JPS62198713A - Differential transformer interface circuit - Google Patents

Abstract

PURPOSE:To obtain a circuit capable of operating even with a single power source which has no negative voltage by connecting the output terminal of a level shift voltage generating circuit to high potential terminals for rectification outputs of two rectifying circuits. CONSTITUTION:Alternating-current voltage induced across secondary coils L2-1 and L2-2 of a differential transformer 2 are rectified with the rectified output voltage of bridge rectifying circuits 3 and 4. The DC components of the rectified output voltages of those circuits 3 and 4 are denoted as V1 and V2, which are negative voltage based upon the potentials at the high potential terminals for the rectification outputs of the circuit 3 and 4 where the output terminal of the level shift voltage generating circuit 9 is connected. Further, g=f+V1 and h=f+V2, where (g) and (h) are input voltages of low-pass filters 5 and 6 and (f) is a level shift voltage. Further, when the voltages (g) and (h) which are level-shifted with the voltage (f) from the circuit 9 are enabled to be obtained at low potential terminals for the rectification outputs of the circuits 3 and 4, the outputs of the filters 5 and 6 are also level-shifted voltage (i) and (j) and a displacement voltage is shifted to an optical level by the single power source which has no negative voltage.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a differential transformer interface that converts an alternating current voltage obtained from the secondary side of a differential transformer into an input voltage of an AD (analog/digital) converter, etc. It is related to circuits.

[Prior art]

Conventionally, the technology in this type of field is Newton (Newton).
ton) Separate volume 1 All about sensors” (Sho 6O-4-20
) There is a differential transformer listed in Kyoikusha.

FIG. 2 is a circuit diagram showing a conventional differential transformer interface circuit constructed using the above-mentioned differential transformer. In the figure, 1 is a drive circuit that drives the primary side of the differential transformer, 2 is a differential transformer, 3.4 is a bridge rectifier circuit, 5 and 6 are low-pass filters, 7 and 8 are level shift circuits, and 9 is a This is a level shift voltage generation circuit. The differential transformer interface circuit having the above configuration operates as follows.

First, the differential transformer 2 has a primary coil according to the displacement amount X of F Cr, and two secondary coils L ! -1*
The degree of magnetic coupling between L 1-1 changes differentially, and when the primary coil L is driven with an AC voltage by the drive circuit 1, the two secondary coils Lm-+ 1 L
! -1, an alternating current voltage proportional to the degree of magnetic coupling with the primary coil is induced. These two secondary coils L
, -, , L, -, respectively, are rectified by bridge rectifier circuits 3 and 4, and low-pass filters 5,
6 to obtain displacement voltages a and b.

FIG. 3 shows the displacement X of the core Cr and the low-pass filter 5.
, 6 is a diagram showing the state of the displacement amounts JEa and b smoothed by . As shown, the displacement voltage a.

b changes linearly in opposite directions according to the left and right displacement when the displacement amount X of the core Cr is zero, that is, when the core Cr is at the center position.

When measuring displacement with an AD converter, it is necessary to shift the displacement voltages a and b to increase the resolution of the AD converter, and the displacement voltages a and b are generated as level shift voltages by level shift circuits 7 and 8. Voltage C generated from circuit 9
As a result, the displacement voltages d and e shown in FIG. 4 are obtained.

FIG. 5 is a circuit diagram showing an example in which the level shift circuits 7 and 8 are specifically constructed using operational amplifiers. In the figure, 10 is an operational amplifier, and 11 to 14 are resistors all having the same resistance value. As shown, input terminal 16
When the displacement voltages a and b smoothed by the low-pass filter 5.6 are input to the input terminal 15, and the level shift voltage C output from the level shift voltage generation circuit 9 is input to the input terminal 15, a displacement shifted by the voltage C from the output terminal 17 is obtained. Voltages d and e are output.

[Problem that the invention seeks to solve]

However, in the conventional differential transformer interface circuit described above, the voltage level at the 1-'' input terminal of the operational amplifier 10 shown in FIG. However, when the operational amplifier 10 is operated with a single power supply, there is a problem in that the operational amplifier 10 does not operate normally because the output voltage of the operational amplifier 10 is around Ov and no current is absorbed. Further, there are many level shift circuits 7 and 8 other than those shown in FIG. 5, but they generally require a negative voltage and cannot operate with a single power supply.

The present invention has been made in view of the above-mentioned points, and it is an object of the present invention to provide a differential transformer interface circuit which eliminates the above-mentioned problems and can operate even with a single power supply without a negative voltage.

[Means for solving problems]

In order to solve the above problems, the present invention provides two
One of the secondary coils is connected to an AC input terminal of a first rectifier circuit, the other is connected to an AC input terminal of a second rectifier circuit, and the rectifier output terminals of the first and second rectifier circuits are connected. A differential transformer interface circuit that uses a direct current voltage obtained from The high potential end of the rectified output of the circuit and the high potential end of the rectified output of the second rectifier circuit are connected to the low potential end of the rectified output of the first rectifier circuit and the low potential end of the rectified output of the second rectifier circuit. The configuration is such that a level-shifted displacement voltage can be obtained using a positive level-shifting voltage from the terminal and the level-shifting voltage generating circuit.

[Effect]

With the above configuration, the output end of the level shift voltage generation circuit is connected to the high potential end of the rectified output of the first rectifier circuit and the high potential end of the rectified output of the second rectifier circuit, and
Since a level-shifted displacement voltage is obtained between the low potential end of the rectified output of the rectifier circuit and the low potential end of the rectified output of the second rectifier circuit, the differential transformer interface circuit shown in FIG. It is possible to obtain a displacement voltage shifted to an arbitrary level without requiring the level shift circuits 7 and 8, and even with a single power supply that does not have a negative voltage.

〔Example〕

Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a circuit diagram showing the configuration of a differential transformer interface circuit according to the present invention. In the figure, parts with the same reference numerals as those in FIG. 2 indicate the same or equivalent parts. The output end of the shift voltage generation circuit 9 is connected to the high potential end of the rectified output of the bridge rectifier circuit 3 and the high potential end of the rectified output of the bridge rectifier circuit 4. The operation of the differential transformer interface circuit shown in FIG. 1 will be explained below.

First, the operation of the drive circuit 1 and the differential transformer 2 is as follows.
This is similar to the conventional differential transformer interface circuit shown in the figure. Secondary coil L of differential transformer 2! -1*
The AC voltage induced in L t-1 is passed through the bridge rectifier circuit 3.
, 4. The DC component of the rectified output voltage of the bridge rectifier circuit 3 is Vl, and the DC component of the rectified output voltage of the bridge rectifier circuit 4 is V.

Then, when the potential between the high potential end of the rectified output of the bridge rectifier circuit 3 and the high potential end of the rectified output of the bridge rectifier circuit 4 to which the output end of the level shift voltage generation circuit 9 is connected is taken as a reference, the voltage V I, V x becomes a negative voltage, and the relationship between the input voltages g, h of the low-pass filters 5 and 6, the level shift voltage f, and the voltages V, , V is as follows: g-f'+Vl, h-f+V! Then, the displacement
, 6 and the DC voltages V, , V of the bridge rectifier circuits 3, 4 are as shown in FIG.

According to the above embodiment, the output end of the level shift voltage generation circuit 9 is connected to the high potential end of the rectified output of the bridge rectifier circuit 3 and the high potential end of the rectified output of the bridge rectifier circuit 4. Since the displacement voltage a9g level-shifted by the level shift voltage f from the level shift voltage generation circuit 9 is obtained at the low potential end of the rectified output and the low potential end of the rectified output of the bridge rectifier circuit 4, the low pass filter 5 , 6 are similarly level-shifted displacement voltages 1+J, which eliminates the need for level shift circuits 7 and 8 as in the conventional differential transformer interface circuit shown in FIG. It becomes possible to shift the displacement voltage to any level with one power supply.

〔Effect of the invention〕

As described above, according to the present invention, the output end of the level shift voltage generation circuit is connected to the high potential end of the rectified output of the first rectifier circuit and the high potential end of the rectified output of the second rectifier circuit. , the configuration is such that a level-shifted displacement voltage is obtained between the low potential end of the rectified output of the first rectifying circuit and the low potential end of the rectified output of the second rectifying circuit. Unlike the differential transformer interface circuit, the level shift circuits 7 and 8 are not required, and the displacement voltage can be shifted to any level even with a single power supply without negative voltage.It is an inexpensive differential with a small number of parts. This provides an excellent effect of providing a dynamic transformer interface circuit.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing the configuration of a differential transformer interface circuit according to the present invention, FIG. 2 is a circuit diagram showing the configuration of a conventional differential transformer interface circuit, and FIG. 3 is a circuit diagram showing the configuration of a conventional differential transformer interface circuit. A diagram showing the relationship between the amount of displacement X of the core of the differential transformer in the interface circuit and the displacement voltages a and b smoothed by a low-pass filter. Figure 4 also shows the core of the differential transformer in the differential transformer interface circuit shown in Figure 2. displacement amount X and displacement voltages a and b smoothed by a low-pass filter
and the displacement voltage d level-shifted by the level shift circuit.
, e, FIG. 5 is a circuit diagram showing an example in which the level shift circuit of the differential transformer interface circuit shown in FIG. 2 is specifically configured using an operational amplifier, and FIG. 6 is a diagram showing the relationship between The amount of displacement X of the core of the differential transformer interface circuit according to the present invention, the displacement voltages i, j smoothed by a low-pass filter, and the DC component voltages V, , V of the bridge rectifier circuit,
FIG. In the figure, 1...drive circuit, 2...differential transformer, 3, 4...bridge rectifier circuit, 5.6...
Low-pass filter, 7.8...level shift circuit,
9...Level shift voltage generation circuit. X Funabi 111; Iki 5 Jun? n) Ranzui Shifufu r-Z mouth 1〒1, Fig. 1 Conventional difference first torsui; Fufu 1-Nuro response Fig. 2 Fig. 3 Fig. 4

Claims (1)

[Claims] One of the two secondary coils of the differential transformer is connected to the AC input terminal of the first rectifier circuit, the other is connected to the AC input terminal of the second rectifier circuit, and the first and second rectifiers A differential transformer interface circuit that uses a DC voltage obtained from a rectified output terminal of a circuit as a displacement signal, and includes a level shift voltage generation circuit that generates a positive voltage for level shifting, and an output terminal of the level shift voltage generation circuit. is connected to the high potential end of the rectified output of the first rectifier circuit and the high potential end of the rectified output of the second rectifier circuit, and the low potential end of the rectified output of the first rectifier circuit and the second A differential transformer interface circuit characterized in that a level-shifted displacement voltage is obtained at a low potential end of a rectifier output of a rectifier circuit.