JPS5921125A - Analog-digital converter - Google Patents

Abstract

PURPOSE:To ensure a digital conversion with high resolution and a low cost, by providing a counter which counts the prescribed pulses with an over-range of an A/D converter and using the output of the counter to compensate the input of the A/D converter. CONSTITUTION:The voltage ES-E0 obtained by subtracting the compensating voltage from unknown input voltage ES to be converted by an analog subtractor 2 is applied to an unknown voltage input terminal of an A/D converter 1. When the voltage ES-E0 exceeds the full-scale voltage of the converter 1, an over-range output terminal 3 is inverted to an H level. Then a counter 6 counts pulses P, and the voltage E0 increases. The voltage ES-E0 is reduced due to an increment of voltage E0 and approximates to the full-scale input voltage. The increment of E0 continues until the terminal 3 is reset to an L level. When the terminal 3 is reset to the L level, a digital conversion output 10 of the converter 1 is turned into a lower digital output to the voltage ES. At the same time, a digital count output of the counter 6 is turned into an upper digital output to the ES. Thus it is possible to have an A/D conversion with higher resolution than a case where just a single unit of converter 1 is used.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an analog-to-digital converter, and relates to an analog-to-digital converter that has a small H-divided power by installing an external circuit.
1 to configure a converter 6Xi with a large resolution.
purpose.

Recently, there has been a trend for household products such as microwave ovens and Mur air conditioners to use micro convenience stores.

In this case, analog input (ja ljj) is processed from digital converter C via an analog-to-digital converter (hereinafter referred to as ADC). However, since high-resolution ADC is expensive, In home-use products, low-cost, low-resolution (generally 8 bits 1) AL) C is used at the expense of control accuracy of 41 mm.

The present invention includes an analog multiplier that subtracts a correction voltage from an unknown human power voltage to be converted, and an output voltage of this analog subtraction 8:9 applied to an unknown [E input terminal].
A counter that generates d1 pulses of a predetermined repetition period during the overrange period of this ADC, and a digital/analog switch that converts the digital output of this counter to analog and converts it into the rated I correction SL pressure are provided. Said A.D.
(:(D f
'lJ counter's digital conversion output, □key-side digital conversion output of the unknown input voltage to be changed], :I
, a''j'' enables low-cost, high-resolution digital conversion.

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 and 2.

(+) fat low resolution AI) C, '(Es, -Eo), which is obtained by subtracting the correction voltage Eo from the unknown input voltage Es to be converted by the analog subtracter (2), is applied to the unknown voltage input terminal. There is. In addition, when this ADC(+') reaches full scale, the state changes from "'L"'→"t("°
(An overrange output terminal (3) that inverts this is provided. (4) is an AND gate that passes the pulse P output from the pulse oscillator (5) between the overrange signal of ADCfl). , (6) is a counter that counts 81 pulses P' output from the AND gate (4).In order to make the explanation easier to understand, we will first refer to this counter (6).
will be explained assuming that counting is executed while the start signal (7) is at the "H" level. <9) is a digital-to-analog converter (hereinafter referred to as DAC) that converts the gain output (8) of the counter (6) into analog, and the conversion output of this DAC <9) is the analog subtracter. (
2) is applied to the paper number input and acts as 'CQ (I correction m pressure Eo).

FIG. 2 is an illustrative waveform diagram of the main part, assuming that the counters (13), . (a) shows No. 48 of (ES-EO), EFS is ADC
+11 full-scale input voltage. (Es-EO
) exceeds the full-scale input voltage EFS of ADC (1), as shown in Figure 2 (b), the overrange output terminal (3) is inverted by 1 (n level). The start signal (7) of (6) is shown in Figure 2 (c).
``[('' and flip it to a bell, the counter (6
) executes 81 pulses P', and the extracted voltage Eo of the output of the DAC (9) increases by 1 as shown in the second 'w,h (d).

Due to this increase in correction voltage EO, (Es-Eo) becomes second
As shown in section W in Figure (a), the full-scale input voltage Eps approaches the full-scale input voltage Eps. Increase in the corrected electrical ratio Eo (counter (θ
) continues until the over range output terminal (3) of A D CO, ) returns to the L" level. In this way, the A D C (1) □σ in over range Output □ Output MM child (3) goes from H” level to L”
When the level is restored, the digital conversion outputs of A, D and C(t) are the lower digital outputs of the unknown human pressure ESI to be converted, and the counter (6)
The digital counting output (8) becomes the upper digital output for the unknown input voltage JEsl to be converted, and the ADC
(It will be an analog-to-digital converter with higher resolution than the one outside the state.

Incidentally, the Illll raster start signal of the counter (6) is actually a reset signal at the conversion period (high phase) of the ADC (1), and the counter ( When (Es-EO)>EFS, the force ``j''> ``(6) counts up and (Es-Eo) becomes converted. It becomes smaller than the unknown input voltage Es, and ADC (1) performs digital conversion within the overrange.

As explained above, according to the present invention 1, low resolution ADC
A counter is provided to count pulses of a predetermined repetition period due to the overrange of Let J be a digital output of 1ζ relative to the unknown input voltage, and convert the counting digital 1' output to the required unknown human power + 1. BU8BA D CJ: High resolution 11i
5 converter can be added to the town by adding an inexpensive external circuit.
, -.
■:.

[Brief explanation of drawings]

Claims (1)

[Claims] 1. An analog subtracter that subtracts the correction voltage from the unknown human power pressure to be converted, an analog-to-digital converter that applies the output voltage of this analog subtracter to the unknown voltage input terminal, and this analog-to-digital converter. a counter that generates a pulse of a predetermined repetition period during an overrange period of
A digital-to-analog converter is installed to convert the digital conversion output of this counter into analog to obtain the correction voltage (), and the digital conversion output of the analog-to-digital converter is converted to 11 (j An analog-to-digital conversion device in which the digital conversion output of the counter (1) is used as the upper digital conversion output of the unknown human force Yh pressure to be converted (1iI).