CN108181501B - Current signal acquisition circuit with protective action - Google Patents
Current signal acquisition circuit with protective action Download PDFInfo
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- CN108181501B CN108181501B CN201810060944.6A CN201810060944A CN108181501B CN 108181501 B CN108181501 B CN 108181501B CN 201810060944 A CN201810060944 A CN 201810060944A CN 108181501 B CN108181501 B CN 108181501B
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- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
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- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
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Abstract
The invention discloses a current signal acquisition circuit with a protection function, which comprises a signal acquisition circuit, a signal processing circuit and a control circuit, wherein the signal acquisition circuit comprises a power module, a sensor connected with the power module and a signal processing circuit connected with the sensor; the first current detection circuit monitors the output current state condition of the power supply circuit of the sensor in the signal acquisition circuit and outputs an overcurrent state signal; and the second current detection circuit monitors the circuit current state condition in the signal conditioning circuit in the current signal acquisition circuit and outputs an overcurrent state signal. The current signal acquisition circuit with the protection function solves the problem that internal devices are damaged when a power supply is short-circuited to the ground or the power supply is short-circuited to a signal input port while realizing the acquisition of sensor signals, and greatly widens the selection range and flexibility of internal amplifiers and analog switch devices.
Description
Technical Field
The invention relates to a signal acquisition circuit, in particular to a current signal acquisition circuit with a protection function.
Background
At present, most of sensors are developed to a two-wire system, only two wires are needed, and signals are transmitted in 4-20 mA current, so that the sensor has the advantages of simple connection, long transmission distance, strong crosstalk inhibition capability, safety, explosion prevention and the like. One of the two-wire sensor is connected with a 24v power module, and the other wire outputs current within the range of 4-20 mA. The conventional two-wire sensor current output signal acquisition circuit is simple in structure, as shown in fig. 1, a power supply module (PMS) supplies power to a sensor, the power supply of the power supply module is usually 24v, and the power supply module can be realized by a power supply module management system such as a low dropout regulator (LDO), a direct current converter (DCDC) or an alternating current-direct current converter (ACDC). The current signal output by the sensor is converted into a voltage signal after passing through a resistor R1, and after being processed by a buffer operational amplifier (OP), the voltage signal is sampled and amplitude-quantized by an analog-to-digital converter (ADC). Since most ADCs are currently low voltage operation devices that can only operate at 5v or below, the voltage drop across R1 may not exceed 5v in order to achieve 20ma corresponding ADC full scale, i.e., the resistance of R1 is typically less than or equal to 250 Ω. Wherein P0 and P1 are PTC thermistors which can limit the flowing current. D0 and D1 are transient voltage suppressing diode (TVS) transistors that can absorb the energy of electrostatic discharge (ESD) or surge. However, in a specific application process, some practical circuit protection problems are also faced. For example, due to misoperation, the 24v power supply module is directly connected to the current input port I1, which may cause internal low voltage devices, such as an operational amplifier (OP), to be damaged due to overvoltage. If the operational amplifier (OP) selects a device which is resistant to high voltage, the selection range of the operational amplifier is necessarily greatly limited. Meanwhile, when such voltage abnormality occurs, corresponding fault indication is lacked in the circuit, and if the problem is not found quickly, the PTC thermistors P0 and P1 continuously flow large current, so that continuous heating is caused, and the stability and reliability of the system are affected. In addition, as shown in fig. 2, in an implementation structure of the multi-channel current signal acquisition system, it is almost difficult to find a suitable high-voltage-resistant analog switching device.
In summary, in the conventional current signal collecting circuit, when a high voltage is suddenly applied to the circuit, there is no indication of circuit abnormality in the circuit, and the circuit does not process the abnormality, and protects the components in the circuit, and further improvement is urgently needed.
Disclosure of Invention
The invention aims to provide a current signal acquisition circuit with a protection function, which is used for solving the defects that the existing current signal acquisition circuit lacks of circuit abnormity prompt and cannot protect components in the circuit.
In order to achieve the above object, the present invention provides a current signal collecting circuit with protection function, the circuit comprising:
the signal acquisition circuit comprises a power module, a sensor connected with the power module and a signal conditioning circuit connected with the sensor;
the first current detection circuit monitors the output current state condition of the sensor power supply circuit in the signal acquisition circuit and outputs an overcurrent state signal;
the second current detection circuit monitors the current state condition of the circuit in the signal conditioning circuit and outputs an overcurrent state signal;
and the overcurrent protection circuit is used for controlling the disconnection and delayed closing of the sensor power supply circuit according to the overcurrent state signal output by the first current detection circuit or the second current detection circuit.
In an embodiment of the invention, the sensor power supply circuit is further connected with a switch circuit, the switch circuit comprises a mos tube, a gate of the mos tube is respectively connected with one end of a resistor R1 and one end of a resistor R2, the other end of the resistor R2 is connected with an output end of the overcurrent protection circuit, and the other end of the resistor R1 is connected with the power supply module;
the drain electrode of the mos tube is connected with the sensor;
and the source electrode of the mos tube is connected with the power supply module.
In one embodiment of the present invention, the drain of the mos transistor is connected to one end of the first PTC thermistor, and the other end of the first PTC thermistor is connected to the first TVS transistor and the sensor, respectively.
In an embodiment of the present invention, the first current detection circuit includes a first current amplifier and a resistor R0, the resistor R0 is connected in series to the sensor power supply circuit, a positive input terminal of the current amplifier is connected to one end of the resistor R0, a negative input terminal of the current amplifier is connected to the other end of the resistor R0, and an output terminal of the current amplifier is connected to the overcurrent protection circuit.
In an embodiment of the present invention, the second current detection circuit includes a second current amplifier and a resistor R3 connected to the conditioning circuit, a positive input terminal of the second current amplifier is connected to one end of the resistor R3, a negative input terminal of the second current amplifier is connected to the other end of the resistor R3, and an output terminal of the second current amplifier is connected to the overcurrent protection circuit.
In an embodiment of the invention, the overcurrent protection circuit comprises a first voltage comparator, a second voltage comparator, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a capacitor C1 and a 555 chip;
the input end of the first voltage comparator is connected with the first current detection circuit, and the output end of the first voltage comparator is connected with the TRIG end of the 555 chip through the R4 resistor;
the input end of the second voltage comparator is connected with the second current detection circuit, and the output end of the second voltage comparator is connected with the TRIG end through the R5 resistor;
the power supply module is connected with the TRIG end through the R6 resistor;
the power supply module is connected with a Dis end and a THR end of a 555 chip and one end of the capacitor C1 through the R7 resistor, and the other end of the capacitor C1 is grounded;
and the Q end of the 555 chip outputs a control signal to control the disconnection and delayed closing of the sensor power supply circuit.
In an embodiment of the present invention, the overcurrent protection circuit further includes an abnormality prompt circuit, the abnormality prompt circuit includes a resistor R8 and a light emitting diode D1, the Q terminal of the 555 chip is connected to the anode of the light emitting diode D1 through the resistor R8, and the cathode of the light emitting diode D1 is grounded.
In one embodiment of the invention, the signal conditioning circuit comprises a current-voltage conversion circuit, an operational amplifier and an analog-digital converter;
the current-voltage conversion circuit comprises a second TVS tube, a third TVS tube, a PTC thermistor, a resistor R10, a first diode and a second diode, wherein the input end of the current-voltage conversion circuit is respectively connected with one end of the second TVS tube and one end of the second PTC thermistor, the other end of the second PTC thermistor is respectively connected with one end of the third TVS tube and one end of the R10 resistor, the other end of the R10 is grounded, the positive end of the first diode and the negative end of the second diode are connected, and the negative end of the first diode is connected with the input end of the second current detection circuit;
the output end of the current-voltage conversion circuit is connected with the input end of the operational amplifier, and the output end of the operational amplifier is connected with the input end of the analog-to-digital converter.
The invention has the following advantages:
the current signal acquisition circuit with the protection function can be used for perfectly solving the problem that internal devices are possibly damaged when a power supply is short-circuited to the ground or the power supply is short-circuited to a signal input port while realizing the acquisition of the sensor signal, thereby greatly widening the selection range and flexibility of internal amplifiers and analog switch devices. When the fault occurs, the abnormity prompting circuit can give corresponding prompt in time.
Drawings
Fig. 1 is a schematic diagram of a conventional current signal acquisition circuit.
Fig. 2 is a schematic circuit diagram of a conventional multi-channel current signal acquisition system.
Fig. 3 is a circuit diagram of the current signal acquisition circuit with protection function according to the present invention.
Fig. 4 is a schematic diagram of a current signal acquisition circuit with protection according to an embodiment of the present invention.
Detailed Description
The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
As shown in fig. 3 and 4, the present invention provides a current signal acquisition circuit with protection function, which comprises a signal acquisition circuit, wherein the signal acquisition circuit comprises a power module 50, a sensor SD1 connected to the power module 50, and a signal conditioning circuit 40 connected to the sensor SD 1; a first current detection circuit 10 for monitoring the output current state of the power supply circuit of the sensor in the current signal acquisition circuit and outputting an overcurrent state signal; a second current detection circuit 20 for monitoring the current state of the circuit in the signal conditioning circuit 40 and outputting an overcurrent state signal; and the overcurrent protection circuit 30 is used for controlling the disconnection and delayed closing of the power supply circuit of the sensor SD1 according to the overcurrent state signal output by the first current detection circuit 10 or the second current detection circuit 20. The current signal acquisition circuit with the protection function can perfectly solve the problem that devices in the circuit are damaged when a power supply module is short-circuited to the ground or the power supply module is short-circuited to a signal input port while realizing the acquisition of a sensor signal, an amplifier, an analog switch device and the like in the circuit can also adopt low-voltage devices, so that the selection range and the flexibility are greatly expanded, and corresponding prompts can be given in time when the faults occur.
The sensor power supply circuit is further connected with a switch circuit 60, the switch circuit 60 comprises a mos tube M0, the grid of the mos tube M0 is connected with one end of a resistor R1 and one end of a resistor R2, the other end of the resistor R2 is connected with an output signal end ctr of the overcurrent protection circuit, and the other end of the resistor R1 is connected with the power module 50; the drain electrode of the mos tube M0 is connected with a sensor SD 1; the source of mos transistor M0 is connected to power module 50. The drain of the mos transistor M0 is connected to one end of the first PTC thermistor P0, and the other end of the first PTC thermistor P0 is connected to the first TVS transistor D0 and the sensor SD1, respectively.
Specifically, the first current detection circuit 10 includes a first current amplifier CC1 and a resistor R0, the resistor R0 is connected in series to the power supply circuit of the sensor SD1, the positive input terminal of the first current amplifier CC1 is connected to one end of a resistor R0, the negative input terminal of the first current amplifier CC1 is connected to the other end of the resistor R0, and the output terminal of the first current amplifier CC1 is connected to the overcurrent protection circuit 30. The second current detection circuit 20 includes a second current amplifier CC2 and a resistor R3 connected to the signal conditioning circuit 40, a positive input terminal of the second current amplifier CC2 is connected to one end of the resistor R3, a negative input terminal is connected to the other end of the resistor R3, and an output terminal of the second current amplifier CC2 is connected to the overcurrent protection circuit 30.
The overcurrent protection circuit 30 comprises a first voltage comparator CM1, a second voltage comparator CM2, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a capacitor C1 and a 555 chip; the input end of a first voltage comparator CM1 is connected with the output end of the first current detection circuit 10, and the output end of the first voltage comparator CM1 is connected with the TRIG end of the 555 chip through a resistor R4; the input end of a second voltage comparator CM2 is connected with the output end of the second current detection circuit, and the output end of the second voltage comparator CM2 is connected with the TRIG end through an R5 resistor; the power supply module is connected with the TRIG end through the R6 resistor; the power supply module is connected with the Dis end and the THR end of the 555 chip and one end of a capacitor C1 through an R7 resistor, and the other end of the capacitor C1 is grounded; and the Q end of the 555 chip outputs a control signal to control the disconnection and delayed closing of the power supply circuit of the sensor. The overcurrent protection circuit 31 further includes an abnormality prompt circuit, which includes a resistor R8 and a light emitting diode D1, the Q terminal of the 555 chip is connected with the anode of the light emitting diode D1 through a resistor R8, and the cathode of the light emitting diode is grounded.
The signal conditioning circuit 40 includes a current-voltage conversion circuit 41, an operational amplifier OP, and an analog-to-digital converter ADC; the current-voltage conversion circuit 41 comprises a second TVS tube D10, a third TVS tube D11, a second PTC thermistor P1, a resistor R10, a first diode D12 and a second diode D13, the input end of the current-voltage conversion circuit 41 is respectively connected with one end of a second TVS tube D10 and one end of a second PTC thermistor P1, the other end of the second PTC thermistor P1 is respectively connected with one end of a third TVS tube D11 and one end of a resistor R10, the other end of the resistor R10 is grounded, the positive end of the first diode D12 and the negative end of the second diode D13 are connected, and the negative end of the first diode D12 is connected with the input end of the second current detection circuit; the output end of the current-voltage conversion circuit 41 is connected to the input end of an operational amplifier OP, an analog switch S1 is further provided between the current-voltage conversion circuit 41 and the operational amplifier OP, and the output end of the operational amplifier OP is connected to the input end of an analog-to-digital converter ADC.
As shown in fig. 3, by connecting a first current detection circuit 10 to the circuit PV that supplies power to the sensor SD1 and a second current detection circuit 20 to the signal conditioning circuit PI, the currents on both paths are monitored by the first current detection circuit 10 and the second current detection circuit 20. When the abnormal current exceeding condition occurs on the power supply circuit of the sensor SD1 and the signal conditioning circuit 40, the overcurrent protection circuit intermittently cuts off the power supply circuit of the sensor through the control switch S0, so that the power supply module PMS does not always output excessive current, when the input end of the signal conditioning circuit 40 is short-circuited to the power supply end, the diode D1 absorbs the excessive current, the current also flows through the thermistor P1, when the threshold current of the thermistor P1 is reached, the thermistor P1 enables the current flowing through the P1 to hardly change along with the increase of the voltage difference between the two ends, namely the resistor P1 increases along with the increase of the voltage difference between the two ends. The combination of the thermistor P1 and the diode D1 clamps the resistor R1 at its one end to a maximum of about V1+ 0.7V. V1 can be set in the voltage range of low voltage device (OP, analog switch S) power module, and the components in the circuit will not be damaged when the power module is short-circuited. Meanwhile, the overcurrent protection circuit monitors the current state condition, gives an abnormal prompt of the overcurrent state signal through an acousto-optic signal, and timely prompts a user to remove abnormal settings. When the abnormal condition is removed, the over-current protection circuit 30 automatically controls the switch S0 to re-turn on the sensor power path.
As shown in fig. 4, a channel-CH 1 signal conditioning circuit is taken as an example to illustrate the working mechanism of the current signal collecting circuit with protection function of the present invention, when the signal collecting circuit works normally, the power input of the two-wire sensor SD1 is connected to the power module PMS VDD1, the output of the two-wire sensor SD1 is connected to the input I1 of the signal conditioning circuit 40, the two-wire sensor SD1 outputs a standard 4-20 mA current C, and the current C flows into the ground after passing through the second PTC thermistor P1 and the resistor R10. When the switch S1 is closed, the voltage signal V is buffered by the operational amplifier OP (or amplified and filtered appropriately), and then sent to the analog-to-digital converter ADC for sampling and amplitude quantization, the digitized information can be further processed and stored in a system such as a single chip microcomputer or a computer, and the signal acquisition function is completed by the CH1 signal conditioning circuit. Similarly, when S2 is closed, the sensor signal on channel two CH2 is collected, and so on. In the acquisition circuit of the invention, D10 and D11 are used as devices for absorbing surge and ESD energy and do not play a role in normal operation, and when abnormal operation occurs, such as VDD1 is directly connected to the input end I1 of the signal conditioning circuit, the voltage at one end of a resistor R10 is more than VDD2+ 0.7. The current C1 'flowing through the input path is much larger than 20mA, and the current C2' exceeding 20mA flows through the second PTC thermistor P1, the first diode D12 and the voltage difference across the second PTC thermistor P1 increases with the increase of the current. The potential of one end of the combined clamping resistor R10 of the second PTC thermistor P1 and the first diode D12 does not exceed the voltage-resistant range of the switch S1 and the operational amplifier OP, so that the combined clamping resistor is not threatened by damage. After the current C2 'flows through the resistor R3, the voltage difference VR3 ═ C2' × R3 across the resistor R3. The second current amplifier CC2 processes the amplified voltage VR3 signal and sends it to a second voltage comparator CM2 for comparison with a reference voltage Vref 2. When the current C2' is larger than a certain value, such as 100mA, the voltage VR3 will invert the output signal of the second voltage comparator CM2 when it is set to exceed the reference voltage Vref 2. R6 and R4, R5 constitute line and function, when arbitrary CM1 or CM2 takes place the upset, the TRIG end of 555 chip all can receive the upset signal, and the 555 chip accomplishes timing function, and after the TRIG received the upset signal, Q end signal Ctr changed along with, the M0 of control switch circuit 60 disconnected, the power supply circuit VDD1 disconnection and the power module PMS of giving sensor SD 1. After a set delay, the Q-terminal signal Ctr is inverted, the M0 of the control switch circuit 60 is closed, the power supply VDD1 for the sensor SD1 is connected to the power module PMS, and the delay is set by the value of R7 × C1. Through the timing function of the 555 chip, whether the short circuit abnormality is removed or not can be detected at any time, when the short circuit abnormality is not removed, the VDD1 keeps supplying power discontinuously, the overcurrent currents on the first PTC thermistor P0 and the second PTC thermistor P1 do not exist continuously, and the situation of continuous heating does not exist in the circuit. When the circuit is removed abnormally, the 555 chip controls the switch circuit to be closed, the continuous power supply is automatically recovered, and the stability of the whole circuit system is greatly optimized. The Ctr signal output by the Q end of the 555 chip can also be used as an alarm prompt signal, and the bright light prompt is realized by lighting the LED D1. Similarly, when VDD1 is shorted to I1 or to ground, an excessive current C3' will flow through the first PTC thermistor P0 and the resistor R0, and the first PTC thermistor P0 will immediately limit the output current of the power module PMS, thereby avoiding the damage of the PMS due to overheating caused by overcurrent. C3' is detected by a first current amplifier CC1, when the voltage exceeds a set threshold value, for example, 500mA, a first voltage comparator CM1 overturns, and due to the line and function formed by resistors R6, R4 and R5, a signal at the TRIG end of a 555 chip overturns, and a Ctr alarm control signal is also given to control a switch circuit 60 to disconnect M0, so that a path from a power module PMS to VDD1 is disconnected, and overcurrent protection of the circuit is realized.
Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.
Claims (3)
1. A current signal acquisition circuit with protection, the circuit comprising:
the signal acquisition circuit comprises a power module, a sensor connected with the power module and a signal conditioning circuit connected with the sensor;
the first current detection circuit monitors the output current state condition of the power supply circuit of the sensor in the signal acquisition circuit and outputs an overcurrent state signal;
the second current detection circuit monitors the current state condition of the circuit in the signal conditioning circuit and outputs an overcurrent state signal;
the overcurrent protection circuit is used for controlling the disconnection and delayed closing of the sensor power supply circuit according to an overcurrent state signal output by the first current detection circuit or the second current detection circuit;
the sensor power supply circuit is also connected with a switch circuit, the switch circuit comprises a mos tube, the grid of the mos tube is respectively connected with one end of an R1 resistor and one end of an R2 resistor, the other end of an R2 resistor is connected with the output end of the overcurrent protection circuit, and the other end of an R1 resistor is connected with the power supply module;
the drain electrode of the mos tube is connected with the sensor;
the source electrode of the mos tube is connected with the power supply module;
the drain electrode of the mos tube is connected with one end of the first PTC thermistor, and the other end of the first PTC thermistor is respectively connected with the first TVS tube and the sensor;
the first current detection circuit comprises a first current amplifier and a resistor R0, the resistor R0 is connected in series with the sensor power supply circuit, the positive input end of the current amplifier is connected with one end of the resistor R0, the negative input end of the current amplifier is connected with the other end of the resistor R0, and the output end of the current amplifier is connected with the overcurrent protection circuit;
the second current detection circuit comprises a second current amplifier and a resistor R3 connected with the conditioning circuit, wherein the positive input end of the second current amplifier is connected with one end of a resistor R3, the negative input end of the second current amplifier is connected with the other end of a resistor R3, and the output end of the second current amplifier is connected with the overcurrent protection circuit;
the signal conditioning circuit comprises a current and voltage conversion circuit, an operational amplifier and an analog-to-digital converter;
the current-voltage conversion circuit comprises a second TVS tube, a third TVS tube, a PTC thermistor, a resistor R10, a first diode and a second diode, wherein the input end of the current-voltage conversion circuit is respectively connected with one end of the second TVS tube and one end of the second PTC thermistor, the other end of the second PTC thermistor is respectively connected with one end of the third TVS tube and one end of the R10 resistor, the other end of the R10 is grounded, the positive end of the first diode and the negative end of the second diode are connected, and the negative end of the first diode is connected with the input end of the second current detection circuit;
the output end of the current-voltage conversion circuit is connected with the input end of the operational amplifier, and the output end of the operational amplifier is connected with the input end of the analog-to-digital converter.
2. The current signal collection circuit with protection according to claim 1,
the overcurrent protection circuit comprises a first voltage comparator, a second voltage comparator, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a capacitor C1 and a 555 chip;
the input end of the first voltage comparator is connected with the first current detection circuit, and the output end of the first voltage comparator is connected with the TRIG end of the 555 chip through the R4 resistor;
the input end of the second voltage comparator is connected with the second current detection circuit, and the output end of the second voltage comparator is connected with the TRIG end through the R5 resistor;
the power supply module is connected with the TRIG end through the R6 resistor;
the power supply module is connected with a Dis end and a THR end of a 555 chip and one end of the capacitor C1 through the R7 resistor, and the other end of the capacitor C1 is grounded;
and the Q end of the 555 chip outputs a control signal to control the disconnection and delayed closing of the sensor power supply circuit.
3. The current signal collection circuit with protection according to claim 2,
the overcurrent protection circuit further comprises an abnormality prompt circuit, the abnormality prompt circuit comprises a resistor R8 and a light-emitting diode D1, the Q end of the 555 chip is connected with the anode of the light-emitting diode D1 through the resistor R8, and the cathode of the light-emitting diode D1 is grounded.
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| CN109085417A (en) * | 2018-08-16 | 2018-12-25 | 珠海英搏尔电气股份有限公司 | The current detection circuit and electric machine controller of direct measuring type Hall sensor |
| CN111551797A (en) * | 2020-04-17 | 2020-08-18 | 中国兵器工业火炸药工程与安全技术研究院 | Online electrostatic charge quantity measuring device suitable for energetic material |
| CN112485507B (en) * | 2020-11-18 | 2022-09-30 | 北京时代民芯科技有限公司 | Method for testing transmission current of daisy chain communication circuit |
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