Transmitter and communication device

Abstract

A communication device 1 comprises a transmitter 2, an insulation part 3, a receiver 4, and a logic circuit 5. The transmitter 2 transmits a differential signal through the insulation part 3. When modulating an input signal on and off on the basis of a clock signal, signal generation units 11 and 12 set a signal being modulated to be a differential out-of-phase modulation signal if a self-diagnostic switching signal being inputted is inactive. When the self-diagnostic switching signal is active, the modulated signal is outputted to the differential signal line as a differential in-phase modulated signal for diagnostic use.

Description

Transmitters and communication devices CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-109628 filed on July 8, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a transmitter used for isolated communication, and a communication device that uses the transmitter and has a self-diagnosis function.

[0003] Generally, an isolator used in an isolated communication system for high-voltage equipment is composed of a multi-chip semiconductor device that transmits signals while the input and output sides are electrically isolated by an isolation element. Passive elements such as capacitors and transformers are used as isolation elements. Communication systems for high-voltage equipment are often performed in noisy environments. For example, the technology disclosed in Patent Document 1 is used as a communication method using differential signals that have high resistance to noise. Furthermore, self-diagnosis technologies for semiconductor communication circuits have been proposed in Patent Documents 2 to 4, for example.

[0004] U.S. Patent No. 8,451,032 U.S. Patent No. 5,585,091 U.S. Patent No. 6,227,170 U.S. Patent Publication No. 2012-507204

[0005] Patent Document 2 discloses a fault diagnosis device that superimposes an auxiliary signal on a transmitted main signal and separates the frequencies using a filter on the receiving side. This is said to enable detection of an open circuit in a communication path, a short circuit to a power supply, or a short circuit to ground, but does not disclose detection of a short circuit fault between both terminals of an isolation element.

[0006] Patent Document 3 discloses a device for detecting faults in differential communication, but this method requires at least three receivers, which increases manufacturing costs. Patent Document 4 discloses a method for transmitting signals using a DC signal included in an in-phase signal using a differential communication line as is. However, because isolated communication is capacitive or inductive coupling, DC signals cannot be transmitted.

[0007] The present disclosure has been made in consideration of the above circumstances, and its purpose is to provide a transmitter that can generate a signal for performing self-diagnosis, and a communication device that can detect a fault in an insulating part without requiring an additional receiving circuit.

[0008] According to the transmitter of claim 1, an electrical signal is transmitted through an insulating unit. When the modulated signal generator digitally modulates an input signal based on a clock signal, if the input self-diagnosis switching signal is inactive, the modulated signal generator converts the modulated signal into a differential out-of-phase modulated signal. On the other hand, if the self-diagnosis switching signal is active, the modulated signal is output to the differential signal line as a differential in-phase modulated signal for diagnosis.

[0009] With this configuration, when the receiver of the signal transmitted from the transmitter receives the diagnostic differential in-phase modulated signal, it can determine whether or not the insulating section has failed based on the demodulation results.

[0010] According to the transmitter of the second aspect, the modulated signal generating section performs on-off modulation as the digital modulation.

[0011] According to a third aspect of the present invention, a communication device includes the transmitter of the first or second aspect, a receiver that receives and demodulates the modulated signal transmitted by the transmitter, an isolation unit connected between the transmitter and receiver, and a receiving-side control unit. During self-diagnosis when the self-diagnosis switching signal is active, the receiving-side control unit determines whether the signal is normal or abnormal based on the signal demodulated by the receiver, and transmits the diagnosis result to a higher-level control device. When the receiver receives and demodulates the differential in-phase modulated diagnostic signal, the demodulation result differs depending on whether the isolation unit is normal or abnormal. This makes it possible to determine whether the isolation unit is faulty.

[0012] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a functional block diagram showing the configuration of a transmitter in a first embodiment, Fig. 2 is a diagram showing the configuration of the transmitter as a logic circuit, Fig. 3 is a functional block diagram showing the configuration of a communication device, Fig. 4 is a functional block diagram showing the configuration of a receiver, Fig. 5 is a waveform diagram showing an example of an input signal being modulated and demodulated to become an output signal, Fig. 6 is a flowchart showing processing by the communication device, Fig. 7 is a diagram showing waveforms demodulated at the receiving side when a differential signal and an in-phase signal are transmitted under normal conditions, Fig. 8 is a diagram showing waveforms demodulated at the receiving side when a differential signal is transmitted with an open circuit or short circuit fault in a capacitor, Fig. 9 is a diagram showing waveforms demodulated at the receiving side when an in-phase signal is transmitted with an open circuit or short circuit fault in a capacitor, Fig. 10 is a functional block diagram showing the configuration of a communication device in a second embodiment, and Fig. 11 is a flowchart showing processing by the communication device.

[0013] First Embodiment As shown in FIG. 3 , a communication device 1 of this embodiment includes a transmitter 2, an isolator 3, a receiver 4, and a logic circuit 5. The transmitter 2 digitally modulates an input signal based on a clock signal to generate a modulated signal, which is then transmitted to the receiver 4 via the isolator 3. A self-diagnosis switching signal is also input to the transmitter 2. The communication line between the transmitter 2, the isolator 3, and the receiver 4 is a differential signal line. If the self-diagnosis switching signal is inactive, the communication device 2 transmits the modulated signal as a differential out-of-phase modulated signal. On the other hand, if the self-diagnosis switching signal is active, the communication device 2 outputs the modulated signal to the differential signal line as a differential in-phase modulated signal for diagnosis. The receiver 4 demodulates the received signal and outputs it to the logic circuit 5.

[0014] As shown in Fig. 1, the transmitter 2 includes a differential signal / diagnostic signal generator 11, a modulated signal generator 12, and an output buffer 13. A clock signal and a self-diagnosis switch signal are input to the differential signal / diagnostic signal generator 11. Based on these signals, the differential signal / diagnostic signal generator 11 generates a differential signal used for normal communication and a diagnostic signal used for diagnosing the isolation unit 3. The modulated signal generator 12 performs on / off modulation of the input signal using the signal output from the differential signal / diagnostic signal generator 11, generates a modulated signal, and outputs it to the output buffer 13. The differential signal / diagnostic signal generator 11 also constitutes a modulated signal generator.

[0015] 2, the differential signal / diagnostic signal generator 11 is composed of NOT gates 14a and 14b, and NAND gates 15a to 15c, 16p, and 16m. The modulated signal generator 12 is composed of NAND gates 17p and 17m, and the output buffer 13 is composed of NAND gates 18p and 18m. The self-diagnostic switch signal is supplied to one input terminal of NAND gate 15b and, via NOT gate 14b, to one input terminal of NAND gate 15c.

[0016] The clock signal is applied to both input terminals of NAND gate 15a, the other input terminal of NAND gate 15b, and via NOT gate 14a to the other input terminal of NAND gate 15c. The output terminal of NAND gate 15a is connected to both input terminals of NAND gate 16p, and the output terminals of NAND gates 15b and 15c are connected to the input terminals of NAND gate 16m.

[0017] The output terminals of the NAND gates 16p and 16m are connected to the input terminals of the NAND gates 18p and 18m that constitute the output buffer 13 via one of the input terminals of the NAND gates 17p and 17m that constitute the modulated signal generating unit 12. An input signal is given to the other of the input terminals of the NAND gates 17p and 17m.

[0018] In the transmitter 2, when the self-diagnosis switching signal is at a low level where it is inactive, and when the input signal indicates a high level, the P output and M output from the output buffer 13 output clock signals that are out of phase with each other. On the other hand, when the self-diagnosis switching signal is at a high level where it is active, and when the input signal also indicates a high level, the P output and M output output clock signals that are in phase with each other.

[0019] As shown in Fig. 4, the receiver 4 includes a differential amplifier 21 and an envelope detector 22. As shown in Fig. 5, the digital modulation performed by the transmitter 2 is, for example, on-off modulation, and when the input signal is high level (H), the modulated signal becomes a differential, anti-phase modulated signal. In the receiver 4, the differential, anti-phase modulated signal is demodulated by the envelope detector 22 and a high-level signal is output.

[0020] As shown in Fig. 7, the insulating unit 3 is composed of an insulating element and a series circuit of two capacitors 23 and 24, which are electrostatic capacitance elements. In Fig. 7, the transmitter 2 is simply shown with only a transceiver symbol. The receiver 4 is shown as a receiver 21 including a differential amplifier, and a demodulator 25 and a comparator 26 that constitute an envelope detector 22.

[0021] Next, the operation of this embodiment will be described. The communication device 1 is shipped after inspecting the differential communication lines including the insulating unit 3. However, in consideration of the possibility that a failure may occur in the insulating unit 3 due to a cause not anticipated at the time of shipment, the communication device 1 of this embodiment is equipped with a function for self-diagnosing insulation failures in the field after shipment.

[0022] 6 is defined as a protocol of the communication device 1 and is executed after startup. Upon startup, the transmitter 2 transmits a communication signal H as a differential output. That is, the P output and the M output transmit a signal in opposite phases (S1). The logic circuit 5, which corresponds to the receiving-side control unit, determines whether the signal demodulated by the receiver 4 is at a high level (H) (S2).

[0023] If a signal H is received here (YES), the sequence proceeds to the next step, where the transmitter 2 transmits a diagnostic signal. That is, it transmits a signal that makes the P output and M output in phase (S3). The logic circuit 5 determines whether the signal demodulated by the receiver 4 is at a low level (L) (S4). If a signal L is received here (YES), it means that the isolated communication is normal, and the process ends.

[0024] If the logic circuit 5 receives the signal L in step S2 (NO), it determines that a fault, such as a disconnection of the differential communication line, has occurred (S5). If the logic circuit 5 receives the signal H in step S4 (NO), it determines that a fault, such as a fault in the insulating unit 3, has occurred (S6). If a fault is determined in step S2 or S4, the logic circuit 5 transmits the determination result to a higher-level control device, as will be described in a second embodiment later.

[0025] The determinations in steps S2 and S4 will now be described with reference to FIGS. 7 to 9. Note that "BIST" in the figures stands for Built-In Self-Test. As shown in FIG. 7(a), if signal H is transmitted as a differential signal during normal communication, the receiver 4 demodulates signal H, which is the expected value in step S2. Also, as shown in FIG. 7(b), if signal H is transmitted as an in-phase signal, the receiver 4 demodulates signal L, which is the expected value in step S4.

[0026] 8(c), if, for example, capacitor 24m has an open fault, when signal H is transmitted as a differential signal, the signal on the m side of the differential communication line is not transmitted to receiver 4, and only the signal on the p side is transmitted. Therefore, if the signal input to comparator 26 is sufficiently amplified, signal H is demodulated by receiver 4, and a fault in capacitor 24m cannot be detected. In the case of a short fault shown in FIG. 8(d), when signal H is transmitted as a differential signal, the amplitude of the signal on the m side becomes larger than normal, destroying the differential characteristic, but signal H is still demodulated by receiver 4, and the fault cannot be detected.

[0027] Therefore, in this embodiment, a period for detecting a fault is set after startup of the communication device 1, and a diagnostic in-phase signal is transmitted from the transmitter 2. As a result, if the differential communication line is healthy, as shown in (b) of Fig. 7, the receiver 4 demodulates a signal L, whereas, as shown in (e) and (f) of Fig. 9, if, for example, the capacitor 23m has an open fault or a short fault, the receiver 4 demodulates a signal H. This makes it possible to detect a fault in the insulating unit 3 through self-diagnosis.

[0028] As described above, according to this embodiment, the communication device 1 includes the transmitter 2, the isolator 3, the receiver 4, and the logic circuit 5. The transmitter 2 transmits a differential signal through the isolator 3. When the signal generators 11 and 12 on-off modulate the input signal based on the clock signal, if the input self-diagnosis switching signal is inactive, the signal generators 11 and 12 convert the modulated signal into a differential out-of-phase modulated signal. On the other hand, if the self-diagnosis switching signal is active, the modulated signal is output to the differential signal line as a diagnostic differential in-phase modulated signal. With this configuration, when the receiver 4 receives and demodulates the diagnostic differential in-phase modulated signal, the demodulation result differs depending on whether the isolator 3 is normal or abnormal. This makes it possible to determine through self-diagnosis whether the isolator is faulty.

[0029] Second Embodiment Hereinafter, the same components as those in the first embodiment will be denoted by the same reference numerals, and a description thereof will be omitted. Only differences will be described. As shown in Fig. 10, a communication device 31 in the second embodiment includes a transmitter 2(1), an insulating unit 3(1), and a receiver 4(1) for transmitting a signal from a control circuit 32(1) to a control circuit 32(2), and a transmitter 2(2), an insulating unit 3(2), and a receiver 4(2) for transmitting a signal from the control circuit 32(2) to the control circuit 32(1). The control circuit 32 has the function of the logic circuit 5 in the first embodiment, and the control circuit 32(1) outputs a self-diagnosis switching signal to the transmitter 2(1), and the control circuit 32(2) outputs a self-diagnosis switching signal to the transmitter 2(2).

[0030] Next, the operation of the second embodiment will be described. In Figure 11, steps S11 to S16 correspond to steps S1 to S6 in the first embodiment. When the communication device 31 is started, the transmitter (1) first executes the same process as in the first embodiment. The fault determination in steps S15 and S16 is performed by the control circuit 32(2). The occurrence of a fault is transmitted from the control circuit 32(2) via the transmitter 2(2), the insulating unit 3(2), and the receiver 4(2) to the control circuit 32(1), which then transmits the signal to the MCU (Micro Control Unit) 33, a higher-level control device.

[0031] Steps S11 to S16 are similar to steps S11 to S16 and are performed by the control circuit 32(2), transmitter 2(2), insulating unit 3(2), and receiver 4(2). The fault determinations in steps S21 and S22 are performed by the control circuit 32(1).

[0032] In addition to the inventions described in the claims, this application also includes the following inventions. [1] A transmitter that transmits an electrical signal through an insulating unit (3), and that includes a modulated signal generator (11, 12) that, when digitally modulating an input signal based on a clock signal, converts the modulated signal into a differential out-of-phase modulated signal if the input self-diagnosis switching signal is inactive, and outputs the modulated signal to a differential signal line as a differential in-phase modulated signal for diagnosis if the self-diagnosis switching signal is active. [2] A transmitter as described in [1], in which the modulated signal generator performs on-off modulation. [3] A communication device that includes: a transmitter (2) as described in [1] or [2]; a receiver (4) that receives and demodulates the modulated signal transmitted from the transmitter; an insulating unit (3) connected between the transmitter and the receiver; and a receiver-side control unit (5, 32) that, during self-diagnosis when the self-diagnosis switching signal is active, determines whether the signal is normal or abnormal based on the signal demodulated by the receiver, and transmits the diagnosis result to a higher-level control device. [4] The communication device according to [3], wherein the demodulated signal exhibits a low logic value if normal and a high logic value if abnormal during self-diagnosis when the self-diagnosis switching signal is active. [5] The communication device according to [3] or [4], wherein the receiver includes a differential amplifier (21) and an envelope detector (22), and demodulates the modulated signal. [6] The communication device according to any one of [3] to [5], wherein the insulating unit is configured by connecting two or more capacitance elements (23, 24) in series.

[0033] (Other Embodiments) The digital modulation is not limited to on-off modulation, but may be other methods such as frequency modulation. Therefore, the demodulation method in the receiver is not limited to using an envelope detector. The insulating section is not limited to two capacitors connected in series, but may be configured with one or three or more insulating elements. It may also be configured with an inductively coupled element.

[0034] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A transmitter that transmits an electrical signal through an insulating unit (3), and that includes a modulated signal generating unit (11, 12) that, when digitally modulating an input signal based on a clock signal, converts the modulated signal into a differential out-of-phase modulated signal if the input self-diagnosis switching signal is inactive, and outputs the modulated signal to a differential signal line as a differential in-phase modulated signal for diagnosis if the self-diagnosis switching signal is active.

2. The transmitter according to claim 1, wherein said modulated signal generating section performs on-off modulation.

3. A communication device comprising: a transmitter (2) according to claim 1 or 2; a receiver (4) that receives and demodulates the modulated signal transmitted from the transmitter; an insulating section (3) connected between the transmitter and the receiver; and a receiving-side control section (5, 32) that, during self-diagnosis when the self-diagnosis switching signal becomes active, determines whether the signal is normal or abnormal based on the demodulated signal by the receiver and transmits the diagnosis result to a higher-level control device.

4. A communication device according to claim 3, wherein the demodulated signal exhibits a low logic value if normal during self-diagnosis when the self-diagnosis switching signal is active, and a high logic value if abnormal.

5. A communication device according to claim 3, wherein the receiver comprises a differential amplifier (21) and an envelope detector (22) for demodulating the modulated signal.

6. A communication device according to claim 3, wherein the insulating section is configured by connecting two or more electrostatic capacitance elements (23, 24) in series.

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