A voltage isolation sampling circuit and implementation method thereof

Abstract

The invention discloses a voltage isolation sampling circuit and a control method thereof, comprising a DC power supply to be tested; an AC voltage source; a first resistor; a sampling resistor; a transformer unit, comprising a primary coil and a secondary coil, wherein the primary coil is connected to the DC power supply to be tested via the first resistor, and the secondary coil is connected to the second AC end of the AC voltage source via the sampling resistor; a sampling signal processing module, which is used to process the sampling signal at the output end of a precision rectifier circuit to obtain an electrical signal value of the DC power supply to be tested; a transformer is used to isolate the DC voltage source to be tested from the sampling resistor, which has high isolation, good precision and linearity, and can meet the needs of most application occasions; in addition, the sampling signal processing module adopts MCU technology, uniformly completes various data processing of the AC voltage source, the sampling and holding unit, the low-pass filtering unit, the delay circuit, the zero calibration unit, and the operation unit and the amplification unit, and has good economic performance.

Description

Technical Field

[0001] The present invention relates to the field of electronics, and in particular to a voltage isolation sampling circuit and an implementation method thereof. Background Art

[0002] Existing DC voltage isolation sampling technologies generally use Hall devices and transformer isolation technology, linear optocoupler isolation technology, isolation amplifier technology, voltage-frequency conversion followed by transformer or optocoupler isolation technology, and direct A / D sampling at the DC voltage end followed by isolated communication transmission technology. Some of the above technologies are relatively expensive, some have poor accuracy and linearity, some devices are difficult to purchase, and some require additional isolated power supplies, with complex circuits that cannot meet application scenarios with high performance and cost requirements. Summary of the invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. By adding a current limiting resistor to the primary coil of the transformer unit, adding an AC voltage source and a sampling resistor to the secondary coil, the sampling signal processing module is used to collect the current of the sampling resistor when the transformer unit inputs an AC voltage, so as to complete the isolation detection of the DC power supply to be tested.

[0004] In one aspect, the present invention provides a voltage isolation sampling circuit, comprising: a DC power supply to be tested; an AC voltage source; a first resistor; a sampling resistor;

[0005] A transformer unit, comprising a primary coil and a secondary coil, wherein the primary coil is connected to the DC power supply to be measured via a first resistor, and the secondary coil is connected to a second AC terminal of the AC voltage source via the sampling resistor;

[0006] The sampling signal processing module is used to process the sampling signal at the output end of the precision rectifier circuit to obtain the electrical signal value of the DC power supply to be tested.

[0007] Furthermore, the first resistor is a current limiting resistor, one end of the current limiting resistor is connected to the positive electrode of the DC voltage source, and the other end of the current limiting resistor is connected to one end of the primary coil.

[0008] Furthermore, a precision rectifier circuit is connected between the sampling resistor and the sampling signal processing module, one end of the sampling resistor is connected to the second secondary end of the secondary coil, and is also connected to the input end of the precision rectifier circuit, and the output end of the precision rectifier circuit is connected to the sampling signal processing module, for precisely rectifying the sampling signal of the sampling resistor and sending the sampling signal to the signal processing module.

[0009] Furthermore, an input end of the precision rectifier circuit is connected to the other end of the secondary coil, and an output end of the precision rectifier circuit is connected to the data processing module.

[0010] Furthermore, the sampling signal processing module is composed of an MCU integrating multiple functional units, the MCU is used to output the driving signal of the AC voltage source, the signal processing module also includes a calculation unit, which is used to calculate and output the sampling signal, the functional units of the MCU include a sampling and holding unit, a low-pass filtering unit, and a calculation unit, a delay circuit, a zero point calibration unit and an amplification unit, the sampling and holding unit is used to sample and hold the signal at the time point determined by the delay circuit, the signal is filtered by the low-pass filtering unit, and then calculated with the value of the zero point calibration unit, and then input into the amplification unit for amplification to obtain the measured voltage value.

[0011] Furthermore, the output end of the amplification unit is also connected to a display device for displaying the calculation result.

[0012] On the other hand, a method for implementing a voltage isolation sampling circuit includes applying a DC voltage to the primary coil until the transformer unit is saturated when there is no AC signal in the secondary coil, and the transformer unit cannot transmit signals when it is in a saturated state;

[0013] When the positive half cycle of AC voltage is applied to the secondary coil and the current reaches a certain intensity, the transformer unit gradually exits the saturation state and runs along the hysteresis loop to the other end and enters the saturation state again;

[0014] When the secondary winding AC voltage is in the negative half cycle, the transformer unit exits the saturation state along the hysteresis loop, runs along the hysteresis loop to the other end, and enters the saturation state again.

[0015] Furthermore, when the transformer unit exits the saturation state, a signal can be transmitted, and the signal transmission of the primary coil is fed back to the secondary coil, and a current is generated in the sampling resistor. The sampling signal processing module samples the signal value during this period and calculates the value of the DC power supply.

[0016] Furthermore, when the voltage transformation unit is in a saturated state, the current on the sampling resistor is the current generated by the AC voltage source in the secondary coil.

[0017] Furthermore, the hysteresis loop of the transformer unit shifts along the magnetic field intensity as the magnitude of the DC to be measured increases.

[0018] The beneficial effects of the present invention are as follows: a transformer is used to isolate the DC voltage source to be measured from the sampling resistor, which has high isolation, good precision and linearity, and can meet the needs of most application scenarios. In addition, the sampling signal processing module adopts MCU technology to uniformly complete various data processing of the AC voltage source, the sampling and holding unit, the low-pass filtering unit, the delay circuit, the zero point calibration unit, the operation unit and the amplification unit, and has good economic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is an overall structural block diagram of a voltage isolation circuit of the present invention;

[0020] Figure 2 It is a circuit principle diagram of a precision rectifier circuit of a voltage isolation circuit of the present invention;

[0021] Figure 3 It is a circuit schematic diagram of a sampling signal processing module of a voltage isolation circuit of the present invention;

[0022] Figure 4 It is a schematic diagram of a hysteresis loop when an AC power supply is applied to a secondary coil of a voltage isolation circuit of the present invention and the primary coil voltage is 0;

[0023] Figure 5 It is a current waveform diagram when the primary coil voltage is 0 when an AC power supply is applied to the secondary coil of a voltage isolation circuit of the present invention;

[0024] Figure 6 It is a schematic diagram of a hysteresis loop when an AC power supply is applied to a secondary coil of a voltage isolation circuit of the present invention and the voltage of the primary coil is DC;

[0025] Figure 7 It is a current waveform diagram when an AC power supply is applied to a secondary coil of a voltage isolation circuit of the present invention and the voltage of the primary coil is DC;

[0026] Figure 8 The present invention is a flow chart of a control method for a voltage isolation circuit of the present invention.

[0027] Attached figure numbers: 10, voltage isolation sampling circuit; 20, precision rectification circuit; 30, sampling signal processing module; 301, sampling and holding unit; 302, low-pass filtering unit; 303, summing operation unit; 304, amplification unit; Vin, measured DC voltage source; R1, current limiting resistor; W1, primary coil; W2, secondary coil; U, AC voltage source; Q1, sampling resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; V1, first diode; V2, second diode; F1, first operational amplifier; F2, second operational amplifier; GND, ground terminal; T, delay unit; Z, zero point calibration unit; V, display device; GND, ground terminal. DETAILED DESCRIPTION

[0028] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0029] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0030] The specific implementation of the present invention will be further described below in conjunction with the accompanying drawings.

[0031] Reference Figure 1As an optional implementation, the voltage isolation sampling circuit 10 includes a DC power supply Vin to be tested; an AC voltage source U; a first resistor R1; a sampling resistor Q1; a transformer unit, including a primary coil W1 and a secondary coil W2. One end of the primary coil W1 is connected to the first resistor R1, and then connected to the positive end of the DC power supply Vin, and the other end is connected to the negative end of the DC power supply Vin to be tested. The first secondary end of the secondary coil W2 is connected to the first AC end of the AC voltage source U through the sampling resistor Q1, and the second secondary end of the secondary coil W2 is connected to the second AC end of the AC voltage source U; a precision rectifier circuit 20 is also connected between the sampling resistor Q1 and the sampling signal processing module 30, one end of the sampling resistor Q1 is connected to the second secondary end of the secondary coil W2, and is also connected to the input end of the precision rectifier circuit 20, and the output end of the precision rectifier circuit 20 is connected to the sampling signal processing module 30, and the sampling signal processing module 30 is used to process the sampling signal output by the precision rectifier circuit to obtain the electrical signal value of the DC power supply Vin to be tested. The first resistor R1 is a current limiting resistor, which is used to limit the current of the DC power supply Vin to be tested to prevent excessive current from burning components; a sampling resistor Q1 is also provided between the secondary coil W2 and the AC voltage source U to collect the signal value output by the secondary coil W2 for sampling and processing by the sampling signal processing module 30.

[0032] Reference Figure 2 As an optional embodiment, the precision rectifier circuit 20 includes a first operational amplifier F1, a second operational amplifier F2, a first diode V1, a second diode V2, a second resistor R2, a third resistor R3, a fourth resistor R4 and a fifth resistor R5, one end of the second resistor R2 is grounded, the other end of the second resistor R2, one end of the third resistor R3 and the cathode of the first diode V1 are all connected to the inverting input terminal of the first operational amplifier F1, the other end of the third resistor R3 and one end of the fourth resistor R4 are all connected to the anode of the second diode V2, and the anode of the first diode V1 and the cathode of the second diode V2 are connected. The cathodes are connected to the output end of the first operational amplifier F1, the other end of the fourth resistor R4 and one end of the fifth resistor R5 are connected to the inverting input end of the second operational amplifier F2, the other end of the fifth resistor R5 is connected to the output end of the second operational amplifier F2, the positive input ends of the first operational amplifier F1 and the second operational amplifier F2 are connected to the other end of the secondary coil W2, and the output end of the second operational amplifier F2 is also connected to the sampling signal processing module 30. A precision rectifier circuit is formed by two operational amplifiers to complete the rectification and signal amplification functions, and output the signal to the sampling signal processing module 30.

[0033] Reference Figure 3As an optional implementation, the sampling signal processing module 30 includes a sampling and holding unit 301 and a computing unit 303, a low-pass filtering unit 302, a delay circuit T, a zero calibration unit Z and an amplifying unit 304, wherein the amplifying unit 304 is used to amplify the sampling signal at the output end to obtain the electrical signal value of the DC power supply Vin to be measured; the sampling and holding unit 301 is used to store the signal value for subsequent calculation; the low-pass filtering unit 302 is used to perform low-pass filtering on the stored value to eliminate interference; the delay circuit T is used to convert the AC voltage source U The signal is delayed for a fixed time to provide a time reference point, and the corresponding signal value at the linear segment is read for the voltage signal after precision rectification; the zero-point calibration unit Z is calibrated when the DC voltage of the primary coil W1 is 0 to eliminate the zero-point error; and the operation unit 303 operates on the signal value after low-pass filtering and the zero-point calibration value; the amplification unit 304 amplifies the initial value and the numerical value after operation so that the output value is approximately equal to the input value; the display device V is used to display the calculation results; optionally, the display device V can be connected to the amplification unit through an HMI interface or a general I / O port.

[0034] A control method for a voltage isolation sampling circuit, including but not limited to the following steps:

[0035] S101, when there is no AC signal in the secondary coil, a DC voltage is applied to the primary coil until the transformer unit is saturated. When the transformer unit is in a saturated state, no signal can be transmitted;

[0036] S102, when the positive half cycle of the AC voltage is applied to the secondary coil and the current reaches a certain intensity, the transformer unit gradually exits the saturation state, runs along the hysteresis loop to the other end, and enters the saturation state again;

[0037] S103, when the secondary winding AC voltage is in the negative half cycle, the transformer unit exits the saturation state along the hysteresis loop, runs to the other end along the hysteresis loop, and enters the saturation state again;

[0038] S104, when the transformer unit exits the saturation state, a signal can be transmitted, the signal transmission of the primary coil is fed back to the secondary coil, and a current is generated in the sampling resistor, and the sampling signal processing module samples the signal value during this period and calculates the value of the primary DC voltage;

[0039] Reference Figure 4 , Figure 4 The hysteresis loop when the primary coil voltage is 0 when AC power is applied to the secondary coil.

[0040] Reference Figure 5 , Figure 5 The current waveform when the primary coil voltage is 0 when AC power is applied to the secondary coil.

[0041] Reference Figure 6 , Figure 6 The hysteresis loop when the primary coil voltage is DC and AC power is applied to the secondary coil.

[0042] Reference Figure 7 , Figure 7 Current waveform when AC power is applied to the secondary coil and the primary coil voltage is DC.

[0043] It is worth noting that the hysteresis loop of the transformer unit shifts along the H axis with the magnitude of the DC voltage. H = N*I / L (N-number of turns of the iron core transformer, I-current, L-magnetic path length, H-magnetic field strength). The number of turns of the iron core transformer and the magnetic path length remain unchanged. When the current changes, the hysteresis loop shifts along the magnetic field strength.

[0044] The simulation results of the voltage isolation sampling circuit of this scheme are as follows (the amplification factor K value is calibrated with 120V):

[0045] Vdc=60V,Vout=59.98V

[0046] Vdc=120V,Vout=120V

[0047] Vdc=180V,Vout=180.07V

[0048] Vdc=240V,Vout=240.17V

[0049] Vdc=300V,Vout=300.32V

[0050] Vdc=360V,Vout=360.51V

[0051] It can be seen from the above simulation results that the accuracy and linearity of the voltage isolation sampling circuit of this scheme are good, and the maximum deviation is +0.14%.

[0052] The working principle of a voltage isolation sampling circuit of the present invention is:

[0053] When there is no AC signal in the secondary coil of the iron core transformer, a DC voltage is applied to the primary coil of the iron core transformer until the transformer is saturated, and an AC voltage is applied to the secondary coil of the iron core transformer. When the current reaches a certain level, the iron core transformer exits the saturation state, runs along the hysteresis loop to the other end, and enters the saturation state again. When the iron core transformer exits the saturation state, the signal can be transmitted, and the signal of the primary coil of the iron core transformer is fed back to the secondary coil of the iron core transformer, and a current is generated on the sampling resistor. The sampling signal processing module samples the signal value during this period, and calculates the value of the primary DC voltage of the iron core transformer based on the sampled value.

[0054] The above is a specific description of the preferred implementation of the present invention, but the invention is not limited to the embodiments. Those skilled in the art can make various equivalent changes or substitutions without violating the spirit of the present invention. These equivalent changes or substitutions are all included in the scope defined by the claims of this application.

Claims

1. A voltage isolation sampling circuit, characterized in that: include: The DC power supply to be tested; AC voltage source; a first resistor; Sampling resistor; A transformer unit, comprising a primary coil and a secondary coil, wherein the primary coil is connected to the DC power supply to be measured via a first resistor, and the secondary coil is connected to a second AC terminal of the AC voltage source via the sampling resistor; A sampling signal processing module is used to process the sampling signal at the output end of the precision rectification circuit to obtain the electrical signal value of the DC power supply to be measured. A precision rectification circuit is also connected between the sampling resistor and the sampling signal processing module. One end of the sampling resistor is connected to the second secondary end of the secondary coil and is also connected to the input end of the precision rectification circuit. The output end of the precision rectification circuit is connected to the sampling signal processing module to perform precision rectification on the sampling signal of the sampling resistor and send the sampling signal to the signal processing module. The precision rectification circuit includes a first operational amplifier, a second operational amplifier, a first diode, a second diode, a second resistor, a third resistor, a fourth resistor and a fifth resistor. One end of the second resistor is grounded. The other end of the second resistor, one end of the third resistor and the cathode of the first diode are all connected to the inverting input terminal of the first operational amplifier, the other end of the third resistor and one end of the fourth resistor are all connected to the anode of the second diode, the anode of the first diode and the cathode of the second diode are all connected to the output terminal of the first operational amplifier, the other end of the fourth resistor and one end of the fifth resistor are all connected to the inverting input terminal of the second operational amplifier, the other end of the fifth resistor is connected to the output terminal of the second operational amplifier, the positive input terminals of the first operational amplifier and the second operational amplifier are all connected to the other end of the secondary coil, and the output terminal of the second operational amplifier is also connected to the sampling signal processing module.

2. A voltage isolation sampling circuit according to claim 1, characterized in that: The first resistor is a current limiting resistor, one end of the current limiting resistor is connected to the positive electrode of the DC voltage source, and the other end of the current limiting resistor is connected to one end of the primary coil.

3. The voltage isolation sampling circuit according to claim 1, characterized in that: The input end of the precision rectifier circuit is connected to the other end of the secondary coil, and the output end of the precision rectifier circuit is connected to the sampling signal processing module.

4. The voltage isolation sampling circuit according to claim 1, characterized in that: The sampling signal processing module is composed of an MCU integrating multiple functional units. The MCU is used to output the driving signal of the AC voltage source. The signal processing module also includes a calculation unit for calculating and outputting the sampling signal. The functional units of the MCU include a sampling and holding unit, a low-pass filtering unit, a calculation unit, a delay circuit, a zero point calibration unit and an amplification unit. The sampling and holding unit is used to sample and hold the signal at a time point determined by the delay circuit. After the signal is filtered by the low-pass filtering unit, it is calculated with the value of the zero point calibration unit and then input into the amplification unit for amplification to obtain the measured voltage value.

5. The voltage isolation sampling circuit according to claim 4, characterized in that: The output end of the amplifying unit is also connected to a display device for displaying the calculation result.

6. A method for implementing a voltage isolation sampling circuit, characterized in that: The voltage isolation sampling circuit according to any one of claims 1 to 5 comprises: When there is no AC signal in the secondary coil, a DC voltage is applied to the primary coil until the transformer unit is saturated. When the transformer unit is in a saturated state, the signal cannot be transmitted. When the positive half cycle of AC voltage is applied to the secondary coil and the current reaches a certain intensity, the transformer unit gradually exits the saturation state and runs along the hysteresis loop to the other end and enters the saturation state again; When the secondary winding AC voltage is in the negative half cycle, the transformer unit exits the saturation state along the hysteresis loop, runs along the hysteresis loop to the other end, and enters the saturation state again.

7. The method for implementing a voltage isolation sampling circuit according to claim 6, characterized in that: When the transformer unit exits the saturation state, it can transmit a signal. The signal transmission of the primary coil is fed back to the secondary coil and generates current in the sampling resistor. The sampling signal processing module samples the signal value during this period and calculates the value of the DC power supply to be tested.

8. The method for implementing a voltage isolation sampling circuit according to claim 7, characterized in that: When the voltage transformation unit is in a saturated state, the current on the sampling resistor is the current generated by the AC voltage source in the secondary coil.

9. The method for implementing a voltage isolation sampling circuit according to claim 8, characterized in that: The hysteresis loop of the transformer unit shifts along the magnetic field intensity as the magnitude of the DC to be measured increases.

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