CN114866160B - Isolation protection circuit, module and chip of RS485 chip in acquisition terminal - Google Patents
Isolation protection circuit, module and chip of RS485 chip in acquisition terminal Download PDFInfo
- Publication number
- CN114866160B CN114866160B CN202210591771.7A CN202210591771A CN114866160B CN 114866160 B CN114866160 B CN 114866160B CN 202210591771 A CN202210591771 A CN 202210591771A CN 114866160 B CN114866160 B CN 114866160B
- Authority
- CN
- China
- Prior art keywords
- chip
- isolation
- differential
- filter circuit
- protection
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
- 238000002955 isolation Methods 0.000 title claims abstract description 137
- 239000003990 capacitor Substances 0.000 claims abstract description 46
- 230000000670 limiting effect Effects 0.000 claims abstract description 14
- 230000001052 transient effect Effects 0.000 claims abstract description 14
- 230000001629 suppression Effects 0.000 claims abstract description 12
- 102100028680 Protein patched homolog 1 Human genes 0.000 claims description 15
- 101710161390 Protein patched homolog 1 Proteins 0.000 claims description 15
- 238000007599 discharging Methods 0.000 claims description 6
- 230000002401 inhibitory effect Effects 0.000 claims description 5
- 238000004806 packaging method and process Methods 0.000 claims description 4
- 230000005540 biological transmission Effects 0.000 claims description 3
- 238000004891 communication Methods 0.000 abstract description 11
- 238000001914 filtration Methods 0.000 description 23
- 230000006872 improvement Effects 0.000 description 7
- 238000010586 diagram Methods 0.000 description 6
- 230000003068 static effect Effects 0.000 description 6
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 4
- 230000005611 electricity Effects 0.000 description 3
- 238000000034 method Methods 0.000 description 3
- 101100163833 Arabidopsis thaliana ARP6 gene Proteins 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000036632 reaction speed Effects 0.000 description 2
- 235000012239 silicon dioxide Nutrition 0.000 description 2
- 239000000377 silicon dioxide Substances 0.000 description 2
- 102100036894 Protein patched homolog 2 Human genes 0.000 description 1
- 101710161395 Protein patched homolog 2 Proteins 0.000 description 1
- 229910004298 SiO 2 Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 230000001808 coupling effect Effects 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 230000002452 interceptive effect Effects 0.000 description 1
- 238000012423 maintenance Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B15/00—Suppression or limitation of noise or interference
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/04—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess voltage
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04Q—SELECTING
- H04Q9/00—Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom
Abstract
The invention belongs to the technical field of digital-analog hybrid and radio frequency integrated circuits, and particularly relates to an isolation protection circuit, a module and a chip of an RS485 chip in an acquisition terminal. The isolation protection circuit comprises an isolation filter circuit, a serial port end protection device and a differential end protection device. The isolation filter circuit comprises an isolation device and a filter device; the isolation device is electrically connected with the RS485 chip. The filter device includes a first filter circuit, a second filter circuit, and a third filter circuit. The serial port end protection device is connected to serial port end interfaces of the RS485 chip and the isolation device. The serial port end protection device is used for releasing interference signals on the RS485 serial port pins. The differential end protection device is connected to the differential end A, B of the RS485 chip. The differential end protection device is composed of 4 current limiting resistors, 3 transient suppression diodes, 2 ESD diodes, a pull-up resistor, a pull-down resistor, a thermistor and a capacitor. The invention solves the problems of insufficient communication stability and poor anti-interference performance of the RS485 interface.
Description
Technical Field
The invention belongs to the technical field of digital-analog hybrid and radio frequency integrated circuits, and particularly relates to an isolation protection circuit, a module and a chip of an RS485 chip in an acquisition terminal, and the RS485 chip integrated with the isolation protection chip.
Background
The power acquisition terminal equipment used on the power grid generally adopts a product modularized design, and the modularized power acquisition equipment consists of a series of standard components with independent functions and independent input and output. The modular terminal design divides the power acquisition terminal into various different components such as a power supply unit, a processing unit, a communication unit, a functional unit and the like, and the components are physically isolated from each other. In order to improve isolation protection performance, the acquisition terminal main control module MCU also uses a power supply independent of other circuits. In order to prevent interference among other power supply circuits, the main control module is required to be isolated from other circuits or interfaces in part of equipment.
The prior acquisition terminal is generally internally provided with no protection device, and circuit communication is easy to be interfered. The scheme of the isolation circuit is adopted by part of the acquisition terminal circuit, but the shielding requirement of the RS485 diversified interference signals cannot be met by the isolation circuit with a single function, and the impact of accumulated interference signals on the chip cannot be resisted. In addition, by adding a protection module or adding a structure for shielding interference, the method is high in application cost, difficult in maintenance of a system using an RS485 communication interface and not suitable for large-scale popularization and application.
Disclosure of Invention
In order to solve the problems that equipment for communication by adopting the existing RS485 interface is easy to be interfered, the communication stability is insufficient and the anti-interference performance is poor; the invention relates to an isolation protection circuit, a module and a chip of an RS485 chip in an acquisition terminal, and the RS485 chip integrated with the isolation protection chip.
The invention is realized by adopting the following technical scheme:
the isolation protection circuit of the RS485 chip in the acquisition terminal comprises an isolation filter circuit, a serial port end protection device and a differential end protection device.
The isolation filter circuit comprises an isolation device and a filter device; the three-channel interface of the isolation device comprises an enabling end, a sending end and a receiving end. The three channel interfaces of the isolation device are respectively and electrically connected with three corresponding interfaces of the serial port end in the RS485 chip. The filter device includes a first filter circuit, a second filter circuit, and a third filter circuit. The first filter circuit is connected to the power end of the isolation device and used for inhibiting the influence of the surge voltage on RS 485. The second filter circuit is connected to the ground end of the isolation device and is used for discharging interference signals accumulated on the RS485 chip through the ground end. The third filter circuit is connected to all interfaces except the power end and the ground end of the isolation device and is used for removing high-frequency interference signals.
The serial port end protection device is connected to three interfaces in the serial port end where the RS485 chip and the isolation device are connected with each other. The serial port end protection device is used for releasing interference signals on the RS485 serial port pins.
The differential end protection device is connected to the differential end A, B of the RS485 chip. The differential end protection device is composed of 4 current limiting resistors R4, R6, R91 and R92,3 transient suppression diodes TVS1, TVS2, TVS3,2 ESD diodes D11 and D17, a pull-up resistor R23, a pull-down resistor R24, a thermistor PTC1 and a capacitor C7. In the differential end protection device, one end of R4 is connected with one differential interface B of the RS485 chip, and the other end of R4 is sequentially connected with R91 and PTC1 in series. The other end of the PTC1 is used as an external port of the differential interface B. One end of R6 is connected with another differential interface A of the RS485 chip, the other end of R6 is connected with R92 in series, and the other end of R92 is used as an external port of the differential interface A. One end of D11 is connected between R4 and R91, and the other end is virtually grounded. One end of D17 is connected between R5 and R92, and the other end is virtually grounded. The 3 transient suppression diodes TVS1, TVS2, and TVS3 are connected in series with each other, and are connected to virtual ground at both ends. The intermediate nodes of TVS1 and TVS2 are electrically connected to the intermediate nodes of R92 and PTC1. The intermediate nodes of TVS2 and TVS3 are electrically connected with the node of R92 as the external terminal of differential interface A. One end of the pull-up resistor R23 is connected with the differential interface B of the RS485 chip, and the other end of the pull-up resistor R23 is virtually grounded. One end of the pull-down resistor R24 is connected with the differential interface A of the RS485 chip, and the other end is connected with a power supply. One end of the capacitor C7 is connected to the power end of the RS485 chip, and the other end of the capacitor C is virtually grounded.
As a further improvement of the invention, the serial port end protection device comprises 3 ESD diodes and 1 resistor R93, wherein two ESD diodes are respectively connected in series to the transmitting end and the receiving end of the RS485 chip, and a third ESD diode is connected in parallel with the resistor R93 and then connected in series to the enabling end of the RSA485 chip; the other ends of the three ESD diodes are all grounded virtually.
As a further improvement of the invention, the isolation device adopts a transmission device with two paths and six channels; the isolation device supports simultaneous connection with two RS485 chips.
As a further improvement of the invention, the second filter circuit adopts a safety capacitor C99, one end of the safety capacitor C99 is connected with the ground end of one path of the isolation device and is grounded in real, and the other end of the safety capacitor C99 is connected with the ground end of the other path of the isolation device and is grounded in virtual mode.
As a further improvement of the invention, the safety capacitor C99 adopts a Y capacitor with the specification of 1000 PF/4000V.
As a further improvement of the invention, the first filter circuit comprises two groups, and both groups are formed by serially connecting a current limiting resistor and a capacitor. The two power ends of the isolation device are respectively connected to the nodes connected between the current limiting resistor and the capacitor in the two groups of first filter circuits. In the two groups of first filter circuits, the other ends of the capacitors are grounded, and the other ends of the current limiting resistors are connected with a power supply.
As a further improvement of the invention, the third filter circuit is formed by a resistor and a capacitor connected in series. In the third filter circuit, the other end of the resistor is electrically connected with the isolation device, and the other end of the capacitor is used as an external port of the isolation device.
As a further improvement of the invention, the isolation device adopts a Na8262 six-channel digital isolator. The model of the transient suppression diode in the differential end protection device is SMAJ60CA; the nominal resistance of the thermistor PTC1 is between 30-60 omega.
The invention further comprises an isolation protection module of the RS485 chip in the acquisition terminal, wherein the isolation protection module adopts the circuit layout of the isolation protection circuit and is used for carrying out isolation protection on the RS485 chip. The isolation protection module comprises an isolation filter unit, a serial port end protection unit and a differential end protection unit.
The isolation filtering unit is composed of an isolation circuit, a first filtering subunit, a second filtering subunit and a third filtering subunit. The isolation circuit adopts a digital isolator with two paths and six channels. The first filtering subunit comprises two groups which are respectively connected to two power supply ends of the isolation device, and the first filtering subunit is used for inhibiting the influence of impulse voltage on RS 485. The second filtering subunit is connected between two ground ends of the isolation device and is used for discharging interference signals accumulated on the RS485 chip through the ground ends. The third filtering subunit adopts a plurality of independent RC filtering circuits and is connected to all interfaces of the isolation device except the power end and the ground end. The third filtering subunit is used for removing the high-frequency interference signal.
The serial port end protection unit is connected to three interfaces in the serial port end where the RS485 chip and the isolation circuit are connected with each other. The serial port end protection device is used for releasing interference signals on the RS485 serial port pins.
The differential end protection unit is connected to the differential end A, B of the RS485 chip and is used for protecting the RS485 chip from the impact of instantaneous high-voltage spike pulse.
The invention also comprises an isolation protection chip, which is formed by packaging the isolation protection circuit of the RS485 chip in the acquisition terminal. The pins of the isolation protection chip comprise: a power terminal pin, a ground terminal pin, a virtual ground pin, two differential interface pins, and three serial port pins.
The power supply terminal pin is connected to the VCC pin of the RS485 chip and is used for connecting a power supply.
One ground pin is used for grounding.
The virtual ground pin is connected to the GND pin of the RS485 chip and is used for grounding the virtual ground.
The two differential interface pins are respectively and electrically connected with differential interfaces A and B in the RS485 chip.
The three serial ports pins include a transmitting terminal pin, a receiving terminal pin and an enabling terminal pin. The enabling end pin is used for being electrically connected with RE and DE pins of the RS485 chip; the sending end pin is used for being electrically connected with a DI pin of the RS485 chip; and the receiving end pin is used for being electrically connected with an RO pin of the RS485 chip.
The invention also comprises an RS485 chip, wherein the RS485 chip is integrated with the isolation protection chip, has the isolation protection function, and improves the communication stability and the anti-interference capability.
The technical scheme provided by the invention has the following beneficial effects:
1. according to the isolation protection circuit, an ESD protection diode is added to a A, B differential interface of the RS485 chip, a serial port transmitting end, a serial port receiving end and a serial port enabling end, so that the RS485 chip is protected from interference of external pulse group coupling interference, static discharge interference, static and other high-frequency signals. When the RS485 interface is connected to a strong electric wire in a wrong way, the ESD2 part is used as a first-stage protection, and the PTC2 is used as a thermistor, so that the whole RS485 can be protected from being burnt out by the strong electric wire. Through setting up the TVS tube, can the speed of PS level limit too high voltage in a safe range to play the effect of protection later circuit, three transient suppression diodes TVS1, TVS2 and TVS3 put in this position, can protect the circuit from surging overvoltage signal dashes. By providing two ESD diodes D11 and D17 in parallel in the circuit, the circuit can be protected from high frequency signals. The TVS absorbs energy greatly, reflects slowly, is suitable for surge protection, has small absorption capacity of the ESD diode, but has high reaction speed, and is suitable for electrostatic occasions, so that the first-stage protection of the ESD2 part adopts the ESD diode and the TVS tube simultaneously, and the external pulse group coupling interference and the electrostatic discharge interference can be shielded. In addition, the ESD1 part is used as a second-stage protection, and three ESD tubes D13, D16 and D18 are used to protect the RS485 chip from high-frequency signals such as static electricity.
2. The isolation protection circuit of the invention is provided with the RC filter circuit at the input end and the output end of the capacitive isolation device respectively, thereby protecting communication from interference. The chip is prevented from being damaged due to impact current.
3. In the method provided by the invention, proper safety capacitors are added at the two ends of the optical coupler of the capacitive isolation device, and the accumulated charges of the circuit interference signals are rapidly released by utilizing the safety capacitors, so that the stability of the transmitted signals is improved, and the anti-interference capability of the chip is improved.
4. The scheme provided by the invention can provide an omnibearing signal anti-interference effect for the RS485 chip, greatly improve the isolation protection performance of the chip, and can be integrated into the existing chip or the existing equipment, thereby reducing the equipment installation cost and improving the maintainability of the product.
Drawings
Fig. 1 is a detailed circuit diagram of an isolation protection circuit of an RS485 chip in an acquisition terminal according to embodiment 1 of the present invention.
Fig. 2 is a schematic diagram of the isolation device of embodiment 1 of the present invention in which high voltage isolation is achieved by series capacitors.
Fig. 3 is a functional module connection schematic diagram of an isolation protection module of an RS485 chip in an acquisition terminal according to embodiment 2 of the present invention.
Fig. 4 is a schematic structural diagram of an isolation protection chip and pins thereof of an RS485 chip in an acquisition terminal according to embodiment 3 of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Example 1
The embodiment provides an isolation protection circuit of an RS485 chip in an acquisition terminal, which comprises an isolation filter circuit, a serial port end protection device and a differential end protection device.
Wherein, as shown in fig. 1, the isolation filter circuit comprises an isolation device and a filter device. Specifically, the isolation device in this embodiment is a U8 chip in the circuit diagram. The isolation circuit adopts a transmission device with two paths and six channels; the circuit model is Na8262; the isolation device is supported to be connected with two RS485 chips at the same time, and the RS485 chip corresponds to a U2 chip in a circuit diagram, and the model is MAX3082ESA. The three channel interface of the isolation device includes an enable terminal RN, a transmit terminal TX and a receive terminal RX. The three channel interfaces of the isolation device are respectively and electrically connected with three corresponding interfaces of the serial port end in the RS485 chip.
Isolation is a method of preventing direct current interference between two parts of a system or preventing interfering alternating current while allowing signals to be transmitted normally in the two parts of the system. Such isolation may be required to protect operators from damage by expensive processors in the high voltage system, and to disconnect the ground loop in the communication network from communication with high-end equipment. Digital isolators are the best choice, such as SPI, UART, I2C, RS-485 and CAN, in many different system applications, including industrial automation systems, motor drives, medical devices, solar inverters, power supplies and hybrid electric vehicles.
Referring to fig. 2, the isolation device may use silicon dioxide (SiO 2 ) As dielectrics used in signal isolation and digital isolators. Typically two series connected silicon dioxide capacitors, one on each side of the isolation gate, are used to achieve high voltage isolation. Compared with an inductance-based (magnetic isolation) isolator and a traditional optocoupler, siO 2 The dielectric strength provided is highest, does not degrade from exposure to ambient humidity, and can have an isolation lifetime of greater than 100 years.
The filter device in this embodiment includes a first filter circuit, a second filter circuit, and a third filter circuit. The first filter circuit is connected to the power supply terminal of the isolation device and corresponds to a part of the circuit in the RC1 area in FIG. 1. The first filter circuit is used for inhibiting the influence of the surge voltage on RS 485. It is contemplated that the isolation device has two outputs and can support the connection of two RS485 chips. In this embodiment, the first filter circuits are also arranged in two groups. The two groups of first filtering currents are formed by connecting a current limiting resistor and a capacitor in series. The two power ends of the isolation device are respectively connected to the nodes connected between the current limiting resistor and the capacitor in the two groups of first filter circuits. In the two groups of first filter circuits, the other ends of the capacitors are grounded, and the other ends of the current limiting resistors are connected with a power supply.
The second filter circuit in this embodiment is connected to the ground of the isolation device. The second filtering current is used for discharging interference signals accumulated on the RS485 chip through the ground terminal. As shown in the RC2 area of fig. 1, the second filter circuit adopts a safety capacitor C99, wherein one end of the safety capacitor C99 is connected to the ground terminal of one path of the isolation device and is grounded in real, and the other end of the safety capacitor C99 is connected to the ground terminal of the other path of the isolation device and is grounded in virtual. In this embodiment, the safety capacitor C99 is a Y capacitor with a specification of 1000 PF/4000V.
In this embodiment, both the first filter circuit and the second filter circuit may function as an RC low-pass filter. The capacitor element has characteristics of high-pass frequency and low-pass frequency. The RC filter utilizes the characteristic of the capacitive element to introduce the high-frequency signal to the ground, and only the low-frequency signal is left in the circuit, so that the purpose of removing the high-frequency signal in the circuit is realized.
The third filter circuit is connected to all interfaces except the power end and the ground end of the isolation device and is used for discharging charges accumulated at the ground end of the RS485 circuit. As shown in the RC3 region of fig. 1, the third filter circuit is formed by connecting a resistor and a capacitor in series. In the third filter circuit, the other end of the resistor is electrically connected with the isolation device, and the other end of the capacitor is used as an external port of the isolation device.
In this embodiment, the third filter circuit uses the coupling effect of the Y capacitor to connect the two circuits, and allows the ac signal to pass through and transmit to the next stage circuit, so as to release the interference energy above the virtual ground to the real ground, and the interference signal energy is transmitted, thereby protecting the circuit components of the RS485 part.
The serial port end protection device is connected to three interfaces in the serial port end where the RS485 chip and the isolation device are connected with each other. The serial port end protection device is used for releasing interference signals on the RS485 serial port pins. Specifically, as shown in an ESD1 part in fig. 1, the serial port end protection device includes 3 ESD diodes and 1 resistor R93, where two ESD diodes are respectively connected in series to a transmitting end and a receiving end of the RS485 chip, and a third ESD diode is connected in parallel with the resistor R93 and then connected in series to an enabling end of the RSA485 chip; the other ends of the three ESD diodes are all grounded virtually.
In this embodiment, the ESD diode has a small absorption capacity, but has a high reaction speed, and is suitable for occasions such as static electricity. By adopting the three ESD diodes D13, D16, and D18, the RS485 chip can be protected from high frequency signals such as static electricity.
The differential end protection device is connected to the differential end A, B of the RS485 chip. The differential end protection device is composed of 4 current limiting resistors R4, R6, R91 and R92,3 transient suppression diodes TVS1, TVS2, TVS3,2 ESD diodes D11 and D17, a pull-up resistor R23, a pull-down resistor R24, a thermistor PTC1 and a capacitor C7. The model of the transient suppression diode in the differential end protection device is 5MAJ60CA; the nominal resistance of the thermistor PTC1 may be between 30-60 Ω and will not be described in detail herein.
As shown in ESD2 part in fig. 1, in the differential end protection device, one end of R4 is connected to one of differential interfaces B of the RS485 chip, and the other end of R4 is serially connected with R91 and PTC1 in sequence. The other end of the PTC1 is used as an external port of the differential interface B. One end of R6 is connected with another differential interface A of the RS485 chip, the other end of R6 is connected with R92 in series, and the other end of R92 is used as an external port of the differential interface A. One end of D11 is connected between R4 and R91, and the other end is virtually grounded. One end of D17 is connected between R5 and R92, and the other end is virtually grounded. The 3 transient suppression diodes TVS1, TVS2, and TVS3 are connected in series with each other, and are connected to virtual ground at both ends. The intermediate nodes of TVS1 and TVS2 are electrically connected to the intermediate nodes of R92 and PTC1. The intermediate nodes of TVS2 and TVS3 are electrically connected with the node of R92 as the external terminal of differential interface A. One end of the pull-up resistor R23 is connected with the differential interface B of the RS485 chip, and the other end of the pull-up resistor R23 is virtually grounded. One end of the pull-down resistor R24 is connected with the differential interface A of the RS485 chip, and the other end is connected with a power supply. One end of the capacitor C7 is connected to the power end of the RS485 chip, and the other end of the capacitor C is virtually grounded.
In this embodiment, when the two ends of the TVS are subjected to the transient high energy impact, it changes the impedance value between the two ends from high impedance to low impedance at the speed of PS seconds to absorb an instantaneous large current, clamps the voltage between the two ends of the TVS to a predetermined value, thereby protecting the following precision components from the impact of the transient high voltage spike pulse, and places the three transient suppression diodes TVS1, TVS2 and TVS3 at this position to mainly protect the circuit from the surge overvoltage signal; d11 and D17 are ESD diodes connected in parallel in the circuit to protect the circuit from high frequency signals. TVS absorbs energy greatly, reflects slowly, is suitable for surge protection, and ESD diode reaction rate is fast, is suitable for electrostatic occasion.
Example 2
On the basis of the circuit designed in embodiment 1, the embodiment further comprises an isolation protection module of the RS485 chip in the acquisition terminal, and the isolation protection module adopts the circuit layout of the isolation protection circuit as in embodiment 1 and is used for performing isolation protection on the RS485 chip.
The isolation protection module in the embodiment comprises three different circuit units, namely an isolation filtering unit, a serial port end protection unit and a differential end protection unit. In fact, the isolation protection module may employ the circuit of embodiment 1, or may employ other signal chips or circuits of different specifications having the same performance.
As shown in fig. 3, the isolation filtering unit is composed of an isolation circuit, a first filtering subunit, a second filtering subunit and a third filtering subunit. The isolation circuit adopts a digital isolator with two paths and six channels. The first filtering subunit comprises two groups which are respectively connected to two power supply ends of the isolation device, and the first filtering subunit is used for inhibiting the influence of impulse voltage on RS 485. The second filtering subunit is connected between two ground ends of the isolation device and is used for discharging interference signals accumulated on the RS485 chip through the ground ends. The third filtering subunit adopts a plurality of independent RC filtering circuits and is connected to all interfaces of the isolation device except the power end and the ground end. The third filtering subunit is used for removing the high-frequency interference signal.
The serial port end protection unit is connected to three interfaces in the serial port end where the RS485 chip and the isolation circuit are connected with each other. The serial port end protection device is used for releasing interference signals on the RS485 serial port pins.
The differential end protection unit is connected to the differential end A, B of the RS485 chip and is used for protecting the RS485 circuit from pulse group, static discharge interference and strong current burning out components.
Example 3
The embodiment also includes an isolation protection chip, which is formed by packaging the isolation protection circuit of the RS485 chip in the acquisition terminal as in embodiment 1. The packaging is in a chip mode, so that popularization and application of the isolation protection circuit are easier. And finally integrated into the equipment such as the acquisition device. And the maintainability of the equipment is improved.
As shown in fig. 4, the pins of the isolation protection chip include: a power terminal pin, a ground terminal pin, a virtual ground pin, two differential interface pins, and three serial port pins.
The power end pin is connected to the VCC pin of the RS485 chip and is used for connecting with a power supply.
One ground pin is used for grounding.
The virtual ground pin is connected to the GND pin of the RS485 chip and is used for grounding the virtual ground.
The two differential interface pins are respectively and electrically connected with differential interfaces A and B in the RS485 chip.
The three serial ports pins include a transmitting terminal pin, a receiving terminal pin and an enabling terminal pin. The enabling end pin is used for being electrically connected with RE and DE pins of the RS485 chip; the sending end pin is used for being electrically connected with a DI pin of the RS485 chip; and the receiving end pin is used for being electrically connected with an RO pin of the RS485 chip.
Example 4
On the basis of the foregoing embodiment, this embodiment further provides an RS485 chip, where the RS485 chip is integrated with an isolation protection chip as in embodiment 3, and has an isolation protection function, so as to improve communication stability and anti-interference capability.
The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.
Claims (9)
1. An isolation protection circuit of an RS485 chip in an acquisition terminal is characterized by comprising
An isolation filter circuit comprising an isolation device and a filter device; the three-channel interface of the isolation device comprises an enabling end, a sending end and a receiving end; the three channel interfaces of the isolation device are respectively and electrically connected with three corresponding interfaces of the serial port end in the RS485 chip; the filter device comprises a first filter circuit, a second filter circuit and a third filter circuit; the first filter circuit is connected to the power end of the isolation device and used for inhibiting the influence of impulse voltage on the RS485 chip; the second filter circuit is connected to the ground end of the isolation device and is used for discharging interference signals accumulated on the RS485 chip through the ground end; the third filter circuit is connected to all interfaces except the power end and the ground end of the isolation device and is used for removing high-frequency interference signals;
the serial port end protection device is connected to three interfaces in the serial port end where the RS485 chip and the isolation device are connected with each other; the serial port end protection device is used for releasing interference signals on serial port pins of the RS485 chip; and
a differential end protection device; the differential end A, B of the RS485 chip is connected with the differential end; the differential end protection device is composed of 4 current limiting resistors R4, R6, R91 and R92,3 transient suppression diodes TVS1, TVS2, TVS3,2 ESD diodes D11 and D17, a pull-up resistor R23, a pull-down resistor R24, a thermistor PTC1 and a capacitor C7; in the differential end protection device, one end of R4 is connected with one differential interface B of an RS485 chip, and the other end of R4 is sequentially connected with R91 and PTC1 in series; the other end of the PTC1 is used as an external port of the differential interface B; one end of R6 is connected with the other differential interface A of the RS485 chip, the other end of R6 is connected with R92 in series, and the other end of R92 is used as an external port of the differential interface A; one end of D11 is connected between R4 and R91, and the other end is virtually grounded; one end of D17 is connected between R5 and R92, and the other end is virtually grounded; the 3 transient suppression diodes TVS1, TVS2 and TVS3 are connected in series, and the two ends are virtually grounded; the intermediate nodes of TVS1 and TVS2 are electrically connected with the intermediate nodes of R92 and PTC1; the intermediate nodes of the TVS2 and the TVS3 are electrically connected with the node of the R92 serving as the external connection end of the differential interface A; one end of the pull-up resistor R23 is connected with the differential interface B of the RS485 chip, and the other end of the pull-up resistor R23 is virtually grounded; one end of the pull-down resistor R24 is connected with the differential interface A of the RS485 chip, and the other end is connected with a power supply; one end of the capacitor C7 is connected to the power end of the RS485 chip, and the other end of the capacitor C is virtually grounded.
2. The isolation protection circuit of an RS485 chip in an acquisition terminal according to claim 1, wherein: the serial port end protection device comprises 3 ESD diodes and 1 resistor R93, wherein two ESD diodes are respectively connected in series to the transmitting end and the receiving end of the RS485 chip, and a third ESD diode is connected in parallel with the resistor R93 and then connected in series to the enabling end of the RSA485 chip; the other ends of the three ESD diodes are all grounded virtually.
3. The isolation protection circuit of an RS485 chip in an acquisition terminal according to claim 1, wherein: the isolation device adopts a transmission device with two paths and six channels; the isolation device support is connected with two RS485 chips at the same time;
the second filter circuit adopts a safety capacitor C99, one end of the safety capacitor C99 is connected with the ground end of one path of the isolation device and grounded, and the other end of the safety capacitor C99 is connected with the ground end of the other path of the isolation device and grounded virtually.
4. The isolation protection circuit of the RS485 chip in the acquisition terminal according to claim 3, wherein: the safety capacitor C99 adopts a Y capacitor with the specification of 1000 PF/4000V.
5. The isolation protection circuit of the RS485 chip in the acquisition terminal according to claim 3, wherein: the first filter circuit comprises two groups, and the two groups are formed by connecting a current limiting resistor and a capacitor in series; two power ends of the isolation device are respectively connected to nodes connected between the current limiting resistor and the capacitor in the two groups of first filter circuits; in the two groups of first filter circuits, the other ends of the capacitors are grounded, and the other ends of the current limiting resistors are connected with a power supply.
6. The isolation protection circuit of the RS485 chip in the acquisition terminal according to claim 5, wherein: the third filter circuit is formed by connecting a resistor and a capacitor in series; in the third filter circuit, the other end of the resistor is electrically connected with the isolation device, and the other end of the capacitor is used as a port externally connected with the isolation device.
7. The isolation protection circuit of an RS485 chip in an acquisition terminal according to claim 1, wherein: the isolation device adopts a Na8262 six-channel digital isolator; the model of the transient suppression diode in the differential end protection device is 5MAJ60CA; the nominal resistance of the thermistor PTC1 is between 30-60 omega.
8. An isolation protection chip, which is characterized in that the isolation protection chip is formed by packaging an isolation protection circuit of an RS485 chip in an acquisition terminal according to any one of claims 1 to 7; the pins of the isolation protection chip comprise:
the power supply end pin is connected to the VCC pin of the RS485 chip and is used for connecting a power supply;
a ground pin for grounding to the ground;
the virtual ground pin is connected to the GND pin of the RS485 chip and is used for being grounded in a virtual mode;
the two differential interface pins are used for being electrically connected with differential interfaces A and B in the RS485 chip;
three serial ports pins, which include a transmitting terminal pin, a receiving terminal pin and an enabling terminal pin; the enabling end pins are used for being electrically connected with RE and DE pins of the RS485 chip; the sending end pin is used for being electrically connected with a DI pin of the RS485 chip; and the receiving end pin is used for being electrically connected with an RO pin of the RS485 chip.
9. An RS485 chip, characterized in that: the RS485 chip is integrated with the isolation protection chip according to claim 8.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210591771.7A CN114866160B (en) | 2022-05-27 | 2022-05-27 | Isolation protection circuit, module and chip of RS485 chip in acquisition terminal |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202210591771.7A CN114866160B (en) | 2022-05-27 | 2022-05-27 | Isolation protection circuit, module and chip of RS485 chip in acquisition terminal |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN114866160A CN114866160A (en) | 2022-08-05 |
| CN114866160B true CN114866160B (en) | 2024-02-06 |
Family
ID=82641049
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202210591771.7A Active CN114866160B (en) | 2022-05-27 | 2022-05-27 | Isolation protection circuit, module and chip of RS485 chip in acquisition terminal |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN114866160B (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN115513924B (en) * | 2022-09-16 | 2024-02-23 | 安徽南瑞中天电力电子有限公司 | Protection system for Ethernet communication of acquisition terminal |
Citations (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103236835A (en) * | 2013-04-09 | 2013-08-07 | 浙江威星智能仪表股份有限公司 | Signal isolation grid circuit |
| CN106655141A (en) * | 2017-02-24 | 2017-05-10 | 中船重工鹏力（南京）新能源科技有限公司 | 485 isolation high-voltage-resistant protective circuit |
| CN206181051U (en) * | 2016-11-19 | 2017-05-17 | 杭州步聚信息科技有限公司 | RS485 communication circuit |
| CN107749664A (en) * | 2017-11-15 | 2018-03-02 | 安徽南瑞中天电力电子有限公司 | A kind of design circuit of acquisition system emergency power supply |
| CN207319228U (en) * | 2017-11-02 | 2018-05-04 | 济南市长清计算机应用公司 | A kind of industrial USB turns RS485 signal adapters |
| CN109104181A (en) * | 2018-08-21 | 2018-12-28 | 深圳市雷赛控制技术有限公司 | A kind of RS485 circuit |
| CN208874545U (en) * | 2018-07-12 | 2019-05-17 | 宁波三星医疗电气股份有限公司 | A kind of remote signals Acquisition Circuit and application have the distribution terminal of the Acquisition Circuit |
| CN213817814U (en) * | 2020-12-26 | 2021-07-27 | 武汉吉阳光电科技有限公司 | Adapter for converting RS485 interface into CAN bus interface |
| CN113726626A (en) * | 2021-08-31 | 2021-11-30 | 天津津航计算技术研究所 | Filter protection circuit based on CAN bus driver chip |
| CN113904315A (en) * | 2021-10-20 | 2022-01-07 | 西安超越申泰信息科技有限公司 | Method for protecting serial port of data communication gateway machine of transformer substation |
| CN215813019U (en) * | 2021-08-31 | 2022-02-11 | 苏州佳智彩光电科技有限公司 | Novel high-voltage sampling protection circuit |
| WO2022041907A1 (en) * | 2020-08-27 | 2022-03-03 | 屹世半导体(上海)有限公司 | Digital isolator |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9197423B2 (en) * | 2008-02-14 | 2015-11-24 | Akros Silicon, Inc. | Electrostatic discharge protection circuit |
-
2022
- 2022-05-27 CN CN202210591771.7A patent/CN114866160B/en active Active
Patent Citations (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103236835A (en) * | 2013-04-09 | 2013-08-07 | 浙江威星智能仪表股份有限公司 | Signal isolation grid circuit |
| CN206181051U (en) * | 2016-11-19 | 2017-05-17 | 杭州步聚信息科技有限公司 | RS485 communication circuit |
| CN106655141A (en) * | 2017-02-24 | 2017-05-10 | 中船重工鹏力（南京）新能源科技有限公司 | 485 isolation high-voltage-resistant protective circuit |
| CN207319228U (en) * | 2017-11-02 | 2018-05-04 | 济南市长清计算机应用公司 | A kind of industrial USB turns RS485 signal adapters |
| CN107749664A (en) * | 2017-11-15 | 2018-03-02 | 安徽南瑞中天电力电子有限公司 | A kind of design circuit of acquisition system emergency power supply |
| CN208874545U (en) * | 2018-07-12 | 2019-05-17 | 宁波三星医疗电气股份有限公司 | A kind of remote signals Acquisition Circuit and application have the distribution terminal of the Acquisition Circuit |
| CN109104181A (en) * | 2018-08-21 | 2018-12-28 | 深圳市雷赛控制技术有限公司 | A kind of RS485 circuit |
| WO2022041907A1 (en) * | 2020-08-27 | 2022-03-03 | 屹世半导体(上海)有限公司 | Digital isolator |
| CN213817814U (en) * | 2020-12-26 | 2021-07-27 | 武汉吉阳光电科技有限公司 | Adapter for converting RS485 interface into CAN bus interface |
| CN113726626A (en) * | 2021-08-31 | 2021-11-30 | 天津津航计算技术研究所 | Filter protection circuit based on CAN bus driver chip |
| CN215813019U (en) * | 2021-08-31 | 2022-02-11 | 苏州佳智彩光电科技有限公司 | Novel high-voltage sampling protection circuit |
| CN113904315A (en) * | 2021-10-20 | 2022-01-07 | 西安超越申泰信息科技有限公司 | Method for protecting serial port of data communication gateway machine of transformer substation |
Also Published As
| Publication number | Publication date |
|---|---|
| CN114866160A (en) | 2022-08-05 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| EP1883179B1 (en) | Communication system for hazardous environments | |
| CN114866160B (en) | Isolation protection circuit, module and chip of RS485 chip in acquisition terminal | |
| CN112019039A (en) | Power interface circuit with high-grade surge protection and high EMI performance | |
| CN114915507B (en) | Gigabit POE power supply communication circuit | |
| CN210640904U (en) | CAN bus interface protection circuit, communication module and system | |
| CN101162840A (en) | Interface protective circuit | |
| CN106021166A (en) | RS485 bus-based multi-host communication circuit | |
| CN110855316B (en) | RS485 automatic receiving and transmitting isolation circuit | |
| CN207283569U (en) | Ethernet interface telecommunication circuit without network transformer | |
| CN107579832B (en) | Ethernet port communication circuit without network transformer | |
| CN213244036U (en) | Isolated communication circuit and device | |
| CN105324020A (en) | Electrical system having galvanic isolation | |
| CN214280931U (en) | Overvoltage surge protection circuit and device | |
| CN206224464U (en) | A kind of communicator with antijamming capability | |
| CN207283578U (en) | CAN node ports protect circuit | |
| CN114123148B (en) | Aviation three-wire system sensor port protection circuit | |
| CN112072628A (en) | Data interface protection circuit and data interface | |
| CN214278699U (en) | RS485 communication circuit and electrical apparatus | |
| CN207853914U (en) | PoE equipment without network transformer | |
| CN102386619B (en) | Circuit for inhibiting interference signal and carrying out surge protection | |
| CN216312673U (en) | Protective circuit | |
| CN213602646U (en) | RS232 communication device, RS485 communication device and lightning protection communication system with isolation | |
| CN219739960U (en) | Strong electromagnetic pulse protection device of integrated signal port | |
| CN218897210U (en) | Low-frequency filter circuit of photoelectric signal | |
| CN219204092U (en) | Electromagnetic compatibility protection circuit of sensor |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination | ||
| GR01 | Patent grant | ||
| GR01 | Patent grant |