CN221124697U - Sampling circuit with overvoltage and overcurrent protection, sampling device and control system thereof - Google Patents
Sampling circuit with overvoltage and overcurrent protection, sampling device and control system thereof Download PDFInfo
- Publication number
- CN221124697U CN221124697U CN202322440762.0U CN202322440762U CN221124697U CN 221124697 U CN221124697 U CN 221124697U CN 202322440762 U CN202322440762 U CN 202322440762U CN 221124697 U CN221124697 U CN 221124697U
- Authority
- CN
- China
- Prior art keywords
- resistor
- sampling
- sampling circuit
- circuit
- overvoltage
- 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
- 238000005070 sampling Methods 0.000 title claims abstract description 109
- 238000006243 chemical reaction Methods 0.000 claims abstract description 8
- 230000009467 reduction Effects 0.000 claims description 3
- 230000002427 irreversible effect Effects 0.000 abstract 1
- 238000000034 method Methods 0.000 description 4
- 230000002159 abnormal effect Effects 0.000 description 3
- 238000013461 design Methods 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000010438 heat treatment Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000011084 recovery Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000012938 design process Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000013024 troubleshooting Methods 0.000 description 1
Abstract
The utility model discloses a sampling circuit with overvoltage and overcurrent protection, a device and a control system thereof, comprising: comprising the following steps: sampling resistor and sampling circuit protection unit, sampling circuit protection unit's one end is connected with the voltage positive pole input of waiting the sampling circuit, conversion circuit's voltage positive pole output respectively, sampling circuit protection unit with sampling resistor parallel connection, just sampling circuit protection unit's the other end is connected with the voltage negative pole input of waiting the sampling circuit, conversion circuit's voltage negative pole output respectively, has realized that the circuit can not receive irreversible damage sampling circuit under the condition of misconnection DC 24V, realizes the overvoltage overcurrent protection function of circuit.
Description
Technical Field
The present utility model relates to the field of sampling circuits, and in particular, to a sampling circuit, device and control system thereof with overvoltage and overcurrent protection.
Background
In industrial control systems such as DCS or PLC, a 250 ohm precision resistor is usually selected for detecting a current signal. In the design process of the product, in order to meet the requirement that the full-range measurement precision is not lower than 0.2% within the range of the working environment temperature of-40 ℃ to +50 ℃, the precise resistor with the temperature drift of 10ppm is generally selected for current sampling.
The high-power resistor has large resistance value change caused by temperature drift when in operation, and influences measurement accuracy, so that the low-temperature drift resistor generally has smaller power. For example, the temperature drift of 2512 packaged chip resistor is 10ppm, the maximum power can only be 0.75W, and the maximum power of 50ppm can be 1W.
There are many signals in industrial control systems such as DCS or PLC, for example, switching value input, switching value output, and the signal amplitude is DC 24V. In the engineering application process, faults such as wire connection fault, damage of a measuring instrument and the like often occur, and the port for accessing the current signal is accessed with DC 24V, so that the current sampling module is burnt. Therefore, users generally require the current signal measuring module or unit to have overvoltage and overcurrent protection functions.
Disclosure of utility model
The utility model aims to provide a sampling circuit and a sampling device with overvoltage and overcurrent protection, which realize that the sampling circuit is not irreversibly damaged under the condition of misconnection of DC 24V, and realize the overvoltage and overcurrent protection function of the circuit.
The utility model provides a sampling circuit with overvoltage and overcurrent protection, which comprises: the sampling circuit protection unit is connected with the sampling resistor in parallel, and the other end of the sampling circuit protection unit is connected with the voltage negative electrode input end of the circuit to be sampled and the voltage negative electrode output end of the conversion circuit.
Preferably, the sampling circuit protection unit comprises a MOSFET tube, a first resistor and a second resistor, wherein the drain electrode of the MOSFET tube is connected with one end of the sampling resistor, the other end of the sampling resistor is sequentially connected with one end of the first resistor and one end of the second resistor, the grid electrode of the MOSFET tube is connected with one end of the first resistor, and the source electrode of the MOSFET tube is connected with one end of the first resistor to limit the current flowing through the sampling resistor to play a role of protection.
Preferably, the sampling circuit protection unit includes a zener diode, a third resistor and a fourth resistor, one end of the third resistor is connected in series with one end of the fourth resistor, the other end of the fourth resistor is connected with a cathode of the zener diode, an anode of the zener diode is connected with one end of the sampling resistor, the other end of the sampling resistor is connected with the cathode of the zener diode, and the anode of the zener diode and one end of the sampling resistor are connected with a voltage cathode input end of the circuit to be sampled and a voltage cathode output end of the conversion circuit so as to achieve a protection effect through voltage division, so that voltage reduction on the sampling resistor plays a role in protecting.
Preferably, the first resistor and the second resistor are both 49.9Ω, and rated power is 0.75W.
Preferably, the sampling resistor is 49.9 Ω and the rated power is 0.75W.
Preferably, the zener diode voltage is 4.7V.
Preferably, the sampling circuit is used for detecting a current signal of 0-20 mA or 4-20 mA.
The utility model provides a sampling device with overvoltage and overcurrent protection, which comprises a sampling circuit with overvoltage and overcurrent protection according to the embodiment of the utility model.
The utility model provides a control system, which comprises a sampling circuit with overvoltage and overcurrent protection according to the embodiment of the utility model.
Aiming at the prior art, the utility model has the following beneficial effects:
The utility model provides a self-elevating high-side control switch circuit scheme applicable to an ultra-wide voltage range, and has no special wide voltage requirement on components. The voltage of the device is the difference value obtained by subtracting the voltage value of the load power supply from the true value obtained by AC-DC coupling, so that the limitations of the working conditions such as complicated control mode in a high-side control scheme, narrow power supply of the device in a bootstrap circuit and the like are broken through, the control method is suitable for solving the high-side switch control scheme of a wider load power supply, and the control mode is simpler.
Drawings
Fig. 1-2 are schematic diagrams of one to two exemplary sampling circuits with overvoltage and overcurrent protection according to embodiments of the present utility model.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present utility model more apparent, the technical solutions of the embodiments of the present utility model will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present utility model, and it is apparent that the described embodiments are some embodiments of the present utility model, but not all embodiments of the present utility model. All other embodiments, which can be made by those skilled in the art based on the embodiments of the utility model without making any inventive effort, are intended to be within the scope of the utility model.
The utility model provides a sampling circuit with overvoltage and overcurrent protection, which comprises the following design steps:
S1: configuring the amplitude of an input/output signal; there are many signals in industrial control systems such as DCS or PLC, for example, switching value input, switching value output, and the signal amplitude is DC 24V. In the engineering application process, faults such as wire connection fault, damage of a measuring instrument and the like often occur, and the port for accessing the current signal is accessed with DC 24V, so that the current sampling module is burnt. The damage of the module not only brings economic loss, but also causes construction period delay and even production accidents due to lack of spare parts. In order to prevent the circuit from being irreversibly damaged under the condition of misconnection with DC 24V, the sampling circuit is firstly modified so that the sampling resistor is not burnt out when the sampling circuit misconnects with external DC 24V. The modified sampling circuit needs to satisfy: the input impedance of the sampling circuit is not excessive, and in the case that the loading capacity of the signal source of the signal to be tested cannot be determined, the excessive input impedance may cause test result errors.
S2: under the condition that abnormal conditions occur in the preset direct-current voltage access, replacing a target device in a sampling circuit to sample current; the preset direct current voltage is 4V direct current voltage, the abnormal condition comprises that the port connected with the current signal is connected with 24V direct current voltage, and the port connected with the current signal is connected with DC 24V, so that the current sampling module is burnt, and the heating value is that
S3: comparing the maximum voltage value which can be accessed by the sampling circuit formed by the target device with a preset direct-current voltage threshold value, and performing overvoltage and overcurrent protection on the sampling circuit under the condition that an abnormal condition occurs when the maximum voltage value which can be accessed by the sampling circuit formed by the target device is larger than the preset direct-current voltage threshold value. The target device may be a precision resistor, MOSFET tube, zener diode, etc.
In one embodiment, 5 pieces 2512 are selected to package a precision resistor with rated power of 0.75W, resistance value of 49.9 omega and temperature drift of 10ppm when designing a current sampling module or unit of a control system such as a DCS or a PLC; meanwhile, a self-recovery fuse with the withstand voltage of 60V and the rated current of 0.05A is connected, so that the purpose of over-current and over-voltage protection can be achieved. 24V is added to 5 precise resistors with the temperature of 49.9 omega, and the heating value of each resistor isLess than the rated power of the resistor, the resistor will not burn out.
Those skilled in the art will appreciate that 1, using 5 2512 packages for current sampling with a precision resistor of 49.9 Ω, the maximum accessible voltage is: that is, even if the DC voltage of 30.59V is connected in error, the current sampling module or unit is not damaged in any performance, and the problem that the current sampling equipment is damaged due to the fact that the DC 24V is connected in error can be perfectly solved.
In another embodiment, the 2, 2512 package has a 49.9 Ω precision resistor rating of 0.75W and is not damaged by 122mA current. The voltage withstand is 60V, the rated current of the self-recovery fuse with the rated current of 0.05A is 74 mA-40.5 mA within the range of-40 ℃ to +50 ℃ in the working environment temperature, and the current sampling can be effectively protected from damage caused by overcurrent.
The sampling circuit with overvoltage and overcurrent protection provided by the utility model realizes the design method of the sampling circuit with overvoltage and overcurrent protection, which is used for detecting a current signal of 0-20 mA or 4-20 mA.
Referring to fig. 1, one end of the sampling circuit sampling resistor and the sampling circuit protection unit 1 is respectively connected with a voltage positive input end of a circuit to be sampled and a voltage positive output end of a conversion circuit, the sampling circuit protection unit 1 is connected with the sampling resistor in parallel, and the other end of the sampling circuit protection unit 1 is respectively connected with a voltage negative input end of the circuit to be sampled and a voltage negative output end of the conversion circuit.
In an embodiment, the sampling circuit protection unit 1 includes a MOSFET tube, a first resistor and a second resistor, a source electrode of the MOSFET tube is connected with a voltage positive input end, a drain electrode of the MOSFET tube is connected with one end of the sampling resistor, the other end of the sampling resistor is connected with a voltage positive output end, the other end of the sampling resistor is sequentially connected with one end of the first resistor and one end of the second resistor, a gate electrode of the MOSFET tube is connected with one end of the first resistor, a source electrode of the MOSFET tube is connected with one end of the first resistor, and the other end of the second resistor is connected with a voltage negative input end and an output end respectively to limit current flowing through the sampling resistor to play a role of protection. The main principle is as follows: the added depletion type MOSFET plays a role of constant current, and limits the current flowing through the sampling resistor, so that the purpose of preventing the sampling resistor from being burnt is achieved. The first resistor and the second resistor adopted in this example are both 49.9Ω, and the rated power is 0.75W. The sampling resistor used in this embodiment is 39Ω.
In another embodiment, as shown in fig. 2, the sampling circuit protection unit 1 includes a zener diode, a third resistor and a fourth resistor, one end of the third resistor is connected with the voltage positive input end, the other end of the third resistor is connected with one end of the fourth resistor in series, the other end of the fourth resistor is connected with the voltage positive output end, the other end of the fourth resistor is connected with the cathode of the zener diode, the anode of the zener diode is connected with one end of the sampling resistor, the other end of the sampling resistor is connected with the voltage negative output end, and the anode of the zener diode is connected with the voltage negative input end to achieve a protection effect through voltage division, so that the voltage reduction on the sampling resistor plays a role in protecting. The main principle is as follows: by dividing the voltage, the voltage across the sampling resistor is reduced. Through calculation, under the condition of misconnection with DC 24V, the power of the sampling resistor is about 0.24W, and the resistor cannot be burnt out at the moment, so that the protection purpose is achieved. And the zener diode connected in parallel with the sampling resistor has the zener voltage of 4.7V, so that the protection effect can be achieved. The sampling resistor used in this example is 49.9Ω, the rated power is 0.75W, the third resistor and the fourth resistor are both 100deg.Ω, and the zener diode voltage is 4.7V.
The circuit of the scheme II does not use a MOSFET, a voltage stabilizing diode is added, the circuit is simpler, the cost is lower, and meanwhile, the troubleshooting difficulty of component faults is reduced, so that the circuit of the scheme II has more advantages in design.
The utility model also provides a sampling device with overvoltage and overcurrent protection, which comprises the sampling circuit with overvoltage and overcurrent protection according to the embodiment of the utility model.
The utility model also provides a control system which comprises the sampling circuit with overvoltage and overcurrent protection according to the embodiment of the utility model.
The functional principle of the present utility model is as described in the above embodiments of the present utility model, and will not be described herein. Parts of the apparatus, device or system embodiments that are not described in detail refer to descriptions of relevant parts of the circuit embodiments.
Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present utility model, and are not limiting; although the utility model has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present utility model.
Claims (9)
1. A sampling circuit with overvoltage and overcurrent protection, comprising: the sampling circuit protection unit is connected with the sampling resistor in parallel, and the other end of the sampling circuit protection unit is connected with the voltage negative electrode input end of the circuit to be sampled and the voltage negative electrode output end of the conversion circuit.
2. The sampling circuit with overvoltage and overcurrent protection according to claim 1, wherein the sampling circuit protection unit comprises a MOSFET tube, a first resistor and a second resistor, the drain electrode of the MOSFET tube is connected with one end of the sampling resistor, the other end of the sampling resistor is sequentially connected with one end of the first resistor and one end of the second resistor, the grid electrode of the MOSFET tube is connected with one end of the first resistor, and the source electrode of the MOSFET tube is connected with one end of the first resistor to limit current flowing through the sampling resistor to play a role of protection.
3. The sampling circuit with overvoltage and overcurrent protection according to claim 1, wherein the sampling circuit protection unit comprises a zener diode, a third resistor and a fourth resistor, one end of the third resistor is connected with one end of the fourth resistor in series, the other end of the fourth resistor is connected with a cathode of the zener diode, an anode of the zener diode is connected with one end of the sampling resistor, the other end of the sampling resistor is connected with the cathode of the zener diode, and the anode of the zener diode and one end of the sampling resistor are connected with a voltage cathode input end of the circuit to be sampled and a voltage cathode output end of the conversion circuit so that voltage reduction on the sampling resistor plays a role in protection through voltage division.
4. A sampling circuit with overvoltage and overcurrent protection according to claim 2 wherein the first resistor and the second resistor are both 49.9 Ω and rated at 0.75W.
5. A sampling circuit with overvoltage and overcurrent protection according to claim 3 wherein the sampling resistor is 49.9 Ω and rated at 0.75W.
6. A sampling circuit with overvoltage and overcurrent protection according to claim 3 wherein the zener diode voltage is 4.7V.
7. A sampling circuit with overvoltage and overcurrent protection according to claim 1, wherein the sampling circuit is configured to detect a 0-20 mA or 4-20 mA current signal.
8. A sampling device with overvoltage and overcurrent protection, characterized in that the device comprises a sampling circuit with overvoltage and overcurrent protection according to any one of claims 1 to 7.
9. A control system of a sampling circuit with overvoltage and overcurrent protection, characterized in that the control system comprises a sampling circuit with overvoltage and overcurrent protection according to any one of claims 1 to 7.
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN221124697U true CN221124697U (en) | 2024-06-11 |
Family
ID=
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| FI99222C (en) | Semiconductor surge protection circuit | |
| US9042067B2 (en) | Battery tester | |
| CN201417941Y (en) | Interface protection circuit | |
| CN106058837B (en) | A kind of leakage conductor leak current detection device of no isolating device | |
| CN103618286A (en) | Transient over-voltage protection circuit | |
| CN202939292U (en) | Direct-current power supply monitoring circuit | |
| CN221124697U (en) | Sampling circuit with overvoltage and overcurrent protection, sampling device and control system thereof | |
| CN207992860U (en) | Digital output circuit and industrial control equipment | |
| CN201708537U (en) | Straight-through protective circuit for bridge arm of converter | |
| CN205160033U (en) | M -Bus bus protector with from recovery function | |
| AU2019100844A4 (en) | An overvoltage optoelectronic isolation protection device based on short circuit test | |
| CN203191443U (en) | Lightning arrester leakage current on-line monitoring device | |
| CN102510056B (en) | High-precision signal source output overvoltage protection circuit | |
| CN209948658U (en) | On-line automatic detection intelligent tripping switching device for communication power supply SPD | |
| CN103487736B (en) | A kind of method and device detecting TVS pipe | |
| CN108733122B (en) | Digital output circuit and industrial control equipment | |
| US20170194787A1 (en) | Redundant solution of outputs on a rc voltage divider | |
| JP6996420B2 (en) | Semiconductor device test method | |
| CN207623395U (en) | A kind of divider of ontology and second divided voltage plate Phototube Coupling | |
| CN201788242U (en) | Protection test device of USB equipment | |
| CN217282213U (en) | Voltage limiting protection circuit | |
| CN205123687U (en) | Power protection circuit | |
| CN220985364U (en) | Charging protection circuit and electronic equipment | |
| CN220358808U (en) | Overvoltage and undervoltage protection circuit | |
| CN205122785U (en) | GNSS terminal active antenna current foldback circuit |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| GR01 | Patent grant |