JPS63300626A - Pulse signal isolating circuit - Google Patents

Abstract

PURPOSE:To isolate a wide pulse signal even with a pulse transformer having not so much large voltage time project by converting an input pulse signal into a pulse signal of a prescribed length or below, and using a decoding circuit at the output side to decode the signal. CONSTITUTION:An original pulse signal string S1 is supplied to an exclusive OR gate 9 together with a coding clock signal C1, and converted into a coded pulse signal train S2. The signal train S2 and the clock C1 drive the input terminal of a pulse transformer 6 via drivers 10, 11. A coded pulse signal train S2' and a coded clock signal C1' retarded by a propagation delay time are outputted from receivers 12,13. Then, the signal is supplied to an exclusive OR gate 14 and converted into a reproduction pulse signal train S3. The pulse signal train S2 is a pulse signal having equal to or twice the width of the clock signal C1, and in selecting properly the clock signal C1, the isolation of the pulse signal train including the wide pulse is attained by using a transformer whose voltage time product is small.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a method for insulating, by a pulse transformer, a pulse signal train transmitted from one of two electronic circuits belonging to different current supply sources to the other. Regarding insulation circuits.

[Conventional technology]

In some cases, power is supplied to two electronic circuits from different systems for long-distance data transmission where the ground potentials are different, or for noise suppression or signal level conversion even within the same printed board. Signal insulation is essential for the stand.

FIG. 6 shows a conventional example of a signal isolation circuit. This uses a photocoupler 3, where 1 is a driver for driving the photocoupler, 2 is a current limiting resistor, 4 is a receiver into which the signal from the photocoupler is input, and 5 is a puller for receiver 4. It is up resistance. However, while the 7-point coupler is capable of transmitting wide pulses up to direct current, the high-speed version is expensive, occupies a large area, and has low reliability due to aging. was there.

In FIG. 7, a pulse transformer is used, and 6 is the pulse transformer. Those using pulse transformers have high waveform transmission properties, high reliability, high-speed operation, and are inexpensive.

Note that other symbols in the figure are the same as in FIG. 6.

[Problem that the invention seeks to solve]

However, when transmitting a pulse signal train including wide pulses in which O1 or 1 are continuous as shown in FIG. 8, a pulse transformer with a sufficiently large voltage-time (ET) product is required. Generally speaking, a pulse transformer with a large ET product has a slow response speed, is small in size, and is expensive.

Therefore, it is an object of the present invention to make it possible to isolate a wide pulse signal even with a pulse transformer that does not have a very large ET product.

[Means for solving problems]

Of the two electronic circuits that belong to different power supply sources, the transmitter electronic circuit has an input pulse signal train consisting of a series of pulse signals. The receiver electronic circuit is provided with a decoding circuit for converting this encoded pulse signal train into the original pulse signal train.

[Effect]

An encoding circuit is provided on the transmitting side of the pulse signal train to convert each pulse signal of the input pulse signal train consisting of a series of pulse signals into a pulse signal of a certain length (axis) or less, and a decoding circuit is installed on the receiving side. is provided to convert the encoded pulse signal train into the original pulse signal train, thereby making it possible to isolate both circuits using a pulse transformer with a small ET product.

〔Example〕

Figure 1 is a main diagram that clearly shows the characteristic amount of gold of this invention.
a and 6b are pulse transformers, and 7 is an encoding circuit.

In this configuration, the original pulse signal train S1 including a wide pulse signal and the encoding crunch signal C1 are input to the encoding circuit 7, and the encoded pulse signal train S2 is output. The encoded pulse signal train S2 and the encoding pulse signal C1 are each insulated by pulse transformers 6a and 6b and sent to the receiving side circuit, and then passed through the decoding circuit 8 to reproduce reproduction pulses similar to the original pulse signal train S1. Signal train S3
is converted to

FIG. 2 is a circuit diagram showing an embodiment of the present invention, and FIG. 3 is a waveform diagram of each part for explaining its operation.

This is a nine-part embodiment of Figure 1, and is an exclusive disjunction (B
OR) Gate 9 and differential driver 10.11 encode the circuit, and differential receiver 12.15 and EO
A decoding circuit is formed by the R gate 14. code 6
is a pulse transformer.

At ζ~, when the original pulse signal train S1 shown in FIG. 5
1ti is converted into the coded pulse signal train $2 shown in FIG. The encoded pulse signal train S2, the encoding clock signal c1, and the encoder drive the input end of the pulse transformer 60 through differential drivers 10 and 11, respectively. The output end of the pulse transformer 6 is coupled to a differential receiver 12.13, and from both receivers, an encoded pulse signal train 82' as shown in FIG. ) is output as an encoding clock signal CI'.

Encoded pulse signal train 82' and encoding clock signal CI
' is input to an EOR gate 14 different from ', and converted into a reproduction pulse signal sequence S3 as shown in FIG.

The encoded pulse signal train S2 output from the EOR gate 9 is called a Manchester code or a pi-phase code, and can be a pulse signal with the same length or width as the encoding clock signal C1. Are known. Therefore, by appropriately selecting the encoding clock signal C1, it is possible to isolate a pulse signal train including wide pulses using an inexpensive pulse transformer with a small ET product.

Figure 4 shows the encoding method for expansion, which is f/2f
code or PDM (Pulse Period Modulation) code.

In this case, each pulse signal of the original pulse signal train is converted into a pulse signal with a unit pulse width Tu or less, so
The same effect as above can be obtained.

FIG. 5 is a schematic diagram showing another embodiment of the present invention. By providing the decoding circuit 8a with a clock extraction function, even when encoding that includes a clock component, including the various codes used above, the clock signal C1 for encoding can be used. The signal line and pulse transformer 6b' can be omitted, making it particularly suitable for long-distance data transmission. Further, the driver and receiver connected to the pulse transformer do not necessarily have to be differential circuits as shown in FIG. 2, but may be of the type shown in FIG. 7.

〔Effect of the invention〕

According to this invention, an encoding circuit is provided on the input side of the pulse transformer to convert each input pulse signal into a pulse signal of a certain length (constant @) or less, and this is sent to the decoding circuit on the output side. Since the decoding is performed using a pulse transformer having a small ET product, it is possible to isolate a pulse signal train including wide pulses using a pulse transformer having a small ET product.

[Brief explanation of drawings]

Figure 1 is the main diagram that best represents the features of this invention;
Figure 6 is a circuit diagram showing an embodiment of Jin's invention, Figure 6 is a waveform diagram of each part to explain its operation, Figure 4 is a waveform diagram to explain another example of the encoding method, and Figure 5. 6 is a circuit diagram showing a conventional example of a pulse signal insulating circuit, FIG. 7 is a circuit diagram showing another conventional example of a pulse signal insulating circuit, and FIG. FIG. 2 is a waveform diagram showing an example of a pulse signal train including wide pulses in which ot or 1 are successive. Symbol explanation 1...Driver, 2...Current limiting resistor, 3...Photocoupler, 4...Receiver, 5...Pull-up Resistance, 6.6a, 6b・
...Pulse transformer, 7...Encoding circuit, 8,8a...Decoding circuit, 9゜14...
・・Exclusive OR (BOR) gate, 10°11...
...Differential driver, 12.13...Differential receiver, Sl...Original pulse signal, 82...
. . . Encoded pulse signal train, S3 . . . Reproduction pulse signal train, C1 . . . Encoding clock signal train. 1st gu ([ (I 2nd 3rd 1) C1 -) S2 ->S; 4th thunder 5 fig.

Claims (1)

[Claims] In order to isolate a pulse signal train transmitted from one of two electronic circuits belonging to different power supply sources to the other by a pulse transformer, an input pulse consisting of a series of pulse signals is provided to the transmitting electronic circuit. An encoding circuit is provided for converting each pulse signal of the signal train into a pulse signal having a predetermined width or less, and the receiving electronic circuit is provided with an encoding circuit for converting the encoded pulse signal train into the original pulse signal train. 1. A pulse signal isolation circuit comprising a decoding circuit.