SU1317548A1 - Switch-type voltage amplifier with current overload protection - Google Patents

Abstract

The invention relates to electrical engineering and can be used to protect amplifiers in automation, control and control devices. The aim of the invention is to increase the reliability of the protection during a short circuit at the output. The goal is achieved by introducing a comparator, thanks to which the circuit can withstand unlimited short circuits at the output of the amplifier and automatically restores performance and parameters after the overload is removed. 1 il. : AR SL 4 EO

Description

The invention relates to electrical engineering and can be used to protect amplifiers in automation, control, control, etc. devices.

The purpose of the invention is to increase the reliability of the protection operation during a short circuit at the output.

The drawing shows a functional diagram of the device.

The key voltage amplifier with overcurrent protection contains a preamplifier on transistor 1 according to a common emitter circuit, the base of which is connected to the output of the input source 2, and the collector through a resistor 3 to the average output of the resistive voltage divider 4 and resistors 5 and &, connected in parallel to the emitter-collector junction of the output transistor 7, into the emitter circuit of which a current-measuring resistor 8 is connected, and the base is connected to the collector of transistor 1 in series with the comparator output 9, the first input of which is connected to the output of the source 10 of the reference signal, and the second to the middle terminal of the divider 4.

The device works as follows.

In the absence of an input signal, the pre-amplifier (transistor 1) is closed, there is no voltage on resistors 3 and 5. The voltage at the second input of the comparator 9 is higher than at its first input. The output of the comparator is in the zero state, i.e. the comparator output transistor 9 is open. Comparator 9 is prepared for operation.

When a signal arrives at the input of transistor 1, transistor 1 is unlocked, its collector current, through the open comparator 9, enters the base of output transistor 7 and unlocks it. After unlocking the transistor 1, the voltage at the second input of the comparator 9 decreases, but remains above the voltage at the first input. Comparator 9 does not change its state.

As the load current increases, the voltage drop across the current-measuring resistor 8 increases, the voltage across the second input of the comparator 9

begins to decline. At a given value of the voltage drop across the resistor 8 (the maximum current setpoint), the voltage at the second input of the comparator 9 becomes less than the voltage at the signal input specified by the source 10. The comparator 9 switches, its output transistor closes, causing closing

o the output transistor 7. The voltage at the output of the amplifier decreases to zero. Positive feedback through the resistor 6 keeps the comparator 9 in the closed state.

5 When removed from the input of the key signal amplifier, transistor 1 is locked, the current through the resistor 5 decreases, the voltage at the second input of the comparator 9 increases and becomes larger than the voltage at the first input. The output transistor of the comparator 9 is unlocked, however, the base current of the output transistor 7 remains equal to zero, since the transistor 1 is closed. The circuit is ready to re-input.

Thus, due to the introduction of a comparator, the circuit causes an unlimited short-circuit 0 or output of the shortcut and automatically restores the performance of a pair of winds after the overload is removed, which increases its reliability.

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Claims (1)

Invention Formula A key voltage amplifier with overcurrent protection, containing a preamplifier on a transistor according to a common emitter circuit, to the collector of which one output of the resistor is connected, the output transistor of the opposite side of the circuit is connected to the resistor divider in parallel to the emitter-collector circuit voltage, and a current measuring resistor is included in the emitter circuit, and an input Q signal source, which differs in that, in order to increase the reliability, it is equipped with a comparator and a reference voltage source wives whose output is connected to the first  the input of the comparator, the second input of which is connected to the connection point of the average output of the resistive voltage divider with the second output of the resistor, and the code is connected between ba313175484 ZOY of the output transistor and the collector, to which the base of the transistor is connected to a pre-output source of the input signal.  w / n Editor A. Ogar . Compiled by V.YaYurov Tehred M.Hodanich Order 2429/49 Circulation 618 Subscription VNIRSHI of the USSR State Committee for Inventions and Discoveries 113035, Moscow, Zh-35, 4/5 Raushsk nab. Production and printing company, Uzhgorod, st. Project, 4 Proofreader A.Zimokosov