JPH04207527A - A/d converter circuit - Google Patents

Abstract

PURPOSE:To improve the resolution in A/D conversion without increasing number of comparators being components of the A/D converter circuit by employing a subtractor and a multiplexer. CONSTITUTION:The A/D converter circuit is provided with a comparator 5 comparing an analog signal outputted from an S/H(Sample-and-Hold) section 4 with a reference voltage generated from a reference voltage generating section 3, a subtractor 6 subtracting a reference voltage generated by the reference voltage generating section 3 from the analog signal outputted from the S/H section 4 and a multiplexer 7 selecting the analog signal outputted from the subtractor 6 by using the digital signal outputted from the comparator 5. Thus, the resolution of the A/D(Analog to Digital) conversion circuit 11 is a product of resolutions of voltage discrimination circuits to improve the resolution. Thus, the resolution of the A/D converter is improved without increasing number of comparators being components of the A/D converter circuit 11.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a multi-bit A/D conversion circuit that obtains a resolution greater than the number of converters.

[Prior Art] FIG. 3 is a block diagram showing an example of a conventional A/D conversion circuit. In the figure, (1) is the front-stage analog circuit, (2) is the rear-stage digital signal, (3) is the reference voltage generator, and (5)
is a converter, and (8) is an encoder.

The reference voltage generator (3) generates a reference voltage for comparison in the comparator (5). Converter (5
) compares the analog signal from the previous-stage analog circuit (1) with the reference voltage from the reference voltage generator (3) and outputs a digital signal. The encoder (8) is a converter (5
) and outputs the digital code to the subsequent digital circuit (2).

[Problems to be Solved by the Invention] In conventional A/D conversion circuits, when increasing the resolution of A/D conversion, it is necessary to increase the number of converters that constitute the A/D conversion circuit. However, there is a problem in that there is a limit to the increase in the number of converters due to problems such as heat generation and an increase in input capacity.

This invention was made to solve the above-mentioned problems, and its purpose is to increase the resolution of A/D conversion without increasing the number of converters that make up the A/D conversion circuit. .

"Means for Solving the Problems" The A/D conversion circuit according to the present invention includes a comparator that compares an analog signal output from the S/8 section with a reference voltage generated in the reference voltage generating section. A/D The resolution of the conversion circuit is the product of the resolutions of each voltage determination circuit, and the resolution can be increased.

[Function] A according to this invention 2. The D conversion circuit can perform A/D conversion without increasing the number of converters that make up the A/D conversion circuit.
The resolution of D conversion can be improved.

[Embodiment] FIG. 1 is a block diagram showing one embodiment of the present invention. In the figure, (3) is the reference voltage generation section, (4) is the 878 section,
(5) is a converter, and (6) is a subtractor.

(7) is a multiplexer, and (8) is an encoder.

Note that components not related to this invention are omitted.

The 878 section (4) holds the analog signal from the previous stage analog circuit (1) for a certain period of time.

First, the inside of the first voltage determination circuit (9) will be explained.
The analog signal output from section 8 (4) is 0 to 4x. Referring to FIG. 2(a), the reference voltage generating section (3) generates a 2x reference voltage. A subtraction section (6) subtracts the reference voltage 2x generated by the reference voltage generation section (3) from the analog signal output from the S/8 section (4) shown in FIG. 2(a). The converter (5) compares the analog signal from the S/8 section (4) with the reference voltage from the reference voltage generation section (3) and outputs a digital signal. The multiplexer (7) is switched by the output of the converter (5). If the reference voltage generation section (3) is higher than the 87/H section (4), switch to the 878 section (4) side, and in the opposite case, switch to the subtraction section (6).
Can be switched to the side. The output range of the multi-f lexer (7) is 0 to 2x. See FIG. 2(b) for the output of the multiplexer (7).

Next, the second voltage determination circuit (10) will be explained.

The reference voltage generator (3) generates an X reference voltage. The converter (5) compares the analog signal from the multiplexer (7) in the first voltage determination circuit (9) with the reference voltage from the reference voltage generator (3) and outputs a digital signal. The encoder (8) is a converter (5) in the first voltage determination circuit (9), and a second voltage determination circuit (10).
The digital signal from the converter (5) in the converter is encoded and a digital code is output to the subsequent digital circuit (2).

Note that a large number of converters and subtraction units may be arranged in parallel.

[Effects of the Invention] As described above, according to the present invention, by using a subtracter and a multiplexer, the resolution of A/D conversion can be increased without increasing the number of comparators constituting the A/D conversion circuit. be able to.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an A/D conversion circuit according to an embodiment of the present invention, and FIG. 2 is a graph showing each signal waveform. Figure (b)
is a graph showing a multi-register output signal in the first voltage determination circuit, and FIG. 3 is a block diagram of a conventional A/D conversion circuit. In the figure, (1) is a front-stage analog circuit, (2) is a rear-stage digital circuit, and (3) is a reference voltage generation section. (4) is the S/8 section, (5) is the converter, (6) is the subtraction section, (7) is the multiplexer, (8) is the encoder, (9) is the first voltage judgment circuit, (10) is the first 2, (11') is an A/D conversion circuit according to an embodiment of the present invention, and (12) is a conventional A/D conversion circuit. Note that the same reference numerals in each figure indicate the same or corresponding parts.

Claims (1)

[Claims] S/H (Samp) that holds the input analog signal for a certain period of time
a reference voltage generation section that generates a reference voltage, a subtraction section that takes the difference between the output of the S/H section and the reference voltage from the reference voltage generation section, and the output of the S/H section and the reference voltage generation section. a converter that compares the reference voltage from the
A multiplexer that switches between the subtraction section output and the S/H section output using a comparator output, and a voltage determination circuit consisting of the reference voltage generation section, subtraction section, comparator, and multiplexer are connected in multiple stages, and the digital signal from the comparator is encoded. A/D (Ana
log to Digital) conversion circuit.