CN104749416A - Electricity leakage detecting protecting circuit - Google Patents
Electricity leakage detecting protecting circuit Download PDFInfo
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- CN104749416A CN104749416A CN201510114331.2A CN201510114331A CN104749416A CN 104749416 A CN104749416 A CN 104749416A CN 201510114331 A CN201510114331 A CN 201510114331A CN 104749416 A CN104749416 A CN 104749416A
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- circuit
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- leakage current
- current detection
- detection protection
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Abstract
The invention provides an electricity leakage detecting protecting circuit. The electricity leakage detecting protecting circuit comprises a small-frequency amplifying circuit which is connected with a secondary side of a current transformer, and a pulse conversion circuit which is connected with the output end of the small-frequency modifying circuit and used for generating a pulse signal of which the width is in proportional to the output current of the small-frequency amplifying circuit. According to the electricity leakage detecting protecting circuit, the small-frequency amplifying circuit is arranged, so that high-frequency interference ripple wave can be effectively filtered, and the interference resistance of the detecting circuit can be improved; the high frequency interference can be effectively inhibited while ensuring high gain amplification of the small-frequency electricity leakage signal; the requirement on the mutual inductor is small; the mutual inductor with a magnetic core framework is avoided; therefore, the problem that the current mutual inductor is easily saturated can be solved; the current mutual inductor is small in size, and the complexity and cost can be decreased.
Description
Technical field
The present invention relates to detection of electrical leakage field, in particular to a kind of leakage current detection protection circuit.
Background technology
The ultimate principle of electric-leakage detection circuit is all based on Hough current law: the algebraic sum flowing into the electric current of any node in circuit is zero, and it adopts zero-sequence transformer as sampling element.In the normal situation of electrical equipment, the vector of each phase current equals zero, therefore the secondary side winding no signal of zero-sequence transformer exports, when there is leak current fault, the vector of each phase current is non-vanishing, fault current makes the annular core of zero-sequence transformer produce magnetic flux, and the secondary side of current transformer has induction current.Present leakage current detection protection circuit, the process for front end signal is generally as follows:
The secondary side of current transformer has sensor current signal, and (patent: 200880106718.1), if voltage signal is less, then by amplifier by voltage amplification (patent: 201210425853.0) to be directly converted to voltage signal use.
If existing circuit shortcoming is that leakage current test accuracy requirement is high, and sensing range wide (such as 0 ~ 100mA), magnetic saturation is there is for avoiding zero-sequence transformer, the magnetic core of mutual inductor needs to have larger area, namely mutual inductor size is larger, be unfavorable for testing circuit miniaturization, and good output linearity degree will be kept in wider range of current, the complexity of mutual inductor realization can be increased and realize cost.
Summary of the invention
The present invention aims to provide a kind of leakage current detection protection circuit that can solve current transformer magnetic saturation problem.
The invention provides a kind of leakage current detection protection circuit, comprising: low-frequency amplifier circuit, be connected with the secondary side of current transformer; Pulse switching circuit, is connected with the output terminal of low-frequency amplifier circuit, and the pulse signal that the output current producing width and low-frequency amplifier circuit is proportional.
Further, leakage current detection protection circuit also comprises: pulse signal filtering circuit, is connected with the output terminal of pulse switching circuit, to remove the interference ripple in pulse signal.
Further, low-frequency amplifier circuit comprises: operational amplifier, and the backward end of operational amplifier is connected with the secondary side of current transformer, is arranged in series amplification resistance parallel with one another and the first filter capacitor between the output terminal of operational amplifier and backward end; The forward end of operational amplifier is connected with direct supply.
Further, the second filter capacitor has been arranged in series between the forward end of operational amplifier and ground.
Further, pulse switching circuit comprises the first comparer and bleeder circuit; The first end of bleeder circuit is connected with the output terminal of low-frequency amplifier circuit, the second end ground connection of bleeder circuit; Bleeder circuit comprises the first divider resistance and second divider resistance of series connection mutually, has output node between the first divider resistance and the second divider resistance; The forward end of the first comparer is connected with output node, and the backward end of the first comparer is connected with the output terminal of low-frequency amplifier circuit.
Further, bleeder circuit also comprises three filter capacitor in parallel with the second divider resistance.
Further, pulse signal filtering circuit comprises the second comparer and reference value arranges circuit; Reference value arranges circuit and comprises first reference value and arrange circuit and the second reference value arranges circuit; First reference value is arranged on circuit has the first reference point, and the first reference point is connected with the output terminal of pulse switching circuit and the forward end of the second comparer; Second reference value is arranged on circuit has the second reference point, and the second reference point is connected with the backward end of the second comparer, and the reference voltage of the first reference point is greater than the reference voltage of the second reference point.
Further, the first end that first reference value arranges circuit is connected with direct supply, and first reference value arranges the second end ground connection of circuit, and first reference value arranges on circuit and has been arranged in series at least two divider resistances; The first end that second reference value arranges circuit is connected with direct supply, and the second reference value arranges the second end ground connection of circuit, and the second reference value arranges on circuit and has been arranged in series at least two divider resistances.
According to leakage current detection protection circuit of the present invention, by arranging low-frequency amplifier circuit, can effectively filtering high frequency interference ripple, improve the antijamming capability of testing circuit.Effectively high frequency interference is inhibit while the plus and blowup ensureing low frequency electric leakage signal, low to transformer request, do not need the mutual inductor using band magnetic core framework.Thus the easily saturated problem of current transformer can be solved, make current transformer can more miniaturization, reduce complexity and cost.
Accompanying drawing explanation
The accompanying drawing forming a application's part is used to provide a further understanding of the present invention, and schematic description and description of the present invention, for explaining the present invention, does not form inappropriate limitation of the present invention.In the accompanying drawings:
Fig. 1 is the principle schematic according to leakage current detection protection circuit of the present invention;
Embodiment
Below with reference to the accompanying drawings and describe the present invention in detail in conjunction with the embodiments.
As shown in Figure 1, according to leakage current detection protection circuit of the present invention, comprising: low-frequency amplifier circuit, be connected with the secondary side of current transformer; Pulse switching circuit, is connected with the output terminal of low-frequency amplifier circuit, and the pulse signal that the output current producing width and low-frequency amplifier circuit is proportional.The present invention is by arranging low-frequency amplifier circuit, directly leakage current signal is converted to the higher voltage signal of amplitude, adopt compared to existing technology and current signal is changed to voltage signal, again by the working method of voltage signal amplification, low-frequency amplifier circuit of the present invention, to High frequency filter, effectively inhibits high frequency interference while the plus and blowup ensureing low frequency electric leakage signal, low to transformer request, do not need the mutual inductor using band magnetic core framework.Thus the easily saturated problem of current transformer can be solved, make current transformer can more miniaturization, reduce complexity and cost.
Particularly, shown in composition graphs 1, low-frequency amplifier circuit comprises operational amplifier U6-B, the backward end of operational amplifier U6-B is connected with the secondary side of current transformer, is arranged in series amplification resistance R225 parallel with one another and the first filter capacitor C232 between the output terminal of operational amplifier U6-B and backward end; The forward end of operational amplifier U6-B is connected with direct supply, usually, has been arranged in series the second filter capacitor C272 between the forward end of operational amplifier and ground, thus prevents the direct supply be connected with forward end from disturbing.
In the present invention, the low frequency part in leakage current signal can effectively be amplified by low-frequency amplifier circuit, and the undesired signal of filtering high frequency, namely the electric capacity C232 of circuit Small And Medium Capacity can by the high-frequency interferencing signal short circuit in current signal, and high-frequency signal gain myopia is β
h=1/2 π fc<<1, realizes the decay of high-frequency interferencing signal, and then low frequency signal amplifies through amplifying resistance R225, and low frequency signal gain myopia is β
l=R=3300 realizes the amplification of low frequency signal.
In addition, low-frequency amplifier circuit of the present invention does not adopt testing circuit conventional at present like that the current signal that mutual inductor produces to be converted to voltage signal, again by working method that voltage signal is amplified by amplifier, but directly leakage current signal is input to backward end, by amplifying, faint current signal is converted to the higher voltage signal of amplitude.The testing circuit that contrast is at present conventional, will disturb ripple also to treat as effective dose integration, the present invention adopts filtering circuit, can effective filtering interfering ripple, the antijamming capability of raising testing circuit.Simultaneously because manner of comparison is faster than integral way speed, the detection protection speed of circuit can be improved.
Shown in composition graphs 1, in the present invention, pulse switching circuit comprises the first comparer U14-A and bleeder circuit, and the first end of bleeder circuit is connected with the output terminal of low-frequency amplifier circuit, the second end ground connection of bleeder circuit; Bleeder circuit comprises the first divider resistance R230 and the second divider resistance R5 of series connection mutually, has output node between the first divider resistance R230 and the second divider resistance R5; The forward end of the first comparer U14-A is connected with output node, and the backward end of the first comparer U14-A is connected with the output terminal of low-frequency amplifier circuit.Namely in the output signal of low-frequency amplifier circuit, on the forward end being connected to the first comparer U14-A by bleeder circuit and backward end, in theory, when the operational amplifier U6-B output signal in low-frequency amplifier circuit is greater than zero, the first comparer U14-A output low level.
In the present invention, pulse switching circuit is by bleeder circuit and the first comparer, produce the pulse signal that width is directly proportional to current signal, the reference voltage amplifying the direct supply that resistance R225 is connected with operational amplifier U6-B forward end in low-frequency amplifier circuit determines the proportionate relationship of pulse width and current signal.Amplify resistance R225 and reference voltage in debugging low-frequency amplifier circuit, can make to start to produce pulse signal when leakage current is 20mA, and pulse signal reaches desired width when 25mA.Now due to the ripple interference of completely filtering in low-frequency amplifier circuit amplifying signal, the forward position of pulse signal and rear edge are with the interference ripple of low amplitude value.Usually, requiring in relatively low leakage circuit, the output signal of the first comparer directly can export the control signal as IC.
Preferably, leakage current detection protection circuit of the present invention is in order to eliminate ripple interference, and be also provided with pulse signal filtering circuit, pulse signal filtering circuit comprises the second comparer and reference value arranges circuit; Reference value arranges circuit and comprises first reference value and arrange circuit and the second reference value arranges circuit; First reference value is arranged on circuit has the first reference point, and the first reference point is connected with the output terminal of pulse switching circuit and the forward end of the second comparer; Second reference value is arranged on circuit has the second reference point, and the second reference point is connected with the backward end of the second comparer, and the reference voltage of the first reference point is greater than the reference voltage of the second reference point.Namely by arranging the second comparer and corresponding reference voltage, compared with setting reference value by the pulse signal with low amplitude value interference ripple, filtering amplitude is less than the interference ripple of reference value, makes pulse signal more clean, for IC provides desirable detection signal.
Shown in composition graphs 1, the first end that first reference value arranges circuit is connected with direct supply, and first reference value arranges the second end ground connection of circuit, and first reference value arranges on circuit and has been arranged in series at least two divider resistances; The first end that second reference value arranges circuit is connected with direct supply, second reference value arranges the second end ground connection of circuit, second reference value arranges on circuit and has been arranged in series at least two divider resistances, selects suitable divider resistance, can regulate corresponding reference value.
As can be seen from the above description, the above embodiments of the present invention achieve following technique effect:
According to leakage current detection protection circuit of the present invention, by arranging low-frequency amplifier circuit, can effectively filtering high frequency interference ripple, improve the antijamming capability of testing circuit.Effectively high frequency interference is inhibit while the plus and blowup ensureing low frequency electric leakage signal, low to transformer request, do not need the mutual inductor using band magnetic core framework.Thus the easily saturated problem of current transformer can be solved, make current transformer can more miniaturization, reduce complexity and cost.
The foregoing is only the preferred embodiments of the present invention, be not limited to the present invention, for a person skilled in the art, the present invention can have various modifications and variations.Within the spirit and principles in the present invention all, any amendment done, equivalent replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (8)
1. a leakage current detection protection circuit, is characterized in that, comprising:
Low-frequency amplifier circuit, is connected with the secondary side of current transformer;
Pulse switching circuit, is connected with the output terminal of described low-frequency amplifier circuit, and the pulse signal that the output current producing width and described low-frequency amplifier circuit is proportional.
2. leakage current detection protection circuit according to claim 1, is characterized in that, described leakage current detection protection circuit also comprises:
Pulse signal filtering circuit, is connected with the output terminal of described pulse switching circuit, to remove the interference ripple in pulse signal.
3. leakage current detection protection circuit according to claim 1 and 2, is characterized in that, described low-frequency amplifier circuit comprises:
Operational amplifier, the backward end of described operational amplifier is connected with the secondary side of described current transformer, is arranged in series amplification resistance parallel with one another and the first filter capacitor between the output terminal of described operational amplifier and backward end;
The forward end of described operational amplifier is connected with direct supply.
4. leakage current detection protection circuit according to claim 3, is characterized in that,
The second filter capacitor has been arranged in series between the forward end of described operational amplifier and ground.
5. leakage current detection protection circuit according to claim 1 and 2, is characterized in that,
Described pulse switching circuit comprises the first comparer and bleeder circuit;
The first end of described bleeder circuit is connected with the output terminal of described low-frequency amplifier circuit, the second end ground connection of described bleeder circuit;
Described bleeder circuit comprises the first divider resistance and second divider resistance of series connection mutually, has output node between described first divider resistance and described second divider resistance;
The forward end of described first comparer is connected with described output node, and the backward end of described first comparer is connected with the output terminal of described low-frequency amplifier circuit.
6. leakage current detection protection circuit according to claim 5, is characterized in that,
Described bleeder circuit also comprises three filter capacitor in parallel with described second divider resistance.
7. leakage current detection protection circuit according to claim 2, is characterized in that,
Described pulse signal filtering circuit comprises the second comparer and reference value arranges circuit;
Described reference value arranges circuit and comprises first reference value and arrange circuit and the second reference value arranges circuit;
Described first reference value is arranged on circuit has the first reference point, and described first reference point is connected with the output terminal of described pulse switching circuit and the forward end of described second comparer;
Described second reference value is arranged on circuit has the second reference point, and described second reference point is connected with the backward end of described second comparer, and the reference voltage of described first reference point is greater than the reference voltage of described second reference point.
8. leakage current detection protection circuit according to claim 7, is characterized in that,
The first end that described first reference value arranges circuit is connected with direct supply, and described first reference value arranges the second end ground connection of circuit, and described first reference value arranges on circuit and has been arranged in series at least two divider resistances;
The first end that described second reference value arranges circuit is connected with direct supply, and described second reference value arranges the second end ground connection of circuit, and described second reference value arranges on circuit and has been arranged in series at least two divider resistances.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
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| CN201510114331.2A CN104749416A (en) | 2015-03-16 | 2015-03-16 | Electricity leakage detecting protecting circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201510114331.2A CN104749416A (en) | 2015-03-16 | 2015-03-16 | Electricity leakage detecting protecting circuit |
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| CN104749416A true CN104749416A (en) | 2015-07-01 |
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| CN201510114331.2A Pending CN104749416A (en) | 2015-03-16 | 2015-03-16 | Electricity leakage detecting protecting circuit |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105445587A (en) * | 2015-12-07 | 2016-03-30 | 珠海格力电器股份有限公司 | Serial connection fault arc detection circuit |
| CN116500329A (en) * | 2023-06-25 | 2023-07-28 | 泉州昆泰芯微电子科技有限公司 | Broadband current measurement method, device, system and chip |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN105445587A (en) * | 2015-12-07 | 2016-03-30 | 珠海格力电器股份有限公司 | Serial connection fault arc detection circuit |
| CN116500329A (en) * | 2023-06-25 | 2023-07-28 | 泉州昆泰芯微电子科技有限公司 | Broadband current measurement method, device, system and chip |
| CN116500329B (en) * | 2023-06-25 | 2023-09-12 | 泉州昆泰芯微电子科技有限公司 | Broadband current measurement method, device, system and chip |
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Application publication date: 20150701 |
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