Signal transmitting device

Abstract

A signal transmitting device (1) comprises: a primary-side winding (2); a first winding (10) magnetically coupled to the primary-side winding (2); and a second winding (20) magnetically coupled to the primary-side winding (2). The number of turns (N1) of the first winding (10) is different from the number of turns (N2) of the second winding (20). One end of the first winding (10) and one end of the second winding (20) are electrically connected to a reference electrically conductive path (90). The signal transmitting device (1) comprises: a first diode (11) that rectifies a voltage induced in the first winding (10); a first resistance unit (12) that is provided between a cathode (11B) of the first diode (11) and the reference electrically conductive path (90); a second diode (21) that rectifies a voltage induced in the second winding (20); and a second resistance unit (22) that is provided between a cathode (21B) of the second diode (21) and the reference electrically conductive path (90).

Description

signal transmission device

[0001] The present disclosure relates to a signal transmission device.

[0002] Patent Document 1 discloses a voltage detection circuit. This voltage detection circuit includes a first coil, a first diode, a first resistance component, a second diode, a second resistance component, and a voltage detection terminal. The first coil receives a voltage to be detected transmitted by a transformer. The first diode rectifies the voltage received by the first coil. The voltage rectified by the first diode is applied to the first resistance component. The second diode is arranged to have the same polarity as the first diode. The second resistance component is arranged in series with the second diode. The voltage detection terminal is provided at both ends of the combination of the second diode and the second resistance component. The first diode, the first resistance component, the second resistance component, and the second diode are connected to the first coil. The second resistance component and the second diode are arranged closer to the voltage detection terminal than the first diode with respect to the first coil. The temperature characteristics of the forward drop voltage of the first diode and the temperature characteristics of the forward drop voltage of the second diode are the same or almost the same.

[0003] Japanese Patent Application Laid-Open No. 2020-112484

[0004] A configuration such as that disclosed in Patent Document 1, which includes a first coil, a first diode, and resistance components (first resistance component and second resistance component), has problems that can lead to detection errors. The first problem is that the forward voltage drop of the first diode varies due to the current flowing through the first diode and the temperature of the first diode. The second problem is that the voltage drop across the first coil varies due to the temperature of the first coil, which affects the voltage drop across the resistance component. Regarding the first problem, Patent Document 1 provides a second diode to reduce the effect of the temperature characteristics of the forward voltage drop of the first diode. However, Patent Document 1 does not consider the second problem at all, leaving room for improvement in this regard.

[0005] The present disclosure aims to provide a technology that can reduce the influence of detection errors caused by diodes and windings on the secondary side of a transformer when detecting a voltage input to the primary side of the transformer on the secondary side.

[0006] The signal transmission device disclosed herein comprises a primary winding, a first winding magnetically coupled to the primary winding, and a second winding magnetically coupled to the primary winding, wherein the number of turns of the first winding is different from the number of turns of the second winding, one end of the first winding and one end of the second winding are electrically connected to a reference conductive path, and further comprises a first diode that rectifies a voltage induced in the first winding, a first resistor unit provided between the cathode of the first diode and the reference conductive path, a second diode that rectifies a voltage induced in the second winding, and a second resistor unit provided between the cathode of the second diode and the reference conductive path.

[0007] The technology disclosed herein can reduce the influence of detection errors caused by diodes and windings on the secondary side of a transformer when detecting a voltage input to the primary side of the transformer on the secondary side.

[0008] Fig. 1 is a configuration diagram of a signal transmission device according to a first embodiment, and Fig. 2 is a configuration diagram of a signal transmission device according to a second embodiment.

[0009] [Description of Embodiments of the Present Disclosure] In the following, embodiments according to the present disclosure are listed and exemplified.

[0010] [1] A signal transmission device comprising: a primary winding; a first winding magnetically coupled to the primary winding; and a second winding magnetically coupled to the primary winding, wherein the number of turns of the first winding is different from the number of turns of the second winding; one end of the first winding and one end of the second winding are electrically connected to a reference conductive path; and further comprising: a first diode that rectifies a voltage induced in the first winding; a first resistor unit provided between the cathode of the first diode and the reference conductive path; a second diode that rectifies a voltage induced in the second winding; and a second resistor unit provided between the cathode of the second diode and the reference conductive path.

[0011] The first voltage between the first diode and the first resistor reflects the voltage of the detection target applied to the primary coil. The second voltage between the second diode and the second resistor also reflects the voltage of the detection target applied to the primary coil. Because the number of turns of the first winding is different from the number of turns of the second winding, a difference may occur between the first voltage and the second voltage. Therefore, the signal transmission device described above makes it possible to calculate the voltage of the detection target applied to the primary coil based on the difference between the first voltage and the second voltage. Furthermore, by calculating the difference between the first voltage and the second voltage, the influence of the forward voltage drop across the second diode is reduced by the forward voltage drop across the first diode. Furthermore, by calculating the difference between the first voltage and the second voltage, the influence of the voltage drop across the second resistor is reduced by the voltage drop across the first resistor, and therefore the influence of the voltage drop across the second winding is reduced by the voltage drop across the first winding. In other words, according to the signal transmission device, when the voltage input to the primary side of the transformer is detected on the secondary side, the influence of detection errors caused by the second diode and the second winding can be reduced.

[0012] [2] The signal transmission device according to [1], wherein the number of turns N1 of the first winding, the number of turns N2 of the second winding, the resistance value R1 of the first resistor section, and the resistance value R2 of the second resistor section satisfy the condition of the following formula (A): (N1 / N2):(R1 / R2)=1:1.3 to 1.3:1 ... formula (A)

[0013] When the ratio of the resistance value R1 of the first resistor section to the resistance value R2 of the second resistor section is close to the ratio of the number of turns N1 of the first winding to the number of turns N2 of the second winding, the difference between the value of the current flowing through the first diode and the value of the current flowing through the second diode becomes small. As a result, the difference between the forward voltage drop of the first diode and the forward voltage drop of the second diode, which changes due to the current, becomes small. In addition, the difference between the voltage drop across the first resistor section and the voltage drop across the second resistor section, which is calculated by multiplying the current by the resistance value, also becomes small. In other words, a configuration that satisfies the condition of the above formula (A) can more reliably reduce the influence of detection errors caused by the second diode and the second winding.

[0014] [3] The signal transmission device according to [1] or [2], further comprising a detection unit that calculates a voltage to be detected that is applied to the primary winding based on a difference between a first voltage between the first diode and the other end of the first resistor and a second voltage between the second diode and the other end of the second resistor.

[0015] According to the signal transmission device, the detection unit can calculate the voltage to be detected that is applied to the primary winding.

[0016] [4] The signal transmission device according to [3], wherein the detection unit has an AD conversion unit and a calculation unit, wherein the AD conversion unit converts a first analog signal indicating a first voltage between the first diode and the first resistor unit into a first digital signal, and converts a second analog signal indicating a second voltage between the second diode and the second resistor unit into a second digital signal, and the calculation unit calculates the voltage to be detected that is applied to the primary winding based on the difference between the value indicated by the first digital signal and the value indicated by the second digital signal.

[0017] According to the signal transmission device, there is no need to provide an operational amplifier.

[0018] [5] The signal transmission device according to [3], further comprising an operational amplifier that amplifies and outputs a difference between a first voltage between the first diode and the first resistor and a second voltage between the second diode and the second resistor, and the detection unit calculates the voltage to be detected that is applied to the primary winding based on the signal output from the operational amplifier.

[0019] According to the signal transmission device, a signal indicating the difference between the first voltage and the second voltage is output from the operational amplifier, so that only one input terminal of the detection unit is required to determine the difference between the first voltage and the second voltage.

[0020] [Details of the embodiment of the present disclosure] 1. First embodiment A signal transmission device 1 according to the first embodiment shown in Fig. 1 is mounted on, for example, a vehicle. The signal transmission device 1 is a device that transmits, in an isolated manner, a signal indicating the voltage of a detection target.

[0021] The signal transmission device 1 includes a primary winding 2 , an iron core 3 , a first winding 10 , and a second winding 20 .

[0022] The primary winding 2 is wound around the iron core 3. The first winding 10 and the second winding 20 are each a secondary winding. The first winding 10 is wound around the iron core 3 and is magnetically coupled to the primary winding 2. The second winding 20 is wound around the iron core 3 and is magnetically coupled to the primary winding 2. The number of turns N1 of the first winding 10 is different from the number of turns N2 of the second winding 20. One end of the first winding 10 is electrically connected to a reference conductive path 90. One end of the second winding 20 is electrically connected to the reference conductive path 90. The reference conductive path 90 is, for example, ground.

[0023] The signal transmission device 1 includes a first diode 11 , a first resistor section 12 , a second diode 21 , a second resistor section 22 , and a detector 30 .

[0024] The first diode 11 rectifies the voltage induced in the first winding 10. The anode 11A of the first diode 11 is electrically connected to the other end of the first winding 10. The first resistor unit 12 is provided between the cathode 11B of the first diode 11 and the reference conductive path 90. One end of the first resistor unit 12 is electrically connected to the reference conductive path 90. The other end of the first resistor unit 12 is electrically connected to the cathode 11B of the first diode 11. A first voltage Vout1 is applied to a first conductive path 13 between the cathode 11B of the first diode 11 and the other end of the first resistor unit 12.

[0025] The second diode 21 rectifies the voltage induced in the second winding 20. The anode 21A of the second diode 21 is electrically connected to the other end of the second winding 20. The second resistor unit 22 is provided between the cathode 21B of the second diode 21 and the reference conductive path 90. One end of the second resistor unit 22 is electrically connected to the reference conductive path 90. The other end of the second resistor unit 22 is electrically connected to the cathode 21B of the second diode 21. A second voltage Vout2 is applied to a second conductive path 23 between the cathode 21B of the second diode 21 and the other end of the second resistor unit 22.

[0026] The detection unit 30 calculates the voltage Vin to be detected that is applied to the primary winding 2 based on the difference between the first voltage Vout1 and the second voltage Vout2. The detection unit 30 has a first input terminal 31, a second input terminal 32, an AD conversion unit 33, and a calculation unit 34.

[0027] The first input terminal 31 is electrically connected to the first conductive path 13, and receives the first voltage Vout1 from the first conductive path 13. The second input terminal 32 is electrically connected to the second conductive path 23, and receives the second voltage Vout2 from the second conductive path 23.

[0028] The AD converter 33 converts a first analog signal indicating the first voltage Vout1 input from the first input terminal 31 into a first digital signal, and converts a second analog signal indicating the second voltage Vout2 input from the second input terminal 32 into a second digital signal.

[0029] The calculation unit 34 calculates the voltage Vin to be detected that is applied to the primary winding 2, based on the difference between the value indicated by the first digital signal and the value indicated by the second digital signal. Specifically, the calculation is performed as follows.

[0030] The signal transmission device 1 includes a switch unit 40 and a signal output unit 41. The switch unit 40 is connected in series to the primary winding 2. The signal output unit 41 outputs an on / off signal with a predetermined duty ratio D to control the on / off of the switch unit 40. The duty ratio is the ratio of the on time to the period. As a result, a voltage based on the voltage Vin to be detected is applied to the primary winding 2, and voltages are induced in the first winding 10 and the second winding 20. As a result, the voltage Vin to be detected is reflected in the first voltage Vout1 of the first conducting path 13 and the second voltage Vout2 of the second conducting path 23.

[0031] The first voltage Vout1 is expressed by the following equation (1): Vout1=Vs1-Vf1 equation (1) where Vs1 is the voltage induced in the first winding 10. Vf1 is the forward voltage drop of the first diode 11.

[0032] The average value of Vs1 is expressed by the following equation (2): Vs1=Vin×D×(N1 / Np)+Is1×R1 (2) N1 is the number of turns of the first winding 10. Np is the number of turns of the primary winding 2. Is1 is the value of the current flowing through the first resistor section 12. R1 is the resistance value of the first resistor section 12.

[0033] The second voltage Vout2 is expressed by the following equation (3): Vout2=Vs2-Vf2 equation (3) where Vs2 is the voltage induced in the second winding 20. Vf2 is the forward voltage drop of the second diode 21.

[0034] The average value of Vs2 is expressed by the following equation (4): Vs2=Vin×D×(N2 / Np)+Is2×R2 (4), where N2 is the number of turns of the second winding 20. Is2 is the value of the current flowing through the second resistor section 22. R2 is the resistance value of the second resistor section 22.

[0035] From the above formulas (1) to (4), the following formula (5) can be derived: Vout2-Vout1=Vin×D×{(N2-N1) / Np}-Vf2+Vf1+Is2×R2-Is1×R1 (Formula (5))

[0036] As can be seen from the above equation (5), by calculating the difference between the second voltage Vout2 and the first voltage Vout1, the influence of the forward voltage drop Vf2 across the second diode 21 is reduced by the forward voltage drop Vf1 across the first diode 11. Furthermore, by calculating the difference between the second voltage Vout2 and the first voltage Vout1, the influence of the voltage drop across the second resistor unit 22 is reduced by the voltage drop across the first resistor unit 12, and therefore the influence of the voltage drop across the second winding 20 is reduced by the voltage drop across the first winding 10. In other words, by using equation (5), the detection unit 30 can calculate the voltage Vin to be detected in a manner that reduces the influence of detection errors caused by the second diode 21 and the second winding 20.

[0037] In particular, when the ratio of the resistance value R1 of the first resistor section 12 to the resistance value R2 of the second resistor section 22 is close to the ratio of the number of turns N1 of the first winding 10 to the number of turns N2 of the second winding 20, the difference between the value of the current flowing through the first diode 11 and the value of the current flowing through the second diode 21 becomes small. As a result, the difference between the forward voltage drop of the first diode 11 and the forward voltage drop of the second diode 21, which changes due to the current, becomes small. In addition, the difference between the voltage drop across the first resistor section 12 and the voltage drop across the second resistor section 22, which is calculated by multiplying the current by the resistance value, also becomes small. Therefore, a configuration that satisfies the condition of the following equation (A) can more reliably reduce the influence of detection errors caused by the second diode 21 and the second winding 20. (N1 / N2):(R1 / R2)=1:1.3 to 1.3:1 (Equation (A)) Furthermore, with a configuration that satisfies the condition of the following equation (B), the influence of detection errors caused by the second diode 21 and the second winding 20 can be more reliably reduced. (N1 / N2):(R1 / R2)=1:1 (Equation (B))

[0038] 2. Second Embodiment In the second embodiment, a configuration for calculating the difference between a first voltage and a second voltage using an operational amplifier will be described. Note that in the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0039] 2 includes a detection unit 230 and an operational amplifier 240 instead of the detection unit 30 of the first embodiment. In other respects, the signal transmission device 201 is the same as the signal transmission device 1 of the first embodiment.

[0040] The operational amplifier 240 has a first terminal 241, a second terminal 242, and a third terminal 243. The first terminal 241 is an inverting input terminal. The first conductive path 13 is electrically connected to the first terminal 241. The first voltage Vout1 is input to the first terminal 241 from the first conductive path 13. The second terminal 242 is a non-inverting input terminal. The second conductive path 23 is electrically connected to the second terminal 242. The second voltage Vout2 is input to the second terminal 242 from the second conductive path 23. The third terminal 243 is an output terminal. The operational amplifier 240 outputs an analog signal indicating the difference between the first voltage Vout1 and the second voltage Vout2 from the third terminal 243.

[0041] The detection unit 230 has an input terminal 231, an AD conversion unit 233, and a calculation unit 234. A signal output from a third terminal 243 is input to the input terminal 231. The AD conversion unit 233 converts the analog signal input from the third terminal 243 into a digital signal. The calculation unit 234 uses the value converted by the AD conversion unit 233 to calculate the voltage Vin to be detected that is applied to the primary winding 2.

[0042] As described above, according to the signal transmission device 201 of the second embodiment, a signal indicating the difference between the first voltage Vout1 and the second voltage Vout2 is output from the operational amplifier 240. Therefore, only one input terminal 231 of the detection unit 230 is required to determine the difference between the first voltage Vout1 and the second voltage Vout2.

[0043] <Other Embodiments> The present disclosure is not limited to the embodiments described above and in the drawings. For example, any combination of features of the above-described or below-described embodiments is possible within a range that does not contradict. Furthermore, any feature of the above-described or below-described embodiments may be omitted unless explicitly stated as essential. Furthermore, the above-described embodiments may be modified as follows.

[0044] Although the signal transmission device of the first embodiment is configured to include a detection unit, it may be configured not to include a detection unit. In a configuration not including a detection unit, for example, an operator may measure the first voltage and the second voltage, and the voltage to be detected may be calculated by an external calculation device using the measured values. Similarly, the signal transmission device of the second embodiment may be configured not to include a detection unit or an operational amplifier.

[0045] It should be noted that the embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present invention is not limited to the embodiments disclosed herein, and is intended to include all modifications within the scope indicated by the claims or within the scope equivalent to the claims.

[0046] REFERENCE SIGNS LIST 1...signal transmission device 2...primary side winding 3...iron core 10...first winding 11...first diode 11A...anode 11B...cathode 12...first resistance section 13...first conductive path 20...second winding 21...second diode 21A...anode 21B...cathode 22...second resistance section 23...second conductive path 30...detection section 31...first input terminal 32...second input terminal 33...AD conversion section 34...calculation section 40...switch section 41...signal output section 90...reference conductive path 201...signal transmission device 230...detection section 231...input terminal 233...AD conversion section 234...calculation section 240...operational amplifier 241...first terminal 242...second terminal 243...third terminal N1...number of turns of first winding N2...Number of turns of the second winding R1...Resistance value of the first resistor section R2...Resistance value of the second resistor section Vf1...Forward drop voltage Vf2...Forward drop voltage Vin...Voltage Vout1...First voltage Vout2...Second voltage

Claims

1. A signal transmission device comprising: a primary winding; a first winding magnetically coupled to the primary winding; and a second winding magnetically coupled to the primary winding, wherein the number of turns of the first winding is different from the number of turns of the second winding; one end of the first winding and one end of the second winding are electrically connected to a reference conductive path; and further comprising: a first diode that rectifies a voltage induced in the first winding; a first resistor unit provided between the cathode of the first diode and the reference conductive path; a second diode that rectifies a voltage induced in the second winding; and a second resistor unit provided between the cathode of the second diode and the reference conductive path.

2. The signal transmission device according to claim 1, wherein the number of turns N1 of the first winding, the number of turns N2 of the second winding, the resistance value R1 of the first resistor section, and the resistance value R2 of the second resistor section satisfy the condition of the following formula (A): (N1 / N2):(R1 / R2)=1:1.3 to 1.3:1 ... formula (A) 3. A signal transmission device according to claim 1 or claim 2, further comprising a detection unit that calculates the voltage to be detected that is applied to the primary winding based on the difference between a first voltage between the first diode and the other end of the first resistor and a second voltage between the second diode and the other end of the second resistor.

4. The signal transmission device according to claim 3, wherein the detection unit has an AD conversion unit and a calculation unit, wherein the AD conversion unit converts a first analog signal indicating a first voltage between the first diode and the first resistor unit into a first digital signal, and converts a second analog signal indicating a second voltage between the second diode and the second resistor unit into a second digital signal, and the calculation unit calculates the voltage to be detected that is applied to the primary winding based on the difference between the value indicated by the first digital signal and the value indicated by the second digital signal.

5. The signal transmission device according to claim 3, further comprising an operational amplifier that amplifies and outputs the difference between a first voltage between the first diode and the first resistor and a second voltage between the second diode and the second resistor, and the detection unit calculates the voltage to be detected that is applied to the primary winding based on the signal output from the operational amplifier.

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