JPS584257Y2 - 2 wire isolator - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a two-wire isolator.

As a condition for realizing a two-wire isolator, it is desired that current or voltage loss be small between the person and the output.

The present invention realizes a two-wire isolator that meets the above objectives by modulating an input DC signal using a pair of complementary semiconductor switching elements and then demodulating it via a capacitor.

FIG. 1 is an electrical connection diagram showing one embodiment of the isolator of the present invention.

In FIG. 1, INl. ■N2 is the DC input signal ■Terminal 0UT1゜0UT2 is the DC output signal I
2 is the terminal to be taken out.

FET1. FET2 is a field effect transistor used as a switching element.

For example, if a MOS type P-channel FET 1 is used as the FET 1, an N-channel FET 2 that is complementary to the FET 1 is used as the FET 2.

O20 is an oscillator, C1 and C2 are insulating capacitors, Dt t D2 is a rectifying diode, and C3 is a filtering capacitor.

Dl, D2 and 03 constitute a demodulation circuit.

4tl12 is a reciprocating connection line.

A FET 1, a capacitor C1, and a diode D1 are connected in series between the input terminal N1 and the output terminal 0UT1 via a connection line l.

Further, an oscillator O8C and a capacitor C2 are connected in series between the input terminal N2 and the output terminal 0UT2 via a connecting line 12.

FET1. An output terminal O of an oscillator O8C is connected to the gate electrode of the FET2, and a diode D2 and a capacitor C3 are connected in parallel between lines 11 and 12, respectively.

The operation of the isolator shown in FIG. 1 constructed in this way will be explained as follows.

A DC input signal ■1 is supplied from the terminal IN1.

Then, when the oscillator 1O8C is operated, the complementary connected FET1. FET2 is alternately turned on by the oscillation output of the oscillator OSC.

Therefore, the input signal (1) is modulated into a rectangular wave signal IAC by the oscillation output of the oscillator O8C.

This rectangular wave signal IAC passes through capacitors C1 and C2, and then is demodulated by diodes D1 and D2 and capacitor C3 to become a DC output signal I2, which is taken out from output terminal 0UT1.

In other words, when FET1 is on, the input current ■1 is
It flows as T1-C1-Dl-OUTl-OUT2-C2.

When the output of the oscillator O8C becomes reverse phase and FET2 is turned on, the circuit of C1-FET2-C2-D2 is closed and the charges in the capacitors C1 and C2 are discharged.

In this way, the capacitors C1 and C2 are repeatedly charged and discharged to perform DC transmission.

In this case, FET1 and FET2 are alternately conductive, but
If the operation is performed ideally, the current signal does not bypass FET1, so a DC current I2 that is exactly equal to the DC input current ■1 and isolated by capacitors C1 and C2 can be obtained from the output terminals 0UT1 and 0UT2. be able to.

Such isolators can be used for various purposes, but
An example is shown in FIG.

In FIG. 2, E is a voltage source, RL is a load, AM is an amplifier, and T is a detection terminal.

The isolator shown in FIG. 1 is inserted at the dashed line IS.

In such a circuit of FIG. 2, lines i4. l≦
It is possible to realize a so-called two-wire insulated transmitter which is used for signal transmission and power transmission, and in which the detection end T side and the voltage source E side are insulated.

A common method is to use a transformer as a means for DC-insulating input and output signals.

However, since transformers essentially require an excitation current,
There is current loss between input and output.

When insulating input and output in industrial instruments such as the transmitter shown in Figure 2, the value of the output signal must be as proportional to the input signal value as possible, and the It would be a problem if there was current loss between input and output.

As mentioned above, FET1. shown in FIG. The switch composed of FET2 has no current loss like a transformer.

Therefore, in the isolated transmitter shown in FIG. 2 constructed using the DC-DC converter shown in FIG. 1, an isolated signal that is extremely accurately proportional to the signal obtained at the detection terminal T is supplied to the load RL be able to.

Furthermore, when using a transformer for insulation, the transformer is usually large compared to other electronic components, so the transformer becomes one bottleneck when converting the circuit into an IC.
The DC-DC converter shown in FIG. 1 does not have such problems and has the advantage that it can be easily integrated into an IC.

Furthermore, since the capacitor has no loss due to resistance, the isolator of the present invention has the advantage of being able to supply the input DC power to the load without reducing it.

The circuit shown in FIG. 1 is a half-wave type isolator, but FIG. 3 shows a double-wave modulation type isolator.

This dual-wave modulation type isolator consists of a field effect transistor FET1. shown in FIG. Along with FET2, a field effect transistor FET is used to set FET≦ to the oscillator O8C.
The input signal 11 is modulated by both waves, and the resulting modulated signal IAC' is sent to the diodes D1 . D2 and a diode B/ placed symmetrically thereto, 1) In addition to 2', double-wave rectification,
An isolated DC output signal I2 corresponding to an input signal 11 is obtained.

Such a dual-wave type isolator shown in Fig. 3 is an FE
T1 and FET'2. FET; and FET2 operate as a pair.

Now, FET1 and FET etc. are on, FET (and FET2
When FET1-C1 is off, the current route that flows through the circuit is FET1-C1.
-D, -0UT1-OUT2-D knee c2-FET4-
It becomes osc.

When the phase is reversed, FET'-C-D'-0UT-OUT2-
D2-C11211 Flows with FET2-O8C.

In addition, in Fig. 3, the Akatsuki capacitors C4, C'4 and the diode Dat D4 are used for level shifting due to the use of a jump cushion type FET, and the Zener diode DZ is used to adjust the input voltage and load. This is provided to prevent the voltage applied to the oscillator O8C from changing significantly depending on conditions.

FIG. 4 is an electrical connection diagram showing still another embodiment of the present invention.

The isolator shown in FIG. 1 connects an oscillator O8C for driving FET1 to FET2 to a reciprocating connection line 11. The isolator in Fig. 4 is connected to the oscillator O.
8C is connected to connection lines 131 and 132 in parallel.

In the oscillator parallel type isolator of FIG. 4, the input terminals IN1. ■The voltage Vi supplied to N2 is FET1. After being modulated by FET2, capacitor C1
, C2 to the demodulator and an isolated voltage ■ proportional to ■1 from the output terminal 0UT1.

is taken out.

The oscillator parallel type converter shown in FIG. 4 is suitable for use as an isolator when, for example, an isolated power supply is provided to an amplifier.

As is clear from the above description, according to the present invention, a two-wire isolator with little current or voltage loss between input and output can be realized with an extremely simple configuration.

[Brief explanation of the drawing]

FIG. 1 is an electrical connection diagram showing one embodiment of the isolator of the present invention, FIG. 2 is a diagram showing an application example of the isolator of the present invention, and FIGS. 3 and 4 are respective examples of other embodiments of the present invention. It is an electrical connection diagram showing. O20...Oscillator, FET...Field effect transistor, C1, C2...Insulating capacitor, Dl. D2. C3...Demodulator.

Claims (1)

[Scope of utility model registration request] A pair of complementary semiconductor switching elements connected in series and parallel to the reciprocating connection lines, a pair of capacitors each connected in series to the reciprocating connection lines, a pair of rectifying diodes and an F-wave capacitor. a demodulation circuit connected to the output side of the pair of capacitors, the input DC signal is modulated by the pair of semiconductor switch elements driven by an oscillator, and the modulated signal is demodulated via both the capacitors. A two-wire isolator that is demodulated by a circuit.