CN105048428A - Protective circuit for analog input ports - Google Patents
Protective circuit for analog input ports Download PDFInfo
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- CN105048428A CN105048428A CN201510369632.XA CN201510369632A CN105048428A CN 105048428 A CN105048428 A CN 105048428A CN 201510369632 A CN201510369632 A CN 201510369632A CN 105048428 A CN105048428 A CN 105048428A
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- signal source
- gas discharge
- discharge tube
- analog input
- protection circuit
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Abstract
The invention discloses a protective circuit for analog input ports. The protective circuit is characterized in that one end of a first gas discharge tube GDT1 is grounded, and the other end of the first gas discharge tube GDT1 is connected with the positive end of a direct-current signal source; one end of a second gas discharge tube GDT2 is grounded, and the other end of the second gas discharge tube GDT2 is connected with the negative end of the direct-current signal source; the positive end of the direct-current signal source is connected with one end of a transient voltage suppressor TVS through a magnetic bead L1, and the negative end of the direct-current signal source is connected with the other end of the transient voltage suppressor TVS through a magnetic bead L2; and a voltage dependent resistor RV is connected in parallel between the positive end of the direct-current signal source and the negative end of the direct-current signal source. The gas discharge tubes are adopted to replace original safety capacitors. Effective EMC protection can be offered to multiple analog input ports. Due to small leakage current, multiple parallel analog input ports are enabled to meet the strength requirement of an insulating medium on the premise of passing quick transient interference test and surge immunity test.
Description
Technical field
The invention belongs to Relay Protection Technology in Power System field, particularly relate to a kind of protection circuit of analog input port.
Background technology
At present, field of relay protection in power, when multiple analog input port parallel connection of protective device, the following main experimental of demand fulfillment requires: (1) fast transient interference test (GB17626.4,1998), IV level; (2) surge immunity test (GB17626.5,1999), IV level;
In above-mentioned test, the interference signal of (1) belongs to high frequency, low-yield interference signal; And the interference signal of (2) belongs to low frequency, high-octane interference signal.General analog input port-guard circuit design, in port respectively over the ground and connect two Y safety electric capacity.These two safety electric capacity have drainage function for the interference signal of experiment (1) and (2), thus by test.
From the security consideration of relay protection of power system, frequency is 50Hz or 60Hz, amplitude is 0.5kV (nominal insulation voltage≤63V), last the power frequency withstand test of 1min to require analog input port to bear ground energy., should not there is insulation breakdown and flashover in duration of test.But when multi-analog input port is connected in parallel, because safety electric capacity has larger leakage current, parallel port number is more, and leakage current is larger, and along with voltage rising, leakage current also increases gradually, finally cannot meet the requirement of dielectric strength.
Visible, the analog input port-guard circuit design used at present, although the test requirements document of (1) and (2) can be met, when two-way and more parallel, cannot by the power frequency withstand test in dielectric strength test.
Summary of the invention
In order to solve in prior art when multi-analog input port is connected in parallel, in order to meet quick wink interference test, surge immunity test and the protective device that adds is in parallel, leakage current is caused to increase, and along with voltage raises, leakage current increases gradually, dielectric requirement of strength cannot be met, not by the problem of dielectric intensity detection, the invention provides and a kind ofly make device in multi-channel parallel situation still by the protection circuit of the analog input port of the power frequency withstand test in dielectric strength test.
In order to solve the problem, the technical solution used in the present invention is:
A kind of protection circuit of analog input port, comprise one-level protection circuit, two stages of circuit and magnetic bead L1 and magnetic bead L2, it is characterized in that: described one-level protection circuit comprises the first gas discharge tube GDT1, a second gas discharge tube GDT2 and piezo-resistance RV, described two stages of circuit comprises transition diode TVS, described first gas discharge tube GDT1 one end ground connection, the first gas discharge tube GDT1 other end is connected with DC signal source positive terminal, described second gas discharge tube GDT2 one end ground connection, the second gas discharge tube GDT2 other end is connected with DC signal source negative pole end, described DC signal source positive terminal is connected with transition diode TVS one end by magnetic bead L1, described DC signal source negative pole end is connected with the transition diode TVS other end by magnetic bead L2, piezo-resistance RV is parallel with between described DC signal source positive terminal and DC signal source negative pole end.
The protection circuit of aforesaid a kind of analog input port, is characterized in that: described DC signal source positive terminal and DC signal source negative pole end access 0 ~ 5V voltage or 4 ~ 20mA electric current.
The protection circuit of aforesaid a kind of analog input port, is characterized in that: when DC signal source positive terminal and DC signal source negative pole end access 4 ~ 20mA electric current, be parallel with resistance R at transition diode TVS two ends.
The protection circuit of aforesaid a kind of analog input port, is characterized in that: described gas discharge tube adopts 2RH2000L-8 gas discharge tube, and the DC breakdown voltage of described gas discharge tube adopts 2KV.
The protection circuit of aforesaid a kind of analog input port, is characterized in that: described piezo-resistance RV adopts 7D471K piezo-resistance, and the pressure sensitive voltage of described piezo-resistance is chosen as 470V.
The protection circuit of aforesaid a kind of analog input port, is characterized in that: described magnetic bead adopts RH359008 magnetic bead.
The protection circuit of aforesaid a kind of analog input port, is characterized in that: described transition diode TVS adopts SMBJ15CA transition diode.
The beneficial effect that the present invention reaches: in power system relay protection device; the present invention adopts gas discharge tube to substitute original safety electric capacity; can carry out effective EMC protection to multi-analog input port, the characteristic utilizing leakage current little can make the analog input port of multi-channel parallel while being tested by fast transient interference test and surge immunity, still meet the requirement of dielectric intensity.
Accompanying drawing explanation
Fig. 1 is the circuit theory diagrams of the protection circuit of analog input port of the present invention.
Embodiment
Below in conjunction with accompanying drawing, the invention will be further described.Following examples only for technical scheme of the present invention is clearly described, and can not limit the scope of the invention with this.
As shown in Figure 1, a kind of protection circuit of analog input port, comprise one-level protection circuit, two stages of circuit and magnetic bead L1 and magnetic bead L2, it is characterized in that: described one-level protection circuit comprises the first gas discharge tube GDT1, a second gas discharge tube GDT2 and piezo-resistance RV, described two stages of circuit comprises transition diode TVS, described first gas discharge tube GDT1 one end ground connection, the first gas discharge tube GDT1 other end is connected with DC signal source positive terminal, described second gas discharge tube GDT2 one end ground connection, the second gas discharge tube GDT2 other end is connected with DC signal source negative pole end, described DC signal source positive terminal is connected with transition diode TVS one end by magnetic bead L1, described DC signal source negative pole end is connected with the transition diode TVS other end by magnetic bead L2, piezo-resistance RV is parallel with between described DC signal source positive terminal and DC signal source negative pole end.
DC signal source positive terminal of the present invention and DC signal source negative pole end access 0 ~ 5V voltage or 4 ~ 20mA electric current.When DC signal source positive terminal and DC signal source negative pole end access 4 ~ 20mA electric current, be parallel with resistance R at transition diode TVS two ends.When DC signal source positive terminal and DC signal source negative pole end access 0 ~ 5V voltage, this resistance R does not weld.
Described gas discharge tube adopts 2RH2000L-8 gas discharge tube, and the DC breakdown voltage of described gas discharge tube adopts 2KV.Described piezo-resistance RV adopts 7D471K piezo-resistance, and the pressure sensitive voltage of described piezo-resistance is chosen as 470V.Described magnetic bead adopts RH359008 magnetic bead.Described transition diode TVS adopts SMBJ15CA transition diode.
The protection circuit of analog input port of the present invention is when carrying out fast transient interference test and surge immunity test, after interference signal is added to analog input port, safe secondary protection circuit is action first, interference signal voltage clamp to lower than back-end circuit normal operating level, along with the enhancing of interference signal, the voltage be added on cascade magnetic bead L and transition diode TVS progressively raises, the transient current of being released by gas discharge tube GDT is increasing, when the operation voltage of this voltage higher than gas discharge tube GDT, first class of protection circuit operation, interference signal is released greatly by gas discharge tube GDT rapidly, thus the protection realized late-class circuit.
When dielectric strength test, the testing standard of this module is 500V/20 milliampere/1 minute.500V power-frequency voltage is added on analog port, is unlikely to make gas discharge tube GDT action, and the leakage current (leakage current of GDT) that even 5 roads or multichannel analog signals port stack up is generally less than 10mA.
The requirement of dielectric strength test of the present invention:
1), under the standard atmospheric conditions of test, it is 50Hz that equipment should be able to bear frequency, lasts the power frequency withstand test of 1min and nothing punctures flashover and component damage phenomenon.
2), test voltage is power-frequency voltage effective value is 0.5kV (nominal insulation voltage≤63V).
3), in process of the test, its cocircuit equipotential interconnected ground connection when arbitrary tested loop applies voltage.
In actual power frequency withstand test, by after all signal input part parallel connections, 0.5KV voltage is applied to the earth, require that in 1min, leakage current is less than 20mA.
In test, when applying 0.5KV voltage to the earth after two signal input part parallel connections, leakage current is about 1uA to the protection circuit of analog input port of the present invention, far above test requirements document.In actual test, in single device after upper 5 modules in parallel, still by dielectric strength test.But safety capacitive scheme individual module leakage current is about 5 ~ 10mA, in single device after 2 modules in parallel, namely likely dielectric strength test cannot be passed through.
More than show and describe general principle of the present invention, principal character and advantage.The technical staff of the industry should understand; the present invention is not restricted to the described embodiments; what describe in above-described embodiment and specification just illustrates principle of the present invention; without departing from the spirit and scope of the present invention; the present invention also has various changes and modifications, and these changes and improvements all fall in the claimed scope of the invention.Application claims protection range is defined by appending claims and equivalent thereof.
Claims (7)
1. the protection circuit of an analog input port, comprise one-level protection circuit, two stages of circuit and magnetic bead L1 and magnetic bead L2, it is characterized in that: described one-level protection circuit comprises the first gas discharge tube GDT1, a second gas discharge tube GDT2 and piezo-resistance RV, described two stages of circuit comprises transition diode TVS, described first gas discharge tube GDT1 one end ground connection, the first gas discharge tube GDT1 other end is connected with DC signal source positive terminal, described second gas discharge tube GDT2 one end ground connection, the second gas discharge tube GDT2 other end is connected with DC signal source negative pole end, described DC signal source positive terminal is connected with transition diode TVS one end by magnetic bead L1, described DC signal source negative pole end is connected with the transition diode TVS other end by magnetic bead L2, piezo-resistance RV is parallel with between described DC signal source positive terminal and DC signal source negative pole end.
2. the protection circuit of a kind of analog input port according to claim 1, is characterized in that: described DC signal source positive terminal and DC signal source negative pole end access 0 ~ 5V voltage or 4 ~ 20mA electric current.
3. the protection circuit of a kind of analog input port according to claim 2, is characterized in that: when DC signal source positive terminal and DC signal source negative pole end access 4 ~ 20mA electric current, be parallel with resistance R at transition diode TVS two ends.
4. the protection circuit of a kind of analog input port according to claim 3, is characterized in that: described gas discharge tube adopts 2RH2000L-8 gas discharge tube, and the DC breakdown voltage of described gas discharge tube adopts 2KV.
5. the protection circuit of a kind of analog input port according to claim 4, is characterized in that: described piezo-resistance RV adopts 7D471K piezo-resistance, and the pressure sensitive voltage of described piezo-resistance is chosen as 470V.
6. the protection circuit of a kind of analog input port according to claim 5, is characterized in that: described magnetic bead adopts RH359008 magnetic bead.
7. the protection circuit of a kind of analog input port according to claim 6, is characterized in that: described transition diode TVS adopts SMBJ15CA transition diode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201510369632.XA CN105048428A (en) | 2015-06-29 | 2015-06-29 | Protective circuit for analog input ports |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201510369632.XA CN105048428A (en) | 2015-06-29 | 2015-06-29 | Protective circuit for analog input ports |
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| CN105048428A true CN105048428A (en) | 2015-11-11 |
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| CN201510369632.XA Pending CN105048428A (en) | 2015-06-29 | 2015-06-29 | Protective circuit for analog input ports |
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Cited By (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105319002A (en) * | 2015-11-27 | 2016-02-10 | 上海立格仪表有限公司 | Natural ventilation pressure measuring instrument |
| CN105826910A (en) * | 2016-04-25 | 2016-08-03 | 北京先研科技有限责任公司 | Financial automatic teller machine (ATM) power source and special lightning protection device for communication system |
| CN106093494A (en) * | 2016-08-22 | 2016-11-09 | 四方继保（武汉）软件有限公司 | A kind of signal for electronic mutual inductor protects filter circuit |
| CN110120662A (en) * | 2019-04-28 | 2019-08-13 | 努比亚技术有限公司 | Circuit protection circuit |
| CN114201942A (en) * | 2022-02-18 | 2022-03-18 | 深圳佑驾创新科技有限公司 | Automatic checking method for capacitance parameter in circuit schematic diagram |
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| CN201674223U (en) * | 2010-06-08 | 2010-12-15 | 杭州华三通信技术有限公司 | Interface protective circuit and interface circuit capable of realizing overvoltage protection |
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| CN204794059U (en) * | 2015-06-29 | 2015-11-18 | 国电南京自动化股份有限公司 | Protection circuit of analog input port |
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2015
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Patent Citations (4)
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| CN201674223U (en) * | 2010-06-08 | 2010-12-15 | 杭州华三通信技术有限公司 | Interface protective circuit and interface circuit capable of realizing overvoltage protection |
| CN202034777U (en) * | 2011-05-12 | 2011-11-09 | 昂纳信息技术（深圳）有限公司 | ESD (electrostatic discharge) protective circuit used for capacitive load |
| KR101391823B1 (en) * | 2014-02-07 | 2014-05-07 | 선광엘티아이(주) | Automatically transfer switching overvoltage protection apparatus |
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Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105319002A (en) * | 2015-11-27 | 2016-02-10 | 上海立格仪表有限公司 | Natural ventilation pressure measuring instrument |
| CN105826910A (en) * | 2016-04-25 | 2016-08-03 | 北京先研科技有限责任公司 | Financial automatic teller machine (ATM) power source and special lightning protection device for communication system |
| CN106093494A (en) * | 2016-08-22 | 2016-11-09 | 四方继保（武汉）软件有限公司 | A kind of signal for electronic mutual inductor protects filter circuit |
| CN110120662A (en) * | 2019-04-28 | 2019-08-13 | 努比亚技术有限公司 | Circuit protection circuit |
| CN110120662B (en) * | 2019-04-28 | 2022-05-24 | 努比亚技术有限公司 | Line protection circuit |
| CN114201942A (en) * | 2022-02-18 | 2022-03-18 | 深圳佑驾创新科技有限公司 | Automatic checking method for capacitance parameter in circuit schematic diagram |
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Application publication date: 20151111 |