CN203607820U - Over-current and overvoltage protective circuit used for 4-20mA current input circuit - Google Patents

Over-current and overvoltage protective circuit used for 4-20mA current input circuit Download PDF

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Publication number
CN203607820U
CN203607820U CN201320800450.XU CN201320800450U CN203607820U CN 203607820 U CN203607820 U CN 203607820U CN 201320800450 U CN201320800450 U CN 201320800450U CN 203607820 U CN203607820 U CN 203607820U
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voltage
signal
current
input
module
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CN201320800450.XU
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Chinese (zh)
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张保建
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Automation information (China) Co., Ltd.
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XIATE WONCOS AUTOMATION (HANGZHOU) CO Ltd
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Abstract

The utility model discloses an over-current and overvoltage protective circuit used for a 4-20mA current input circuit. The over-current and overvoltage protective circuit comprises a filtering rectification module which filters a transient overvoltage pulse interference signal in an input signal and prevents reversal connection of the input signal; a switch control module which receives a current signal outputted by the filtering rectification module and controls on and off of a current loop; a voltage acquisition module which converts the current signal from the switch control module into a corresponding voltage signal; and a signal monitoring module which monitors the voltage signal acquired by the voltage acquisition module, the voltage is compared with a preset voltage threshold value, and if the voltage surpasses the preset voltage threshold value, the current loop is disconnected by the switch control module through control, and the preset threshold voltage can be set according to requirements. According to the input over-current and overvoltage protective circuit, over-current and overvoltage protective functions can be realized so that the circuit is safe and reliable and has quite low influence on the input signal.

Description

A kind of overcurrent excess voltage protection for 4-20mA current input circuit
Technical field
The utility model relates to a kind of protective circuit, particularly a kind of overcurrent excess voltage protection for 4-20mA current input circuit.
Background technology
In commercial Application, in order to overcome the impact of disturbing signal, conventionally adopt 4-20mA electric current to carry out signal transmission.But, in actual application, can the 12V of system or 24V voltage signal be linked into input signal terminal because of misoperation unavoidably, or export large electric current because of signal source fault, or holding wire suffer thunderbolt high voltage is coupled to input signal terminal, cause signal input device to be burnt, signal collecting device is malfunctioning, when serious, can cause whole system paralysis, cause direct or indirect economic loss.
For fear of overcurrent-overvoltage, some has added independently input protection module.Than (patent No.: 200810301869.4), input voltage is divided in voltage comparator U1 by resistance R 1, R2, the output signal of U1 arrives switching circuit below, turn-offs the 5V_SB signal of rear class while there is overvoltage signal as shown in Figure 1.Some utilizes LM317L to realize overcurrent overvoltage protection as shown in Figure 2: electric current flow into LM317L from VI; flow out to R1 from Output pin; because the voltage on inner Adjustment pin is limited in 1.25V; the electric current of the output of LM317L is limited in Ilimit=1.25/R1, and electric current is limited in 1.25/R1.
But these protective circuits are limited to the function of overvoltage and overcurrent protection, and larger on the input impedance impact of circuit, easily cause acquisition precision variation, the input impedance of input signal to become large harmful effect.In Fig. 1; the sampling of front end electric resistance partial pressure and switching circuit are below separate cascade connections; what turn-off is also late-class circuit; there is no the incoming end open circuit at overvoltage signal, if there is very high voltage to access for a long time, after protective circuit effect; owing to there is no the access of disconnecting external voltage; large electric current, by Q1, probably burns out Q1, finally loses defencive function.And in circuit as shown in Figure 2; this scheme only relies on self the 1.25V limiting voltage of LM317L to realize current-limiting function; when input Input termination enters too high voltages; the tolerance range that has exceeded chip LM317, LM317L itself will be damaged, finally also will lose defencive function; simultaneously; because of LM317L internal circuit impact, input circuit impedance is shown as non-linear, the conference of input circuit impedance exceedes 300 ohm.
Utility model content
Technical problem to be solved in the utility model is, in industry spot 4-20mA current signal acquisition applications, sometimes because of misoperation or signal source fault, or in signal, be coupled to instantaneous overvoltage signal, make input signal produce overvoltage or overcurrent signal, thereby cause 4-20mA electric current input equipment fault.
The utility model is to solve the problems of the technologies described above the technical scheme adopting to be to provide a kind of overcurrent excess voltage protection for 4-20mA current input circuit, comprising:
Filter rectification module: the instantaneous overvoltage pulse signal in filtering input signal, and anti-stop signal reversal connection;
Switch control module: receive the current signal of described filter rectification module output and control the break-make of this current signal;
Voltage acquisition module: will change into corresponding voltage signal from the current signal of switch control module; And
Signal monitoring module: monitor the voltage signal that collects of voltage acquisition module, and with predetermined threshold value voltage ratio, if exceed predetermined voltage threshold, control immediately described switch control module turn-off current loop.The above-mentioned overcurrent excess voltage protection for 4-20mA current input circuit; wherein; described filter rectification module comprises two-way TVS pipe D1, filter capacitor C1 and anti-reverse diode D2, is connected to the positive pole of anti-reverse diode D2 after described two-way TVS pipe D1 is in parallel with filter capacitor C1.
The above-mentioned overcurrent excess voltage protection for 4-20mA current input circuit, wherein, described switch control module is metal-oxide-semiconductor Q1, and described voltage acquisition module is sampling resistor R3, and described signal monitoring module comprises voltage comparator U1, divider resistance R1 and divider resistance R2; The drain electrode of described metal-oxide-semiconductor Q1 is connected to the negative pole of anti-reverse diode D2, the grid of described metal-oxide-semiconductor Q1 is connected to the output of voltage comparator U1, the source electrode of described metal-oxide-semiconductor Q1 is connected to sampling resistor R3, be connected to the reverse input end of voltage comparator U1 simultaneously, the positive input of described voltage comparator U1 is connected to one end of electric resistance partial pressure resistance R 1 and divider resistance R2 simultaneously, the other end of described divider resistance R1 is connected to power end V_Set, and the other end of described divider resistance R2 is connected to earth terminal GND.
The above-mentioned overcurrent excess voltage protection for 4-20mA current input circuit, wherein, described metal-oxide-semiconductor Q1 is N channel enhancement metal-oxide-semiconductor.
The utility model contrast prior art has following beneficial effect: the overcurrent excess voltage protection for 4-20mA current input circuit that the utility model provides, realize overcurrent, superpotential defencive function by filter rectification module, voltage acquisition module, switch control module and signal monitoring module; This protective circuit is little on input signal impact, and the error effect maximum of input current is less than to 1uA; Protective circuit is very little to the impedance influences of input circuit, makes input circuit can keep low input impedance, lower to the requirement of signal source; Fast response time, when overcurrent overvoltage signal appears in input signal, moment thoroughly disconnects input circuit, makes overcurrent overvoltage signal and protected isolation of system, effectively protects late-class circuit, and reliability is high; Can effectively prevent that thunderbolt or transient overvoltage pulse interference signal are input to late-class circuit simultaneously; This circuit uses components and parts simple, and implementation cost is cheap.
Accompanying drawing explanation
Fig. 1 is existing over-voltage protection function block diagram;
Fig. 2 is the existing overcurrent protection block diagram based on LM317L;
Fig. 3 is the utility model input overcurrent excess voltage protection block diagram;
Fig. 4 is the utility model input overcurrent excess voltage protection figure.
In figure:
1 filter rectification module 2 switch control module 3 signal monitoring modules
4 voltage acquisition modules
Embodiment
Below in conjunction with drawings and Examples, the utility model will be further described.
Fig. 3 is the utility model input overcurrent excess voltage protection block diagram.
Refer to Fig. 3, the overcurrent excess voltage protection for 4-20mA current input circuit that the utility model provides comprises:
Filter rectification module 1: the instantaneous overvoltage pulse interference signal in filtering input signal, and anti-stop signal reversal connection;
Switch control module 2: the current signal that the rectification module 1 that accepts filter is exported the break-make of controlling this current circuit;
Voltage acquisition module 4: will change into corresponding voltage signal from the current signal of switch control module 2; And
Signal monitoring module 3: monitor the voltage signal that collects of voltage acquisition module 4, and with predetermined voltage threshold comparison, if exceed predetermined voltage threshold, control immediately described switch control module 2 turn-off current loops.Described voltage threshold can regulate as required.
The overcurrent excess voltage protection operation principle for 4-20mA current input circuit that the utility model provides is as follows: first by filter rectification module 1, the curtage signal of input is processed, prevent that transient overvoltage pulse interference signal is input to late-class circuit, and prevent input signal reversal connection; Then input signal flows into switch control module 2, and switch control module 2 is in the time of opening, and conduction impedance is extremely low, finally enters into voltage acquisition module 4.Voltage acquisition module 4 is by a sampling resistor, current signal is changed into corresponding voltage signal, the moment monitors the voltage signal that voltage acquisition module 4 collects to signal monitoring module 3, and with predetermined voltage threshold comparison, once the voltage that voltage acquisition module collects exceedes set point, moment makes switch control module 2 turn-off current loops, then signal monitoring module 3 is by the voltage that monitoring voltage acquisition module 4 collects again, now because circuit disconnects, the voltage collecting should be 0V, so, signal monitoring module 3 makes switch control module 2 circuit turn-ons, then signal monitoring module 3 is by the voltage that monitoring voltage acquisition module 4 collects again, if the voltage now collecting is still higher than predetermined voltage threshold, moment makes switch control module 2 open circuit loops again, on the contrary, if the voltage now collecting, lower than predetermined voltage threshold, does not operate switch control module 2, reenter voltage detection module 4 and wait for result of determination, so circulation, make voltage acquisition to voltage be controlled in below predetermined voltage threshold.
Fig. 4 is the utility model input overcurrent excess voltage protection figure.
Please continue referring to Fig. 4, filter rectification module 1 in the utility model can be made up of two-way TVS pipe D1, a filter capacitor C1 and anti-reverse diode D2, switch control module 2 can be selected N channel enhancement metal-oxide-semiconductor Q1, signal monitoring module 3 adopts voltage comparator U1 and divider resistance R1, R2 composition, and voltage acquisition module 4 adopts sampling resistor R3.Concrete connected mode is as follows: the positive pole that is connected to anti-reverse diode D2 after two-way TVS pipe D1 is in parallel with filter capacitor C1, the negative pole of anti-reverse diode D2 is connected to the drain electrode of metal-oxide-semiconductor Q1, the grid of Q1 is connected to the output of voltage comparator U1, the source electrode of Q1 is connected to sampling resistor R3, be connected to the reverse input end of voltage comparator U1 simultaneously, the positive input of voltage comparator U1 is connected to one end of divider resistance R1 and R2 simultaneously, the other end of divider resistance R1 is connected to power end V_Set, and the other end of divider resistance R2 is connected to earth terminal GND.Divider resistance R2 is upper is threshold voltage to the dividing potential drop of V_Set.
The utility model is as follows for the overcurrent excess voltage protection course of work of 4-20mA current input circuit: when normal 4-20mA current signal input, via the rectification of two-way TVS pipe D1 and filter capacitor C1 filtering and anti-reverse diode D2, flow into the drain electrode of Q1, then out flow into sampling resistor R3 from source electrode, on sampling resistor R3, be converted to voltage signal, be the voltage that voltage acquisition module 4 collects, and this voltage is sent to late-class circuit; The supply power voltage of voltage comparator U1 is generally more than or equal to 3.3V, and in the situation due to circuit initial input state and the normal 4-20mA signal of input, adopt the voltage at resistance R 3 two ends to be all less than the threshold voltage Vset that excess voltage protection is set, the output voltage that guarantees thus voltage comparator U1 is high level in the time that circuit input signal is normal, the supply power voltage that now output voltage is voltage comparator; In order to leave surplus, sampling resistor R3 is taken as 75 ohm, and circuit protection voltage threshold is set as 2.5V, and in the time that 20mA electric current is inputted, the voltage collecting on sampling resistor R3 is: U=0.02 × 75=1.5V; Under normal 4-20mA current signal input condition, voltage comparator U1 is because anodal input voltage is greater than negative pole input voltage, be output as high level, now for metal-oxide-semiconductor Q1, grid voltage equals 3.3V, and source voltage is less than or equal to 1.5V, and metal-oxide-semiconductor grid voltage is greater than source voltage, be Vgs>1.8V, conducting between the drain electrode of Q1 and source electrode.
In the time there is overcurrent signal input, by the filter rectification processing of two-way TVS pipe D1, filter capacitor C1, anti-reverse diode D2, on Zhongdao sampling resistor R3, change into voltage, this voltage is connected to the reverse input end of voltage comparator U1, the reverse input voltage of voltage comparator U1 and the comparison of forward input voltage, because the forward input voltage of voltage comparator U1 obtains by two electric resistance partial pressures, so the forward input voltage of voltage comparator U1 is fixed, this voltage can be set by the resistance value that regulates R1, R2.In the time that the voltage on sampling resistor R3 is greater than the forward input voltage of U1, the output of voltage comparator U1 is output as low level immediately, the grid voltage of metal-oxide-semiconductor Q1 is less than source voltage, between the source electrode of metal-oxide-semiconductor Q1 and drain electrode, disconnect, be that current circuit disconnects, voltage on sampling resistor R3 becomes 0V, be less than the anodal input voltage of U1, so the output of voltage comparator U1 is exported again high level, the drain electrode of metal-oxide-semiconductor Q1 and source electrode conducting, current signal flow into sampling resistor R3 again, change into voltage, and with the forward input voltage comparison of U1, owing to being overcurrent signal, the voltage transforming on sampling resistor R3 is greater than the forward input voltage of voltage comparator U1, moment has been exported low level, the source electrode of metal-oxide-semiconductor Q1 and drain electrode disconnect, so repeatedly, voltage on final assurance R3 is less than or equal to the forward input voltage of U1, be R1, voltage after R2 dividing potential drop.
In the time there is overvoltage signal input, the operation principle when operation principle of the protective circuit that the utility model is described and current signal input is similar, when overvoltage signal is instant high-voltage signal, while grade as thunderbolt, TVS pipe D1, by transient switching, releases GND above by voltage, protection late-class circuit, in the time that overvoltage signal is stable high voltage signal, pass through C1, the filter rectification processing of D2, on Zhongdao sampling resistor R3, and with the forward input voltage comparison of voltage comparator U1, in the time that the voltage on sampling resistor R3 is greater than the forward input voltage of U1, the output of voltage comparator U1 is output as low level immediately, between the source electrode of metal-oxide-semiconductor Q1 and drain electrode, disconnect, be that input circuit disconnects, voltage on sampling resistor R3 and then becomes 0V, be less than the anodal input voltage of U1, so the output of U1 is exported again high level, metal-oxide-semiconductor Q1 conducting, voltage signal is transformed on R3, and with the forward input voltage comparison of U1, owing to being overvoltage signal, be greater than the forward input voltage of U1, moment is output as low level, the source electrode of metal-oxide-semiconductor Q1 and drain electrode disconnect, so repeatedly, voltage on final assurance sampling resistor R3 is less than or equal to the forward input voltage of U1, be R1, voltage after R2 dividing potential drop.
In sum, the overcurrent excess voltage protection for 4-20mA current input circuit that the utility model provides, realizes overcurrent, superpotential defencive function by filter rectification module, voltage acquisition module, switch control module and signal monitoring module; This protective circuit is little on input signal impact, current input signal is gathered to worst error and be less than 1uA; Signal input impedance is low, lower to the requirement of signal source; Fast response time, when overcurrent overvoltage signal appears in input signal, moment thoroughly disconnects input circuit, makes overcurrent overvoltage signal and protected isolation of system, effectively protects late-class circuit, and reliability is high; Can effectively prevent that the interference signals such as thunderbolt or transient overvoltage pulse are input to late-class circuit simultaneously.
Although the utility model discloses as above with preferred embodiment; so it is not in order to limit the utility model; any those skilled in the art; not departing from spirit and scope of the present utility model; when doing a little modification and perfect, therefore protection range of the present utility model is worked as with being as the criterion that claims were defined.

Claims (4)

1. for an overcurrent excess voltage protection for 4-20mA current input circuit, it is characterized in that, comprising:
Filter rectification module: the instantaneous overvoltage pulse signal in filtering input signal, and anti-stop signal reversal connection;
Switch control module: receive the current signal of described filter rectification module output and control the break-make of this current circuit;
Voltage acquisition module: will change into corresponding voltage signal from the current signal of switch control module; And
Signal monitoring module: monitor the voltage signal that collects of voltage acquisition module, and with predetermined voltage threshold comparison, if exceed predetermined voltage threshold, control immediately described switch control module turn-off current loop.
2. the overcurrent excess voltage protection for 4-20mA current input circuit as claimed in claim 1; it is characterized in that; described filter rectification module comprises two-way TVS pipe D1, filter capacitor C1 and anti-reverse diode D2, is connected to the positive pole of anti-reverse diode D2 after described two-way TVS pipe D1 is in parallel with filter capacitor C1.
3. the overcurrent excess voltage protection for 4-20mA current input circuit as claimed in claim 2, it is characterized in that, described switch control module is metal-oxide-semiconductor Q1, described voltage acquisition module is sampling resistor R3, and described signal monitoring module comprises voltage comparator U1, divider resistance R1 and divider resistance R2; The drain electrode of described metal-oxide-semiconductor Q1 is connected to the negative pole of anti-reverse diode D2, the grid of described metal-oxide-semiconductor Q1 is connected to the output of voltage comparator U1, the source electrode of described metal-oxide-semiconductor Q1 is connected to sampling resistor R3, be connected to the reverse input end of voltage comparator U1 simultaneously, the positive input of described voltage comparator U1 is connected to one end of electric resistance partial pressure resistance R 1 and divider resistance R2 simultaneously, the other end of described divider resistance R1 is connected to power end V_Set, and the other end of described divider resistance R2 is connected to earth terminal GND.
4. the overcurrent excess voltage protection for 4-20mA current input circuit as claimed in claim 3, is characterized in that, described metal-oxide-semiconductor Q1 is N channel enhancement metal-oxide-semiconductor.
CN201320800450.XU 2013-12-06 2013-12-06 Over-current and overvoltage protective circuit used for 4-20mA current input circuit Withdrawn - After Issue CN203607820U (en)

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Application Number Priority Date Filing Date Title
CN201320800450.XU CN203607820U (en) 2013-12-06 2013-12-06 Over-current and overvoltage protective circuit used for 4-20mA current input circuit

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103618285A (en) * 2013-12-06 2014-03-05 悉雅特万科思自动化(杭州)有限公司 Over-current over-voltage protection circuit for 4-20mA current input circuit
CN109030913A (en) * 2018-08-27 2018-12-18 沃尔特电子(苏州)有限公司 A kind of current detection means
CN112684359A (en) * 2020-12-03 2021-04-20 上汽通用汽车有限公司 Voltage pulse isolation protection device and battery test bench comprising same

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103618285A (en) * 2013-12-06 2014-03-05 悉雅特万科思自动化(杭州)有限公司 Over-current over-voltage protection circuit for 4-20mA current input circuit
CN103618285B (en) * 2013-12-06 2015-12-23 万科思自控信息(中国)有限公司 A kind of overcurrent excess voltage protection for 4-20mA current input circuit
CN109030913A (en) * 2018-08-27 2018-12-18 沃尔特电子(苏州)有限公司 A kind of current detection means
CN112684359A (en) * 2020-12-03 2021-04-20 上汽通用汽车有限公司 Voltage pulse isolation protection device and battery test bench comprising same
CN112684359B (en) * 2020-12-03 2024-04-02 上汽通用汽车有限公司 Voltage pulse isolation protection device and battery test bed comprising same

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Owner name: MOX AUTOMATIC CONTROL INFORMATION (CHINA) CO., LTD

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Effective date: 20140919

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Address after: Jiaxing City, Zhejiang province 314000 Nanhu District Ling Gong Tang Road No. 3339 (Jiaxing city) building A room 407

Patentee after: Automation information (China) Co., Ltd.

Address before: 2, No. 398, building 18, No. 310023, Tianmu Road, Hangzhou, Zhejiang

Patentee before: Xiate Woncos Automation (Hangzhou) Co., Ltd.

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Address after: Jiaxing City, Zhejiang province 314000 Qunxian Road No. 130

Patentee after: Automation information (China) Co., Ltd.

Address before: Jiaxing City, Zhejiang province 314000 Nanhu District Ling Gong Tang Road No. 3339 (Jiaxing city) building A room 407

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Denomination of utility model: Over-current over-voltage protection circuit for 4-20mA current input circuit

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C25 Abandonment of patent right or utility model to avoid double patenting