JPS63224414A - A/d converter - Google Patents

Abstract

PURPOSE:To obtain a converter capable of measuring a voltage without lowering measuring accuracy even when the voltage exceeding the generation voltage of a D/A conversion circuit is measured, by deciding a most significant order bit by comparing a signal to be measured with the output voltage of a reference voltage, and setting a result as an offset voltage to a voltage comparison type comparator. CONSTITUTION:The voltage comparison type comparator sets decision whether an input signal Sa exceeds the reference voltage or not as the decision of the voltage of the most significant order bit by comparing the input signal Sa with the output voltage of a reference voltage generation circuit 3 via adder circuit 7, and when it is decided that the signal Sa does not exceed the reference voltage, a switching circuit 6 selects the output of the D/A conversion circuit 4, then applies a usual A/D conversion. When it is decided that the signal Sa exceeds the reference voltage, the circuit 6 remains unchanged. Therefore, the voltage in which the output voltage of the conversion circuit 4 is added on the reference voltage is supplied to the comparator 1, then, the A/D conversion is applied. For this reason, it is possible to provide a doubled measuring range without lowering the measuring accuracy on a usual device.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] This BA relates to the field of measurement that handles analog signals as the first measurement target.

[Conventional technology]

Figure 2 shows a conventional sequential comparison type A/D converter. (3) is a reference voltage generation circuit, (4) is the reference voltage generation circuit (3)
) input voltage and generates an analog voltage corresponding to the data of the sequential comparison register (2).
) is a timing circuit that controls the timing of the above operation,
Da is an A/D conversion value.

[Problem that the invention seeks to solve]

According to the above configuration, the resolution of the circuit is determined only by the oscillation g:'tIt pressure of the D/mu conversion circuit.

When measuring a voltage higher than the voltage generated by the D/A conversion circuit,
The input voltage must be reduced and A/D converted, reducing the measurement accuracy, and the measurement accuracy may be reduced.
)/A conversion circuit is required.

There was a problem that led to an increase in the number of llff1 cases.

This invention was made to eliminate the above-mentioned problems, and even when measuring a voltage higher than the D/A variable generation voltage, it is possible to measure without reducing measurement accuracy. The purpose is to obtain a capable A/D conversion device ltk.

[Means to resolve the problem tps]

The A/D converter according to the present invention selects the output of the MI true circuit using the switch circuit, and compares the output voltage of the reference voltage generation circuit via the adder circuit with the human input signal using the voltage comparison type comparator.1- By doing so.

The determination of the upper bit of the A/D conversion in 26 is performed in this device. A latch circuit is created based on the results of step 7.

The switch circuit is controlled to determine whether to supply the voltage of the adding circuit or the voltage of the L D/Af circuit. For this reason, two devices can be used without reducing the conventional measurement accuracy.
It is set to 5 so that it can have twice the measurement range of gE rice.

[Effect]

This invention is a svf pressure ratio type Konopa V-Yu.

By comparing the human input signal with the national voltage of the reference voltage generation circuit via the adder circuit, it is determined whether the input signal exceeds the output voltage of the reference voltage generation circuit or not by determining the voltage of the most significant bit. If the result is not exceeded, the switch circuit selects the output of the Ll/A converter circuit and converts it to the conventional A/A converter.
Perform D conversion. Further, if it is determined that the determination result exceeds the output voltage of the reference voltage generation circuit, the circuit does not change to a switch circuit.

Therefore, fl D/A to the voltage comparison type comparator
The output hidden pressure of the conversion circuit plus the national power voltage of the reference tortoise pressure generation circuit is supplied and A/D conversion is performed. As a result, the heavy equipment f does not reduce the measurement degree of the conventional A/D converter (it has twice the measurement range).

〔Example〕

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

In the figure, (1) to (5) are completely the same as the conventional circuit described above. In Figure 1 above, the timing circuit (
5) controls the latch circuit (8) so that the switch circuit (6) selects the IXJ arithmetic circuit (7), and also controls the D
The successive ratio fL' resistor (2) is controlled so that the national power voltage of the /A conversion circuit (4) is not generated. Therefore, by comparing the measured signal Sa and the output voltage of the fc reference voltage generation circuit via the adder circuit (7) in the m-voltage comparison type conhalator (1), A bit voltage determination is performed.

When the voltage comparison type comparator (1) determines that the measured signal Sa is lower than the output voltage of the reference voltage generation circuit (3), the determination result is stored in the latch circuit (81). In addition to obtaining the top pit Db of A/D conversion, the above switch circuit 2) can be switched to the above D/A conversion circuit (4).

Furthermore, A/D conversion by the conventional circuit is started. At this time, the switch circuit (6) is connected to the D/A circuit (4).
), the output voltage of the adder circuit (7) is not synthesized, and A/D conversion is performed only by the output voltage of the D/A converter circuit (4), which is the same as the conventional circuit. D f chivalry value Da((can be obtained.

In addition, when it is determined that the signal to be measured as a result of the comparison of the upper d self-voltage comparison type co/valley meter (11) is lower than the national power voltage of the reference voltage generation circuit (3), the latch circuit (8) 6) is not driven and the adder circuit (7) remains selected.Furthermore, the output voltage of the adder circuit (7) is the output voltage of the reference '1 pressure generating circuit (3) and D/p,
The national power voltage of the converter circuit (4) is combined into one shift and A/
The D transformation is performed. Therefore, by using the A/D transformation b and the Asahi of Da together, it is possible to have twice the measurement range without lowering the measurement range compared to the conventional A/D transformation. .

[The young fruits of invention]

As described above, according to the present invention, the most significant bit is determined by comparing i' with the national power voltage of the surveyor number and the reference voltage generation circuit, and the result can be used as the offset voltage to the voltage comparison type comparator. can.

Therefore, it is necessary to lower the measurement accuracy (conventional A/
J) A measurement range twice as large as that of a converter can be obtained.

[Brief explanation of drawings]

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 voltage comparison type comparator, (2) is a sequential ratio soft register, (3) is a reference voltage generator circuit, and (4)
(5) is a timing circuit, (6) is a switch circuit, (7) is a latch circuit, and (7) is a +81U control circuit. Note that the same reference numerals in Figure 9 indicate the same or corresponding parts.

Claims (1)

[Claims] A voltage comparison type comparator that compares the voltage of the measured signal given from the outside and the output voltage of the D/A conversion circuit; A/D conversion consisting of a comparison register, a D/A conversion circuit that converts the output voltage of the sequential comparison register into an analog voltage, and a reference voltage generation circuit that supplies a reference voltage to the D/A conversion circuit. In the device, the input signal of the voltage comparison type comparator is controlled by a timing circuit to switch the output voltage of the adder circuit and the output voltage of the D/A converter circuit, and the output of the reference voltage generation circuit via the adder circuit. A latch circuit that latches and stores the A/D conversion value when the voltage is selected, and the output voltage of the reference voltage generation circuit and D
An A/D converter including an adder circuit that synthesizes output voltages of the A/A converter circuits.