JPS5946132B2 - analog digital converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an analog-to-digital converter that electrically insulates minute input analog signals and converts the input analog signals into digital signals corresponding to the magnitude of the input analog signals.

SUMMARY OF THE INVENTION An object of the present invention is to realize an analog-to-digital converter that can perform signal isolation and obtain a digital signal that accurately corresponds to the magnitude of a minute analog signal with a simple configuration.

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

In the figure, 11.12 is an input terminal to which the input analog signal Ei is applied, C is a capacitor connected between input terminals 11.12, Dl and D2 are diodes connected in parallel with opposite polarities, and these are parallel diodes. It makes up the circuit.

TR is a transformer 21 having a primary winding nl g, a secondary winding n2 and a tertiary winding n3; 22 is an output terminal connected to both ends of the secondary winding n2; and O8 is a pulse generator connected to the tertiary winding n3. It is a vessel.

CK is an arithmetic means that inputs two types of pulse width signals obtained at the output terminals 21 and 22, and has a time width counting function and an arithmetic function.

As this calculation means, for example, a microprocessor is used.

The primary winding n1 of the transformer TR is connected to input terminals 11 and 12 through a parallel diode circuit, and these constitute an input circuit, and the secondary winding n2 constitutes an output circuit.

FIG. 2 is a characteristic diagram of a parallel diode circuit, and the applied voltage e and the flowing current 11 have a nonlinear relationship as shown.

In the device configured as described above, the turn ratio between the primary winding n1 and the secondary winding n2 of the transformer TR is set to 1:1, and a pulse signal i having positive and negative symmetry is applied to the tertiary winding n3.

, the equivalent circuit is as shown in FIG.

In the equivalent circuit of Figure 3, the switch S is a diode D
1. This shows the switching operation of D2. When a positive pulse is applied from the pulse generator O8, switch S is connected to contact a side (diode D is conductive), and a negative pulse is applied. When is applied, the switch S is connected to the contact side (diode D2 is conductive).

diode ha. D2 is both expressed as a forward voltage Δ.

Now, when the positive pulse +Io is being applied from the pulse generator O8, the switch S is equivalent to being connected to the contact a (the diode D1 is conductive), and the inductance L of the coil representing the transformer TR is If the current flowing there is iL, then (1) holds true at the rise of the pulse.

Similarly, when a negative pulse -Io is applied from the pulse generator O8, the switch S is equivalent to being connected to the contact point (diode D2 is conductive), and at the falling edge of the pulse (2) The formula holds true.

In formula (1), iL is from -Io to ■.

The time t required to reach this point can be expressed by equation (3).

Furthermore, in formula (2), iL is ■.

The time t2 from t2 to -Io can be expressed by equation (4).

Therefore, the output terminal 21 of the secondary winding n2 (output circuit)
．． A voltage signal is generated between 22 and 22 only when the current iL flowing through the coil is changing, and this voltage signal e is related to the input analog signal Ei as shown in equations (3) and (4). Two types of pulse width signals having a pulse width (time width) of 11.12 are obtained.

FIG. 4 is an operational waveform diagram of the circuit of FIG. 3.

From the pulse generator O8, the operation as shown in Fig. 4A is performed.

When a changing pulse signal is applied to qIo, current 11s12 flows through the diode circuit and the input circuit on the input terminals 11 and 12 as shown in the opening in Figure 4 at the rise of the pulse and at the fall of the pulse. , In addition, a current iL as shown in FIG. 4 flows through the inductance L.

Here, the time t1 until jl pi2 becomes zero,
t2 is expressed by equations (3) and (4).

When a current iL that linearly rises or falls as shown in the fourth diagram flows through the inductance L, the output terminal 21.2
Between 2 and 2, there are pulse widths t1 and tt2 as shown in FIG.
A signal e can be obtained.

The output terminals 21, 22 have the pulse width t1. of the pulse width signal generated here. A calculation means CK such as a processor having a function capable of determining t2 (for example, a function of counting time) and a calculation function is connected, and 2
While finding the time width 11.12 of the seed pulse width signal, calculations as shown in equation (5) are performed.

As a result, it is possible to obtain a digital signal corresponding to the input analog signal Ei in the digital calculation means CK.

In equation (5), if Δ1=Δ, =Δ, then equation (5) becomes as shown in equation (6). Therefore, by performing the calculation in equation (5) in the digital calculation means CK, the result is obtained. The digital signal corresponding to the input analog signal Ei is the inductance L of the transformer, which is a circuit element for signal isolation, and the signal 2 from the pulse generator O8.

It is not affected by the size of

FIGS. 5 and 6 are connection diagrams showing other embodiments of the present invention.

The embodiment of FIG. 5 uses a plurality of (here, two inputs) input DC signals E il @ E 12
The tertiary windings n3 of each transformer TR are connected in series, and a driving pulse signal i is supplied from a pulse generator O8.

It was designed to give

Here, the pulse generator O8 is composed of a positive and negative polarity constant current source C8 including a square wave oscillator O8C, a diode bridge circuit that manually inputs an output signal from this oscillator, and a constant current element Q that utilizes the constant current property of an FET. This is what I did.

The embodiment shown in FIG. 6 uses a transformer TR having a primary winding n□ and a secondary winding n2, and the pulse generator O8 is connected to a secondary winding n
It is connected to both ends of 2.

In this case as well, the operation is exactly the same as that of the circuit shown in FIG.

Note that the pulse generator O8 may be connected between both ends AB of the primary winding n1.

7 to 9 are connection diagrams showing other examples of parallel diode circuits.

FIG. 7 shows a structure in which a plurality of diodes connected in series are connected in parallel.

The forward voltage Δ can be adjusted by changing the number of diodes connected in series.

FIG. 8 shows a structure in which transistors are diode-connected and connected in parallel with each other with opposite polarities.

FIG. 9 shows a configuration in which Zener diodes are connected in parallel.

In the above embodiment, the ratio between the primary winding n1 and the secondary winding n2 of the transformer TR does not have to be 1:1.

Further, the capacitor C connected between the input terminals 11 and 12 may be omitted.

As explained above, the present invention (according to this invention) is an analog/digital system that can isolate minute analog signals and at the same time obtain a digital signal that is accurately proportional to the input analog signal without being affected by circuit elements for signal isolation. A converter can be realized.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing an embodiment of the present invention, FIG. 2 is a characteristic diagram of a parallel diode circuit used in the present invention, FIG. 3 is an equivalent circuit of the circuit in FIG. 1, and FIG. 5 is a diagram showing its operating waveforms, FIGS. 5 and 6 are connection diagrams showing other embodiments of the present invention, and FIGS. 7 to 9 are connection diagrams showing other examples of parallel diode circuits. 11.12... Input terminal, 21, 22...
...Output terminal, D...Parallel diode circuit, T
R...Transformer, nl...Primary winding,
n2...Secondary winding, n3...Tertiary winding, O8...Pulse generator, C...Capacitor, CK... Digital calculation means.

Claims (1)

[Claims] 1. A transformer having a primary winding and a secondary winding, a nonlinear circuit having a nonlinear voltage-to-current characteristic such that a current starts flowing when the applied voltage exceeds a predetermined value, and an input analog signal circuit means for applying a rectangular wave pulse signal to the primary winding of the transformer through a circuit; means for applying a rectangular wave pulse signal to any of the primary winding, secondary winding, and tertiary winding of the transformer; Two types of pulse width signals obtained from the secondary winding are input, and the time width of these pulse width signals is 11.
1. An analog-to-digital converter comprising digital calculation means for calculating 12 and calculating - to obtain a digital signal corresponding to the input analog signal.