SU1436110A1 - Power source protection device - Google Patents

Abstract

The invention relates to electrical engineering, in particular to protection devices. The purpose of the invention is to increase the reliability of work and expand the scope. At rated input voltage and no overcurrent, transistor 1 is fully open. Comparison node transistor 7 is locked. When the output voltage exceeds the value given by the core element 9, the transistor 7 and the protection transistor 5 open, locking the control transistor 1, which limits the load current. When overloaded or short-circuited, the voltage on the current sensor 2 opens the protective transistor 5, which also leads to a current limitation. When a significant load is caused by a current limiting to an undervoltage, the threshold element 17 switches, which leads to an overload indication by the LED 19. The aim of the invention is to provide the possibility of limiting voltage surges on the load and using the device in protection mode and in stabilization mode. 2 hp f-ly, 1 ill. (WITH

Description

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The invention relates to electrical engineering and can be used in various power supply systems for radio equipment, computing equipment and communication facilities.

The purpose of the invention is to increase the reliability of work and expand the scope.

The drawing shows a circuit for protecting a power source.

The device contains a regulating transistor 1J connected in series to the power bus; control transistor 19, resistor 4 bias 5 connected by a single output to the base of control transistor 1 protective, transistor 5, junction collector emitter shunt base-emitter: Uhlir transistor 1, a control resistor 6, vklk ;; - Cheney parallel to the base-emitter. the transition of the protective transistor 5, the transistor 7 of the comparison circuit whose collector, through the first flattering resistor 8 is connected to the base of the protective transistor 5, the second supporting element 9j is connected between the terrain of the transistor 7 of the comparison circuit and the common bus, the second ballast resistor 10 connected between in turn device and the second supporting element 9, divider 1 of the output voltage, input connected to the output of the device and the common power, and output to the base of the transistor 7 of the comparison circuit delay circuit 12, confining the current torus 13. in series between the input and output and the cond: capacitor 14, connected between the input of the circuit and the common bus, shunt the transistor 15 on by the collector-emitter junction parallel to the second; the reference element 9, and the base through the resistor 16 connected to the output of the delay circuit 12, the threshold element 175 IAC) connected to the output of the output voltage divider 11, and the output to the input of the delay circuit 12 the source 18 constant voltage connected between the second output resistors 4 cm20

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. - 2S 49 j th., „-;.,. and a common bus, the output of the constant voltage source 18 is connected to the power output of the threshold element 17, the overload indication element 19, connected in series to the collector circuit of the shunt transistor 15.

The device works as follows.

With a rated input voltage and no voltage; current overload, the regulating transistor 1 is fully open and is in saturation, the depth of which is determined by the bias resistor 4, the voltage drop across the current sensor 2 and the base-emitter junction of the regulating element 1 is less than the one specified by the first supporting element 3. The voltage limiting level is set by the second supporting element 9s fed from the input through the second ballast resistor 10, and in normal mode the voltage removed from

the output voltage divider 11 is insufficient for unlocking the comparison circuit transistor s 7, with the result that the latter is locked, there is no current in its collector circuit. Thus, there is no current in the base circuit of the protection transistor 5, it is closed and does not affect the operation of the regulating relay transistor 1. At the input of the threshold element 17 there is a high potential perceived by it as logical 1, therefore a low potential is formed at its output — a logical O, a capacitor 14 of the delay circuit 12, and a transistor. 15 is closed, the current in the optical fiber 19 is absent, and the latter does not indicate an Overload signal. In this mode, the voltage drop in the input and output is minimal, and the power j is dissipated by the regulating transistor, is minimized.

 When the input voltage is set by the value given by the second supporting element 9 and the transfer coefficient of the output voltage divider 11, the comparison transistor 7 opens, a current arises in its collector circuit, which decreases due to the voltage drop on the ballast resistor 8 and the control resistor b unlocks the protective transistor 5, which, shunt the base-zmitterny transition regulating transistor 1,

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leads to its locking and limiting the output voltage.

Under the action of overcurrent or short circuit of the load, the voltage drop on the resistive current sensor 2 increases to the level determined by the first supporting element 3 and the base-emitter voltage value of the control transistor 1, as a result of which the latter is energized, limiting the current in the load at the level determined by the resistance value of the resistor sensor 2 current. Since the increase in the load current and the transition to the limiting mode of the current regulating element 1 are accompanied by a fall of the output voltage on the yarn, a logical signal O is generated at the input of the threshold element 17, which translates its output into the logical 1 state, i.e. at its output a high potential is formed, which is fed to the input of the delay circuit 12. The capacitor 14 is charged through the current limiting resistor 13, as a result of which the output of the delay circuit 12 after a time determined by the constant KS circuit generates a high potential, unlocking the shunt transistor 15, the collector current of which is ignited Light-emitting diode

19, the indicating signal. Overload. The output voltage threshold is sharply lowered, as a result of which the control transistor 1 is closed similarly to the indicated overvoltage mode, and the device disconnects the load from the mains. If the time of the overload action is shorter than the time for the formation of a high potential, then at the output cxei-ft of the delay, the device returns to its original state.

If the response threshold of the device at the input voltage is set below the minimum input, taking into account the voltage drop on the regulating element 1 in the linear mode, then the device works as a continuous constant voltage stabilizer with current overload protection and with trigger protection against short circuit at the exit. Improving the stability of the output voltage can, if necessary, be achieved by known methods, replacing, for example, the transistor 7 of the comparison circuit with a differential or operational amplifier.

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Using the invention as an input voltage limiter at a predetermined level, having a minimum voltage drop, input-output at nominal mode, and also as a continuous voltage regulator with simultaneous protection against overcurrent and short-circuits, expands its scope. Thus, using the invention as a surge protection device at the input of a power source powered from a power supply network eliminates overvoltages at its inputs and applies low-voltage elements in its circuit. In addition, the limitation of the input current allows to provide a p.pavny input to the mode of the protected power source and. eliminate current surges in the primary network with

Claims (3)

Invention Formula one . A power supply protection device containing a control transistor connected in series to the power bus, the emitter of which through a resistor current sensor, is connected to the input terminal, and the collector is connected to the output terminal, the first supporting element, which is connected between the input terminal and the base of the regulating transistor. an offset resistor, one output connected to the regulating transistor base, a protective transistor, an emitter connected to the emitter, and a collector to the regulating transistor base, the control resistor, between the base and the emitter of the protective transistor, a comparison made on the transistor, the collector of which is connected, whose second ballast resistor to the base of the protective transistor through the first ballast resistor, the second ballast resistor connected between the emitter of the transistor of the comparison circuit and the common transistor , included between the input terminal and the emitter of the transistor circuit. we are a comparison, an output voltage divider whose output is connected to the base of the comparison circuit's transistor, a delay node that is time-fulfilled — a master capacitor and a current limiting resistor, and one of the terminals of the current limiting resistor is one of the terminals of the master terminal The capacitor is the output of the delay node, another capacitor lead is connected to the common bus, and the other output of the current limiting resistor is the input of the delay knob, characterized in that, in order to increase the reliability and extend the application, a threshold element is not included , stabil-Litron, resistor and shunt transistor, whose collector-emitter type is connected in parallel to the second support element, and the base | iepe3 resistor is connected to the output of the Delay unit, the input of the threshold element is connected to the output of the div eat | vghodnogo voltage and output - to 10.6 the input of the delay node, the zener diode being connected between the common bus and the other output of the bias resistor, to which the supply terminal of the threshold element is connected. 2. The device according to claim 1, characterized in that the threshold element is made on the logical element NOT, 3. The device according to claim 1, characterized in that, in order to indicate an overcurrent mode and a short circuit, a light-emitting diode is inserted into it, connected by an anode to the emitter of the transistor of the comparison circuit, and by a cathode to the collector of the shunt transistor. Compiled by V. Baranov Editor I. Shulla Tehred M. Khodanych Proofreader M. Maksimishinets Order 5647/48 Circulation 866 VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Subscription