JPH08330982A - Power amplifier for transmission - Google Patents

Abstract

PURPOSE: To extend the life or a battery by not supplying an excessive load current from the battery in a power amplifier for transmission fed by the battery. CONSTITUTION: An upper limit value or the output current is preliminarily set in a current control circuit 3 to which power is inputted from a battery 5 and which controls the output current supplied to a power amplification part 2 based on the load variance of the power amplification part 2, and the output current corresponding to the load variance of the power amplification part 2 is supplied when the supplied current value is within a range smaller than the upper limit value which is set beforehand. The current control circuit 3 includes a current limiting means which limits the output current not to supply the output current larger than the upper limit value at the time when the supplied current value reaches the upper limit value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power amplifier for transmission which is supplied with power from a battery and amplifies and outputs an input high frequency signal to an output level at which transmission is possible.

[0002]

2. Description of the Related Art In a general portable telephone or the like which uses a battery as a power source, a circuit called a transmission power amplifier for performing communication with a base station is used. It is characterized in that it has a function of automatically amplifying a weak high-frequency signal (normally a high-frequency signal obtained by modulating a carrier signal of several hundred MHz or more) to a predetermined transmission output level. When the load impedance of the transmission power amplifier fluctuates due to the influence of the human body on the antenna of a mobile phone, etc., the transmission power amplifier uses power to maintain the specified transmission output level with respect to this fluctuation of the load impedance. Since the amplification gain is changed, the transmission output current fluctuates as a result, and an excessive output current sometimes flows.

FIGS. 3A and 3B are diagrams showing changes in the VSWR of the transmission / reception channel depending on the magnitude of the influence of the human body on the antenna. The horizontal axis of FIG. 3 is 0.76 to 1.00 GH
The frequency up to z is shown, and the vertical axis shows VSWR (voltage standing wave ratio). Also, the triangular marks 1 and 2 indicate the receiving channel.
Reference numerals 4 to 4 denote transmission channels, and different frequency bands are assigned to the reception channel and the transmission channel. Further, a center channel (not shown) is provided between the triangle marks 1-2 and 3-4. When the influence of the human body on the antenna increases, the VSWR of the transmission channel that uses the high frequency band increases, and the transmission power efficiency decreases. For example, as shown in FIG. 3A, when VSWR is about 1.5, a transmission power efficiency of about 96% can be obtained.
As shown in FIG. 3B, when the VSWR is about 4.0, the transmission power efficiency drops to about 64%. The output current of the transmission power amplifier also changes due to the change in the transmission power efficiency.

FIG. 4 is a diagram showing changes in the battery load current due to load fluctuations. The circles in the figure show the current values when the load fluctuations are large, and the Xs show the current values when the load fluctuations are small. . For example, a triangular mark 4 out of 3 transmission channels
In the high channel indicated by, the load current when the load change is small is about 525 mA, but the load current when the load change is large increases to about 620 mA.

[0005]

However, in the conventional transmission power amplifier as described above, the specified transmission output level is maintained even when the load of the transmission power amplifier changes due to the influence of the human body on the antenna. Therefore, the load current supplied from the battery to the device becomes excessively large, which causes a problem that the life of the battery is significantly shortened.

[0006]

A transmission power amplifier according to the present invention is a transmission power amplifier which is supplied with power from a battery and amplifies and outputs an input high frequency signal to an output level at which transmission is possible. Current control means for inputting power from the battery and controlling an output current to be supplied to the transmission power amplifier based on a load variation of the transmission power amplifier, wherein an upper limit value of the output current is set in advance and supplied. In the range of the current value to be less than or equal to the upper limit value, the output current corresponding to the load fluctuation of the transmission power amplifier is supplied, but when the supplied current value reaches the upper limit value,
It is provided with a current control means including a current limiting means for limiting the output current so that the output current exceeding the upper limit value is not supplied.

[0007]

According to the present invention, in the power amplifier for transmission which is supplied with power from the battery and amplifies and outputs the input high frequency signal to an output level capable of transmitting, the current control means receives power from the battery. Controlling the output current supplied to the transmission power amplifier based on the load fluctuation of the transmission power amplifier, and based on the upper limit value of the output current preset by a built-in current limiting means, the transmission power amplifier The output current corresponding to the load fluctuation of the transmission power amplifier is supplied within the range of the current value supplied to the upper limit value or less, but when the supplied current value reaches the upper limit value, the output of the upper limit value or more is output. Since the output current is limited so that no current is supplied, an excessive load current is not supplied from the battery, Service life is timed.

[0008]

1 is a diagram showing a configuration example of a power amplifier for transmission according to the present invention, in which 1 is an input terminal, 2 is a power amplifier (also referred to as PA module), 3 is a current control circuit, Reference numeral 4 is a power amplifier for transmission of the present invention including a power amplification unit 2 and a current control circuit 3, 5 is a battery, 6 is an antenna duplexer (which makes an antenna shared by transmission and reception), 7 is an antenna matching circuit, and 8 is Atena. In addition, the current control circuit 2
A specific example of the circuit will be described with reference to FIG. In FIG. 1, the power supply to the power amplifier 2 is not directly supplied from the battery 5 as in the conventional case, but is supplied from the battery 5 to the power amplifier 2 via the current control circuit 3. Is configured.

The current control circuit 3 controls the output current supplied to the power amplification unit 2 on the basis of the load fluctuation of the power amplification unit 2. The upper limit value of the output current supplied is set in advance. , And has a function of limiting the output current so that the output current exceeding the upper limit value is not supplied. That is, the current control circuit 3 changes the load of the power amplifier 2 within a range in which the value of the current supplied to the power amplification unit 2 is equal to or less than the upper limit value of the output current which is set in advance to extend the life of the battery 5. When the current value to be supplied reaches the upper limit value, it operates so as to limit the supply of the output current above the upper limit value.

The operation of FIG. 1 will be described. A weak high-frequency signal input from the preamplifier through the input terminal 1 is power-amplified by the power amplification unit 2 to a transmission output level,
This amplified output is transmitted to the base station as a radio wave via the antenna duplexer 6, the antenna matching circuit 7 and the antenna 8. At the time of this transmission, when the load variation of the power amplification unit 2 occurs due to the influence of the human body on the antenna 8 or the like, the output current supplied from the current control circuit 3 to the current amplification unit 2 exceeds the preset upper limit value. Since the output current is limited so that it does not exist, an excessive current is not supplied from the battery 5 to the load. As a result, the battery life can be extended.

FIG. 2 is a diagram showing an example of a current control circuit according to the present invention. In the figure, Q _{1 to} Q ₃ are transistors,
R _s , R _{1 to} R ₅ are resistors, and C is a capacitor. Further, V _in is an input voltage supplied from the output of the battery 5, V in
_out is the output voltage supplied to the power amplification unit 2, and the resistance R
_s is connected in series with the transistor Q ₃ for detecting the value of the current supplied to the power amplification section 2. The operation of FIG. 2 will be described. The transistor Q ₃ is a transistor for controlling the current supplied to the power amplification unit 2, and is supplied from the output of the smoothing circuit configured by the resistors R ₄ and C to which the input voltage V _in is input via the resistor R _5. A collector current Ic ₃ flows to the emitter side based on the base current Ib ₃ and supplies an output current to the power amplification unit 2.

The voltage drop across the resistor R _s due to the current flowing from the input voltage V _in through the resistor R _s to the transistor Q ₃ becomes the base-emitter voltage Vbe ₁ of the transistor Q ₁ and this voltage Vbe ₁ Based on resistance R ₁
If the base current Ib ₁ flowing through the transistor Q ₁ is sufficient to make the transistor Q ₁ conductive, the transistor Q ₁ becomes conductive, and the voltage generated across the resistor R ₂ caused by this conduction current is the base-emitter of the transistor Q _2. Voltage Vbe
_2, and the transistor Q ₂ as long as sufficient base current Ibe ₂ flowing through the resistor R ₃ on the basis of the voltage Vbe ₂ is to conduct the transistor Q ₂ is turned. The current outputted through the resistor R ₅ from one end of the capacitor C is branched into two, one of which is supplied as a base current Ib ₃ of the transistor Q _3, the other of the collector current of the transistor Q ₂ Ib ₂ Supplied as.

[0013] Thus Figure 2, the collector current Ib ₂ of the transistor Q ₂ is increased, the base current Ib ₃ of the transistor Q ₃ are circuit so reduced is formed. When the input voltage V _in , the resistances R _s , R _{1 to} R ₅ and the value of the capacitor C and the current amplification factors of the transistors Q _{1 to} Q _{3 in} FIG. 2 are properly selected, the transistors Q _{1 to} Q _{3 become} In both cases, when the collector current Ic ₃ of the transistor Q ₃ is supplied as an output current to the power amplification unit 2 in the conductive state, a base current Ib ₃ that can supply the collector current Ic ₃ up to the upper limit value of the output current. Transistor Q ₃
Can be supplied to.

However, the collector current I of the transistor Q ₃
When c ₃ flows slightly beyond the upper limit of the output current, its emitter current Ie ₁ increases due to the increase of the base current Ib ₁ of the transistor Q ₁ due to the increase of the voltage across the resistor R _s , and this current Ie ₁ The base current Ib _{2 of the} transistor Q _{2 is} increased due to the increase of the voltage across the resistor R ₂ due to the increase of
Is increased, and as a result, the collector current I of the transistor Q ₂ is increased.
c ₂ increases. Since the base current Ib ₃ of the transistor Q ₃ decreases due to the increase of the collector current Ic ₂ of the transistor Q _2, the collector current Ic ₃ of the transistor Q ₃ also decreases, and the current limit so that a current exceeding the upper limit value of the output current does not flow. To work.

Note that FIG. 2 shows an example of the current control circuit, and the present invention is not limited to this circuit, and the current limiting is performed so that the output current is not supplied above the preset upper limit value. Any circuit may be used as long as it is a circuit that performs current control including a function.

[0016]

As described above, according to the present invention, in the transmission power amplifier which is supplied with power from the battery and amplifies and outputs the input high frequency signal to an output level capable of transmitting, the current control means is Power is input from the battery, and the output current supplied to the power amplifier for transmission is controlled based on the load fluctuation of the power amplifier for transmission,
Based on the upper limit value of the output current preset by the built-in current limiting means, within a range in which the current value supplied to the transmission power amplifier is equal to or less than the upper limit value, it corresponds to the load fluctuation of the transmission power amplifier. The output current is supplied, but when the supplied current value reaches the upper limit value, the output current is limited so that the output current above the upper limit value is not supplied, so an excessive load current is supplied from the battery. This is not the case, and the effect of extending the life of the battery can be obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of a transmission power amplifier according to the present invention.

FIG. 2 is a diagram showing an example of a current control circuit according to the present invention.

[Fig. 3] VS of transmission / reception channel depending on the magnitude of the human body
It is a figure which shows the change of WR.

FIG. 4 is a diagram showing a change in a battery load current due to a load change.

[Explanation of symbols]

 1 Input Terminal 2 Power Amplifier 3 Current Control Circuit 4 Transmission Power Amplifier 5 Battery 6 Antenna Duplexer 7 Antenna Matching Circuit 8 Antenna

Claims (1)

[Claims] 1. A power amplifier for transmission, which is supplied with power from a battery and amplifies and outputs an input high frequency signal to an output level at which transmission is possible, wherein the power is input from the battery to the power amplifier for transmission. Current control means for controlling the output current to be supplied based on the load fluctuation of the transmission power amplifier, wherein the upper limit value of the output current is set in advance, and the current value to be supplied is within the range of the upper limit value or less, An output current corresponding to the load fluctuation of the transmission power amplifier is supplied, and when the supplied current value reaches the upper limit value, a current limiting means for limiting the output current so as not to supply the output current above the upper limit value is included. A transmission power amplifier comprising a current control means.