JPH03272208A - High frequency output automatic control circuit - Google Patents

Abstract

PURPOSE:To prevent destruction of a final stage amplifier by detecting an output of a pre-stage amplifier, comparing the detection signal at a differential amplifier section and generating a control signal from a control circuit so as to control the pre-stage amplifier. CONSTITUTION:The automatic control circuit is devised in such a way that a control circuit generates a control signal to control a pre-stage amplifier 2 to attain normal operation of a final stage amplifier 3. An output of the pre-stage amplifier 2 is detected and a detection signal is inputted to the control circuit to control the pre-stage amplifier 2 thereby attaining normal operation of the final stage amplifier 3. When damage or breaking of wire takes place in a circuit component of an output circuit section and detection power is reduced due to the increase in reflection power, an output of the pre-stage amplifier 2 is increased. Thus, the increased value is detected to suppress the power supply voltage to the pre-stage amplifier 2 via the control circuit. Thus, the output transistor(TR) is operated without over-drive or destruction to improve the reliability.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a final stage amplifier of a high frequency high output amplifier, and more particularly to a high frequency output automatic control circuit for preventing destruction of the final stage amplifier.

[Conventional technology]

As shown in FIG. 3, conventionally, the output power 6 is controlled by connecting a capacitor 11 to the output terminal of the filter 5 or by connecting a capacitor 12 to the input terminal of the filter 5. , the output power detected by the combination of the capacitor 17, the power supply 26, the resistor 15, the resistor 14, the diode 13, and the VR16.
, the voltage Vbe of the transistor 21 is controlled by the current flowing through the diode 19, the resistor 20, the transistor 21, and the resistor 22. If the output power 6 fluctuates up or down for some reason, the above control function operates to return the output power 6 to the specified output power value set by the variable resistor 16. For example, when the output power 6 decreases, the detection level decreases, the Vbe of the transistor 21 decreases, and a large amount of current flows through the transistor 23 constituting the differential amplifier. Therefore, the Ib of the transistor 30 increases, and the Vce decreases and the power supply voltage applied to the front-stage amplifier 2 increases, so the output power of the front-stage amplifier 2 increases, the output power of the final-stage amplifier 3 increases, and the output power 6 recovers to the specified output power value.However, For example, when the output power 6 decreases due to an increase in reflected power due to the destruction of the capacitor 11 or 12 or the destruction of the output circuit section such as the filter 5, and the detected power decreases, the control circuit operates as explained above, and the output power of the preamplifier 2 is reduced. The output power, that is, the input power of the final stage amplifier 3 increases.Moreover, since the output transistor of the final stage amplifier 3 continues to operate beyond its rated value, the MT of the output transistor increases.
BF (average lifespan) will be shortened or destroyed.

[Problem to be solved by the invention]

The present invention has been made in view of the above-mentioned problems of the conventional technology, and when the output power of the final stage amplifier 3 continues to operate beyond a preset specified value, the output power is reduced to within the preset specified value. This provides a circuit to suppress this.

[Means to solve the problem]

In order to achieve the above purpose, in a high frequency high power amplifier that detects the output of the high frequency high power amplifier, generates a control signal in a control circuit, controls the front stage amplifier, and operates the final stage amplifier normally, the front stage amplifier The present invention provides an automatic high-frequency output control circuit, which detects the output of the amplifier, inputs the detection signal to the control circuit, controls the front-stage amplifier, and causes the final-stage amplifier to operate normally.

[Effect]

According to the above configuration, when the detected power decreases due to an increase in reflected power when a circuit component in the output circuit section is damaged or disconnected, the output of the front-stage amplifier increases, and this increased value is detected and controlled. The power supply voltage of the preamplifier is suppressed through the circuit.

〔Example〕

Embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of a main part showing an embodiment according to the present invention, and FIG. 2 is a circuit diagram of a main part showing an embodiment of a power amplifier using multiple parallel connections of the same high-frequency output automatic control circuit. . Components having the same functions as those in FIG. 3 are given the same numbers and detailed explanations will be omitted.

In FIG. 1, the output power 6 decreases due to an increase in reflected power due to the destruction of the capacitor 11 or 12 or the destruction or disconnection of the output circuit section such as the filter 5,
When the detected power decreases, the differential circuit of transistors 21 and 23 and the control circuit of transistor 30 operate to
, and the input power applied to the amplification transistor of the final stage amplifier 3 increases beyond the specified value of the transistor. In order to suppress this and bring it to the specified value, diode 3
6. The voltage applied to Vbe of the transistor 21 is increased by the voltage detected by the circuit configuration of the capacitor 37, the resistor 35, the capacitor 34, and the variable resistor 33, thereby increasing the current flowing through the transistor 21. As a result, the current flowing through the transistor 23 constituting the differential amplifier is reduced, Vbe of the transistor 30 is reduced, and the power supply voltage applied to the preamplifier 2 is reduced. As a result, the output power of the pre-stage amplifier 2, that is, the input power of the final-stage amplifier 3 decreases, and the output power of the final-stage amplifier 3 decreases. In this case, the output power value of the final stage amplifier 3 is maintained at a constant value set by the variable resistor 33, and does not exceed the maximum value of the output transistor of the final stage amplifier 3. Note that 1 is an input power, 26 is a tenth power supply, 29 is a + power supply, and 19.31 is a backflow prevention diode.

FIG. 2 shows an example in which the final stage amplifiers 3 are operated in parallel; the output from the previous stage amplifier 2 is divided into two by a divider 40 and input to each final stage amplifier 3, and the amplified output is sent to the combiner 41. be synthesized. The above-described detection circuits are connected to each output section of the distributor 40, and the output signals thereof are combined and connected to the terminal of the transistor 210 of the differential amplifier of the control circuit, and then sent to the front stage amplifier 2 via the control transistor 30.
It is connected to the. These two detection circuits and control circuits have the same circuit configuration as shown in FIG. 1, and their functions and operations are also completely the same.

〔Effect of the invention〕

As described above, in the present invention, when the output power decreases due to damage or disconnection of circuit components in the output section, the control circuit operates to increase the input power of the final stage amplifier and increase the maximum value of the final stage amplifier transistor. Operating the product beyond its limits will shorten its service life or cause damage.

In this case, the output power of the final stage amplifier can be kept within a certain value and the output transistor can be operated without being overdriven or destroyed, thereby improving reliability.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a main part showing an embodiment of an automatic high-frequency output control circuit according to the present invention, and FIG. 2 is a main part showing an embodiment of a power amplifier using multiple parallel connections of the automatic high-frequency output control circuit. It is a circuit diagram. FIG. 3 is a main circuit diagram showing a conventional embodiment. In the figure, ■ is the input power, 2 is the front stage amplifier, 3 is the final stage amplifier, 5 is the filter, 6 is the output power, 11.1 Ibara 17.18
．． 32.34.37 is a capacitor, 13.19.31°36 is a diode, 14.15.20.22.35 is a resistor, 16°33 is a variable resistor, 21.23.30 is a transistor, 26 is a pre-power source, 29 is a pre-power source, 40 is a distributor,
41 is a synthesizer.

Claims (2)

[Claims] (1) Detect the output of the high frequency high power amplifier, compare the detection signals in the differential amplifier section, create a control signal in the control circuit, and control the front stage amplifier.In the high frequency high power amplifier, the output of the front stage amplifier is A high-frequency output automatic control circuit characterized in that the detected signal is detected, the detected signal is compared by the differential amplifier, and the control circuit generates a control signal to control a pre-stage amplifier. (2) When the final stage amplifiers are connected in parallel, the output of the previous stage amplifier is distributed by a divider, each distributed output is detected, the detection signal is input to the control circuit, and the output of the previous stage amplifier is 2. The high frequency output automatic control circuit according to claim 1, wherein the high frequency output automatic control circuit controls: