JP3038729B2 - Power amplifier output signal control circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier circuit that combines output signals of a plurality of power amplifiers and outputs the combined signal, and in particular, a control circuit for controlling a combined amplifier output signal. About.

[Conventional technology]

Conventionally, in this type of power amplifier circuit, a plurality of power amplifiers are connected in parallel via a splitter and a combiner, an input signal is split by a splitter, and then amplified by each power amplifier. The signal is synthesized by a synthesizer and output.

[Problems to be solved by the invention]

In the above-described conventional power amplifier circuit, when the power of another amplifier is cut off while leaving one or more amplifiers or when the power is input again, the gain by the power amplifier is rapidly reduced or increased. Therefore, the level of the combined output is suddenly changed to an overshoot state, and when this kind of power amplifier circuit is used for a transmitter of a communication device, a communication error occurs or a line is disconnected. There is a problem. In addition, the power amplifier becomes full gain during the rise and fall of the power supply, and the distortion may cause an error or disconnection of the line.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control circuit that prevents an abrupt fluctuation of an output level when a power supply is connected / disconnected, and when the power supply rises and falls, thereby preventing an error and a line disconnection.

[Means for solving the problem]

The power amplifier output signal control circuit of the present invention includes an output signal detection circuit that detects output levels of a plurality of power amplifiers, a level control circuit that controls a gain of each power amplifier based on the detected output levels, A power supply voltage detection circuit that detects a power supply voltage of the amplifier; and a time constant circuit that causes a required time delay in a detection signal of the power supply voltage detection circuit. The level control circuit includes an output level of each power amplifier. Controls the gain of each power amplifier so that is constant, and performs control to gradually increase or decrease the gain of each power amplifier to a gain at which the output level becomes constant based on the output of the time constant circuit. It is composed.

[Action]

In this configuration, the level control circuit controls the gain of the power amplifier according to the time constant set by the time constant circuit in accordance with the fluctuation of the power supply voltage. To prevent overshoot.

〔Example〕

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

FIG. 1 is a block diagram of one embodiment of the present invention. The signal input from the input terminal 1 is split into two signals by the splitter 2 and input to the power amplifiers 3A and 3B, respectively. The output signals amplified by the power amplifiers 3A and 3B are combined by the combiner 4 and output from the output terminal 5.

Output signal detection circuits 6A and 6B are connected to the output sides of the power amplifiers 3A and 3B, respectively, and each output level is detected. The detected output signal levels are input to the level control circuits 7A and 7B, respectively, and the power amplifiers 3A and 7B are controlled by the level control circuits 7A and 7B based on the output signal levels so that the output signal levels become constant. Controls 3B gain.

On the other hand, the voltages of the power supplies 8A and 8B of the power amplifiers 3A and 3B are
The time constant circuit 10 is detected by the power supply voltage detection circuits 9A and 9B.
Input to A and 10B. These time constant circuits 10A and 10B output the power-off and connection state signals to the level control circuits 7A and 7B while delaying them by a predetermined time, and based on these signals, the level amplifiers 3A and 3B Change the gain gradually.

For this reason, when power supply voltage is input, power amplifiers 3A and 3B
, And gradually increase its output signal level to the required level. Further, when the power supply voltage is cut off, the gains of the power amplifiers 3A and 3B are gradually lowered, and the output signal levels thereof are gradually lowered. Therefore, it is possible to prevent the output level from suddenly changing and overshooting when the power supply is connected / disconnected, thereby preventing the occurrence of an error and the disconnection of the circuit when used in a communication device.

Although the above embodiment shows an example in which two power amplifiers are used, the present invention can be similarly applied to a power amplifier circuit including three or more power amplifiers.

〔The invention's effect〕

As described above, the present invention detects a change in the power supply voltage, and the level control circuit controls the gain of the power amplifier based on the time constant set by the time constant circuit, so that the output signal level is gradually increased or decreased. To prevent overshoot of the output signal level when the power supply is connected and disconnected,
This has the effect of preventing occurrence of an error or disconnection of the line.

[Brief description of the drawings]

FIG. 1 is a block diagram of one embodiment of the present invention. 1 ... input terminal, 2 ... branching device, 3A, 3B ... power amplifier, 4 ... synthesizer, 5 ... output terminal, 6A, 6B ... output signal detection circuit, 7A, 7B ... output signal level Control circuit, 8A, 8B
Power supply, 9A, 9B Power supply voltage detection circuit, 10A, 10B Time constant circuit.

Claims (1)

(57) [Claims] 1. A power amplifier circuit for synthesizing outputs of a plurality of power amplifiers, an output signal detection circuit for detecting an output level of each power amplifier, and controlling a gain of each power amplifier based on the detected output level. Level control circuit, a power supply voltage detection circuit for detecting a power supply voltage of each of the power amplifiers, and a time constant circuit for causing a required time delay to a detection signal of the power supply voltage detection circuit. Controlling the gain of each of the power amplifiers so that the output level of each of the power amplifiers is constant, and changing the gain of each of the power amplifiers to a gain at which the output level is constant based on the output of the time constant circuit. A power amplifier output signal control circuit, characterized in that the control is performed so as to gradually raise or lower the power amplifier.