JP7337723B2 - Current supply circuit and resistance measuring device - Google Patents

Description

The present invention provides an amplifier that outputs an output voltage for supplying an output current to a load, and a current output that has the function of limiting the maximum output voltage (maximum absolute value) of this output voltage to a predetermined voltage. The present invention relates to a supply circuit and a resistance measuring device equipped with this current supply circuit.

As a current supply circuit of this type, the applicant of the present application has already proposed a constant current source disclosed in Patent Document 1 below. This proposed constant current source (current supply circuit) adjusts the voltage value of the voltage supplied to the resistor to be measured according to the resistance value (unknown) of the resistor to be measured in order to apply a constant current to the resistor to be measured. It is connected to the output terminal of the error amplifier circuit, and the positive maximum voltage (maximum absolute value) of the output voltage output from this output terminal is set to a predetermined positive voltage. Connected to the output terminal of the first voltage limiting circuit for limiting (for example, a circuit having an ideal diode circuit configured by an operational amplifier and a diode and a reference voltage generating circuit for outputting a predetermined positive voltage) and the error amplifier circuit A second voltage limiting circuit (for example, an ideal diode composed of an operational amplifier and a diode circuit and a reference voltage generation circuit that outputs a predetermined voltage on the negative side).

With this configuration, in this constant current source, each voltage limiting circuit (voltage limiting section) limits the voltage (output voltage) of the output terminal of the error amplifier circuit within a range between a predetermined positive voltage and a predetermined negative voltage. (limiting the maximum absolute value of the output voltage within a predetermined range), for example, application of an excessive voltage to the resistor to be measured can be avoided.

Japanese Patent Application Laid-Open No. 11-281688 (pages 4-5, FIG. 1)

However, the constant current generating circuit (constant current source) has the following problems to be solved. Specifically, in this constant current generation circuit, each voltage limiting circuit is connected to the output terminal of an error amplifier circuit that changes the voltage value of the voltage supplied to the resistor to be measured according to the resistance value (unknown) of the resistor to be measured. (Voltage limiting section) The operational amplifier is directly connected, and each voltage limiting circuit directly limits the output voltage output from the output terminal of the error amplifier circuit. In addition, in this constant current generation circuit, when the resistance value of the resistor to be measured is assumed to be large, the output voltage from the error amplifier circuit to the resistor to be measured is also high. The predetermined voltage on the side is defined as a voltage higher than this high voltage. Therefore, as an operational amplifier that constitutes each voltage limiting circuit, an operational amplifier with a high withstand voltage (high voltage) specification in which the withstand voltage on the positive side exceeds a predetermined voltage on the positive side and the withstand voltage on the negative side exceeds a predetermined voltage on the negative side ( Operational amplifiers with operating and input voltages exceeding ±several tens of volts (eg, ±30V) must be used. Semiconductor parts such as operational amplifiers with high breakdown voltage specifications (high voltage specifications) are compared with semiconductor parts with low breakdown voltage specifications (operation voltage and input voltage are, for example, ±15 V or less, low voltage specification operational amplifiers). Since the range of selection is narrowed and the cost is generally high, the degree of freedom in design is low and cost reduction is difficult.

The present invention has been made in view of such problems to be solved, and is a current supply circuit and a resistor that can avoid the use of high voltage specification semiconductor parts (high voltage specification operational amplifiers, comparators, etc.) in the voltage limiter. The main purpose is to provide a measuring device.

In order to achieve the above objects, a current supply circuit according to claim 1 amplifies an input voltage referenced to a circuit ground input to an input section through an input resistor and connects between the output section and the circuit ground. A current supply circuit for supplying an output current to the load, the current supply circuit having an amplifier unit for outputting an output voltage for applying the applied voltage to the load, wherein the output unit in the load a first resistor voltage dividing unit connected between a first terminal on the side and the circuit ground for dividing the applied voltage by a predetermined voltage division ratio and outputting a first divided voltage; a voltage limiting unit that inputs the divided voltage and compares it with a set voltage, and reduces the absolute value of the input voltage when the absolute value of the first divided voltage exceeds the absolute value of the set voltage. ing.

Further, the current supply circuit according to claim 2 is the current supply circuit according to claim 1, which is connected between the second terminal of the load on the circuit ground side and the circuit ground, and detects the output current as a detection voltage. the input voltage is input to the non-inverting input terminal as the input unit, the detection voltage is input to the inverting input terminal, and the output terminal is the It has an operational amplifier connected to the output.

The current supply circuit according to claim 3 is the current supply circuit according to claim 1, which is connected between the output section and the first terminal of the load to convert the output current into a detection voltage. an output detection resistor unit, connected between the output unit and the circuit ground, wherein the amplifier unit amplifies the input voltage and divides the output voltage output from the output unit by a predetermined voltage dividing ratio; a second resistive voltage dividing unit for inputting the first divided voltage and the second divided voltage and amplifying a difference voltage between the two divided voltages to generate a detection voltage; the input voltage is input to the non-inverting input terminal as the input section, the detection voltage is input to the inverting input terminal, and the output terminal is the output It has an operational amplifier connected to the unit.

A resistance measuring apparatus according to claim 4 comprises the current supply circuit according to any one of claims 1 to 3, and measuring the voltage value of the applied voltage and the current value of the output current. and a measuring unit that measures the resistance value of the load based on the current value.

According to the current supply circuit of claim 1 and the resistance measurement device of claim 4, an applied voltage is applied to the load connected between the output of the amplifier and the circuit ground, thereby outputting the voltage to the load. By providing the first resistance voltage dividing unit that divides the output voltage into a first divided voltage that is a low voltage and outputs the voltage to the voltage limiting unit while allowing current to be supplied, the voltage limiting unit is made of a semiconductor with low voltage specifications. It can be configured with components (such as a low voltage specification comparator), thereby avoiding the use of high voltage specification semiconductor components (such as a high voltage specification comparator).

According to the current supply circuit of claim 2 and the resistance measuring device of claim 4, the load is connected between the second terminal on the circuit ground side of the load and the circuit ground to convert the output current into the detection voltage. The amplifier has an input voltage input to a non-inverting input terminal as an input part, a detection voltage input to an inverting input terminal, and an output terminal connected to an output part. , the output current can be supplied to the load as an accurate constant current while avoiding the use of high-voltage semiconductor components in the voltage limiter, thereby reducing the resistance value of the load. It can be measured with sufficient accuracy.

According to the third aspect of the current supply circuit and the fourth aspect of the resistance measuring device, the first and second resistance voltage dividers are provided, so that the high voltage specification in the voltage limiter is achieved. It is possible to supply the output current to the load in a state close to a constant current while avoiding the use of semiconductor components for the differential amplifier and the use of high-voltage specification semiconductor components in the differential amplifier. Resistance values can be measured with the required accuracy.

1 is a configuration diagram of a current supply circuit 1A and a resistance measuring device 50A; FIG. 4 is a waveform diagram of the output voltage Vo for explaining the operation of the current supply circuit 1A; FIG. 2 is a configuration diagram of a current supply circuit 1B and a resistance measuring device 50B; FIG.

Embodiments of a current supply circuit and a resistance measuring device will be described below with reference to the accompanying drawings.

First, configurations of a current supply circuit 1A as a current supply circuit and a resistance measurement device 50A as a resistance measurement device will be described with reference to FIG.

First, the current supply circuit 1A will be described. The current supply circuit 1A includes a voltage input terminal 2, an input resistor 3, an amplifier section 4, a detection resistor section 5, a first resistor voltage dividing section 6, a voltage limiting section 7, and load connection terminals 8a and 8b. 2 is amplified by the amplifier 4 and applied to the load DUT connected between the load connection terminals 8a and 8b as the applied voltage Vap (the voltage across the load DUT). It is configured to be able to supply an output current Io to the DUT. Further, the current supply circuit 1A includes the first resistive voltage dividing unit 6 and the voltage limiting unit 7, so that the highest voltage (maximum absolute voltage value) of the applied voltage Vap can be limited to a predetermined voltage Vs. It is configured.

Specifically, in the current supply circuit 1A, a reference voltage source 9 is connected between the voltage input terminal 2 and the circuit ground G (the reference potential portion in the current supply circuit 1A). The reference voltage source 9 generates a reference voltage Vr and outputs it to the voltage input terminal 2 as a voltage with the potential of the circuit ground G as a reference. In this example, as an example, the reference voltage source 9 is configured as an AC constant voltage source, and is based on an AC constant voltage (constant sine wave voltage) having a predetermined constant amplitude and a predetermined constant frequency. Although it is configured to generate a voltage Vr and output it to the voltage input terminal 2, it is not limited to this configuration, and is configured as a DC constant voltage source and generates a DC voltage (DC A constant voltage) may be generated as the reference voltage Vr and output to the voltage input terminal 2 . The reference voltage source 9 may be separate from the current supply circuit 1A, or may be built in the current supply circuit 1A.

The input resistor 3 has one end connected to the voltage input terminal 2 and the other end connected to an input section 4a of the amplifier section 4, which will be described later. With this configuration, the reference voltage Vr output from the reference voltage source 9 to the voltage input terminal 2 is input to the input section 4 a of the amplifier section 4 via the input resistor 3 .

In this example, as an example, the amplifier unit 4 has a high voltage specification (an operating voltage exceeding ±several tens of volts (eg, ±30 V), and a specification capable of outputting a high voltage output voltage close to the operating voltage. ) (hereinafter also referred to as operational amplifier 4). Thus, in this example, the non-inverting input terminal of the operational amplifier 4 functions as the input section 4a of the amplifying section 4, and the other end of the input resistor 3 is connected to this non-inverting input terminal. Also, the inverting input terminal of the operational amplifier 4 functions as the other input section 4b of the amplifier section 4. FIG. An output terminal of the operational amplifier 4 functions as an output section 4c of the amplifier section 4 and is connected to one of the load connection terminals 8a and 8b, 8a. A detection resistor 5 is connected between the other load connection terminal 8b of the load connection terminals 8a and 8b and the circuit ground G. As shown in FIG. The detection resistor section 5 is composed of a resistor having a constant (known) resistance value, converts the output current Io flowing through the load DUT into a detection voltage Vd, and outputs the detected voltage Vd to the inverting input terminal of the operational amplifier 4 as the input section 4b. do.

With this configuration, the operational amplifier 4 is in a state in which the load DUT is connected between the load connection terminals 8a and 8b (that is, the load DUT is connected between the output terminal and the inverting input terminal of the operational amplifier 4, and the operational In the state where the negative feedback path of the amplifier 4 is configured), the detection voltage Vd input to the inverting input terminal is the input voltage Vi (normally the same as the reference voltage Vr) input to the non-inverting input terminal. A negative feedback operation is performed to control the output voltage Vo output from the output terminal (output section 4c) so that the voltages match. That is, since the reference voltage Vr is a constant AC voltage, the operational amplifier 4 controls the load DUT so that the detected voltage Vd is the same constant AC voltage as the reference voltage Vr (in other words, the output current Io is a constant AC current). ), when the resistance of the load DUT is small, the output voltage Vo, which is an AC voltage, is lowered accordingly, and when the resistance of the load DUT is large, the output voltage Vo is raised accordingly. Perform current control operation.

In addition, as in this example, in a configuration in which the detection resistor unit 5 is connected to the circuit ground G side of the load DUT, the difference between the applied voltage Vap applied to the load DUT and the detection voltage Vd (=input voltage Vi) is Since the added voltage becomes the output voltage Vo, the voltage (Vo-Vi) obtained by subtracting the input voltage Vi (=Vd) from the output voltage Vo is applied to the load DUT as the applied voltage Vap. In this case, since the input voltage Vi is constant (same as the reference voltage Vr) in a normal state (a state in which voltage limitation is not applied to the input voltage Vi by the first resistor voltage dividing unit 6 and the voltage limiting unit 7), , the applied voltage Vap rises and falls in proportion to the output voltage Vo.

The amplifier section 4 is not limited to a circuit configuration composed of one operational amplifier as in this example, and various circuit configurations can be used as long as the circuit configuration has an operational amplifier arranged at the input stage. can be adopted. For example, although not shown, the amplifier section 4 may have a circuit configuration including an input-stage operational amplifier and an output-stage buffer circuit connected to the output terminal of the operational amplifier. functions as an output section 4 c of the amplifier section 4 .

Further, in the current supply circuit 1A of this example, the load DUT connected between the load connection terminals 8a and 8b is prevented from being applied with a voltage exceeding the maximum applied voltage of the load DUT as described above. , a first resistive voltage dividing unit 6 and a voltage limiting unit 7 to limit the output voltage Vo output from the operational amplifier 4 to a predetermined voltage Vs, thereby reducing the voltage Vap applied to the load DUT to the load A configuration is employed that can be limited to less than the maximum applied voltage of the DUT.

Specifically, in this example, the output voltage Vo to be limited is an AC voltage (applied voltage Vap is the same) in which peak voltages appear in both the positive voltage region and the negative voltage region. In 1A, as a set of the first resistor voltage divider 6 and the voltage limiter 7, a voltage waveform including a positive peak that is the positive peak voltage of the output voltage Vo (a voltage waveform in the vicinity of the positive peak) is shifted to the positive side. and a voltage waveform including a negative peak that is the peak voltage on the negative side of the output voltage Vo (near the negative peak). voltage waveform) to a predetermined negative voltage Vsb (a voltage whose absolute value is the same as the absolute value of the predetermined positive voltage Vsa). I have.

In this case, the first resistive voltage dividers 6a and 6b are connected to the output terminal 4c of the amplifier 4 (in this example, the output terminal of the operational amplifier 4) of the pair of terminals TM1 and TM2 of the load DUT. 1 terminal) TM1 and the circuit ground G (that is, between the load connection terminal 8a to which the terminal TM1 of the load DUT is connected and the circuit ground G) so as to apply the output voltage Vo to each of the predetermined voltages. By dividing the voltage by the voltage dividing ratio, the first resistor voltage dividing section 6a outputs the first divided voltage V1a, and the first resistor voltage dividing section 6b outputs the first divided voltage V1b.

As an example, the first resistor voltage dividing unit 6a is composed of two resistors 11a and 12a connected in series. When the resistance value of the resistor 12a connected to the circuit ground G is R2, the resistance values R1 and R2 ( For example, a resistance value of several tens of kΩ to several hundreds of kΩ that satisfies R1>R2 is defined. With this configuration, even when the output voltage Vo is high, the first resistor voltage dividing unit 6a can set the first divided voltage V1a to a low voltage specification (for example, a low operating voltage such as ±15 V or ±5 V). voltage, and the input voltage is also limited to a low voltage within the corresponding operating voltage range) operational amplifiers and comparators (general operational amplifiers and comparators such as those used in the voltage limiter 7a ) can be output as a low voltage that meets the input specifications.

Similarly to the first resistance voltage dividing portion 6a, the first resistance voltage dividing portion 6b is also composed of two series-connected resistors 11b and 12b. R3 is the resistance value of the resistor 11b connected to the circuit ground G, and R4 is the resistance value of the resistor 12b connected to the circuit ground G. Each resistance value R3, R4 (for example, a resistance value of about several tens of kΩ to several hundreds of kΩ satisfying R3>R4) is defined so as to satisfy R3 and R4. With this configuration, even when the output voltage Vo is high, the first resistor voltage dividing unit 6b can also divide the first voltage dividing voltage V1b into a low voltage specification operational amplifier in the same way as the first voltage dividing unit 6a. and a comparator (a general operational amplifier or comparator used in the voltage limiter 7b) can be output as a low voltage that matches the input specifications.

Note that the current supply circuit 1A of the present example adopts a configuration in which the first resistance voltage dividing portion 6a and the first resistance voltage dividing portion 6b are used as the first resistance voltage dividing portion 6, but for example, , when the respective voltage division ratios of the first resistance voltage dividing portion 6a and the first resistance voltage dividing portion 6b are equal, one of the first resistance voltage dividing portion 6a and the first resistance voltage dividing portion 6b is set to the voltage limiting portion It can also be configured to be used as the first resistance voltage dividing section 6 common to 7a and 7b. In addition, in the current supply circuit 1A of this example, since the output voltage Vo is an alternating voltage, as described above, the first resistor voltage dividing unit 6a for limiting the voltage of the output voltage Vo in the positive voltage region and A configuration including a set of the voltage limiting section 7a and a set of the first resistor voltage dividing section 6b and the voltage limiting section 7b for limiting the voltage of the output voltage Vo in the negative voltage region is adopted. is not limited to For example, when a positive DC constant voltage is input as the reference voltage Vr and the output voltage Vo is a positive DC voltage, only the set of the first resistor voltage dividing unit 6a and the voltage limiting unit 7a is provided. When a negative DC constant voltage is input as the output voltage Vo and the output voltage Vo is a negative DC voltage, it is also possible to employ a configuration including only a set of the first resistor voltage dividing section 6b and the voltage limiting section 7b.

The voltage limiter 7a includes, for example, a comparator 21a, a set voltage source 22a, and a unidirectional element 23a. The comparator 21a is composed of a general comparator of low voltage specifications. The first divided voltage V1a is input from the first resistor voltage divider 6a to the inverting input terminal of the comparator 21a. The comparator 21a can also be configured by using a general operational amplifier with low voltage specifications as a comparator (used in an open loop).

The set voltage source 22a is composed of a variable positive voltage source that outputs a positive voltage, and generates a preset positive set voltage V2a (voltage based on the potential of the circuit ground G). Also, the set voltage source 22a outputs the generated positive side set voltage V2a to the non-inverting input terminal of the comparator 21a. The set voltage source 22a is configured so that the user of the current supply circuit 1A can arbitrarily set the voltage value of the positive side set voltage V2a. For example, when limiting the output voltage Vo to the predetermined voltage Vsa, the set voltage V2a is set to V2a=Vsa×R2/(R1+R2).

The unidirectional element 23a is connected between the input section 4a (the non-inverting input terminal of the operational amplifier 4) of the amplifier section 4 and the output terminal of the comparator 21a, and the output terminal side of the comparator 21a from the input section 4a side. It allows the passage of current in the direction towards it and blocks the passage of current in the opposite direction. In this example, as an example, the unidirectional element 23a is composed of a diode as a discrete component (hereinafter also referred to as the diode 23a). Therefore, the diode 23a has its anode terminal connected to the input section 4a and its cathode terminal connected to the output terminal of the comparator 21a.

As an example, the voltage limiter 7b includes a comparator 21b, a set voltage source 22b, and a unidirectional element 23b. The comparator 21b is composed of a general comparator with the same low voltage specifications as the comparator 21a. The inverting input terminal of the comparator 21b receives the first divided voltage V1b from the first resistor voltage divider 6b. The comparator 21b can also be configured by using a general operational amplifier with low voltage specifications as a comparator (used in an open loop).

The set voltage source 22b is composed of a variable negative voltage source that outputs a negative voltage, and generates a preset negative set voltage V2b (voltage based on the potential of the circuit ground G). Also, the set voltage source 22b outputs the generated negative side set voltage V2b to the non-inverting input terminal of the comparator 21b. The set voltage source 22b is configured so that the user of the current supply circuit 1A can arbitrarily set the voltage value of the negative side set voltage V2b. For example, when limiting the output voltage Vo to a predetermined voltage Vsb (negative voltage), the set voltage V2b is set to V2b=Vsb×R4/(R3+R4).

The unidirectional element 23b is connected between the input section 4a and the output terminal of the comparator 21b, permits the passage of current in the direction from the output terminal side of the comparator 21a toward the input section 4a side, and allows current to pass in this direction. block the passage of current in the opposite direction. In this example, as an example, the unidirectional element 23b is composed of a diode as a discrete component, like the unidirectional element 23a (hereinafter also referred to as the diode 23b). Therefore, the diode 23b has its anode terminal connected to the output terminal of the comparator 21a and its cathode terminal connected to the input section 4a.

The unidirectional elements 23a and 23b can also be configured using bipolar transistors or field effect transistors (not shown) instead of diodes as discrete components.

Next, the resistance measuring device 50A will be described. The resistance measuring device 50A includes the current supply circuit 1A, the measuring section 51 and the output section 52 described above. The measurement unit 51 includes, for example, an A/D converter and a computer (both not shown), measures the current value of the output current Io based on the detection voltage Vd output from the detection resistor unit 5, and By measuring the voltage value of the applied voltage Vap and dividing the measured voltage value of the applied voltage Vap by the measured current value of the output current Io, the resistance value Rx of the load DUT is measured (calculated). The measuring unit 51 also outputs the measured resistance value Rx to the output unit 52 . Since the current value of the output current Io is known in the current supply circuit 1A, the measurement unit 51 may of course use this known current value when measuring the resistance value Rx.

The output unit 52 is configured by, for example, a display device, and displays (outputs) the resistance value Rx output from the measurement unit 51 on the screen. The output unit 52 can also be configured by various interface circuits instead of the display device. and stores the resistance value Rx in a storage medium connected to the medium interface circuit.

Next, operations of the current supply circuit 1A and the resistance measuring device 50A will be described. As a premise, it is assumed that the operational amplifier 4 can operate at an operating voltage exceeding ±50V and can change the output voltage Vo within the voltage range of ±50V. Further, the detection resistor section 5 is assumed to be composed of a fixed resistor of 100Ω as an example. Also, the amplitude of the reference voltage Vr output from the reference voltage source 9 is assumed to be 0.1 V as an example. As a result, since the output current Io has an amplitude of 1 mA (=0.1/100), in the current supply circuit 1A, the maximum resistance value of the load DUT that can be connected between the load connection terminals 8a and 8b is , about 50 kΩ (49.9 kΩ=(50−0.1)/0.001). Further, it is assumed that the voltage division ratios of the first resistance voltage dividing portions 6a and 6b are the same at 1/10. Also, the voltage drop in each of the unidirectional elements 23a and 23b is assumed to be zero volts for easy understanding. It is also assumed that the load DUT to be measured has a normal resistance value Rx within a normal range of, for example, 10 kΩ to 25 kΩ, and the maximum applied voltage (breakdown voltage) is specified at 28V. Also, in the load DUT to be measured, the resistance value Rx may greatly exceed the above normal range when there is an abnormality.

First, prior to measuring the resistance of the load DUT, the user considers that the maximum applied voltage (breakdown voltage) of the applied voltage Vap to the load DUT is 28 V, and the voltage applied from the current supply circuit 1A to the load DUT is In order to prevent the applied voltage Vap from exceeding 28 V, as an example, the predetermined voltage Vsa, which is the positive limiting voltage of the output voltage Vo, becomes +28 V, and the predetermined voltage Vsb, which is the negative limiting voltage of the output voltage Vo. is -28V, the positive side set voltage V2a of the set voltage source 22a and the negative side set voltage V2b of the set voltage source 22b are set. As described above, the applied voltage Vap is the voltage obtained by subtracting the input voltage Vi (the same as the reference voltage Vr in the normal state) from the output voltage Vo. Therefore, the absolute value of the applied voltage Vap is the absolute value of the output voltage Vo is always lower than the value by the absolute value of the input voltage Vi. For this reason, the positive limit voltage value of the output voltage Vo is made equal to the positive maximum applied voltage of the applied voltage Vap, and the negative limit voltage value of the output voltage Vo is set to the negative side of the applied voltage Vap. By making it the same as the maximum applied voltage, it is possible to suppress the applied voltage Vap to the load DUT below the maximum applied voltage.

Specifically, since the voltage division ratio of the first resistor voltage dividers 6a and 6b is 1/10, when the absolute value of the output voltage Vo is 28V, the voltage is output from the first resistor voltage dividers 6a and 6b. Each of the first divided voltages V1a and V1b has an absolute value of 2.8V. Therefore, the user operates the set voltage sources 22a and 22b to set the voltage value of the positive side set voltage V2a to +2.8 V (=Vsa×R2/(R1+R2)), and the voltage of the negative side set voltage V2b Set the value to −2.8V (=Vsb×R4/(R3+R4)). With some margin, the absolute value of the positive limiting voltage value of the output voltage Vo is set to be smaller than the absolute value of the maximum applied voltage on the positive side of the applied voltage Vap, and the negative side of the output voltage Vo is The absolute value of the limiting voltage value may be smaller than the absolute value of the maximum applied voltage on the negative side of the applied voltage Vap (in the above specific example, the absolute value of the limiting voltage value is set to 27 V or 26 V, for example). and correspondingly, the voltage values of the set voltages V2a and V2b may be +2.7V, -2.7V or +2.6V, -2.6V).

Next, the user connects one of the plurality of load DUTs to be measured between the load connection terminals 8a and 8b, and measures the resistance value Rx of this load DUT.

In this case, when the connected load DUT is normal (when the resistance value Rx is within the normal range), in the current supply circuit 1A, the operational amplifier 4 outputs from the detection resistor section 5 Negative feedback operation to control the output voltage Vo output from the output terminal so that the detected voltage Vd matches the input voltage Vi input to the non-inverting input terminal through the input resistor 3 (normally, the reference voltage Vr). , the amplitude (current value) of the output current Io flowing through the load DUT is controlled to 1 mA. Since the resistance value Rx of the load DUT is normally 10 kΩ or more and 25 kΩ or less, the absolute value of the output voltage Vo when an output current Io of 1 mA is supplied to the load DUT is 25.1 V (=25 kΩ×1 mA+0 .1V), and does not reach 28V, which is the absolute value of the limit voltage value in each of the voltage limiters 7a and 7b. Therefore, in the current supply circuit 1A, the operational amplifier 4 controls the output voltage Vo to be output by the reference numerals W1 and W1 in FIG. By changing the voltage value as indicated by W2, an output current Io is supplied to the load DUT at a specified current value (1 mA).

Accordingly, in the resistance measuring device 50A, the measuring unit 51 measures the output current Io based on the detected voltage Vd output from the detecting resistor unit 5, measures the applied voltage Vap, and calculates the measured applied voltage Vap. By dividing by the measured output current Io, the resistance value Rx of the load DUT is measured and output to the output section 52 . Note that the current supply circuit 1A supplies the load DUT with the output current Io of 1 mA, which is the specified current value, in this way, that is, the current supply circuit 1A operates as a constant current supply circuit. Sometimes, the current value of the output current Io is known, and a configuration can be adopted in which the measurement by the measuring section 51 is omitted. In this case, the measurement unit 51 measures the resistance value Rx of the load DUT from the known current value of the output current Io and the measured voltage value of the applied voltage Vap.

The output unit 52 displays (outputs) the resistance value Rx output from the measurement unit 51 on the screen. This completes the measurement of the resistance value Rx of the load DUT connected between the load connection terminals 8a and 8b.

On the other hand, when the load DUT connected between the load connection terminals 8a and 8b is not normal and its resistance value Rx exceeds the normal range (for example, a very large value such as 30 kΩ), the current supply circuit 1A Then, the operational amplifier 4 applies the detection voltage Vd output from the detection resistor section 5 to the non-inverting input terminal via the input resistor 3 in order to supply the output current Io of the specified current value also to this load DUT. Control is executed to increase the output voltage Vo output from the output terminal so as to match the input voltage Vi (normally, the same voltage as the reference voltage Vr).

However, when an output current Io of 1 mA can be supplied to a load DUT of 30 kΩ, the absolute value of the output voltage Vo is 30.1 V (=30 kΩ×1 mA+0.1 V). exceeds 28 V, which is the absolute value of the limit voltage value. Therefore, in the current supply circuit 1A, the operational amplifier 4 increases its output voltage Vo in the positive voltage region in response to the input voltage Vi (the same voltage as the reference voltage Vr) that increases in the positive voltage region. In this state, the voltage value of the output voltage Vo reaches 28 V before the input voltage Vi (reference voltage Vr) reaches the positive peak. Also, the first divided voltage V1a output from the first resistor voltage dividing unit 6a reaches +2.8 V, that is, the positive side set voltage V2a set in the set voltage source 22a.

In this way, from the point in time when the voltage value of the increasing output voltage Vo reaches 28 V (for example, time t1 in FIG. 2) before the input voltage Vi (reference voltage Vr) reaches the positive peak, the input voltage Vi Assuming that (the reference voltage Vr) is not subject to the voltage limitation by the voltage limiting section 7a, the output voltage Vo decreases after passing the positive side peak as indicated by the dashed line in FIG. During the period until the voltage value drops to 28 V (for example, time t2 in FIG. 2) (the period during which the absolute value of the first divided voltage V1a exceeds the absolute value of the positive set voltage V2a), the operational amplifier 4 and The voltage limiter 7a operates as follows to limit the output voltage Vo to a predetermined voltage Vsa (+28 V in this example) as shown in FIG.

When the output voltage Vo from the operational amplifier 4 rises to reach +28 V and slightly exceeds +28 V immediately after that, the voltage limiter 7a outputs from the first resistance voltage divider 6a to the inverting input terminal of the comparator 21a. The first divided voltage V1a that is applied exceeds the positive side set voltage V2a (+2.8 V) that is output from the set voltage source 22a to the non-inverting input terminal of the comparator 21a. Therefore, the comparator 21a changes the voltage (output voltage) of its output terminal (the terminal to which the cathode terminal of the diode 23a is connected) from a positive voltage substantially equivalent to its positive operating voltage to its negative operating voltage. to a negative voltage approximately equal to .

In this case, since the voltage of the anode terminal of the diode 23a is the positive input voltage Vi (reference voltage Vr), when the voltage of the output terminal of the comparator 21a becomes the negative voltage, Diode 23a transitions from a non-conducting state to a conducting state. As a result, the input voltage Vi is forcibly lowered by the comparator 21a through the conductive diode 23a. At this time, the operational amplifier 4 reduces its output voltage Vo so that the detection voltage Vd input to the inverting input terminal matches the decreasing input voltage Vi.

After that, when the output voltage Vo drops slightly below +28 V, the voltage limiter 7a detects the first divided voltage V1a output from the first resistance voltage divider 6a to the inverting input terminal of the comparator 21a. is lower than the positive set voltage V2a (+2.8 V) output from the set voltage source 22a to the non-inverting input terminal of the comparator 21a. Therefore, the comparator 21a again raises the voltage (output voltage) of its output terminal (the terminal to which the cathode terminal of the diode 23a is connected) toward a positive voltage substantially equal to its positive operating voltage. .

In this case, the voltage at the anode terminal of the diode 23a is the positive input voltage Vi (reference voltage Vr), but its value (absolute value less than 1 V) is the positive operating voltage of the comparator 21a ( +15 V), the voltage at the cathode terminal of diode 23a will briefly exceed the voltage at the anode terminal and diode 23a will transition from a conducting state to a non-conducting state. As a result, the input voltage Vi rises to the same voltage as the reference voltage Vr. At this time, the operational amplifier 4 increases its output voltage Vo in order to match the rising input voltage Vi with the detection voltage Vd input to the inverting input terminal. This causes the rising output voltage Vo to reach +28V again.

After that, the input voltage Vi (reference voltage Vr) passes the positive side peak and decreases, and the positive output voltage Vo output by the operational amplifier 4 based on this input voltage Vi also falls below the positive side predetermined voltage Vsa. The operational amplifier 4 and the voltage limiter 7a repeat this operation until the output voltage Vo is continuously limited to the predetermined voltage Vsa (+28 V in this example).

Further, the current supply circuit 1A operates after the output voltage Vo of the positive voltage output from the operational amplifier 4 based on the input voltage Vi becomes lower than the predetermined voltage Vsa on the positive side. Until the voltage value of the output voltage Vo reaches -28 V in the voltage region of , the load DUT is not subjected to voltage limitation by the voltage limiting units 7a and 7b, similarly to when the load DUT is normal. The voltage value of the output voltage Vo is changed according to the resistance value Rx of the DUT, and the output current Io is supplied to the load DUT at a specified current value (1 mA).

In the current supply circuit 1A, the operational amplifier 4 reduces the output voltage Vo in the negative voltage region in response to the input voltage Vi (same voltage as the reference voltage Vr) that decreases in the negative voltage region. In this state, the voltage value of the output voltage Vo reaches -28V before the input voltage Vi (reference voltage Vr) reaches its negative peak. Also, the first divided voltage V1b output from the first resistor voltage dividing unit 6b reaches -2.8V, that is, the negative side set voltage V2b set in the set voltage source 22b.

In this way, before the input voltage Vi (reference voltage Vr) reaches the negative peak, the voltage value of the decreasing output voltage Vo reaches −28 V (for example, time t3 in FIG. 2). Assuming that Vi (reference voltage Vr) is not subject to voltage limitation by the voltage limiting section 7b, the output voltage Vo increases past the negative side peak as indicated by the dashed line in FIG. rises to −28 V (for example, time t4 in FIG. 2) (the period in which the absolute value of the first divided voltage V1b exceeds the absolute value of the negative set voltage V2b), the operational amplifier 4 and the voltage limiter 7b operate as follows to limit the output voltage Vo to a predetermined voltage Vsb (-28V in this example) as shown in FIG.

When the output voltage Vo from the operational amplifier 4 decreases to reach -28 V and immediately after that falls slightly below -28 V, the voltage limiter 7b switches the voltage from the first resistor voltage divider 6b to the inverting input terminal of the comparator 21b. The output first divided voltage V1b falls below the negative set voltage V2b (-2.8 V) output from the set voltage source 22b to the non-inverting input terminal of the comparator 21b. Therefore, the comparator 21b changes the voltage (output voltage) of its output terminal (the terminal to which the anode terminal of the diode 23b is connected) from a negative voltage substantially equivalent to its negative operating voltage to its positive operating voltage. to a positive voltage approximately equal to .

In this case, since the voltage at the anode terminal of the diode 23b is the negative input voltage Vi (reference voltage Vr), when the voltage at the output terminal of the comparator 21b becomes a positive voltage, Diode 23b transitions from a non-conducting state to a conducting state. As a result, the input voltage Vi is forcibly increased by the comparator 21b through the conductive diode 23b. At this time, the operational amplifier 4 increases its output voltage Vo in order to match the rising input voltage Vi with the detection voltage Vd input to the inverting input terminal.

After that, when the output voltage Vo slightly exceeds -28 V, the voltage limiter 7b detects the first divided voltage output from the first resistance voltage divider 6b to the inverting input terminal of the comparator 21b. V1b exceeds the negative set voltage V2b (-2.8 V) output from the set voltage source 22b to the non-inverting input terminal of the comparator 21b. Therefore, the comparator 21b again reduces the voltage (output voltage) of its output terminal (the terminal to which the anode terminal of the diode 23b is connected) toward a negative voltage substantially equal to its negative operating voltage. .

In this case, the voltage at the cathode terminal of the diode 23b is the input voltage Vi (reference voltage Vr) which is a negative voltage, but its value (absolute value less than 1 V) is the negative operating voltage of the comparator 21b ( −15 V), the voltage at the anode terminal of diode 23b falls below the voltage at the cathode terminal for a short time, and diode 23b transitions from the conducting state to the non-conducting state. As a result, the input voltage Vi drops to the same voltage as the reference voltage Vr. At this time, the operational amplifier 4 reduces its output voltage Vo so that the detection voltage Vd input to the inverting input terminal matches the decreasing input voltage Vi. As a result, the decreasing output voltage Vo reaches -28V again.

Thereafter, the input voltage Vi (reference voltage Vr) rises past the negative peak, and the negative output voltage Vo output from the operational amplifier 4 based on this input voltage Vi also exceeds the predetermined negative voltage Vsb. The operational amplifier 4 and the voltage limiter 7b repeat this operation until the output voltage Vo is continuously limited to the predetermined voltage Vsb (-28 V in this example).

Further, the current supply circuit 1A operates after the negative output voltage Vo output by the operational amplifier 4 based on the input voltage Vi exceeds the predetermined negative voltage Vsa, as described above. Until the voltage value of the output voltage Vo reaches +28 V in the voltage region of , the load DUT is not subjected to voltage limits by the voltage limiters 7a and 7b, similarly to when the load DUT is normal. The voltage value of the output voltage Vo is changed according to the resistance value Rx of , and the output current Io is supplied to the load DUT at a specified current value (1 mA).

Thus, according to the current supply circuit 1A and the resistance measuring device 50A including the current supply circuit 1A, the output portion 4c (the output terminal of the operational amplifier 4) of the amplifier portion 4 constituting the current supply circuit 1A and the By applying the applied voltage Vap to the load DUT connected between the circuit ground G, the output current Io can be supplied to the load DUT, and the output voltage Vo is reduced to the first divided voltage V1a, which is a low voltage. By providing the first resistor voltage dividing unit 6 (6a, 6b) that divides the voltage into V1b and outputs it to the voltage limiting unit 7 (7a, 7b), the voltage limiting unit 7 (7a, 7b) is made of a low-voltage specification semiconductor. The comparators 21a and 21b of low voltage specification can be used as components, thereby avoiding the use of high voltage specification semiconductor components (high voltage specification operational amplifiers, comparators, etc.).

Further, according to the current supply circuit 1A and the resistance measuring device 50A equipped with the current supply circuit 1A, the voltage between the second terminal TM2 (load connection terminal 8b) on the circuit ground G side of the load DUT and the circuit ground G , the amplifier unit 4 has a non-inverting input terminal as an input unit 4a to which the input voltage Vi is input, and an inverting input terminal to By providing the operational amplifier 4 to which the detection voltage Vd is input and whose output terminal is connected to the output section 4c (the output terminal functions as the output section 4c), the voltage limiting section 7 (7a, 7b) can The output current Io can be supplied to the load DUT as an accurate constant current while avoiding the use of voltage specification semiconductor components (such as high voltage specification operational amplifiers and comparators). Further, according to this resistance measuring device 50, the resistance value Rx of the load DUT can be measured with sufficient accuracy.

The current supply circuit 1A described above employs a configuration in which the detection resistor section 5 is connected between the circuit ground G and the second terminal TM2 (load connection terminal 8b) on the circuit ground G side of the load DUT. , but not limited to this configuration. For example, like the current supply circuit 1B shown in FIG. A configuration in which the second terminal TM2 (load connection terminal 8b) of is connected to the circuit ground G can also be adopted. The current supply circuit 1B and the resistance measuring device 50B equipped with the current supply circuit 1B will be described below. The same components as those of the current supply circuit 1A and the resistance measuring device 50A are denoted by the same reference numerals, and overlapping descriptions are omitted. In addition, overlapping descriptions of operations similar to those of the resistance measuring device 50A will be omitted.

First, the configuration of the current supply circuit 1B will be described with reference to FIG.

The current supply circuit 1B includes a voltage input terminal 2, an input resistor 3, an amplifier 4, a detection resistor 5, a first resistor voltage divider 6 (6a, 6b, 6c), a voltage limiter 7 (7a, 7b), a load Equipped with connection terminals 8a and 8b, a second resistance voltage dividing unit 31, and a differential amplifier unit 32, the reference voltage Vr input to the voltage input terminal 2 is amplified by the amplifier unit 4 and applied between the load connection terminals 8a and 8b. By applying an applied voltage Vap (a voltage across the load DUT) to the load DUT connected to the load DUT, an output current Io, which is a constant current, can be supplied to the load DUT.

In this current supply circuit 1B, as described above, the detection resistor section 5 is connected between the output section 4c of the amplifier section 4 and the first terminal TM1 (which is also the load connection terminal 8a) of the load DUT. Further, as the first resistance voltage dividing portion 6, in addition to the first resistance voltage dividing portions 6a and 6b in the current supply circuit 1A, a first resistance voltage dividing portion 6c is provided.

The first resistor voltage dividing unit 6c is composed of two series-connected resistors 11c and 12c in the same manner as the first resistor voltage dividing units 6a and 6b, and outputs a first divided voltage V1c. In this current supply circuit 1B, since the load connection terminal 8b to which the second terminal TM2 of the load DUT is connected is connected to the circuit ground G, each of the first resistor voltage dividers as the first resistor voltage divider 6 6a, 6b, and 6c divide the applied voltage Vap according to their respective voltage division ratios, and output first divided voltages V1a, V1b, and V1c.

In the first resistor voltage dividing unit 6c, when the resistance value of the resistor 11c connected to the load connection terminal 8a is R5 and the resistance value of the resistor 12c connected to the circuit ground G is R6, R6/( Each resistance value R5, R6 (for example, a resistance value of several tens of kΩ to several hundreds of kΩ where R5>R6) is defined so that the voltage division ratio represented by R5+R6) becomes, for example, one-tenth. . With this configuration, the first resistive voltage dividing portion 6c, like the first resistive voltage dividing portions 6a and 6b, even when the output voltage Vo and the applied voltage Vap are high voltages, the first divided voltage V1c can be output as a low voltage that matches the input specifications of a low-voltage specification operational amplifier or comparator (a general operational amplifier such as that used in the differential amplifier 32). As for the first resistance voltage dividing portion 6c, by matching the voltage division ratio to that of the first resistance voltage dividing portion 6 of the first resistance voltage dividing portions 6a and 6b, one of the first resistance voltage dividing portions 6a and 6b The resistive voltage dividing unit 6 may also be used. Further, the first resistor voltage dividers 6a, 6b, and 6c may be combined into one first resistor voltage divider 6 by aligning the voltage division ratios of the first resistor voltage dividers 6a, 6b, and 6c.

The second resistor voltage divider 31 is composed of two series-connected resistors 13 and 14, and is connected between the output 4c of the second amplifier 4 (in this example, the output terminal of the operational amplifier 4) and the circuit ground G. , and divides the output voltage Vo at a predetermined voltage dividing ratio (the same voltage dividing ratio as the first resistor voltage dividing unit 6c) to output a second divided voltage V3. In the second resistor voltage dividing unit 31, when the resistance value of the resistor 13 connected to the output unit 4c is R7 and the resistance value of the resistor 14 connected to the circuit ground G is R8, R8/(R7+R8 ) is the same as that of the first resistor voltage dividing portion 6c, the resistance values R7 and R8 (for example, resistance values of several tens of kΩ to several hundreds of kΩ where R7>R8) are stipulated. With this configuration, the second resistive voltage dividing unit 31 reduces the second divided voltage V3 even when the output voltage Vo is high in the same manner as the first resistive voltage dividing units 6a, 6b, and 6c. It is possible to output a low voltage that matches the input specifications of a voltage specification operational amplifier (a general operational amplifier such as that used in the differential amplifier 32). Further, since the voltage division ratios of the first resistance voltage dividing portion 6c and the second resistance voltage dividing portion 31 are the same in this manner, the difference voltage between the second divided voltage V3 and the first divided voltage V1c is , is proportional to the voltage generated across the detection resistor 5 due to the flow of the output current Io.

The differential amplifier 32 is configured by, for example, a low-voltage operational amplifier 32a arranged in the input stage, and the second divided voltage V3 input to the non-inverting input terminal of the operational amplifier 32a and the inverting input A voltage difference from the first divided voltage V1c input to the terminal is amplified by a predetermined amplification factor and output as a detection voltage Vd to the input section 4b. That is, in the current supply circuit 1B, the first resistive voltage dividing unit 6c, the second resistive voltage dividing unit 31, and the differential amplifier unit 32 together with the detection resistor unit 5 convert the output current Io flowing through the load DUT to the detection voltage. It is converted to Vd and output to the inverting input terminal of the operational amplifier 4 as the input section 4b.

Also in this resistance measuring device 50B, the measuring unit 51 operates in the same manner as in the resistance measuring device 50A, measures the output current Io based on the detected voltage Vd, measures the applied voltage Vap, and measures the measured applied voltage. By dividing the voltage Vap by the measured output current Io, the resistance value Rx of the load DUT is measured and output to the output section 52 . Further, the output unit 52 displays (outputs) the resistance value Rx output from the measurement unit 51 on the screen. Thereby, the resistance value Rx of the load DUT connected between the load connection terminals 8a and 8b is measured. In the resistance measuring device 50B, since the first resistance voltage dividing portions 6a, 6b, 6c are connected between the load connection terminal 8a and the circuit ground G, the first resistance voltage dividing portions 6a, 6b , 6c are connected in parallel with the load DUT. Therefore, the output current Io measured based on the detected voltage Vd includes not only the current flowing through the load DUT but also the current flowing through the first resistance voltage dividing units 6a, 6b, and 6c. By sufficiently increasing the series resistance value of each resistor constituting the first resistor voltage dividing units 6a, 6b, and 6c with respect to the value Rx, the output current Io is supplied to the load DUT in a substantially constant current state. Therefore, it is possible to measure the resistance value Rx with the required accuracy.

Thus, in the current supply circuit 1B and the resistance measuring device 50A as well, the current supply circuit 1B is connected between the output part 4c (the output terminal of the operational amplifier 4) of the amplifier 4 and the circuit ground G. By applying the applied voltage Vap to the load DUT, the output current Io can be supplied to the load DUT in a state close to a constant current, while the output voltage Vo and the applied voltage Vap are reduced to the second divided voltage V3 which is a low voltage. and the second resistor voltage dividing unit 31 and the first resistor voltage dividing unit 6 (6a , 6b, 6c), the differential amplifier 32 and the voltage limiter 7 (7a, 7b) are composed of the low voltage specification operational amplifier 32a and the comparators 21a, 21b as low voltage specification semiconductor components. can be obtained, thereby avoiding the use of high-voltage semiconductor components (such as high-voltage operational amplifiers and comparators).

1A, 1B current supply circuit
3 Input resistance
4 amplification section 4a input section 4c output section
5 resistance detection unit 6a, 6b, 6c first resistance voltage dividing unit 7a, 7b voltage limiting unit 31 second resistance voltage dividing unit 32 differential amplifier unit 50A, 50B resistance measurement device 51 measurement unit DUT load
G Circuit ground Io Output current TM1 First terminal TM2 Second terminal V1a, V1b, V1c First divided voltage V2a, V2b Set voltage V3 Second divided voltage Vap Applied voltage Vd Detected voltage Vi Input voltage Vo Output voltage

Claims (4)

Amplifies the input voltage referenced to the circuit ground that is input to the input through the input resistor, and outputs the output voltage for applying the applied voltage to the load connected between the output and the circuit ground. A current supply circuit that has an amplifier unit that outputs from the output unit and supplies an output current to the load,
A first voltage dividing resistor connected between a first terminal on the output side of the load and the circuit ground, for dividing the applied voltage by a predetermined voltage dividing ratio and outputting a first divided voltage. Department and
A voltage limiter that inputs the first divided voltage, compares it with a set voltage, and reduces the absolute value of the input voltage when the absolute value of the first divided voltage exceeds the absolute value of the set voltage. and a current supply circuit. a detection resistor connected between a second terminal of the load on the circuit ground side and the circuit ground for converting the output current into a detection voltage and outputting the detection voltage;
The amplifier section includes an operational amplifier having a non-inverting input terminal as the input section to which the input voltage is input, an inverting input terminal to which the detected voltage is input, and an output terminal connected to the output section. 2. A current supply circuit according to claim 1. a detection resistor unit connected between the output unit and the first terminal of the load for converting the output current into a detection voltage and outputting the detection voltage;
a second divided voltage connected between the output section and the circuit ground, wherein the amplifying section amplifies the input voltage and divides the output voltage output from the output section by a predetermined voltage division ratio; a second resistor voltage dividing unit that outputs
a differential amplifier that receives the first divided voltage and the second divided voltage, amplifies a difference voltage between the two divided voltages, and outputs the detected voltage as a detection voltage;
The amplifier section includes an operational amplifier having a non-inverting input terminal as the input section to which the input voltage is input, an inverting input terminal to which the detected voltage is input, and an output terminal connected to the output section. 2. A current supply circuit according to claim 1. The current supply circuit according to any one of claims 1 to 3, and measuring the voltage value of the applied voltage and the current value of the output current, and the resistance value of the load based on the measured voltage value and current value A resistance measuring device comprising a measuring unit for measuring

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