JPH089776Y2 - Voltage generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a voltage generator capable of generating a standard voltage of an arbitrary value according to a set value, and in particular, an improved zero-point adjusting means. Is.

[Conventional technology]

In a generator of this kind, each circuit is usually constructed using an operational amplifier, but the operational amplifier has an offset component. If this offset is not compensated for by any means, the zero point fluctuates and an error occurs, so that the voltage cannot be generated with high accuracy.

[Problems to be solved by the invention]

SUMMARY OF THE INVENTION The present invention is intended to solve such a problem and to obtain a generator having a zero point adjusted and capable of generating a standard voltage with high accuracy by a simple configuration.

[Means for solving problems]

In order to achieve the above-mentioned object, the present invention comprises a reference voltage generating circuit VS configured to use an operational amplifier to generate a variable reference voltage according to a set value, H and L terminals to which a load is connected, and a reference voltage. The output terminal of the generating circuit VS is connected to one input terminal, the output terminal is connected to the H terminal through the regulator RG, and the voltage corresponding to the output voltage generated between the H and L terminals is applied to the other input terminal. An error amplifier composed of an operational amplifier A1 to be added, and a pair of Zener diodes connected to its output terminal and a variable resistor at one input terminal
It has a zero adjustment circuit OC composed of an inverting amplifier A2 to which a stable voltage is applied via Rv, and a reference common potential line SG is provided between the L terminal and the other input terminal of the inverting amplifier A2.
And the output terminal of the inverting amplifier A2 and the reference voltage generating circuit VS are connected by the signal ground line SG '. Examples will be described below.

〔Example〕

FIG. 1 is a connection diagram of an embodiment of the voltage generator according to the present invention. In the figure, VS is a reference voltage generating circuit that generates a reference voltage whose value is variable according to a set value. In the embodiment, VS generates a variable analog reference voltage Er according to the set value S given by a digital signal. It is composed of a digital-analog converter. A schematic equivalent circuit of the reference voltage generating circuit VS is shown in FIG. In FIG. 2, S is a setting means and U is an operational amplifier. The voltage Er corresponding to the set value is taken out from the output terminal of the operational amplifier U by the setting means S.

Returning to FIG. 1, A1 is an error amplifier to which the output of the reference voltage generation circuit VS is added to one input terminal, and RG is the power supply + V depending on the output of A1 to which the output of the error amplifier A1 is added to its control terminal r. Is a regulator that controls the output voltage of the. H,
L is a high-side and low-side input terminal to which the load LO is connected, and the output terminal of the regulator RG is connected to the terminal H. R1 and R2 are voltage dividing resistors that divide the voltage Eo generated between the terminals H and L, and the voltage dividing point is connected to the other input terminal of the error amplifier A1.

OC is a zero adjustment circuit added by the present invention. This zero adjustment circuit OC is an inverting amplifier using an operational amplifier OP.
The input resistance Ra of the inverting amplifier A2 is connected to the brush of the variable resistor Rv. A stable power source ± V is added to the variable resistor Rv. Inverting amplifier
The output terminal of A2 is connected to the reference voltage generating circuit VS via the signal ground line SG '. Dz1 and Dz2 are Zener diodes respectively, Dz1 is connected between the power supply + V and the output terminal of the inverting amplifier A2, and Dz2 is connected between the output terminal of the inverting amplifier A2 and the power supply -V. The non-inverting input terminal of the inverting amplifier A2 is connected to the resistance element r1 by the reference common potential line SG.
Is connected to the terminal L via. The terminal L is connected to the circuit common COM via the resistance element r2. The resistance elements r1 and r2 indicate the resistance of the switch for switching between the voltage mode and the current mode when the device of the present invention is used as a voltage / current generator, and the switching operation is not the essence of the present invention. Will be omitted.

In the voltage generator according to the present invention having such a configuration, when the desired reference voltage Er according to the set value is generated in the reference voltage generation circuit VS, this reference voltage is applied to one input terminal of the error amplifier A1. . A regulator RG is connected to the forward circuit of the error amplifier A1, and the output voltage Eo divided by the voltage dividing resistors R1 and R2 is applied to the other input terminal. As a result, the error amplifier A1 increases or decreases the voltage Eo so that the voltage Eo generated between the terminals H and L corresponds to the reference voltage Er. On the other hand, the potential generated at the terminal L is applied to the inverting amplifier A2 forming the zero adjustment circuit OC via the reference common potential line SG.

Zener diodes Dz1 and Dz2 are connected between the inverting amplifier A2 and the positive and negative power supplies ± V. Here, when the brush of the variable resistor RV is changed and positive and negative voltages are applied to the inverting amplifier A2 with reference to the potential of the reference common potential line SG, the reference common potential line SG connected to the non-inverting input terminal is generated. Amplifier A2
Between the signal ground SG ′ connected to the output terminal of
A stable voltage of ΔE is generated. This voltage ± ΔE is added to the output Er of the reference voltage generating circuit VS to generate Er ', which is an error amplifier.
Added to A1.

When a semiconductor switch is used as a changeover switch for switching between the voltage mode and the current mode, the internal resistances r1 and r2 are large, and the voltage drop due to this resistance is large. In this regard, in the circuit of FIG. 1, the route (r
2) and the reference common potential are separated by the reference common potential line SG. In this case, the resistors r1, r
In order that the voltage drop of 2 does not affect, the circuit current of the reference voltage generation circuit VS that generates the reference voltage Er 'is the reference common potential line.
It is necessary not to flow into SG. As a means for solving this, in the circuit of FIG. 1, the output terminal of the inverting amplifier A2 is set to the signal ground SG 'as described above, and the signal ground SG' and the reference common potential SG are made to correspond to each other. As shown by the dotted line in the figure, the circuit current of the reference voltage generation circuit VS is absorbed by this operational amplifier from the output terminal of the operational amplifier OP whose output impedance can be regarded as zero, so that it does not flow to the reference common potential line SG. (For this technology, the applicant of the present application filed a utility model application as the device name “voltage / current generator” on the same date as the present application).

Here, the reference voltage generating circuit VS is composed of an operational amplifier, and the error amplifier A1 is also an operational amplifier.
The operational amplifier has an offset component as described above. In this case, when the offset of the reference voltage generating circuit VS is ero and the offset of the error amplifier A1 is eao as shown, the output voltage Eo is represented by Eo = (Er + ero + eao + ΔE) .multidot. {R1 / (R1 + R2)}. Therefore, if (ero + eao + ΔE) = 0, that is, ΔE = − (ero + eao) (1), the error due to the offset of the operational amplifier is compensated and the zero point is adjusted. ΔE in equation (1)
As described above, this can be easily obtained by adjusting the position of the brush of the variable resistor RV connected to the input side of the inverting amplifier A2.

[Effect of the present invention]

As described above, according to the present invention, in a voltage generator configured by using a plurality of operational amplifiers, inverting amplifiers having variable inputs are connected subordinately to the operational amplifiers. It is possible to compensate the offset voltages of a plurality of operational amplifiers all at once by making the input of the variable. Therefore, according to the present invention, a voltage generator capable of generating a standard voltage with extremely high accuracy can be obtained with a simple configuration.

[Brief description of drawings]

FIG. 1 is a connection diagram of an embodiment of the device according to the present invention, and FIG. 2 is a schematic equivalent circuit diagram of a reference voltage generating circuit used in the device of FIG. VS ... Reference voltage generation circuit, A1 ... Error amplifier, H, L ... terminals, O
C ... Zero adjustment circuit, SG ... Reference common potential line, SG '... Signal ground.

Claims (1)

[Scope of utility model registration request] 1. A reference voltage generation circuit VS configured to use an operational amplifier to generate a variable reference voltage according to a set value, H and L terminals to which a load is connected, and an output terminal of the reference voltage generation circuit VS. Connected to one input terminal and output terminal is regulator RG
Error amplifier A1 composed of an operational amplifier which is connected to the H terminal via the terminal and a voltage corresponding to the output voltage generated between the H and L terminals is applied to the other input terminal, and a pair of output terminals connected to the error amplifier A1. A zero-point adjusting circuit OC composed of an inverting amplifier A2 in which a zener diode is connected and a stable voltage is applied to one input terminal via a variable resistor Rv is provided, and the L terminal and the inverting amplifier A2 are provided. A voltage generating circuit characterized in that it is connected to the other input terminal of the reference common potential line SG, and the output terminal of the inverting amplifier A2 and the reference voltage generating circuit VS are connected to each other by a signal ground line SG '. apparatus.