JP6971018B2 - Insulated signal conversion circuit, isolated signal converter, and circuit board - Google Patents

Description

The present invention relates to an isolated signal conversion circuit, an isolated signal conversion device, and a circuit board.

Conventionally, an optical isolator (isolated signal conversion circuit) that insulates between a primary side circuit and a secondary side circuit and transmits a signal from the primary side circuit to a secondary side circuit is known. For example, there is an optical isolator using a photocoupler including a light emitting unit and a light receiving unit (see, for example, Patent Document 1). In such an optical isolator, the light emitting diode, which is a light emitting diode, is blinked by an input signal from an input terminal inside the photocoupler, and the lighting state of the light emitting diode is detected by the light receiving unit, whereby the above input signal is electrically generated. Converts to a signal and outputs from the output terminal.

For example, the light emitting diode of an optical isolator begins to emit light when the forward voltage exceeds the threshold voltage (about 1.0 V). Further, the amount of light at that time increases with an increase in the forward current, and the light receiving unit receives a predetermined amount of light. In this way, since the optical isolator sends and receives signals with light, the primary side / secondary side circuits are physically isolated, so noise (common mode noise) resistance generated between the primary side / secondary side circuits is tolerated. Is high, and is used in, for example, monitoring devices.

Japanese Unexamined Patent Publication No. 06-283991

However, noise may occur, and a forward voltage that exceeds the forward threshold voltage of the light emitting diode may be applied to the light emitting portion of the photocoupler, and the noise may be detected as a signal. Further, since the optical isolator has a very high time response characteristic, even pulse noise having a relatively short pulse width such as switching noise or noise containing a high frequency component may be erroneously detected.

The present invention has been made in consideration of the above circumstances, and provides an isolated signal conversion circuit, an isolated signal conversion device, and a circuit board capable of suppressing false detection of a signal caused by noise. With the goal.

In order to solve the above problems, in the isolated signal conversion circuit of the present invention, a second frequency is defined lower than the first frequency, and an electric signal having a frequency component lower than the second frequency is supplied. An isolated signal conversion circuit, the light emitting element that emits light in response to an electric signal having a frequency component lower than the first frequency , and the light emitting element in order to bypass the frequency component exceeding the second frequency. includes a capacitive element connected in parallel, the capacitance value of the capacitor element, wherein the extent that the light emitting element does not respond to a second electrical signal having a frequency component exceeding a frequency, frequencies above the second frequency have been determined the electrical signal components to attenuate, the include a second 100 kilohertz in frequency components above the frequency, characterized in that.

Further, another isolated signal conversion circuit of the present invention forms a parallel circuit in which the pair of the light emitting element and the capacitive element are connected in parallel to each other, and the signal source of the supplied electric signal and the parallel circuit. that the series impedance component connected in series in a closed circuit, the capacitance value, Ru is determined based on the impedance value that varies at a frequency component of at least the series impedance component Empire.

Another insulated signal conversion circuit of the present invention, the current flowing through the amplitude of the voltage of the electrical signal output from the pre-SL signal source, to the light emitting element depends on the voltage drop due to the forward voltage of the light emitting element The magnitude of the impedance does not exceed the allowable current value of the light emitting element , and the frequency characteristic of the impedance depending on the second frequency, the impedance value, and the capacitance value is superimposed on the supplied electric signal. the size of the 10 0 key Roger Tsu frequency components are to meet that attenuates to less than one 50 minutes, the ratio of the impedance depends on the capacitance value and the impedance value of the series impedance component is determined , Characterized by that.

Further, in the other isolated signal conversion circuit of the present invention, when the closed circuit is open, the second frequency applied to the light emitting element is set by the circuit formed by the capacitance between the sheaths of the multi-core cable. The voltage division ratio between the impedance value of the capacitive element and the impedance value of the series impedance component with respect to the frequency component exceeding the second frequency so that the amplitude of the voltage of the frequency component exceeding the frequency does not exceed the forward voltage of the light emitting element. Is determined.

Further, the isolated signal conversion device of the present invention is an isolated signal conversion device in which a second frequency is defined lower than the first frequency and an electric signal having a frequency component lower than the second frequency is supplied. The light emitting element that emits light in response to the electric signal of the frequency component lower than the first frequency and the light emitting element connected in parallel to the light emitting element in order to bypass the frequency component exceeding the second frequency. comprising a substrate comprising a capacitive element, the element, the capacitance value of the capacitor element, wherein the extent that the light emitting element does not respond to a second electrical signal having a frequency component exceeding a frequency, frequencies above the second frequency have been determined the electrical signal components to attenuate, the include a second 100 kilohertz in frequency components above the frequency, characterized in that.

Further, the circuit board of the present invention is a circuit board in which a second frequency is defined lower than the first frequency and an electric signal having a frequency component lower than the second frequency is supplied . A light emitting element that emits light in response to an electric signal having a frequency component lower than the frequency of 1 is mounted on the first connection portion, and is connected in parallel to the light emitting element in order to bypass the frequency component exceeding the second frequency. capacitive element to be is mounted on the mold package of the second connecting portion or the light emitting element, wherein the impedance element that limits the current flowing through the light emitting element is mounted on the third connecting portion, the capacitance value of the capacitive element is said to the extent that the light emitting element does not respond to a second electrical signal having a frequency component exceeding frequency, have been determined to attenuate electrical signals of the frequency components above said second frequency, said second It is characterized in that 100 kilohertz is contained in the frequency component exceeding the frequency of.

In the present invention, it is possible to suppress erroneous detection of a signal caused by noise.

FIG. 1 is a block diagram for explaining a configuration example of a monitoring system including an isolated signal conversion circuit according to the first embodiment. It is a figure which shows the relationship between the frequency range which an optical isolator 12 responds, and the frequency range which limits a frequency band by a capacitor 13. It is a figure which shows an example of the current-voltage characteristic of an optical isolator 12. It is a figure for demonstrating the frequency characteristic data of each impedance in a different capacitor. It is a block diagram for demonstrating the configuration example of the monitoring system including the isolated signal conversion circuit in 2nd Embodiment. It is a block diagram for demonstrating the structural example of the isolated signal conversion apparatus in 3rd Embodiment. It is a block diagram for demonstrating the structural example of the isolated signal conversion apparatus in 4th Embodiment.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
First, as a first embodiment, FIG. 1 is a block diagram for explaining a configuration example of a monitoring system including an isolated signal conversion circuit according to the first embodiment. The monitoring system 100 shown in FIG. 1 includes an isolated signal conversion circuit 1 as an example of a monitoring device and a monitored device (monitored device) 2.

The isolated signal conversion circuit 1 shown in FIG. 1 includes two terminals 10-1 and 10-2 connected to the monitored device 2, a first resistor (current limiting resistor r) 11, an optical isolator 12, and an optical isolator 12. It includes a capacitor (capacitive element) 13, a second resistor (R) 14, an information transfer unit 15, and a power supply voltage Vb1.

The first resistor 11 is an impedance element that limits the current flowing through the set of the optical isolator 12 and the capacitor 13. Further, the first resistor 11 has an impedance value of a main value with respect to the impedance value of the series impedance component with respect to the optical isolator 12.

The optical isolator 12 is a semiconductor device including a light emitting diode (light emitting element) 12a and an optical transistor (light receiving element) 12b, and converts light into an electric signal. The light emitting diode 12a emits light in response to a frequency component lower than the first frequency of the input electric signal. For example, the light emitting diode 12a irradiates light when a voltage exceeding about 1 V is applied as a signal having a frequency component lower than the first frequency. The optical transistor 12b receives the light from the light emitting diode 12a, converts the amount of received light into a current value, and amplifies the light received by the transistor to increase the output signal level. The optical isolator 12 is, for example, a photo coupler, a photo relay, a photo triac, or the like.

Here, when a voltage is applied, the capacitor 13 stores an electric charge according to the voltage, but in the first embodiment, it is used so as to form a band limiting filter of a frequency component. FIG. 2 is a diagram showing the relationship between the frequency range to which the optical isolator 12 responds and the frequency range in which the frequency band is limited by the capacitor 13. The horizontal axis of FIG. 2 indicates the frequency f, and the vertical axis indicates the gain G (frequency response).

In the example of FIG. 2, the optical isolator 12 responds to a signal having a frequency (first frequency) f1 or less. By providing the capacitor 13, the frequency band exceeding the frequency (second frequency) f2 is limited. For example, the capacitor 13 is set with a predetermined capacitance value so as not to respond to a frequency component having a frequency f2 lower than the frequency f1 to which the light emitting diode 12a responds in the input electric signal.

The positive pole side of the power supply voltage Vb1 is connected to the outside via terminals 10-2, and the negative pole side is connected to the cathode of the light emitting diode 12a. Further, the power supply voltage Vb1 is a voltage sufficient to pass a current through the closed circuit. The second resistor 14 is a pull-down resistor for digital signalization. The information transfer unit 15 is a unit that transfers an electric signal converted by an optical isolator 12 to an IC (Integrated Circuit), an external device, or the like. The isolated signal conversion circuit 1 may not include the information transfer unit 15.

The isolated signal conversion circuit 1 described above is connected as follows, for example. The anode of the light emitting diode 12a is connected to the terminal 10-1 via the first connection line (alarm line) L1. A first resistor 11 is interposed in the first connection line L1 so as to be in series. The cathode of the light emitting diode 12a is connected to the terminal 10-2 via the second connection line (common line) L2. The power supply voltage Vb1 is inserted in series with the second connection line L2, and the positive pole side of the power supply voltage Vb1 is connected to the terminal 10-2. In the following description, if necessary, a set of a signal source of an input electric signal, an optical isolator 12, and a capacitor 13 may be described as a closed circuit.

Further, in the isolated signal conversion circuit 1, a power supply Vcc is applied to one end of the optical transistor 12b of the optical isolator 12, and the other end is grounded via a second resistor 14. The information transfer unit 15 may be connected to the other end of the above.

Further, in the first embodiment, the capacitor 13 is connected in parallel to the light emitting diode 12a of the optical isolator 12. For example, between the first connection line L1 connected to the terminal 10-1 and the second connection line L2 connected to the terminal 10-2, or between the first connection line L1 and GND. When a noise voltage is generated due to stray capacitance of wiring or the like, the voltage is divided by the impedance ratio between the first resistor 11 which is a current limiting resistor and the capacitor 13. For example, when the impedance of the first resistor 11 is, for example, about 3 kΩ, and the impedance of the capacitor 13 in the frequency component corresponding to the frequency of noise is, for example, about 30 Ω, the impedance ratio is 100: 1.

By providing the capacitor 13 in this way, the voltage generated due to the noise applied to both ends of the light emitting diode 12a is reduced, and the voltage is suppressed to be equal to or lower than the forward threshold voltage of the light emitting diode 12a, which is caused by the noise. The light emission of the light emitting diode 12a can be suppressed.

In the isolated signal conversion circuit 1 shown in FIG. 1, the noise voltage generated in the first connection line L1 is the voltage Vr due to the voltage drop of the first resistor 11 and the capacitor 13 connected in parallel to the light emitting diode 12a. The voltage is divided between the terminals and the voltage Vc. By appropriately determining this voltage division ratio, it is possible to prevent a current due to a voltage caused by noise from flowing through the light emitting diode 12a and causing the light emitting diode 12a to emit light erroneously.

For example, the impedance of the first resistor 11 is selected to be about 2 kΩ in consideration of the control power supply voltage (for example, about 10 V) and the recommended forward current of the light emitting diode 12a (for example, about 10 mA or less). Here, the If-Vf characteristics of the optical isolator 12 used in the isolated signal conversion circuit 1 will be described with reference to the drawings.

FIG. 3 is a diagram showing an example of the current-voltage characteristics of the optical isolator 12. In the example of FIG. 3, the horizontal axis represents the forward voltage VF (V), and the vertical axis represents the forward current IF (mA). According to the example of FIG. 3, it can be seen that the forward voltage VF is about 1 V. Further, as the target noise, a noise voltage of 100 (Vp ₋ p) and a noise frequency of 100 kHz are assumed. In this case, the maximum voltage applied to the light emitting diode 12a in the forward direction due to the noise voltage is about 50 (V ₀₋ p). When a current flows through the capacitor 13, it is divided into Vr and Vc by the first resistor (current limiting resistor r) 11 and the capacitor 13.

In the first embodiment, in order not to pass a current through the light emitting diode 12a, it is necessary to set Vc to about 1V or less. Therefore, the capacitor 13 needs to have a ratio of the resistance value of the first resistor 11 to the impedance of the capacitor 13 (for example, about 100 kHz) of 50: 1 or less.

Therefore, for example, when the impedance of the first resistor 11 is about 2 kΩ, the impedance of the capacitor 13 in the frequency range that limits the signal needs to be about 40 Ω or less. Here, using two capacitors having different impedance characteristics, the frequency characteristic data of each impedance will be described with reference to the drawings.

FIG. 4 is a diagram for explaining frequency characteristic data of each impedance in different capacitors. In the examples of FIGS. 4A and 4B, the horizontal axis represents the frequency and the vertical axis represents the impedance value (Ω). The curve 30 at the upper side of each of the graphs of FIGS. 4A and 4B shows the capacitance of each capacitor at a frequency of 40 Hz to 5 MHz, and the curve 31 at the lower side of the graph shows the frequency of each capacitor at 40 Hz. It shows the magnitude of impedance at ~ 5MHz.

Here, referring to FIGS. 4A and 4B, it can be seen that the impedance of the capacitor has a characteristic that it decreases as the frequency increases. For example, in FIGS. 4 (A) and 4 (B), the impedance at a frequency of 100 kHz is about 52.2 Ω in the example of the capacitor corresponding to FIG. 4 (A), and the impedance of the capacitor corresponding to FIG. 4 (B). In the example, it is about 19.2Ω. From their comparison, it is preferable that the capacitor 13 used in the isolated signal conversion circuit 1 in the first embodiment is a capacitor having the characteristics of FIG. 4 (B) lower than about 40Ω.

As described above, the capacitance value of the capacitor 13 is in series with respect to the set of the optical isolator 12 and the capacitor 13 in the closed circuit including the signal source of the input electric signal, the optical isolator 12, and the capacitor 13. It is determined based on the impedance value of the impedance component. Further, the impedance value of the series impedance component is determined based on, for example, the amplitude of the electric signal output from the signal source, the forward voltage of the optical isolator 12, and the allowable current value of the capacitor.

Further, in the first embodiment, as the above-mentioned closed circuit, a series impedance element (first resistor 11) forming a series impedance component, a set of an optical isolator 12 and a capacitor 13, and a power supply for passing a current through the closed circuit. And at least may be included. In this case, in the closed circuit, the current value from the power supply is adjusted according to the state of the signal source to generate an electric signal. As described above, according to the first embodiment, it is possible to prevent the isolated signal conversion circuit 1 from malfunctioning due to noise.

Further, the monitored device 2 has terminals 20-1 and 20-2 connected corresponding to terminals 10-1 and 10-2 of the isolated signal conversion circuit 1 as a monitoring device, and an abnormal signal contact (abnormal signal contact). It has an alarm contact) 21. The isolated signal conversion circuit 1 monitors the operating state of the monitored device 2 by detecting the state of the abnormal signal contact 21. For example, the monitored device 2 keeps the abnormal signal contact 21 open in normal times when there is no abnormality in the operating state, and closes the abnormal signal contact 21 when an abnormality is detected in the operating state. In the above case, the current does not flow in the closed circuit including the abnormal signal contact 21 in normal times, but the current flows in the abnormal state. However, as described above, when the isolated signal conversion circuit 1 is affected by noise, a current flows through the closed circuit even though the abnormal signal contact 21 is not closed.

The above description of the abnormal signal contact 21 in the monitored device 2 shows an example, and may indicate the control state of the monitored device 2, and is a logic corresponding to the opening and closing of the contact signal. Is not limited to the above, and can be appropriately determined according to the configuration.

The monitored device 2 may include, for example, a power supply device such as a DC power supply device or a UPS (Uninterruptible Power Supply, uninterruptible power supply device). Further, a power supply facility such as a DC power supply device or UPS may be a source of noise due to its operation. Even in the above case, in the monitoring system 100, the influence of noise generated by the operation of the power supply equipment such as the DC power supply device and UPS can be suppressed by the above-mentioned isolated signal conversion circuit 1. Further, in the case of the monitoring system 100, the information transfer unit 15 may transfer the output data (for example, the monitoring result) in the isolated signal conversion circuit 1 to the monitoring center or the like.

According to the first embodiment described above, the optical isolator 12 becomes noise by adding the capacitor 13 to the light emitting diode 12a of the optical isolator 12 used for detecting the state of the contact signal of the isolated signal conversion circuit 1. It is possible to prevent unnecessary switch operation by the voltage. As a result, even when a large-capacity inverter device or the like is used and the monitoring device is used in a situation where the electromagnetic environment is bad, unnecessary operation of the monitoring device (isolated signal conversion circuit 1) can be suppressed. Can be done.

<Second embodiment>
Next, the second embodiment will be described with reference to the drawings. In the embodiments shown below, the same components as those of the above-described embodiments will be designated by the same reference numerals, and specific description thereof will be omitted here. FIG. 5 is a block diagram for explaining a configuration example of a monitoring system including an isolated signal conversion circuit according to a second embodiment. The monitoring system 200 shown in FIG. 5 includes an isolated signal conversion circuit 3 as an example of a monitoring device, and a monitored device (monitored device) 4.

The isolated signal conversion circuit 3 shown in FIG. 5 includes a terminal 10-1 connected to the monitored device 4, a first resistor (current limiting resistor r) 11, an optical isolator 12, and a capacitor (capacitor element) 13. A second resistor (R) 14, an information transfer unit 15, and a power supply voltage Vb1 are provided.

Compared with the first embodiment described above, the second embodiment does not have the terminal 10-2, and the positive pole side of the power supply voltage Vb1 is connected to GND via a common wire. Further, in the monitored device 4, one end of the abnormal signal contact 21 is connected to the GND. As shown in the second embodiment, the isolated signal conversion circuit 3 does not need to individually connect the second connection line L2 to the monitored device 4 side, but the isolated signal in the first embodiment described above. Similar to the conversion circuit 1, it is possible to prevent malfunction due to noise of the electric signal input from the terminal 10-1.

<Third embodiment>
Next, a third embodiment will be described. In the third embodiment, the capacitors 13 in the first and second embodiments described above are attached to the outside of the isolated signal conversion circuit, and a substrate including each configuration as an element (for example, a printed circuit board, a semiconductor substrate, etc.). An isolated signal conversion device including the above will be described. The isolated signal conversion device can replace the isolated signal conversion circuits 1 and 3 in the monitoring systems 100 and 200 described above. Therefore, in the following description, the description of the monitored device in the monitoring system will be omitted, and the portion of the isolated signal conversion device will be described with reference to the drawings.

FIG. 6 is a block diagram for explaining a configuration example of the isolated signal conversion device according to the third embodiment. The isolated signal conversion device 300 shown in FIG. 6 includes an isolated signal conversion circuit 5 and a frequency band limiting unit 6. The isolated signal conversion circuit 5 has two terminals 10-1 and 10-2, a first resistor (current limiting resistor r) 11, an optical isolator 12, a second resistor (R) 14, and information transfer. It includes a unit 15 and a power supply voltage Vb1. Further, the frequency band limiting unit 6 includes two terminals 60-1 and 60-2 and a capacitor (capacitive element) 61.

The third embodiment is a method in which the frequency band limiting unit 6 is externally installed so as to be connected in parallel to the terminals 10-1 and 10-2 in the vicinity of the isolated signal conversion circuit 5. As shown in FIG. 6, a capacitor 61 is externally attached between the terminal 10-1 and the terminal 10-2 in the vicinity of the terminal 10-1 and the terminal 10-2 of the isolated signal conversion circuit 5. The capacitor 61 is, for example, the same as the above-mentioned capacitor 13, but is not limited thereto. With the isolated signal converter 300 in the third embodiment, for example, the impedance of the terminal 10-1 with respect to the terminal 10-2 can be lowered, and the noise voltage applied to the terminal 10-1 and the terminal 10-2 is suppressed. be able to.

When the isolated signal conversion device 300 is applied to the above-mentioned monitoring system, the two terminals 60-1 and 60-2 of the frequency band limiting unit 6 are, for example, the terminals 20-1 of the above-mentioned monitoring target device 2. , 20-2.

As described above, in the third embodiment, by suppressing the voltage applied to the light emitting diode 12a, it is possible to suppress light emission (malfunction) due to the influence of noise of the light emitting diode 12a.

<Fourth Embodiment>
Next, the fourth embodiment will be described with reference to the drawings. FIG. 7 is a block diagram for explaining a configuration example of the isolated signal conversion device according to the fourth embodiment. The isolated signal conversion device 400 shown in FIG. 7 includes an isolated signal conversion circuit 7 and a frequency band limiting unit 8. Compared with the isolated signal conversion circuit 5 in the third embodiment described above, the isolated signal conversion circuit 7 does not have the terminal 10-2 and has a positive pole of the power supply voltage Vb1. The side is connected to GND via a common line. Further, with respect to the frequency band limiting unit 8, one end of the capacitor 61 is connected to the GND as compared with the frequency band limiting unit 6 described above.

When the isolated signal conversion device 400 is applied to the above-mentioned monitoring system, the terminal 60-1 of the frequency band limiting unit 8 is connected to, for example, the terminal 20-1 of the above-mentioned monitoring target device 4. Since the other configurations are the same as those of the third embodiment described above, the specific description thereof will be omitted here.

The fourth embodiment is a method in which the frequency band limiting unit 6 is externally installed so as to be connected in parallel to the terminals 10-1 and GND in the vicinity of the isolated signal conversion circuit 5. As shown in FIG. 7, by externally attaching a capacitor 61 between the terminal 10-1 and the GND in the vicinity of the terminal 10-1 of the isolated signal conversion circuit 5, the first connection line L1 is connected to the GND. The impedance can be lowered, and the noise voltage applied to the first connection line L1 and GND can be suppressed. Therefore, it is possible to suppress light emission (malfunction) due to the influence of noise of the light emitting diode 12a.

In the third and fourth embodiments described above, the optical isolator 12 that emits light in response to a frequency component lower than the first frequency of the input electric signal and the second frequency lower than the first frequency are used. Although an isolated signal conversion device having a capacitance value determined not to respond to a frequency component exceeding a frequency component and having a substrate including a capacitor connected in parallel to the light emitting diode 12a of the optical isolator 12 as an element is described. The scope of application of the present invention is not limited to this. For example, the light emitting diode 12a described above is mounted on the first connection portion, the capacitor 13 described above is mounted on the second connection portion, and the first resistor 11 that limits the current flowing between the light emitting diode 12a and the capacitor 13 is provided. It is mounted and has the same effect on a circuit board or the like in which the light emitting diode 12a and the capacitor 13 are connected in parallel and the light emitting diode 12a and the first resistor are connected in series.

According to each of the above-described embodiments, it is possible to suppress erroneous detection of a signal due to noise. Further, all or a part of each of the above-described embodiments may be combined with other embodiments. Further, as a method of making it less susceptible to malfunction due to noise, for example, the voltage of the control power supply that applies a voltage to the optical isolator 12 is increased to increase the resistance value of the protection resistor of the light emitting diode, and the first resistance (current limiting resistor) is increased. r) There is a method of further increasing the voltage division ratio between 11 and the capacitor 13. Further, as another method, there is a method of selecting a capacitor 13 having a lower impedance in the frequency range of the frequencies f1 to f2 described above. Therefore, for example, by combining these methods with each of the above-described embodiments, erroneous detection of a signal due to noise can be further suppressed. Further, as another embodiment, the optical isolator 12 in the isolated signal conversion circuits 1 and 3 and the isolated signal converters 300 and 400 described above may be configured as a molded component including the capacitor 13.

Although the embodiments for carrying out the present invention have been described above using the embodiments, the present invention is not limited to these embodiments, and various modifications and substitutions are made without departing from the gist of the present invention. Can be added.

1, 3, 5, 7 Insulated signal conversion circuit 2, 4 Monitored device 6, 8 Frequency band limiting unit 10, 20, 60 Terminal 11 First resistor 12 Optical isolator 12a Light emitting diode 12b Optical transistor 13, 61 Capacitor 14 Second resistor 15 Information transfer unit 21 Abnormal signal contact (alarm contact)
100, 200 Monitoring system 300, 400 Insulated signal converter

Claims (6)

An isolated signal conversion circuit in which a second frequency is defined lower than the first frequency and an electric signal having a frequency component lower than the second frequency is supplied.
A light emitting element that emits light in response to an electric signal having a frequency component lower than the first frequency,
A capacitive element connected in parallel to the light emitting element in order to bypass a frequency component exceeding the second frequency, and a capacitive element.
Including
The capacitance value of the capacitive element is determined so as to attenuate the electric signal of the frequency component exceeding the second frequency so that the light emitting element does not respond to the electric signal of the frequency component exceeding the second frequency. hand,
The frequency component above the second frequency includes 100 kHz.
Insulated signal conversion circuit. A parallel circuit in which the pair of the light emitting element and the capacitive element are connected in parallel to each other is formed.
The signal source of the supplied electric signal, the parallel circuit, and the series impedance component are connected in series in a closed circuit.
The capacitance value is determined based on an impedance value that fluctuates at least with a frequency component of the series impedance component.
The isolated signal conversion circuit according to claim 1. The magnitude of the current flowing through the light emitting element, which depends on the amplitude of the voltage of the electric signal output from the signal source and the voltage drop due to the forward voltage of the light emitting element, does not exceed the allowable current value of the light emitting element. Moreover, the frequency characteristic of the impedance depending on the second frequency, the impedance value, and the capacitance value is 1/50 of the magnitude of the frequency component of the 100 kilohertz superimposed on the supplied electric signal. The ratio of the impedance value of the series impedance component to the impedance depending on the capacitance value is determined so as to satisfy the following attenuation.
The isolated signal conversion circuit according to claim 2. The closed circuit
With the series impedance component
With the parallel circuit
A power supply that allows current to flow through the closed circuit,
Including at least
The current value from the power supply is adjusted according to the state of the signal source to generate the electric signal.
The isolated signal conversion circuit according to claim 2 or 3. An isolated signal conversion device in which a second frequency is set lower than the first frequency and an electric signal having a frequency component lower than the second frequency is supplied.
A light emitting element that emits light in response to an electric signal having a frequency component lower than the first frequency,
A capacitive element connected in parallel to the light emitting element in order to bypass a frequency component exceeding the second frequency, and a capacitive element.
Equipped with a board that includes the elements
The capacitance value of the capacitive element is determined so as to attenuate the electric signal of the frequency component exceeding the second frequency so that the light emitting element does not respond to the electric signal of the frequency component exceeding the second frequency. hand,
The frequency component above the second frequency includes 100 kHz.
Insulated signal converter. A circuit board in which a second frequency is defined lower than the first frequency and an electric signal having a frequency component lower than the second frequency is supplied.
A light emitting element that emits light in response to an electric signal having a frequency component lower than the first frequency is mounted on the first connection portion.
A capacitive element connected in parallel to the light emitting element in order to bypass a frequency component exceeding the second frequency is mounted in the second connection portion or the mold package of the light emitting element.
An impedance element that limits the current flowing through the light emitting element is mounted on the third connection portion.
The capacitance value of the capacitive element is determined so as to attenuate the electric signal of the frequency component exceeding the second frequency so that the light emitting element does not respond to the electric signal of the frequency component exceeding the second frequency. hand,
The frequency component above the second frequency contains 100 kHz.
Circuit board.

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