RU201519U1 - Tracking system amplifier USS-2-02 - Google Patents

Abstract

Utility model The amplifier of the tracking system belongs to the field of electrical engineering. The technical result of the utility model is to reduce the weight of the product by reducing the number of radioelements while maintaining the tactical and technical characteristics and overall dimensions. For this, an amplifier of the tracking system is proposed, consisting, among other things, of a preliminary stage on an operational amplifier (OA) and an output stage, assembled on two complementary transistors (VT1, VT2) according to the scheme of a push-pull emitter follower, while the output of the OA is connected to the bases of transistors VT1 and VT2, the collectors of transistors VT1 and VT2, respectively, through resistors R7 and R8 are connected to the positive power bus, the diodes VD1 and VD3 are cathodes connected to the positive power bus, the anodes are connected to the cathodes of diodes VD2 and VD4, which are connected by anodes to the positive power bus, point connection of diodes VD1 and VD2 is connected to the first input of the op-amp and to the resistor R5, which limits the first input voltage signal at the level of the power supply, the connection point of the diodes VD3 and VD4 is connected to the second input of the op-amp and to the resistor R6, which limits the second input voltage signal at the level power supply. 2 ill.

Description

The utility model relates to the field of electrical engineering, namely to amplifying devices and can be used to amplify AC signals with a frequency of 400 Hz to the value required to control two-phase AC motors used in automatic control systems for aircraft [1]. The device is not intended for independent use at the facility, but must be installed as part of a certified product.

The known design of the servo system amplifier with a balanced input and an unbalanced output (USS-2). The disadvantage of this amplifier is its structural complexity, due to the use of obsolete radio elements, low manufacturability, as well as unstable operation at reduced voltage. The technical task of the utility model is to ensure the reliable operation of the amplifier and to improve the performance characteristics.

To solve this problem, a variant version of the tracking system amplifier is proposed, consisting of a preliminary stage on an operational amplifier (OA) and an output stage assembled on complementary transistors according to a push-pull emitter follower scheme, characterized in that the circuit uses VD1 - VD4 diodes, resistors R5, R6 are designed to limit input voltage signals at the level of the power supply, and the blocking capacitor C1 serves to ensure high stability of the output operating point and eliminate parasitic feedback through the power supply at a high frequency; the circuit uses parallel negative voltage feedback, carried out by two resistors R1 and R2, designed to stabilize the operating point of the output and the gain; resistors R3, R4 create a common input point, and resistors R7, R8 serve to protect the collector circuits of the output transistors from exceeding electrical loads in operation.

The amplifier of the tracking system, consisting of a preliminary stage on an operational amplifier (OA) and an output stage, assembled on two complementary transistors (VT1, VT2) according to the scheme of a push-pull emitter follower, characterized in that the output of the OA is connected to the bases of transistors VT1 and VT2, collectors of transistors VT1 and VT2, respectively, through resistors R7 and R8 are connected to the positive power bus, the diodes VD1 and VD3 are cathodes connected to the positive power bus, the anodes to the cathodes of the diodes VD2 and VD4, which are anodes connected to the positive power bus, the connection point of the diodes VD1 and VD2 is connected to the first input of the op-amp and to the resistor R5 limiting the first voltage input signal at the power supply level, the junction point of the diodes VD3 and VD4 is connected to the second input of the op-amp and to the resistor R6 limiting the second voltage input signal at the power supply level, the third and fourth inputs The op amps are connected to the positive power rail, capacitor C1 is connected between the terminals of the positive power bus, while the output of the amplifier and two resistors R1 and R2 connected in series are connected to the junction point of the emitters of transistors VT1 and VT2, forming a voltage feedback, the output of which is connected to the first input signal and resistor R5, and the resistor R3 is the first output connected to the positive power rail, the second terminal to the first terminal of the resistor R4, the second terminal of which is connected to the negative power rail, the junction point of the resistors R3 and R4 is connected to the common input point.

New in the device of the servo amplifier is that the design provides for a simplified circuit using a modern electronic component base. The technical result of the utility model is to reduce the weight of the product by reducing the number of radioelements while maintaining the tactical and technical characteristics and overall dimensions. Structurally, the servo amplifier is a functional block with bulk wiring and printed circuit board. The output transistors are glued to the aluminum base with a compound that has a thermally conductive filler.

The criterion for using amplifiers with a printed circuit board or with a heat sink is the base temperature, which, under the operating conditions specified in the design documentation, should not exceed + 105 ° С.

The assembled product is covered with a polyamide casing. The amplifier, as a component, can be structurally fastened and soldered into the printed circuit board of the incoming object, when used on a load with a maximum output power not exceeding 1 VA. When using a load of more than 1 VA, the amplifier must be installed on a heat sink. The minimum size of the heat sink when tested at a temperature of + 85 ° C should not be less than 60 × 60 × 3 mm. In an object, the amplifier is mounted in any position and fixed with two screws M 2.5 thread.

The description of the operation of the USS-2 amplifier and the proposed amplifier of the tracking system is set out below, the electrical schematic diagrams are attached.

FIG. 1 shows an electrical schematic diagram of the USS-2 amplifier, consisting of a pre-voltage amplifier assembled on an operational amplifier (OA) [3], low-power transistors - T1, T2, a transistor operating in class AB - T3 and a push-pull output power amplifier on transistors T4 and T5, T6. The use of an operational amplifier (OA) at the input makes it possible to sum signals at one or simultaneously at two differential inputs (inverted and non-inverted). At high levels of input signals Ivx = 1.5 V, an input limiter must be used. The USS-2 amplifier uses an input limiter made on diodes D8, D9 (pin 2).

To power the operational amplifier, a stabilized and filtered voltage of ± 5.6 V is used, which is removed from the zener diodes D1 and D2 using limiting resistances consisting of resistors R3, R4 and R5, R6 connected in parallel. One of the main parameters of the amplifier is the gain. To increase the gain, composite transistors are used, consisting of T4 and T6. Resistor R13, bypassing the base-emitter junction of transistor T3, is designed to select the initial collector current of transistor T1, equal to ≈ 1 mA. Resistor R7 is designed to limit the collector current T1, the value of which, sufficient to saturate the transistor T3, should not exceed the maximum permissible collector current T1.

To exclude the possibility of the appearance of through-current pulses, resistors R19 and R20 are included in the emitter circuit of the output transistors. When the output transistors operate on an inductive load (motor control winding), a negative voltage pulse appears, which, at the moment of opening the output transistor, creates voltages at the base-emitter junction that exceed the permissible ones. To limit the reverse voltage, diodes D6 and D7 are placed in the collector-emitter circuit of each output transistor. Capacitors C4 and C5 are included to filter the variable component from the "common entry point" relative to the power supply. The USS-2 amplifier uses parallel negative voltage feedback, carried out by two resistors R17 and R18, designed to stabilize the operating point of the output (stabilization of the output constant voltage) and the gain.

For stable operation of the amplifier with feedback coverage, frequency correction is applied, which in the low frequency region is carried out by elements C3, R11 and additional correction elements C2, R12. In the region of higher frequencies, the frequency response is corrected by elements C1 and R1, as well as by a series-connected chain R = 51 Ohm and C = 0.1 μF, which is connected to the load (motor control winding).

FIG. 2 shows an electrical schematic diagram of the amplifier of the proposed servo system amplifier, with a symmetrical input and an unbalanced output, consisting of a preliminary stage on the DA1 microcircuit [4] - DA1 and an output stage assembled on complementary transistors of the type 2T831V - VT1 and 2T830V - VT2 according to the push-pull emitter scheme repeater.

Unlike the amplifier circuit (USS-2), the use of such a circuit makes it possible to reduce the output impedance of the amplifier. In conventional amplifiers, when the transistors of the final stage are turned on in this way, the shape of the output voltage is distorted - a step is observed on the oscillogram, which is characteristic of the operation of transistors without an initial bias. The large margin of the op-amp gain and deep negative feedback from the amplifier output to its input leads to linearization of the device operation. The op-amp directly compares the input and output signals and automatically shifts the operating point of the amplifying transistor at every moment, so that the output signal is undistorted. Diodes VD1 - VD4, resistors R5, R6 are designed to limit input voltage signals at the power supply level. In the proposed servo system amplifier, pin 2 "input limiter" is absent. The blocking capacitor C1 serves to provide

high stability of the operating point of the output and elimination of parasitic feedback through the power supply at high frequency. In the proposed amplifier of the tracking system, a parallel negative voltage feedback is used, carried out by two resistors R1 and R2, designed to stabilize the operating point of the output and the gain. Resistors R3, R4 create a common entry point. Resistors R7, R8 are used to protect the collector circuits of the output transistors from exceeding electrical loads in operation. Stable operation of the servo amplifier on the engine control winding is maintained with a gain in the range from 200 to 2000. When the amplifier operates from an on-board network of 27 V ± 10%, it is necessary to use a circuit when the input and output do not have a common point both with each other and with power supply.

Information sources

1.D.A. Braslavsky, S.S. Logunov. Aviation instruments. Mechanical engineering. M. 1964.

2. Amplifier of the tracking system USS-2, USS-2-02. Technical conditions 6S2.548.008 TU.

3. Operational amplifier. Radio. No. 10. 1974.

4. Integrated microcircuits 140UD6A. Technical conditions AEYAR.431130.171-04TU.

Claims (1)

The amplifier of the tracking system, consisting of a preliminary stage on an operational amplifier (OA) and an output stage, assembled on two complementary transistors (VT1, VT2) according to the scheme of a push-pull emitter follower, characterized in that the output of the OA is connected to the bases of transistors VT1 and VT2, collectors of transistors VT1 and VT2, respectively, through resistors R7 and R8 are connected to the positive power bus, the diodes VD1 and VD3 are connected by cathodes to the positive power bus, the anodes are connected to the cathodes of diodes VD2 and VD4, which are connected by anodes to the positive power bus, the connection point of the diodes VD1 and VD2 is connected to the first input of the op-amp and to the resistor R5 limiting the first voltage input signal at the power supply level, the junction point of the diodes VD3 and VD4 is connected to the second input of the op-amp and to the resistor R6 limiting the second voltage input signal at the power supply level, the third and fourth op-amp inputs are connected to the positive power bus, capacitor C1 is connected to at the terminals of the positive power bus, while the output of the amplifier and two resistors R1 and R2 connected in series are connected to the junction point of the emitters of transistors VT1 and VT2, forming a voltage feedback, the output of which is connected to the first input signal and the resistor R5, and the resistor R3 is the first output connected to the positive power rail, the second terminal to the first terminal of the resistor R4, the second terminal of which is connected to the negative power rail, the junction point of the resistors R3 and R4 is connected to the common input point.

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