JPS6059806A - Offset processing method of operational amplifier - Google Patents

Abstract

PURPOSE:To adjust the offset of an operational amplifier with a single power supply by subtracting an offset component in the process that an output voltage of the operational amplifier is extracted and processed. CONSTITUTION:A prescribed bias voltage is applied to a non-inverting input terminal + of the operational amplifier OP by varying a variable resistor VR2 of a voltage division circuit RV2 in order to offset the operational amplifier OP of a peak value detector 12, its output voltage is offset to a prescribed positive value without being adjusted to zero, and said offset component is subtracted in calculating an effective value from a peak value by using a microprocessor 14. Thus, a single power supply is enough for the power supply.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an offset processing method for an operational amplifier, and particularly to an offset processing method for an operational amplifier that allows offset adjustment of an operational loudspeaker using a single power supply. It is about the method.

[Prior art]

Generally, operational amplifiers are widely used in analog calculation circuits and signal processing circuits for high-precision amplification and calculation, but even if the input signal is zero, an offset voltage is generated on the output side, which causes the output voltage to This is a factor that causes errors. Therefore, as shown in FIG. 3, the two positive and negative power supplies E are connected so as to supply a predetermined IA voltage to the inverting input terminal e of the operational amplifier OP including the input resistor R1 and the feedback resistor R2.
Variable resistor vR1 and resistor Rt1 connected between 1 and 82
A voltage dividing circuit Rv1 consisting of +R'1s is provided, and the output voltage of the operational amplifier OP is adjusted to zero by varying the bias voltage using the variable resistor VRi. However, such a conventional device has a drawback in that two power sources, a positive power source and a negative power source, are required. In addition, in FIG. 3, VxN and v2 are positive and negative power supplies E1 and F,
1 and υ are the power supply terminals of the operational amplifier OP to which voltages are supplied, and IN is the input terminal.

[Summary of the invention]

The present invention has been made in view of the above points, and an object thereof is to provide an offset processing method for an operational amplifier that can perform offset adjustment of an operational amplifier using a single power supply.

In order to achieve such an object, the present invention provides an operational amplifier having two input terminals with a voltage divider circuit that divides the voltage from a single power supply and supplies a variable bias voltage, Input the variable bias voltage supplied from the voltage divider circuit and the input signal to one input terminal of the amplifier (when adjusting the offset of the operational amplifier, perform calculation by varying the bias voltage supplied from the voltage divider circuit) By offsetting the output voltage of the amplifier to a constant value, the offset is subtracted by 7 in the process of extracting the output voltage of the operational amplifier and processing it.Hereinafter, Embodiments of the present invention will be described based on the drawings.

〔Example〕

FIG. 1 is an overall schematic block diagram for explaining an embodiment in which the operational amplifier offset processing method according to the present invention is applied to a digital multimeter for a generator, and FIG. 2 is a detailed diagram of the main parts thereof. FIG. In these figures, 1 is a generator that outputs a sinusoidal AC voltage by the rotation of an engine (not shown), and this AC voltage is supplied to an AC load (not shown) via an AC output terminal 2. The voltage is full-wave rectified by a pair of rectifier diodes 4ay4b, converted into a DC voltage, and then supplied to a battery 5 as a DC load via a DC output terminal 3. 6 is a current detection transformer that detects the sinusoidal alternating current flowing from the generator 1 to the AC load via the AC output terminal 3; 7 is a current detection transformer that detects the peak value of the alternating current detected by the current detection transformer 6; 8 is a voltage detection transformer that detects the sinusoidal AC voltage supplied from the generator 1 to the AC load via the AC output terminal 2; 9 is the AC detected by the voltage detection transformer 8; This is a peak value detector that detects the peak value of voltage.

10 is connected to the generator 1 via the DC side terminal 3 [1
, a current detection resistor 11 detects a distorted wave current having a waveform phased with a full-wave rectified wave as shown in FIG. 4) as a direct current flowing into the battery 5. As shown in FIG. and a capacitor C. Reference numeral 12 denotes a peak value detector that detects the peak value of the integral output integrated by the integrating circuit 11. This peak value detector 12 has an input resistor R1 connected to one non-inverting input terminal (■) of the operational amplifier OP.
, and a feedback resistor R is connected to the feedback loop between its output end and the other inverting input terminal e via a diode D1.
1 is connected to the ground via a resistor R8, forming a non-inverting amplifier circuit, and the connection point between the cathode of the diode Dl, whose anode is connected to the output end of the operational amplifier op, and the feedback resistor Rs, and the ground. Resistor R41 capacitor cl between
Connect a different integration circuit. An offset adjustment circuit is connected to the non-inverting input terminal of the operational amplifier OP. It is configured as. That is, when adjusting the offset of the operational amplifier op, the peak value detector 12 adjusts the offset of the operational amplifier op by varying the variable resistor VRz of the voltage dividing circuit RVs and supplying a predetermined bias voltage to its non-inverting input terminal ■. The output voltage of the OP is not adjusted to zero, but is offset to a constant positive value. Reference numeral 13 denotes an A- which converts the respective peak values corresponding to the AC current, voltage and DC current detected by the respective peak value detectors 7, 9 and 12 as input signals into A-D (Analog-Digital). D converter, 14 is the A-D converter;
This microprocessor 14 is a normal microprocessor that uses the peak value A-D converted by the converter 13 as input data and calculates the effective value from the peak value. mode selection signal.

The effective value of the calculation result corresponding to the mode selection signal is transferred as measurement data to the digital display 15 for digital display.

Next, the operation of the above embodiment will be explained. Here, it is assumed that the peak value detector 12 performs offset adjustment on the operational amplifier OP as described above, so that its output voltage is offset to a positive one-step value. Therefore, when measuring the sine wave alternating current output from the generator 61, the current detection transformer 6
detects the alternating current that is in phase with the sine wave and inputs it to the peak value detection path 7. Accordingly, the peak value detector 7 detects the peak value of the alternating current detected by the current detection transformer 6, and the peak value is detected by the A-D converter 13.
-D conversion and input to the microprocessor 14. Then, the microprocessor 14 uses the peak value output from the A-D converter 13 as input data, and calculates the effective value by multiplying the peak value by a constant value (1/7-2). , and its effective value is displayed on the digital display 15 as the effective value of the alternating current. Furthermore, when measuring the AC voltage from the generator 1 as an effective value, the measurement can be performed in the same manner.

Next, when measuring the DC current flowing from the generator 1 to the battery 5 via the DC output terminal 3, the DC voltage becomes a full-wave rectified wave as shown in Figure 4 ←). The current becomes a distorted wave having a waveform similar to an intermittent full-wave rectified wave as shown in FIG. 4(b), and the current detection resistor 10 detects this. Then, the integrating circuit 11 integrates the distorted wave current detected by the current detection resistor 10 through the resistor R and the capacitor C, and the integrated output waveform becomes relatively smaller than the waveform of the original distorted wave current. It is input to the peak value detector 12. At this time, the peak value detector 12
When the capacitor C1 is in the initial state of one value due to the offset adjustment of the operational amplifier OP, the operational amplifier 0Pit operates as a comparator and outputs a positive voltage to the output terminal side according to its input voltage to conduct the diode Dl. A negative feedback loop is formed, and the peak value of the input voltage is held by the capacitor C1. And operational amplifier OP
When the output voltage becomes larger than the input voltage, the diode DI becomes non-conductive and operates as an open-loop comparator, and this operation is repeated every cycle of the input voltage. As a result, the output point a of resistor R4 and capacitor CI
A peak value obtained by superimposing a constant value of an offset on the input voltage is detected.

Accordingly, the peak value detected by the peak value detector 12 is A-D converted by the A-D converter 13 and then input to the microprocessor 14. Therefore, when calculating the effective value from the peak value in the same way as when measuring the alternating current described above, the microprocessor 14 calculates the effective value by subtracting the offset.
The effective value of the distorted wave can be displayed on the digital display 15.

As described above, according to the above embodiment, when measuring a distorted wave current as shown in FIG. By integrating the waveform and detecting its peak value with the peak value detector 12, even if the waveform of the distorted wave current is relatively large in distortion compared to a full-wave rectified wave, it is regarded as a full-wave rectified wave. The effective value can be calculated from the peak value. Therefore, the resistance R of the integrating circuit 11
The integration constant of and capacitor C is the distortion method of the current waveform, and the energization time (also called duty) is 17Il.
: By selecting the appropriate value accordingly), it becomes possible to measure a value close to the effective value with an error of several percent for a strain waveform whose effective value cannot be measured by detecting the peak value. Therefore, compared to the conventional method in which the effective value is calculated from the open value of the waveform, the processing is easier, and it is also cost effective and simplified.

In addition, in order to adjust the offset of the operational amplifier OP of the peak value detector 12, a predetermined bias voltage is supplied to the non-inverting input terminal (■) of the operational amplifier OP by varying the variable resistor VRi of the voltage dividing circuit RV8, and the output The voltage is not adjusted to zero, but is offset to a constant positive value at intervals of τ, and the microprocessor 1
By subtracting the offset when calculating the effective value from the peak value in step 4, there are advantages such as unification of the power source.

In addition, although the above-mentioned embodiment shows the case where the offset adjustment is performed on the operational amplifier of the peak value detector used in the digital multimeter, the present invention is not limited to this, and the output signal of the operational amplifier is taken out and various types of adjustment are performed. It can be applied to all devices that perform calculation processing.

〔Effect of the invention〕

As explained above, according to the offset processing method for an operational amplifier according to the present invention, offset adjustment can be performed using a single power supply, which has the effect of simplifying the power supply and reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a general block diagram for explaining an embodiment in which the operational amplifier offset processing method according to the present invention is applied to a digital multimeter for a generator, and FIG. A circuit configuration diagram of an integrating circuit and a peak value detector; FIG. 3 is a circuit configuration diagram showing an example of a conventional operational amplifier;
FIGS. 4(IIL) and 4(b) are waveform diagrams of the full-wave rectified wave voltage and distorted wave current supplied from the generator of FIG. 1 to the battery via the DC output terminal. 10... Resistor for current detection, 11... Integrating circuit,
12... conflict peak value detector, 13... A, T')
Converter, 14. Compensation microprocessor, 15...
・Digital display, OP-・O・Operation amplifier, R1...
...Input resistance, R2...Feedback resistance, R3...Resistor, RVs...Voltage divider circuit, VRI, a e a
e variable resistance, R2t, R2s@e e ++ resistance, El
...Φ positive power supply. Patent applicant: Koito Seisakusho Co., Ltd. Representative: Kazuko Yamakawa (1 person)

Claims (1)

[Claims] In an operational amplifier having two input terminals, a voltage divider circuit that divides a voltage from a single power supply and supplies a variable bias voltage is provided, and one input terminal of the operational amplifier is connected to the voltage divider circuit and the voltage divider circuit. Inputting the supplied variable bias voltage and input signal, and when adjusting the offset of the operational amplifier, offset the output voltage of the operational amplifier to a constant value by varying the bias voltage supplied from the voltage dividing circuit. An offset processing method for an operational amplifier, characterized in that the offset amount is subtracted in the process of extracting and processing the output voltage of the operational amplifier.