CN105045673A - Watchdog circuit suitable for safety output - Google Patents
Watchdog circuit suitable for safety output Download PDFInfo
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- CN105045673A CN105045673A CN201510504225.5A CN201510504225A CN105045673A CN 105045673 A CN105045673 A CN 105045673A CN 201510504225 A CN201510504225 A CN 201510504225A CN 105045673 A CN105045673 A CN 105045673A
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Abstract
The present invention discloses a watchdog circuit suitable for safety output. A feeding-dog signal is input to the watchdog circuit by a processing unit, the watchdog circuit outputs a safety signal to a relay, and the watchdog circuit comprises a window detection unit, a driving unit and a signal conversion unit. The watchdog circuit disclosed by the present invention not only has a time window detection function, but also has the ability that a single device fault cannot cause the circuit to be at the dangerous side, and is suitable for a safety power supply, a safety switch and the like to use a signal driven by a relay output.
Description
Technical field
The present invention relates to watchdog circuit.
Background technology
Have in the control system of safety integrity requirement in track traffic, aviation electronics etc., the safety circuit (as: safety power supply) of system needs to possess fault-safety principle function, and realizing fault-safety principle function needs to use watchdog circuit.
Watchdog circuit is by processing unit behaviors such as monitoring processor units, and when processing unit runs according to predetermined performing an action, watchdog circuit exports and allows run signal, as: relay adhesive, power supply exports; When watchdog circuit monitors processing unit not by predetermined state, house dog output circuit output safety signal, as: relay disconnects, power-off.
From sensing range, most watchdog circuit only detects the lower limit of feeding the dog cycle, just can detect when namely only having the feeding-dog signal cycle to be greater than setting cycle, and processing unit fault causes feeding the dog cycle and too frequently then cannot detect.And have the system of safety integrity requirement often namely to monitor the lower limit of feeding the dog cycle, also need to monitor the upper limit of feeding the dog cycle, namely need the watchdog circuit using " possessing time window measuring ability ".
The existing watchdog circuit conventional approach possessing time window measuring ability is, use existing possess time window measuring ability watchdog chip or use the Programmable Logic Device such as PLD to build realization, then drive relay to monitor with transistor or driving chip.This implementation method cannot solve the self-adhesion of house dog output signal and to lose efficacy or the transistor nonfunctional exported makes house dog cannot output safety signal, finally causes output state in the hole.
Summary of the invention
Technical matters to be solved by this invention is just to provide a kind of watchdog circuit being applicable to Safety output, has the function of the faults itself failure to the safe side of watchdog circuit and driving circuit.
For solving the problems of the technologies described above, the present invention adopts following technical scheme: a kind of watchdog circuit being applicable to Safety output, feeding-dog signal is inputted to watchdog circuit by processing unit, watchdog circuit is to relay output safety signal, and this watchdog circuit comprises windows detecting unit, driver element, signal conversion unit;
The frequency range of described windows detecting unit to feeding-dog signal detects, if the feeding-dog signal frequency detected meets setting requirement, then continues conveying feeding-dog signal, if the feeding-dog signal frequency anomaly detected, then cuts off feeding-dog signal transmission;
Described driver element does not change the square wave feeding-dog signal frequency that processing unit exports, and converts the rated voltage of relay to;
Described signal conversion unit converts square wave feeding-dog signal to burning voltage signal, and this voltage signal is contrary with the voltage of driver element, for the Direct driver actuating of relay.
Preferably, described windows detecting unit comprises high-frequency detection module, low frequency detection module, gauge tap, described high-frequency detection module is used for detecting the feeding-dog signal that frequency is too high, and described low frequency detection module is used for detecting the feeding-dog signal of underfrequency; If the feeding-dog signal frequency that high-frequency detection module and low frequency detection module detect all meets the requirements, described gauge tap closes, if the feeding-dog signal frequency anomaly that high-frequency detection module and low frequency detection module detect, described gauge tap disconnects.
Preferably, described driver element comprises level shifting circuit, and described level shifting circuit converts the input signal of watchdog circuit the rated voltage of relay to.
Preferably, described driver element also comprises driving intensifier circuit, and the output current of described driving intensifier circuit to watchdog circuit strengthens, and enables the output current Direct driver relay of watchdog circuit.
Preferably, described driving intensifier circuit is the totem pole be made up of triode Q6, triode Q8.
Preferably, described driver element is also provided with resistance R9, resistance R10, and described resistance R9 is connected to the base stage of triode Q8, and described resistance R10 is connected to the base stage of triode Q6.
Preferably, described signal conversion unit comprises electric capacity C3, electric capacity C4, diode D4, diode D5, diode D6 and exports S2, electric capacity C3 one end is connected with driver element output terminal, the electric capacity C3 other end is connected with the positive pole of diode D5, the negative pole of diode D4, the negative pole of diode D5 is connected with GND, and the positive pole of diode D4 is connected with output S2, and electric capacity C4 is connected with output S2 and GND, the positive pole of diode D6 is connected with output S2, and the negative pole of diode D6 is connected with GND.
Watchdog circuit of the present invention not only possesses time window measuring ability, also possesses single device fault and circuit can not be caused to be in the ability of hazardous side, is applicable to safety power supply, safety switch etc. and uses relay to export the signal driven.
Accompanying drawing explanation
Below in conjunction with the drawings and specific embodiments, the invention will be further described:
Fig. 1 is circuit theory diagrams of the present invention.
Embodiment
As shown in Figure 1, a kind of watchdog circuit being applicable to Safety output, this watchdog circuit is primarily of windows detecting unit, driver element, signal conversion unit composition, and this watchdog circuit is input as the feeding-dog signal of processing unit, exports the voltage signal into Direct driver relay.
Wherein, the frequency range of windows detecting unit to feeding-dog signal detects, if the feeding-dog signal frequency detected meets setting requirement, then continues conveying feeding-dog signal, if the feeding-dog signal frequency anomaly detected, then cuts off feeding-dog signal transmission; Driver element does not change the square wave feeding-dog signal frequency that processing unit exports, and converts the rated voltage of relay to; Signal conversion unit converts square wave feeding-dog signal to burning voltage signal, and this voltage signal is contrary with the voltage of driver element, for the Direct driver actuating of relay.
Below windows detecting unit, driver element, signal conversion unit are made and being illustrated.
Windows detecting unit comprises high-frequency detection module, low frequency detection module, gauge tap K, gauge tap K is controlled by high-frequency detection module, low frequency detection module, described high-frequency detection module is used for detecting the feeding-dog signal that frequency is too high, and described low frequency detection module is used for detecting the feeding-dog signal of underfrequency; If the feeding-dog signal frequency that high-frequency detection module and low frequency detection module detect all meets the requirements, described gauge tap K closes, and now feeding-dog signal can export toward rear stage according to original frequency, amplitude; If the feeding-dog signal frequency anomaly that high-frequency detection module and low frequency detection module detect, described gauge tap K disconnects, and now feeding-dog signal can not output to driver element, and driver element does not obtain feeding-dog signal, safety relay disconnects the most at last, system failure to the safe side.
The circuit realiration of windows detecting cell mesh by realizing based on the trigger circuit of trigger composition, also can pass through programming realization by programmable units such as PLD.
Driver element comprises level shifting circuit, drives intensifier circuit, and wherein the input signal of watchdog circuit is converted to the rated voltage of relay by level shifting circuit.Drive the output current of intensifier circuit to watchdog circuit to strengthen, enable the output current Direct driver relay of watchdog circuit, and do not need through amplifying circuit.Intensifier circuit is driven to be the totem pole be made up of triode Q6, triode Q8 in the present embodiment.In addition, driver element is also provided with resistance R9, resistance R10, and resistance R9 is connected to the base stage of triode Q8, and resistance R10 is connected to the base stage of triode Q6, and resistance R9, resistance R10 are used for playing metering function.
The circuit of driver element realizes by modes such as transistor, integrated driving IC.As the application of example, use 12V to need the relay of 30mA electric current, then feeding-dog signal converts to by drives partial circuit, has the square-wave signal of the 12V voltage of 50mA driving force, and dutycycle, the frequency of output are consistent with input.
Signal conversion unit converts Dynamic Signal to stationary singnal, physical circuit comprises electric capacity C3, electric capacity C4, diode D4, diode D5, diode D6 and exports S2, electric capacity C3 one end is connected with driver element output terminal, the electric capacity C3 other end is connected with the positive pole of diode D5, the negative pole of diode D4, the negative pole of diode D5 is connected with GND, the positive pole of diode D4 is connected with output S2, electric capacity C4 is connected with output S2 and GND, the positive pole of diode D6 is connected with output S2, and the negative pole of diode D6 is connected with GND.
The electric capacity C3 of foregoing circuit, diode D5, diode D4, electric capacity C4, diode D6 realize converting the square-wave signal of certain dutycycle to stable voltage signal jointly, and this voltage signal is contrary with the voltage of drive part, for Direct driver relay, the high level exporting S1 output as driver element is the square-wave signal of 12V, then export the stable voltage signal that S2 is-12V.Stable-12V the voltage exported can the Direct driver actuating of relay, and the single hardware random failure of this partial circuit can not cause the output of circuit to enter hazardous side.
Signal conversion unit principle of work is as follows: when S1 point is high level, because triode Q6 produces the high level signal having larger driving force, now 12V power supply is charged to electric capacity C3 by triode Q6, diode D5; When S1 point exports as low level, because triode Q8 produces the low level signal having larger driving force, the electric charge of electric capacity C3 is discharged by triode Q8, diode D4, electric capacity C4, charge transfer is charged to electric capacity C4 simultaneously, now the voltage of electric capacity C4 is about the half of supply voltage, constantly circulate through multiple cycle, finally reach the voltage of electric capacity C4 close to supply voltage, can the action of Direct driver output relay.As long as the existence of S1 point and dutycycle are normal, then electric capacity C4 will be continuously charged, and electric capacity C4 direct relay R elay1 in parallel will adhesive always, and safety power supply exports by the relay of adhesive.
If processing unit do not feed dog or fault cause the signal of S1 be normal high time, open-circuit condition is equivalent to after electric capacity C3 electric charge is full of, now electric capacity C4 cannot be charged by diode D4, the electric charge at electric capacity C4 two ends is discharged by relay R elay1, electric capacity C4 voltage is caused constantly to reduce, finally cause relay R elay1 to disconnect, safety power supply does not export; When S1 signal is often low, electric capacity C3 is by being equivalent to open-circuit condition after the electric charge release of triode Q8, electric capacity C4, diode D4, electric capacity C4 can not continue charging, the electric charge at electric capacity C4 two ends is discharged by relay R elay1, electric capacity C4 voltage is caused constantly to reduce, finally cause relay R elay1 to disconnect, safety power supply does not export.
And circuit self can realize " fault-safety principle " function, concrete principle is as follows:
If Dynamic Signal turns Static output part electric capacity C3, diode D5, diode D4, diode D6 open failure or electric capacity C3, diode D5, electric capacity C4, diode D6 short-circuit failure, because electric capacity C4 can not be charged, then relay can not adhesive, and relay exports in a safe condition;
If diode D4 short-circuit failure, then because diode D6 exists, electric capacity C4 cannot be charged, then relay can not adhesive, and relay exports in a safe condition;
If Dynamic Signal turns Static output part electric capacity C4 open failure, then exporting S2 is the half that half the time has driving voltage, and therefore relay also can not by adhesive, and relay exports in a safe condition;
If driver element adhesion is normal high, normal low, open circuit, then S1 can be caused to be Chang Gao or normal low signal, be equivalent to and do not have feeding-dog signal, then relay can not adhesive, and relay exports in a safe condition.
Windows detecting unit and gauge tap K become normal effective status, then " the windows detecting function " of circuit lost efficacy, and house dog degenerates, if now processing unit fault causes feeding-dog signal to export, and relay also not adhesive, system is in a safe condition; Only cause feeding too fast or less the feeding when dog Frequency downshift exceeds time window of variable quantity of dog frequency and can not detect processing unit is abnormal.This fault is lower inside all defective proportion, can detect by starting the modes such as self-inspection.
To sum up can draw, the present invention possesses following characteristics: circuit topology is simple, and circuit malfunction rate is low, cost is low; In circuit, any one component failure all can not cause relay to be continued adhesive, and circuit possesses " fault-safety principle " function of device level.
Claims (7)
1. one kind is applicable to the watchdog circuit of Safety output, feeding-dog signal is inputted to watchdog circuit by processing unit, watchdog circuit, to relay output safety signal, is characterized in that: this watchdog circuit comprises windows detecting unit, driver element, signal conversion unit;
The frequency range of described windows detecting unit to feeding-dog signal detects, if the feeding-dog signal frequency detected meets setting requirement, then continues conveying feeding-dog signal, if the feeding-dog signal frequency anomaly detected, then cuts off feeding-dog signal transmission;
Described driver element does not change the square wave feeding-dog signal frequency that processing unit exports, and converts the rated voltage of relay to;
Described signal conversion unit converts square wave feeding-dog signal to burning voltage signal, and this voltage signal is contrary with the voltage of driver element, for the Direct driver actuating of relay.
2. a kind of watchdog circuit being applicable to Safety output according to claim 1, it is characterized in that: described windows detecting unit comprises high-frequency detection module, low frequency detection module, gauge tap, described high-frequency detection module is used for detecting the feeding-dog signal that frequency is too high, and described low frequency detection module is used for detecting the feeding-dog signal of underfrequency; If the feeding-dog signal frequency that high-frequency detection module and low frequency detection module detect all meets the requirements, described gauge tap closes, if the feeding-dog signal frequency anomaly that high-frequency detection module and low frequency detection module detect, described gauge tap disconnects.
3. a kind of watchdog circuit being applicable to Safety output according to claim 1, it is characterized in that: described driver element comprises level shifting circuit, described level shifting circuit converts the input signal of watchdog circuit the rated voltage of relay to.
4. a kind of watchdog circuit being applicable to Safety output according to claim 3, it is characterized in that: described driver element also comprises driving intensifier circuit, the output current of described driving intensifier circuit to watchdog circuit strengthens, and enables the output current Direct driver relay of watchdog circuit.
5. a kind of watchdog circuit being applicable to Safety output according to claim 4, is characterized in that: described driving intensifier circuit is the totem pole be made up of triode Q6, triode Q8.
6. a kind of watchdog circuit being applicable to Safety output according to claim 5, it is characterized in that: described driver element is also provided with resistance R9, resistance R10, described resistance R9 is connected to the base stage of triode Q8, and described resistance R10 is connected to the base stage of triode Q6.
7. a kind of watchdog circuit being applicable to Safety output according to claim 1 to 6 any one, it is characterized in that: described signal conversion unit comprises electric capacity C3, electric capacity C4, diode D4, diode D5, diode D6 and output S2, electric capacity C3 one end is connected with driver element output terminal, the positive pole of the electric capacity C3 other end and diode D5, the negative pole of diode D4 is connected, the negative pole of diode D5 is connected with GND, the positive pole of diode D4 is connected with output S2, electric capacity C4 is connected with output S2 and GND, the positive pole of diode D6 is connected with output S2, the negative pole of diode D6 is connected with GND.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510504225.5A CN105045673A (en) | 2015-08-17 | 2015-08-17 | Watchdog circuit suitable for safety output |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510504225.5A CN105045673A (en) | 2015-08-17 | 2015-08-17 | Watchdog circuit suitable for safety output |
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| CN105045673A true CN105045673A (en) | 2015-11-11 |
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| CN201510504225.5A Pending CN105045673A (en) | 2015-08-17 | 2015-08-17 | Watchdog circuit suitable for safety output |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106292434A (en) * | 2016-08-19 | 2017-01-04 | 东风汽车公司 | A kind of watchdog circuit for automobile electronic controller |
| CN118193278A (en) * | 2024-05-17 | 2024-06-14 | 浙江正泰中自控制工程有限公司 | Watchdog diagnosis system and method with flexibly-configurable time window |
Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01149148A (en) * | 1987-12-07 | 1989-06-12 | Oki Electric Ind Co Ltd | Relay driving circuit with watch dog timer |
| CN202009136U (en) * | 2011-01-27 | 2011-10-12 | 陈清尧 | Power conversion plug extension |
| CN202042870U (en) * | 2011-04-01 | 2011-11-16 | 广州珠江电信设备制造有限公司 | Improved monitoring and alarming device for communication power supply system |
| CN104331340A (en) * | 2014-11-20 | 2015-02-04 | 苏州富欣智能交通控制有限公司 | Watchdog circuit |
| CN104750568A (en) * | 2015-04-14 | 2015-07-01 | 广州市智博光辉电气科技有限公司 | Abnormal forced resetting type watchdog circuit of microcontroller |
| CN204945993U (en) * | 2015-08-17 | 2016-01-06 | 浙江众合科技股份有限公司 | A kind of watchdog circuit being applicable to Safety output |
-
2015
- 2015-08-17 CN CN201510504225.5A patent/CN105045673A/en active Pending
Patent Citations (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPH01149148A (en) * | 1987-12-07 | 1989-06-12 | Oki Electric Ind Co Ltd | Relay driving circuit with watch dog timer |
| CN202009136U (en) * | 2011-01-27 | 2011-10-12 | 陈清尧 | Power conversion plug extension |
| CN202042870U (en) * | 2011-04-01 | 2011-11-16 | 广州珠江电信设备制造有限公司 | Improved monitoring and alarming device for communication power supply system |
| CN104331340A (en) * | 2014-11-20 | 2015-02-04 | 苏州富欣智能交通控制有限公司 | Watchdog circuit |
| CN104750568A (en) * | 2015-04-14 | 2015-07-01 | 广州市智博光辉电气科技有限公司 | Abnormal forced resetting type watchdog circuit of microcontroller |
| CN204945993U (en) * | 2015-08-17 | 2016-01-06 | 浙江众合科技股份有限公司 | A kind of watchdog circuit being applicable to Safety output |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106292434A (en) * | 2016-08-19 | 2017-01-04 | 东风汽车公司 | A kind of watchdog circuit for automobile electronic controller |
| CN106292434B (en) * | 2016-08-19 | 2019-03-08 | 东风汽车公司 | A kind of watchdog circuit for automobile electronic controller |
| CN118193278A (en) * | 2024-05-17 | 2024-06-14 | 浙江正泰中自控制工程有限公司 | Watchdog diagnosis system and method with flexibly-configurable time window |
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