Background technology
M-BUS(Meter-BUS EN1434-3) is consumer instrument current international practice standard.It is a kind of economical and practical fieldbus, has good opening, its topological structure is bus structures, adopt common two core cable to connect, finish the function of power supply power supply and data communication simultaneously, when connecting, need not distinguish polarity, can be according to randomly topologically structured cable wiring manufacture, its construction cost and difficulty descend greatly.
M-BUS bus electric interfaces should meet the following requirements:
When slave station was powered by main website, each slave station obtained to be not more than the electric current of 2mA, and the main website driving force should be not less than 64 slave stations.
Main website to the message transmission of slave station is to realize by the mode that level changes.During mark (logic level is " 1 "): the bus voltage of bus voltage during than spacing is greater than 10V, and bus voltage is smaller or equal to 42V; During spacing (logic level is " 0 "): bus voltage should be greater than 12V.
Slave station to master information transmission is that the variation by the slave station size of current realizes.During mark (logic level " 1 "): marking current is 0mA~1.5mA; During spacing (logic level " 0 "): spacing current is to increase about 11mA~20mA on the basis of marking current value; When bus was idle, master and slave station should keep mark condition.
Guard grating claims safe retainer again, be to be connected between the intrinsically safe circuit in the immaterial safety circuit of place of safety and hazardous area, can be between place of safety and hazardous area the two-way transmission signal of telecommunication, and can limit the energy transmission of place of safety that barrier for some reason causes to the hazardous area, be limited in device in certain safe range with supplying with the voltage of intrinsically safe circuit or electric current.
The essential safe type guard grating is applied in the design of intrinsic safe explosion-proof system, it is to be installed on harbor and to contain intrinsically safe circuit and the device of non-intrinsically safe circuit, limited the energy that is sent to on-the-spot intrinsic safety loop by current limliting and pressure limiting circuit in the circuit, thereby the dangerous energy that prevents non-intrinsically safe circuit seals in intrinsically safe circuit, it is called associate device in the intrinsic safe explosion-proof system, be the important component part of intrinsic safety system.The Generally Recognized as safe grid have Zener type, isolated.
The Zener type guard grating adopts fast acting fuse, current-limiting resistance or pressure limiting diode to limit with the electric flux to input in the circuit, thereby guarantees to output to the energy in hazardous area.
Isolating safety grid has adopted the circuit structure with input, output and the mutual electrical isolation of power supply three party, meets the requirement of essential safety restriction energy simultaneously.
In the M-BUS bus system, main website is that non-intrinsic safety equipment is positioned at the place of safety, and slave station needs to be provided with between main website and the slave station guard grating that meets the intrinsic safety requirement for intrinsic safety equipment is positioned at the hazardous area, it will meet the M-BUS bus standard, can not influence master-salve station work and between communication.
Existing guard grating is applied on the M-BUS bus, has the following disadvantages:
1, Zener type guard grating, bigger current-limiting resistance, excessive voltage drop causes bus-powered deficiency, reduces the ability that drives slave station; Internal circuit does not meet the M-BUS bus standard, and master-salve station cisco unity malfunction or master-salve station can not be communicated by letter; When fault, need to change fuse or guard grating, operation is extremely inconvenient, increases maintenance cost.
2, isolating safety grid, the output power supply capacity is relatively poor to cause driving that slave station quantity reduces or communication distance reduces; Do not meet the M-BUS bus standard, when being applied on the M-BUS bus, influence communicating by letter between main website and the slave station.
Summary of the invention
An object of the present invention is to remedy the deficiencies in the prior art; a kind of M-BUS bus intrinsic safety barriter, is provided; can carry out multistage pressure limiting and overcurrent protection to the input of M-BUS bus, output meets the essential safety requirement, and it meets the M-BUS bus standard and can be used for the M-BUS bus.
Another object of the present invention is that M-BUS bus run quantity is expanded, and a main website can drive many M-BUS buses in turn, has expanded the capacity of M-BUS bus system, has reduced equipment cost.
The present invention is achieved through the following technical solutions:
A kind of M-BUS bus intrinsic safety barriter,, described bus intrinsic safety barriter, are connected between the main website and slave station of M-BUS bus system; It is characterized in that described bus intrinsic safety barriter, comprises the following circuit that connects successively:
Input stage realizes the polar switching of M-BUS bus input, and limits the short circuit current of M-BUS bus;
Protected level
, comprising pressure limiting circuit and current foldback circuit, its input connects the output of described input stage, this protected level
Output connect protected level
Input;
Protected level
, described protected level
With described protected level
Connect described protected level in turn
Also comprise a pressure limiting and current foldback circuit, with described protected level
Constitute the redundancy protecting of M-BUS bus together.
If the more than one passage of M-BUS bus requirements, then described M-BUS bus intrinsic safety barriter, also further comprises output stage, and the input of this output stage connects described protected level
Output, described output stage is a number of channels expanded circuit for combination electronic switch matrix or mechanical switch matrix, realizes the expansion from a passage to a plurality of passages, increases the quantity that drives slave station.Certainly, if only need a passage, shouldn't this level.
Input stage comprises the current-limiting resistance of a bridge-type change-over circuit and a low capacity.The bridge-type change-over circuit is realized the nonpolarity of M-BUS bus input, when current-limiting resistance makes output short-circuit, very big short circuit current can not occur.
Protected level
And protected level
Be two identical circuit modules.It comprises a current sampling resistor, an electronic switch, a diode, a control chip and other components and parts, and the electrical characteristic of whole modular circuit meets the M-BUS standard.Control chip monitors output end voltage, when overpressure situation occurring, output voltage is adjusted in the voltage of setting by regulating electronic switch, also monitor the pressure drop on the sampling resistor of input simultaneously, when overcurrent condition occurring, the control electronic switch disconnects and being connected of exporting.No matter overvoltage or over current fault have taken place, if fault continues always, the inner integrated fault timer of control chip can guarantee that all electronic switch fast and reliable ground turn-offs so, and the diode that is connected on output prevents the input of reverse voltage.
Output stage comprises Signal Spacing decoding circuit and switch matrix circuit.The channel selecting signal of input is carried out that photoelectricity is isolated, behind the decoder circuit, can select a certain channel switch conducting, make it and protected level
Output connects, and reaches a passage M-BUS bus is expanded to multichannel purpose.Certainly, the quantity of extended channel can increase or reduce as required.
The present invention adopts said structure, and its electrical characteristic meets the M-BUS standard, can directly be applied on the M-BUS bus, and two-stage protected level circuit forms function of redundancy protection, and when one-level broke down therein, another grade can be born defencive function.Every grade all has independently pressure limiting and overcurrent protection function.Can expand the M-BUS number of channels by output stage.
Beneficial effect of the present invention: limit the energy of input effectively, make intrinsically safe equipment can be applied to the hazardous area safely; Meet the M-BUS bus standard, can directly apply on the M-BUS bus; Input and output pressure drop are little; Fragile element such as no fuse is safeguarded and need do not changed substantially; One passage M-BUS bus can be expanded to multichannel, reduce cost; Also can be used as the Generally Recognized as safe grid uses.
Embodiment
The present invention is further illustrated below in conjunction with instantiation and accompanying drawing
M-BUS bus standard regulation: the M-BUS bus is non-polar, main website be by the variation of control bus voltage (when sending logical one, output HIGH voltage; When sending logical zero, output LOW voltage) send data to slave station, the scope of voltage transformation is greater than 10V.Slave station is that (when sending logical one, it is constant to keep bus current by the variation of control bus electric current; When sending logical zero, make bus current increase a fixed value) send data, scope 11mA~20mA that electric current changes to main website.
As shown in Figure 1, M-BUS bus intrinsic safety barriter, comprises the following circuit that connects successively:
Input stage has the circuit of importing polar switching and current-limiting resistance;
Protected level
, have the circuit of pressure limiting and overcurrent protection function;
Protected level
, have the circuit of pressure limiting and overcurrent protection function;
Output stage, combination electronic switch matrix or mechanical switch matrix are number of channels expanded circuits, realize the expansion from a passage to a plurality of passages, increase the quantity that drives slave station, if only need a passage, this grade circuit shouldn't.
In conjunction with the accompanying drawings, the particular circuit configurations of circuit modules at different levels is analyzed as follows:
As shown in Figure 2, input stage one end connects the input of M-BUS bus, and the positive and negative electrode of the other end is connected respectively to protected level
Positive and negative electrode.It comprises the current-limiting resistance of a bridge-type change-over circuit and a low capacity, and after the M-BUS bus realized reversal through bridge-type change-over circuit D1, positive pole was connected to protected level through a current-limiting resistance R1
Positive pole, negative pole is directly connected to protected level
Negative pole.Input stage has realized the nonpolarity input of M-BUS bus, the maximum short circuit current when having limited output short-circuit.
Protected level
And protected level
Be identical circuit structure, as shown in Figure 3, in the present embodiment, the operating voltage scope of design of protected level is 9V to 42V, and the pressure limiting point is designed to 36V, crosses flow point and is designed to 0.2A.
As shown in Figure 3, with protected level
For example illustrates its circuit structure: protected level
Comprise a current sampling resistor R3, an electronic switch (MOSFET manages Q1), diode D2, a control chip U1 and other components and parts.The positive pole of input series current sampling resistor R3, MOSFET is successively managed Q1, diode D2 to output, the
pin 7 of control chip U1 and
pin 8 are connected respectively to the two ends of current sampling resistor R3, the
pin 5 of control chip U1 is by
resistance R 4 driven MOS FET pipe Q1, the conducting or the shutoff of control input and output, be connected to the both positive and negative polarity of the output behind the MOSFET pipe Q1 after voltage
sample resistance R 5 and the R6 series connection, centre tap is connected to the
pin 2 of control chip U1, and
resistance R 2 and C1 are the control chip U1 necessary components and parts of working.
Its operation principle is: the pin 2 monitor voltage sampling resistor R5 of control chip U1 and the feedback voltage of R6, and when input voltage during greater than 36V, its pin 5 output control signals are regulated MOSFET pipe Q1 output are adjusted to 36V; The pressure drop at control chip U1 pin 7 and pin 8 standby current sampling resistor R3 two ends, when through the electric current of R3 during greater than 0.2A, the pressure drop at current sampling resistor R3 two ends surpasses set point, and its pin 5 output control signals disconnect and being connected of exporting MOSFET pipe Q1; Diode D2 prevents the input of reverse voltage.
In the present embodiment, control chip U2 selects LT4356-3 for use.
Protected level
The positive pole of output and protected level
The positive pole of input connects, protected level
The negative pole of output and protected level
The negative pole of input connects, and two-stage protected level circuit forms function of redundancy protection, and when one-level broke down therein, another grade can be born defencive function.
Output stage comprises Signal Spacing decoding circuit and switch matrix circuit.In the present embodiment, output stage expands to 16 passages, and 4 the tunnel select signal to select corresponding passage by the 4-16 decoder.
As shown in Figure 4,4 paths drive the light lotus root by a resistance after selecting signal to pass through the reversal of bridge-type change-over circuit respectively, and the signal after the light lotus root isolates is input to the input of chip U5,16 road signal driving switch matrix circuits after decoding output.
As shown in Figure 5, be the switch matrix circuit principle schematic, comprise 16 identical channel switchs, the input of each channel switch and protected level
Output connect, output is connected to lead-out terminal, control end is connected with isolation decoding circuit output.By channel switch, control signal can be controlled protected level simultaneously
The conducting or the shutoff of output head anode, negative pole and lead-out terminal.Channel switch is a double-pole switch.
In the present embodiment, the 1st channel switch with switch matrix circuit is that example illustrates its circuit structure principle.
As shown in Figure 6A, be the 1st channel switching circuit execution mode one principle schematic of switch matrix circuit.This circuit is made up of 4 electronic switches: the 1st electronic switch of being made up of resistance R A1, RA4 and triode QA2, manage the 2nd electronic switch that QA1 forms by resistance R A2, RA3 and MOSFET, by diode DA1, the 3rd electronic switch that resistance R A5 and triode QA3 form is managed the 4th electronic switch that QA4 forms by resistance R A6, RA7 and MOSFET; Wherein the end of resistance R A4 is connected to the base stage of triode QA2, and the other end is connected to the passage output signal of Signal Spacing decoding circuit; The source class of MOSFET pipe QA1 is connected to protected level
The negative pole of output drains to the negative pole output of this passage, is connected to lead-out terminal; The source class of MOSFET pipe QA4 is connected to protected level
The positive pole of output drains to the positive pole output of this passage, is connected to lead-out terminal.
Operation principle is: input control signal is controlled the 1st electronic switch conducting or shutoff; the 1st electronic switch is controlled the 2nd electronic switch and the 3rd electronic switch conducting or shutoff; the 3rd electronic switch is controlled the 4th electronic switch conducting or shutoff, and promptly input control signal is controlled protected level simultaneously
The conducting or the shutoff of output head anode, negative pole and lead-out terminal.
Shown in Fig. 6 B, be the 1st channel switching circuit execution mode two principle schematic of switch matrix circuit.The electronic switch of being made up of resistance R A8, RA9 and triode QA5 drives relay K A1, and DA2 plays afterflow effect, protected level with relay K A1 diode connected in parallel
The positive pole of output and the common port that negative pole is connected respectively to relay K A1, the Chang Kaiduan of relay K A1 is connected respectively to the lead-out terminal of this passage.Input control signal drives relay control protected level by electronic switch
The conducting or the shutoff of output head anode, negative pole and lead-out terminal.
The present patent application people has done detailed explanation and description in conjunction with Figure of description to embodiments of the invention; but those skilled in the art should understand that; above embodiment only is the preferred embodiments of the invention; detailed explanation is just in order to help the reader to understand spirit of the present invention better; and be not limiting the scope of the invention; on the contrary, any any improvement or modification of being done based on invention spirit of the present invention all should drop within protection scope of the present invention.