JPS5931249B2 - Analog-digital converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an analog-to-digital (hereinafter abbreviated as AD) conversion device having a calibration function.

A conventional AD converter is shown in FIG. 1, and will be explained with reference to the waveform diagram in FIG. 2.

In FIG. 1, AI is an analog input signal, and 7 is a reference voltage generator for calibrating the analog-to-digital converter, which outputs a reference voltage 10.

SW is an analog switch that selects either the analog input signal AI or the reference voltage 10 of the reference voltage generator 7 using the input selection signal 3 output from the control calculation circuit 6 and outputs it to the amplifier power 1; An amplifier 5 amplifies the amplifier power 1 with a specified amplification degree and outputs it to the AD converter power 41, and 5 is an AD converter that AD converts the AD converter power 41 and outputs it to the digital output line 51.

6 is a control calculation circuit which outputs an AD conversion command 2 and an input selection signal 3 according to a predetermined program to control the AD conversion device, and also reads out the contents of the memory 8 storing reference digital data; It performs calculations for correction and outputs digital data DO.

8 is a memory for storing reference digital data;
DO is the digital digital output of the calibrated analog input signal.
2 is an AD conversion command for performing AD conversion, 3 is an AD conversion command for performing AD conversion.
is the input selection signal.

Next, the operation of the conventional device will be explained.

When the AD converter starts operation from point A shown in FIG. 2C, the input selection signal 3 shown in FIG.
The signal is output to select the switch SW or the reference voltage 10, and the switch SW is switched to the reference voltage side.

The reference voltage 10 switched to the reference voltage side is input to the amplifier 4 as shown in the opening of FIG.
Converter 50 input.

At this time, the control calculation circuit 6 outputs A as shown in FIG.
D conversion command 2 is output and the amplified reference voltage A
D-convert the reference digital data to digital output line 5
Output to 1.

This reference digital data is input to the control calculation circuit 6, and is stored in the memory 8 as shown in FIG.

Next, the control calculation circuit 6 outputs the input selection signal 3 as shown in FIG. 2 so that the switch SW selects the analog input signal AI, switches the switch SW to the analog input signal side, and selects the analog input signal AI. The signal is input to the amplifier 4 as shown in Figure 2.

The analog input signal amplified by the amplifier 4 is sent to the AD converter 5.
The signal is input to the control calculation circuit 6, is AD converted by the AD conversion command shown in FIG.

The AD converted data is the reference digital data previously stored in the memory 8, that is, the SDO shown in FIG.
is calculated and corrected, and output from the control calculation circuit 6 as digital data DO, thereby obtaining digital data of the analog input signal AI.

Here, the analog input signal AI is AD converted, and the memory 8
Assuming that one cycle of the AD converter is one cycle of the AD converter in which a correction operation is performed using the reference digital data SD stored in the data SD and the digital data Do is obtained, the reference digital data SD1 is added every n cycles as shown in FIG. ．． S
D2...... is created with a constant period T as shown in Fig. 2.

The AD converter is calibrated every time.

However, the AD converter shown in Fig. 1 calibrates the AD converter at regular intervals, so the power is turned off.
Immediately after changing from the F state to the ON state, or in the case of a sudden change in ambient temperature, etc., it is not possible to follow the change in the state of the AD converter, resulting in a decrease in the accuracy of the AD converter during that period.

This invention has been made to eliminate the drawbacks of the above-mentioned devices, and provides an AD converter that does not reduce accuracy even when the state of the AD converter changes.

An embodiment of the present invention is shown in FIG. 3 and explained below with reference to FIG. 4.

In FIG. 3, the same reference numerals as in FIG. 1 indicate the same or corresponding parts.

Reference numeral 31 denotes a state change detector for detecting the state of the AD converter, which outputs a state change detection signal 32 when a state change such as a fluctuation in power supply voltage or a sudden change in ambient temperature occurs.

Next, the operation of the embodiment of the invention shown in FIG. 3 will be explained.

Now, if the AD converter starts operating at point A shown in FIG. 4 and there is a change in the power supply voltage, the state change detector 31 outputs a state change detection signal 3 as shown in FIG.
2 is output to the control calculation circuit 6.

The control calculation circuit 6 inputs the state change detection signal 32 and
It is known that a state change has occurred in the conversion device 5.

As a result, the control calculation circuit 6 calibrates the AD conversion at T at first as shown in FIG. 4-2.

, followed by T1. The switch SW, AD converter, etc. are controlled so as to perform the operation at a cycle T2...Tm.

Here, To, T1.・・・・・・・・・Tm time is T.

＜T1〈T2 く・・・・・・〈There is a relationship between Tm. Immediately after a state change occurs, calibration is performed every short period of time, increasing as time passes, and finally, calibration is performed at a constant period Tm. Make sure to do the following.

While the AD converter is in operation, as shown at point B in FIG.
For example, even when the ambient fluctuation suddenly changes, the state change detection signal 32 is output from the state change detector, and the calibration period is T as in the above case.

, T1. T2......Changes as Tm.

As mentioned above, according to the embodiment of the present invention, the state of the AD converter 5 suddenly changes, the state of the analog circuit of the amplifier 4 and the AD converter 6 changes, and zero drift, gain drift, etc. occur. Also, since the AD converter is calibrated to follow the changes, there is no transient decrease in accuracy due to state changes.

As explained above, according to the present invention, there is no reduction in accuracy due to drift of the AD converter due to sudden changes in power supply voltage, ambient temperature, etc., and the AD converter has a short warm-up time.
A conversion device can be provided.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram showing a conventional AD conversion device, FIG. 2 is a timing diagram for explaining the operation of the device shown in FIG. 1, and FIG. 3 is a configuration diagram showing an AD conversion device according to an embodiment of the present invention. 4 are timing charts for explaining the operation of the device shown in FIG. 3. In the figure, SW is a switch that switches between the input signal and the reference voltage, 4 is an amplifier, 5 is an AD converter, 7 is a reference voltage generator that generates a reference voltage for calibration, 6 is a switch that controls the entire AD converter, A control arithmetic circuit performs data correction calculations, 9 is a memory for storing basic digital data used for correction, and 31 is a state change detector for detecting state changes of the AD converter. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] 1 A digital signal corresponding to the analog signal is obtained by applying an analog signal to a digital-to-analog converter via an amplifier, and a reference voltage is applied in advance to the digital-to-analog converter via the amplifier. In an analog-to-digital converter that stores a reference digital signal in a memory and periodically inputs a reference voltage to periodically calibrate the analog-to-digital converter, there is no effect on the operation of the analog-to-digital converter. provide means for detecting a change in state that causes
An analog-to-digital conversion device characterized in that the calibration cycle is changed to become shorter in accordance with the state change.