JP3636066B2 - Transistor power amplifier - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a transistor power amplifier, and more particularly to a transistor power amplifier that measures the idle current of a transistor in operation.
[0002]
[Prior art]
Usually, in a high-frequency high-power amplifier used for a television broadcaster or a wireless transmitter, a transistor (including an FET) operating in the AB class is used as an amplifying element. FIG. 6 is a circuit diagram showing an example of a conventional transistor power amplifier.
[0003]
In the conventional example of FIG. 6, the transistor 3 of the amplifying element, RF1 to which the OFDM signal is input, RF2 of the output power from the transistor 3, and the average current supplied from the power source (+ VDD) 8 to the collector of the transistor 3 And an average current sensor 6 for measuring the current and a bias circuit 13 connected to the base of the transistor 3.
[0004]
Next, the operation of the conventional example will be described. First, the flow of the OFDM signal is input from the RF input 1 to the transistor 3, amplified, and then output from the RF output 2. At that time, the current Ids supplied to the transistor 3 can be measured by the average current sensor 6.
[0005]
[Problems to be solved by the invention]
The problems (problems) of the conventional transistor power amplifier described above will be described below.
[0006]
First, in the conventional example, the idle current at normal temperature cannot be measured after the start of the main broadcast, that is, during power amplification. The reason is that the Ids varies depending on the output power because the transistor of the large power amplifier performs AB class operation.
[0007]
Secondly, in the conventional example, the idle current cannot be finely adjusted / reset during the main broadcast. The reason is that the conventional circuit cannot measure the idle current at room temperature during power amplification and does not have the function of fine adjustment and resetting.
[0008]
Thirdly, in the conventional example, when the power is reduced during the operation of the amplifier, it is difficult to confirm the damage state of the transistor. The reason for this is that when the output power of the transistor is reduced in the normal AB class operation, the Ids also decreases accordingly. Therefore, it is difficult to determine whether the power is reduced or the transistor is damaged. Because.
[0009]
An object of the present invention is to provide a transistor power amplifier capable of measuring an idle current of a transistor at normal temperature in an operating state of the power amplifier.
[0010]
[Means for Solving the Problems]
The transistor power amplifier of the present invention includes a semiconductor element for power amplification that operates in class A to class AB, a current supplied to the semiconductor element, and a radio frequency (RF) signal input to the semiconductor element. Means for measuring a current that fluctuates at high speed (fast current), means for measuring an average current supplied to the semiconductor element, and multiplying the average current by a power supply voltage supplied to the semiconductor element, Means for calculating DC input power that is average power consumption, means for measuring RF input power that is input average power of the RF signal, and RF output power that is average output power of the RF signal output from the semiconductor element means for measuring, means for calculating the power consumption of the semiconductor device by adding the RF input power to the DC input power subtracting the RF output power, Means for measuring the temperature of the serial semiconductor device, the temperature and the means for calculating a junction temperature of the semiconductor device during operation from the heat resistance and the power consumption of the semiconductor device, the high-speed current during operation, the junction temperature , and from said high-speed current and the conversion table memory in advance set the idle current value at normal temperature of the junction temperature of the semiconductor device in correspondence, and means for calculating the idle current at the normal temperature of the semiconductor device during operation It is characterized by having.
[0011]
Further, the average transistor power amplifier of the present invention, a transistor for power amplification operating in class A to class AB, and fast current sensor for measuring the high-speed current supplied to the transistor, which is supplied to the transistor the average current sensor for measuring current, an input signal detector for outputting measuring the RF input power which is input to the transistor, and outputs the measuring the RF output power of the RF signal outputted from the transistor Based on the output signal detector, the temperature sensor that measures and outputs the temperature of the transistor in operation, the high-speed current in operation, the junction temperature, and the conversion table memory, the room temperature of the transistor in operation and having an arithmetic unit for calculating and outputting an idle current value at.
[0012]
In the transistor power amplifier according to the present invention, the conversion table memory corresponds to each combination of the transistor junction temperature (Tj) and the high-speed current value, and the RF signal is not input, at the room temperature. An idle current is set.
[0013]
The transistor power amplifier according to the present invention further includes a monitor that displays a numerical value of the idle current at normal temperature output from the arithmetic unit.
[0014]
The transistor power amplifier of the present invention is characterized by comprising means for adjusting the idle current supplied to the transistor based on the numerical value of the idle current at normal temperature . The transistor power amplifier according to the present invention includes a bias circuit that inputs an idle current value from the arithmetic unit and automatically adjusts a voltage supplied to the transistor.
[0015]
The transistor power amplifier according to the present invention is characterized in that a thermocouple whose resistance value changes with temperature change is attached as the temperature sensor close to the flange of the transistor.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of an embodiment of the present invention.
[0017]
In this embodiment, a power amplification transistor 3 operating in class A to class AB and a high-speed fluctuation (hereinafter referred to as a high-speed current) for measuring a signal current amplified by the transistor 3 is measured at high speed. The current sensor 7, the average current sensor 6 for measuring the average current flowing into the transistor 3, and the average power of the RF input 1 of the OFDM (Orthogonal Frequency Division Multiplexing) signal used for digital broadcasting are measured and output. An input signal detector 4, an output signal detector 5 that measures and outputs the average power of the RF output 2 of the signal output from the transistor 3, and measures and outputs the temperature at which the transistor 3 is released during operation. It is represented by the temperature sensor 9, the high-speed current of the above measurement, the average current, the average power of the RF input / output signal, and the temperature information and the conversion table preset in the memory 11. An arithmetic unit 10 for outputting the idle current value of the transistor 3 at normal temperature, a monitor 12 for displaying the measurement result and the idle current value, a bias current circuit 13 for adjusting the idle current of the transistor 3 by feeding back the measurement result, It is configured to have + VDD (power supply) 8 supplied to the transistor 3 and the bias circuit 13.
[0018]
Next, the operation of this embodiment will be described. Normally, a transistor 3 operating in the AB class is used as an amplifying element in a high power amplifier used for television broadcasting. FIG. 2 is a correlation diagram between the output power of the transistor and the current (Ids). The current (hereinafter referred to as Ids) mA supplied to the transistor 3 tends to increase as the output power (Power) dBm increases. . The Ids when the output power becomes 0 is particularly called an idle current. First, an OFDM signal used for digital broadcasting is input from the RF input 1 to the transistor 3, amplified, and then output from the RF output 2. At that time, the average input power is measured by the input signal detector 4, the average output power is measured by the output signal detector 5, and the average current of the transistor 3 is measured by the average current sensor 6. Usually, the power consumed when the transistor 3 amplifies the power is calculated by the equations (1) and (2).
Power consumption = DC input power + RF input power-RF output power (1)
DC input power = (+ VDD8) × (value of average current sensor 6: Ids) (2)
FIG. 3 is a waveform diagram showing a comparison between the RF signal of this embodiment and the current (Ids) flowing through the transistor. In the transistor 3, (A) shows the RF (OFDM signal) output 2 when the average power is constant on the time axis. It is an example of the envelope at the time of measuring by (t). When Ids (mA) is measured simultaneously at this time, the average current sensor 6 measures the average value of Ids, as shown in (C). However, when the measurement is performed using the high-speed current sensor 7, the waveform of Ids accompanying the high-speed amplitude fluctuation of the power as shown in FIG. 2B can be measured according to FIG. Therefore, the value of the high-speed current sensor at the moment when the RF level in (A) becomes 0 becomes the idle current value, and this idle current value is transferred to the arithmetic unit 10.
[0019]
FIG. 4 is a correlation diagram between Ids and Tj of the transistor of this embodiment. As can be seen from FIG. 4, the relationship between Ids of a general transistor and the temperature (junction temperature: Tj) in the case is Ids ( mA) increases in proportion to the increase in Tj (° C.). Therefore, when the transistor generates heat, the current value obtained by measuring the instantaneous Ids when the envelope of the RF signal is 0 as described above is different from the idle current in the measurement state at room temperature.
[0020]
FIG. 5 is a diagram showing the relationship between the Tj of the transistor of this embodiment and the idle current at room temperature. From the junction temperature Tj of the transistor and the Ids value at that temperature, there is no RF signal (at room temperature). If the idle current is measured in advance and a conversion table is created, the idle current at normal temperature can be derived from the conversion table. Here, the junction temperature Tj follows the following equation (3).
Tj = ( power consumption × thermal resistance) + base plate temperature (3)
However, the temperature of the base plate (heat radiating plate) to which the transistor is attached is a value measured by the temperature sensor 9 attached to the base plate to which the transistor is attached, and the thermal resistance is a value determined by the transistor.
[0021]
As the temperature sensor, a thermocouple type sensor whose electrical output value changes in response to temperature fluctuations is attached so as to be in close contact with a flange (metal base portion = base plate) of a transistor (FET) with a screw. A temperature sensor is provided in the FET case. Then, a conversion table of relational data as in the example of FIG. 5 is stored in the memory 11, and the arithmetic device 10 can equivalently measure the idle current at normal temperature by performing arithmetic processing on various measured information. it can.
[0022]
Further, by feeding back the idle current information output from the arithmetic unit 10 to the bias current circuit 13, the idle current value of the transistor 3 can be automatically corrected to the optimum value.
[0023]
Further, since the idle current at normal temperature can be displayed on the monitor 12, when the idle current value is set by an operation input, if the information in the memory 11 is used contrary to the measurement, the bias current circuit 13 Since the voltage to be applied to the base of the transistor 3 can be changed, the idle current value can be finely adjusted or reset.
[0024]
In this embodiment, the input RF signal is described as an OFDM signal. However, even in a CDMA (Code Division Multiple Access) or QAM (Quadrature Amplitude Modulation) signal, the envelope of the high-speed current is “0”. If the signal has a moment indicating the level, it can be similarly implemented.
[0025]
【The invention's effect】
As described above, according to the present invention, a semiconductor element for power amplification operating in class A or class B, means for measuring a high-speed current supplied to the semiconductor element, and the semiconductor element simultaneously with the high-speed current Means for measuring an average current supplied to the semiconductor element; means for measuring a temperature at which the semiconductor element is released during operation; and the semiconductor element is in operation by the measured high-speed current, the average current, and the temperature. In addition, there is an effect described below by having a means for measuring the idle current at normal temperature.
[0026]
The first effect is that the idle current can be measured without interrupting the digital broadcast during the main broadcast. The reason is that the idle current value in the normal temperature state can be calculated by measuring the current Ids at the moment when the power consumption of the transistor and the envelope of the RF signal become 0 level and using the conversion table.
[0027]
The second effect is that the idle current can be finely adjusted and reset without interrupting the digital broadcast during the main broadcast. The reason is that it is used contrary to the case of measuring the conversion table data in the memory. This is because the idle current value can be finely adjusted and reset by changing the voltage applied to the base of the transistor.
[0028]
A third effect is that a transistor breakage state can be confirmed during operation of the power amplifier. The reason is that the Ids of a normal AB class transistor depends on the output power, so it is difficult to determine whether the power has been reduced or the transistor has been damaged by simply measuring the operating current. This is because it can be easily determined by measuring the idle current value at room temperature.
[Brief description of the drawings]
FIG. 1 is a block diagram of an embodiment of the present invention.
FIG. 2 is a correlation diagram between output power and current (Ids) of operation in the AB class of the transistor of this example.
FIG. 3 is a waveform diagram showing a comparison between an RF signal of this example and a current (Ids) flowing through a transistor.
FIG. 4 is a correlation diagram showing changes in transistor current with temperature in the present example.
FIG. 5 is a diagram showing the relationship between the junction temperature and the idle current at normal temperature in the present embodiment.
FIG. 6 is a circuit diagram of an example of a conventional transistor power amplifier.
[Explanation of symbols]
1 RF input 2 RF output 3 Transistor 4 Input signal detector 5 Output signal detector 6 Average current sensor 7 High-speed current sensor 8 + VDD (power supply)
9 Temperature Sensor 10 Computing Device 11 Memory 12 Monitor 13 Bias Current Circuit

Claims (7)

A power amplifying semiconductor element operating in class A to class AB and a current supplied to the semiconductor element, which varies at high speed in accordance with a radio frequency (RF) signal input to the semiconductor element (high-speed current) ), A means for measuring an average current supplied to the semiconductor element, and a DC input power which is an average power consumption of the semiconductor element by multiplying the average current by a power supply voltage supplied to the semiconductor element. Means for calculating RF input power, which is the average input power of the RF signal, means for measuring RF output power, which is the average output power of the RF signal output from the semiconductor element, and the DC means for calculating the power consumption of the semiconductor device by adding the RF input power to the input power subtracting the RF output power, means for measuring the temperature of the semiconductor element Means for calculating a junction temperature of the semiconductor element in operation from the temperature and thermal resistance and the power consumption of the semiconductor device, the high-speed current during operation, the junction temperature, and the high speed current and the junction temperature and a conversion table memory in correspondence to preset idle current value at normal temperature of the semiconductor element, a transistor power amplifier, characterized in that it comprises a means for calculating the idle current at the normal temperature of the semiconductor device during operation . A transistor for power amplification operating in class A to class AB, and fast current sensor for measuring the high-speed current supplied to the transistor, and the average current sensor for measuring the average current supplied to the transistor, wherein An input signal detector for measuring and outputting the RF input power input to the transistor; an output signal detector for measuring and outputting the RF output power of the RF signal output from the transistor; Based on the temperature sensor that measures and outputs the temperature of the transistor, the high-speed current during operation, the junction temperature, and the conversion table memory, calculates and outputs the idle current value of the transistor during operation at normal temperature 2. The transistor power amplifier according to claim 1, further comprising an arithmetic unit that performs the operation.   In the conversion table memory, the idle current at normal temperature in a state where the RF signal is not input is set corresponding to each combination of a transistor junction temperature (Tj) and the high-speed current value. The transistor power amplifier according to claim 2.   4. The transistor power amplifier according to claim 2, further comprising a monitor for displaying a numerical value of the idle current at normal temperature output from the arithmetic unit. 5. The transistor power amplifier according to claim 4, further comprising means for adjusting an idle current supplied to the transistor based on a numerical value of the idle current at normal temperature .   4. The transistor power amplifier according to claim 2, further comprising a bias circuit for inputting an idle current value at normal temperature from the arithmetic unit and automatically adjusting a voltage supplied to the transistor.   3. The transistor power amplifier according to claim 2, wherein a thermocouple whose resistance value changes with temperature change is attached as the temperature sensor close to the flange of the transistor.

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