CN117310514A - Voltage detection circuit for fuel cell diagnosis - Google Patents
Voltage detection circuit for fuel cell diagnosis Download PDFInfo
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- 239000000446 fuel Substances 0.000 title claims abstract description 58
- 238000001514 detection method Methods 0.000 title claims abstract description 39
- 238000003745 diagnosis Methods 0.000 title claims description 16
- 238000012545 processing Methods 0.000 claims abstract description 31
- 238000005070 sampling Methods 0.000 claims abstract description 28
- 238000002955 isolation Methods 0.000 claims abstract description 15
- 238000004364 calculation method Methods 0.000 claims abstract description 12
- 239000003990 capacitor Substances 0.000 claims description 52
- 230000000903 blocking effect Effects 0.000 claims description 12
- 230000001066 destructive effect Effects 0.000 claims description 10
- 230000009977 dual effect Effects 0.000 claims description 9
- 230000001052 transient effect Effects 0.000 claims description 9
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- 230000003321 amplification Effects 0.000 claims description 2
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 2
- 238000001914 filtration Methods 0.000 abstract description 18
- 238000012216 screening Methods 0.000 abstract description 5
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- 238000000157 electrochemical-induced impedance spectroscopy Methods 0.000 description 6
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- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 3
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- 238000005516 engineering process Methods 0.000 description 3
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/36—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC]
- G01R31/378—Arrangements for testing, measuring or monitoring the electrical condition of accumulators or electric batteries, e.g. capacity or state of charge [SoC] specially adapted for the type of battery or accumulator
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
- G01R19/2506—Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values ; Details concerning sampling, digitizing or waveform capturing
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
- G01R19/25—Arrangements for measuring currents or voltages or for indicating presence or sign thereof using digital measurement techniques
- G01R19/2506—Arrangements for conditioning or analysing measured signals, e.g. for indicating peak values ; Details concerning sampling, digitizing or waveform capturing
- G01R19/2509—Details concerning sampling, digitizing or waveform capturing
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Abstract
The voltage detection circuit is connected with the output end of the diagnosed fuel cell, wherein the voltage detection circuit comprises a high-voltage side filter processing circuit and a low-voltage side filter processing circuit, the high-voltage side filter processing circuit is connected with the low-voltage side filter processing circuit through a differential isolation operational amplifier circuit, the input end of the high-voltage side filter processing circuit is connected with a high-voltage sampling node of the fuel cell, and the low-voltage side filter processing circuit is connected with a controller impedance calculation unit. Under the condition that the interference noise is larger than the useful alternating current signal in the high-voltage circuit of the system, the high-quality useful alternating current voltage signal is acquired through measures such as signal filtering and frequency screening, and is processed to carry out impedance calculation on the DSP control unit, so that high-precision voltage sampling is realized.
Description
Technical Field
The present invention relates to the field of fuel cell diagnosis, and in particular, to a voltage detection circuit for fuel cell diagnosis.
Background
Fuel cells have been widely studied in recent years as an environmentally friendly and energy conversion-efficient device, and are essentially devices that convert chemical energy of hydrogen into electric energy by generating electrons and ions from hydrogen and oxygen through electrochemical reactions using hydrogen as a fuel. Fuel cells are widely used in the fields of automobiles, industry, electric power, aerospace, etc., but the stability and life problems thereof have been one of the main factors restricting the application thereof.
To solve this problem, EIS (Electrochemical ImpedanceSpectroscopy) impedance detection technology is proposed and applied to fuel cells. EIS is a technology for measuring and diagnosing internal resistance of a fuel cell, and the detection principle is based on interaction of alternating current electricity and chemical reaction, and the internal electrochemical reaction of the fuel cell is scanned in frequency by injecting alternating current signals into the fuel cell, and electrochemical impedance spectrum of the fuel cell is measured by calculating parameters such as complex impedance and the like so as to evaluate the stability and the expected service life of the internal characteristic of the fuel cell. The internal resistance of the fuel cell is characterized by low nonlinear dynamic impedance, severe working environment, serious electromagnetic interference, limited detection and diagnosis means and difficult assessment.
Most of the prior art focuses on how to realize the internal resistance detection method and the calculation algorithm of EIS detection, but how to obtain high-precision detection is always a technical difficulty aiming at the sampling realization process of specific signals. This is because: 1) The operating environment of the fuel cell system is severely electromagnetic; 2) In order to improve efficiency, the internal resistance of the fuel cell is usually milliohm, so that the detection difficulty is high; 3) Injecting an excitation current which does not affect the normal operation of the system through an EIS detection means, wherein a voltage signal responded on milliohm level internal resistance of the excitation current is only millivolt level; 4) In a complex electromagnetic environment, the interference noise is larger than that of an effective signal, and the weak effective signal is easily covered to cause signal distortion, so that the detection accuracy is affected. Therefore, how to handle noise is a difficult problem in designing the whole sampling detection circuit, and is also a key point in determining whether the EIS detection is accurate or not.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a voltage detection circuit for fuel cell diagnosis aiming at the defects existing in the prior art.
The technical scheme adopted for solving the technical problems is as follows: the voltage detection circuit is connected with the output end of the diagnosed fuel cell, wherein the voltage detection circuit comprises a high-voltage side filter processing circuit and a low-voltage side filter processing circuit, the high-voltage side filter processing circuit is connected with the low-voltage side filter processing circuit through a differential isolation operational amplifier circuit, the input end of the high-voltage side filter processing circuit is connected with a high-voltage sampling node of the fuel cell, and the low-voltage side filter processing circuit is connected with a controller impedance calculation unit.
Under the condition that the interference noise is larger than the useful alternating current signal in the high-voltage circuit of the system, the high-quality useful alternating current voltage signal is acquired through measures such as signal filtering and frequency screening, and is processed to carry out impedance calculation on the DSP control unit, so that high-precision voltage sampling is realized.
Preferably, the high-voltage side filtering processing circuit comprises an RC high-pass filtering circuit, an LC band-pass filtering circuit and an RC low-pass filtering circuit which are connected in sequence.
Preferably, the RC high-pass filter circuit is connected to the high-voltage sampling node through a nondestructive shielding connection unit, the RC high-pass filter circuit is connected with the LC band-pass filter circuit, a transient suppression protection circuit is arranged at the output end of the LC band-pass filter circuit, and a T-shaped resistance attenuation network is arranged between the transient suppression protection circuit and the RC low-pass filter circuit.
Preferably, the nondestructive shielding connection unit is a nondestructive shielding wire harness, one end of the nondestructive shielding wire harness is connected with the high-voltage sampling node, and the other end of the nondestructive shielding wire harness is connected with the RC high-pass filter circuit. Because the output end of the fuel cell system is connected with the detection unit by a long-distance wire harness, the electromagnetic noise in the fuel cell system is serious, and therefore, the nondestructive shielding wire harness is used for connection, so that the influence of electromagnetic interference on an initial signal is reduced.
Preferably, the input end of the RC high-pass filter circuit is respectively provided with a high-voltage blocking capacitor, and the direct-current component of the output end of the fuel cell collected by the nondestructive shielding wire harness is isolated to obtain the alternating-current component on the direct-current output of the fuel cell. The direct current component of the fuel cell end is isolated to obtain a clean pure alternating current voltage signal.
Preferably, the LC band-pass filter circuit is a dual band-pass filter composed of an LC low-pass filter circuit and an RC high-pass filter circuit, and comprises differential-mode filter inductors L301-L302, capacitors C330-C335, a resistor R312 and a resistor R326, wherein the differential-mode filter inductor L301 is connected in series with the capacitor C330, the differential-mode filter inductor L302 is connected in series with the capacitor C331 so as to form an LC low-pass filter circuit, the capacitor C332, the capacitor C333, the capacitor C334 and the capacitor C335 are bridged and then form an RC high-pass filter circuit with the resistor R312 and the resistor R326, and the output of the LC low-pass filter circuit is connected with the RC high-pass filter circuit so as to form the LC band-pass filter with specific frequency. The first-order high-pass RC filter is adopted to filter low-frequency interference noise, and for high-frequency interference noise, the double-band-pass filter consisting of the LC low-pass filter circuit and the RC high-pass filter circuit is adopted, a band-pass filter consisting of a group of proper LCR parameters is selected to filter specific frequencies in differential signals, inductance reactance and capacitance reactance are mutually counteracted under resonance frequency, namely only useful signals under resonance frequency can pass.
Preferably, the T-shaped resistor attenuation network comprises resistors R309-R312 and resistors R326-R327, wherein the resistor R309 is connected with the resistor R312, the resistor R310 is connected with the resistor R327, one end of the resistor R312 is connected with the resistor R309 and the resistor R312 after being connected in series, and the other end of the resistor R312 is connected with the resistor R326 after being connected in series, so that the double-T-shaped attenuator unit is formed. The double T-shaped attenuator unit is used for adjusting the signal size, improving impedance matching, controlling the attenuation accurately and having better linear regulation characteristic in a specific frequency range.
Preferably, the RC low-pass filter circuit includes a resistor R314, a resistor R315, and a filter capacitor C318, where the filter capacitor C318 is connected across the resistor R314 and the resistor R315 to form a dual low-pass RC filter circuit. The adjusted differential signal is placed at the front end of the isolated operational amplifier input through a double-low-pass RC filter circuit consisting of a filter resistor R314, a resistor R315 and a filter capacitor C318, so that the performance of differential signal noise in a signal transmission path is improved.
Preferably, the low-voltage side filtering processing circuit comprises a bias voltage operational amplifier circuit, a proportional operational amplifier circuit and an AD sampling unit which are connected in sequence.
Preferably, the bias voltage operational amplifier circuit includes an operational amplifier U303, resistors are respectively disposed at the positive input end and the negative input end of the operational amplifier U303, and a pull-up resistor and a capacitor are disposed at the positive input end of the operational amplifier U303 and connected to the bias voltage V ref The negative input end of the operational amplifier U303 is connected to the output end of the operational amplifier U303 through a feedback resistor R319 and a capacitor C324 to form a negative feedback operational amplifier circuit.
Compared with the prior art, the invention has the advantages that: under the condition that the interference noise is larger than the useful alternating current signal in the high-voltage circuit of the system, the high-quality useful alternating current voltage signal is acquired through measures such as signal filtering and frequency screening, and is processed to carry out impedance calculation on the DSP control unit, so that high-precision voltage sampling is realized. The response voltage caused by the exciting current injected into the fuel cell can be accurately sampled, the detection circuit is convenient to use and easy to realize in engineering, the application cost is effectively reduced, and the economic applicability is strong.
Drawings
FIG. 1 is a schematic block diagram of a circuit according to an embodiment of the present invention;
FIG. 2 is a sampling flow chart of an embodiment of the present invention;
FIG. 3 is a schematic circuit diagram of an embodiment of the present invention;
fig. 4 is an equivalent diagram of a T-type circuit in a schematic circuit diagram according to an embodiment of the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals refer to the same or similar elements or elements having the same or similar functions.
In the description of the present invention, it should be understood that the terms "center," "longitudinal," "transverse," "length," "width," "thickness," "up," "down," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," etc. indicate orientations or positional relationships based on the orientation or positional relationships shown in the drawings, merely to facilitate description of the present invention and simplify description, rather than to indicate or imply that the devices or elements being referred to must have a particular orientation, be configured and operated in a particular orientation, and that these directional terms are not to be considered limiting, such as "up," "down" are not necessarily limited to directions opposite or coincident with the direction of gravity, since the disclosed embodiments of the present invention may be arranged in different orientations. Furthermore, features defining "first", "second" may include one or more such features, either explicitly or implicitly.
Examples:
the voltage detection circuit disclosed in this embodiment is connected with the output end of the diagnosed fuel cell, and is characterized in that the voltage detection circuit comprises a high-voltage side filtering processing circuit and a low-voltage side filtering processing circuit, the high-voltage side filtering processing circuit is connected with the low-voltage side filtering processing circuit through a differential isolation operational amplifier circuit, the input end of the high-voltage side filtering processing circuit is connected with a high-voltage sampling node of the fuel cell, and the low-voltage side filtering processing circuit is connected with a controller impedance calculation unit. The voltage detection circuit also comprises an isolation auxiliary power circuit connected with the auxiliary direct-current power supply. Under the condition that the interference noise is larger than the useful alternating current signal in the high-voltage circuit of the system, the high-quality useful alternating current voltage signal is acquired through measures such as signal filtering and frequency screening, and is processed to carry out impedance calculation on the DSP control unit, so that high-precision voltage sampling is realized.
As shown in fig. 1, in this embodiment, the voltage detection circuit 11 is connected to the output end of the diagnosed fuel cell, and the high-voltage side filter processing circuit 12 includes an RC high-pass filter circuit, an LC band-pass filter circuit, and an RC low-pass filter circuit, which are sequentially connected. The low-voltage side filter processing circuit 13 comprises a bias voltage operational amplifier circuit, a proportional operational amplifier circuit and an AD sampling unit which are sequentially connected.
In the implementation process of this embodiment, the RC high-pass filter circuit is connected to the high-voltage sampling node through a lossless shielding connection unit, the RC high-pass filter circuit is connected to the LC band-pass filter circuit, a transient suppression protection circuit is disposed at an output end of the LC band-pass filter circuit, and a T-type resistor attenuation network is disposed between the transient suppression protection circuit and the RC low-pass filter circuit. The output end of the RC low-pass filter circuit is used as the output end of the high-voltage side filter processing circuit, the output end of the RC low-pass filter circuit is connected with the input end of the differential isolation operational amplifier circuit, the output end of the differential isolation operational amplifier circuit is connected with the input end of the offset voltage operational amplifier circuit, the output end of the offset voltage operational amplifier circuit is connected with the input end of the proportional operational amplifier circuit, and the output end of the proportional operational amplifier circuit is connected with the AD sampling unit. The connection sequence of the module circuits is also a flow chart of sampling signals of the units where the module circuits are located, and is specifically shown in fig. 2.
The specific implementation circuit of this embodiment is shown in fig. 3, specifically, the RC high-pass filter circuit is connected to the high-voltage sampling node through a non-destructive shielding connection unit, the non-destructive shielding connection unit is a non-destructive shielding wire harness, one end of the non-destructive shielding wire harness is connected to the high-voltage sampling node, and the other end of the non-destructive shielding wire harness is connected to the RC high-pass filter circuit. Because the output end of the fuel cell system is connected with the detection unit by a long-distance wire harness, the electromagnetic noise in the fuel cell system is serious, and therefore, the nondestructive shielding wire harness is used for connection, so that the influence of electromagnetic interference on an initial signal is reduced.
In the present embodiment, for the RC high-pass filter circuit: the voltage response is an ac component superimposed on the dc output of the fuel cell, so that it is necessary to connect the signal collected by the lossless harness to the high voltage dc blocking capacitor to isolate the dc component at the fuel cell end, so as to obtain a clean, pure ac voltage signal. Wherein the equivalent impedance of the blocking capacitor isThe blocking capacitor and the equivalent impedance output by the rear end form a double RC high-pass filter circuit, and the calculation formula of the equivalent output gain is as follows:
the larger the capacitance value of the blocking capacitor is, the smaller the capacitance reactance is, and the larger the gain of the output high-frequency alternating current signal is. The scheme selects a group of blocking capacitors with proper capacitance values to isolate low-frequency interference noise at the input end, so as to obtain better low-frequency cut-off frequency characteristics.
Specifically, the signals collected by the nondestructive wire harness are connected to the high-voltage blocking capacitors C307 and C317, and the direct-current components at the fuel cell end are isolated, so that clean pure alternating-current voltage signals are obtained. Based on the high voltage of the fuel cell being within 600V, the blocking capacitance takes a value of 0.22uF, and the equivalent impedance is as follows:
wherein C is the value of the blocking capacitor, and f is the frequency constant value. In the experimental case, a 600Hz frequency point is selected, a double RC high-pass filter circuit is formed by the blocking capacitor and the rear end output equivalent impedance, the larger the capacitance value of the blocking capacitor is, the smaller the capacitance resistance is, the larger the output high-frequency alternating current signal gain is, and the equivalent output gain is calculated as:
wherein: r is equivalent impedance and consists of harness matching impedance. R was chosen to be approximately 75 ohms in this experimental case.
In the present embodiment, for the LC band pass filter circuit: a first-order high-pass RC filter is adopted to filter low-frequency interference noise, and for high-frequency interference noise, a double-band-pass filter consisting of an LC low-pass filter circuit and an RC high-pass filter circuit is adopted to select a band-pass filter consisting of a group of proper LCR parameters to filter specific frequencies in differential signals. The differential mode filter inductor is a bandpass filter which is formed by combining a special custom-made amorphous material magnetic ring inductor and a capacitor and has specific frequency, and can filter non-key signals and interference noise in the fuel cell system. The gain calculation formula is as follows:
(wherein->X L ＝jωL)
At the resonant frequency, the inductive reactance and the capacitive reactance cancel each other, i.e. the signal at the resonant frequency can pass through the bandpass filter circuit for a specific frequency.
Specifically, the LC band-pass filter circuit is a dual band-pass filter composed of an LC low-pass filter circuit and an RC high-pass filter circuit, and comprises differential-mode filter inductors L301-L302, capacitors C330-C335, a resistor R312 and a resistor R326, wherein the differential-mode filter inductor L301 is connected in series with the capacitor C330, the differential-mode filter inductor L302 is connected in series with the capacitor C331 so as to form an LC low-pass filter circuit, the capacitor C332, the capacitor C333, the capacitor C334 and the capacitor C335 are bridged and then form an RC high-pass filter circuit with the resistor R312 and the resistor R326, and the output of the LC low-pass filter circuit is connected with the RC high-pass filter circuit so as to form the LC band-pass filter with specific frequency.
A frequency bin of 600Hz was selected in the experimental case, wherein: l301=l302=12mh, c330=c331=2.2uf, c334=c335=2.2uf, r312=r326=1kΩ, and the calculated band pass filter circuit broadband frequency is 72Hz<f BW <980Hz. Band pass filtering is performed in accordance with the 600HZ frequency point range.
In the present embodiment, for the transient suppression protection circuit: the input end is high voltage and the detection control end is low voltage, in order to avoid the influence of transient impulse voltage on a back-end circuit, a TVS transient protection unit is inserted into the LC band-pass filter circuit, the influence of impulse voltage on a back-end sensitive circuit is reduced, and the reliability is improved.
In this embodiment, for a T-type resistive damping network: the filtered differential signal is connected to a dual T-type attenuator cell consisting of resistors. The method is used for adjusting the signal size, improving impedance matching, controlling the attenuation more accurately and having better linear regulation characteristic in a specific frequency range. The equivalent model of the T-shaped circuit is shown in figure 4. According to the T-type network, the signals can be attenuated under the condition of not affecting the matching characteristics, namely the input and output characteristic impedance of the voltage signals are Z 0 R can be calculated A 、R B And R is C Is the value of (1):
t-network delta gain:
specifically, in this embodiment, the T-type resistor attenuation network includes resistors R309-R312 and resistors R326-R327, where the resistor R309 is connected to the resistor R312, the resistor R310 is connected to the resistor R327, one end of the resistor R312 is connected to the connection between the resistor R309 and the resistor R312 after being connected in series with the resistor R326, and the other end of the resistor R312 is connected to the connection between the resistor R310 and the resistor R327 after being connected in series with the resistor R326, thereby forming a dual T-type attenuator unit. The double T-shaped attenuator unit is used for adjusting the signal size, improving impedance matching, controlling the attenuation accurately and having better linear regulation characteristic in a specific frequency range.
Here, the value r309=r310=10kΩ, r311=r312=r326=r327=1kΩ, and r313=51Ω. T-network delta gain:
wherein R309 and R310 correspond to R A R312 and R327 are equivalent to R B R313 is R L 。
In this embodiment, for the RC low-pass filter circuit, the adjusted differential signal is placed at the front end of the isolated op-amp input through the dual low-pass RC filter circuit formed by the filter capacitor and the filter resistor, so as to improve the performance of the differential signal noise in the signal transmission path, and the following conditions are satisfied: the cut-off frequency of the RC filter circuit is at least an order of magnitude lower than the back-end delta sigma modulator.
Specifically, the RC low-pass filter circuit includes a resistor R314, a resistor R315, and a filter capacitor C318, where the filter capacitor C318 is connected across the resistor R314 and the resistor R315 to form a dual low-pass RC filter circuit, and the cut-off frequency of the RC low-pass filter circuit is at least an order of magnitude lower than that of the back-end ΔΣ modulator. The adjusted differential signal is placed at the front end of the isolated operational amplifier input through a double-low-pass RC filter circuit consisting of a filter resistor R314, a resistor R315 and a filter capacitor C318, so that the performance of differential signal noise in a signal transmission path is improved.
In this embodiment, regarding the differential isolation operational amplifier circuit: the differential input signal is connected to the input end of the isolated differential operational amplifier circuit, and the isolated transmission unit isolates the high voltage end from the low voltage end. The circuit adopts an enhanced electric isolation type precision amplifier, which can separate an output circuit from an input circuit by an isolation layer with extremely strong electromagnetic interference resistance, and an isolation grid can separate devices running at different common-mode voltage levels in a system so as to protect low-voltage side devices from high-voltage impact. The isolation operational amplifier adopts differential analog input, is modulated into a high-frequency digital signal through OOK (On-off keying), and is transmitted to a receiving end through a capacitance isolation unit, and the receiving end outputs an analog signal after passing through a signal restoration modulation unit and a multi-stage analog filter. The isolation transmission adopts digital, so that signal distortion is avoided, and signal transmission precision is improved. The high-frequency transmission and switching buffer technology is adopted to realize the low EMC (Electromagnetic Compatibility electromagnetic compatibility) performance of high common mode rejection ratio transmission.
In the present embodiment, regarding the bias voltage operational amplification circuit: the circuit comprises an operational amplifier U303, wherein a resistor R316 and a resistor R317 are respectively arranged at a positive input end and a negative input end of the operational amplifier U303, and the operational amplifier U303 is positiveThe input end is provided with a pull-up resistor R318 and a capacitor C323 to a bias voltage V r f The negative input end of the operational amplifier U303 is connected to the output end of the operational amplifier U303 through a feedback resistor R319 and a capacitor C324 to form a negative feedback operational amplifier circuit. Under the condition of single power supply, according to kirchhoff current law and the virtual break characteristic of an ideal operational amplifier input end, an alternating current signal passes through a bias voltage V ref Then, according to the signal superposition theorem, the output signals are as follows:
specifically, in this embodiment, the auxiliary power supply unit as the whole voltage sampling circuit comprises an isolated 5V power supply and a reference voltage source V ref And a 3.3V/5V DSP power supply.
In this embodiment, the scaling operation amplifying circuit is a proportional operation amplifying circuit. The output voltage signal after the bias voltage is connected to R320, then connected to the input positive terminal of the operational amplifier U304, the resistor R322 and the capacitor C326 are grounded through the positive terminal. The negative terminal is grounded through R321, a feedback resistor R323, a capacitor C327 is connected to the output terminal from the negative terminal, an output signal is connected to an RC filter circuit consisting of R324 and C329, signal distortion caused by output overshoot and the like is prevented, and D303 is a port protection circuit. According to kirchhoff's current law and the virtual break characteristic of an ideal operational amplifier input end, the scaling circuit outputs signals:
in the invention, devices such as passive resistor, capacitor, inductor, isolation operational amplifier and the like are adopted, the complexity is low, the cost is low, the engineering implementation in products is convenient, and meanwhile, the effective filtering of interference noise stronger than useful signals in a fuel cell system is realized by matching and optimizing the combination of circuit structures and parameters, so that the response voltage signal with complete sampling and high quality is obtained. Through repeated system test and comparison verification, the system has the advantages of high signal integrity, good signal quality, strong anti-interference capability and good robustness. The circuit is applied to a fuel cell output high-voltage system, a tiny alternating current response voltage signal is collected and transmitted to a DSP end in an isolated lossless manner, and high-precision AD sampling is completed.
The invention relates to a voltage detection circuit for fuel cell diagnosis. An excitation disturbance current signal generated by a harmonic current of a DC-DC control module in a fuel cell system is detected, and is injected into the system, and an alternating current response voltage signal generated at the internal impedance of the fuel cell is detected. The response alternating voltage signal superposed on the high voltage output end of the fuel cell is weak, and needs to be filtered and amplified, and then sent to the DSP for AD sampling and impedance calculation. Compared with the prior art, the invention has the advantages that: under the condition that the interference noise is larger than the useful alternating current signal in the high-voltage circuit of the system, the high-quality useful alternating current voltage signal is acquired through measures such as signal filtering and frequency screening, and is processed to carry out impedance calculation on the DSP control unit, so that high-precision voltage sampling is realized. The response voltage caused by the exciting current injected into the fuel cell can be accurately sampled, the detection circuit is convenient to use and easy to realize in engineering, the application cost is effectively reduced, and the economic applicability is strong.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (10)
1. The voltage detection circuit for fuel cell diagnosis is connected with the output end of a diagnosed fuel cell, and is characterized by comprising a high-voltage side filter processing circuit and a low-voltage side filter processing circuit, wherein the high-voltage side filter processing circuit is connected with the low-voltage side filter processing circuit through a differential isolation operational amplifier circuit, the input end of the high-voltage side filter processing circuit is connected with a high-voltage sampling node of the fuel cell, and the low-voltage side filter processing circuit is connected with a controller impedance calculation unit.
2. The voltage detection circuit for fuel cell diagnosis according to claim 1, wherein the high-voltage side filter processing circuit includes an RC high-pass filter circuit, an LC band-pass filter circuit, and an RC low-pass filter circuit connected in this order.
3. The voltage detection circuit for fuel cell diagnosis according to claim 2, wherein the RC high-pass filter circuit is connected to the high-voltage sampling node through a non-destructive shielding connection unit, the RC high-pass filter circuit is connected to the LC band-pass filter circuit, an output end of the LC band-pass filter circuit is provided with a transient suppression protection circuit, and a T-type resistance attenuation network is provided between the transient suppression protection circuit and the RC low-pass filter circuit.
4. The voltage detection circuit for fuel cell diagnosis according to claim 3, wherein the non-destructive shielding connection unit is a non-destructive shielding wire harness, one end of the non-destructive shielding wire harness is connected to the high-voltage sampling node, and the other end of the non-destructive shielding wire harness is connected to the RC high-pass filter circuit.
5. The voltage detection circuit for fuel cell diagnosis according to claim 4, wherein the input end of the RC high-pass filter circuit is provided with high-voltage blocking capacitors respectively, and the dc components of the output end of the fuel cell collected by the nondestructive shielding harness are isolated to obtain ac components on the dc output of the fuel cell.
6. The voltage detection circuit for fuel cell diagnosis according to claim 4, wherein the LC band-pass filter circuit is a dual band-pass filter composed of an LC low-pass filter circuit and an RC high-pass filter circuit, and comprises differential-mode filter inductors L301-L302, capacitors C330-C335, a resistor R312 and a resistor R326, the differential-mode filter inductor L301 is connected in series with the capacitor C330, the differential-mode filter inductor L302 is connected in series with the capacitor C331 so as to form the LC low-pass filter circuit, the capacitor C332, the capacitor C333, the capacitor C334 and the capacitor C335 are connected in bridge connection, and then the capacitor C is connected with the resistor R312 and the resistor R326 so as to form the RC high-pass filter circuit, and the output of the LC low-pass filter circuit is connected with the RC high-pass filter circuit so as to form the LC band-pass filter with a specific frequency.
7. The voltage detection circuit for fuel cell diagnosis according to claim 4, wherein the T-type resistor attenuation network comprises resistors R309-R312 and resistors R326-R327, the resistor R309 is connected with the resistor R312, the resistor R310 is connected with the resistor R327, one end of the resistor R312 connected in series with the resistor R326 is connected with the junction of the resistor R309 and the resistor R312, and the other end of the resistor R312 connected in series with the resistor R326 is connected with the junction of the resistor R310 and the resistor R327, thereby forming a double T-type attenuator unit.
8. The voltage detection circuit for fuel cell diagnostics according to claim 4 wherein the RC low pass filter circuit comprises a resistor R314, a resistor R315 and a filter capacitor C318, the filter capacitor C318 being connected across the resistor R314 and the resistor R315 to form a dual low pass RC filter circuit.
9. The voltage detection circuit for fuel cell diagnosis according to claim 1, wherein the low-voltage side filter processing circuit includes a bias voltage operational amplifier circuit, a proportional operational amplifier circuit, and an AD sampling unit, which are connected in this order.
10. The voltage detection circuit for fuel cell diagnosis according to claim 9, wherein the bias voltage operational amplification circuit comprises an operational amplifier U303, resistors are provided at both the positive input terminal and the negative input terminal of the operational amplifier U303, and a pull-up resistor is provided at the positive input terminal of the operational amplifier U303And a capacitor connected to the bias voltageThe negative input end of the operational amplifier U303 is connected to the output end of the operational amplifier U303 through a feedback resistor R319 and a capacitor C324 to form a negative feedback operational amplifier circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311447953.8A CN117310514A (en) | 2023-11-02 | 2023-11-02 | Voltage detection circuit for fuel cell diagnosis |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311447953.8A CN117310514A (en) | 2023-11-02 | 2023-11-02 | Voltage detection circuit for fuel cell diagnosis |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN117310514A true CN117310514A (en) | 2023-12-29 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202311447953.8A Pending CN117310514A (en) | 2023-11-02 | 2023-11-02 | Voltage detection circuit for fuel cell diagnosis |
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| Country | Link |
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| CN (1) | CN117310514A (en) |
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2023
- 2023-11-02 CN CN202311447953.8A patent/CN117310514A/en active Pending
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