JPS63173420A - Analog/digital converter - Google Patents

Abstract

PURPOSE:To improve the accuracy of A/D conversion by holding a D/A converter output voltage in obtaining an A/D converter by a sample-and-hold circuit, amplifying the difference between the value and a signal to be measured and applying A/D conversion again so as to add a value of new A/D conversion to a conventional A/D conversion value. CONSTITUTION:A sample-and-hold circuit 8 outputs an A/D conversion value Da obtained by a conventional circuit constitution and samples and holds the output voltage of a D/A converter 5 by the control of the timing circuit 6. The holding voltage is inputted to a differential amplifier 9 together with an output voltage of the buffer circuit 1 and only the difference of the both is amplified. The amplification factor in this case is selected to amplify the error voltage within one bit resolution to a value of A/D conversion again. When a switch circuit 10 selects the differential amplifier 9, the measuring range is decided by the amplification factor set by the differential amplifier 9 and its value is given in the same process as the A/D conversion by a conventional circuit operation to obtain the conversion data. Since the conversion data is given to the least significant bit of the conventional circuit operation, then the measuring accuracy as the A/D converter is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to the field of measurement that handles analog signals as signals on the wave meter side.

[Conventional technology]

FIG. 2 shows a conventional successive approximation type A/D converter.

In the figure, (1) is a buffer circuit for impedance conversion of the wave meter sub-signal, (21 is the buffer circuit (
1) A voltage ratio soft comparator that compares the signal vt voltage of the D/A converter +51 (31 is a successive ratio soft register that stores the signal of the voltage ratio soft comparator 121, (41 is a reference voltage generation circuit, ( 51 is the reference voltage generation circuit (4
The O/A converter (6) which inputs the voltage of the successive approximation register (31) and generates an analog voltage corresponding to the data of the successive approximation register (31) is a timing circuit which controls the timing of the above operation;
) is a register for accumulating the A/D conversion value that is the output of the successive approximation register (3), and Da is the register (
This is the output value of 71.

[While the invention is trying to solve the problem]

According to the above-mentioned Yasei, the measurement accuracy of a human/D converter is determined only by the resolution of the D/A converter itself, so in order to improve measurement accuracy, K is a D/A converter with better resolution. There was a problem in that a converter was required, leading to an increase in price.

This invention was made in order to solve the above-mentioned problem of interpolation, and it is possible to convert the D/D f without changing the D/A converter.
The purpose is to improve the resolution of the wedge device.

[Means for solving problems]

The A/D conversion device according to the present invention holds the D/A converter output voltage when obtaining the conventional A/D conversion value in a sample/hold circuit, and calculates the difference between that value and the plate needle image signal. By amplifying the signal and A/D converting it again, the A/D converted value is added to the conventional A/D conversion by 9wr, thereby improving the human/D conversion accuracy of the human/D conversion device. .

[Effect]

The differential amplifier in this invention takes the difference between the D/A converter output voltage held by sample and hold and the output voltage of the buffer circuit, and amplifies the error voltage, which is within 1 bit. The error voltage is made A/D convertible again, and the A/D conversion value obtained by A/D conversion is added to the conventional human/D conversion value to improve human/D conversion accuracy. .

〔Example〕

FIG. 1 is a block diagram showing an embodiment of the present invention.

In the figure, ftl~(71 is exactly the same as the above-mentioned conventional circuit.

In FIG. 1 above, the sample/hold (8) is the timing circuit (8) that outputs the output voltage of the D/A converter (51) when it outputs the human/D conversion value Da obtained by the conventional circuit configuration.
6) is sampled and held by 1filJ (ii4). The voltage held by the sample and hold (8+) is input to the differential amplifier 191 together with the output voltage of the buffer circuit (11). Well then.

Only the difference voltage between the sample and hold circuit (8) and the buffer circuit (ri) is amplified. In this case, the amplification factor is such that the error voltage within the resolution of 1 bit is amplified to a value that allows A/D conversion again.

The output of the buffer circuit (1) and the differential amplifier (91)
The switch circuit 6O selects the output of the buffer circuit (11) using the timing circuit (6), when performing A/D conversion using the conventional circuit configuration, selects the buffer circuit (11), and when operating according to the present invention, selects the differential amplifier +9+. do.

If the above differential amplifier (9) is selected, the differential amplifier (9)
) The measurement range is determined by the amplification factor set in ), and the converted data is obtained in the same process as A/D conversion by conventional circuit operation. Since this conversion data is added to the least significant bit of the conventional circuit operation, it is possible to improve the measurement accuracy as a one-person/D conversion device. Also, a differential amplifier (91
The amplification factor can be varied up to 111, which is the resolution of the D/A converter 151.

〔Effect of the invention〕

As described above, according to the present invention, by freely setting the amplification factor of the differential amplifier, the A/D conversion accuracy can be improved compared to the conventional A/D conversion device.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG.
The figure is a configuration diagram showing a conventional circuit. In the figure, (1) is a buffer circuit, (21 is a voltage comparison type comparator, (3) is a successive approximation register, C41 is a reference voltage generation circuit, (5) is a D/A converter, (6) is a timing circuit, and C7 is a reference voltage generation circuit. ) is a register, and (8) is a sample/hold. +91 is a differential amplifier, and α· is a switch circuit. Note that the same symbols in Figure 9 indicate the same or equivalent parts.

Claims (1)

[Claims] A buffer circuit that converts the impedance of an analog signal given from the outside, and a D/A converter for the output of the buffer circuit.
A voltage comparison type comparator that compares the voltage with the converter output voltage, a successive approximation register that inputs the comparison result of the voltage comparison type comparator and whose operating speed is controlled by a timing circuit, and an analog output of the successive approximation register. The A/D converter is composed of a D/A converter that converts into a voltage, a reference voltage generation circuit that supplies a reference voltage to the D/A converter, and a register that stores A/D converted values when the reference voltage is supplied. In the D converter, there is a sample/hold for holding the D/A converter output voltage when the above A/D converted value is obtained under the control of a timing circuit, and the above sample/hold.
A differential amplifier that amplifies the difference between the hold output voltage and the buffer circuit output, and a switch circuit that switches the buffer circuit output and the differential amplifier output under the control of a timing circuit, the analog voltage from the buffer circuit is converted into an A/D converter. An A/D conversion device characterized in that measurement accuracy is improved by using a converted value and a value obtained by A/D converting the analog voltage from the differential amplifier.