JP2003069386A - Electrical variable generating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrical variable generating apparatus that realizes generation of standard DC/AC voltage/current by utilizing components of an equivalent resistance generating apparatus in common for generating an equivalent resistance with high precision. SOLUTION: The electrical variable generating apparatus for generating electrically an equivalent resistance when applying voltage or current between output terminals is characterized in that the electric variable generating apparatus includes a circuit for converting current flowing to one of the output terminals into voltage, a gain variable multiplication type digital/analog converter, an output control circuit that receives an output voltage of the gain variable multiplication type digital/analog converter and feeds back voltage at the other of the output terminals to an error amplifier so as to control the voltage at the output terminal, and an equivalent resistance generating device that includes transistors and controls emitter levels of the transistors with an output of an operational amplifier in the case of controlling an output voltage in excess of a range supplied by the operational amplifier so as to control a voltage drop between the collectors and emitters of the transistors.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric quantity generating device capable of generating equivalent resistance and electric quantities such as voltage and current at arbitrary values.

[0002]

2. Description of the Related Art Japanese Patent No. 31064 discloses a device for generating a quantity of electricity such as voltage, current and equivalent resistance.
The contents are disclosed in Japanese Patent Publication No. 59. The disclosure content is the main configuration of the device for generating standard voltage / current for calibrating a measuring instrument that measures voltage, current or thermocouple output, and for generating an equivalent resistance for calibrating an ohmmeter. The elements are standardized and integrated.

[0003]

However, in the case of the method according to the invention described in Japanese Patent No. 3106459,
Equivalently creating a resistance between output terminals is to create a desired equivalent resistance by generating a voltage according to a virtual resistance when a current source is applied between the terminals. It was difficult to pass a current according to the desired equivalent resistance. Further, in the case of generating a high resistance or applying a high voltage source, in the existing method, an amplifier capable of generating a high voltage is required in the output circuit. Further, in order to output a high voltage, a power supply for operating a high voltage amplifier is naturally required.

On the other hand, in the case of an ordinary resistor, the power is supplied from the outside, so that the resistor itself does not need to have its own power source, and it is necessary to realize a system as close to this situation as possible. Further, it has been difficult for the conventional equivalent resistance generator to handle an AC signal.

The present invention has been made in view of the above circumstances, and can be realized even when a high resistance is generated or a high voltage is applied without preparing a corresponding high voltage power supply, and can also correspond to an AC signal. (EN) Provided is an electric quantity generation device which can realize a resistance generation device with a simple configuration and which can be switched to a voltage or current generation device by using the above circuit by adding a switching circuit and some circuits. The purpose is to

[0006]

In order to achieve the above object, the invention according to claim 1 provides an output according to a current flowing into the output terminal when a voltage or a current is applied between the output terminals. A circuit for converting a current flowing into one of the output terminals into a voltage in a quantity-of-electricity generating device that generates a voltage drop corresponding to a desired resistance value between the terminals to generate an electronically equivalent resistance; Of the multiplication type D-A converter whose gain is variable by setting a digital value corresponding to the resistance value of, and the output voltage of the multiplication type D-A converter as an input, An output control circuit for controlling the voltage of the output terminal by feeding back the voltage to the error amplifier directly or via a voltage divider, and O constituting the error amplifier.
An emitter amplifier is connected to the output terminal of the P amplifier, a base electrode is connected to a constant voltage source in the forward direction via a resistor, and a collector is connected to the output terminal via a diode. In controlling an output voltage that exceeds the range that can be supplied by, an equivalent resistance generating mechanism that controls the emitter potential of the transistor by the output of the OP amplifier to control the voltage drop between the collector and the emitter of the transistor is characterized. .

Therefore, according to the invention described in claim 1,
Since the emitter potential of the transistor is controlled, the applied voltage V increases and the output voltage (Vo) to be controlled is + V.
When the voltage exceeds Vs, the constant voltage V + is supplied to the base electrode. Therefore, when the voltage Va increases, the base current of the transistor decreases, and the transistor enters the control region from the saturation region, causing a voltage drop. Output voltage V
It becomes possible to control o.

The invention described in claim 2 is the same as claim 1.
In addition to the configuration described in (1) above, an NPN-type transistor and a PNP-type transistor are connected in parallel as a control element by the transistor, and a diode is connected to each transistor.

Therefore, according to the invention described in claim 2,
Since the NPN type transistor and the PNP type transistor are connected in parallel, it is possible to deal with both positive and negative polarities of the applied voltage. Also, by connecting a diode to each transistor, current blocking for the reverse voltage can be achieved. It is possible to do.

Further, in the invention described in claim 3, in addition to the structure described in claim 1, the input of the multiplying DA converter is set to a constant reference voltage, and the collector electrode of the transistor of the output control circuit is set. And a standard voltage generation mechanism for inserting a DC power supply between the output terminals and controlling the voltage between the output terminals to a desired value, and switching the equivalent resistance generation mechanism and the standard voltage generation mechanism. It is characterized by enabling the function switching by.

Therefore, according to the invention of claim 3,
By realizing the standard voltage generating device by using the multiplication type D / A converter and the output control circuit of the equivalent resistance generating device according to claim 1, commonalization of the constituent elements can be achieved, and By using the switching circuit, it becomes possible to easily realize the function switching from the standard voltage generator to the equivalent resistance generator.

The invention according to claim 4 is the same as claim 3
In addition to the configuration described in (1), a standard current generating mechanism that converts a current flowing through the output terminal into a voltage with a shunt resistance and controls the output current so as to be equal to the output of the multiplying DA converter is provided. Characterize.

Therefore, according to the invention of claim 4,
If a shunt resistor is provided between the output terminal and the circuit common and the voltage proportional to the current is fed back to control the output,
A constant current output corresponding to the k setting can be obtained, and the multiplication type D
It becomes possible to make the output current equal to the output of the −A converter.

Further, in the invention described in claim 5, in addition to the configuration described in claim 2 or 3, the reference voltage is a sine wave reference voltage of constant amplitude with alternating current, and the collector of the transistor and the output terminal are connected. It is characterized in that the power source applied during the period is a power source having the same frequency and the same phase as the sine wave reference voltage and capable of generating a variable voltage current having an arbitrary value of alternating current from the output terminal.

Therefore, according to the invention described in claim 5,
Since the reference voltage is an AC sine wave reference voltage and the power supply applied between the collector of the transistor and the output terminal is the same AC power supply as the sine wave reference voltage, it is possible to realize an AC variable voltage current. .

The invention according to claim 6 is the same as claim 3
In addition to the configuration according to any one of 5 to 5, the value of the insertion power supply required for generating the output voltage is set to a substantially desired voltage value in the standard voltage generating mechanism, and the load voltage is used in the standard current generating mechanism. It is characterized in that a second control circuit that is changed according to the above is also used.

Therefore, according to the invention of claim 6,
By providing the second control circuit that changes the value of the insertion power source according to the standard voltage generation mechanism and the standard current generation mechanism, it is possible to suppress the voltage drop of the transistor and reduce the voltage control loss.

Further, the invention according to claim 7 is characterized in that, in addition to the structure according to any one of claims 1 to 6, a field effect transistor is used for the voltage drop element for the output control.

Therefore, according to the invention of claim 7,
As a transistor as a voltage drop element, MOSFE
It is possible to use a field effect transistor such as T.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of a circuit of an electric quantity generating device according to an embodiment of the present invention. Terminal 71,
An AC power supply is provided between 72. A current / voltage conversion circuit 20 for converting a current into a voltage is connected to the terminal 72, and the current / voltage conversion circuit 20 is connected to the multiplication type DA converter 30. This multiplication type DA
The converter 30 has a function of changing the gain (GAIN) by setting a digital value corresponding to a predetermined resistance value.

The multiplication DA converter 30 is connected to an output control OP amplifier (error amplifier) 41. A voltage divider 42 is connected to one input terminal of an output control OP amplifier (error amplifier) 41, and the voltage divider 42 has a function of dividing a voltage. As shown by reference numeral 50, an NPN transistor and a PNP transistor are connected in parallel to the output terminal of the output control OP amplifier (error amplifier) 41.

Next, the equivalent resistance generating operation will be described with reference to FIG. When the voltage V is applied between the output terminals 71 and 72, the current I flows. The current I is converted into the voltage V1 by the current / voltage conversion circuit 20, and the multiplication type DA converter 30 is used.
Add to. The multiplication DA converter 30 sets GAIN to k in accordance with the desired generated resistance value setting. Multiplication type D-
The output of the A converter 30 is applied to an output control circuit OP amplifier (error amplifier) 41, and the other input terminal of the error amplifier 41 divides the voltage of the output terminal 71 into 1 / N via a voltage divider 42. It is pressed and returned. The error amplifier 41 controls the output so that the value of 1 / N of the output terminal voltage becomes equal to the input voltage, that is, the output voltage of the multiplication DA converter 30.
That is, when V1 and Vo are expressed by equations, they become equations (1) and (2).

V1 = I * Rs (1)

[0024] V0 = V1 * k * N = I * Rs * k * N (2)

On the other hand, when a voltage V is applied between the terminals, V is expressed by the following equation (3).

[0026] V = V0 + I * R0 = (I * Rs * k * N) + I * R0 = I (Rs * k * N + R0) (3)

Since the equivalent resistance Req is Req = V / I, Req is given by the following equation (4).

[0028] Req = (Rs * k * N) + R0 (4)

The same applies when the constant current source I is applied between the output terminals 71 and 72.

By the way, the output voltage Vo is determined by the error amplifier 41.
Output voltage Va is controlled, but when the power supply voltage of the OP amplifier used for the error amplifier 41 is + Vs and −Vs, the output voltage cannot be larger than ± Vs.
~ 2V less range). According to the conventional method, when the applied voltage V is large, it is necessary to control the output voltage accordingly. The present invention shown in FIG. 1 does not control the voltage of the output terminal only by the output of the amplifier, but performs the SINK (suction) operation of the current by controlling the Vce of the transistor,
This is a control method that combines the control of the output voltage of a normal amplifier.

The base electrode of the NPN transistor Q1 is connected through a resistor to a constant voltage V + in the forward direction, which is slightly lower than the maximum voltage that can be generated by the OP amplifier. For example, when the maximum amplitude of the OP amplifier is ± 13V, V + is about +1
Set to 0V. In this way, the applied voltage V is low and V
When o is controlled within approximately V +, the transistor is turned on (saturation region), Q1 is simply conductive, and the output voltage is controlled by the OP amplifier output. As described above, Vo is expressed by the following equation (5).

V0 = I * Rs * k * N (5)

Alternatively, it can be expressed as in equation (6).

[0034] V0 = V * (Rs / Req) * k * N (6)

However, when the applied voltage V increases and Vo to be controlled exceeds + Vs, the constant voltage V + is supplied to the base electrode. Therefore, when Va increases, the base current of the transistor decreases. The transistor enters the control region from the saturation region and causes a voltage drop to control the output voltage Vo. FIG. 2 shows the state of the voltage of each part according to the applied voltage V. 2A shows an enlarged view of the NPN-type transistor and the PNP-type transistor, and FIG. 2B shows a state in which the voltage of each part changes according to the applied voltage V. Since the present invention is configured to control the emitter electrode, the above-described operation is possible.

In order to make the applied voltage positive or negative, an NPN type transistor and a PNP type transistor are connected in parallel as indicated by the reference numeral. The diode is for blocking current in the opposite direction. Since the gain of the error amplifier (OP amplifier) 41 is sufficiently large (usually 120 dB or more for a DC signal), the forward voltage drop of the diode and the forward saturation voltage of the transistor are equivalent to the input conversion value of the control system. There is no error when viewed with.

As described above, according to the present invention, the OP amplifier directly controls the output with respect to a low voltage, and when the voltage becomes high, the transistor absorbs the voltage (becomes a voltage drop element) and the device itself. It is possible to generate resistance equivalently for any voltage without incorporating a high-voltage power supply. Since the low-level output control centered on zero is directly controlled by the output of the OP amplifier, it is possible to continuously control the positive / negative voltage centered on zero.

FIG. 3 shows a block diagram of a system which can be realized by switching the above-mentioned equivalent resistance generating function and arbitrary standard variable voltage generating function. Between the output terminals 71, 72 and the current / voltage conversion circuit 20 and the multiplication type D / A converter 30, a changeover switch 80 (interlocked individual switches 81, 8
2, 83). When the switch 80 is switched to the a side, the function of the equivalent resistance generator shown in FIG. 1 is obtained. Then, when the switch 80 is switched to the b side, it becomes a voltage generating function.

Vref connected to the b side of the individual switch 81 provided between the current / voltage conversion circuit 20 and the multiplication DA converter 30 is a reference power source and is provided at the output terminal 71. Vc connected to the b side of the switch 83 is a voltage source required when a high voltage is generated. Vc is approximately equal to or higher than the desired output voltage. The operation when the voltage generating function is selected is as follows.

The multiplying DA converter 30 generates a desired variable voltage as a reference voltage, which serves as a reference input to the output control section. Due to the feedback action, the output voltage Vo is Vo = Vref * k * N
However, when the output voltage Vo is within ± Vs, Q1,
Or the circuit of Q2 is turned on and the output of the OP amplifier is Vo.
Is controlled. If it is desired to control Vo beyond the voltage that can be generated by the OP amplifier, Vc is added. Vc is Vo ± V
It may be s or more. When the voltage drop between the collector C and emitter E of Q1 or Q2 including the voltage drop in the forward direction of the diode is Vce, Vo = Va + Vce is controlled.

If the reference voltage Vref is an AC sine wave reference voltage and Vc is an AC power supply whose phase matches Vref, the variable voltage generating function of the AC voltage can be realized by the same operation as described for DC.

Although not shown in particular, instead of the feedback loop from the Vo terminal by the voltage divider 42 of the voltage generating circuit, a shunt resistor is inserted between the terminal 72 and the circuit common, and a voltage proportional to the current is fed back to output. If controlled, k
The constant current output according to the setting can be obtained. That is,
When the output current is Io and the shunt resistor is Rsh, Io can be obtained by the following equation (7) (current generation function).

[0043] I0 = (Vref * k) / Rsh (7)

[0044]

According to the present invention, the function and use of high-precision equivalent resistance generation can be applied not only to the use for calibrating a conventional resistance meter, but also to a wider range of voltage / current and AC signals. It can be used for more general purpose. In addition, by using the components of this equivalent resistance generator in common, it is possible to generate standard voltages and currents of DC and AC.
It is possible to realize a device that is compact and inexpensive and that generates the above-mentioned various kinds of electricity.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit having an equivalent resistance generating function of an electricity quantity generating device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a voltage state of each part according to an applied voltage V. (A) is a partial view of the NPN type transistor and the PNP type transistor shown in FIG. 1. (B) is a graph showing the state of the voltage change of each part according to the applied voltage V.

FIG. 3 is a block diagram showing a circuit for switching and realizing an equivalent resistance generating function and an arbitrary standard variable voltage generating function of the electricity quantity generating device according to the embodiment of the present invention.

[Explanation of symbols]

20 Current / Voltage Conversion Circuit 30 Multiplying DA Converter 41 Output Control Circuit OP Amplifier (Error Amplifier) 42 Voltage Divider 71, 72 Output Terminal 80 Changeover Switch 81, 82, 83 Individual Switch

Claims (7)

[Claims] 1. When a voltage or a current is applied between the output terminals, a voltage drop corresponding to a desired resistance value is generated between the output terminals according to the current flowing into the output terminals, and an electronically equivalent voltage drop is generated. In an electric quantity generating device for generating a resistance, a circuit for converting a current flowing into one of the output terminals into a voltage, and a multiplication type DA for varying a gain by setting a digital value corresponding to a desired resistance value. A converter and an output voltage of the multiplying DA converter are input, and the voltage of the other terminal of the output terminals is fed back to the error amplifier directly or via a voltage divider to output the voltage of the output terminal. An output control circuit for controlling and an output terminal of the OP amplifier constituting the error amplifier are connected to an emitter electrode, a base electrode is connected via a resistor to a constant voltage source in the forward direction, and a collector is connected via a diode to the front side. In order to control the output voltage exceeding the range that can be supplied by the OP amplifier, the transistor connected to the output terminal controls the emitter potential of the transistor by the output of the OP amplifier, and the voltage drop between the collector and the emitter of the transistor. An electric quantity generating device having an equivalent resistance generating mechanism for controlling the electric quantity. 2. A control element comprising the transistor,
The electricity quantity generating device according to claim 1, wherein an NPN transistor and a PNP transistor are connected in parallel, and a diode is connected to each transistor. 3. The input of the multiplying DA converter is set to a constant reference voltage, a DC power source is inserted between the collector electrode of the transistor of the output control circuit and the output terminal, and the voltage between the output terminals is adjusted. The electrical equipment according to claim 1, further comprising a standard voltage generating mechanism controlled to a desired value, wherein the equivalent resistance generating mechanism and the standard voltage generating mechanism can be switched in function by a switching circuit. Quantity generator. 4. A standard current generating mechanism for converting a current flowing through the output terminal into a voltage by a shunt resistor and controlling the output current so as to be equal to the output of the multiplying DA converter. The electric quantity generator according to claim 3. 5. A power supply applied between the collector of the transistor and the output terminal as a sine wave reference voltage having a constant amplitude with an alternating current, and a power supply having the same frequency and the same phase as the sine wave reference voltage. 4. The electric quantity generating device according to claim 2, wherein a variable voltage current having an arbitrary value of alternating current can be generated as the output terminal. 6. The value of the insertion power supply required for generating the output voltage is changed to a substantially desired voltage value in the standard voltage generating mechanism, and is changed in accordance with the load voltage in the standard current generating mechanism. 6. The electricity quantity generating device according to claim 3, wherein the second control circuit according to claim 5 is used in combination. 7. A field effect transistor is used as the voltage drop element for controlling the output.
The electric quantity generator according to any one of 1.