Variable resistance device

Abstract

Provided is a variable resistance device that can set a desired resistance value while measuring the resistance value of a variable resistor. Specifically, this variable resistance device 100 comprises: a variable resistor 10 that includes a resistor 11 that has a first terminal t1 and a second terminal t2 and a slider 12 that has a third terminal t3 and is configured such that the position P at which the slider 12 contacts the resistor 11 can be changed; a drive unit 40 that moves and thereby changes the position of the slider 12 as in contact with the the resistor 11; an input-side resistance measurement unit 20 that measures an input-side variable resistance value R1 that is the resistance value between the first terminal t1 and the third terminal t3; and a control unit 30 that, when an output-side variable resistance value R2 that is the resistance value between the second terminal t2 and the third terminal t3 is adjusted to a desired output resistance value, controls the drive unit 40 to change the position at which the slider 12 contacts the resistor 11 on the basis of the input-side variable resistance value R1 measured by the input-side resistance measurement unit 20.

Description

variable resistance device

[0001] The present invention relates to a variable resistance device, and more particularly to a variable resistance device including a control unit that adjusts the resistance value of a variable resistor.

[0002] 2. Description of the Related Art Conventionally, variable resistance devices have been known that include a control unit that adjusts the resistance value of a variable resistor (see, for example, Patent Document 1).

[0003] The above-mentioned Patent Document 1 discloses a configuration in which a damping resistor control unit adjusts the value of a damping resistor to suppress signal noise such as ringing from occurring in an interface signal between an IC in the mobile phone and the memory card when reading a memory card used in a mobile phone, etc. The above-mentioned Patent Document 1 also discloses a configuration in which the damping resistor control unit adjusts the resistance value of the damping resistor to a resistance value stored in a memory unit based on a command to adjust the damping resistor to a predetermined setting value. The above-mentioned Patent Document 1 also discloses a configuration in which the damping resistor control unit adjusts the damping resistor by gradually decreasing the resistance value from the maximum resistance value by a preset value based on a command to adjust the resistance value of the damping resistor to a predetermined setting value.

[0004] Japanese Patent Application Laid-Open No. 2008-41009

[0005] The above-mentioned Patent Document 1 discloses a configuration in which a damping resistor control unit adjusts the resistance value of a damping resistor to a resistance value stored in a memory unit, and to a resistance value gradually decreasing from a maximum value by a set value. Here, the resistance value of a variable resistor is generally determined by the positional relationship between the resistor and the slider. However, the state of the variable resistor may change due to deterioration caused by friction of the slider or changes in contact resistance at the contact position, resulting in a deviation in the resistance value. Therefore, it is conceivable that the resistance value adjusted to the resistance value stored in the memory unit or the resistance value adjusted by gradually decreasing the resistance value from the maximum value by a set value, as in the above-mentioned Patent Document 1, may deviate from the desired resistance value. Therefore, there is a demand for a variable resistor device that can set the resistance value of a variable resistor to a desired resistance value even if the state of the variable resistor changes.

[0006] The present invention has been made to solve the above-mentioned problems, and one object of the present invention is to provide a variable resistor device that can set the resistance value of a variable resistor to a desired resistance value even if the state of the variable resistor changes.

[0007] In order to achieve the above object, a variable resistance device according to one aspect of the present invention comprises a variable resistor including a resistor having a first terminal and a second terminal, and a slider having a third terminal, and configured so that the position at which the slider contacts the resistor can be changed; a drive unit that moves and changes the position of the slider that contacts the resistor; an input-side resistance measuring unit that measures an input-side variable resistance value that is the resistance value between the first terminal and the third terminal; and a control unit that controls the drive unit to change the position at which the slider contacts the resistor based on the input-side variable resistance value measured by the input-side resistance measuring unit when adjusting the output-side variable resistance value that is the resistance value between the second terminal and the third terminal to a desired output resistance value.

[0008] As described above, a variable resistance device according to one aspect of the present invention includes a control unit that controls the drive unit to change the contact position of the wiper with respect to the resistor based on the input variable resistance value measured by the input resistance measurement unit when adjusting the output variable resistance value, which is the resistance value between the second terminal and the third terminal, to a desired output resistance value. This changes the position of the wiper based on the input variable resistance value measured by the input resistance measurement unit, making it possible to adjust the resistance value while measuring the actual value of the input variable resistance. As a result, the resistance value of the variable resistor can be set to a desired resistance value even if the state of the variable resistor changes.

[0009] The variable resistance device according to the above aspect preferably further includes a memory unit that stores variable resistance relationship information indicating the relationship between the input variable resistance value and the output variable resistance value. To adjust the output variable resistance value to a desired output resistance value, the control unit identifies the input resistance value corresponding to the desired output resistance value based on the variable resistance relationship information acquired from the memory unit, and controls the drive unit to change the contact position of the wiper with the resistor to a position where the input resistance value measured by the input resistance measurement unit is equal to the input resistance value. With this configuration, even when adjusting the output variable resistance value of the resistor to a desired output resistance value for suppressing signal noise such as ringing, the contact position of the wiper with the resistor can be moved to an appropriate position based on the measured value of the input variable resistance. As a result, the output variable resistance value can be adjusted to the desired output resistance value based on the measured value of the input variable resistance.

[0010] In the variable resistance device according to the above aspect, preferably, when adjusting the output variable resistance value to the desired output resistance value, the control unit controls the drive unit to change the contact position of the wiper with respect to the resistor based on the input variable resistance value measured by the input resistance measurement unit while the load connected to the second terminal t2 of the resistor is in operation. With this configuration, for example, even if the output variable resistance value temporarily changes due to a displacement of the wiper caused by vibration while the load is in operation, the output resistance value can be adjusted without stopping the operation of the load.

[0011] In this case, preferably, the device further includes a DC interruption circuit connected between the second terminal t2 and a load operated by input of AC power, and the input-side resistance measurement unit is connected to the first terminal t1 of the resistor and the third terminal of the wiper. Here, DC power is generally used for resistance measurement. Therefore, with the above configuration, even when the load is driven by AC power, the DC power used for the input-side resistance measurement unit is interrupted by the DC interruption circuit provided between the second terminal and the load, preventing it from being supplied to the load. As a result, the input-side variable resistance, which is the resistance between the first terminal of the resistor and the third terminal of the wiper, can be measured and adjusted while the load using AC power is operating.

[0012] The variable resistance device having the DC blocking circuit preferably further includes an output resistance measuring unit connected to the second terminal of the resistor and the third terminal of the wiper, for measuring the output variable resistance value. With this configuration, even when it is desired to adjust the output variable resistance value to a desired output resistance value, the output variable resistance value can be adjusted while measuring the output resistance value.

[0013] The variable resistance device with the memory unit preferably further includes an output resistance measurement unit connected to the second terminal of the resistor and the third terminal of the slider and configured to measure the output variable resistance value, the memory unit configured to store a plurality of positions where the slider contacts the resistor and to update and store the stored variable resistance-related information based on measurements of both the input variable resistance value and the output variable resistance value corresponding to each of the plurality of positions. With this configuration, even if the state of the variable resistor changes (deteriorates) due to wear of the slider or the like, the variable resistance-related information after the change in the resistance characteristics of the variable resistor is updated and stored in the memory unit based on the new measurements. As a result, even if the state of the variable resistor changes, the output variable resistance value can be appropriately set based on the input variable resistance value.

[0014] In this case, the memory unit is preferably configured to store measured values ​​of at least one of the input variable resistance value and the output variable resistance value at each of the plurality of positions. This configuration allows an operator to compare the measured values ​​stored in the memory unit with the current measured values. As a result, the operator can easily detect changes in the resistance characteristics of the variable resistor due to wear of the slider, etc.

[0015] In the variable resistance device having the memory unit, the variable resistance relationship information stored in the memory unit preferably includes at least one of a formula for obtaining an output variable resistance value based on an input variable resistance value, a table that associates input variable resistance values ​​with output variable resistance values, and an approximation formula that represents the correlation between the input variable resistance value and the output variable resistance value. With this configuration, the control unit can easily identify the input resistance value that corresponds to the desired output resistance value based on the formula, table, or approximation formula that represents the relationship between the input variable resistance value and the output variable resistance value, which is stored in the memory unit.

[0016] According to the present invention, as described above, it is possible to provide a variable resistor device that can set the resistance value of a variable resistor to a desired resistance value even if the state of the variable resistor changes.

[0017] It is a figure which showed the structure of the variable resistance device by 1st embodiment. It is a figure for demonstrating various resistances of the variable resistance device by 1st embodiment. It is an example of a circuit which incorporates the variable resistance device by 1st embodiment. It is a figure which showed the structure of the variable resistance device by 2nd embodiment.

[0018] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0019] First Embodiment The configuration of a variable resistance device 100 according to a first embodiment will be described with reference to FIG.

[0020] (Configuration of Variable Resistance Device) As shown in FIG. 1, the variable resistance device 100 includes a variable resistor 10, an input resistance measuring unit 20, a control unit 30, a drive unit 40, and a capacitor C1 as a DC blocking circuit.

[0021] The variable resistor 10 includes a resistive element 11 having a first terminal t1 and a second terminal t2, and a wiper 12 having a third terminal t3. The variable resistor 10 is, for example, a linear potentiometer. The resistive element 11 is made of a conductive film material, such as a carbon film, which is resistant to wear due to sliding. The wiper 12 is made of a conductive metal brush, such as a copper alloy, and is arranged to contact the resistive element 11. The wiper 12 also has a shaft (not shown), and the contact position P (see FIG. 2 ) with respect to the resistive element 11 is changed by moving the shaft supported by the drive unit 40. The shaft included in the wiper 12 is made of an insulating material to prevent noise generated by the drive unit 40 from being transmitted to the variable resistor 10.

[0022] Here, the resistance values ​​of the variable resistor 10 will be described in detail using FIG. 2 . The resistance value of the entire resistor 11 is Rz. As described above, the contact position P of the slider 12 relative to the resistor 11 is changed. Note that this contact position P indicates the distance from a reference point, where the end of the movable position of the slider 12 on the side where the drive unit 40 is located is set to 0. In this case, if the resistance value of the first resistor 1 representing the resistance of the portion of the resistor 11 closer to the first terminal t1 than the contact position P is Rx, and the resistance value of the second resistor 2 representing the resistance of the portion of the resistor 11 closer to the second terminal t2 than the contact position P is Ry, then the relationship Rz = Rx + Ry holds. This relationship does not change even if the resistance values ​​Rx of the first resistor 1 and Ry of the second resistor 2 are changed according to the contact position P. The resistance value Rx of the first resistor 1 at the contact position P is expressed as Rx = (P - P1) / (P2 - P1) x Rz, based on the contact position P1 of the wiper 12 where the resistance value Rx of the first resistor 1 is minimum and the contact position P2 of the wiper 12 where the resistance value Rx of the first resistor 1 is maximum. Therefore, the resistance value Rx of the first resistor 1 at the contact position P increases as the contact position P of the wiper 12 with respect to the resistor 11 approaches the second terminal t2.

[0023] The wiper 12 also includes a contact resistance 3 between the resistor 11 and the wiper 12 at the contact position P, and a wiper resistance 4, which is the resistance of the wiper 12 itself. The resistance value of the contact resistance 3 is Rc, and the resistance value of the wiper resistance 4 is Rs. In this first embodiment, the resistance value Rc of the contact resistance 3 does not change depending on the contact position P between the resistor 11 and the wiper 12. Using the above resistance values, the input-side variable resistance R1, which is the resistance value between the first terminal t1 and the third terminal t3, is expressed by the relational expression R1 = Rx + Rc + Rs. Similarly, the output-side variable resistance R2, which is the resistance value between the second terminal t2 and the third terminal t3, is expressed by the relational expression R2 = Ry + Rc + Rs. In this first embodiment, the resistance values ​​Rs and Rc are designed to be negligibly small compared to the resistance values ​​Rx and Ry, and in the initial stage of use of the variable resistance device 100 (when the state of the variable resistor 10 has not changed), the relationships R1 ≒ Rx and R2 ≒ Ry hold.

[0024] 1 is a measuring device for measuring the input variable resistance R1. The input resistance measuring unit 20 includes a comparator 21, a DC current source S, a capacitor C2, and a measuring unit resistor 22 having a resistance value Rm.

[0025] The comparator 21 has an internal impedance that is significantly larger than the input variable resistance R1 and the resistance Rm of the measurement section resistor 22. The comparator 21 is configured to amplify the voltage difference between two wires connected to the first terminal t1 or the third terminal t3 and transmit a signal to the control section 30. More specifically, the comparator 21 transmits a signal to the control section 30 for specifying the input variable resistance R1 using a voltage drop value obtained by dropping a predetermined output value of the DC current source S due to the input variable resistance R1 and the resistance Rm of the measurement section resistor 22.

[0026] The input resistance measuring unit 20 includes a capacitor C2 connected between two terminals of the comparator 21. The capacitor C2, together with the measuring resistor 22, functions as a low-pass filter circuit for suppressing external AC signals input to the comparator 21. For example, a film capacitor is used as the capacitor C2. The measuring resistor 22 is provided on one of the wires connected to the comparator 21, the wire connected to the resistor 11, and together with the capacitor C2, forms a low-pass filter circuit. The measuring resistor 22 is selected to have a value sufficiently larger than the wiring impedance of the wire connected to the comparator 21 so that the wiring impedance can be ignored, but smaller than the overall resistance Rz of the resistor 11. The DC current source S may be, for example, a well-known power supply for generating a minute DC current.

[0027] The control unit 30 includes a processor such as a CPU (Central Processing Unit), a ROM (Read Only Memory), a RAM (Random Access Memory), and a GPU (Graphics Processing Unit). The control unit 30 also includes a storage unit 31. When adjusting the output variable resistance R2, which is the resistance between the second terminal t2 and the third terminal t3, to a desired output resistance Ro, the control unit 30 controls the drive unit 40 to change the contact position P at which the wiper 12 contacts the resistor 11 based on the measured value of the input variable resistance R1, which is the resistance between the first terminal t1 and the third terminal t3, measured by the input resistance measurement unit 20. The control performed by the control unit 30 will be described in detail later.

[0028] The storage unit 31 includes a nonvolatile memory or the like, and stores a plurality of contact positions P of the slider 12 with respect to the resistor 11, and the input-side variable resistance value R1 and the output-side variable resistance value R2 for each of the plurality of contact positions P. The storage unit 31 is also configured to store variable resistance relationship information that indicates the relationship between the input-side variable resistance value R1 and the output-side variable resistance value R2.

[0029] The driving unit 40 supports a shaft portion (not shown) included in the slider 12, and is configured to change the contact position P of the slider 12 with respect to the resistor 11 in response to a control command from the control unit 30. The driving unit 40 is, for example, a single-axis actuator including a servo motor with an encoder, and moves while supporting the shaft of the slider 12, thereby continuously moving the position of the slider 12 to any desired position. The driving unit 40 also transmits information about the contact position P of the slider 12 with respect to the resistor 11 after movement to the control unit 30.

[0030] The capacitor C1 functions as a DC blocking circuit and is configured to block DC power flowing through the second terminal t2 to the load 60 (see FIG. 3) side of the variable resistance device 100. For example, a ceramic capacitor is used as the capacitor C1.

[0031] (Operation of Variable Resistance Device) Next, the operation of the variable resistance device 100 having the above-described configuration will be described using an example in which the variable resistance device 100 is incorporated into a load driving circuit 200 as shown in FIG.

[0032] As shown in FIG. 3 , the load drive circuit 200 includes a power supply 50, switches Sw1 and Sw2, a load 60 driven by AC power, a variable resistance device 100, and a capacitor C3. The load drive circuit 200 converts DC power output from the power supply 50 into AC power by controlling the opening and closing timing and duration of the switches Sw1 and Sw2, thereby driving the load 60. In this case, ringing that occurs when the switch Sw2 opens and closes may cause the operation of the load 60 to become unstable. In this first embodiment, to ensure stable operation of the load 60, a snubber circuit, for example, a ceramic capacitor C3 and the variable resistance device 100 connected in series, is provided in parallel with the switch Sw2 to suppress ringing that occurs when the switch Sw2 opens and closes. More specifically, a case will be described in which the output-side variable resistance value R2 is set to a predetermined output resistance value Ro that can reduce ringing of the switch Sw2.

[0033] First, the control unit 30 acquires information that the output variable resistance value R2 has been set to the output resistance value Ro by an operator using an operation unit (not shown). Note that the desired output resistance value Ro is set by the operator according to the load 60 to which the variable resistance device 100 is connected.

[0034] Next, the control unit 30 calculates the input resistance Ri corresponding to the desired output resistance Ro based on the variable resistance-related information stored in the memory unit 31. In this first embodiment, the variable resistance-related information is a formula for obtaining the input variable resistance R1 based on the output variable resistance R2. Specifically, the variable resistance-related information is the formula R1 = Rz + 2Rc + 2Rs - R2. In this first embodiment, Rz, Rc, and Rs are known fixed resistance values. Therefore, when the output variable resistance R2 is the output resistance Ro, the input resistance Ri, which is the target value for the input variable resistance R1, is calculated using the formula Ri = Rz + 2Rc + 2Rs - Ro, which shows a linear relationship. The variable resistance-related information is updated at predetermined intervals and stored in the memory unit 31 to correspond to the resistance Rc of the contact resistor 3 and the resistance Rs of the slider resistor 4, which have changed over time.

[0035] Next, the control unit 30 starts controlling the drive unit 40 to move the position of the wiper 12 from the first terminal t1 side to the second terminal t2 side while measuring the input variable resistance value R1 using the input resistance measurement unit 20. In the first embodiment, this control is performed while the load 60 is in operation. The control unit 30 obtains the current input variable resistance value R1 based on the signal obtained from the input resistance measurement unit 20, and controls the drive unit 40 by feedback control to change the position of the wiper 12 until the input variable resistance value R1 becomes equal to the desired input resistance value Ri. When the input variable resistance value R1 matches the input resistance value Ri, the control unit 30 controls the drive unit 40 to stop driving, and determines the position of the wiper 12 relative to the resistor 11.

[0036] (Effects of First Embodiment) Next, effects of the first embodiment will be described.

[0037] The variable resistance device 100 of the first embodiment described above includes a variable resistor 10 including a resistor 11 having a first terminal t1 and a second terminal t2, and a slider 12 having a third terminal t3, and configured so that the position at which the slider 12 contacts the resistor 11 can be changed; a drive unit 40 that moves and changes the position of the slider 12 that contacts the resistor 11; an input-side resistance measuring unit 20 that measures an input-side variable resistance value R1, which is the resistance value between the first terminal t1 and the third terminal t3; and a control unit 30 that controls the drive unit 40 so as to change the position at which the slider 12 contacts the resistor 11 based on the input-side variable resistance value R1 measured by the input-side resistance measuring unit 20 when adjusting an output-side variable resistance value R2, which is the resistance value between the second terminal t2 and the third terminal t3, to a desired output resistance value Ro. As a result, the position of the wiper 12 is changed based on the input variable resistance R1 measured by the input resistance measuring unit 20, so that the input resistance Ri can be adjusted while measuring the actual value of the input variable resistance R1. As a result, even if the state of the variable resistor 10 changes, the output variable resistance R2 of the variable resistor 10 can be set to the desired output resistance Ro.

[0038] The first embodiment further includes a memory unit 31 that stores variable resistance relationship information indicating the relationship between the input variable resistance R1 and the output variable resistance R2. To adjust the output variable resistance R2 to a desired output resistance Ro, the control unit 30 identifies the input resistance Ri corresponding to the desired output resistance Ro based on the variable resistance relationship information acquired from the memory unit 31, and controls the drive unit 40 to change the contact position of the wiper 12 with the resistor 11 to a position where the input resistance Ri is equal to the measured value of the input variable resistance R1 measured by the input resistance measurement unit 20. This allows the contact position of the wiper 12 with the resistor 11 to be moved to an appropriate position based on the measured value of the input variable resistance R1, even when adjusting the output variable resistance R2, one of the variable resistance values ​​of the resistor 11, to a desired output resistance Ro for suppressing signal noise such as ringing. As a result, the output variable resistance R2 can be adjusted to the desired output resistance Ro based on the measured value of the input variable resistance R1.

[0039] Furthermore, in the first embodiment, when adjusting the output variable resistance R2 to the desired output resistance Ro, the control unit 30 controls the drive unit 40 to change the contact position of the wiper 12 with respect to the resistor 11 based on the input variable resistance R1 measured by the input resistance measurement unit 20 while the load 60 connected to the second terminal t2 of the resistor 11 is in operation. As a result, even if the output variable resistance R2 temporarily changes due to a positional shift of the wiper 12 caused by vibration while the load 60 is in operation, the output variable resistance R2 can be adjusted without stopping the operation of the load 60.

[0040] Furthermore, the first embodiment further includes a capacitor C1 as a DC blocking circuit connected between the load 60, which is operated by input of AC power, and the second terminal t2, and the input resistance measuring unit 20 is connected to the first terminal t1 of the resistor 11 and the third terminal t3 of the wiper 12. As a result, even when the load 60 is driven by AC power, the DC power used by the input resistance measuring unit 20 is blocked by the DC blocking circuit provided between the second terminal t2 and the load 60, preventing it from being supplied to the load. As a result, the input variable resistance R1, which is the resistance between the first terminal t1 of the resistor 11 and the third terminal t3 of the wiper 12, can be measured and adjusted while the load 60, which uses AC power, is in operation.

[0041] In the first embodiment, the variable resistance relationship information stored in the storage unit 31 includes a formula for calculating the output variable resistance value R2 based on the input variable resistance value R1. This allows the control unit 30 to easily identify the input resistance value Ri corresponding to the desired output resistance value Ro based on the formula stored in the storage unit 31 that indicates the relationship between the input variable resistance value R1 and the output variable resistance value R2.

[0042] Second Embodiment Next, a variable resistance device 110 according to a second embodiment will be described with reference to Fig. 4. The configuration of the variable resistance device 110 according to the second embodiment is the same as that of the variable resistance device 100 shown in Fig. 1, except that an output-side resistance measuring unit 70 and a switch Sw3 are added. Note that a description of the second embodiment common to the first embodiment will be omitted.

[0043] As described above, the variable resistance device 110 according to the second embodiment has the same configuration as the variable resistance device 100 according to the first embodiment, but also includes an output resistance measurement unit 70 and a switch Sw3. The output resistance measurement unit 70 includes a configuration equivalent to that of the input resistance measurement unit 20 shown in FIG. 1 , is connected to the second terminal t2 and the third terminal t3 by wiring including the switch Sw3, and measures the output variable resistance R2 between the second terminal t2 and the third terminal t3. Note that the switch Sw3 is controlled by the control unit 30 to be open while the load 60 connected to the second terminal t2, as shown in FIG. 3 , is in operation, and is closed only when the output variable resistance R2 is measured by the output resistance measurement unit 70.

[0044] In this second embodiment, unlike the first embodiment, the resistance value Rc of the contact resistor 3 of the variable resistor 10 shown in Figure 2 changes for each contact position P between the resistor 11 and the wiper 12. In this case, as explained in the first embodiment, the input variable resistance value R1 satisfies the relational expression R1 = Rz + 2Rc + 2Rs - R2. However, even if the target value of the output variable resistance value R2 is determined to be the output resistance value Ro, the input resistance value Ri, which is the target value of the input variable resistance value R1, cannot be determined because it includes the variable resistance value Rc.

[0045] In the second embodiment, the storage unit 31 stores variable resistance relationship information indicating the relationship between the input variable resistance value R1 and the output variable resistance value R2 without using the above-mentioned relational expression (without using the resistance value Rc as a variable). The storage unit 31 is configured to store a plurality of contact positions P of the wiper 12 with respect to the resistor 11. The storage unit 31 is also configured to store previously measured values ​​of the input variable resistance value R1 and the output variable resistance value R2 corresponding to the plurality of contact positions P. In other words, the storage unit 31 stores, as the variable resistance relationship information, a table that associates the input variable resistance value R1 with the output variable resistance value R2 for each of the plurality of contact positions P. Specifically, multiple contact positions P are stored as coordinate data (Pa, Pb, Pc), the input side variable resistance value R1 corresponding to the coordinate data of the contact position P is measured as (R1a, R1b, R1c), and the output side variable resistance value R2 at the position corresponding to the coordinate data of the contact position P is measured as (R2a, R2b, R2c), and these data are stored as a table.

[0046] The storage unit 31 also stores, as variable resistance relationship information, an approximate expression that represents the correlation between the input variable resistance value R1 and the output variable resistance value R2, which is generated based on the above table. Therefore, when an operator or the like sets the target value of the output variable resistance value R2 to the output resistance value Ro, the control unit 30 determines the input resistance value Ri, which is the target value of the input variable resistance value R1, based on the above table or approximate expression. Thereafter, the control unit 30 controls the drive unit 40 to change the position P of the contact point P of the slider 12 with respect to the resistor 11 so that the input variable resistance value R1 becomes the input resistance value Ri.

[0047] Furthermore, the control unit 30 updates and stores in the memory unit 31, at any timing, the past measured values ​​of the input-side variable resistance value R1 and the output-side variable resistance value R2 corresponding to the plurality of contact positions P, based on signals communicated by the input-side resistance measuring unit 20 and the output-side resistance measuring unit 70. In the second embodiment, the control unit 30 updates and stores in the memory unit 31 the measured values ​​of the input-side variable resistance value R1 and the output-side variable resistance value R2 corresponding to the plurality of contact positions P as a table every ten times the control unit 30 adjusts the contact position P of the wiper 12 relative to the resistor 11. Furthermore, the control unit 30 is configured to update and store the approximate formula as variable resistance relationship information based on the table of the input-side variable resistance value R1 and the output-side variable resistance value R2 corresponding to the plurality of contact positions P stored in the memory unit 31.

[0048] (Effects of Second Embodiment) Next, effects of the second embodiment will be described.

[0049] The second embodiment further includes an output resistance measuring unit 70 that is connected to the second terminal t2 of the resistor 11 and the third terminal t3 of the wiper 12 and measures the output variable resistance R2. This allows the output variable resistance R2 to be adjusted to a desired output resistance Ro while measuring the output resistance Ro.

[0050] In the second embodiment, the memory unit 31 is configured to store a plurality of contact positions of the wiper 12 with the resistor 11, and to update and store the stored variable resistance-related information based on the measured values ​​of both the input variable resistance value R1 and the output variable resistance value R2 corresponding to each of the plurality of positions. As a result, even if the state of the variable resistor 10 changes (deteriorates) due to wear of the wiper 12 or the like, the variable resistance-related information after the change in the resistance characteristics of the variable resistor 10 is updated and stored in the memory unit 31 based on the new measured value. As a result, even if the state of the variable resistor 10 changes, the output variable resistance value R2 can be appropriately set based on the input variable resistance value R1.

[0051] In the second embodiment, the memory unit 31 is configured to store measured values ​​of at least one of the input variable resistance value R1 and the output variable resistance value R2 at each of a plurality of positions. This allows an operator to compare the measured value stored in the memory unit 31 with the current measured value. As a result, the operator can easily find that the resistance characteristics of the variable resistor 10 have changed due to wear of the slider 12 or the like.

[0052] In the second embodiment, the variable resistance relationship information stored in the storage unit 31 includes a table that associates the input variable resistance value R1 with the output variable resistance value R2, and an approximate expression that represents the correlation between the input variable resistance value R1 and the output variable resistance value R2. This allows the control unit 30 to easily identify the input resistance value Ri that corresponds to the desired output resistance value Ro based on the calculation formula, table, or approximate expression that represents the relationship between the input variable resistance value R1 and the output variable resistance value R2, which is stored in the storage unit 31.

[0053] The other effects of the second embodiment are the same as those of the first embodiment.

[0054] [Modifications] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is defined by the claims, not by the description of the above-mentioned embodiments, and further includes all modifications (modifications) within the meaning and scope of the claims.

[0055] For example, in the first and second embodiments described above, an example was shown in which the storage unit 31 was included inside the control unit 30, but the present invention is not limited to this. In the present invention, the storage unit 31 may be provided separately from the control unit 30. In this case, the storage unit 31 may be a non-volatile memory, a magnetic tape, a hard disk, or the like.

[0056] In the first embodiment, the variable resistance device 100 is incorporated into the load drive circuit 200, but the present invention is not limited to this. In the present invention, the variable resistance device 100 is widely applicable to circuits used for changing input / output impedance, adjusting frequency, adjusting volume, changing output resistance, etc. For example, the variable resistance device 100 may be incorporated into an RC filter circuit, an RLC resonant circuit, a speaker amplifier, a radio wave transmission circuit, or an ultrasonic pulser circuit.

[0057] In the first and second embodiments, the variable resistor 10 is a linear potentiometer, the resistor 11 is a carbon film, and the wiper 12 is a conductive metal brush made of copper alloy or the like, but the present invention is not limited to this. In the present invention, any configuration may be used as long as the resistance value of the variable resistor 10 can be adjusted while being measured. The variable resistor 10 may be a rotary potentiometer, the resistor 11 may be a conductive film other than carbon film, or the wiper 12 may be a conductive metal brush made of a material other than a copper alloy.

[0058] In the first and second embodiments, the input variable resistance value R1 and the output variable resistance value R2 have a linear relationship, but the present invention is not limited to this. In the present invention, the input variable resistance value R1 and the output variable resistance value R2 may have a nonlinear relationship.

[0059] Furthermore, while the first and second embodiments have described examples in which the capacitor C1 is used as the DC blocking circuit, the present invention is not limited to this. In the present invention, the DC blocking circuit may be a switch or relay circuit that is opened when the input resistance measurement unit 20 measures the input variable resistance value R1.

[0060] In the first and second embodiments, the input-side resistance measuring unit 20 includes a DC current source S therein, but the present invention is not limited to this. In the present invention, the input-side resistance measuring unit 20 only needs to include something capable of supplying a constant current therein, and may be configured to include, for example, a DC voltage source.

[0061] In the first and second embodiments, the driving unit 40 includes a servo motor having an encoder, but the present invention is not limited to this. In the present invention, the driving unit 40 may use a stepping motor that does not include an encoder, or may use a DC motor or a linear motor.

[0062] In the first and second embodiments, when the output variable resistance R2 is to be set to a desired output resistance Ro, the input resistance Ri corresponding to the output resistance Ro is identified and the input variable resistance R1 is measured and adjusted, but the present invention is not limited to this. In the present invention, for example, when impedance matching is performed and the target value of the input impedance is known, the target input resistance Ri of the input variable resistance R1 may be directly set by an operator or the like and used to change the input variable resistance R1 without determining the target output resistance Ro of the output variable resistance R2.

[0063] In the first and second embodiments, the control unit 30 specifies the input resistance Ri corresponding to the desired output resistance Ro based on the variable resistance-related information acquired from the storage unit 31 in order to adjust the output variable resistance R2 to the desired output resistance Ro, and controls the drive unit 40 to change the contact position of the wiper 12 with the resistor 11 to a position where the measured value of the input variable resistance R1 measured by the input resistance measuring unit 20 becomes equal to the input resistance Ri. However, the present invention is not limited to this. In the present invention, the control unit 30 may control the drive unit 40 to change the contact position of the wiper 12 with the resistor 11 to a position that achieves the desired output resistance Ro, for example, based on the measurement value of the output resistance measuring unit 70, without acquiring the variable resistance-related information from the storage unit 31.

[0064] In the first and second embodiments, the control unit 30 controls the drive unit 40 to change the contact position of the wiper 12 with respect to the resistor 11 based on the input variable resistance R1 measured by the input resistance measurement unit 20 while the load 60 connected to the second terminal t2 of the resistor 11 is in operation when adjusting the output variable resistance R2 to the desired output resistance Ro. However, the present invention is not limited to this. In the present invention, the contact position of the wiper 12 with respect to the resistor 11 may be changed based on the input variable resistance R1 measured by the input resistance measurement unit 20 when the load 60 is not in operation.

[0065] In the first and second embodiments, the example is shown in which the capacitor C1 serving as a DC interrupting circuit is connected between the load 60, which is operated by input of AC power, and the second terminal t2, and the input-side resistance measuring unit 20 is connected to the first terminal t1 of the resistor 11 and the third terminal t3 of the wiper 12. However, the present invention is not limited to this. In the present invention, the capacitor C1 serving as a DC interrupting circuit may be omitted, and the position at which the wiper 12 contacts the resistor 11 may be changed when the load 60 is stopped.

[0066] Furthermore, in the second embodiment, an example was shown in which the output resistance measuring unit 70, which is connected to the second terminal t2 of the resistor 11 and the third terminal t3 of the wiper 12 and measures the output variable resistance value R2, is further provided, and the memory unit 31 is configured to store a plurality of contact positions P of the wiper 12 with respect to the resistor 11 and to update and store the stored variable resistance-related information based on the measured values ​​of both the input variable resistance value R1 and the output variable resistance value R2 corresponding to each of the plurality of contact positions P. However, the present invention is not limited to this. For example, in the present invention, if the resistance value Rc of the contact resistor 3 is a constant value, it is not necessary to provide the output resistance measuring unit 70, and it is not necessary to update and store the variable resistance-related information corresponding to each of the plurality of contact positions P, as in the first embodiment.

[0067] In the second embodiment, the storage unit 31 is configured to store the measured values ​​of at least one of the input variable resistance value R1 and the output variable resistance value R2 at each of the plurality of contact positions P. However, the present invention is not limited to this. In the present invention, the measured values ​​of both the input variable resistance value R1 and the output variable resistance value R2 at each of the plurality of contact positions P may be stored.

[0068] In the second embodiment, the previous measured values ​​of the input variable resistance value R1 and the output variable resistance value R2 corresponding to the plurality of contact positions P are updated and stored in the storage unit 31 as a table every 10 adjustments of the contact position P of the slider 12 with respect to the resistor 11, but the present invention is not limited to this. In the present invention, the previous measured values ​​stored in the storage unit 31 may be updated and stored at any timing. For example, the previous measured values ​​may be updated and stored in the storage unit 31 as a table every predetermined time or every time the control unit 30 is started.

[0069] REFERENCE SIGNS LIST 10 variable resistor 11 resistor 12 wiper 20 input-side resistance measuring section 30 control section 31 memory section 40 drive section 60 load 70 output-side resistance measuring section 100, 110 variable resistance device t1 first terminal t2 second terminal t3 third terminal R1 input-side variable resistance value R2 output-side variable resistance value

Claims

1. A variable resistance device comprising: a variable resistor including a resistor having a first terminal and a second terminal, and a slider having a third terminal, the variable resistance device being configured so that the position at which the slider contacts the resistor can be changed; a drive unit which moves and changes the position of the slider which contacts the resistor; an input side resistance measuring unit which measures an input side variable resistance value which is the resistance value between the first terminal and the third terminal; and a control unit which controls the drive unit to change the position at which the slider contacts the resistor based on the input side variable resistance value measured by the input side resistance measuring unit when adjusting an output side variable resistance value which is the resistance value between the second terminal and the third terminal to a desired output resistance value.

2. A variable resistance device as described in claim 1, further comprising a memory unit that stores variable resistance relationship information indicating the relationship between the input side variable resistance value and the output side variable resistance value, wherein the control unit, in order to adjust the output side variable resistance value to the desired output resistance value, identifies an input resistance value corresponding to the desired output resistance value based on the variable resistance relationship information obtained from the memory unit, and controls the drive unit to change the contact position of the slider with the resistor to a position where the measured value of the input side variable resistance value measured by the input side resistance measuring unit is equal to the input resistance value.

3. The variable resistance device of claim 1, wherein the control unit controls the drive unit to change the contact position of the slider with respect to the resistor based on the input side variable resistance value measured by the input side resistance measuring unit while a load connected to the second terminal of the resistor is in operation when adjusting the output side variable resistance value to the desired output resistance value.

4. The variable resistance device of claim 3, further comprising a DC blocking circuit connected between the load operated by input of AC power and the second terminal, and the input side resistance measuring unit is connected to the first terminal of the resistor and the third terminal of the slider.

5. The variable resistance device according to claim 4, further comprising an output resistance measuring section connected to the second terminal of the resistor and the third terminal of the slider, for measuring the output variable resistance value.

6. The variable resistance device according to claim 2, further comprising an output-side resistance measuring unit connected to the second terminal of the resistor and the third terminal of the slider for measuring the output-side variable resistance value, wherein the memory unit is configured to store a plurality of positions at which the slider contacts the resistor, and to update and store the stored variable resistance relationship information based on the measured values ​​of both the input-side variable resistance value and the output-side variable resistance value corresponding to each of the plurality of positions.

7. The variable resistance device according to claim 6, wherein the memory section is configured to store measured values ​​of at least one of the input variable resistance value and the output variable resistance value at each of the plurality of positions.

8. The variable resistance device described in claim 2, wherein the variable resistance relationship information stored in the memory unit includes at least one of a calculation formula for obtaining the input side variable resistance value based on the output side variable resistance value, a table that matches the input side variable resistance value with the output side variable resistance value, and an approximation formula that represents the correlation between the input side variable resistance value and the output side variable resistance value.

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