JP2011228774A - Power control device and power control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive wireless transmission apparatus having a small area and low power consumption and capable of preventing a gain, a distortion characteristic or current consumption from being changed at a rear stage of a power amplifier depending on a load condition of an antenna, even if a load stabilizer such as an isolator is removed.SOLUTION: An antenna load obtained from a power amplifier 100 is specified by prestoring a load-dependent characteristic of the power amplifier 100 in a memory 70 based on a detected transmission power level and a detected current value of the power amplifier 100. Based on a result of the above-described determination, a load adjustment of the power amplifier 100 is performed by a variable load unit 40 and a power source voltage adjustment is performed by a DC/DC converter 90, respectively.

Description

  The present invention relates to a load control circuit for a power amplifier and a power control method for the power amplifier, which can be used in a wireless transmission device to achieve low cost, small area, and low power consumption.

  The gain, distortion characteristics, and current consumption of the power amplifier used in the wireless transmission device vary depending on the load impedance state of the output. In particular, when used in a mobile communication terminal such as a mobile phone, the mobile communication terminal may be handled in various forms, and the load impedance variation due to antenna load variation is large (about VSWR = 3 varies). To do). For example, when a device is used close to the human body or used on a metal desk during a call, the antenna load fluctuates due to the capacitive coupling of the antenna of the wireless transmission device with the human body or metal plate, and the effect However, it also appears in various characteristics of the power amplifier that amplifies the transmission output. For this reason, devices that stabilize load impedance, such as isolators, are used in mobile communication terminals. However, since an isolator has a large circuit scale, it is not desirable to use it in a mobile communication terminal that requires portability. Therefore, a technique for suppressing the influence of the load variation of the antenna without using an isolator has been proposed.

  In Patent Document 1, a variable load that can be controlled is used instead of the above-described isolator, and the variable load is controlled on the basis of output power or current consumption. A technique for stabilizing the above is disclosed.

  Japanese Patent Laid-Open No. 2004-228561 detects the bias voltage and current consumption of the power amplifier and calculates the power consumption, thereby changing the bias voltage and correcting the deterioration of the distortion characteristics, thereby reducing the isolator. A technique is disclosed in which the distortion characteristics of a power amplifier are always optimized.

JP 2000-295055 A International Publication No. 2008/111196

  In the conventional configuration, a characteristic depending on the load variation of the power amplifier (hereinafter referred to as a load variation dependent characteristic) is absorbed by control of either a variable load or a bias voltage change. Here, the load dependent characteristics include the gain, distortion characteristics, and current consumption as described above. However, the antenna load assumed in mobile communication terminals such as mobile phones fluctuates extremely violently. Therefore, when an antenna load change occurs, it is difficult to sufficiently suppress the efficiency change and distortion change of the power amplifier only with either the variable load or the bias voltage change.

  In order to solve the conventional problems, a power control apparatus according to the present invention includes a power amplifier that amplifies power, a variable load unit that can change a load of the power amplifier, and input power and output power to the power amplifier, The gain calculation unit for calculating the gain of the power amplifier, the current specifying unit for specifying the current consumed by the power amplifier, the gain calculated by the gain calculating unit and the current specified by the current specifying unit By determining the load and adjusting the load of the variable load unit, the load setting unit that brings the load characteristic of the power amplifier closer to the load characteristic of the reference load, and after adjustment by the load setting unit, the load characteristic of the power amplifier and the reference load If the difference from the load characteristics is larger than the specified value, adjust the power amplifier power supply voltage to adjust the power amplifier load characteristics after adjusting the power supply voltage and the reference negative before adjusting the power supply voltage. The difference between the characteristic and a power supply voltage setting unit suppressed below a predetermined value.

  According to this configuration, the power control device according to the present invention brings the load of the power amplifier closer to the reference load and then adjusts the power supply voltage to further bring the load of the power amplifier closer to the reference load. Therefore, it is possible to absorb the characteristic fluctuation of the power amplifier with high accuracy without using an isolator. In addition, since the power supply voltage is adjusted after adjusting the variable load, the adjustment range of the power supply voltage can be suppressed, and the characteristic fluctuation of the power amplifier can be absorbed without increasing the withstand voltage characteristic of the power control device.

Block diagram of load fluctuation detection and power control circuit in this embodiment The figure which showed the distortion characteristic in this Embodiment on the Smith chart The figure which shows the graph which shows the power supply voltage dependence characteristic in this Embodiment The figure which shows the example of the load dependence table in this Embodiment The figure which showed the characteristic of gain and current in this embodiment on the Smith chart Flowchart for explaining operation of load variation detection and power control circuit in the present embodiment

  Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment)
FIG. 1 is a block diagram showing a schematic configuration of a load control circuit and a power control circuit according to an embodiment of the present invention. The load control circuit and the power control circuit of the present embodiment include a directional coupler 10 for detecting input power, a directional coupler 20 for detecting output power, a detection circuit 30 for input power, and a detection circuit 50 for output power. , A variable load circuit 40 of the power amplifier, a control unit 60 for specifying the load from the input / output power and the detected current, a memory 70 for storing the characteristics of the power amplifier, a step-up / step-down DC / DC converter 90, current consumption And a detection unit 80.

  Input power to the power amplifier 100 is detected by the directional coupler 10 and converted into a voltage by the detection circuit 30. The voltage-converted power is input to the control unit 60 that identifies the load from the input / output power and the detected current, and is A / D converted. The output power from the power amplifier 100 is detected by the directional coupler 20 and converted into a voltage by the detection circuit 50. Then, the voltage-converted power is input to the control unit 60 and A / D converted. In the gain calculation unit 61, the control unit 60 specifies the power gain of the power amplifier 100 (hereinafter also simply referred to as gain) from these input power and output power.

  The consumption current detector 80 detects the current consumed by the power amplifier 100. Specifically, the current value is specified by digitally converting the voltage value detected by the consumption current detection unit 80 in the consumption current conversion unit 62 in the control unit 60 and then performing V / I conversion. The

Next, the memory 70 that stores the characteristics of the power amplifier will be described. As shown in FIGS. 2 and 5, the power amplifier 100 has characteristics in which current, gain, and distortion vary depending on the output load. This load variation dependency characteristic is stored in a memory as a characteristic for each impedance as shown in FIG. In the present embodiment, as shown in FIG. 4, this characteristic is stored in the form of a table (hereinafter referred to as a load dependence table). Here, I _** , G _** , and A _** in Figure 4 (** indicates each number in the table) are the current, gain, and distortion for each impedance, and are dependent on the power supply voltage. Is saved. The characteristic for each impedance stored in the memory can be easily measured by automatic measurement as a single characteristic of the power amplifier. Further, R _** and X _** in FIG. 4 represent the real part and the imaginary part of the impedance.

The load specifying unit 63 uses the power gain detection unit, the current consumption detection unit, and the memory 70 that stores the characteristics of the power amplifier, and uses the load of the power amplifier 100 corresponding to the current current consumption and power. Is identified. Hereinafter, a specific method for specifying the load will be described. It is assumed that the current value detected by the current consumption detector (80 and 62) is 300 mA. Further, it is assumed that the power gain detected by the power gain detection units (10, 20, 30 and 50, 61) is 27 dB. Using this current value and gain value, the cell closest to the pair of I _** and G _** of 300 mA and 27 dB is searched from the load dependence characteristic table shown in FIG. And the real part R and the imaginary part X of the impedance which are the load corresponding to the current consumption current and electric power are specified by confirming the value of the R-axis and the X-axis corresponding to the found cell.

Load adjustment is performed using the specified load and the reference load stored in advance. Here, the reference load is a load used for characteristic inspection in an inspection in a mass production process. In this embodiment, when a 50Ω load by a measuring instrument or the like is connected, a load set in advance so that the current and distortion are optimal is used as the reference load. Assume that the reference load is the load A in FIG. 2, and the load specified by the load specifying unit 63 is the load B. If the impedance of the load A is R1 + jX1, and the impedance of the load B is R2 + jX2, the variable load circuit 40 of the power amplifier is operated so that R1 approaches R2 and X1 approaches X2. More specifically, for example, when the variable load circuit is configured by a variable-capacitor, the capacitive load is varied and adjusted to become the load C. At this time, how much the phase changes in the variable load circuit is stored in the memory in advance. In FIG. 2, an arrow passing from the load B to the load C indicates a load change when the capacitive load is changed by the variable load circuit 40. That is, when only the capacitive load is changed, the load cannot move from the line of the arrow. Here, in the present embodiment, the load C closest to the reference load A is selected from the fluctuating loads. Note that the load C is selected by the load specifying unit 63 searching for a cell in which I _** , G _** , and A _** are closest to the reference load from the load dependence characteristic table. As a result, the real part R3 and the imaginary part X3 of the impedance corresponding to this cell are obtained. Then, by operating the variable load circuit 40, the real part of the impedance of the power amplifier is set to R3 and the imaginary part is set to X3, thereby setting the load of the power amplifier to a load close to the reference load A (load C). be able to.

  However, as shown in FIG. 2, even when the variable load is adjusted to the load C, the distortion characteristic is −36 dBc. This does not reach the reference load of −42 dBc. For this reason, in this embodiment, the step-up / step-down DC / DC converter 9 changes the power supply voltage of the power amplifier 2 to bring the distortion characteristic closer to the characteristic of the reference load (reference state). FIG. 3 is a graph showing characteristics (power supply voltage dependency characteristics) between each power supply voltage and each load. As can be seen from FIG. 3, by increasing the power supply voltage, the distortion of the load C can be brought close to the distortion of the load A when the power supply voltage is low. In FIG. 3, the desired (reference state) distortion characteristic is obtained by increasing the power supply voltage from 3.3 V in the initial setting state to 4.0 V in a state adjusted to the load C by the variable load circuit 40 of the power amplifier. Secured. The setting unit 64 determines how much the power supply voltage should be increased, and the step-up / step-down DC / DC converter 90 performs the process of increasing the power supply voltage. Here, the information of the graph shown in FIG. 3 can be obtained in advance as a single characteristic of the power amplifier, and is calculated from the numerical value for each power supply voltage in the load dependence table shown in FIG. It is possible.

  When the distortion characteristic of the load C is sufficiently close to the load A, a result that is sufficiently close to the reference state may be obtained only by adjusting the load by the variable load circuit 40. In such a case, the power supply voltage is not adjusted, and the current state is maintained until the next load adjustment timing.

  FIG. 6 is a flowchart showing this series of operations. Hereinafter, FIG. 6 will be described.

  Load adjustment processing is started at regular time intervals (step S100). Then, the directional coupler 10 and the directional coupler 20 detect the input power and the output power of the power amplifier, respectively, the detector 30 and the detector 50 convert the input power and the output power, respectively, and the control unit 60 A power gain is calculated from the voltage-converted input power and the voltage-converted output power (S101). Further, the consumption current detector 80 detects the consumption current of the power amplifier (S102). Note that either step S101 or step S102 may be performed first or in parallel.

  Subsequently, the load specifying unit 63 in the control unit 60 searches the load dependence table stored in the memory 70 for a cell corresponding to the power gain obtained in step S101 and the current consumption obtained in step S102. Then, the load of the power amplifier is specified from the found cell (S103).

  Then, the setting unit 64 in the control unit 60 operates the variable load circuit 40 to bring the load of the power amplifier closer to the reference load (load A) (S104). That is, the load specifying unit 63 specifies the load C having the characteristic closest to the reference load A based on the load characteristic table, and the setting unit 64 operates the variable load circuit 40 to load the load of the power amplification unit. Set to C.

  Subsequently, the control unit 60 evaluates whether the load C has characteristics sufficiently close to the reference load A (S105). This evaluation is performed, for example, by determining whether or not the difference between the gain and distortion characteristics is within a predetermined range between the load C and the reference load A. That is, the control unit 60 determines that the desired characteristic is satisfied if the difference is within a predetermined range, and otherwise determines that the desired characteristic is not satisfied.

  If the desired characteristics are not satisfied (S106), the power supply voltage is adjusted. On the other hand, if the desired characteristics are satisfied (S107), the current state is maintained until the next load adjustment timing.

  When adjusting the power supply voltage (S108), the step-up / step-down DC / DC converter 90 increases the power supply voltage in accordance with an instruction from the setting unit 64.

  When the power supply voltage is increased, the increased power supply voltage is recorded in the memory 70, and the next load adjustment timing is awaited (S109).

  The reason why load adjustment is repeatedly performed after S107 and S109 is that load fluctuations are constantly occurring. That is, in the present embodiment, the above-described process is repeated at predetermined time intervals.

  In the above embodiment, the current, gain, and distortion for each impedance are stored in the form of a load characteristic table. However, the present invention is not limited to this. Any other data structure may be used as long as it can store and retrieve current, gain, and distortion for each impedance.

  When the conventional method is used to improve the characteristic fluctuation at the time of load fluctuation of the power amplifier as described above, Patent Document 1 is a characteristic improvement technique using a variable load and improves only to the state of the load C. do not do. In Patent Document 2, the power supply voltage is increased from the load B in FIG. 3 to ensure the characteristics. However, it is necessary to increase the power supply voltage to about 4.3 V, which may cause a problem in the withstand voltage characteristics of the power amplifier 2. There is sex. As a method of avoiding this, a method of gradual change in the load dependent characteristics of the power amplifiers in FIGS. 2 and 5 can be considered, but a reduction in efficiency at the reference load of the power amplifier occurs. Further, in the simple combination of the techniques of Patent Document 1 and Patent Document 2, it is necessary to perform load detection in each of the variable load control and the bias voltage change control, and one correction takes time. .

  Therefore, a power control apparatus according to an aspect of the present invention includes a power amplifier that amplifies power, a variable load unit that can change a load of the power amplifier, and an input power and an output power of the power amplifier. The gain calculation unit for calculating the gain, the current specifying unit for specifying the current consumed by the power amplifier, the gain calculated by the gain calculating unit and the current specified by the current specifying unit are used to determine the load of the power amplifier. The load setting unit that adjusts the load of the variable load unit to bring the load characteristic of the power amplifier closer to the load characteristic of the reference load, and after the adjustment by the load setting unit, the load characteristic of the power amplifier and the load characteristic of the reference load If the difference is larger than the predetermined value, the power amplifier power supply voltage is adjusted, the power amplifier load characteristics after the power supply voltage adjustment, and the reference load characteristics before the power supply voltage adjustment And a power supply voltage setting unit to reduce a difference below a predetermined value.

  That is, the power control apparatus according to the present invention brings the load of the power amplifier closer to the reference load by adjusting the variable load, and further brings the load closer to the reference load by adjusting the power supply voltage. Therefore, it is possible to absorb the characteristic fluctuation of the power amplifier with high accuracy without using an isolator. In addition, since the power supply voltage is adjusted after adjusting the variable load, the adjustment range of the power supply voltage can be suppressed, and the characteristic fluctuation of the power amplifier can be absorbed without increasing the withstand voltage characteristic of the power control device.

  Further, in the power control device according to one aspect of the present invention, when the power supply voltage setting unit is adjusted by the load setting unit, the difference between the load characteristic of the power amplifier and the load characteristic of the reference load falls within a predetermined value or less. Do not adjust the power supply voltage.

  As a result, the power adjustment process can be omitted, and the control can be speeded up.

  In the power control apparatus according to one aspect of the present invention, the load setting unit stores in advance load characteristic information that is information that associates the gain and current of the power amplifier for each load of the power amplifier, and calculates A load corresponding to the gain calculated by the unit and the current detected by the detection unit is set as a load of the power amplifier.

  Thereby, a load close to the load characteristic of the reference load can be examined at high speed.

  In the power control apparatus according to one aspect of the present invention, the load characteristic information is information in which the gain, current, and distortion of the power amplifier are associated with each load of the power amplifier, and the load setting unit includes the load characteristic information By specifying the load corresponding to the gain and distortion closest to the gain and distortion of the reference load, and adjusting the load of the variable load unit to match the load of the power amplifier with the specified load, the load characteristics of the power amplifier To the load characteristics of the reference load.

  Thereby, load adjustment can be performed at high speed. That is, since the load characteristic information is stored in advance, it is not necessary to check a new load characteristic after adjusting the variable load, and the number of load detection processes can be reduced.

  In the power control device according to one embodiment of the present invention, the power amplifier amplifies the transmission output of the antenna.

  Thereby, the influence of the load fluctuation | variation of an antenna can be suppressed with high precision by the process of the power control apparatus mentioned above.

  The present invention can be applied to all devices having a power amplifier. In particular, it is useful in a device including a wireless transmission device such as a mobile communication terminal in which the load fluctuation of the power amplifier is severe.

DESCRIPTION OF SYMBOLS 10 Directional coupler for input power detection 20 Directional coupler for output power detection 30 Input power detection circuit 40 Variable load circuit of power amplifier 50 Output power detection circuit 60 Specify load from input / output power and detection current Control unit 61 Gain calculation unit 62 Current consumption value conversion unit 63 Load specifying unit 64 Variable load and voltage setting unit 70 Memory for storing power amplifier characteristics 80 Current consumption detection unit 90 Buck-boost DC / DC converter 100 Power Amplifier 110 Antenna duplexer 120 Antenna

Claims (6)

A power amplifier for amplifying power;
A variable load unit capable of changing a load of the power amplifier;
A gain calculation unit for calculating a gain of the power amplifier from input power and output power to the power amplifier;
A current specifying unit for specifying the current consumed by the power amplifier;
The load of the power amplifier is obtained from the gain calculated by the gain calculating unit and the current specified by the current specifying unit, and the load of the variable load unit is adjusted to obtain the load characteristic of the power amplifier as a reference load. A load setting unit that approaches the load characteristics of
After the adjustment by the load setting unit, when the difference between the load characteristic of the power amplifier and the load characteristic of the reference load is larger than a predetermined value, the power supply voltage of the power amplifier is adjusted to adjust the power supply voltage after the adjustment. A power control apparatus comprising: a power supply voltage setting unit configured to suppress a difference between a load characteristic of the power amplifier and a characteristic of the reference load before adjustment of the power supply voltage to the predetermined value or less. The power supply voltage setting unit does not adjust the power supply voltage when a difference between a load characteristic of the power amplifier and a load characteristic of the reference load falls below a predetermined value as a result of adjustment by the load setting unit. Item 2. The power control apparatus according to Item 1. The load setting unit stores in advance load characteristic information, which is information in which the gain and current of the power amplifier are associated with each load of the power amplifier, and the gain calculated by the calculation unit and the detection unit The power control apparatus according to claim 1, wherein a load corresponding to the current detected by the power amplifier is a load of the power amplifier. The load characteristic information is information that associates the gain, current, and distortion of the power amplifier for each load of the power amplifier,
The load setting unit identifies a load corresponding to the gain and distortion closest to the gain and distortion of the reference load from the load characteristic information, and adjusts the load of the power amplifier to the identified load. The power control device according to claim 3, wherein the load characteristic of the power amplifier is brought close to the load characteristic of the reference load by adjusting a load of the unit. The power control apparatus according to claim 1, wherein the power amplifier amplifies a transmission output of an antenna. A power control method by a power control device comprising a power amplifier for amplifying power and a variable load unit capable of changing a load of the power amplifier,
A gain calculating step of calculating a gain of the power amplifier from input power and output power to the power amplifier;
A current identifying step for identifying a current consumed by the power amplifier;
By obtaining the load of the power amplifier from the gain calculated in the gain calculating step and the current specified in the current specifying step, and adjusting the load of the variable load unit, the load characteristic of the power amplifier is obtained. A setting step to bring it closer to the load characteristics of the reference load;
After the adjustment by the setting step, when the difference between the load characteristic of the power amplifier and the load characteristic of the reference load is larger than a predetermined value, the power voltage of the power amplifier is adjusted to adjust the power voltage after the adjustment. A power control method comprising: a power supply voltage setting step of suppressing a difference between a load characteristic of a power amplifier and a characteristic of the reference load before adjustment of the power supply voltage to be equal to or less than the predetermined value.

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