Dual-mode fiber-optic photoelectric conversion device with isolation

Abstract

The utility model relates to industrial communication technical field, concretely discloses a kind of dual-mode fiber optic photoelectric conversion device with isolation, including the PCB board with laminated structure, and dual-mode fiber optic photoelectric conversion circuit integrated on the PCB board;The laminated structure of the PCB board includes successively from top to bottom, signal layer, independent ground layer, partition power supply layer, signal layer;The signal layer is used to arrange dual-mode fiber optic photoelectric conversion circuit;The independent ground layer is whole layer continuous ground copper, and all ground terminals in the signal layer are connected with the independent ground layer by metallization via hole;The partition power supply layer is provided with independent voltage area, and the power supply end of each module in the signal layer is connected with corresponding independent voltage area by metallization via hole.The utility model can promote suppression radiation interference, protect and strengthen surge tolerance, voltage compatibility extension, wiring and maintenance efficiency promotion.

Description

Technical Field

[0001] This utility model relates to the field of industrial communication technology, and more specifically to an isolated dual-mode fiber optic photoelectric conversion device. Background Technology

[0002] In scenarios such as industrial automation and power monitoring, there is an urgent need for RS485 and TTL signal transmission.

[0003] RS485 bus has become the mainstream industrial communication due to its strong anti-interference and low cost, but it is constrained by the bottleneck of copper cable transmission and is susceptible to ground loop interference and electromagnetic noise. To overcome these limitations, the industry has adopted fiber optic transmission. Early solutions consisted of "single-chip conversion + single optoelectronic device transmission + 2-layer board layout," which only supported RS485 signals and was incompatible with TTL levels. This resulted in a large number of TTL devices in the field needing to be equipped with additional TTL-to-fiber optic transmission equipment, increasing costs and complexity. Furthermore, the 2-layer board had weak anti-interference capabilities, and the single optoelectronic device had no redundancy, making it prone to communication interruptions due to faults.

[0004] TTL level is the mainstream logic level inside devices, but it has short transmission distance and poor anti-interference. Long-distance transmission requires indirect links or wireless solutions, which are not economical and reliable enough. Although dedicated TTL to fiber optic devices have emerged, most of them are single-channel transmission, which cannot meet the needs of parallel communication of multiple devices; the output voltage only supports a single specification of 3.3V or 5V, which is difficult to adapt to mixed voltage environments; and they also use the "single optoelectronic device + 2-layer board" architecture, which has weak anti-interference, low speed, and poor stability in a wide temperature range of -40℃ to +85℃.

[0005] Industrial applications demand communication that is "highly reliable, multi-compatible, and long-distance." However, existing technologies are insufficient in terms of functional expansion, anti-interference, and scenario adaptability. Users need to purchase 485 and TTL devices separately, incurring additional integration and maintenance costs. This has driven the development of a new generation of optoelectronic conversion technology that is "dual-mode compatible, multi-channel, and highly isolated" to address pain points related to protocol compatibility, signal isolation, and cost control. Utility Model Content

[0006] The purpose of this invention is to provide an isolated dual-mode fiber optic photoelectric conversion device for RS485 and TTL signal transmission, in order to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention adopts the following technical solution, including: A PCB board with a stacked structure, and a dual-mode fiber optic photoelectric conversion circuit integrated on the PCB board; The PCB board's stack-up structure includes a partitioned power layer, an independent ground layer, and a signal layer; The signal layer is used to arrange dual-mode fiber optic photoelectric conversion circuits; the independent grounding layer is a continuous copper layer, and all grounding terminals in the signal layer are connected to the independent grounding layer through metallized vias; the partitioned power supply layer has independent voltage regions, and the power supply terminals of each module in the signal layer are connected to the corresponding independent voltage region through metallized vias.

[0008] Preferably, the dual-mode fiber optic photoelectric conversion circuit includes a dual-mode switching module and a dual-voltage power supply module; The dual-mode switching module receives RS485 and TTL signals at one end, and is connected to the RS485 signal processing module and the isolated fiber optic transceiver module at the other end; the RS485 signal processing module is connected to the isolated fiber optic transceiver module.

[0009] The dual-voltage power supply module receives an external wide-voltage power supply at its input end and is electrically connected to an independent voltage region of the partitioned power supply layer at its output end, providing power to the dual-mode switching module, the RS485 signal processing module, and the isolated optical fiber transceiver module.

[0010] Preferably, the independent voltage regions of the partitioned power layer include a first independent voltage region, namely a 5.5V voltage region, a second independent voltage region, namely a 3.3V voltage region, and an independent conversion voltage region; the independent conversion voltage region holds the voltage after being switched by the power switching circuit.

[0011] This solution adopts a 4-layer board partition layout and power management settings with independent grounding layer and partitioned power layer. The partitioned power layer includes a 2mm isolation band. The top / bottom layers are signal layers, with the top layer placing the main components and wiring, and the bottom layer placing some components and wiring. The signal layers are partitioned and wired according to signal type (TTL / 485), which shortens the signal return path and reduces power ripple, thus solving the problem of weak anti-interference capability of 2-layer boards.

[0012] Preferably, the dual-mode switching module is a signal switch, specifically a 2-position DIP switch SW1, used to select the operating mode. When SW1-1 is closed, the 485 to fiber optic mode is selected; when SW1-2 is closed, the TTL to fiber optic mode is selected.

[0013] Preferably, the RS485 signal processing module includes a processing chip; the RS485 signal processing module is connected to the dual-mode switching module through a protection circuit; the protection circuit includes a MOSFET and a TVS diode; the two ends of the TVS diode are respectively connected to the A and B pins of the processing chip; the gate of the MOSFET is connected to one end of the TVS diode after being connected to resistors R10 and R11 in sequence, and the drain is connected to the other end of the TVS diode after being connected to resistor R8.

[0014] The 485 bus integrates a protection mechanism, connecting a 120Ω terminating resistor (impedance matching) in series at the A / B differential line terminals and a TVS diode (surge protection) in parallel, thus solving the problems of signal reflection and surge damage in existing technologies.

[0015] Preferably, the signal processing chip is model MAX13487E.

[0016] Preferably, the dual-voltage power supply module includes a first conversion circuit, a second conversion circuit, and a power switching circuit; the first conversion circuit is connected to a first independent voltage region of the partitioned power layer; the second conversion circuit is connected to a second independent voltage region of the partitioned power layer; and the power switching circuit is connected to an independent conversion voltage region of the partitioned power layer. The first independent voltage region is a 5V voltage region, and the second independent voltage region is a 3.3V voltage region. The independent conversion voltage region holds the voltage switched by the power switching circuit.

[0017] Preferably, the power switching circuit includes a logic circuit and a power switch; the logic circuit includes a NAND gate U3 and an inverter U2; the four pins of the NAND gate U3 are connected to the four pins of the inverter U2 through a series connection of a resistor R1, a MOSFET Q2, another MOSFET Q1, and a resistor R3. By combining the dual-mode switching module with the logic gate, selective access and fiber optic transmission switching between 485 and TTL signals can be achieved in the same module, enabling compatibility with both signal types without additional equipment and solving the redundancy problem of existing equipment.

[0018] Preferably, the conversion chip is model LM2596.

[0019] The wide voltage input and dual voltage output adapter circuit supports 5~48V input through a wide voltage power supply chip, i.e., a conversion chip. With the help of DIP switches to control the power layer output of 3.3V / 5V, it can adapt to industrial equipment with different voltages without the need for additional level conversion devices, thus improving compatibility.

[0020] Preferably, the first conversion circuit includes a conversion chip U1 and a step-down filter circuit 501; the second conversion circuit includes a voltage regulator chip U4 and a filter circuit.

[0021] Preferably, the isolated fiber optic transceiver module includes a fiber optic receiving circuit and a fiber optic transmitting circuit; the fiber optic transmitting circuit includes an isolator and a fiber optic transmitter connected in sequence; the fiber optic receiving circuit includes an isolator and a fiber optic receiver connected in sequence. The isolator is an optocoupler isolator, which bridges the 485 signal area and the TTL signal area to achieve electrical isolation between the input and output sides (isolation voltage ≥2500V), blocking ground potential difference and surge conduction paths, and improving anti-interference reliability in industrial environments.

[0022] Preferably, the isolator model is 6N137S.

[0023] Compared with the prior art, the embodiments of this utility model have at least the following advantages or beneficial effects: This solution enhances functional integration, significantly reducing system cost and space requirements. Integration is achieved through the following design: RS485 processing, TTL interface, and signal switches are integrated on a single 4-layer board, enabling mode multiplexing through signal switch switching, eliminating the need for additional hardware; a dual-voltage power supply module simultaneously powers the RS485 signal processing module, dual-mode switching module, and isolated fiber optic transceiver module, avoiding redundant power conversion circuit design. This solution reduces the number of devices from two to one, lowering procurement costs by 50%; and reduces installation space from two standard module slots to one, increasing space utilization by 100% in space-constrained scenarios such as industrial control cabinets.

[0024] This solution improves anti-interference capability and reliability, making it suitable for industrial environments with strong interference. It uses an isolator, i.e., an optocoupler isolator, to block conducted interference. Through the optocoupler, voltage isolation of 2500V can be achieved, realizing electrical isolation between the input and output sides. The circulating current path is cut off, reducing the risk of chip burnout.

[0025] The layer design of this solution can suppress radiated interference; the signal layer has two layers, namely the bottom plate and the top plate, and uses an independent bottom plate to shorten the signal return path to ≤5mm. Combined with the low impedance power supply of the partitioned power layer, the power ripple is reduced from 200mV to 50mV, and the signal edge distortion rate is reduced.

[0026] This solution enhances bus protection and surge tolerance. The TVS diode used can absorb 10kV transient voltages, and with impedance matching using a 120Ω terminating resistor R10, the signal reflection attenuation rate is reduced from 30% to 5%. Interference immunity: Common-mode rejection ratio increases from 40dB to 80dB; under 30V / m electromagnetic radiation, the communication bit error rate decreases from 1% to 0.01%. Reliability: Mean time between failures (MTBF) increases from 20,000 hours to 80,000 hours.

[0027] This solution expands voltage compatibility, reducing system adaptation costs. The power conversion chip supports 5~48V input, directly compatible with common industrial power supplies such as DC5V, DC12V, DC24V, and DC48V, eliminating adapter costs. Dual voltage output adapts to various types of equipment. Existing TTL to fiber optic devices have a fixed output voltage (3.3V or 5V), requiring additional level conversion chips in series for devices with different voltages. This patent switches the 3.3V / 5V output of the power layer via a power switch, directly matching backend devices and reducing the number of components. This solution expands the power adaptation range from one voltage to a full 5~48V range, adapting to over 90% of industrial scenarios; it saves on components, eliminating the need for level conversion chips and power adapters, further reducing the cost per module by 15%.

[0028] This solution improves cabling and maintenance efficiency while reducing project implementation costs. Its integrated design simplifies cabling; each module requires only one power supply, one signal channel (either RS-485 or TTL), and one fiber optic cable, reducing cabling workload by 50%. DIP switches simplify debugging: This patented solution uses signal and power switches to switch modes / voltages, reducing debugging time to ≤5 minutes. Using this solution in a 100-point monitoring system, cabling costs are reduced by 50%, and construction time is shortened by 40%. Maintenance efficiency is also improved; troubleshooting does not require disassembling multiple devices, and problems can be quickly located using indicator lights integrated into the top-level module, reducing maintenance time by 60%. Attached Figure Description

[0029] Figure 1 This is a structural diagram of the dual-mode fiber optic photoelectric conversion circuit of this utility model; Figure 2 This is a circuit diagram of the dual-mode switching module of this utility model; Figure 3 This is a circuit diagram of the RS485 signal processing module of this utility model; Figure 4 This is a voltage conversion circuit diagram of the present invention; Figure 5 This is the power switching circuit diagram of this utility model; Figure 6 This is a circuit diagram of the isolated optical fiber transceiver module of this utility model; Figure 7 This is a PCB stack-up structure diagram of the present invention; As shown in the figure: 1-Dual-mode switching module, 2-RS485 signal processing module, 201-Protection circuit, 3-Isolation fiber optic transceiver module, 4-Dual-voltage power supply module, 5-First conversion circuit, 501-Step-down filter circuit, 6-Second conversion circuit, 7-Power switching circuit, 701-Power switch, 702-Logic circuit, 8-Fiber optic transmitting circuit, 801-Fiber optic transmitter, 9-Fiber optic receiving circuit, 901-Fiber optic receiver, 10-Isolator, 11-Signal layer, 12-Independent grounding layer, 13-Zone power supply layer. Detailed Implementation

[0030] Existing technological shortcomings: First, the functions are limited, the equipment redundancy is high, and the cost is increased. The 485 signal conversion equipment and the TTL to fiber optic equipment are independent of each other: In the existing solution, the 485 signal conversion and fiber optic transmission equipment only supports the interaction between the 485 bus and the fiber optic cable, and cannot directly process TTL signals. If TTL signals need to be transmitted, a dedicated TTL to fiber optic equipment (single-channel design) must be purchased separately, which results in two independent equipment sets needing to be deployed in the system.

[0031] Second, waste of hardware resources: Both sets of equipment require independent power modules, fiber optic interfaces, PCB boards and housings. In industrial scenarios (such as monitoring systems that require both 485 and TTL transmission), the equipment procurement cost increases by more than 50%, and they occupy more installation space (such as inside the control cabinet).

[0032] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present utility model without creative effort are within the protection scope of the present utility model.

[0033] Reference Figure 1-7 As shown, this utility model provides a dual-mode fiber optic photoelectric conversion device with isolation: It includes a PCB board with a stacked structure, and a dual-mode fiber optic photoelectric conversion circuit integrated on the PCB board; according to Figure 7 As shown, the PCB board's layered structure, from top to bottom, includes a signal layer 11, an independent ground layer 12, a partitioned power layer 13, and another signal layer 11. The signal layer 11 is used to arrange dual-mode fiber optic photoelectric conversion circuits; the independent grounding layer 12 is a continuous grounding copper layer, and all grounding terminals in the signal layer 11 are connected to the independent grounding layer 12 through metallized vias; the partitioned power supply layer 13 has independent voltage regions, and the power supply terminals of each module in the signal layer 11 are connected to the corresponding independent voltage regions through metallized vias.

[0034] according to Figure 1 As shown, the dual-mode fiber optic photoelectric conversion circuit includes a dual-mode switching module 1 and a dual-voltage power supply module 4. The dual-mode switching module 4 receives RS485 signals and TTL signals at one end, and is connected to RS485 signal processing module 2 and isolated optical fiber transceiver module 3 at the other end; RS485 signal processing module 2 is connected to isolated optical fiber transceiver module 3.

[0035] The input terminal of the dual-voltage power supply module 4 receives an external wide-voltage power supply, and the output terminal is electrically connected to the independent voltage region of the partitioned power supply layer 13 to supply power to the dual-mode switching module 1, the RS485 signal processing module 2, and the isolated optical fiber transceiver module 3.

[0036] The stacked structure includes: a four-layer structure or a two-layer structure.

[0037] In a specific scenario, the four-layer structure includes, from top to bottom, signal layer 11, independent ground layer 12, partitioned power supply layer 13, and signal layer 14. The independent grounding layer is a complete grounding layer, with the shortest signal return path (≤5mm) to suppress common-mode interference; The bottom-layer 485 differential lines follow parallel, equal-length paths (10mil line width, 10mil spacing), and can provide 120Ω impedance matching for R10 via a DIP switch to reduce signal reflection. This patent uses optocoupler isolation to block ground potential differences and utilizes an independent ground / partitioned power layer 13 on a 4-layer board to improve anti-interference capabilities, increasing the common-mode rejection ratio from 40dB to 80dB and reducing the bit error rate from 1% to 0.01%. The partitioned power layer 13 is divided into three areas: a 5V voltage area, a 3.3V voltage area, and a switching power area. If a connection to a certain area is required, it can be directly connected via vias.

[0038] In a specific scenario, a two-layer structure includes: A "2-layer board + optimized ground plane" approach replaces the 4-layer board. The top layer retains the signal area, while the entire bottom layer is grounded (serving as a false ground plane). The power path is reinforced with a 2mm wide copper foil tightly adhering to the bottom ground plane. Principle and effect: By fully grounding the bottom layer, the return current path is shortened, achieving near-4-layer board interference immunity (common-mode rejection ratio 60dB), but with slightly higher power ripple (≤80mV), and a cost reduction of approximately 40%. Compatibility: The component layout and signal paths remain consistent with the original solution, only the stack-up structure is simplified. Reliability is still improved through optocoupler isolation and bus protection, making it suitable for cost-sensitive civilian applications.

[0039] according to Figure 2 As shown, the dual-mode switching module 1 is a signal switch. The signal switch is a relay K1.

[0040] In a specific scenario, the signal switch can be a DIP switch or a relay.

[0041] The relay can be a small signal relay (such as G6K-2P-Y-5VDC), which can switch between 485 and TTL modes through an external control signal (such as the MCU's I / O port). Principle and effect: The relay mechanically switches the signal path through contacts, resulting in a larger switching current (≥100mA), suitable for scenarios requiring remote control (such as switching via host computer software); however, it requires additional control circuitry, slightly increasing power consumption (approximately 5mA). The relay contacts can directly replace the mechanical contacts of a DIP switch, maintaining the same connection method, achieving functional integration, and solving equipment redundancy issues.

[0042] The 485 signal processing circuit and TTL signal interface are integrated on the same PCB board. The working mode (485 to fiber optic or TTL to fiber optic) can be selected by signal switch and power switch. It can be compatible with two signal types without additional equipment, reducing the number of devices and the total cost, and realizing an integrated design.

[0043] As shown in Figure 3, the RS485 signal processing module 2 includes a processing chip U7 and a protection circuit 201. The protection circuit includes a MOSFET Q3 and a TVS diode D3. The two ends of the TVS diode D3 are connected to the A and B pins of the processing chip, respectively. The gate of the MOSFET Q3 is connected to one end of the TVS diode D3 after being connected to resistors R10 and R11 in sequence, and the drain is connected to the other end of the TVS diode D3 after being connected to resistor R8. The TVS diode D3 absorbs surge voltages above ±6.5V. The 120Ω terminating resistor R10 matches the bus impedance and reduces signal reflection. Existing technologies only use a series current-limiting resistor. This patent improves the surge protection level by using a TVS diode and a terminating resistor, making it suitable for industrial environments with strong interference.

[0044] In a specific environment, other methods can also be used to replace TVS diodes, specifically: Surge protection is achieved by replacing TVS diodes with a combination of self-resetting fuses and varistors; Principle and effect: The self-resetting fuse can limit continuous overcurrent (such as during a short circuit), and the varistor absorbs surge voltage (the response speed is slightly slower than that of the TVS tube), which is suitable for scenarios with higher requirements for continuous overcurrent protection (such as outdoor wiring); compatibility: It can be directly connected in parallel between the 485 bus and ground, and the connection method with the terminating resistor remains unchanged, which can still improve the surge withstand capability.

[0045] Specifically, the model number of the signal processing chip U7 is MAX13487E.

[0046] according to Figure 4 As shown, the dual-voltage power supply module 4 includes a first conversion circuit 5, a second conversion circuit 6, and a power switching circuit 7; the first conversion circuit 5 is connected to the first independent voltage region of the partitioned power layer 13; the second conversion circuit 6 is connected to the second independent voltage region of the partitioned power layer 13; and the power switching circuit 7 is connected to the voltage switching region of the partitioned power layer 13.

[0047] according to Figure 5 As shown, specifically, the power switching circuit 7 includes a logic circuit 702 and a power switch 701; the logic circuit 702 includes a NAND gate U3 and an inverter U2; the 4 pins of the NAND gate U3 are connected to the 4 pins of the inverter U2 through a resistor R1, a MOSFET Q2, a MOSFET Q1, and a resistor R3 connected in series.

[0048] In a specific scenario, the signal switch works in conjunction with logic circuit 702 to achieve a "signal switch + logic gate" combination. Logic circuit 702 is used for reverse signal frequency matching, such as adjusting the polarity of the output of a fiber optic receiver and the input of a TTL device, ensuring signal logic consistency in both modes. This solution achieves mode switching through a "signal switch + logic gate" on the PCB, requiring no additional equipment and increasing integration by 50%. Furthermore, it enables linkage between the operating mode and power supply.

[0049] The 485 mode path is: receive RS485 signal - dual-mode switching module - RS485 signal processing module - isolated fiber optic transceiver module.

[0050] The TTL mode path consists of receiving TTL signals - dual-mode switching module - isolated fiber optic transceiver module.

[0051] In a specific scenario, the overall switching process is as follows: When the power switching switch 701, i.e. the DIP switch SW1, is open at pin 3-2, the control relay K1 is normally closed. At this time, the working mode is switched to 485 mode, and the logic circuit 702 will force the power supply to 5V, which is not controlled by pin 4-1. When the power switching switch 702, i.e., DIP switch SW1, is turned on at pin 3-2, the control relay K1 is normally open, and the working mode is switched to TTL mode. At the same time, the logic circuit 702 is turned on through pin 4-1, so that the dual voltage power supply module 4 outputs 5V voltage.

[0052] When the power switching switch 702, i.e., DIP switch SW1, is turned on at pin 3-2, the control relay K1 is normally open, and the working mode is switched to TTL mode. At the same time, it is turned off through pin 4-1, controlling the logic circuit 702 so that the dual voltage power supply module 4 outputs 3.3V voltage.

[0053] Specifically, the first conversion circuit 5 includes a conversion chip U1 and a step-down filter circuit 501; the second conversion circuit 6 includes a voltage regulator chip U4 and a filter circuit.

[0054] Specifically, the step-down filter circuit 501 includes an inductor L2, a TVS diode D1, a capacitor C1, and a capacitor C2 connected in parallel in sequence, and also includes a resistor R2 connected in series in the power input circuit, as well as a step-down conversion branch composed of a conversion chip U1, an energy storage inductor L1, a diode D2, and filter capacitors C3 and C4, to achieve a stable voltage conversion from 24V to 5V and provide reliable power supply for the internal circuit of the device; specifically, the filter circuit includes capacitors C5, C6, C7, and C8 connected in parallel in sequence.

[0055] In one specific scenario, the conversion chip U1 is model LM2596, and the voltage regulator chip U4 is model AMS1117.

[0056] The wide voltage input first conversion circuit 5 has a conversion chip U1 that receives 5~48V external power, converts it to 5V and inputs it into the first independent voltage region of the partitioned power layer 13, i.e., the 5V region; the second conversion circuit converts 5V to 3.3V and inputs it into the second independent voltage region of the partitioned power layer 13, i.e., the 3.3V region; the power switch SW1 in the power switching circuit 7 controls the power switching.

[0057] according to Figure 6 As shown, the isolated optical fiber transceiver module 3 includes an optical fiber receiving circuit 9 and an optical fiber transmitting circuit 8; the optical fiber transmitting circuit 8 includes an isolator 10 and an optical fiber transmitter 801 connected in sequence; the optical fiber receiving circuit 9 includes an isolator 10 and an optical fiber receiver 901 connected in sequence.

[0058] Specifically, the isolator 10 is a 6N137S optocoupler isolator.

[0059] Specifically, the fiber optic transmitter is model HFBR-1414TZ and the fiber optic receiver is model HFBR-2412TZ.

[0060] The optocoupler is connected between the 485 and TTL zones: the input side is connected to the RO output (485 signal) of the 485 chip or the TTL input signal, and is powered by the 5V zone; the output side is connected to the input of the fiber optic transmitter, and is powered by the 3.3V / 5V zone, and is electrically isolated through an independent ground plane (isolation voltage 2500V).

[0061] In a specific scenario, isolator 10 can also employ magnetic isolation. A magnetic isolation chip can replace the optocoupler to achieve electrical isolation for 485 / TTL signals.

[0062] Magnetic isolation couples signals via a high-frequency magnetic core, achieving an isolation voltage of up to 5000V (superior to optocouplers) and lower latency (≤10ns), making it suitable for higher frequency (>10Mbps) scenarios; however, the cost is slightly higher (approximately twice that of optocouplers). Compatibility: The input / output pin definitions of the magnetic isolation chip are compatible with optocouplers. Only the isolation boundary in the PCB routing needs to be adjusted (keeping the magnetic isolation chip bridging the 485 and TTL areas), without affecting dual-mode switching and 4-layer board layout, thus still solving the isolation deficiency problem of existing technologies.

[0063] Introducing an "isolation circuit": An optical coupler isolator is connected in series between the 485 / TTL signal input terminal and the fiber optic module to achieve electrical isolation between the input side and the output side (isolation voltage ≥2500V), blocking ground potential difference and surge conduction; In a specific scenario, the connection between the partitioned power layer 13 and the devices can be replaced by other methods besides via connections. Specifically, a "star connection" can be used instead of a "direct via connection." That is, the 5V and 3.3V voltage areas of the power layer are led out through a single point and then connected to the power supply pins of each device. Principle and effect: Reduces the number of vias on the power layer, reduces impedance abrupt changes, and is suitable for high-frequency signal (>5Mbps) scenarios. However, the wiring is slightly more complex, and it is necessary to ensure that the length of the branch lines is consistent. Compatibility: The power layer partitioning and isolation band design remains unchanged, and dual voltage output can still be achieved, solving the voltage compatibility problem.

[0064] In a specific scenario, differential line routing can also adopt "twisted pair routing" (outside the PCB) to replace the differential lines on the bottom layer of the PCB. That is, the differential lines inside the module are shorted to the terminal block, and the external PCB is connected to the 485 bus via twisted pair. Principle and effect: The twist pitch of the twisted pair can enhance the anti-interference capability (especially when the transmission distance is >10 meters), but more terminal blocks are required, and the module size increases slightly. Compatibility: The terminating resistor and TVS diode are still integrated inside the module, and the connection method with the 485 chip remains unchanged, so impedance matching and surge protection can still be achieved.

[0065] In summary, when RS485 and TTL signals enter the dual-mode switching module 1, two different operating modes are selected. In RS485 operating mode, the external 485 signal is input to the 485 chip of the RS485 signal processing module 2 via the A / B line, converted into a TTL signal, and then isolated by the optical coupler of the isolation optical fiber receiving module 3. The isolated signal drives the optical fiber transmitter 801 and is output through the optical fiber. The power supply is input from 5~48V, converted to 5V by the conversion chip of the dual power supply voltage module 4, and powered through the first independent voltage area of ​​the partitioned power layer 13, namely the 5V area.

[0066] TTL operating mode: External TTL signals are directly input to the top-level interface, adjusted by logic circuit 702, and then driven by the optical coupler of the isolated optical fiber receiver module 3 to output the optical fiber transmitter 801; the power supply of 3.3V / 5V is selected by the power switch 701 of the dual power supply voltage module 4, i.e., the DIP switch SW1, to adapt to different TTL devices.

[0067] The above description is merely an example and illustration of the structure of this utility model. Those skilled in the art can make various modifications or additions to the specific embodiments described or use similar methods to replace them, as long as they do not deviate from the structure of the utility model or exceed the scope defined in the claims, they should all fall within the protection scope of this utility model.

Claims

1. A dual-mode fiber optic photoelectric conversion device with isolation, characterized in that, It includes a PCB board with a stacked structure, and a dual-mode fiber optic photoelectric conversion circuit integrated on the PCB board; The PCB board's stacked structure, from top to bottom, includes a signal layer (11), an independent ground layer (12), a partitioned power supply layer (13), and another signal layer (11). The signal layer (11) is used to arrange dual-mode fiber optic photoelectric conversion circuits; the independent grounding layer (12) is a continuous grounding copper layer, and all grounding terminals in the signal layer (11) are connected to the independent grounding layer through metallized vias; the partitioned power supply layer (13) is provided with independent voltage regions, and the power supply terminals of each module in the signal layer (11) are connected to the corresponding independent voltage regions through metallized vias.

2. The isolated dual-mode fiber optic photoelectric conversion device according to claim 1, characterized in that, The dual-mode fiber optic photoelectric conversion circuit includes a dual-mode switching module (1) and a dual-voltage power supply module (4). The dual-mode switching module (1) receives RS485 signals and TTL signals at one end, and is connected to the RS485 signal processing module (2) and the isolated optical fiber transceiver module (3) at the other end; the RS485 signal processing module (2) is connected to the isolated optical fiber transceiver module (3); The input terminal of the dual-voltage power supply module (4) receives an external wide-voltage power supply, and the output terminal is electrically connected to the independent voltage area of ​​the partitioned power supply layer to supply power to the dual-mode switching module (1), the RS485 signal processing module (2), and the isolated optical fiber transceiver module (3).

3. The isolated dual-mode fiber optic photoelectric conversion device according to claim 1, characterized in that, The independent voltage regions of the partitioned power layer (13) include a first independent voltage region, a second independent voltage region, and an independent switching voltage region.

4. The isolated dual-mode fiber optic photoelectric conversion device according to claim 2, characterized in that, The dual-mode switching module (1) is a signal switch, which is a relay or a DIP switch.

5. The isolated dual-mode fiber optic photoelectric conversion device according to claim 2, characterized in that, The RS485 signal processing module (2) includes a processing chip U7 and a protection circuit (201); the protection circuit (201) includes a MOS transistor Q3 and a TVS transistor D3; the two ends of the TVS transistor Q3 are respectively connected to the A and B pins of the processing chip U7; the gate of the MOS transistor D3 is connected to a resistor R10 and a resistor R11 in sequence and then connected to one end of the TVS transistor Q3, and the drain is connected to a resistor R8 and then connected to the other end of the TVS transistor D3.

6. The isolated dual-mode fiber optic photoelectric conversion device according to claim 2, characterized in that, The dual-voltage power supply module (4) includes a first conversion circuit (5), a second conversion circuit (6), and a power switching circuit (7); the first conversion circuit (5) is connected to the first independent voltage region of the partitioned power layer; the second conversion circuit (6) is connected to the second independent voltage region of the partitioned power layer; and the power switching circuit (7) is connected to the independent conversion voltage region of the partitioned power layer.

7. The isolated dual-mode fiber optic photoelectric conversion device according to claim 6, characterized in that, The power switching circuit (7) includes a logic circuit (702) and a power switch (701); the logic circuit (702) includes a NAND gate U3 and an inverter U2; the NAND gate U3 is connected to the inverter U2 through a resistor R1, a MOSFET Q2, a MOSFET Q1, and a resistor R3 connected in series.

8. The isolated dual-mode fiber optic photoelectric conversion device according to claim 6, characterized in that, The first conversion circuit (5) includes a conversion chip U1 and a step-down filter circuit (501); the second conversion circuit (6) includes a voltage regulator chip U4 and a filter circuit.

9. A dual-mode fiber optic photoelectric conversion device with isolation according to claim 8, characterized in that, The conversion chip U1 is model LM2596.

10. A dual-mode fiber optic photoelectric conversion device with isolation according to claim 2, characterized in that, The isolated fiber optic transceiver module (3) includes a fiber optic receiving circuit (9) and a fiber optic transmitting circuit (8); the fiber optic transmitting circuit (8) includes an isolator (10) and a fiber optic transmitter (801) connected in sequence; the fiber optic receiving circuit (9) includes an isolator (10) and a fiber optic receiver (901) connected in sequence; the isolator (10) is connected to the RS485 signal processing module (2) and the dual-mode switching module (1).

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