JP7332852B2 - Current detection resistor switching device for APC circuit - Google Patents

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 current by providing a current detection resistor in the circuit to detect the current flowing through the load, etc., and measuring the potential difference between both ends of the resistor, the current detection resistor is controlled based on the detected current. It is known to do (for example, see Patent Documents 1, 2, and 3).

Patent Document 1 discloses first and second resistors connected in series for detecting the current flowing through the load, switches connected in parallel to these resistors, and detecting the current flowing through these resistors. A current sensing circuit is shown that switches a resistor for sensing by switching on and off exclusively depending on the magnitude of the current being sensed.

In Patent Document 2, in an inverter circuit connected to a rotating electric machine, by switching a group of switching elements connected in parallel according to the detected current, the current is detected by one current detection resistor at the time of a small current, and the current detection accuracy is improved. is increased, and when the current is large, it is divided into a plurality of current detection resistors to suppress heat generation per switching element.

Patent Document 3 discloses a gas concentration detection device using a gas concentration sensor that outputs a current signal corresponding to the gas concentration. It is shown that the resistance value can be varied by switching in accordance with , and the gas concentration can be detected with high accuracy.

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

All of these patent documents 1 to 3 are techniques for changing the resistance value by switching the current detection resistor with a switch or the like according to the magnitude of the current to be detected. The objects to be detected in Patent Documents 1 to 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. The current detection resistor is switched when detected. In addition, 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) installed in a radio device that can switch the output power by user operation, the current input to the power amplifier of the transmitter is 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 for controlling the output power of a power amplifier, when the output power is set low, the current flowing is small. is required to be larger than a certain value, but if the output power is increased, the current flowing is large, resulting in poor power efficiency. Conversely, if the value of the current detection resistor is made small in order to improve power efficiency, it becomes difficult to accurately set small output power.

The present invention solves the above problem by not switching the current sensing resistor according to the sensed current value, but by switching the current sensing resistor to a preset predetermined resistance value according to the output power setting selected by the user. i.e., when the output power setting is high, the value of the current sense resistor is decreased for better power efficiency, and when the output power setting is low, the value of the current sense resistor is decreased for accurate output power regulation It is an object of the present invention to provide a current detection resistor switching device for an APC circuit that can realize the characteristic of increasing

The present invention includes a current detection resistor connected in series to a power supply line of a power amplifier and having a variable combined resistance value, and a negative feedback based on the potential difference between both ends of the current detection resistor to keep the output power of the power amplifier constant. an APC circuit to be controlled; and 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 resistors based on the output power setting of the power amplifier selected by the user. , wherein the current detection resistor has a plurality of current detection resistors, one current detection resistor is connected in parallel with the other current detection resistor via a switch, and the output power setting of the power amplifier is high. When the switch is turned on by the control signal from the control circuit, the current detection resistors are connected in parallel, thereby reducing the value of the current detection resistors and setting the output power of the power amplifier to low. When the switch is turned off by the control signal from the control circuit, the current detection resistor becomes only one of the current detection resistors, thereby increasing the value of the current detection resistor. It is a switching device.

Further, in the above, it is preferable that a comparator is provided for receiving the potentials across the current detection resistor as inputs and outputting the result of the comparison, and the output of the comparator is provided to the APC circuit.

Moreover, in the above, it is preferable that the power amplifier is for transmission power of a wireless device.

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

1 is a circuit diagram of a current sensing resistor switching device for an APC circuit according to one embodiment of the present invention; FIG. FIG. 4 is a diagram showing switch states corresponding to output power settings in the same current detection resistor switching device;

A current detection resistor switching device for an APC circuit according to an embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, a current detection resistor switching device 1 for an APC circuit (automatic power control circuit) is connected in series to a power source Vcc line of a power amplifier 2, and a current detection resistor 3 with a variable combined resistance value. , an APC circuit 4 for controlling the output power of the power amplifier 2 to be constant, and a control circuit 5 for generating a control signal and the like for the APC circuit 4 . Power amplifier 2, in this example, is for the transmit power of the radio, which can be used with either a high or low output power setting.

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) to 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, based on the signal from the transmission output switching operation section 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. One current detection resistor 31 is connected in parallel with the other current detection resistor 32 via a switch 33 It is The current detection resistors 31 and 32 may have the same resistance value, but they do not necessarily have the same value. A semiconductor switch, for example, can be used as the switch 33 .

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 control signal (H) from the CPU 51 of the control circuit 5 turns the switch 33 ON ( 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 only, and the combined resistance value becomes large.

A comparator 7 for detecting a potential difference across the current detection resistor 3 is provided between the current detection resistor 3 and the input section for applying negative feedback of the APC circuit 4 . The comparator 7 has two input terminals to which potentials across the current detection resistor 3 are inputted and an output terminal for outputting the result of comparing these two input values, and gives an output signal to the APC circuit 4 . One of the potentials across the current detection resistor 3 is the potential at the end of the current detection resistor 3 on the power supply Vcc side, and the other is the potential at the end of the current detection resistor 3 on the power amplifier 2 side.

In the current detection resistance switching device 1 configured as described above, the user selects and operates the transmission output switching operation section 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 . When the set signal is high, the CPU 51 outputs a signal to turn ON (close) the switch 33 of the current detection resistor 3 to connect the current detection resistors 31 and 32 in parallel. When the setting signal is low, a signal for turning off (opening) the switch 33 of the current detection resistor 3 is output, leaving only the current detection resistor 31 .

FIG. 2 shows switch states corresponding to output power settings in the current detection resistor switching device 1 . When the output power setting is high (high), the switch 33 is ON, and when the output power setting is minimal (low), the switch 33 is OFF. The output power setting can be set in single or multiple stages for each of high and low (for example, although shown as 3 high stages and 1 low stage, the number of switching stages may be arbitrary, such as 2 high stages and 2 low stages). 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 section 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 when the setting signal is high. Since a sufficient potential difference is generated even if the resistance value of the resistor 3 is small, the measurement can be performed without any problem. However, when the setting signal is low, the current flowing through the current detection resistor 3 is small. At that time, if the resistance value of the current detection resistor 3 is small, a sufficient potential difference is not generated across the resistor, making accurate measurement impossible. become unable. If the resistance value of the current detection resistor 3 is increased, the loss due to the current detection resistor 3 increases when the flowing current increases.

On the other hand, in this embodiment, the switch 33 switches ON/OFF the combined resistance value of the current detection resistors 3 connected in parallel according to the output power setting of the power amplifier 2 (radio device) selected by the user. to switch between large and small. 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 resistor 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-described embodiment, only two resistors in parallel relation are shown as the current detection resistor 3, but for example, three resistors in parallel relation may be switched.

1 current detection resistor switching device 2 power amplifier (power amplifier)
3 current detection resistors 31, 32 current detection resistor 33 switch 4 APC circuit 5 control circuit 51 CPU
6 Transmission output switching operation section 7 Comparator Vcc power supply

Claims (3)

a current detection resistor connected in series to the power supply line of the power amplifier and having 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 resistors, based on the output power setting of the power amplifier selected by the user ;
The current detection resistor has a plurality of current detection resistors, and one current detection resistor is connected in parallel to the other current detection resistor via a switch,
When the output power setting of the power amplifier is high, the switch is turned on by a control signal from the control circuit to connect the current detection resistors in parallel, thereby reducing the value of the current detection resistors,
When the output power setting of the power amplifier is low, the switch is turned off by the control signal from the control circuit, and the current detection resistor becomes only one current detection resistor, thereby changing the value of the current detection resistor. A current detection resistor switching device for an APC circuit characterized by being enlarged . 2. A current detection resistor for an APC circuit according to claim 1, further comprising a comparator for receiving potentials across said current detection resistor as inputs and outputting a comparison result thereof, and providing an output of said comparator to said APC circuit. switching device. 3. A current detection resistor switching device for an APC circuit according to claim 1 , wherein said power amplifier is for transmission power of a wireless device.

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