JP2020136988A - Current detection resistance switching apparatus for apc circuit - Google Patents

Abstract

To provide a current detection resistance switching apparatus for an APC circuit, capable of achieving characteristics that, when an output power setting selected by a user is high, a value of a current detection resistance is set to a small value in order to increase a power efficiency, and when the output power setting is low, the value of the current detection resistance is set to a large value in order to adjust an accurate output power.SOLUTION: A current detection resistance switching apparatus for an APC circuit, comprises: a current detection resistance 3 (31 and 32) which can change a combined resistance connected to a power source line of a power amplifier 2 in serial; an APC circuit 4 that performs a current detection by measuring a potential difference of both ends of the current detection resistance 3, and controls an output power of the power amplifier 2 in constant by applying a negative feed-back on the basis of the current detection value; and a control circuit 5 that generates a control signal to the APC circuit 4 and a control signal for switching the combined resistance of the current detection resistance on the basis of an output power setting of the power amplifier 2 selected by a user.SELECTED DRAWING: Figure 1

Description

The present invention relates to a current detection resistor switching device for an APC circuit used to control a power amplifier.

Conventionally, in a current detection circuit that detects a current by providing a current detection resistor in the circuit to detect the current flowing through a load or the like and measuring the potential difference between the resistors, the current detection resistor is controlled based on the detected current. It is known to do so (see, for example, Patent Documents 1, 2 and 3).

Patent Document 1 describes the first and second resistors connected in series for detecting the current flowing through the load, the switches connected in parallel to these resistors, and the current flowing through these resistors. A current detection circuit is shown which includes a detector for detection and switches a resistor for detection by turning a switch exclusively on / off according to the magnitude of the detected current.

According to Patent Document 2, in an inverter circuit connected to a rotary electric machine, by switching a group of switching elements connected in parallel according to a detection current, the current is detected by one current detection resistor at a small current, and the current detection accuracy. It has been shown that when a large current is generated, the current is divided into a plurality of current detection resistors to suppress heat generation per switching element.

Patent Document 3 describes a detection current value of a resistor connected in series for detecting a current flowing through a gas concentration sensor in a gas concentration detection device using a gas concentration sensor that outputs a current signal corresponding to the gas concentration. It has been shown that the resistance value is made variable by switching according to, and the gas concentration is detected accurately.

JP-A-2015-141170 Japanese Patent No. 5805225 Japanese Patent No. 3487159

All of such Patent Documents 1-3 are techniques for changing the current detection resistance with a switch or the like to change the resistance value according to the magnitude of the detected current. The detection targets of Patent Documents 1-3 are the output current value from the generator, the output current value to the rotary electric machine, and the output current value from the sensor, and the current value equal to or more than a certain threshold or less than or equal to the threshold is set. The current detection resistor is switched when it is detected. Further, the control is not performed so that the current flowing through the current detection resistor becomes constant.

By the way, for example, in a current control type APC circuit (automatic power control circuit) mounted on a radio whose output power can be switched by user operation, the current input to the power amplifier (power amplifier) of the transmitter is used. The output power of the transmitter is controlled to be constant by detecting with a current detection resistor and applying negative feedback with an APC circuit. In such a method of controlling the output power of the power amplifier, when the output power is set to be small, the flowing current is small. Therefore, in order to generate a potential difference sufficient for measurement across the resistor, the value of the current detection resistor. However, if this is done, the power efficiency will deteriorate because the current that flows is large when the output power is increased. On the contrary, if the value of the current detection resistor is reduced in order to improve the power efficiency, it becomes difficult to accurately set a small output power.

The present invention solves the above-mentioned problem, does not switch the current detection resistance according to the detected current value, but sets a predetermined resistance value preset according to the output power setting selected by the user. When the output power setting is high, the value of the current detection resistor is reduced to improve power efficiency, and when the output power setting is low, the value of the current detection resistor is used for accurate output power adjustment. It is an object of the present invention to provide a current detection resistance switching device for an APC circuit capable of realizing the characteristic of increasing the power consumption.

In the present invention, the output power of the power amplifier is made constant by applying negative feedback based on a current detection resistance whose combined resistance value is variable and a potential difference between both ends of the current detection resistance, which is connected in series with the power supply line of the power amplifier. A control circuit that generates a control signal for the APC circuit and a control signal for switching the combined resistance value of the current detection resistor based on the output power setting of the power amplifier selected by the user. This is a current detection resistance switching device for the APC circuit provided.

Further, in the above, the current detection resistor has a plurality of current detection resistors, one current detection resistor is connected in parallel to the other current detection resistor via a switch, and the output power setting of the power amplifier is high. At this time, when the switch is turned on by the control signal from the control circuit, the current detection resistors are connected in parallel, and when the output power setting of the power amplifier is low, the control signal from the control circuit causes the current detection resistor. It is preferable that the current detection resistor becomes only one current detection resistor when the switch is turned off.

Further, in the above, it is preferable that a comparator is provided in which the potentials at both ends of the current detection resistor are input and the comparison result is output, and the output of the comparator is given to the APC circuit.

Further, in the above, it is preferable that the power amplifier is for the transmission power of the radio.

According to the present invention, when the output power of the power amplifier is large, the flowing current is large, but since the current detection resistor having a small resistance value is used, the power loss in the current detection resistor can be reduced and the power efficiency is improved. Also, when the output power of the power amplifier is small, the flowing current is small, but since a current detection resistor with a large resistance value is used, the potential difference between the current detection resistors can be measured normally, and accurate output power adjustment in the APC circuit can be performed. Is possible.

The circuit diagram of the current detection resistance switching device for the APC circuit which concerns on one Embodiment of this invention. The figure which shows the switch state corresponding to the output power setting in the same current detection resistance switching device.

Hereinafter, the current detection resistance switching device for the APC circuit according to the embodiment of the present invention will be described with reference to the drawings. In FIG. 1, the current detection resistance switching device 1 for the APC circuit (automatic power control circuit) is connected in series with the power supply Vcc line of the power amplifier (power amplifier) 2, and the combined resistance value is variable with the current detection resistance 3. APC circuit 4 that constantly controls the output power of the power amplifier 2 and a control circuit 5 that generates a control signal or the like for the APC circuit 4 are provided. In this example, the power amplifier 2 is for the transmission power of the radio, and the radio can be used regardless of whether the output power setting is high or low.

The APC circuit 4 controls the output power of the power amplifier 2 to be constant by applying negative feedback according to the current value flowing through the current detection resistor 3. The control circuit 5 includes a CPU 51 that outputs various signals, and outputs an output power control signal (D / A) for the APC circuit 4 and a control signal (H / L) for switching the combined resistance value of the current detection resistor 3. Generate. The CPU 51 generates each signal based on the output power setting of the power amplifier 2 selected by the user, that is, the signal from the transmission output switching operation unit 6.

The current detection resistor 3 has a plurality of current detection resistors 31 and 32 in order to make the combined resistance value variable, and one current detection resistor 31 and the other current detection resistor 32 are connected in parallel via a switch 33. Has been done. The current detection resistors 31 and 32 may have the same resistance value, but do not necessarily have the same value. As the switch 33, for example, a semiconductor switch can be used.

Regarding the resistance value of the current detection resistor 3 according to the connection mode of the current detection resistors 31 and 32, when the output power setting of the power amplifier 2 is high, the switch 33 is turned on by the control signal (H) from the CPU 51 of the control circuit 5. By closing), the current detection resistors 31 and 32 are connected in parallel, and the combined resistance value becomes small. On the other hand, when the output power setting of the power amplifier 2 is low, the switch 33 is turned off (opened) by the control signal (L) from the CPU 51 of the control circuit 5, so that the current detection resistor 3 becomes one of the current detection resistors 31. Only, the combined resistance value becomes large.

A comparator 7 for detecting the potential difference between both ends of the current detection resistor 3 is provided between the current detection resistor 3 and the input unit for applying negative feedback of the APC circuit 4. The comparator 7 includes two input ends at which the potentials at both ends of the current detection resistor 3 are input and an output end that outputs a result of comparing the two input values, and gives an output signal to the APC circuit 4. The potentials at both ends of the current detection resistance 3 are one at the power supply Vcc side end of the current detection resistance 3 and the other at the power amplifier 2 side end of the current detection resistance 3.

In the current detection resistance switching device 1 configured as described above, the user selects and operates the transmission output switching operation unit 6 to set the output power of the power amplifier 2 to high or low. The CPU 51 receives the high or low setting signal and outputs a predetermined output power control signal (D / A) to the APC circuit 4. Further, the CPU 51 outputs a signal for turning on (closing) the switch 33 of the current detection resistor 3 when the setting signal is high, and connects the current detection resistors 31 and 32 in parallel. When the low setting signal is set, a signal for turning off (opening) the switch 33 of the current detection resistor 3 is output, and only the current detection resistor 31 is used.

FIG. 2 shows a switch state corresponding to the output power setting in the current detection resistance switching device 1. When the output power setting is large (high), the switch 33 is turned on, and when the output power setting is extremely small (low), the switch 33 is turned off. The output power setting can be set to a single stage or a plurality of stages for each of high and low (for example, although it is shown as high 3 stages and low 1 stage, it may be any number of switching stages such as high 2 stages and low 2 stages). It can be switched. Switching of the switch 33 is achieved by outputting a power control signal from the CPU 51 according to the output set by the transmission output switching operation unit 6.

Apart from this embodiment, if the resistance of the current detection resistor 3 is not switched regardless of the high / low setting, the current flowing through the current detection resistor 3 is large at the time of the high setting signal, and at that time, the current is detected. Even if the resistance value of the resistor 3 is small, a sufficient potential difference is generated, so that the measurement can be performed without any problem. However, when the low setting signal is used, the current flowing through the current detection resistor 3 is small, and if the resistance value of the current detection resistor 3 is small at that time, a sufficient potential difference does not occur at both ends of the resistor, and accurate measurement can be performed. become unable. If the resistance value of the current detection resistor 3 is increased, the loss due to the current detection resistor 3 becomes large when the flowing current becomes large.

On the other hand, in the present embodiment, the combined resistance value of the current detection resistors 3 connected in parallel is switched ON / OFF of the switch 33 according to the output power setting of the power amplifier 2 (radio) selected by the user. Switch between large and small depending on. As a result, when the flowing current is large (output power is large), the current detection resistor 3 with a small resistance value is used, and when the flowing current is small (output power is small), the current detection resistance 3 with a large resistance value is used. As a result, the power loss in the current detection resistor 3 can be reduced, and the potential difference between the current detection resistors can be normally measured even with a small current.

The present invention is not limited to the configuration of the above embodiment, and various modifications are possible. For example, in the above embodiment, only two resistors in a parallel relationship are shown as the current detection resistor 3, but for example, three resistors in a parallel relationship may be switched.

1 Current detection resistance switching device 2 Power amplifier (power amplifier)
3 Current detection resistor 31, 32 Current detection resistor 33 Switch 4 APC circuit 5 Control circuit 51 CPU
6 Transmission output switching operation unit 7 Comparator Vcc power supply

Claims (4)

A current detection resistor that is connected in series with the power line of the power amplifier and has a variable combined resistance value.
An APC circuit that controls the output power of the power amplifier to be constant by applying negative feedback based on the potential difference between both ends of the current detection resistor.
A control circuit that generates a control signal for the APC circuit and a control signal for switching the combined resistance value of the current detection resistor based on the output power setting of the power amplifier selected by the user.
A current detection resistor switching device for an APC circuit, which is characterized by being equipped with. The current detection resistor has a plurality of current detection resistors, and one current detection resistor and the other current detection resistor are connected in parallel via a switch.
When the output power setting of the power amplifier is high, the current detection resistors are connected in parallel by turning on the switch by the control signal from the control circuit, and when the output power setting of the power amplifier is low, The current detection resistance switching device for an APC circuit according to claim 1, wherein the current detection resistance becomes only one current detection resistance when the switch is turned off by a control signal from the control circuit. The APC circuit according to claim 1 or 2, further comprising a comparator that receives potentials at both ends of the current detection resistor as inputs and outputs the comparison result, and supplies the output of the comparator to the APC circuit. Current detection resistance switching device. The current detection resistance switching device for an APC circuit according to any one of claims 1 to 3, wherein the power amplifier is used for transmission power of a radio.

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