CN212459812U - Multi-range high-precision high-voltage isolation transmitter - Google Patents
Multi-range high-precision high-voltage isolation transmitter Download PDFInfo
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- CN212459812U CN212459812U CN202021013147.1U CN202021013147U CN212459812U CN 212459812 U CN212459812 U CN 212459812U CN 202021013147 U CN202021013147 U CN 202021013147U CN 212459812 U CN212459812 U CN 212459812U
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Abstract
The utility model discloses a changer is kept apart to multirange high accuracy high voltage, this device include multirange selection circuit, MCU control circuit, programme-controlled high voltage input circuit, programmable resistance array, PWM closed-loop control circuit, high isolation coupling mutual-inductor, PWM demodulation circuit, linear integrator circuit, voltage/current conversion circuit. The rough adjustment of the gain correction of the device is realized by controlling the program control amplifier through the MCU control circuit. The rough adjustment of the zero offset correction of the device is realized by the MCU control circuit to the programmable resistor array. The correction and the adjustment of the gain and the zero point offset of the device are realized by controlling a PWM closed-loop control circuit power supply. The device adopts MCU control technology and PWM technology to carry out signal conversion, and obtains required multi-range high-precision high-voltage isolation transmission signals by accurately adjusting the duty ratio of PWM pulses.
Description
Technical Field
The utility model relates to a changer, in particular to changer is kept apart to multirange high accuracy high voltage.
Background
A transducer is a transducer that converts the output signal of a sensor into a signal that can be recognized by a controller (or a signal source that converts the non-electrical quantity input by the sensor into an electrical signal while amplifying it for remote measurement and control). The sensor and the transmitter together form a monitoring signal for automatic control. Different physical quantities require different sensors and corresponding transmitters. The types of transmitters are various, and the transmitters used on the industrial control instrument mainly comprise a temperature transmitter, a pressure transmitter, a flow transmitter, a current transmitter, a voltage transmitter and the like.
The voltage transducer is an instrument which can convert the tested AC and DC voltage into AC and DC current or voltage which is output according to linear proportion. And the corresponding indicating instrument or device is matched, so that the measurement and control of voltage and current can be realized in alternating current and direct current circuits of the power system.
With the innovative development of scientific technology, a higher voltage driving mode is adopted for optimizing energy in modern high-power industrial equipment such as rail transit, industrial control, power grids, aerospace, new energy and the like. The monitoring of these high-power high-voltage systems is mainly to ensure the safety of people and equipment, and there are high common-mode voltage signals in these high-power equipment. The detection of these signals requires the use of highly reliable, high precision, high voltage isolation transmitters.
In a rail transit high-voltage traction system, the wide input range of a voltage signal of a high-voltage isolation transmitter is as follows: unipolar or bipolar voltage of +/-60 mV to +/-3600V is isolated by high voltage and then output and converted into +/-20 mA, 4-20 mA and +/-10V standard current and voltage range.
At present, a high-voltage isolation transmitter used in a rail transit high-voltage traction system has the following defects:
1. the high-voltage isolation transmitter can only measure high voltage with fixed range and cannot meet the multi-range test detection requirements of various application occasions;
2. the gain calibration and the zero offset calibration of the high-voltage isolation transmitter are realized by manually adjusting the fine-tuning element. For example, the adjustable potentiometer is adjusted, and due to the characteristics of the material structure performance of the potentiometer, the problems of potential jump along with a vibration environment, potential drift along with temperature, large noise and the like exist.
SUMMERY OF THE UTILITY MODEL
The utility model discloses a high voltage isolation changer performance to using in present power electronics high voltage measurement field has the high voltage to keep apart the changer and can only measure fixed range high voltage, can't satisfy multiple application scenario's multirange test detection demand, provides a multirange high accuracy high voltage isolation changer device.
The technical scheme adopted by the device is as follows: a multi-range high-precision high-voltage isolation transmitter comprises a high-voltage input circuit, a resistor array, a PWM (pulse-width modulation) closed-loop control circuit, an isolation coupling mutual inductor, a PWM demodulation circuit and a linear integration circuit; the input high-voltage signal to be detected attenuates the high-voltage signal into a low-voltage small signal which can be identified by a controller through a high-voltage input circuit, adjusts the zero offset of the signal through a resistor array, sends the signal into a PWM closed-loop control circuit to be converted into a PWM signal, and sends the PWM signal to a PWM demodulation circuit and a linear integration circuit to be converted into a voltage amplitude signal after being isolated by an isolation coupling mutual inductor; the multi-range selection circuit and the MCU control circuit are also included; the high-voltage input circuit and the resistor array are respectively a program-controlled high-voltage input circuit and a programmable resistor array controlled by the MCU control circuit;
the multi-range selection circuit is connected with the MCU control circuit;
the device also comprises a coarse adjustment module for gain calibration, a coarse adjustment module for zero offset calibration and a fine adjustment module for gain and zero offset calibration;
the coarse adjustment module for gain calibration consists of the MCU control circuit and a program control amplifier in the program control high-voltage input circuit; the coarse tuning module for zero offset calibration consists of an MCU control circuit and a programmable resistor array; the gain calibration and zero offset calibration fine tuning module MCU control circuit is composed of a working power supply of a PWM closed-loop control circuit.
Further, in the above-mentioned multi-range high accuracy high voltage isolation transmitter: the gain and zero offset calibration fine tuning module comprises: a first integrating circuit consisting of a resistor R12 and a capacitor C11 and a second integrating circuit consisting of a resistor R15 and a capacitor C12; a first follower consisting of an operational amplifier U11A and a resistor R11 and a second follower consisting of an operational amplifier U11B and a resistor R14;
the MCU control circuit outputs PWM1 with adjustable duty ratio, the PWM1 is integrated by the first integrating circuit and then is output by the first follower to be connected with a power supply VCC +;
the MCU control circuit outputs PWM2 with adjustable duty ratio, the PWM2 is integrated by a second integrating circuit and then is output by a second follower to be connected with a power supply VCC-.
Further, in the above-mentioned multi-range high accuracy high voltage isolation transmitter: the PWM closed-loop control circuit comprises a square wave oscillation circuit, a triangular wave circuit, an integral comparison circuit and a modulation signal output circuit;
the square wave oscillation circuit comprises a Schmitt inverter U2A, a Schmitt inverter U2D, a resistor R4 and a capacitor C2; the output end of the Schmitt inverter U2A is connected with the input end of the Schmitt inverter U2D; the resistor R4 is arranged between the input end and the output end of the Schmitt inverter U2A, one end of the capacitor C2 is connected with the input end of the Schmitt inverter U2A, and the other end of the capacitor C2 is connected with the output end of the Schmitt inverter U2D;
the triangular wave circuit comprises a resistor R3 and a capacitor C3; the square wave output by the square wave oscillation circuit is connected with one end of a resistor R3, and the other end of the resistor R3 is grounded through a capacitor C3; the common end of the resistor R3 connected with the capacitor C3 forms an output end S2 of the triangular wave;
the integral comparison circuit comprises an operational amplifier U1, a Schmitt inverter U2F, a capacitor C1, a resistor R1, a resistor R2, a capacitor C4 and a resistor R5; the output end S2 of the triangular wave is connected with the input end of a Schmitt inverter U2F, the output end of the Schmitt inverter U2F is connected with one end of a resistor R5, and the 14 pin and the 7 pin of the Schmitt inverter U2F are respectively connected with a power supply VCC + and VCC-; the other end of the resistor R5 is grounded through a capacitor C4; an input signal VIN is connected and superposed with a common end connected with a resistor R5 and a capacitor C4 after being limited by a resistor R1, and then is connected with an out-phase end of an operational amplifier, and the in-phase end of the operational amplifier is connected with an input end ground level VF; the capacitor C1 is arranged between the out-phase end and the output end of the operational amplifier U1, and the output end of the operational amplifier U1 is connected with the end of the resistor R3 connected with the capacitor C3 through the resistor R2;
the PWM modulation signal output circuit comprises a Schmitt inverter U2B, a Schmitt inverter U2C and a capacitor C5; the input end of the Schmitt inverter U2B is connected with the input end of the Schmitt inverter U2C; the output end of the Schmitt inverter U2B and the output end of the Schmitt inverter U2C are connected with each other; the resistor R2 is connected with the common end of the resistor R3 connected with the capacitor C3 and is respectively connected with the input ends of the Schmitt inverter U2B and the Schmitt inverter U2C, the output ends of the Schmitt inverter U2B and the Schmitt inverter U2C are connected with one end of the capacitor C5, and the other end of the capacitor C5 forms the output S4 of the PWM closed-loop control circuit.
Further, in the above-mentioned multi-range high accuracy high voltage isolation transmitter: the high isolation coupling mutual inductor is a PCB embedded high isolation coupling mutual inductor.
The utility model also provides a calibration method of multirange high accuracy high voltage isolation changer, MCU control circuit confirms gain and zero offset of current gear according to range selection circuit, calibrates according to gain and zero offset of current gear, and the calibration mode divide into gain calibration coarse adjustment, zero offset calibration coarse adjustment, gain and zero offset fine adjustment;
and a step of coarse gain calibration: in the step, the gain resistance ratio of the program control amplifier is adjusted to realize coarse gain calibration adjustment;
and a step of calibrating coarse adjustment of zero offset: in the step, the coarse adjustment of zero offset calibration is realized by adjusting the resistance ratio of the programmable resistance array;
and fine adjustment of gain and zero offset: in the step, the power supply voltage VCC + and VCC-of the PWM closed-loop control circuit U2 is accurately adjusted by adjusting the power supply VCC + and VCC-precision fine tuning circuit, so that the fine tuning of gain and zero offset is realized.
Further, in the calibration method of the multi-range high-precision high-voltage isolation transmitter, the following steps are performed: the gain and zero point offset fine adjustment steps are as follows:
the single chip microcomputer generates two paths of PWM1 and PWM2 duty ratio adjustable pulses, the pulses are converted into single chip microcomputer adjustable direct current potentials through two paths of linear integration circuits, and then the pulses are connected through an operational amplifier U11, and the change of VCC + and VCC-direct current voltage of a pulse oscillation circuit power supply in a PWM closed loop circuit is achieved.
The utility model discloses a processor circuit of intelligence adjusts the multirange test that satisfies multiple application scenario a little to gain calibration and zero offset thickness and gain and zero offset and detects the demand.
The present invention will be further described with reference to the accompanying drawings and the detailed description.
Drawings
FIG. 1 is a block diagram of the apparatus.
Fig. 2 is a circuit schematic of the gain and zero offset trimming module.
Fig. 3 is a circuit schematic diagram corresponding to the PWM closed-loop control circuit portion.
Fig. 4 is a block diagram of a calibration process of the present apparatus.
Detailed Description
The present embodiment is a multi-range high-precision high-voltage isolation transmitter device as shown in fig. 1, and includes a multi-range selection circuit, an MCU control circuit, a program-controlled high-voltage input circuit, a programmable resistor array, a PWM (pulse width modulation) closed-loop control circuit, a high-isolation coupling transformer, a PWM demodulation circuit, a linear integration circuit, and a voltage/current conversion circuit, where the program-controlled high-voltage input circuit includes a high-voltage attenuation circuit and a program-controlled amplifier.
The MCU control circuit of the device determines the current input/output range of the device according to the range selection circuit, an input high-voltage signal passes through the program-controlled high-voltage input circuit, is attenuated by the high-voltage attenuation circuit to be a low-voltage small signal which can be processed by the program-controlled amplifier, and is adjusted to be a signal with proper voltage amplitude by adjusting the gain of the program-controlled amplifier. The signal is adjusted to zero offset by the programmable resistor array, sent to the PWM closed-loop control circuit to be converted into a pulse signal with a finely adjustable duty ratio, and sent to the high isolation coupling mutual inductor for isolation. The voltage amplitude signal is converted into a voltage amplitude signal through a PWM demodulation circuit and a linear integration circuit and is output through a voltage/current conversion circuit.
In the embodiment, the voltage transducer has a plurality of measuring ranges, and each step of gain calibration and zero offset calibration are composed of coarse tuning calibration and fine tuning calibration.
The MCU control circuit controls a program control amplifier in the program control high-voltage input circuit to realize coarse adjustment of gain correction, and the MCU control circuit controls a programmable resistance array to realize coarse adjustment of zero offset correction. The MCU control circuit outputs two paths of PWM1 and PWM2 signals with adjustable duty ratio, the two paths of signals are converted into a single-chip microcomputer adjustable direct current potential through two paths of linear integration circuits, and after the two paths of signals are amplified through an operational amplifier U11, the power supply VCC + and VCC-of the PWM closed-loop control circuit are controlled, the voltage change of the power supply is realized, and therefore the gain and the fine adjustment of zero offset of the device are realized. From the analysis of fig. 3, it can be seen that: the duty ratio of the output signal of the PWM wave closed-loop modulation circuit is only related to the power supply voltage VCC +, VCC-of the PWM wave closed-loop modulation circuit, the input signal VIN and the reference level VF of the signal input end, the reference level VF is provided by a precise voltage stabilizing source, and the duty ratio regulation precision of the output pulse of the circuit is only determined by the regulation precision of VCC + and VCC-.
In this embodiment, the coarse tuning of the gain is performed by adjusting the ratio of the gain resistance of the programmable control amplifier through the MCU control circuit, so as to perform coarse tuning on the gain calibration. The rough adjustment of the zero offset calibration is to adjust the resistance ratio of the program control resistor array through the MCU control circuit, so as to carry out rough adjustment on the zero offset of the device. In the embodiment, the adjustment of the gain calibration and the zero offset calibration is realized by outputting two paths of pulses with adjustable duty ratios of PWM1 and PWM2 through the MCU control circuit, converting the two paths of pulses into adjustable direct current potentials of a single chip microcomputer through two paths of linear integration circuits, and controlling power supplies VCC + and VCC-of the PWM closed-loop control circuit after the two paths of pulses are amplified by the operational amplifier U11. This change in voltage can fine tune the gain and zero offset of the transmitter of this embodiment. The MCU control circuit outputs two paths of PWM signals: PWM1 and PWM2 pulses, the frequency is set to be 2KHz, and the minimum adjustment resolution of the pulse duty ratio is 0.01 percent. VCC + and VCC-are regulated in the same step and direction, the duty ratio of the output pulse of the PWM closed-loop control circuit is adjusted to 50%, and the zero offset of the embodiment is finely adjusted. VCC + and VCC-are adjusted in the same step and different directions, and the gain of the device is finely adjusted.
In this embodiment, the fine tuning of the gain calibration and the zero offset calibration is implemented by the MCU control circuit by controlling VCC + and VCC-in the PWM closed-loop control circuit as shown in fig. 2.
The PWM closed-loop control circuit comprises a PWM closed-loop control circuit, a power supply VCC + and VCC-voltage precision fine tuning circuit;
the PWM closed-loop control circuit comprises a square wave oscillation circuit, a triangular wave circuit, an integral comparison circuit and a pulse width modulation signal output circuit;
the power VCC + and VCC-precision fine tuning module comprises: the MCU control circuit outputs 2 paths of adjustable PWM signals, the signals are sent to the 2 paths of integrating circuits, and the signals are converted into 2 paths of direct current voltages adjustable by the single chip microcomputer after being processed by the two paths of operational amplifiers U11. This voltage precisely regulates the supply voltage VCC +, VCC-of the PWM closed loop control circuit U2.
As shown in fig. 2, the power VCC + and VCC-precision trimming module includes two paths of integrating circuits composed of a resistor R12, a capacitor C11, a resistor R15, and a capacitor C12, and two paths of follower circuits composed of operational amplifiers U11A, R11, an operational amplifier U11B, and a resistor R14.
An integrating circuit consisting of a resistor R12 and a capacitor C11; the MCU control circuit outputs two paths of PWM1 with adjustable duty ratio, the two paths of PWM1 are connected with one end of a capacitor C11 through a resistor R12, the other end of the capacitor C11 is grounded, and the other end of the resistor R13 is also connected with a pin 3 of the operational amplifier U11A.
And the MCU control circuit outputs two paths of PWM2 with adjustable duty ratio, the PWM2 is connected with one end of a capacitor C12 and one end of a resistor R16 through a resistor R15, the other end of the capacitor C12 is grounded, and the other end of the resistor R16 is connected with a pin 5 of an operational amplifier U11.
The operational amplifiers U11A and R11, the operational amplifier U11B and the resistor R14 form a two-way follower circuit, wherein one way is that the pin 1 of the operational amplifier U11A is connected with one end of the resistor R11, and the other end of the R11 is connected with the pin 2 of the operational amplifier and is output to VCC + of the PWM closed-loop control circuit; in the other path, the pin 7 of the operational amplifier U11 is connected with one end of the resistor R14, and the other end of the R14 is connected with the pin 6 of the operational amplifier and is output to VCC-of the PWM closed-loop control circuit.
The square wave oscillation circuit is shown in fig. 3 and comprises a schmitt inverter U2A, a schmitt inverter U2D, a resistor R4 and a capacitor C2; the output end of the Schmitt inverter U2A is connected with the input end of the Schmitt inverter U2D; the resistor R4 is disposed between the input terminal and the output terminal of the schmitt inverter U2A, one terminal of the capacitor C2 is connected to the input terminal of the schmitt inverter U2A, and the other terminal of the capacitor C2 is connected to the output terminal of the schmitt inverter U2D.
The triangular wave circuit comprises a resistor R3 and a capacitor C3; the square wave output by the square wave oscillation circuit is connected with one end of a resistor R3, and the other end of the resistor R3 is grounded through a capacitor C3; the common end of the resistor R3 connected with the capacitor C3 forms an output end S2 of the triangular wave;
the integral comparison circuit comprises an operational amplifier U1, a Schmitt inverter U2F, a capacitor C1, a resistor R1, a resistor R2, a capacitor C4 and a resistor R5; the output end S2 of the triangular wave is connected with the input end of a Schmitt inverter U2F, the output end of the Schmitt inverter U2F is connected with one end of a resistor R5, and the 14 pin and the 7 pin of the Schmitt inverter U2F are respectively connected with a power supply VCC + and VCC-; the other end of the resistor R5 is grounded through a capacitor C4; an input signal VIN is connected and superposed with a common end connected with a resistor R5 and a capacitor C4 after being limited by a resistor R1, and then is connected with an out-phase end of an operational amplifier, and the in-phase end of the operational amplifier is connected with the ground level VREF of an input end; the capacitor C1 is arranged between the out-phase end and the output end of the operational amplifier U1, and the output end of the operational amplifier U1 is connected with the end of the resistor R3 connected with the capacitor C3 through the resistor R2;
the PWM modulation signal output circuit comprises a Schmitt inverter U2B, a Schmitt inverter U2C and a capacitor C5; the input end of the Schmitt inverter U2B is connected with the input end of the Schmitt inverter U2C; the output end of the Schmitt inverter U2B and the output end of the Schmitt inverter U2C are connected with each other; the resistor R2 is connected with the common end of the resistor R3 connected with the capacitor C3 and is respectively connected with the input ends of the Schmitt inverter U2B and the Schmitt inverter U2C, the output ends of the Schmitt inverter U2B and the Schmitt inverter U2C are connected with one end of the capacitor C5, and the other end of the capacitor C5 forms the output S4 of the PWM closed-loop control circuit.
The accuracy of the supply voltage VCC +, VCC-regulation depends on the oscillation frequency and frequency accuracy of the MCU circuit crystal oscillator. The MCU regulates the intermediate value of the voltage difference between VCC + and VCC-to be equal to VF through the accurate regulation of the PWM pulse width output by the I/O port of the MCU, and the duty ratio of the PWM wave is 50%. The zero point offset of the output signal of the device is ensured. Therefore, the circuit has higher measurement accuracy, the change of the parameters of the components is fed back by the circuit in a closed loop in real time, and the influence of the change of the parameters of the components on the measurement accuracy is very small.
In this embodiment, the step amplitude of the coarse tuning calibration of the gain and the zero point is smaller than 1%, so that the adjustment of the coarse tuning calibration precision is controlled within 1%, and the step amplitude of the fine tuning calibration of the gain and the zero point is smaller than 0.01%, so that the precision of the gain calibration and the zero point calibration is controlled within 0.01%.
The high isolation coupling transformer is embedded in the PCB, the PCB density can be improved by designing and integrating the high isolation coupling transformer in the PCB, the size of the transformer is reduced, and the electrical parameters can be accurately controlled. A primary coil and a secondary coil of the high-isolation coupling mutual inductor embedded in the PCB are self-resonant coils with the same resonant frequency and the turn ratio of 1: 1. And designing a double-layer snail-shaped spiral coil. The multi-layer PCB technology is adopted, simulation calculation is convenient to carry out, and the self-resonant frequency of the coil is accurate and stable by adjusting the size of the coil, the number of turns, the distance between the wires, the width and the thickness of the coil, the thickness of the substrate and other parameters. The grounding shielding layer in the PCB embedded high-isolation coupling mutual inductor can effectively inhibit the interference of radiation noise to a circuit, and the PCB high-insulation substrate enables the isolation voltage between the primary coil and the secondary coil of the PCB embedded high-isolation coupling mutual inductor to be larger than 20 kV.
A high-isolation coupling mutual inductor embedded in a PCB in the electromagnetic isolation type PWM circuit transmits a pulse duty ratio signal, and the transmission precision is hardly influenced by leakage inductance.
In the embodiment, the gain calibration and the zero offset calibration of various high-voltage input/output ranges are completed through the adjustment of software, and the input/output range is switched by selecting a multi-gear coding switch. The calibration process is as shown in fig. 4, and the initialization of the parameters is performed after the MCU is powered on. After initialization, the serial port is configured and opened, and the MCU continuously reads the serial port command. When the serial port receives a gain calibration coarse adjustment command, the MCU reads data received by the serial port and controls a program control amplifier of the program control high-voltage input circuit to perform corresponding adjustment; when the serial port receives a zero calibration coarse adjustment command, the MCU reads data received by the serial port and controls the programmable resistance array to perform corresponding adjustment; when the serial port receives the gain calibration fine adjustment command, the MCU reads the data received by the serial port and controls the PWM1 and the PWM2 to adjust in the same step and opposite directions; when the serial port receives a zero calibration fine adjustment command, the MCU reads data received by the serial port and controls the PWM1 and the PWM2 to adjust in the same step and the same direction; when the serial port receives the correction completion instruction, the MCU stores the corrected data and closes the serial port, and after the serial port is closed, the coding switch is enabled, the change of the coding switch is continuously detected, and corresponding configuration data is called.
Because the device is the combination of various high-voltage input/output ranges, the multi-gear input/output ranges need to be respectively corrected during correction. For example: when the multi-range selection circuit is 16 ranges, the 16-range coding switch can be selected to control the input/output range. When the first gear is corrected, the coding switch is dialed to the number 0000 position. The input voltage of the device is set to be 0V, so that the device is in a zero input state, and the output of the device is zero offset. And testing the output voltage of the device by using a high-precision voltmeter, and if the error of the output voltage of the device is more than 1%, performing coarse zero offset correction. After the serial port receives the zero offset correction coarse adjustment command, the MCU reads data received by the serial port and controls the programmable resistance array to carry out corresponding zero offset correction adjustment until the zero offset error is less than or equal to 1%. And after coarse adjustment, if the zero offset error of the device is less than or equal to 1% and more than or equal to 0.01%, performing zero offset correction fine adjustment. After the serial port receives the zero offset correction fine adjustment command, the MCU reads the data received by the serial port and controls the PWM1 and the PWM2 to adjust in the same step and the same direction until the zero offset error is less than 0.01 percent. And if the zero offset error is less than 0.01%, completing the zero offset correction.
And after the zero offset correction is finished, performing coarse gain correction. We set the input voltage of the device to the maximum input voltage of the gear. The serial port receives a gain correction coarse adjustment command, and the MCU reads data received by the serial port and controls a program control amplifier of the program control high-voltage input circuit to perform corresponding adjustment until a gain correction error is less than or equal to 1%. After the gain rough adjustment, if the gain error of the transmitter is less than or equal to 1% and more than or equal to 0.01%, gain correction fine adjustment is carried out. The serial port receives the gain correction fine adjustment command, the MCU reads the data received by the serial port and controls the PWM1 and the PWM2 to adjust in the same stepping direction and opposite directions until the gain error is less than 0.01 percent. And if the gain error is less than 0.01%, the gain correction is finished. At which point the gear correction is complete.
At this time, the coding switch digital code is switched to 0001, and second gear correction is carried out. The zero offset correction method is similar to the first gear, when the gain error is corrected, the input voltage of the transmitter is set to be the maximum input voltage of the second gear, and the correction method is similar to the first gear. And the other gear calibration is analogized in turn until all 16 gears are corrected. After the correction is completed, a correction completion command is sent to the MCU through the serial port, the MCU stores the corrected data and closes the serial port, and after the serial port is closed, the coding switch is enabled, the change of the coding switch is continuously detected, and corresponding configuration data is called.
The present embodiment can achieve the following main performance indicators:
input range: unipolar or bipolar voltages of + -60 mV to + -3600V,
outputting a measuring range: standard current of +/-20 mA, 4-20 mA and +/-10V and voltage range.
And (3) zero offset: less than 0.05 percent
Gain error: less than 0.05 percent
Isolation voltage: 20KV (input to output and input to power supply)
EMC (EN 61326) radiation interferes with class B immunity industry class.
In the embodiment, a multi-range high-precision high-voltage test is realized by adopting an MCU control technology and an electromagnetic isolation PWM technology. The defect of high-voltage isolation transmitters in the existing rail transit traction system is overcome. The multi-range high-precision high-voltage signal monitoring requirement of various application occasions is met.
In the embodiment, the correction of various high-voltage input/output ranges is completed through the adjustment of software, and a multi-gear coding switch is selected to switch the input/output ranges;
when the first gear is corrected, the coding switch is dialed to a number 0000 position; setting the input voltage of the device to be 0V, and enabling the device to be in a zero input state; testing the output voltage of the device through a high-precision voltmeter, and if the error of the output voltage of the device is larger than 1%, performing coarse zero offset correction; after the serial port receives the zero offset correction coarse adjustment command, the MCU reads data received by the serial port and controls the programmable resistance array to carry out corresponding zero offset correction adjustment until the zero offset error is less than or equal to 1%; after coarse adjustment, if the zero offset error of the device is less than or equal to 1% and more than or equal to 0.01%, performing zero offset correction fine adjustment; after the serial port receives the zero offset correction fine adjustment command, the MCU reads the data received by the serial port and controls the PWM1 and the PWM2 to carry out adjustment with the same step and the same direction until the zero offset error is less than 0.01 percent; and if the zero offset error is less than 0.01%, completing the zero offset correction.
After the zero offset correction is finished, performing coarse gain correction; setting the input voltage of the device as the maximum input voltage of the gear; the serial port receives a gain correction coarse adjustment command, the MCU reads data received by the serial port and controls a program control amplifier of a program control high-voltage input circuit to perform corresponding adjustment until a gain correction error is less than or equal to 1%; after the gain rough adjustment, if the gain error of the transmitter is less than or equal to 1% and more than or equal to 0.01%, performing gain correction fine adjustment; the serial port receives a gain correction fine adjustment command, the MCU reads data received by the serial port and controls the PWM1 and the PWM2 to adjust in the same stepping direction and opposite directions until the gain error is less than 0.01%; and if the gain error is less than 0.01%, the gain correction is finished. At this time, the gear correction is completed; switching the coding switch digital code to 0001 to carry out second gear correction; the zero offset correction method is similar to the first gear, when the gain correction is carried out, the input voltage of the transmitter is set to be the maximum input voltage of the second gear, and the correction method is similar to the first gear; other gears are calibrated in sequence until all gears are calibrated; after the correction is completed, a correction completion command is sent to the MCU through the serial port, the MCU stores the corrected data and closes the serial port, and after the serial port is closed, the coding switch is enabled, the change of the coding switch is continuously detected, and corresponding configuration data is called.
Claims (4)
1. A multi-range high-precision high-voltage isolation transmitter comprises a high-voltage input circuit, a resistor array, a PWM (pulse-width modulation) closed-loop control circuit, an isolation coupling mutual inductor, a PWM demodulation circuit and a linear integration circuit; the input high-voltage signal to be detected attenuates the high-voltage signal into a low-voltage small signal which can be identified by a controller through a high-voltage input circuit, adjusts the zero offset of the signal through a resistor array, sends the signal into a PWM closed-loop control circuit to be converted into a PWM signal, and sends the PWM signal to a PWM demodulation circuit and a linear integration circuit to be converted into a voltage amplitude signal after being isolated by an isolation coupling mutual inductor; the method is characterized in that: the multi-range selection circuit and the MCU control circuit are also included; the high-voltage input circuit and the resistor array are respectively a program-controlled high-voltage input circuit and a programmable resistor array controlled by the MCU control circuit;
the multi-range selection circuit is connected with the MCU control circuit;
the device also comprises a coarse adjustment module for gain calibration, a coarse adjustment module for zero offset calibration and a fine adjustment module for gain and zero offset calibration;
the coarse adjustment module for gain calibration consists of the MCU control circuit and a program control amplifier in the program control high-voltage input circuit; the coarse tuning module for zero offset calibration consists of an MCU control circuit and a programmable resistor array; the gain calibration and zero offset calibration fine tuning module MCU control circuit is composed of a working power supply of a PWM closed-loop control circuit.
2. The multi-range high-precision high-voltage isolation transmitter of claim 1, wherein: the gain and zero offset calibration fine tuning module comprises: a first integrating circuit consisting of a resistor R12 and a capacitor C11 and a second integrating circuit consisting of a resistor R15 and a capacitor C12; a first follower consisting of an operational amplifier U11A and a resistor R11 and a second follower consisting of an operational amplifier U11B and a resistor R14;
the MCU control circuit outputs PWM1 with adjustable duty ratio, the PWM1 is integrated by the first integrating circuit and then is output by the first follower to be connected with a power supply VCC +;
the MCU control circuit outputs PWM2 with adjustable duty ratio, the PWM2 is integrated by a second integrating circuit and then is output by a second follower to be connected with a power supply VCC-.
3. The multi-range high-precision high-voltage isolation transmitter of claim 1, wherein: the PWM closed-loop control circuit comprises a square wave oscillation circuit, a triangular wave circuit, an integral comparison circuit and a PWM modulation signal output circuit;
the square wave oscillation circuit comprises a Schmitt inverter U2A, a Schmitt inverter U2D, a resistor R4 and a capacitor C2; the output end of the Schmitt inverter U2A is connected with the input end of the Schmitt inverter U2D; the resistor R4 is arranged between the input end and the output end of the Schmitt inverter U2A, one end of the capacitor C2 is connected with the input end of the Schmitt inverter U2A, and the other end of the capacitor C2 is connected with the output end of the Schmitt inverter U2D;
the triangular wave circuit comprises a resistor R3 and a capacitor C3; the square wave output by the square wave oscillation circuit is connected with one end of a resistor R3, and the other end of the resistor R3 is grounded through a capacitor C3; the common end of the resistor R3 connected with the capacitor C3 forms an output end S2 of the triangular wave;
the integral comparison circuit comprises an operational amplifier U1, a Schmitt inverter U2F, a capacitor C1, a resistor R1, a resistor R2, a capacitor C4 and a resistor R5; the output end S2 of the triangular wave is connected with the input end of a Schmitt inverter U2F, the output end of the Schmitt inverter U2F is connected with one end of a resistor R5, and the 14 pin and the 7 pin of the Schmitt inverter U2F are respectively connected with a power supply VCC + and VCC-; the other end of the resistor R5 is grounded through a capacitor C4; an input signal VIN is connected and superposed with a common end connected with a resistor R5 and a capacitor C4 after being limited by a resistor R1, and then is connected with an out-phase end of an operational amplifier, and the in-phase end of the operational amplifier is connected with an input end ground level VF; the capacitor C1 is arranged between the out-phase end and the output end of the operational amplifier U1, and the output end of the operational amplifier U1 is connected with the end of the resistor R3 connected with the capacitor C3 through the resistor R2;
the PWM modulation signal output circuit comprises a Schmitt inverter U2B, a Schmitt inverter U2C and a capacitor C5; the input end of the Schmitt inverter U2B is connected with the input end of the Schmitt inverter U2C; the output end of the Schmitt inverter U2B and the output end of the Schmitt inverter U2C are connected with each other; the resistor R2 is connected with the common end of the resistor R3 connected with the capacitor C3 and is respectively connected with the input ends of the Schmitt inverter U2B and the Schmitt inverter U2C, the output ends of the Schmitt inverter U2B and the Schmitt inverter U2C are connected with one end of the capacitor C5, and the other end of the capacitor C5 forms the output S4 of the PWM closed-loop control circuit.
4. The multi-range high accuracy high voltage isolation transmitter of any one of claims 1 or 2 or 3, wherein: the isolation coupling mutual inductor is a high isolation coupling mutual inductor embedded in a PCB.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111537774A (en) * | 2020-06-05 | 2020-08-14 | 镇江英创电力电子有限公司 | Multi-range high-precision high-voltage isolation transmitter and calibration method |
| CN114221642A (en) * | 2022-02-22 | 2022-03-22 | 浙江地芯引力科技有限公司 | PWM wave generation and duty ratio control method, device, timer and equipment |
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2020
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN111537774A (en) * | 2020-06-05 | 2020-08-14 | 镇江英创电力电子有限公司 | Multi-range high-precision high-voltage isolation transmitter and calibration method |
| CN114221642A (en) * | 2022-02-22 | 2022-03-22 | 浙江地芯引力科技有限公司 | PWM wave generation and duty ratio control method, device, timer and equipment |
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