JPH0666599B2 - Power amplifier circuit - Google Patents

Description

The present invention relates to a power amplifier circuit, and more particularly to a power amplifier circuit used in a power amplifier unit of a transmitter or the like of a mobile communication device.

[Conventional technology]

A block diagram of an example of a conventional power amplifier circuit is shown in FIG.

This circuit transmits a variable attenuator 1 that controls the amount of attenuation of an input signal V _I by a control signal V _C , a power amplifier 3 that power-amplifies this output, and an output of the power amplifier 3 to an output terminal 12. Along with this, a detection unit 4 that outputs an output monitoring signal V _S of a DC voltage corresponding to this output power, and a temperature detection unit 8 that detects heat generated from the power amplification unit 3 via a radiator and outputs a control signal V _C. It is configured to have and.

In a normal state, the attenuation amount of the variable attenuator 1 is set to the minimum, and the high frequency input signal V _I input to the input terminal 11 is hardly attenuated by the variable attenuator 1 and the power amplifier 3
And the power is amplified. The output power of the power amplification unit 3 is input to the detection unit 4, and the detection unit 4 transmits this output power to the output terminal 12 and also generates the output monitoring signal V _S of the DC voltage corresponding to this output power. The output monitoring signal _{V S}
Is supplied to an output drop detection circuit provided externally, and is used as an output drop alarm (usually generated at a point of -3 dB in a normal state) to determine abnormality of the power amplification unit.

The temperature detection unit 8 constantly detects the temperature of the radiator of the power amplification unit 3, and if the temperature exceeds a preset temperature, the power amplification unit 3 is determined to be abnormal and the variable attenuator is detected. The control signal V _C is sent to 1 to increase the attenuation amount of the variable attenuator 1 to a preset value. Therefore, in this case, the output power P _{O at the} output terminal 12 is forcibly reduced, heat generation of the power amplification unit 3 is suppressed, and the power amplification unit 3 is protected.

[Problems to be solved by the invention]

In a power amplifier circuit that employs such a method based on temperature detection, if it is set not to detect a temperature abnormality due to high temperature aging within the temperature specifications, it may not be detected at the time of abnormality, and conversely it is likely to be detected at the time of abnormality. If such a setting is made, the malfunction of abnormal detection is likely to occur even in a normal state, and there is a drawback that temperature setting is very difficult.

In addition, if the collector side matching circuit of the power amplification unit 3, particularly the collector side matching circuit of the final stage transistor, is in a mismatched state for some reason and the output drops within the range in which the output drop alarm is not sent, the temperature detection point is detected. In some cases, the temperature in the vicinity of the collector lead of the final stage transistor of the power amplifying unit 3 may be the reflected wave. May cause abnormal heating, and if it is operated for a long time in this state, it will lead to a secondary failure that the collector lead and the printed board around it will burn out, resulting in an unrepairable state. There was a drawback.

Although the output drop alarm is not sent, if the output drops to the level just before it is sent out, the unmanned station continues to operate until it is maintained, and the same problem as described above occurs. It was

An object of the present invention is to provide a power amplification circuit capable of removing a difficult temperature setting, accurately detecting an abnormality, protecting a power amplification unit, and preventing a failure from progressing.

[Means for solving problems]

The power amplification circuit of the present invention includes a variable attenuator that controls the attenuation amount of an input signal to a predetermined value when the control signal is at the first level and to increase it when the control signal is at the second level, and a variable attenuator. A first detector that transmits the output of the attenuator to the next stage and outputs a detection signal at a level corresponding to the power of the output, and a power amplifier that amplifies the output transmitted from the first detector. And a second detection unit that outputs an output monitoring signal of a level corresponding to the output power of the power amplification unit, and a third detection signal when the detection signal is smaller than the first reference signal. When the level is larger than the first level, the first comparing section which outputs the first binary signal which becomes the fourth level, and the output monitoring signal is compared with the second reference signal, and when the output monitoring signal is smaller, When the third level is larger, the second level becomes the fourth level. A second comparator for outputting a value signal,
The exclusive OR operation of the first and second binary signals is performed, and when the first and second binary signals are at the same level, the first level is obtained, and when the different levels are different, the second level is obtained. And a control unit that outputs a control signal.

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

The amount of attenuation of the variable attenuator 1 is set to the minimum when the control signal V _C is normal at the first level, and the high-frequency input signal V _I input to the input terminal 11 is almost absent in the variable attenuator 1. It is input to the first detection unit 2 without being attenuated. First
The detection unit 2 generates a DC voltage detection signal corresponding to the input power and at the same time transmits the input power to the power amplification unit 3, and the power amplification unit 3 amplifies the power. The output power of the power amplification unit 3 is input to the second detection unit 4, and the second detection unit 4
Is the output monitoring signal V _S of the DC voltage corresponding to this output power
And at the same time, the output power is transmitted to the output terminal 12.

The detection signal generated by the first detection unit 2 is the first comparison unit 5
Is compared with the first reference voltage V _R1 and is smaller than the reference voltage V _{R1 at a} third level (for example, low level), and when larger than the first reference voltage V _R1 , at a fourth level (for example, high level) first binary signal. On the other hand, the output monitoring signal V _S generated by the second detector 4 is supplied to the output drop detection circuit provided outside and used for the judgment of the output drop alarm and at the same time the second comparison The second binary signal of the third level (low level) is compared with the second reference voltage V _R2 in the section 6 and is smaller than the reference voltage V _R2 , and the fourth level (high level) when it is larger. Is output as. These binary signals are applied to the control unit 7 which performs an exclusive OR operation, and the control unit 7 causes the variable attenuating unit 1 to detect that the first and second binary signals have the same level according to the above operation result. The control signal V _C of the first level is output when the levels are different from each other, and the control signal V _C of the second level is output when the levels are different from each other. Increase the amount of attenuation to a preset value.

That is, considering the power amplification unit 3 as a reference, the first detection unit 2 detects the input power of the power amplification unit 3 and the second detection unit 4 detects the output power of the power amplification unit 3. Then, when the power amplification section 3 is in a normal operation state or in a non-input state, the outputs of the first and second comparison sections 5 and 6 are binary signals of the same level. Therefore, the result of the exclusive OR operation of the control unit 7 becomes the same first level, for example, the low level in any of the above cases,
The amount of attenuation of the variable attenuator 1 remains set to the minimum.

On the other hand, if the power amplifier 3 fails and the output drops, the output of the second detector 4, that is, the DC voltage of the output monitoring signal V _S correspondingly drops below the value during normal operation. ,
Since the third level (low level) is set to the fourth level (high level) in the normal state compared with the second reference voltage V _R2 set in advance by the second comparison section 6, abnormalities are easy to occur. Can be detected. Therefore, in this case, the first and second binary signals input to the control unit 7 have different levels from each other, and as a result of the exclusive OR operation of the control unit 7, the second level, for example, a high level. And variable attenuator 1
The attenuation amount of is increased to a preset value.

Therefore, the input power of the power amplification unit 3 is reduced and the output power P _O of the output terminal 12 is also reduced, so that the progress of the failure can be prevented.

Note that the control signal V _C is designed to hold that state once it becomes an abnormal state.

〔The invention's effect〕

As described above, the present invention simultaneously monitors the input power to the power amplification unit and the output power from the power amplification unit, and performs an exclusive OR operation by these detection signals to determine the input power to the power amplification unit. By controlling, there is an effect that a difficult temperature setting becomes unnecessary, an abnormality of the power amplification unit can be accurately detected, and an output can be forcibly reduced at the time of abnormality to prevent the progress of the failure. Further, since the control is performed by the exclusive OR operation, even when the input power of the power amplifier is not detected but the power amplifier is in the self-oscillation state where the output power is detected. There is also an effect that it can be detected.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is a block diagram showing an example of a conventional power amplifier circuit. 1 ... Variable attenuator, 2 ... Detector, 3 ... Power amplifier,
4 ... Detector, 5,6 ... Comparison, 7 ... Control, 8 ...
Temperature detector.

Claims (1)

[Claims] 1. A variable attenuator for controlling an attenuation amount of an input signal so as to be set to a predetermined value when the control signal has a first level and to increase when a control signal has a second level, and a variable attenuator of the variable attenuator. A first detector for transmitting the output to the next stage and outputting a detection signal of a level corresponding to the power of the output;
A power amplifier for power amplifying the output transmitted from the detector, a second detector for outputting an output monitoring signal of a level corresponding to the output power of the power amplifier, and the detection signal as a first reference. When the detected signal is smaller than the detected signal and the third level is larger when the detected signal is smaller, a first comparing unit that outputs a first binary signal that has a fourth level, and the output monitor signal A second comparing section that outputs a second binary signal that has a third level when the output monitoring signal is smaller than the reference signal and has a third level when the output monitoring signal is larger; and the first and second The binary OR signal of
And a control unit that outputs the control signal that has a first level when the second binary signal has the same level and a second level when the second binary signal has a different level.