CN117239678A - Leakage detection and automatic protection circuit - Google Patents
Leakage detection and automatic protection circuit Download PDFInfo
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- CN117239678A CN117239678A CN202311501043.3A CN202311501043A CN117239678A CN 117239678 A CN117239678 A CN 117239678A CN 202311501043 A CN202311501043 A CN 202311501043A CN 117239678 A CN117239678 A CN 117239678A
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Abstract
The leakage detection and automatic protection circuit comprises linear Hall sensors respectively connected in series on a live wire and a zero wire; the Hall voltage output ends of the two linear Hall sensors are respectively connected with two signal input ends of a differential amplifier module, the output end of the differential amplifier module is connected with the input end of a comparator module, and the output end of the comparator is connected with the control end of a single-pole double-throw relay in a protection module; the protection module comprises a silicon controlled switch connected in series on a live wire or a zero wire, the control end of the silicon controlled switch is connected with two output ends of a single-pole double-throw relay, and the control end of the single-pole double-throw relay is connected with the output end of the comparator module. The invention adopts a hardware circuit form to realize the leakage detection, judges whether to shut off the AC power supply by detecting the leakage current, can realize the leakage detection and automatic shutoff functions without software programming, improves the safety of a protection circuit and reduces the cost of the detection circuit.
Description
Technical Field
The invention relates to the technical field of power supplies, in particular to a leakage detection and automatic protection circuit.
Background
The power supply protection circuit is a special circuit for protecting the power supply network and the electric equipment when the power supply is in an abnormal working state, and for a high-power alternating current power supply, the electric leakage phenomenon can cause serious equipment damage and even personal casualties, and the electric leakage protection circuit must be arranged.
In the prior art, most of the power leakage protection circuit flows back to the ground through a ground wire, personnel safety protection is realized through the upper-level protection, and part of product power supply design is not connected with the ground, so that the safety protection cannot be realized, and even if a product with the ground connection is connected, the power supply cannot be automatically powered off under the condition of leakage, the personnel safety is required to be tripped by means of an upper-level air switch, and personnel electric shock accidents caused by product leakage can often occur under the condition that the air switch is not available.
Although the fuse is generally installed on the main power supply line, the fuse can only protect against the condition of large current of ground fault, and cannot protect against the condition of electric leakage of small current of tens of milliamperes, for example, the danger of electric shock exists when the human body contact type electric leakage exceeds 30mA, and the fuse cannot protect personal safety.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention discloses a leakage detection and automatic protection circuit.
The invention relates to a leakage detection and automatic protection circuit, which is characterized by comprising linear Hall sensors respectively connected in series with a pair of input power lines; the Hall voltage output ends of the two linear Hall sensors are respectively connected with two signal input ends of a differential amplifier module, the output end of the differential amplifier module is connected with the input end of a comparator module, and the output end of the comparator is connected with the control end of a single-pole double-throw relay in a protection module;
the protection module comprises a silicon controlled switch which is connected in series with an input power line, the control end of the silicon controlled switch is connected with two output ends of a single-pole double-throw relay, the single-pole double-throw relay is an active device, the two output ends of the single-pole double-throw relay are respectively connected with resistors with different sizes, and the control end of the single-pole double-throw relay is connected with the output end of the comparator module.
Preferably, the output end of the comparator module is connected with the control end of the single-pole double-throw relay through a PMOS tube, the output end of the comparator module is connected with the grid electrode of the PMOS tube, the drain electrode of the PMOS tube is grounded, and the source electrode of the PMOS tube is connected with the single-pole double-throw relay.
Preferably, the linear Hall sensor adopts CC6900SO-30A.
Preferably, the differential amplifier module comprises a differential amplifier chip, a first signal input end of the differential amplifier chip is connected with a normal phase input end of the differential amplifier module and the ground through a fifth resistor and a sixth resistor respectively, and a second signal input end of the differential amplifier chip is connected with an inverted input end of the differential amplifier module and an output end of the differential amplifier chip through a third resistor and a fourth resistor respectively; the third and fifth resistance values and the fourth and sixth resistance values are respectively equal.
Preferably, the single pole double throw relay power supply is generated for a power converter connected with the leakage detection and automatic protection circuit, and the power supply is connected with a capacitor.
Preferably, the single pole double throw relay employs HFD23.
Preferably, the comparator module comprises a comparator chip, wherein a non-inverting input end of the comparator chip is connected with a reference voltage, an inverting input end of the comparator chip is connected with an output end of the differential amplifier module, and the reference voltage is obtained by dividing a seventh resistor and an eighth resistor which are connected in series between an external power supply and the ground.
Preferably, the pair of input power lines are an ac live line and a neutral line, or a dc power line and a ground line.
The invention has the following beneficial effects:
firstly, the leakage detection is realized in a hardware circuit mode, whether the alternating current power supply is closed or not is judged by detecting the leakage current, and the leakage detection and automatic turn-off functions can be realized without software programming.
And secondly, the pair of linear Hall sensors are utilized to realize induction detection, the detection range is wide, the detection result is irrelevant to the frequency and amplitude of the input alternating current, the leakage current does not flow through any detection device, and the high-power current only flows through one device of the bidirectional thyristor, so that the safety of a protection circuit is improved, and the cost of the detection circuit is reduced.
And thirdly, the leakage current is detected by detecting the current difference through a pair of linear Hall sensors, a ground wire is not needed, and the detection is carried out on the ground wire, so that the application range of the protection circuit is improved.
And fourthly, the automatic power restoration of the circuit is realized by adopting the cooperation of the capacitor and the active relay, and the power restoration time is convenient to adjust.
Drawings
FIG. 1 is a schematic diagram of an embodiment of a leakage detection and automatic protection circuit according to the present invention;
FIG. 2 is a schematic diagram of one embodiment of a differential amplifier module according to the present invention;
FIG. 3 is a schematic diagram of a comparator module according to one embodiment of the present invention;
the reference numerals in the figures are: the power supply comprises an L-live wire, an N-zero wire, a C-capacitor, a P-PMOS tube, a D-bidirectional thyristor, an R1-first resistor, an R2-second resistor, an R3-third resistor, an R4-fourth resistor, an R5-fifth resistor, an R6-sixth resistor, an R7-seventh resistor and an R8-eighth resistor.
Detailed Description
The present invention will be described in further detail with reference to the following examples, but the present invention is not limited to the following examples:
the invention relates to a leakage detection and automatic protection circuit, which is used for providing a leakage protection function for electric equipment connected to an input power supply, as shown in fig. 1, taking an alternating current input power supply as an example, the leakage detection and automatic protection circuit can be used for providing the leakage protection function for the electric equipment connected between an alternating current live wire and a zero wire, for example, the electric equipment in fig. 1 is an ACDC converter, and the protection circuit comprises linear Hall sensors respectively connected to the live wire and the zero wire in series; the Hall voltage output ends of the two linear Hall sensors are respectively connected with two signal input ends of the differential amplifier module, the output end of the differential amplifier module is connected with the input end of the comparator module, the differential amplifier module outputs differential voltage to the comparator module after differential amplification, and the output end of the comparator is connected with the single-pole double-throw relay in the protection module.
When any equipment connected with a power line, such as a system complete machine, is leaked to the ground, the currents flowing on the live wire and the zero wire generate a difference value due to the leakage, the difference between the currents detected by the two linear Hall sensors causes the voltage difference input to the input end of the differential amplifier module to be increased, the output voltage of the differential amplifier module is increased, the comparator module is connected with a reference voltage, and when the output voltage of the differential amplifier module is larger than the reference voltage, the output voltage of the comparator module is overturned to operate the protection modules connected in series on the live wire and/or the zero wire.
Wherein, the function of differential amplifier does: the output voltage is the voltage difference between the two signal inputs multiplied by the voltage gain of the differential amplifier.
The protection module comprises a silicon controlled switch connected in series on a live wire or a zero line, the control end of the silicon controlled switch is connected with two output ends of a single-pole double-throw relay, the two output ends of the single-pole double-throw relay are respectively connected with resistors with different sizes, and the control end of the single-pole double-throw relay is connected with the output end of the comparator module.
As shown in FIG. 1, the output end of the comparator module is connected with the control end of the single-pole double-throw relay through the source electrode of a PMOS tube P, the output end of the comparator module is connected with the grid electrode of the PMOS tube, the drain electrode of the PMOS tube is grounded, the source electrode of the PMOS tube is connected with the single-pole double-throw relay, the single-pole double-throw relay is an active device, the control end of the single-pole double-throw relay has no current during the closing period of the PMOS tube, the relay keeps an initial default state, the control end is high level, the output of the single-pole double-throw relay keeps the initial default state to the output of the first output end, the resistance value of a first resistor R1 connected with the first output end of the single-pole double-throw relay is smaller, the current of the first output end is larger, and the normal opening of the bidirectional thyristor can be maintained.
When the output voltage of the comparator module is turned over, the PMOS tube is started, the voltage of the control end of the single-pole double-throw relay connected with the source electrode of the PMOS tube is pulled down to a low level, the output current of the single-pole double-throw relay is switched to the output of the second output end, the resistance value of a second resistor R2 connected with the second output end of the single-pole double-throw relay is larger, the current of the second output end is reduced, the bidirectional thyristor cannot be maintained to be started, the bidirectional thyristor is closed, and as shown in figure 1, the alternating current is equivalent to the disconnection of an internal ACDC converter, and the ACDC converter does not work any more.
In a preferred embodiment, the power V1 of the single pole double throw relay is provided by the AC converter, the power V1 is connected with the capacitor C, when the ACDC converter (AC/dc converter) works normally, the capacitor is charged and continuously supplies power to the single pole double throw relay, when the leakage protection occurs, the protection module breaks the connection between the AC power and the internal ACDC converter, the ACDC converter does not work normally any more, at this time, the single pole double throw relay is continuously supplied with power by the capacitor C, the bidirectional thyristor is controlled to be kept off, after the discharge time lasts for a period of time T1, when the capacitor C is discharged or discharged to a lower voltage, the single pole double throw relay is restored to a normal state, the bidirectional thyristor device D can be turned on by electrifying, so that normal power supply is ensured, the protection circuit can automatically resume working after the leakage occurs, the discharge time T1 can be set to a longer time, generally tens of seconds to hundreds of seconds, and an operator can conveniently handle and decide whether to turn off the power supply.
A specific embodiment is given below, and specific models and specific circuit designs are given to each module, so as to more accurately describe the technical effects of the technical principle of the present invention.
The linear Hall sensor adopts CC6900SO-30A, and a high-precision low-noise linear Hall circuit and a low-impedance main current lead are integrated in the CC 6900-30A. When the sampling current flows through the main current lead, a magnetic field generated by the sampling current is induced on the Hall circuit, and a Hall voltage signal is output.
For CC6900SO-30A, during normal operation, the Hall voltage is output
VI = VCC / 2 + 0.067 ×IP*1.414，（1）
Wherein VCC is the power supply voltage of the linear Hall sensor, and IP is the wire current of the linear Hall sensor.
As shown in fig. 2, a specific real-time manner of the differential amplifier module in this embodiment includes a differential amplifier chip LM358DR, where a first signal input end of the differential amplifier chip is connected to a normal phase input end VP of the differential amplifier module and ground through a fifth resistor R5 and a sixth resistor R6, and a second signal input end of the differential amplifier chip is connected to an inverted phase input end VN of the differential amplifier module and an output end VLI of the differential amplifier chip through a third resistor R3 and a fourth resistor R4, respectively.
Assuming that the Hall voltages output by the two linear Hall sensors are VI+ and VI-, respectively, wherein VI+ represents the live wire current and VI-represents the zero wire current, the output voltage VLi of the differential amplifier module is equal to
VLi=(R4/R3)*(VI+-VI-)，（2）
Since in reality, the leakage means that the live current does not leak from the zero line to the ground, but leaks from other unknown areas, the live current must be greater than the zero line current when the leakage occurs, i.e., vi+ must be greater than VI-.
Assume that the wire currents of two linear hall sensors are respectively
IP (+) and IP (-), substituting formula (1)
Vli= (R4/R3) ((VCC/2+0.067×ip (+). 1.414) - (VCC/2+0.067×ip (-). 1.414)), vcc=5, r4=r6=116K, r3=r5=1K,
vli=116.1 (0.094738 (IP (+) -IP (-))), (3) can be obtained after simplification
Wherein IP (+) -IP (-) is the current difference of the two wires, i.e. leakage current.
Assuming that the comparator module output is required to be turned over when the leakage current is 30 milliamperes, when vli=0.33v is calculated after the leakage current is brought into the formula (3), the output level of the comparator module is turned over, that is, the compared reference voltage of the comparator module should be 0.33V.
An embodiment of the comparator module is shown in fig. 3, and comprises a comparator chip AP331AWG, wherein a non-inverting input terminal of the comparator chip is connected with a reference voltage VREF, and an inverting input terminal VCN of the comparator chip is connected with an output terminal VLI of the differential amplifier chip.
The reference voltage VREF is obtained by dividing a voltage of 3.3V by a seventh resistor R7 and an eighth resistor R8 connected in series, where r7=90k and r8=10k, and the reference voltage vref=0.33V. Wherein the 3.3V voltage can also be obtained by converting ac power to dc 3.3V voltage by ACDC converter.
The power supply voltage of the comparator chip is consistent with that of the single-pole double-throw relay, so that the PMOS tube can be completely closed when the comparator module outputs high-level voltage.
As previously described, when the leakage current reaches 30 milliamperes, the differential amplifier module output voltage will exceed 0.33V, at which point the comparator module output voltage will flip.
After the output voltage of the comparator module is turned over, the PMOS tube is converted into an on state from an off state, and the voltage of the control end of the single-pole double-throw relay is pulled down.
The single pole double throw relay adopts HFD23 as an active device and is provided with two output ends, in the specific embodiment, a first resistor and a second resistor which are connected with the two output ends are respectively R1=5.5K and R2=1M, the power supply voltage of the single pole double throw relay is 5V,
the control terminal current Igt is continuously provided from R1 to the control terminal of the triac D, and is calculated according to the product specifications of the HFD23 device:
igt=220v1.414/r1=220×1.414/5.5k=56 mA. The current is larger than the minimum conduction control current IGT of the bidirectional thyristor D, the bidirectional thyristor is conducted, and the circuit works normally.
When leakage occurs and the leakage circuit is larger than the safety current by 30mA, the comparator module outputs a low level, the PMOS is conducted and pulled down to the control end of the single-pole double-throw relay, the output end of the relay is switched to a second output end, and at the moment, the current Igt=220V 1.414/R2=220×1.414/1000 K=0.3 mA at the control end of the bidirectional thyristor D is smaller than the minimum conduction control current of the bidirectional thyristor D, and at the moment, the bidirectional thyristor cannot be conducted, and the power supply is disconnected, so that the protection effect is achieved.
In the specific embodiment, the single-pole double-throw relay is connected with a 1.5F super capacitor, at the moment, although an ACDC converter (alternating current-direct current converter) does not work any more, the super capacitor can still continuously supply power to enable the single-pole double-throw relay to keep an action state, the action keeping time T is the discharge time of a battery,
assuming that the internal resistance of the relay coil is 125 omega, C=1.5F, the lowest working voltage is 4V, the single-pole double-throw relay power supply V1=5.5V, T (approximately 125 x C) (5.5V-4V) =281 seconds can be obtained through calculation, the relay always keeps an action state in the period of time, so that the disconnection state of the bidirectional thyristor is kept to be non-conductive, and when the super capacitor discharges to below 4V, the relay is reset to be in a normal state, and the bidirectional thyristor can be conducted after the power is supplied, so that normal power supply is ensured.
In order to simplify the design, the differential amplifier module and the comparator module are usually powered by the subsequent ACDC converter, and after the power is off, the ACDC converter cannot work normally, so that the differential amplifier module and the comparator module cannot work, and at the moment, the single-pole double-throw relay cannot be controlled by the output signal of the comparator module.
The invention has the following beneficial effects:
firstly, the leakage detection is realized in a hardware circuit mode, whether the alternating current power supply is closed or not is judged by detecting the leakage current, and the leakage detection and automatic turn-off functions can be realized without software programming.
And secondly, the pair of linear Hall sensors are utilized to realize induction detection, the detection range is wide, the detection result is irrelevant to the frequency and amplitude of the input alternating current, the leakage current does not flow through any detection device, and the high-power current only flows through one device of the bidirectional thyristor, so that the safety of a protection circuit is improved, and the cost of the detection circuit is reduced.
And thirdly, the leakage current is detected by detecting the current difference through a pair of linear Hall sensors, a ground wire is not needed, and the detection is carried out on the ground wire, so that the application range of the protection circuit is improved.
And fourthly, the automatic power restoration of the circuit is realized by adopting the cooperation of the capacitor and the active relay, and the power restoration time is convenient to adjust.
The foregoing is a further detailed description of the invention in connection with specific preferred embodiments, and it is not intended that the invention be limited to these descriptions. Other embodiments of the invention, which are apparent to those skilled in the art to which the invention pertains without departing from its technical scope, shall be covered by the protection scope of the invention.
Claims (8)
1. The leakage detection and automatic protection circuit is characterized by comprising linear Hall sensors which are respectively connected in series with a pair of input power lines; the Hall voltage output ends of the two linear Hall sensors are respectively connected with two signal input ends of a differential amplifier module, the output end of the differential amplifier module is connected with the input end of a comparator module, and the output end of the comparator is connected with the control end of a single-pole double-throw relay in a protection module;
the protection module comprises a silicon controlled switch which is connected in series with an input power line, the control end of the silicon controlled switch is connected with two output ends of a single-pole double-throw relay, the single-pole double-throw relay is an active device, the two output ends of the single-pole double-throw relay are respectively connected with resistors with different sizes, and the control end of the single-pole double-throw relay is connected with the output end of the comparator module.
2. The leakage detection and automatic protection circuit according to claim 1, wherein the output end of the comparator module is connected with the control end of the single-pole double-throw relay through a PMOS tube, the output end of the comparator module is connected with the grid electrode of the PMOS tube, the drain electrode of the PMOS tube is grounded, and the source electrode of the PMOS tube is connected with the single-pole double-throw relay.
3. The leakage detection and automatic protection circuit according to claim 1, wherein the linear hall sensor employs CC6900SO-30A.
4. The leakage detection and automatic protection circuit according to claim 1, wherein the differential amplifier module comprises a differential amplifier chip, a first signal input end of the differential amplifier chip is connected with a positive input end of the differential amplifier module and ground through a fifth resistor and a sixth resistor respectively, and a second signal input end of the differential amplifier chip is connected with an inverting input end of the differential amplifier module and an output end of the differential amplifier chip through a third resistor and a fourth resistor respectively; the third and fifth resistance values and the fourth and sixth resistance values are respectively equal.
5. The leakage detection and automatic protection circuit according to claim 1, wherein the single pole double throw relay power supply is generated for a power converter to which the leakage detection and automatic protection circuit is connected, and the power supply is connected with a capacitor.
6. The leakage detection and automatic protection circuit according to claim 1, wherein the single pole double throw relay employs HFD23.
7. The leakage detection and automatic protection circuit according to claim 1, wherein the comparator module comprises a comparator chip, a non-inverting input terminal of the comparator chip is connected with a reference voltage, an inverting input terminal of the comparator chip is connected with an output terminal of the differential amplifier module, and the reference voltage is obtained by dividing a voltage by a seventh resistor and an eighth resistor connected in series between an external power supply and ground.
8. The leakage detection and automatic protection circuit according to claim 1, wherein the pair of input power lines are ac live and neutral lines, or dc power and ground lines.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311501043.3A CN117239678A (en) | 2023-11-13 | 2023-11-13 | Leakage detection and automatic protection circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202311501043.3A CN117239678A (en) | 2023-11-13 | 2023-11-13 | Leakage detection and automatic protection circuit |
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| CN117239678A true CN117239678A (en) | 2023-12-15 |
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| CN202311501043.3A Pending CN117239678A (en) | 2023-11-13 | 2023-11-13 | Leakage detection and automatic protection circuit |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN119199638A (en) * | 2024-10-24 | 2024-12-27 | 国网山东省电力公司莱芜供电公司 | A non-intrusive line tower leakage current monitor based on AI learning |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2045152U (en) * | 1988-12-02 | 1989-09-27 | 孟震峰 | Household automatic electric current controller |
| CN101141060A (en) * | 2006-09-08 | 2008-03-12 | 鸿富锦精密工业（深圳）有限公司 | Auto-power-off control device |
| CN101431226A (en) * | 2007-11-05 | 2009-05-13 | 鸿富锦精密工业（深圳）有限公司 | Power supply protection circuit |
| CN202260378U (en) * | 2011-09-14 | 2012-05-30 | 吴茂义 | Leakage protector |
-
2023
- 2023-11-13 CN CN202311501043.3A patent/CN117239678A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN2045152U (en) * | 1988-12-02 | 1989-09-27 | 孟震峰 | Household automatic electric current controller |
| CN101141060A (en) * | 2006-09-08 | 2008-03-12 | 鸿富锦精密工业（深圳）有限公司 | Auto-power-off control device |
| CN101431226A (en) * | 2007-11-05 | 2009-05-13 | 鸿富锦精密工业（深圳）有限公司 | Power supply protection circuit |
| CN202260378U (en) * | 2011-09-14 | 2012-05-30 | 吴茂义 | Leakage protector |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN119199638A (en) * | 2024-10-24 | 2024-12-27 | 国网山东省电力公司莱芜供电公司 | A non-intrusive line tower leakage current monitor based on AI learning |
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