CN213151905U - Protection circuit, lightning protection device and electronic equipment of weak current power supply port - Google Patents
Protection circuit, lightning protection device and electronic equipment of weak current power supply port Download PDFInfo
- Publication number
- CN213151905U CN213151905U CN202021579924.9U CN202021579924U CN213151905U CN 213151905 U CN213151905 U CN 213151905U CN 202021579924 U CN202021579924 U CN 202021579924U CN 213151905 U CN213151905 U CN 213151905U
- Authority
- CN
- China
- Prior art keywords
- circuit
- sub
- protection
- current power
- filtering
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Active
Links
Images
Landscapes
- Emergency Protection Circuit Devices (AREA)
Abstract
The utility model discloses a protection circuit, a lightning protection device and an electronic device of a weak current power port, wherein the protection circuit comprises a high-voltage protection sub-circuit, a filtering time-delay sub-circuit, a residual voltage absorption sub-circuit and a damping sub-circuit which are connected in sequence; one end of the high-voltage protection sub-circuit is connected with the weak-current power supply port, and the other end of the high-voltage protection sub-circuit is connected with the filtering delay sub-circuit and is used for performing high-voltage protection on the weak-current power supply port; the filtering delay sub-circuit utilizes the self-generated delay function to enable the high-voltage protection sub-circuit to generate response before the residual voltage absorption sub-circuit; the residual voltage absorption sub-circuit is used for absorbing residual voltage which is not completely discharged after the piezoresistor in the high-voltage protection sub-circuit is broken down; the damping sub-circuit is used for increasing the inductive reactance of the inductance coil, generating a damping effect and inhibiting common-mode interference current. Adopt the utility model discloses, can carry out multistage protection and filtering through this protection circuit to eliminate common mode interference, differential mode interference, realize the protection to EFT, Surge.
Description
Technical Field
The utility model relates to a power port protection technology especially relates to an electric Fast Transient pulse crowd (Electrical Fast Transient, EFT), Surge impact (Surge) protective circuit, lightning protection device, electronic equipment of weak current power port.
Background
The protection circuit of the traditional weak current power supply port is mostly realized by adopting an ampere rule X/Y capacitor and filtering differential mode/common mode interference through a filtering function. However, such protection circuits have a very limited immunity to interference and, due to the high transient voltages, there is a risk of the capacitor breaking down. Thus, the protection against EFT and Surge is obviously insufficient. Therefore, it is urgent to develop a new protection technology for weak current power port based on the requirements of electromagnetic compatibility (EMC) performance and circuit reliability.
When voltage in a circuit suddenly changes, the voltage dependent resistor (MOV) is broken down, the resistance value of the voltage dependent resistor is sharply reduced, and current in the circuit is shunted and discharged. And Transient Voltage Suppressor (TVS) has faster response speed to the peak Voltage, and the TVS can absorb instantaneous large pulse power between the two poles and clamp the Voltage to a preset level, so that the Transient overvoltage phenomenon can be quickly and efficiently dealt with.
Therefore, on the basis of protection of the traditional safety capacitor and common mode inductor, when a new weak current power supply port protection technology is researched and developed, the piezoresistor and the TVS tube can be considered to be added for matching use, and the protection performance of the weak current power supply port is further improved.
SUMMERY OF THE UTILITY MODEL
In view of this, the main object of the present invention is to provide a protection circuit for a weak current power port, which aims to perform multi-stage protection and filtering through the protection circuit to eliminate common mode interference and differential mode interference, thereby realizing protection of EFT and Surge; and further improve the protection effect of the protection circuit.
In order to achieve the above purpose, the technical scheme of the utility model is as follows:
a protection circuit of a weak current power supply port comprises a high-voltage protection sub-circuit, a filtering delay sub-circuit, a residual voltage absorption sub-circuit and a damping sub-circuit which are sequentially connected;
one end of the high-voltage protection sub-circuit is connected with the weak current power supply port, and the other end of the high-voltage protection sub-circuit is connected with the filtering delay sub-circuit and is used for performing high-voltage protection on the weak current power supply port;
the filtering delay sub-circuit utilizes the self-generated delay function to enable the high-voltage protection sub-circuit to generate response before the residual voltage absorption sub-circuit;
the residual voltage absorption sub-circuit is used for absorbing residual voltage which is not completely discharged after the piezoresistor in the front-stage sub-circuit is broken down;
the damping sub-circuit is used for increasing the inductive reactance of the inductance coil, generating a damping effect and inhibiting common-mode interference current.
Wherein: the damping sub-circuit is followed by:
and the common-mode filtering sub-circuit is used for consuming and filtering common-mode interference through filtering action so as to protect a post-stage working circuit.
The connection mode of the high-voltage protection sub-circuit and the weak current direct current power port is as follows:
one end of the piezoresistor Z1 is connected with the anode of the direct-current power supply, and the other end is grounded PE; one end of the piezoresistor Z2 is connected with the positive pole of the direct-current power supply, and the other end is connected with 0V ground; one end of the piezoresistor Z3 is connected to 0V ground, and the other end is connected to ground PE.
The connection mode of the filtering delay sub-circuit and the high-voltage protection sub-circuit is as follows: the capacitor C1 is connected across the two ends of the rear stage of the piezoresistor Z2, the input pin of the inductor L1 is connected with one end of the capacitor C1, and the input pin of the inductor L2 is connected with the other end of the capacitor C1.
The residual voltage absorption sub-circuit and the filtering delay sub-circuit are connected in the following mode:
the two poles of the TVS tube D3 are bridged between the two output pins of the inductor L1 and the inductor L2, the TVS tube D1 and the TVS tube D2 are respectively led out from the two pins of the TVS tube D3 and connected to the ground PE, and the two poles of the capacitor C2 are connected with the two ends of the rear stage of the TVS tube D3.
The connection mode of the damping sub-circuit and the filtering delay sub-circuit is as follows:
the capacitor C2 is connected to the two input pins of a common mode inductor L3.
The common mode filtering sub-circuit is connected with the damping sub-circuit in the following mode:
and the capacitors C3 and C4 are connected in series from two output pins of the common-mode inductor L3, and the middle of the capacitors C3 and C4 is grounded by PE.
A lightning protection device applying the weak current power supply port protection circuit is provided.
An electronic device applying the weak current power supply port protection circuit.
The utility model discloses protection circuit of weak current power port has following beneficial effect:
1) the utility model discloses a protection circuit adopts multistage protection and multilayer filtering to handle, all has fine suppression effect to the transient state electric current and the transient state high pressure that differential mode interference and common mode interference produced. The piezoresistors Z1 and Z3 are firstly broken down, residual voltage formed after breakdown is clamped and protected by a rear-stage TVS tube, and the common-mode inductor L3 and the Y capacitor C3/C4 can also play a role in inhibiting a common mode, so that common-mode interference is filtered; the voltage dependent resistor Z2 is firstly broken down, residual voltage formed after breakdown is clamped and protected by a TVS tube D3, and capacitors C1 and C2 are matched with inductors L1 and L2 to play a role in differential mode low-pass filtering, so that differential mode interference is filtered.
2) The embodiment of the utility model provides an in the protection circuit that provides be applicable to and provide the protection for the weak current power supply circuit that multiple occasion was used, especially to the protection of EFT, Surge, show to have promoted the electromagnetic compatibility performance.
Drawings
Fig. 1 is a schematic diagram of a multi-stage protection architecture of a protection circuit of a weak current power port according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a protection circuit of a weak current power port according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and embodiments of the present invention.
Fig. 1 is a schematic diagram of a multi-stage protection architecture of a weak current power port protection circuit according to an embodiment of the present invention.
As shown in fig. 1, the multi-stage protection architecture of the weak current power port protection circuit mainly includes a multi-stage sub-circuit, i.e., a high-voltage protection sub-circuit, a filtering delay sub-circuit, a residual voltage absorption sub-circuit, a damping sub-circuit and a common-mode filtering sub-circuit, which are connected in sequence.
Fig. 2 is a schematic diagram of a protection circuit of a weak current power port according to an embodiment of the present invention.
Referring to fig. 2, the protection circuit of the weak current power supply port specifically includes:
the first-stage protection, namely a high-voltage protection sub-circuit, mainly comprises piezoresistors Z1, Z2 and Z3;
the pi-type filtering, namely a filtering delay sub-circuit, mainly comprises an inductor L1, an inductor L2, a capacitor C1 and a capacitor C2;
the second stage of protection, namely the residual voltage absorption sub-circuit, mainly comprises TVS tubes D1, D2 and D3;
the third stage of protection, the damping subcircuit, mainly includes inductance L3;
the fourth stage of protection, i.e. the common mode filtering sub-circuit, mainly comprises capacitors C3, C4.
In the above circuit element: z1, Z2 and Z3 are piezoresistors; c1 and C2 are X capacitors; d1, D2 and D3 are TVS tubes; l1 and L2 are differential mode inductors; l3 is common mode inductance; c3 and C4 are Y capacitors.
Referring to fig. 2, the embodiment of the present invention provides a protection circuit for a weak current power port, which is especially used for realizing and improving protection of EFT and Surge against the deficiency of EMC performance of the existing protection circuit.
In this embodiment, taking the following weak current power supply port (dc 24V power supply) to be protected as an example, as described above, the protection circuit mainly includes the following components: the device comprises a piezoresistor, a safety capacitor, a differential mode inductor, a TVS (transient voltage suppressor) tube and a common mode inductor. The circuit formed by the components realizes multi-stage protection, and ensures that a post-stage circuit is not damaged by EFT and Surge.
The protection circuit structure of the weak current power supply port and the working principle thereof are as follows:
the utility model discloses protection circuit has contained level four protection circuit and one-level pi type filter circuit, wherein:
the first-stage protection, namely a high-voltage protection sub-circuit, mainly comprises piezoresistors Z1, Z2 and Z3, wherein one end of the piezoresistor Z1 is connected with a direct current 24V positive electrode, and the other end of the piezoresistor Z1 is grounded PE; one end of the piezoresistor Z2 is connected with a direct current 24V positive electrode, and the other end is connected with 0V ground; one end of the piezoresistor Z3 is connected to 0V ground, and the other end is connected to ground PE. In practical application, the high-voltage protection sub-circuit is mainly used for preventing strong electricity such as thunder and lightning, high-voltage and ultrahigh-voltage alternating current power transmission and transformation and the like from being connected into a weak-current power circuit in series to burn out a power supply and electronic equipment connected with the power supply.
The pi-type filter circuit, i.e. the filter delay sub-circuit, is mainly composed of inductors L1, L2, capacitors C1 and C2, wherein an X capacitor C1 is bridged at two ends of the rear stage of a voltage dependent resistor Z2, an input pin of the inductor L1 is connected with one end of the capacitor C1, and an input pin of the inductor L2 is connected with the other end of the capacitor C1.
The second stage of protection, namely the residual voltage absorption sub-circuit, is mainly composed of TVS tubes D1, D2 and D3, two poles of the TVS tube D3 are bridged between two output pins of inductors L1 and L2, TVS tubes D1 and D2 are respectively led out from two pins of D3 and connected to ground PE, and two poles of a capacitor C2 are connected with two ends of the rear stage of the TVS tube D3.
Here, in the second stage protection, the TVS tube may be located in a perfect combination with the pi-filter circuit, and the TVS tubes D1, D2, and D3 must be placed after the inductors L1 and L2 and before the capacitor C2 and the inductor L3 of the third stage protection circuit. The reason for this design is: the response time of the TVS tube is far faster than that of the piezoresistor, so that the characteristic that the current of the inductors L1 and L2 cannot change suddenly is utilized to play a role in delaying, and the high-voltage protection sub-circuit generates response before the residual voltage absorption sub-circuit. Therefore, the problem that the piezoresistor of the first-stage protection does not respond and the TVS tube of the later stage responds first can be well avoided.
The reason why the capacitor C2 and the inductor L3 need to be placed in the next stage (damping sub-circuit) is that: the functions of the two are in a circuit, interference signals are restrained and filtered in a filtering mode, and for high-power interference, the position of a filtering device is possibly damaged too far forward, so that the whole circuit operation is influenced while the function is lost. Similarly, the capacitor C3 and the capacitor C4 suitable for the fourth-stage protection circuit (common-mode filtering sub-circuit) are placed at the end of the circuit, and the filter devices are arranged at the rear stage as much as possible, so that the protection effect and the common-mode/differential-mode interference suppression effect of the protection circuit are optimal.
The third stage of protection, i.e. the damping sub-circuit, is mainly composed of L3, and the capacitor C2 is connected with the two poles of the common mode inductor L3.
The fourth-stage protection, namely the common-mode filtering sub-circuit, is mainly composed of capacitors C3 and C4, is led out from two output pins of a common-mode inductor L3, is connected in series with two Y capacitors C3 and C4, and the middle grounding PE of the capacitors C3 and C4 is subjected to protection and filtering processing of the whole protection circuit, so that most of EFT and Surge interference can be consumed or filtered, and a very reliable protection effect is achieved on a rear-stage working circuit.
The embodiment of the utility model provides a in the selection of components and parts, consider because the voltage of weak current power supply port is 24V of direct current, in order to keep certain design allowance, carry out derating design, select voltage dependent resistor Z1, Z2, Z3 of withstand voltage 47V, consider the harmfulness of leakage current to the user, according to the requirement of the state to ann's rule electric capacity, the leakage current peak value can not exceed 0.7mA, so the electric capacity value can not exceed 4.7nF the most.
In the embodiment of the utility model, electric capacity C1, C2, C3, C4 select for use 2.2nF, and 1000V are selected to withstand voltage.
The embodiment of the utility model provides an in, the clamping voltage of the TVS pipe D1, D2, D3 of chooseing for use can not be less than the normal range upper limit value of input power, can not be higher than the biggest tolerance limit of back-stage element. The embodiment of the utility model provides a maximum reverse peak current of the TVS pipe of chooseing for use is 30A, and maximum clamping voltage is 49.9V.
The embodiment of the utility model provides an in, inductance L1, L2 that choose for use are 22 uH's differential mode inductance, rated current 1.7A, and inductance L3 is common mode inductance, will choose for use the low common mode inductance of differential mode impedance, rated operating voltage 80V, rated current 5A, and direct current resistance only is 10m omega, can satisfy the design demand.
The utility model discloses in the implementation, play the guard action to common mode interference, mainly realized by piezo-resistor Z1, Z3, TVS pipe D1, D2, inductance L3 and electric capacity C3, C4. When common mode interference enters a circuit through a power supply port, the primary protection of the circuit is firstly realized, the transient high voltage of the interference can make the piezoresistor Z1/Z3 break down at first, the impedance of the piezoresistors Z1 and Z3 is very low at the moment, most of overvoltage can be discharged to the ground PE, but the primary protection at the moment is not enough to discharge all interference to the ground, therefore, two TVS tubes D1 and D2 are added in the secondary protection for absorbing residual voltage which is not completely discharged after the piezoresistors Z1 and Z3 are broken down, on the basis of the first two-stage protection, a common-mode inductor L3 is added in the third-stage protection, because of the isotropy of the current of the common-mode interference, an equidirectional magnetic field is generated in the coil of the inductor to increase the inductive impedance of the coil, the coil is high-impedance, and has a strong damping effect, so that the common-mode interference current is suppressed, and the purpose of filtering is achieved.
And finally, the fourth-stage protection is utilized, namely the common-mode interference is filtered to the ground PE through the filtering of the two Y capacitors C3 and C4 of the common-mode filtering sub-circuit, and through the protection of the multi-stage circuit, the common-mode interference can be well consumed and filtered, so that the rear-stage working circuit is not influenced.
The embodiment of the utility model provides an in, to the guard action of differential mode interference, mainly by piezo-resistor Z2, electric capacity C1, inductance L1, L2, TVS pipe D3, electric capacity C2, the circuit realization that inductance L3 constitutes. When differential mode interference enters a port of a power supply, firstly, the differential mode interference passes through a piezoresistor Z2 of primary protection, the transient high voltage of the interference can enable a piezoresistor Z2 to be directly broken down, at the moment, Z2 impedance suddenly drops, the current flowing through the piezoresistor Z2 suddenly rises, the energy of the differential mode interference is consumed by the internal resistance of the piezoresistor Z2 in a large current mode, and then pi-type filtering processing is carried out, wherein a capacitor C1 and a capacitor C2 are used as an X capacitor and matched with two differential mode inductors L1 and L2 to filter the differential mode interference in a filtering mode, in addition, a TVS tube D3 of secondary protection can be instantly conducted when the common mode interference comes, the voltage is clamped at a preset position to absorb the residual voltage of the previous stage, and finally, the leakage inductance of the common mode inductor L3 has an effective effect on the suppression of the differential mode interference.
In traditional circuit, can not jointly use piezo-resistor and TVS pipe, because the response speed of TVS pipe will be faster than piezo-resistor far away, under more circumstances, common mode/differential mode interference is held voltage clamp by the TVS pipe, and piezo-resistor can not exert it and should absorptive effect, to this kind of circumstances, the utility model discloses a fine solution this problem among the circuit design. Firstly, the TVS tubes D1, D2 and D3 must be placed at the rear stage of the differential mode inductors L1 and L2, because the currents of the differential mode inductors L1 and L2 cannot change suddenly, the time of the interference reaching the TVS tubes can be delayed, especially the response speed of the transient high-voltage TVS tubes is faster than that of the piezoresistors, if the inductors L1 and L2 are not designed at the front ends of the TVS tubes, when the transient high voltage of the interference enters the circuit, the transient high voltage cannot respond to the piezoresistors in the first stage of protection, the TVS tubes at the rear stage are firstly conducted, and at this time, the first stage of protection is disabled, and the protection effect cannot be achieved. Meanwhile, the two differential mode inductors are matched with the two X capacitors to form a pi-type filter circuit, so that the current of the circuit can be smoothed while the normal response of the piezoresistor and the TVS tube is ensured, and the clamping of the TVS tube is more accurate.
The position of the TVS tube D3 needs to be placed before the C2 as much as possible, because the protection and filtering rules of the circuit need to realize protection first and filtering later, otherwise, on the premise of not making protection, advanced filtering is realized, once a rear-stage circuit is damaged by common mode/differential mode interference, the filtering device of the front stage loses significance, and is easy to damage, the protection effect cannot be achieved, and the design initiatives of the protection circuit cannot be met.
The protection circuit of the weak current power supply port provided by the embodiment of the invention can be applied to a lightning protection device and can also be applied to various electronic equipment using a secondary power supply as a backup power supply, wherein the electronic equipment comprises but is not limited to a wireless communication base station, a microwave communication ground station, a satellite communication ground station and the like.
Carry out EFT, Surge protection to weak current power supply port, under the prerequisite that does not deviate from the protection circuit design thought of this application, can also evolve out multiple protection circuit, can reach the technological effect of this embodiment equally, all should regard as belonging to the utility model discloses protection circuit's patent protection scope.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.
Claims (9)
1. A protection circuit of a weak current power supply port is characterized by comprising a high-voltage protection sub-circuit, a filtering delay sub-circuit, a residual voltage absorption sub-circuit and a damping sub-circuit which are sequentially connected;
one end of the high-voltage protection sub-circuit is connected with a weak current power supply port, and the other end of the high-voltage protection sub-circuit is connected with the filtering delay sub-circuit and is used for performing high-voltage protection on the weak current power supply port;
the filtering delay sub-circuit utilizes the self-generated delay function to enable the high-voltage protection sub-circuit to generate response before the residual voltage absorption sub-circuit;
the residual voltage absorption sub-circuit is used for absorbing residual voltage which is not completely discharged after the piezoresistor in the high-voltage protection sub-circuit is broken down;
the damping sub-circuit is used for increasing the inductive reactance of the inductance coil, generating a damping effect and inhibiting common-mode interference current.
2. The protection circuit for a weak current power port of claim 1, further comprising after the damping sub-circuit:
and the common-mode filtering sub-circuit is used for consuming and filtering the common-mode interference through the filtering action.
3. The protection circuit for the weak current power port of claim 1, wherein the connection mode of the high voltage protection sub-circuit and the weak current power port is as follows:
one end of the piezoresistor Z1 is connected with the anode of the direct-current power supply, and the other end is grounded PE; one end of the piezoresistor Z2 is connected with the positive pole of the direct-current power supply, and the other end is connected with 0V ground; one end of the piezoresistor Z3 is connected to 0V ground, and the other end is connected to ground PE.
4. A protection circuit for a weak current power port according to claim 1 or 3, wherein the filtering delay sub-circuit is connected to the high voltage protection sub-circuit in a manner that: the capacitor C1 is connected across the two ends of the rear stage of the piezoresistor Z2, the input pin of the inductor L1 is connected with one end of the capacitor C1, and the input pin of the inductor L2 is connected with the other end of the capacitor C1.
5. The protection circuit of a weak current power port according to claim 1, wherein the residual voltage absorption sub-circuit is connected with the filtering delay sub-circuit in a manner that:
the two poles of the TVS tube D3 are bridged between the two output pins of the inductor L1 and the inductor L2, the TVS tube D1 and the TVS tube D2 are respectively led out from the two pins of the TVS tube D3 and connected to the ground PE, and the two poles of the capacitor C2 are connected with the two ends of the rear stage of the TVS tube D3.
6. The weak current power port protection circuit of claim 1, wherein said damping sub-circuit is connected to said filtering delay sub-circuit in a manner that:
the capacitor C2 is connected to the two input pins of a common mode inductor L3.
7. The protection circuit for a weak current power port according to claim 1, wherein the common mode filtering sub-circuit is connected to the damping sub-circuit in a manner that:
and the capacitors C3 and C4 are connected in series from two output pins of the common-mode inductor L3, and the middle of the capacitors C3 and C4 is grounded by PE.
8. A lightning protection device using the weak current power supply port protection circuit of any one of claims 1 to 7.
9. An electronic device using the weak current power supply port protection circuit of any one of claims 1 to 7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021579924.9U CN213151905U (en) | 2020-08-03 | 2020-08-03 | Protection circuit, lightning protection device and electronic equipment of weak current power supply port |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202021579924.9U CN213151905U (en) | 2020-08-03 | 2020-08-03 | Protection circuit, lightning protection device and electronic equipment of weak current power supply port |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN213151905U true CN213151905U (en) | 2021-05-07 |
Family
ID=75735804
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202021579924.9U Active CN213151905U (en) | 2020-08-03 | 2020-08-03 | Protection circuit, lightning protection device and electronic equipment of weak current power supply port |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN213151905U (en) |
-
2020
- 2020-08-03 CN CN202021579924.9U patent/CN213151905U/en active Active
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN204089181U (en) | A kind of lightning surge protection circuit and LED drive power | |
| CN103515942B (en) | The protection circuit of communication interface | |
| CN103795045B (en) | Protection device | |
| CN106093494A (en) | A kind of signal for electronic mutual inductor protects filter circuit | |
| CN109546634B (en) | Composite broadband filter circuit with surge voltage resistance | |
| CN106505842A (en) | Airborne DC source | |
| CN211908364U (en) | Multistage lightning surge protection circuit for direct-current power supply of product in power industry | |
| CN205753380U (en) | The protection circuit of lightning surge | |
| CN203339687U (en) | High speed and high frequency signal port surge protection circuit | |
| CN215344365U (en) | Power supply protection circuit and industrial flowmeter | |
| CN213151905U (en) | Protection circuit, lightning protection device and electronic equipment of weak current power supply port | |
| JP2011155759A (en) | Surge energy transfer circuit | |
| CN208623329U (en) | One kind having the compatible immunity to interference mould group of lightning protection EMC multifunction electromagnetic | |
| CN106026627A (en) | Method for improving surge immunity of switching power supply | |
| CN112039325A (en) | Protection circuit of weak current power supply port and protection method thereof | |
| CN203233162U (en) | Surge protection device | |
| CN213637073U (en) | Lightning surge protection circuit for navigation mark equipment | |
| CN213093862U (en) | Direct current power supply lightning protection circuit | |
| CN110011290B (en) | Ethernet interface anti-surge circuit | |
| CN211405467U (en) | Electric power direct current signal acquisition return circuit protection circuit | |
| CN204333949U (en) | A kind of protection against lightning surge circuit for navigation mark equipment | |
| CN1581627A (en) | Protective circuit | |
| CN210041323U (en) | Lightning surge protection circuit of elevator door motor | |
| CN208820468U (en) | A kind of Spark gap device applied to 806MHZ~2500MHZ radiofrequency signal | |
| CN207368658U (en) | PLC product 6KV surging protection circuits |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant | ||
| GR01 | Patent grant |