JPH0522160A - Power amplifier circuit - Google Patents

Abstract

PURPOSE:To obtain the transmission power amplifier circuit which has high power efficiency and enables stable APC control. CONSTITUTION:This power amplifier circuit is equipped with a power amplifier system composed of plural amplifiers 11, 12 and 13 to amplify input power Pi and an APC circuit to extract one part of output power Po by a directional coupler 14, to compare it with a reference voltage Vr by a comparator 16, to impress an output power control voltage Vc from a control transistor 17 to all the amplifiers 11, 12 and 13 for eliminating the difference and to control the output power Po. Since the voltage Vc impressed to the amplifiers 11, 12 and 13 is changed corresponding to the output power Po, energy is not consumed in vain and since a rise voltage is made high, the APC control is facilitated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier circuit used in a transmission circuit system of a cellular phone, a cordless phone or the like.

[0002]

2. Description of the Related Art Conventionally, this kind of power amplifier circuit has been equipped with an AP.
A power control circuit called C (Automatic Power Control) is provided to control the output power to be constant. FIG. 2 shows the configuration of a conventional power amplifier circuit of this type. In FIG. 2, 1 and 2 are pre-amplifiers, 3
Is a PA (power amplifier) module, 4 is a directional coupler, 5 is a detection circuit, 6 is a comparison circuit, and 7 is a control transistor. The stabilized power supply Vs is applied to the front-stage amplifiers 1 and 2, and the battery power supply Vb and the output power control voltage Vc of the control transistor 7 are applied to the PA module 3. Further, the battery power supply Vb is applied to the collector of the control transistor 7, and the output of the comparison circuit 6 is applied to the base of the control transistor 7.

Next, the operation of the above conventional example will be described.
The input power Pi is applied to the pre-stage amplifier 1, is amplified through the pre-stage amplifier 2 and the PA module 3, and the output power Po is output. A part of the output power Po is picked up by the directional coupler 4, rectified into a direct current through the detection circuit 5, and input to the comparison circuit 6 as a detection voltage. In the comparison circuit 6, the signal coming from the detection circuit 5 is compared with the reference voltage Vr set in advance in this circuit. As a result of the comparison, if the voltage values of the two do not match, the difference between the two signals is It is input to the control transistor 7. The control transistor 7 outputs the output power control voltage Vc until the difference between the signal coming from the detection circuit 5 and the reference voltage Vr disappears.
Is output to adjust the output power Po of the PA module 3.

The output power control voltage Vc is changed by changing its voltage level to output power Po of the PA module 3.
When the signal coming from the detection circuit 5 is smaller than the reference voltage Vr, it is increased, and when it is larger than the reference voltage Vr, it is changed in the decreasing direction. Controlled.

As described above, also in the conventional power amplifier circuit described above, the desired output power can be appropriately obtained by the output power control voltage Vc appropriately operating.

[0006]

However, in the above-described conventional power amplifier circuit, it is necessary to allow a certain amount of current to flow through the preamplifier regardless of the output power, so that the battery usage time is unduly limited. There was a problem that In addition, since the output power control voltage Vc becomes extremely small at low output power, the influence of the variation factor in the circuit becomes relatively large, and it is difficult to secure the stability of the output power. there were.

The present invention solves such a conventional problem and provides an excellent power amplifier circuit which can obtain high power efficiency and can perform stable APC control at low output and high output. It is intended to be provided.

[0008]

In order to achieve the above object, the present invention applies an output power control voltage output from a control transistor to all amplifiers in a power amplification system such as a pre-stage amplifier and a PA module. It is the one.

[0009]

The present invention has the above-mentioned structure.
Since the entire power amplification system operates as if it were one amplifier with respect to the desired output power, that is, since the output power control voltage according to the desired output power is applied, it is necessary to flow an excess current to the preceding amplifier or the like. In addition, the limited battery capacity can be effectively used, and the call time in the wireless telephone or the like can be extended. Secondly, since the rising characteristic of the output power with respect to the output power control voltage starts rising from a voltage relatively higher than 0 volt, there is an effect that the APC control is easy to perform and stable control can be performed.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the present invention. In FIG. 1, 11 and 12 are pre-amplifiers, 1
3 is a PA module, 14 is a directional coupler, 15 is a detection circuit, 16 is a comparison circuit, and 17 is a control transistor. The difference from the conventional example shown in FIG. 2 is that the applied voltages to the pre-stage amplifiers 11 and 12 and the PA module 13 are all output power control voltage V of the control transistor 17.
c, and the battery power source Vb is the control transistor 16
It is only applied to the collector of.

Next, the operation of the above embodiment will be described.
The input power Pi is applied to the pre-stage amplifier 11, is amplified through the pre-stage amplifier 12 and the PA module 13, and the output power Po is output. A part of the output power Po is picked up by the directional coupler 14, rectified into a direct current through the detection circuit 15, and input to the comparison circuit 16 as a detection voltage. In the comparison circuit 16, the signal coming from the detection circuit 15 is the reference voltage Vr preset in this circuit.
If the voltage values of the two signals do not match as a result of the comparison, the difference between the two signals is input to the control transistor 17. The output power control voltage Vc is output from the control transistor 17 until there is no difference between the signal coming from the detection circuit 15 and the reference voltage Vr, and the PA module 1
The output power Po of No. 3 is adjusted.

The output power control voltage Vc is the same as the pre-stage amplifier 11
And 12 and the PA module 13 are evenly applied. Since the applied voltage is a value determined by the signals compared in the comparison circuit 16, it changes depending on the desired output power Po. That is,
These amplifiers 11 have as much voltage as they need, when needed.
Since it is added to 12 and 13, the wasted current is reduced.

Further, the PA module 13 has a property that the output power does not appear at the output end unless a certain threshold value is exceeded, and in this embodiment, the applied voltage of the pre-stage amplifiers 11 and 12 also changes. The module does not operate until the applied voltage rises to some extent until the module 13 rises. As a result, the output power control voltage Vc becomes higher than in the conventional case. Therefore, APC control is easy to perform and stable control can be performed.

As described above, according to the above embodiment, the output power control voltage Vc output from the control transistor 17 is
Pre-stage amplifiers 11 and 12 and PA module 13
Since it is applied to all the amplifiers of the power amplification system of No. 3, each amplifier is applied with a required voltage when necessary according to the desired output power Po, so that the power is not wasted and the battery is not consumed. The life of the power supply Vb can be extended, and the call time in a wireless telephone or the like can be extended. Also, since the rising voltage becomes high, AP
C control becomes easier to perform.

[0015]

As is apparent from the above embodiment, the present invention applies the output power control voltage from the control transistor in the power control circuit to all the amplifiers in the power amplification system. On the other hand, since the entire power amplification system operates as if it were one amplifier, that is, since the output power control voltage according to the desired output power is applied, it is not necessary to supply the surplus current to the pre-stage amplifier, etc. The battery capacity can be effectively used, and the call time in a wireless telephone or the like can be extended. Further, since the rising characteristic of the output power with respect to the output power control voltage starts to rise from a voltage relatively higher than 0 volt, there is an effect that APC control is easy to perform and stable control can be performed.

[Brief description of drawings]

FIG. 1 is a schematic block diagram of a power amplifier circuit according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram of a conventional power amplifier circuit.

[Explanation of symbols]

 11 Pre-Amplifier 12 Pre-Amplifier 13 PA Module 14 Directional Coupler 15 Detection Circuit 16 Comparison Circuit 17 Control Transistor Pi Input Power Po Output Power Vb Battery Power Vr Reference Voltage Vc Output Power Control Voltage

Claims (1)

Claim: What is claimed is: 1. A power amplification system comprising a plurality of amplifiers for amplifying input power, a part of output power is extracted and compared with a reference voltage, and a control transistor is provided so as to eliminate the difference. And a power control circuit for controlling the output power of the power amplification system, wherein the output power control voltage from the control transistor is applied to all the amplifiers of the power amplification system.