High-speed serial communication interface applied to small ammeter

Abstract

The utility model relates to a high-speed serial communication interface applied to a small ammeter, which belongs to the field of electric power measurement and comprises a non-polar RS485 interface chip and a peripheral circuit. An RO port in the non-polar RS485 interface chip is connected with an input port of slave equipment (SLAVE); the RE port is suspended; the VREG port is grounded through a capacitor C1; the DI port is connected with the output port of the MCU chip; the GND port is grounded; the external circuit of the A port is connected with a power supply VREG through a pull-up resistor R3; the external circuit of the B port is grounded through a pull-down resistor R1; a resistor R2 and a static and surge protector D1 are connected between the external circuits of the A port and the B port; the port B is also connected with a PTC thermistor RT1; and the VDD port is connected with an external power supply end VIN.

Description

Technical Field

[0001] The utility model belongs to the technical field of electric power metering and communication, and relates to a high-speed serial communication interface applied to a small electric meter. Background Art

[0002] With the rapid development of smart grids, electricity meters, as key equipment for grid data collection, have increasingly higher requirements for the transmission rate, stability and reliability of communication interfaces. The RS485 communication interface has been widely used in the field of power metering due to its advantages such as high transmission rate, long-distance transmission capability and multi-node connection capability. However, when the traditional RS485 communication interface is used on small electricity meters, there are problems such as limited data transmission rate. For example, the RS485 communication interface rate usually used on electricity meters on the market is 9600bps, which is a low transmission rate and difficult to meet the needs of smart grids. Utility Model Content

[0003] In view of this, the purpose of the utility model is to provide a high-speed serial communication interface for small electric meters, which increases the data transmission rate to 115200bps through a non-polar RS485 interface chip of a low-power transceiver for RS485 communication, thereby achieving high-speed and high-stability data transmission; at the same time, the miniaturization and low cost of the interface are maintained, and it can be applied to small electric meters.

[0004] In order to achieve the above object, the utility model provides the following technical solutions:

[0005] A high-speed serial communication interface applied to a small electric meter comprises a non-polarity RS485 interface chip and a peripheral circuit; the non-polarity RS485 interface chip comprises a receiver output port RO, a receiver output enable pin RE, a 5V low voltage difference linear regulator LDO output port VREG, a driver input port DI, a ground port GND, a non-phase input and output terminal A, a reverse input and output terminal B, and a power supply port VDD; the RO port is connected to an input port RX of a slave device (SLAVE); the RE port is suspended; the VREG port is grounded through a capacitor C1; the DI port is connected to an output port TX of an MCU chip; the GND port is grounded; an external circuit of the A port is connected to a power supply VREG through a pull-up resistor R3; an external circuit of the B port is grounded through a pull-down resistor R1; a resistor R2 and an electrostatic and surge protector D1 are connected between the external circuits of the A port and the B port; the B port is also connected to a PTC thermistor RT1; and the VDD port is connected to an external power supply terminal VIN.

[0006] Furthermore, the non-polarity RS485 interface chip includes a driver D, a receiver R and a low voltage difference linear regulator LDO; the input end of the driver D is connected to the driver input port DI, and the output end is respectively connected to the in-phase input and output terminal A and the inverting input and output terminal B; the input end of the receiver R is respectively connected to the in-phase input and output terminal A and the inverting input and output terminal B, and the output end is connected to the receiver output port RO; the output end of the low voltage difference linear regulator LDO is connected to the VREG port, and the low voltage difference linear regulator LDO supplies power to the internal circuit, and provides a 5V power supply and 50mA current to the outside through the VREG pin.

[0007] Furthermore, the low-dropout linear regulator LDO is connected to an overcurrent protection and short-circuit protection circuit. When the output current exceeds 250mA, the overcurrent protection is activated; when VREG is short-circuited to ground, the short-circuit protection circuit limits the output current to 10mA.

[0008] Furthermore, when the RE pin is left floating, it can automatically determine the sending and receiving relationship between the Master and the Slave and identify the sending and receiving direction. In the idle condition of the automatic direction identification state, DI is set to a high potential.

[0009] Furthermore, the package type of the non-polarity RS485 interface chip is SOP8 or ESOP8.

[0010] The beneficial effect of the utility model is that the high-speed serial communication interface for small electric meters provided by the scheme, namely the non-polarity RS485 interface chip GS1485ND, realizes high-speed and high-stability data transmission through optimized design, while maintaining the miniaturization and low cost of the interface, so that it can be applied to small electric meters. After experimental verification, the communication interface increases the data transmission rate to 115200bps, which can adapt to different communication rate requirements and provide a high-speed communication solution for small electric meters in smart grids.

[0011] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and will be apparent to those skilled in the art based on the following examination and research, or can be taught from the practice of the present invention to some extent. The objectives and other advantages of the present invention can be achieved and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to make the purpose, technical solution and advantages of the utility model clearer, the utility model will be described in detail below in conjunction with the accompanying drawings, in which:

[0013] Figure 1The pin diagram of the non-polarity RS485 interface chip, where (a) is SOP8 package and (b) is ESOP8 package;

[0014] Figure 2 This is a schematic diagram of the internal structure of the non-polarity RS485 interface chip;

[0015] Figure 3 It is the structure diagram of the communication interface circuit;

[0016] Figure 4 The three views of the non-polarity RS485 interface chip SOP8 package, where (a) is the front view, (b) is the left view, and (c) is the top view;

[0017] Figure 5 The three views of the non-polarity RS485 interface chip ESOP8 package, where (a) is the front view, (b) is the left view, and (c) is the top view. (a) is the front view, (b) is the left view, (c) is the bottom view, (d) is the top view, and (e) is the size of the copper foil at the bottom of the chip. DETAILED DESCRIPTION

[0018] The following describes the implementation of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and the features in the embodiments can be combined with each other without conflict.

[0019] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present utility model. In order to better illustrate the embodiments of the present utility model, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of the actual product. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0020] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "back" and the like indicate directions or positional relationships, they are based on the directions or positional relationships shown in the drawings, which are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as a limitation on the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0021] Figure 1 The figure shows an interface chip for a high-speed serial communication interface used in a small electric meter (two package types, Figure 1 (a) is SOP8, (b) is ESOP8). This interface chip is a non-polarity RS485 interface chip. The function pins of this chip are defined as follows: Figure 1 And make corresponding explanations as follows:

[0022] 1.RO is the output of the receiving end. When receiving is enabled, VA-VB>-50mV, the output is high level; VA-VB<-200mV, the output is low level; when sending, RO outputs high impedance.

[0023] 2.RE is the enable pin. When it is low level, the chip is in receiving state; when it is high level, it is in sending state; when it is floating, the state of the chip is automatically controlled by DI.

[0024] 3. VREG is 5V LDO output, external 1uF capacitor.

[0025] 4.DI is the data input. When in idle state, DI must be driven with a high level.

[0026] 5.GND ground.

[0027] 6.A is the non-inverting input / output terminal.

[0028] 7.B is the inverting input / output terminal.

[0029] 8. VDD is the power supply and can accept 5~28V input.

[0030] The internal structure of this non-polarity RS485 interface chip is as follows Figure 2 As shown, the most important ones are the receiver R and the driver D, and the others are configuration circuit modules.

[0031] This non-polarity RS485 interface chip has the following characteristics:

[0032] This non-polarity RS485 interface chip is a low-power transceiver for RS485 communication, with a receiver input impedance of 1 / 8 unit load, so that there can be up to 256 transceivers on the bus to form a half-duplex communication network. The chip's maximum transmission rate is greater than 500kbps.

[0033] The non-polarity RS485 interface chip has a driver and a receiver. The output driver is designed with slew rate limitation, which enables the chip to reduce EMI and signal reflection effects and achieve error-free data transmission.

[0034] This non-polarity RS485 interface chip can work normally in a wide range of power supply voltage from +5V to +28V. It integrates a low voltage drop linear regulator LDO internally, which can provide a 5V / 50mA regulated power supply for external circuits. Under isolated application conditions, this regulated power supply can provide power for peripheral devices such as optocouplers.

[0035] This non-polarity RS485 interface chip combines the DE / RE interface into RE. The RE pin can control reception and transmission, but it can also be left floating. When left floating, the chip automatically determines the direction of transmission and reception, making the chip particularly suitable for isolation applications, requiring only two optocouplers.

[0036] This non-polarity RS485 interface chip supports non-polarity connection. You only need to add pull-up / down resistors on the Master end, and the Slave end can automatically determine the polarity of the A / B port, which is convenient for installation. And the output end does not need to be connected with external pull-up / down resistors, and automatically performs failure protection, which can further save system costs.

[0037] The static power consumption of this non-polar RS485 interface chip is less than 500μA. The driver has short-circuit current limitation, which will automatically limit the output current under output short-circuit conditions. It also has an internal over-temperature protection circuit, which can shut down the driver output through the thermal shutdown circuit to prevent thermal damage.

[0038] Figure 3 The figure shows the structure of the communication interface circuit. The circuit includes the main chip, the non-polarity RS485 interface chip and the peripheral circuit. The RS485 interface chip performs the communication function between the master / slave devices. The A / B terminal is connected to the Master device, and the RO / DI terminal is connected to the Slave device. The peripheral circuit device selection and connection method are as follows Figure 3 The specific markings are as follows:

[0039] The RO port is connected to the input port RX of the slave device (SLAVE).

[0040] The RE port is left unconnected, and the chip automatically identifies the transmit and receive status.

[0041] The VREG port is grounded through capacitor C1. The capacitor is 1uF / 10V and is used for filtering and stabilizing the power output.

[0042] The DI port is connected to the output port TX of the MCU chip.

[0043] The GND port is connected to ground.

[0044] A pull-up resistor R3 (typical resistance is 1KΩ or 2KΩ) ​​needs to be connected to the external circuit of port A, and the power supply VREG is connected through the pull-up resistor.

[0045] A pull-down resistor R1 (typical resistance is 1KΩ or 2KΩ) ​​needs to be connected to the external circuit of port B and grounded through the pull-down resistor.

[0046] Between the external circuits of ports A and B, resistor R2 (typical resistance is 120Ω, which can be adjusted accordingly in different application environments) and an electrostatic and surge protector (TVS-ESD) are connected, represented by D1, and the protector model is SMBJ6.0CA; and a PTC thermistor needs to be connected to the outermost side of port B, represented by RT1, and its model is MZ11-10A300-600RM.

[0047] The VDD port is connected to the external power supply terminal VIN.

[0048] like Figure 4 As shown in (a)-(c), the dimensions in the figure are shown in Table 1.

[0049] Table 1

[0050]

[0051] like Figure 5 As shown in (a)-(e), the dimensions in the figure are shown in Table 2.

[0052] Table 2

[0053]

[0054]

[0055] in Figure 5 (e) is the size of the copper foil at the bottom of the chip. When the chip is soldered to the PCB, the copper foil is a soldering point, which is soldered to the PCB and also plays a role in heat dissipation.

[0056] In the embodiment of the utility model, the non-polar RS485 interface chip will automatically connect pull-up / down resistors according to the bus polarity, and the A and B ports do not need to be connected to pull-up / down resistors. However, GS1485ND can also be used in the ordinary polar RS485 communication mode, and the external pull-up / down resistors will not affect its use.

[0057] In the embodiment of the utility model, the non-polarity RS485 interface chip needs to pay attention to two points when implementing non-polarity communication in the electric meter solution: (1) There must be a pair of pull-up / pull-down resistors (typical resistance 1KΩ or 2KΩ, used in the collector) on the bus, and no pull-up / pull-down resistors are added to the RS485 communication port of each individual electric meter; (2) The communication rate must be greater than 20Hz, and the high level or low level duration of the communication must be less than 120mS.

[0058] In the embodiment of the utility model, the LDO integrated inside the non-polarity RS485 interface chip not only supplies power to the internal circuit, but also provides a 5V power supply to the outside through the VREG pin. The LDO can provide an additional 50mA current externally. If this current value is exceeded, the load current of the A / B port needs to be reduced accordingly. The LDO also integrates overcurrent protection and short-circuit protection functions. When the output current exceeds 250mA, the overcurrent protection will start and clamp the output current. The integrated short-circuit protection circuit limits the output current of the LDO to 10mA when VREG is short-circuited to ground.

[0059] In the embodiment of the utility model, the non-polarity RS485 interface chip has an automatic direction recognition function. When the RE pin is suspended, the chip will enter the automatic direction recognition state. This function can reduce one optocoupler in the case of isolation application. In the automatic direction recognition state, under idle conditions, DI must be set to a high potential.

[0060] In the embodiment of the utility model, for non-isolated application solutions, if the system is powered by a 5V power supply, VDD and VREG can be short-circuited together and the 5V power supply can be directly used, which can reduce the heat consumption of the chip.

[0061] In the embodiment of the utility model, for the RS485 network with heavy load, it is recommended to use ESOP8 package and consider heat dissipation design during PCB design.

[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the utility model rather than to limit it. Although the utility model has been described in detail with reference to the preferred embodiments, ordinary technicians in the field should understand that the technical solution of the utility model can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the utility model.

Claims

1. A high-speed serial communication interface for small electric meters, characterized in that: Including non-polarity RS485 interface chip and peripheral circuit; The non-polarity RS485 interface chip includes a receiver output port RO, a receiver output enable pin RE, a 5V low-voltage difference linear regulator LDO output port VREG, a driver input port DI, a ground port GND, a non-inverting input and output terminal A, an inverting input and output terminal B, and a power port VDD; the receiver output port RO is connected to the input port RX of the slave device SLAVE; the receiver output enable pin RE is suspended; the 5V low-voltage difference linear regulator LDO output port VREG is grounded through a capacitor C1; the driver input port DI is connected to the output port TX of the MCU chip; the GND port is grounded; the external circuit of port A is connected to the power supply VREG through a pull-up resistor R3; the external circuit of port B is grounded through a pull-down resistor R1; a resistor R2 and an electrostatic and surge protector D1 are connected between the external circuits of port A and port B; port B is also connected to a PTC thermistor RT1; and the VDD port is connected to an external power supply terminal VIN.

2. The high-speed serial communication interface for small electric meters according to claim 1, characterized in that: The non-polarity RS485 interface chip includes a driver D, a receiver R and a low-voltage difference linear regulator LDO; the input end of the driver D is connected to the driver input port DI, and the output end is respectively connected to the in-phase input and output terminal A and the inverting input and output terminal B; the input end of the receiver R is respectively connected to the in-phase input and output terminal A and the inverting input and output terminal B, and the output end is connected to the receiver output port RO; the output end of the low-voltage difference linear regulator LDO is connected to the VREG port, the low-voltage difference linear regulator LDO supplies power to the internal circuit, and provides a 5V power supply and 50mA current to the outside through the VREG pin.

3. The high-speed serial communication interface for small electric meters according to claim 2, characterized in that: The low voltage difference linear regulator LDO is connected to an overcurrent protection and short circuit protection circuit. When the output current exceeds 250mA, the overcurrent protection is activated; when VREG is short-circuited to the ground, the short circuit protection circuit limits the output current to 10mA.

4. The high-speed serial communication interface for small electric meters according to claim 1, characterized in that: When the RE pin is left floating, it can automatically determine the sending and receiving relationship between the Master and Slave and identify the sending and receiving direction. In the idle condition of the automatic direction identification state, DI is set to a high potential.

5. The high-speed serial communication interface for small electric meters according to claim 1, characterized in that: The package type of the non-polarity RS485 interface chip is SOP8 or ESOP8.

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