Differential multi-channel high-voltage sampling circuit with second-order low-pass filtering

Abstract

The invention discloses a differential multi-channel high-voltage sampling circuit with second-order low-pass filtering, comprising: a high-voltage sampling circuit, a differential second-order low-pass filtering circuit, a first-order RC filter and an ESD diode; the high-voltage sampling circuit comprises positive and negative sampling voltage-dividing resistors, the input ends of the positive and negative sampling voltage-dividing resistors are respectively connected to the positive and negative poles of the peripheral high voltage, and the output ends respectively output positive level signals and negative level signals; the two input ends of the differential second-order low-pass filtering circuit are respectively connected to the output ends of the positive and negative sampling voltage-dividing resistors, and the output end of the differential second-order low-pass filtering circuit is connected to the first-order RC filter; the first-order RC filter is connected in parallel with the ESD diode and output to the input port of the DSP chip. Through the technical solution of the invention, the noise of the AC signal is effectively reduced, the common-mode interference is suppressed, the multiple protections of the circuit are realized, and the cost of voltage acquisition is greatly reduced.

Description

Technical Field

[0001] The invention relates to the technical field of power electronics, and in particular to a differential multi-channel high-voltage sampling circuit with second-order low-pass filtering. Background Art

[0002] At present, with the development of power electronics technology, the processing and control of high voltage and large current are inseparable from power electronics technology, and the sampling circuit is crucial to the entire system. The accuracy of the collected signal directly affects the output control effect.

[0003] Digital Signal Processing (DSP) is an emerging discipline that involves many disciplines and is widely used in many fields. Since the 1960s, with the rapid development of computer and information technology, digital signal processing technology has emerged and has developed rapidly. In the past two decades, digital signal processing has been widely used. DSP chips are chips that can implement digital signal processing technology.

[0004] A filter is an electronic device that allows useful signals to pass through while suppressing useless frequency signals. It is widely used in automatic control and other electronic systems such as data transmission, information processing and interference suppression.

[0005] However, the existing sampling circuit cannot provide accurate signals to the DSP chip, and there is a lot of noise. The filtering circuit cannot effectively suppress the noise signal in the circuit and protect the DSP chip at the same time, and the cost of sampling multi-channel signals is high. Summary of the invention

[0006] In response to at least one of the above problems, the present invention provides a differential multi-channel high-voltage sampling circuit with second-order low-pass filtering. Through differential design, the noise of the AC signal is effectively reduced and common-mode interference is suppressed. Multiple filters are used in the entire high-voltage sampling circuit to achieve multiple protections for the circuit. At the same time, a multi-channel sampling circuit is used to greatly reduce the cost of voltage acquisition.

[0007] To achieve the above-mentioned purpose, the present invention provides a differential multi-channel high-voltage sampling circuit with second-order low-pass filtering, comprising: a high-voltage sampling circuit, a differential second-order low-pass filtering circuit, a first-order RC filter and an ESD diode; the high-voltage sampling circuit comprises positive and negative sampling voltage-dividing resistors, the input ends of the positive and negative sampling voltage-dividing resistors are respectively connected to the positive and negative poles of the peripheral high voltage, and the output ends respectively output positive level signals and negative level signals; the two input ends of the differential second-order low-pass filtering circuit are respectively connected to the output ends of the positive and negative sampling voltage-dividing resistors, and the output end of the differential second-order low-pass filtering circuit is connected to the first-order RC filter; the first-order RC filter is connected in parallel with the ESD diode and output to the input port of the DSP chip.

[0008] In the above technical solution, preferably, the differential second-order low-pass filter circuit includes an operational amplifier, the positive and negative input terminals of the operational amplifier are respectively connected to the first-order filter circuit, the second-order filter circuit and the switching diode, and are correspondingly connected to the positive and negative sampling voltage divider resistors, and the output terminal of the operational amplifier is connected to the resistor of the first-order RC filter.

[0009] In the above technical scheme, preferably, the first-order filter circuit and the second-order filter circuit connected to the negative level signal input terminal of the operational amplifier are both resistors and capacitors connected in series, the first-order filter circuit is connected in parallel with the resistor of the second-order filter circuit, one end of the resistor of the first-order filter circuit is respectively connected to the sampling voltage divider resistor that outputs the negative level signal, the capacitor of the second-order filter circuit and the switching diode, the other end of the resistor of the first-order filter circuit is respectively connected to the capacitor of the first-order filter circuit and the negative level signal input terminal of the operational amplifier, and the capacitor of the first-order filter circuit is respectively connected to the resistor of the second-order filter circuit and the output terminal of the operational amplifier.

[0010] In the above technical scheme, preferably, the second-order filter circuit connected to the positive level signal input terminal of the operational amplifier is a resistor and a capacitor connected in series, and the first-order filter circuit is a resistor and a capacitor connected in parallel, one end of the capacitor of the second-order filter circuit is respectively connected to the resistor of the second-order filter circuit and the positive level signal input terminal of the operational amplifier, and the other end is grounded, the other end of the resistor of the second-order filter circuit is respectively connected to the sampling voltage divider resistor that outputs the positive level signal, the capacitor and the resistor of the first-order filter circuit in parallel, and the switching diode, and the other end of the capacitor and the resistor of the first-order filter circuit in parallel are grounded.

[0011] In the above technical solution, preferably, the switching diode is LBA99WT1G, pin 1 and pin 2 of the LBA99WT1G switching diode are connected to the positive and negative power supplies respectively, and pin 3 is connected to the first-order filter circuit and the second-order filter circuit.

[0012] In the above technical solution, preferably, the first-order RC filter is a resistor and a capacitor connected in series, one end of the resistor of the first-order RC filter is connected to the output end of the differential second-order low-pass filter circuit, and the other end is respectively connected to the capacitor of the first-order RC filter, the I / O end of the ESD diode and the input port of the DSP chip, and the other end of the capacitor of the first-order RC filter is grounded.

[0013] In the above technical solution, preferably, pin 2 of the ESD diode is directly connected to REFGND, and pin 5 is connected to REFGND via a preset number of parallel capacitors.

[0014] In the above technical solution, preferably, the ESD diode includes 4 I / O terminals, the 4 I / O terminals can be respectively connected to four groups of the first-order RC filters, and the four groups of the first-order RC filters are respectively connected to four groups of differential second-order low-pass filter circuits and high-voltage sampling circuits to simultaneously realize four-channel high-voltage sampling.

[0015] In the above technical solution, preferably, the sampling voltage-dividing resistor is composed of a preset number of high-precision and high-resistance resistors connected in series.

[0016] In the above technical solution, preferably, the operational amplifier is connected to power supply voltages of +15V and -15V respectively.

[0017] Compared with the prior art, the beneficial effects of the present invention are: through differential design, the noise of the AC signal is effectively reduced, common-mode interference is suppressed, multiple filters are used in the entire high-voltage sampling circuit to achieve multiple protections for the circuit, and a multi-channel sampling circuit is used to greatly reduce the cost of voltage acquisition. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of the circuit principle of a differential multi-channel high-voltage sampling circuit with second-order low-pass filtering disclosed in an embodiment of the present invention;

[0019] Figure 2 A schematic diagram of a simulation circuit of a differential multi-channel high-voltage sampling circuit with second-order low-pass filtering disclosed in an embodiment of the present invention;

[0020] Figure 3 for Figure 2 The schematic diagram of the oscilloscope waveform of the simulation circuit disclosed in the illustrated embodiment;

[0021] Figure 4 for Figure 2 A schematic diagram of waveforms of a Bode tester of a simulation circuit disclosed in the illustrated embodiment;

[0022] Figure 5 for Figure 1 A schematic diagram of the circuit principle of a four-channel high-voltage sampling circuit disclosed in the illustrated embodiment;

[0023] Figure 6 for Figure 1 A schematic diagram of the circuit principle of one of the differential second-order low-pass filter circuits disclosed in the illustrated embodiment;

[0024] Figure 7 for Figure 1 The circuit principle diagram of the four-channel first-order RC filter disclosed in the illustrated embodiment;

[0025] Figure 8 for Figure 1 A schematic diagram of the circuit principle of the ESD diode disclosed in the illustrated embodiment;

[0026] Fig. 9 The present invention discloses a circuit connection diagram of a single-channel high-voltage sampling circuit according to an embodiment of the present invention. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0029] like Figure 1 As shown, a differential multi-channel high-voltage sampling circuit with second-order low-pass filtering provided by the present invention includes: a high-voltage sampling circuit, a differential second-order low-pass filtering circuit, a first-order RC filter and an ESD diode; the high-voltage sampling circuit includes positive and negative sampling voltage-dividing resistors, the input ends of the positive and negative sampling voltage-dividing resistors are respectively connected to the positive and negative electrodes of the peripheral high voltage, and the output ends respectively output positive level signals and negative level signals; the two input ends of the differential second-order low-pass filtering circuit are respectively connected to the output ends of the positive and negative sampling voltage-dividing resistors, and the output end of the differential second-order low-pass filtering circuit is connected to the first-order RC filter; the first-order RC filter is connected in parallel with the ESD diode and output to the input port of the DSP chip.

[0030] like Figures 2 to 5As shown, in this embodiment, the high-voltage sampling circuit obtains a pair of differential signals through sampling voltage-dividing resistors, which are positive level signals and negative level signals, respectively, as signal inputs of the differential second-order low-pass filter circuit. The differential second-order low-pass filter circuit absorbs the high-frequency part of the input signal, passes the low-frequency signal of the fixed frequency band, and filters out the high-frequency clutter signal, providing a pure signal to the DSP chip. The positive level signal passes through the resistor and capacitor, and is finally connected to the positive level signal input end of the operational amplifier TLV4170; the negative level signal passes through the resistor and capacitor, and is finally connected to the negative battery signal input end of the operational amplifier TLV4170. After being processed by the operational amplifier TLV4170, the two differential signal outputs are finally connected to the first-order RC filter, and the ESD diode SRV05-4 is connected in parallel to protect the DSP chip. After a series of processing, it finally enters the GPIO of the DSP chip.

[0031] In the above embodiment, preferably, the differential second-order low-pass filter circuit includes an operational amplifier TLV4170, the positive and negative input terminals of the operational amplifier are respectively connected to the first-order filter circuit, the second-order filter circuit and the switching diode, and are correspondingly connected to the positive and negative sampling voltage divider resistors, and the output terminal of the operational amplifier is connected to the resistor of the first-order RC filter.

[0032] In the above embodiment, preferably, the switching diode is LBA99WT1G, and pins 1 and 2 of the LBA99WT1G switching diode are connected to the positive and negative power supplies respectively, and pin 3 is connected to the first-order filter circuit and the second-order filter circuit.

[0033] The following takes the high-voltage sampling circuit of one channel as an example to illustrate the differential multi-channel high-voltage sampling circuit with second-order low-pass filtering.

[0034] like Figure 6 As shown, in the above embodiment, preferably, the first-order filter circuit and the second-order filter circuit connected to the negative level signal input terminal of the operational amplifier are both resistors and capacitors connected in series, the first-order filter circuit is connected in parallel with the resistor R2 of the second-order filter circuit, one end of the resistor R6 of the first-order filter circuit is respectively connected to the sampling voltage divider resistor that outputs the negative level signal, the capacitor C2 of the second-order filter circuit and the switching diode, the other end of the resistor R6 of the first-order filter circuit is respectively connected to the capacitor C4 of the first-order filter circuit and the negative level signal input terminal of the operational amplifier TLV4170, and the capacitor C4 of the first-order filter circuit is respectively connected to the resistor R2 of the second-order filter circuit and the output terminal of the operational amplifier.

[0035] Specifically, the negative level signal is connected to the left end of resistor R5, the right end of R5 is connected to the left end of R6, the right end of R6 is connected to the positive level signal input pin 2 of TLV4170, and connected to the left end of filter capacitor C4, and the right end of C4 is connected to the output pin 1 of operational amplifier TLV4170. The right end of capacitor C2 is connected to the right end of R5 and the left end of R6, and the switching diode LBA99WT1G is connected. Resistor R2 is connected between this pin and the output pin of TLV4170, and grounded at the left end of C2. Pin 2 of LBA99WT1G is connected to a +15V power supply, and pin 1 of LBA99WT1G is connected to a -15V power supply. For negative level signals, R6 and C4 form a first-order filter circuit, and R2 and C2 form a second-order filter circuit. The second-order filter circuit can calculate the cutoff frequency of the required signal and the value in this circuit by adjusting the resistance value of R and the capacitance value of C.

[0036] In the above embodiment, preferably, the second-order filter circuit connected to the positive level signal input terminal of the operational amplifier is a resistor and a capacitor connected in series, and the first-order filter circuit is a resistor and a capacitor connected in parallel, one end of the capacitor C8 of the second-order filter circuit is respectively connected to the resistor R19 of the second-order filter circuit and the positive level signal input terminal of the operational amplifier, and the other end is grounded, the other end of the resistor R19 of the second-order filter circuit is respectively connected to the sampling voltage divider resistor that outputs the positive level signal, the capacitor C6 and the resistor R24 ​​of the first-order filter circuit in parallel, and the switching diode, and the other end of the capacitor C6 and the resistor R24 ​​of the first-order filter circuit in parallel is grounded.

[0037] Specifically, the positive level signal is connected to the left end of resistor R18, the right end of R18 is connected to the left end of R19, and is connected to the right ends of C6 and R24 and the switching diode LBA99T1G, and the left end of C6 and the left end of R24 are grounded. The right end of R19 is connected to the positive level signal input end of the TLV4170 operational amplifier and the upper end of C8, and the lower end of C8 is connected to GND. R24 and C6 constitute the first-order filter circuit of the input signal, and R19 and C8 constitute the second-order filter circuit. For the positive level signal, the second-order filter is input before entering the TLV4170, and the output signal is finally connected to the output pin 1 of the TLV4170.

[0038] like Figure 1 As shown, VIN2 and VIN_2N, VIN3 and VIN_3N, and VIN4 and VIN_4N are respectively connected to the high-voltage sampling circuits of the other three channels, wherein the components and circuit connections correspond to the high-voltage sampling circuits of the channels connected to VIN1 and VIN_1N, and are not described again here.

[0039] In the above embodiment, preferably, the first-order RC filter is a resistor and a capacitor connected in series (R48 and C20, R47 and C17, R49 and C19, R50 and C18 are the resistors and capacitors of the first-order RC filters of the four channels respectively), one end of the resistor of the first-order RC filter is connected to the output end of the differential second-order low-pass filter circuit, and the other end is respectively connected to the capacitor of the first-order RC filter, the I / O end of the ESD diode and the input port of the DSP chip, and the other end of the capacitor of the first-order RC filter is grounded.

[0040] In the above embodiment, preferably, pin 2 of the ESD diode is directly connected to REFGND, and pin 5 is connected to REFGND via a preset number of parallel capacitors (C21, C22, C23, C24 and C25).

[0041] In the above embodiment, preferably, the ESD diode SRV05-4 includes 4 I / O terminals, and the 4 I / O terminals can be respectively connected to four groups of first-order RC filters, and the four groups of first-order RC filters are respectively connected to four groups of differential second-order low-pass filter circuits and high-voltage sampling circuits, so as to simultaneously realize four-channel high-voltage sampling. The ESD diode SRV05-4 has a low clamping voltage, which clamps the signal input level within the operating voltage range of the DSP, preventing the signal input voltage from being too high or too low and burning the DSP, thereby protecting the DSP.

[0042] In the above embodiment, preferably, the sampling voltage-dividing resistor is a preset number of high-precision high-resistance resistors (R10, R11 and R12, or R20, R21 and R22, or R7, R8 and R9, or R13, R14 and R15, or R34, R35 and R36, or R44, R45 and R46, or R27, R28 and R29, or R37, R38 and R39) connected in series.

[0043] In the above embodiment, preferably, the operational amplifier is connected to power supply voltages of +15V and -15V respectively.

[0044] According to the differential multi-channel high-voltage sampling circuit with second-order low-pass filtering provided by the above embodiment, the differential filtering circuit principle is as follows:

[0045] First, determine the amplification factor, that is, the gain of the operational amplifier. This amplification factor can be very large, or even 1. The gain of the operational amplifier used in the present invention is -1, that is, the amplification factor is 1, and the phase difference is 180°. Then select the type and angular frequency of the filter. The type and angular frequency of the filter determine the bandpass gain. There are three types of filters, Butterworth, Chebyshev and Bessel. The present invention uses a Butterworth filter. Then select the capacitors C6 and C8 of the first-order filter circuit and the second-order filter circuit for sampling the positive level signal. According to the given cut-off frequency and bandpass gain, select C6 and C8, and then calculate the resistance of R18, the resistor R19 of the second-order filter circuit and the resistor R2 of the second-order filter circuit for sampling the negative level signal. In order to meet the load requirements, R2 must not be less than 10K at the minimum. When selecting the resistor, because the calculated value and the standard resistor will have a certain deviation, there can be about 2.5% error, which is close to the calculated value.

[0046] like Figure 7 The figure shows the simulation circuit of the differential multi-channel high-voltage sampling circuit with second-order low-pass filtering in Multisim. The input signal in the simulation circuit simulates the level signal after sampling the high-voltage signal. It is connected to channel 1 of the oscilloscope with a black line and connected to the IN of the baud tester. The output is the output of the differential second-order filter circuit. It is connected to channel 2 of the oscilloscope with a black line and connected to the OUT of the baud tester. Then set the values ​​of the resistors and capacitors according to the calculated results. Use a multimeter to measure the output level, and the displayed level is about 3V. This signal will enter the DSP through the RC filter circuit and the clamping diode. The oscilloscope waveform is as follows Figure 8 As shown in the figure: The gain is set to -8.4, so the output waveform is about 1 / 8 of the input waveform amplitude, and the waveform looks smooth without burrs. Fig. 9 As shown: It has a suppression function for high-frequency signals. When high-frequency signals pass through this filter, the amplitude will be attenuated. Through the above analysis, it can be seen that the differential second-order low-pass filter circuit has a strong filtering ability for high-frequency signals.

[0047] When connecting the second-order differential filter circuit, by precisely designing the parameters of each device, a very accurate cutoff frequency can be obtained, which means that the clutter in the input signal can be filtered out very well, and a very pure and good input signal can be obtained. In addition, the TLV4170 has the characteristics of multi-channel and wide gain range, and can simultaneously obtain multiple high-voltage level signals and process them, which will greatly reduce the cost. Only one operational amplifier chip plus some peripheral resistors and capacitors are needed to obtain multiple pure input signals. The differential second-order low-pass filter circuit adopts a differential design. The advantage of the differential amplifier is that it can significantly reduce the noise of the AC signal, and the design of the differential amplifier is to suppress the common-mode signal and the common-mode interference, so that the output end can obtain a better input signal. In addition, before the I / O of the DSP, there will be a first-level RC filter as a filter circuit and an ESD diode as a clamping circuit. From the input signal entering the DSP chip, there are multiple filters and multiple protection circuits. The design of the circuit is relatively complete, and the effect is particularly good in the specific use process, and the stability is also very good.

[0048] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A differential multi-channel high-voltage sampling circuit with second-order low-pass filtering, characterized in that: include: High voltage sampling circuit, differential second-order low-pass filter circuit, first-order RC filter and ESD diode; The high-voltage sampling circuit comprises positive and negative sampling voltage-dividing resistors, the input ends of the positive and negative sampling voltage-dividing resistors are respectively connected to the positive and negative electrodes of the peripheral high voltage, and the output ends respectively output positive level signals and negative level signals; The two input ends of the differential second-order low-pass filter circuit are respectively connected to the output ends of the positive and negative sampling voltage-dividing resistors, and the output end of the differential second-order low-pass filter circuit is connected to the first-order RC filter; The first-order RC filter is connected in parallel with the ESD diode and output to the input port of the DSP chip; The differential second-order low-pass filter circuit includes an operational amplifier, the positive and negative input terminals of the operational amplifier are respectively connected to the first-order filter circuit, the second-order filter circuit and the switch diode, and are correspondingly connected to the positive and negative sampling voltage-dividing resistors, and the output terminal of the operational amplifier is connected to the resistor of the first-order RC filter; The first-order filter circuit and the second-order filter circuit connected to the negative level signal input terminal of the operational amplifier are both resistors and capacitors connected in series, the first-order filter circuit is connected in parallel with the resistor of the second-order filter circuit, one end of the resistor of the first-order filter circuit is respectively connected to the sampling voltage divider resistor that outputs the negative level signal, the capacitor of the second-order filter circuit and the switching diode, the other end of the resistor of the first-order filter circuit is respectively connected to the capacitor of the first-order filter circuit and the negative level signal input terminal of the operational amplifier, and the capacitor of the first-order filter circuit is respectively connected to the resistor of the second-order filter circuit and the output terminal of the operational amplifier; The second-order filter circuit connected to the positive level signal input end of the operational amplifier is a resistor and a capacitor connected in series, and the first-order filter circuit is a resistor and a capacitor connected in parallel. One end of the capacitor of the second-order filter circuit is respectively connected to the resistor of the second-order filter circuit and the positive level signal input end of the operational amplifier, and the other end is grounded. The other end of the resistor of the second-order filter circuit is respectively connected to the sampling voltage divider resistor that outputs the positive level signal, the capacitor and the resistor of the first-order filter circuit in parallel, and the switching diode, and the other end of the capacitor and the resistor of the first-order filter circuit in parallel are grounded.

2. The differential multi-channel high-voltage sampling circuit with second-order low-pass filtering according to claim 1 is characterized in that: The switching diode is LBA99WT1G, and the 1st and 2nd pins of the LBA99WT1G switching diode are connected to the positive and negative power supplies respectively, and the 3rd pin is connected to the first-order filtering circuit and the second-order filtering circuit.

3. The differential multi-channel high-voltage sampling circuit with second-order low-pass filtering according to claim 1 is characterized in that: The first-order RC filter is a resistor and a capacitor connected in series. One end of the resistor of the first-order RC filter is connected to the output end of the differential second-order low-pass filter circuit, and the other end is respectively connected to the capacitor of the first-order RC filter, the I / O end of the ESD diode and the input port of the DSP chip. The other end of the capacitor of the first-order RC filter is grounded.

4. The differential multi-channel high-voltage sampling circuit with second-order low-pass filtering according to claim 3 is characterized in that: Pin 2 of the ESD diode is directly connected to REFGND, and pin 5 is connected to REFGND via a preset number of parallel capacitors.

5. The differential multi-channel high-voltage sampling circuit with second-order low-pass filtering according to claim 1, characterized in that: The ESD diode includes 4 I / O terminals, which can be respectively connected to four groups of the first-order RC filters, and the four groups of the first-order RC filters are respectively connected to four groups of the differential second-order low-pass filter circuits and high-voltage sampling circuits to simultaneously realize four-channel high-voltage sampling.

6. The differential multi-channel high-voltage sampling circuit with second-order low-pass filtering according to claim 1, characterized in that: The sampling voltage-dividing resistor is formed by a preset number of high-precision and high-resistance resistors connected in series.

7. The differential multi-channel high-voltage sampling circuit with second-order low-pass filtering according to claim 1, characterized in that: The operational amplifier is connected to power supply voltages of +15V and -15V respectively.

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