JP2002009641A - Device protection unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of the conventional device protection units that they require increase in input power from prescribed device and increase in the output power, in order to obtain a desired output from a prescribed device, while an isolator is used. SOLUTION: In the case of outputting a prescribed signal output on the basis of an output of a prescribed device, load fluctuations at a signal output side are detected to adjust an impedance connected just after the device, in response to load fluctuations. Thus, this invention provides a device protection unit that can prevent breakdown of the device, while realizing high reliability and making service life long, without the need for attempt to bring high efficiency for the device and causing the increased power consumption.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device protection device, and more particularly to a device protection device suitable for use in preventing destruction of a power amplifier.

[0002]

2. Description of the Related Art In a device for obtaining a high output, such as a power amplifier of a transmitter, the characteristics of the device greatly change due to a change in a load impedance connected to the output. In particular, when the load impedance increases, the level of the reflected wave returning to the device increases, which causes an increase in current consumption, a deterioration in power output efficiency, and the like. Depending on the level, the device may be destroyed.

In order to stabilize the output load of a device, a technique for incorporating a load matching device such as an isolator is conventionally known. This isolator is an element that transmits electromagnetic waves in a predetermined direction and absorbs electromagnetic waves in the opposite direction.By interposing this element between the power amplifier and the transmission output, it is possible to block reflected waves. it can. On the other hand, in the technique disclosed in JP-A-6-252785, when obtaining an output from an antenna based on a power amplifier output, the presence or absence of the antenna is detected.
When the antenna is not connected, the power of the power amplifier itself is switched to protect against load fluctuation.

[0004]

The above-mentioned conventional device protection apparatus has the following problems. In the former prior art, since the isolator itself has an attenuation, in order to obtain a desired radiated power at the antenna output, it is necessary to obtain an output in consideration of the attenuation of the isolator by a device. Here, since it is generally not easy to increase the efficiency of the device, it is necessary to increase the input power to the device and increase the output power in order to obtain the desired radiated power, and as a result, the current consumption increases. It will be connected.

On the other hand, in the latter conventional technique, since the power supply of the power amplifier is changed instantaneously, it is not desirable in terms of reliability and life of the power amplifier itself.

[0006] The present invention has been made in view of the above problems, and does not require high efficiency of the device.
It is an object of the present invention to provide a device protection device that can prevent device destruction while achieving high reliability and long life without increasing power consumption.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, when a predetermined signal is output based on an output of a predetermined device, the device is destroyed by a load change on the output side. A device protection device for preventing the above, wherein the device output is an input, a variable impedance means capable of adjusting an input impedance to the input, and a signal output means for outputting the predetermined signal based on an output of the variable impedance means A load fluctuation detecting means for detecting a load fluctuation in the signal output means; and an impedance control means for controlling the variable impedance means based on a detection result of the load fluctuation detecting means to adjust the input impedance. There is a configuration.

That is, the device protection apparatus according to the present invention, when outputting a predetermined signal based on the output of a predetermined device, does not work to improve the efficiency of the device and increases the power consumption. Without the device being destroyed. Therefore, the variable impedance means receives the device output as an input, and can adjust the input impedance with respect to the input, and the signal output means performs the predetermined signal output based on the output of the variable impedance means. .

Further, when a predetermined signal is output by the signal output means, the load fluctuation detecting means detects a load fluctuation in the signal output means. The impedance control means controls the variable impedance means based on the detection result of the load fluctuation detection means to adjust the input impedance. Therefore, even when the load is rapidly increased in the signal output means and the output reflection is increased, the impedance at the subsequent stage of the device is adjusted, and the device can be prevented from being broken.

According to a second aspect of the present invention, in the device protection device according to the first aspect, the predetermined device is a power amplifier. In other words, when the power required for transmitting output in the transmitter is obtained from the output of the power amplifier, the load at the output end easily fluctuates greatly due to the expansion / contraction state, the proximity of metal or the like, or the attachment / detachment of the antenna. I do. Therefore, it is preferable to apply the present invention to such a power amplifier because it is possible to prevent destruction without changing the characteristics and power consumption of the power amplifier.

Further, according to a third aspect of the present invention, in the device protection device according to the first or second aspect, the variable impedance means is a phase adjuster. That is, the phase adjuster has a function of changing the electrical length according to a signal from the outside, thereby changing the input impedance. Here, the impedance adjustment by the phase adjuster does not require an operation to instantaneously turn on / off the power supply of the device, and thus is advantageous in terms of reliability and lifetime of the device itself as compared with the above-described conventional technology. .

Further, according to a fourth aspect of the present invention, in the device protection device according to any one of the first to third aspects, the signal output means inputs an output of the variable impedance means and receives the input of the input. A first output that outputs main power, a directional coupler including a second output that inputs a reflection of the first output and outputs the reflection input to the load variation detection unit, And an antenna for radiating the output to free space.

That is, the directional coupler is a power splitter that outputs an input from two directions at a certain fixed attenuation rate in accordance with the input level thereof. The state can be easily monitored. Further, by connecting the output of the directional coupler to the antenna, the power of the device can be easily supplied to the antenna serving as the transmission output terminal.

Further, according to a fifth aspect of the present invention, in the device protection apparatus according to any one of the first to fourth aspects, the load fluctuation detecting means inputs the reflection of the signal output means, and It is configured to output detection power proportional to the input power. That is,
Since the reflected power reflects the load fluctuation, outputting the detected power in proportion to the reflected power is equivalent to detecting the load fluctuation and performing output in accordance with the fluctuation.

Further, according to a sixth aspect of the present invention, in the device protection apparatus according to any one of the first to fifth aspects, the impedance control means is provided when the output impedance of the signal output means becomes large. ,
The configuration is such that the input impedance is increased.
That is, when the output impedance of the signal output means increases, the reflected power increases. By increasing the input impedance at this time, unnecessary large power is not supplied to the device.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic block diagram showing a device protection apparatus according to an embodiment of the present invention. This embodiment is an embodiment in which a device protection device is interposed in a transmission system of a wireless device.
Reference numeral 0 denotes an element that amplifies and outputs a predetermined input signal, and supplies signal power for outputting a predetermined signal from the antenna 100.

In the present embodiment, in order to prevent the power amplifier 500 from being destroyed, a device protection device is interposed at the subsequent stage of the power amplifier 500. Here, the device protection device includes a phase adjuster 300 and a directional coupler 2.
00, a detection circuit 400, and a control device 600. The phase adjuster 300 changes the input impedance by changing its electrical length in response to an external input signal. The output of the power amplifier 500 is input to the phase adjuster 300.

The directional coupler 200 is a power splitter that outputs an input from two directions at a certain fixed attenuation rate according to the input level, and a phase adjuster 300.
And the antenna 100 and the detection circuit 400 are connected. The main part of the power input from the phase adjuster 300 is output to the antenna 100, and the reflected power from the antenna 100 is output to the detection circuit 400. In this way, the main part of the power amplified by the power amplifier 500 is normally output to the antenna 100.

The detection circuit 400 is constituted by a circuit such as a detection diode (not shown) to which a DC bias is applied.
This circuit outputs a detection voltage proportional to the input power. As described above, the output of the reflected power in the directional coupler 200 is input, and a detection voltage proportional to the input power is output to the control device 600. The control device 600 outputs a control signal corresponding to the input voltage. The control signal is input to the phase adjuster 300, and the input impedance is adjusted. That is, the output state of the detection circuit 400 is monitored and the input impedance is changed according to the monitored state.

As described above, the device protection apparatus according to the present embodiment forms a feedback loop using the reflected power of the antenna 100. On the other hand, in a circuit using the power amplifier 500, generally, the antenna 1
It is conceivable that feedback control based on the signal power amount in the 00 direction is also performed. The directional coupler 200 is suitable for obtaining the control amount information at that time.

Although the device to be protected is the power amplifier 500 in the present embodiment, it is needless to say that the device is not limited to the power amplifier 500 and the device protection apparatus can be applied to various devices. In the above embodiment, the phase adjuster 300 constitutes the variable impedance means, the directional coupler 200 constitutes the signal output means, the detection circuit 400 constitutes the load fluctuation detecting means, and the control device 600 Constitute the impedance control means.

Hereinafter, the operation of the present device protection apparatus having the above configuration will be described. In FIG. 1, a power amplifier 50
When a predetermined signal is input to 0, the power amplifier 500 amplifies and outputs the signal. The directional coupler 200 receives the power output from the power amplifier 500 via the phase adjuster 300 and outputs the main part to the antenna 100. Antenna 100 radiates a transmission signal to free space based on input power. In the signal output by the antenna 100, if the load of the antenna 100 is ideally matched with the subsequent circuits, no reflected power is generated.

However, the load on the antenna 100 fluctuates easily when the antenna 100 expands or contracts, or when a metal or the like is brought close to the antenna 100, and power is transmitted as a reflected wave from the antenna 100 toward the directional coupler 200. This reflected power is input to the directional coupler 200, and a signal based on the input is input to the detection circuit 400. The detection circuit 400 performs detection output according to the input signal power and inputs the detection output to the control device 600.

When the load of the antenna 100 deviates extremely from the matching and the reflected power input to the directional coupler 200 increases, the detection output also increases accordingly.
At this time, the control device 600 recognizes this, and
00 to increase the load impedance as viewed from the power amplifier 500. Therefore, the output power of the power amplifier 500 itself decreases. Generally, as a process leading to the destruction of a power device, it often happens that the sum of the power supply voltage, the output power amplitude, and the reflected wave power amplitude exceeds a certain threshold value. According to the above operation, the input of the reflected wave to the power amplifier 500 and the output power of the power amplifier 500 itself become small even by the extreme load fluctuation of the antenna 100, and the device itself is prevented from being destroyed due to the extremely increased reflected wave. It becomes possible.

As described above, according to the present invention, the level of the reflected wave generated by the large fluctuation of the impedance due to the expansion / contraction operation of the antenna and the connection / disconnection of the output terminal is relatively reduced. It has the effect of preventing its own efficiency reduction and destruction. Further, since there is no load matching device such as an isolator, the attenuation after the output terminal of the device is reduced, so that even when the same power is obtained at the antenna radiation end, the output power of the device itself can be reduced. In other words, in the above state, if the efficiency of the device does not change, the current consumption of the device can be reduced, that is, the device can operate for a long time. Further, since the control target is the phase adjuster, the power supply of the device is not instantaneously changed unlike the technique disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 6-252785. The service life can be extended.

The antenna 100 is not limited to a pure aerial, but may have a fluctuating load. For example, even if it is an output terminal for extracting a signal from a mobile phone terminal to the outside with a coaxial cable or the like, the cable is connected. Since the change in load due to the absence of this is considered to correspond to the expansion and contraction of the antenna, the application of this patent is possible. Here, the detection circuit 400 assumes an operation of converting power into voltage using a diode, but the circuit configuration is not particularly limited.

FIG. 2 is a block diagram showing a configuration example when the device protection device according to the present invention is applied to an actual circuit. In this example, a part of the transmission block of the wireless device includes an antenna 110, a directional coupler 210, a phase adjuster 310, a detection circuit 410, a control device 610, and a power amplifier 510, as in the above-described embodiment. .
In addition to this configuration, a detection circuit 415 for performing feedback control based on power in the direction of the antenna 110 is provided.
It has. Here, the antenna 110 and the phase adjuster 3
The configuration and operation of the detection circuit 10, the detection circuit 410, and the power amplifier 510 are the same as those in the above embodiment.

On the other hand, the directional coupler 210 outputs the main part of the power input from the phase adjuster 310 to the antenna 110 in the same manner as in the above-described embodiment, and forward-divides a part of the power with a constant attenuation in the forward direction. The output 211 is output to the detection circuit 415. The detection circuit 415, like the detection circuit 410, is configured by a circuit such as a not-shown detection diode with a DC bias and outputs a detection voltage proportional to the input power. This detection circuit 4
Reference numeral 15 inputs the positive branch output 211 of the directional coupler 210 and outputs a detection voltage 213 proportional to the input power to the control device 600.

Further, similarly to the above embodiment, the directional coupler 210 converts the reflected power from the antenna 110 into a backward branch output 212 with a certain amount of attenuation, as a detection circuit 41.
Output for 0. A detection voltage 214 corresponding to the backward branch output 212 is output from the detection circuit 410 and input to the control device 600. The control device 600 outputs a control signal corresponding to the input voltage.
Feedback control of the phase adjuster 300 is performed according to 3,214.

In the above configuration, the power amplifier 500
When a predetermined signal is input to the power amplifier 500, the power amplifier 500 amplifies and outputs the signal. Directional coupler 2
10 receives the power output from the power amplifier 500 via the phase adjuster 300, outputs the main part to the antenna 110, and outputs the forward branch output 211. The positive branch output 211 is input to the detection circuit 415, and the detection voltage 213 is output. As a result, the control device 610 controls the phase adjuster 310 to change the load impedance.

On the other hand, the load of the antenna 110 fluctuates due to the expansion / contraction state of the antenna 110, the proximity of a metal or the like to the vicinity, and the connection / disconnection state of the antenna 110, and a reflected wave is generated. The reflected wave is transmitted to the directional coupler 21.
The detection circuit 410 outputs a detection voltage 214 from the detection circuit 410. As a result, the control device 610 controls the phase adjuster 310 to change the load impedance. With this control, even if the load on the antenna 110 is extremely deviated from the matching and the reflected power input to the directional coupler 210 increases, the load impedance viewed from the power amplifier 510 is appropriately adjusted. Therefore, destruction of the device itself due to an excessive increase in reflected waves can be prevented.

As described above, according to the present invention, when a predetermined signal is output based on the output of a predetermined device, the load fluctuation on the signal output side is detected, and the impedance connected immediately after the device is adjusted according to the load fluctuation. I do. Therefore,
A device protection device that does not need to increase the efficiency of the device, does not cause an increase in power consumption, and can prevent device destruction while realizing high reliability and long life. Can be provided.

[0033]

As described above, according to the present invention, even when the load suddenly increases on the signal output side and the output reflection increases, the impedance at the subsequent stage of the device is adjusted and the device is destroyed. Can be prevented. According to the second aspect of the invention, destruction can be prevented without changing the characteristics and power consumption of the power amplifier. Further, according to the third aspect of the invention, it is possible to increase the reliability of the device itself and extend the life of the device.

Further, according to the invention of claim 4,
The state of input / output power can be easily monitored. Further, according to the invention of claim 5, it is possible to easily detect a load change. Further, according to the invention of claim 6, it is not necessary to supply unnecessary large power to the device.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a device protection apparatus according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a configuration example when the device protection device according to the present invention is applied to an actual circuit.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 antenna 200 directional coupler 300 phase adjuster 400 detection circuit 500 power amplifier 600 controller

Claims (6)

[Claims] 1. A device protection device for preventing a device from being destroyed by a load fluctuation on an output side when a predetermined signal is output based on an output of a predetermined device. Variable impedance means capable of adjusting the input impedance of the variable impedance means; signal output means for outputting the predetermined signal based on the output of the variable impedance means; load variation detection means for detecting a load variation in the signal output means; A device protection device comprising: an impedance control unit that controls the variable impedance unit based on a detection result of the load fluctuation detection unit to adjust the input impedance. 2. The device protection device according to claim 1, wherein the predetermined device is a power amplifier. 3. The device protection device according to claim 1, wherein said variable impedance means is a phase adjuster. 4. The device protection device according to claim 1, wherein the signal output means receives the output of the variable impedance means and outputs the main power of the input. A directional coupler comprising an output, a second output for inputting the reflection of the first output and outputting the reflection input to the load fluctuation detecting means, and an antenna for radiating the first output to free space A device protection device comprising: 5. The device protection apparatus according to claim 1, wherein said load fluctuation detecting means inputs a reflection at a signal output means and detects a signal proportional to the input power. A device protection device for outputting electric power. 6. The device protection device according to claim 1, wherein the impedance control means increases the input impedance when the output impedance of the signal output means increases. A device protection device characterized by the above-mentioned.