resistance resistor 5 creates a voltage drop across it, sufficient to create a current through the winding 3 of the relay, causing its contact 2 to trip. Thus, double protection is performed — first the thyristor switches on, shunts the consumer, and then the relay operates and disconnects, using pin 2, the power source from the consumer. 1 z.Po f-ly, 1 ill.

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The invention relates to the protection of electronic circuits, for which an increase in the supply voltage (constant or pulsed) is governed by 5 technical conditions of use, and can be used in tuning, testing electronic circuits, for example, performed on integrated circuits.

The purpose of the invention is to simplify and improve the reliability of the device.

The drawing shows the proposed device protecting the load from overvoltages.

The device contains a power source 1, contact 2 relays, the first winding 3 relays, thyristor ft, shunt resistor 5, feedback resistor 20 communication 6, resistive divider 7S 3.9 / resistor 10, semiconductor diode 11, voltage comparator 12 (type 521 SAZ), filter capacitor 13 second relay coil, current pulse driver 15, button 16 (toggle switch), load 17.

The device works as follows.

The voltage from source 1 is supplied 30 to load 17 through the closed contact 2 of the relay. The direct input of the comparator 12 is supplied with voltage, and the divider 7, 8, 3 is less than the voltage drop.

on the semiconductor diode 11. At the same time, from the output of the comparator 12, a low voltage level applied to the thyristor control input does not open the latter.

When the voltage source reaches the value determined by the formula

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The voltage, which is controlled by one of the resistors of the divider 7, 8, 9, at the direct input of the comparator 12 exceeds the fixed voltage on the diode 11 by the value of the comparator being overexcited (a few millivolts), which is activated and produces a high level of control voltage the thyristor b input, the thyristor is turned on. The current flowing through the thyristor creates a voltage drop across the low-resistance resistor 5. This voltage should be less than the maximum allowable load supply voltage, but sufficient to create a current in the first winding 3 of the relay to turn off contact 2,

So, the first factor in protecting the load is when the thyristor is turned on, through which a high current is generated, in which the stabilizing functions of the power supply are violated, which leads to a sharp decrease in the voltage at its output and, consequently, at the load. The relay is then triggered by the current flowing through the first winding 3 and the contact 2 is opened. Second / second occurs The protection factor of the load power source and circuit elements of the device from excessively high thyristor currents - the power source is disconnected from the device by opening the relay contact.

Although the voltage is removed from the winding of the 3 relays, it remains in a state where contact 2 is open for an arbitrarily long time.

In the transient process of turning on the thyristor and the onset of voltage reduction. On divider 1, 8, 9, connected in parallel with the load, the moment of switching the comparator to the initial state may occur due to a decrease in the voltage at its direct input and, therefore, switching off the thyristor, the current of which is insufficient to hold. As the voltage rises again, the process repeats, which leads to the self-oscillation mode of large currents in the power supply and thyristor circuits and, as a result, their failure. To eliminate the auto-oscillation mode, the voltage from the cathode of the thyristor is fed to the direct input of the comparator through a feedback resistor 6 and a divider 7, 8, 9 so that

this voltage in all situations remains above the fixed voltage by means of diode 11 at the reverse input while current flows through the thyristor.

To enable pin 2, i.e. to apply voltage to the load, it is enough to apply a current pulse from the driver 15 by pressing, the button 16 to

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l rizirovannogo relay. Since this part of the scheme does not affect the reliability of protection, its implementation can be arbitrary.

The filter capacitor 13 reduces the effect of impulse noise.

Thus, the proposed device has high-speed double protection and high sensitivity to voltage variation, which is explained by the fact that the device uses a voltage comparator on two transistors having a gain factor greater than one, and the larger the gain factor of the comparator , the higher the sensitivity of the device, in addition, it has increased reliability, since all these advantages are provided without an additional (operational) power source, and higher th sensitivity because the proposed technical solution allows to apply comparator pro- myshenny e.g., type 521 SAZ with gain coefficient is greater than 1000. In addition, no additional power reduces the power consumption of the device.

All these advantages are explained by the corresponding inclusion of two

1582256

Claims (2)

 1. A device for protecting the load from overvoltage, which contains a thyristor, the anode of which is connected via an actuating relay contact to a power source, while the control electrosistor is connected to the output of a voltage comparator, the direct input of which is connected to the first resistive divider voltage, and inverse - to the divider of the reference voltage, both dividers connected to the terminals for connecting to the load, and an actuating relay winding is connected to the thyristor circuit, characterized in that In this case, the newly introduced low-resistance resistor is connected in series with the thyristor and in parallel with which the winding of the mentioned executive relay is connected, the cathode of the thyristor is connected to the second point of the resistive voltage divider via the newly introduced feedback resistor. 2. The device according to claim 1, characterized in that the executive relay is made in the form of a polarized two-winding, the second winding of which is connected to the input relay return current pulse shaper.