JPH0669156B2 - Isolator using hole element - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an isolator using a Hall element for transmitting an analog signal containing a DC component between electrically isolated circuits, such as an input unit of a data processing device. Is used for.

<Prior art> Conventionally, as a method of transmitting an analog signal containing a DC component between electrically isolated circuits, a modulation circuit converts the analog signal into an AC signal, and the AC signal is transmitted by a transformer or a photocoupler. However, the method of returning to the original analog signal in the demodulation circuit was used.

However, this method requires a modulation circuit, a demodulation circuit, a transformer, and a photocoupler, which complicates the configuration and increases the cost, and has a drawback that the transmission bandwidth is narrow and the transmission accuracy is low. .

<Object of the Invention> The present invention has been made in view of the above circumstances, and an object thereof is to provide an isolator having a simplified structure and an improved response speed of transmission by using a Hall element. .

<Structure of the Invention> In the present invention, a first coil to which an analog signal is applied, and a Hall element that outputs a signal according to the strength of the magnetic field in the gap of the yoke around which the first coil is wound. ,
A first amplifier for amplifying the output signal of the Hall element,
A second coil wound around the yoke and to which an output signal of the first amplifier is applied via a resistor; and a second amplifier for amplifying a potential difference generated in the resistor to obtain an output signal. The second coil is wound around the yoke so that the current from the first amplifier flows in such a direction as to cancel the magnetic flux generated by the current flowing through the first coil. .

Example An example of the present invention will be described below.

FIG. 1 shows the structure of an isolator using a Hall element. The primary coil 1 is wound around the yoke 2, and an analog signal which is an input signal is applied to the terminals 3 and 4 of the primary coil 1. The yoke 2 further includes a feedback coil 5
Is wound.

The Hall element 6 is arranged in the gap 7 of the yoke 2.
The Hall element 6 generates a voltage signal according to the strength of the magnetic field of the gap 7. The high gain amplifier 8 is a hall element 6
Is amplified, and the output signal of the high gain amplifier 8 is applied to the feedback coil 5 via the resistor 9.

The low-gain high-band amplifier 10 amplifies the potential difference generated between the points at both ends of the resistor 9 and outputs an output signal to the terminal 11.

The operation of the above isolator will be described below.

When a current flows through the primary coil 1, a magnetic flux is generated and an electromotive force is generated in the Hall element 6. The output voltage of the Hall element 6 is amplified by the high gain amplifier 8 and a current flows through the feedback coil 5 through the resistor 9 to generate a magnetic flux. The current of the feedback coil 5 flows in a direction in which the magnetic flux generated in the feedback coil 5 cancels the magnetic flux generated by the primary coil 1. Since the amplification factor of the high gain amplifier 8 is large, the magnetic flux of the primary coil 1 and the magnetic flux of the feedback coil 5 are automatically balanced. Therefore, the current flowing through the primary coil 1 is always proportional to the current flowing through the feedback coil 5, and the operating point of the Hall element 6 is always kept at zero. As a result, the movement of the operating point due to the temperature of the Hall element 6 becomes irrelevant.

The high gain amplifier 8 that amplifies the output voltage of the Hall element 6 is
While the response speed is low, the output has a high final value accuracy with respect to the input. Therefore, at the point, a signal of a value flow component having a higher final value accuracy than the input analog signal is obtained.
Further, at the point, the signal of the AC component of the input analog signal induced in the feedback coil 5 by the change in the magnetic flux of the primary coil 1 is obtained.

A signal in which a DC component having a low response speed at this point but a high final value accuracy and an AC component having a high response speed at a point are combined is input to the low-gain high-bandwidth amplifier 10. Therefore,
The output of the amplifier 10 matches the input analog signal of the terminals 3 and 4 with high accuracy. Since the low-gain high-bandwidth amplifier 10 has a low gain, the response speed can be sufficiently increased.

2 (a) to (d) show signal waveforms of the main part of the above-mentioned circuit, (a) shows signal waveforms applied to terminals 3 and 4,
(B) is a point signal waveform, (c) is a point signal waveform,
(D) shows the output signal waveform of the amplifier 10, respectively. In the amplifier 10, the signal of the DC component at the point shown in (b) and the signal of the AC component at the point shown in (c) are combined,
The waveform shown in (d) is obtained. The output waveform of the amplifier 10 in (d) is almost equal to the waveform of the input analog signal in (a).

FIG. 3 shows a detailed circuit configuration of the above isolator.
Since the Hall element 6 is always in a state where the output is zero, it is not necessary to feed power from the constant current source. Therefore, the power supply to the hall element 6 is performed by the power source common to the high gain amplifier 8 and the low gain high bandwidth amplifier 10.

The movement of the zero point due to the temperature of the Hall element 6 is
Proportional to the terminal voltage of. Therefore, this terminal voltage is taken out as a correction value from the point and the point of the output terminal of the Hall element 6, and the current of the resistor group 12 in parallel with the Hall element 6 is changed according to this correction value, so that Perform the temperature correction of. FIG. 4 shows only this temperature correction circuit in a simplified form.

<Effects of the Invention> As described above, in the present invention, the isolator is mainly configured by the primary coil, the feedback coil, the Hall element, the high gain amplifier and the low gain amplifier, so that the configuration is simple and the cost is reduced. In addition, the transmission bandwidth can be increased to, for example, DC to 500 KHz by the low gain amplifier having a high response speed.
Further, since the feedback system is configured, the linearity is good and the transmission accuracy can be improved. Further, the temperature drift is small, and stable operation can be obtained against the fluctuation of the power supply voltage.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing the basic configuration of the embodiment of the present invention. FIG. 2 is a diagram showing operation waveforms of essential parts of the circuit of FIG. 1, FIG. 3 is a circuit diagram showing a detailed configuration of an embodiment of the present invention, and FIG. 4 is a partial circuit diagram of FIG. 1 …… Primary coil 2 …… Yoke 5 …… Feedback coil 6 …… Hall element 7 …… Gap 8 …… High gain amplifier 9 …… Resistance 10 …… Low gain high bandwidth amplifier 12 …… Resistance group

Claims (2)

[Claims] 1. A first coil to which an analog signal is applied, a Hall element for outputting a signal according to the strength of a magnetic field of a gap of a yoke around which the first coil is wound, and a Hall element of the Hall element. A first amplifier for amplifying an output signal, a second coil wound around the yoke and applied with an output signal of the first amplifier through a resistor, and a potential difference generated in the resistor are amplified. A second amplifier for obtaining an output signal is provided, and the second coil is wound so that the current from the first amplifier flows in such a direction as to cancel the magnetic flux generated by the current flowing through the first coil. An isolator that uses the Hall element that is manufactured. 2. An isolator using a hall element according to claim 1, further comprising a correction circuit for correcting the temperature of the zero point of the hall element according to the output voltage of the hall element. .