JPS6315511A - Isolator - Google Patents

Abstract

PURPOSE:To obtain outputs of various zero levels and spans by providing a photocoupler selecting, isolating and sending one signal among time width signals generated from a duty modulation circuit and a switch selecting a different reference voltage sources depending on the introduced signal through the photocoupler. CONSTITUTION:An input signal is given to the duty modulation circuit, where the signal is converted into plural time width signal keeping an H or L level depeding on the level of the input signal. One time width signal selected to have a required level as a demodulation output among the plural signals is given to the photocoupler 20, the light of the light emission part reaches the light receiving part of the photocoupler, where the light is converted again into the time width signal. The time width signal is given to a switch circuit 30' which leads the signal to two paths between two different reference power supplies 33, 34 and an integration circuit 35 selectively depending on the H, L level of the signal and the signal is smoothed in the integration circuit 35.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to improvements in duty modulated finators.

2. Description of the Related Art For example, when introducing electrical output from a sensor into its measurement circuit, it may be necessary to isolate the signal path between the sensor and the circuit to protect the circuit. Although a photocoupler is generally used in such an isolation unit, errors inevitably occur due to a difference in characteristics between the electric-to-optical converter and the optical-to-electrical converter. In order to eliminate the above-mentioned error, it is conceivable to first convert the input signal to the photocoupler (for example, the output from the sensor) into a time width signal, and then transmit and receive the signal. That is, in this case, the input signal A is compared with the triangular wave B repeatedly sent out from the triangular wave oscillator, and is binarized so that when A > B, the level is "I", and when the signal is "L" level, when < B (t), and in this way, the deterioration in the absolute magnitude of the signal level becomes unrelated to the signal information.

By the way, the time width signal received via the photocoupler in this way is then demodulated, which requires a rectifier circuit consisting of an operational amplifier, a diode, etc. Is required. However, in this type of rectifier circuit, errors due to the characteristics of nonlinear elements are unavoidable, and the rectification method is also a fixed one that corresponds to the time width signal. There was a problem that it was difficult to change the level.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention configures a duty modulation circuit for forming a time width signal and its demodulation circuit using logic circuit elements, and provides a method for forming a time width signal. , a plurality of time width signals having different time width changes corresponding to the input signal are formed, and the time width signals "I" and "L" are
a duty modulation circuit that selectively conducts two types of reference power supplies in correspondence with one another, and forms a plurality of different time width signals corresponding to the magnitude of an input signal;
A photocoupler that insulates and transmits one time width signal selected from the time width signals, and a photocoupler that is selectively opened and closed by the time width signal introduced through the photocoupler, and selectively connects different reference voltage sources. It consists of a switch that turns on and off, and an integrating circuit for the output of the switch circuit.

In the above, the input signal is introduced into the duty modulation circuit, and the input signal is set to "H" or "L" depending on the magnitude of the input signal.
``It is converted into a periodic time width signal whose time width for keeping the level changes, and it is also converted into a periodic time width signal whose inverted signal, or an AND or OR signal between these signals and a 1/2 frequency divided signal of the periodic signal. Then, one time width signal selected from among the plurality of time width signals according to the magnitude required as the final output (output of the demodulation circuit) is introduced into the photocoupler. The time width signal drives the light emitting part of the photocoupler, and the light reaches the light receiving part of the photocoupler, where it is converted back into a 1 time width signal.Then, the time width signal is introduced into the switch circuit, The two different reference power supplies and the integrating circuit are selectively brought into conduction depending on the H and L levels. Then, the integrating circuit performs smoothing. Therefore, the type of time width signal and the two standards The selection of the power supply (positive, negative predetermined value, or O) will create outputs of various zero levels and spans.

Embodiment 1 In FIG. 1 and FIG. 2 showing output waveforms of each part thereof, 10 is a duty modulation circuit, and a comparison circuit 12 into which the input signal A and the sawtooth wave B of the sawtooth wave generator 11 are introduced.
, the output ■ of the comparator circuit 12 and gAt! output from the sawtooth oscillator 11. ]-shaped wave period divided into full wave periods.”
A binary frequency divided signal of "H" and "L" was introduced, and the above
a time width signal forming section 13 having an inverter circuit that forms an inverted output (■), an OR circuit, and an AND circuit that forms an OFF output (■) and an AND output (■) of the inverter circuit output (■) and the frequency-divided signal, respectively; It consists of a selection switch 14 that selectively turns on each of the outputs (1) to (4) of the time width signal forming section 13.

20 is a high-speed photocoupler, and the selection switch 14
The light emitting section 21 is connected to the light emitting section 21, and the light receiving section 22 receives the light and reproduces an electrical output corresponding to the amount of light. 3
o is a demodulation circuit, which includes a switch circuit 30' consisting of switch elements 31 and 32 that are selectively turned on and off by the output of the light receiving section 22 and its inverted output, and an integration circuit using each of the switch elements 31 and 32. It consists of first and second reference power supplies 33 and 34 connected to the output terminal of 35. In the above case, the comparator circuit 12 compares the input signal A and the sawtooth B as shown by the number 12 in FIG.
A binarized output (2) which becomes "H" during the time period is formed and sent to the time width signal form r&, section 13. Subsequently, the time width signal forming section 13 generates an inverted output (2) of the output (2), an OR output (2) between the output (2) and the frequency-divided signal, and an AND output (2). Then, the switch 14 selects a necessary output from among the outputs (1) to (4), and the light emitting section 21 is driven by the selected output to emit light. When the light reaches the light receiving section 22, an electrical output corresponding to the amount of light received, that is, an output similar to the output selected by the switch 14 is reproduced. In other words, the input signal and demodulation circuit 30 are connected via this high-speed photocoupler 20.
There is isolation between the two. Then, in the demodulation circuit 30, conduction of each reference output from the output first and second reference power sources reproduced by the light receiving section 22 is selectively controlled, and in the integration circuit 35, the conduction output is smoothed. and output. Therefore, for example, now switch 1
4 selects the output ■, and the first and second reference power supplies 33.
34 outputs are respectively set to +Vr and 0, the input signal A
The output decreases from +Vr to 0 in response to a linear increase in
If output ■ is selected under
If r, the span will be from -Vr to +Vr open, which will be twice the above. Also, for example, the switch 14 can output
If you select , the respective reference power supplies +Vr, 0 and +
The outputs at Vr and Vr are +Vr/2 to +Vr and VO to 10Vr, and when output ■ is selected,
The output under each of the above reference power supplies is -Vr/2 to -Vr,
0 to -Vr, and demodulated outputs of various zero levels and spans can be obtained depending on the selection output and the output of the reference power supply. In the above embodiment-1, the input signal A is an analog signal, but in the case of a digital signal, a counter that counts clock pulses and the output of the counter are compared with the dinotal input signal A. , an output h similar to that described above is generated according to the comparison result. In this case, the output is converted into an analog output by the demodulation circuit 30, so that this device ultimately constitutes a DA converter.

The effects of the invention are as described above, and the present invention selectively controls conduction and interruption by a plurality of different time width signals that change in response to an input signal and a time width signal selected from among the time width signals as necessary. Since it has two reference power supplies with different outputs,
Demodulated outputs of various zero levels and spans can be extracted, and the type of output required can be easily extracted.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an output waveform diagram thereof. 10: Duty modulation circuit 20: High speed photocoupler 30: Demodulation circuit

Claims (1)

[Claims] 1. A duty modulation circuit that forms a plurality of different time width signals corresponding to the magnitude of an input signal, a photocoupler that insulates and transmits one time width signal selected from the time width signals, and the photocoupler. An isolator comprising a switch that is selectively opened and closed by a time width signal introduced through the circuit to selectively conduct or cut off different reference voltage sources, and an integrator circuit for the output of the switch circuit.