Signal conditioning circuit of a partition current detection device on both sides of the cathode and anode

Abstract

The present invention discloses a signal conditioning circuit for a partition current detection device on both sides of the anode and cathode, comprising: a voltage signal conditioning module, and the voltage signal conditioning module includes: an RC input filter circuit, a differential mode amplification circuit, a common mode rejection circuit, a linear voltage regulator, and an RC lag circuit. By adopting the technical solution of the present invention, it is possible to accurately amplify the differential mode signal in the voltage signal output by the partition current detection device of the high-power stack, and at the same time suppress the common mode signal in the voltage signal, thereby improving the accuracy of the partition current detection inside the fuel cell stack and the stability of the detection device.

Description

Technical Field

[0001] The present invention belongs to the technical field of fuel cells, and particularly relates to a signal conditioning circuit for a partition current detection device on both sides of the cathode and anode. Background Art

[0002] As an efficient and clean energy conversion device, fuel cells are increasingly widely used in the fields of transportation, stationary power generation, and portable power supplies. Uneven distribution of reaction gases can lead to problems such as reduced durability of the fuel cell stack, local overheating, and flooding. Therefore, measuring the current density in different partitions inside the fuel cell stack is an important method for optimizing the fuel cell stack.

[0003] However, detecting the partition current density of fuel cells faces many challenges. Especially in high-power application scenarios, it is necessary to solve the problem of signal interference caused by the high common-mode voltage on the cathode side. The common-mode voltage is the same voltage existing on the signal line, and its superposition with the differential-mode signal (i.e., the current signal actually to be measured) will cause measurement errors. Therefore, it is difficult to obtain accurate measurement results using the current detection method of traditional differential amplifiers under high common-mode voltage and strong radio frequency interference, and it cannot meet the requirements for the detection accuracy of the partition current density of high-power fuel cell stacks. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a signal conditioning circuit for a partition current detection device on both sides of the cathode and anode, which can perform high-resolution detection on the partition current density on the cathode and anode sides inside the fuel cell stack, and can achieve high-resolution detection of the partition current in a high common-mode voltage environment, improving the accuracy and stability of current monitoring inside the fuel cell stack.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] A signal conditioning circuit for a partition current detection device on both sides of the cathode and anode, comprising: a voltage signal conditioning module, and the voltage signal conditioning module includes: an RC input filter circuit, a differential-mode amplification circuit, a common-mode rejection circuit, a linear voltage regulator, and an RC lag circuit; wherein,

[0007] The RC input filter is used to eliminate radio frequency interference in the input line;

[0008] The differential-mode amplification circuit is used to amplify the differential-mode signal across the sampling resistor and convert the differential signal across the sampling resistor into a single-ended signal; wherein, the differential signal includes: a high common-mode voltage and a differential-mode signal.

[0009] The common-mode rejection circuit is used to suppress the high common-mode voltage in the single-ended signal and retain the amplified differential-mode signal;

[0010] The linear voltage regulator is used to supply power to the instrumentation amplifier and the differential amplifier;

[0011] The RC lag circuit performs lag compensation on the voltage signal output by the common-mode rejection circuit.

[0012] Preferably, the RC input filter includes: a reverse input resistor, a first filter capacitor, a forward input resistor, a second filter capacitor, and a differential-mode filter capacitor.

[0013] Preferably, the differential-mode amplification circuit includes: an instrumentation amplifier, a gain adjustment resistor, a first positive power supply decoupling capacitor, and a second negative power supply decoupling capacitor.

[0014] Preferably, the common-mode rejection circuit includes: a differential amplifier, a second positive power supply decoupling capacitor, and a second negative power supply decoupling capacitor.

[0015] Preferably, the linear voltage regulator includes: an instrumentation amplifier positive power supply circuit, an instrumentation amplifier negative power supply circuit, a differential amplifier positive power supply circuit, and a differential amplifier negative power supply circuit; wherein, the instrumentation amplifier positive power supply circuit includes: an instrumentation amplifier positive power supply voltage regulator, a first input capacitor, a first output capacitor; the instrumentation amplifier negative power supply circuit includes: an instrumentation amplifier negative power supply voltage regulator, a second input capacitor, a second output capacitor; the differential amplifier positive power supply circuit includes: a differential amplifier positive power supply voltage regulator, a third input capacitor, a third output capacitor; the differential amplifier negative power supply circuit includes: a differential amplifier negative power supply voltage regulator, a fourth input capacitor, a fourth output capacitor.

[0016] Preferably, the RC lag circuit includes: an output resistor and a fifth output capacitor;

[0017] Preferably, the reference grounds of the instrumentation amplifier and its positive and negative power supply voltage regulators are both connected to the negative pole of the sampling resistor in the signal acquisition board.

[0018] Preferably, the reference grounds of the differential amplifier and its positive and negative power supply voltage regulators are both connected to the anode current collector plate of the fuel cell.

[0019] The present invention can accurately amplify the differential-mode signal in the voltage signal output by the anode and cathode partition current detection device of the high-power stack, and at the same time suppress the common-mode signal in the voltage signal, thereby improving the accuracy of the partition current detection inside the fuel cell stack and the stability of the detection device. Description of the Drawings

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other accompanying drawings can also be obtained based on the provided drawings.

[0021] Figure 1 It is the circuit diagram of the signal conditioning circuit of the partition current detection device on both sides of the anode and cathode of the embodiment of the present invention;

[0022] Among them, R0 is the current sampling resistor, 1 is the positive power supply circuit of the instrumentation amplifier, 2 is the positive power supply circuit of the differential amplifier, 3 is the input RC filter circuit, 4 is the differential mode amplification circuit, 5 is the common mode rejection circuit, 6 is the RC lag circuit, 7 is the negative power supply circuit of the instrumentation amplifier, and 8 is the negative power supply circuit of the differential amplifier. Specific embodiments

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0024] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0025] Embodiment 1:

[0026] As Figure 1 shown, the embodiment of the present invention provides a signal conditioning circuit for a partition current detection device on both sides of the anode and cathode, and inputs the voltage signal across the sampling resistor R0 into the signal conditioning circuit through a connecting wire; in the signal conditioning circuit, the differential signal input voltage signal is conditioned into the voltage signal conditioning module by using the traces on the PCB board; the voltage signal conditioning module includes: an RC input filter circuit, a differential mode amplification circuit, a common mode rejection circuit, a linear voltage regulator, and an RC lag circuit; among them, the RC input filter is used to eliminate the radio frequency interference in the input line; the differential mode amplification circuit is used to amplify the differential mode signal across the sampling resistor and convert the differential signal across the sampling resistor into a single-ended signal; among them, the differential signal includes: a high common mode voltage and a differential mode signal; the common mode rejection circuit is used to suppress the high common mode voltage in the single-ended signal and retain the amplified differential mode signal; the linear voltage regulator is used to supply power to the instrumentation amplifier and the differential amplifier; the RC lag circuit performs lag compensation on the voltage signal output by the common mode rejection circuit.

[0027] As an implementation manner of an embodiment of the present invention, the RC input filter includes: a reverse input resistor R1, a first filter capacitor C1, a forward input resistor R4, a second filter capacitor C7, and a differential-mode filter capacitor C4; wherein, one end of the reverse input resistor R1 is connected to one end of the sampling resistor R0, the other end of the sampling resistor R0 is connected to one end of the forward input resistor R4, the other end of the reverse input resistor R1 is connected to the reverse input pin 1 (-IN) of the instrumentation amplifier U1 and is connected to one end of the first filter capacitor C1, and the other end of the first filter capacitor C1 is connected to a floating ground; the other end of the forward input resistor R4 is connected to the forward input pin 4 (+IN) of the instrumentation amplifier U1, the other end of the forward input resistor R4 is connected to one end of the second filter capacitor C7, and the other end of the second filter capacitor C7 is connected to a floating ground; one end of the differential-mode filter capacitor C4 is connected to the other end of the forward input resistor R4 and the forward input pin 4 (+IN) of the instrumentation amplifier U1, and the other end of the differential-mode filter capacitor C4 is connected to the connection between the reverse input resistor R1 and the forward input pin 1 (-IN) of the instrumentation amplifier U1.

[0028] Furthermore, when the signal conditioning circuit is applied in a strong radio frequency interference scenario, the instrumentation amplifier U1 will rectify the radio frequency interference and then show it as a DC output offset error. To suppress this radio frequency interference, an RC input filter circuit is added in the front stage of the instrumentation amplifier U1. The common-mode part in the radio frequency interference signal is filtered by two groups of RC filters, namely R1-C1 and R4-C7, while the differential-mode part is filtered by the parallel connection of R1+R4 and C4 with the series connection of C1 and C7. The cut-off frequency f CM of the common-mode filter is 1 / 2πR1C1, and the cut-off frequency f DIFF of the differential-mode filter is 1 / 2πR1(2C4+C1).

[0029] As an implementation manner of an embodiment of the present invention, the differential-mode amplification circuit includes: an instrumentation amplifier U1, a gain adjustment resistor R2, a first positive power supply decoupling capacitor C17, and a second negative power supply decoupling capacitor C8; wherein, the negative input pin 1 (-IN) of the instrumentation amplifier U1 is connected to the common point of the reverse input resistor R1 and the first filter capacitor C1; the two pins 2 and 3 (RG) of the instrumentation amplifier U1 are respectively connected to both ends of the gain adjustment resistor R2; the positive input pin 4 (+IN) of the instrumentation amplifier U1 is connected to the common point of the forward input resistor R4 and the second filter capacitor C7; the negative power supply pin 5 of the instrumentation amplifier U1 is connected to one end of the capacitor second negative power supply decoupling capacitor C8, and the other end of the second negative power supply decoupling capacitor C8 is connected to a floating ground; the reference pin 6 (REF) of the instrumentation amplifier U1 is connected to the floating ground; the output terminal 7 (VOUT) of the instrumentation amplifier U1 is connected to the positive input pin (+IN) of the differential amplifier U2; the positive power supply pin 8 (+VS) of the instrumentation amplifier U1 is connected to one end of the first positive power supply decoupling capacitor C17, and the other end of the first positive power supply decoupling capacitor C17 is connected to the floating ground.

[0030] Further, the differential-mode amplification circuit amplifies the differential-mode signal in the differential signal across the sampling resistor by a set amplification factor and converts the differential signal into a single-ended signal; the differential-mode amplification circuit includes: an instrumentation amplifier U1, a gain adjustment resistor R2, a first positive power supply decoupling capacitor C17, and a second negative power supply decoupling capacitor C8. The gain adjustment resistor R2 is responsible for adjusting the amplification factor G of the instrumentation amplifier, and the relationship between G and the resistance value R of R2 is G = 1 + 30kΩ / R. The first positive power supply decoupling capacitor C17 and the second negative power supply decoupling capacitor C8 are respectively responsible for filtering the power supply noise of the positive power supply and the negative power supply. The instrumentation amplifier U1 is responsible for amplifying the differential-mode signal in the differential signal and converting the differential signal into a single-ended signal. The instrumentation amplifier consists of two input-stage operational amplifiers A1, A2 and a differential-output-stage operational amplifier A3; the input signals include differential-mode signals and common-mode signals, and A1 and A2 are respectively connected to the differential input terminals to preliminarily amplify the input signals; the amplified signals are transmitted to A3 through the intermediate stage, and A3 performs differential amplification on it to finally obtain a single-ended output signal. The differential voltage signals V in + 、V in - are input into the differential-mode amplification circuit through connecting wires, and the magnitude of the output signal voltage relative to the fuel cell anode is G*(V in + -V in - ) + V ref , where V ref is the voltage value of the reference ground.

[0031] As an implementation manner of an embodiment of the present invention, the common-mode rejection circuit includes: a differential amplifier U2, a second positive power supply decoupling capacitor C3, and a second negative power supply decoupling capacitor C6; wherein, the positive and negative reference pins 1 and 5 (REF(-) and REF(+)) of the differential amplifier U2 are both grounded; the negative input pin 2 (-IN) of the differential amplifier U2 is connected to the floating ground; the positive input pin 3 (+IN) of the differential amplifier U2 is connected to the output pin (VOUT) of the instrumentation amplifier U1; the negative power supply pin 4 (-VS) of the differential amplifier U2 is connected to one end of the second negative power supply decoupling capacitor C6, and the other end of the second negative power supply decoupling capacitor C6 is grounded; the output pin 6 (OUTPUT) of the differential amplifier U2 is connected to one end of the output resistor R3; the positive power supply pin 7 (+VS) of the differential amplifier U2 is connected to one end of the second positive power supply decoupling capacitor C3, and the other end of the second positive power supply decoupling capacitor C3 is grounded.

[0032] Further, the common-mode rejection circuit is used to suppress the high common-mode voltage in the single-ended signal and retain the amplified differential-mode signal. The common-mode rejection circuit is composed of a differential amplifier U2, a second positive power supply decoupling capacitor C3, and a second negative power supply decoupling capacitor C6. Among them, the second positive power supply decoupling capacitor C3 and the second negative power supply decoupling capacitor C6 are respectively responsible for filtering the power supply noise of the positive power supply and the negative power supply. The differential amplifier is responsible for suppressing the high common-mode voltage in the single-ended signal. The specific process is as follows: through the internal resistor voltage division network, the non-inverting input signal is attenuated to a small signal, and the feedback circuit amplifies the differential-mode signal to the required gain, and the gain is usually 1; the precisely matched resistors ensure that the common-mode signal is effectively suppressed, and at the same time, the super-β transistor input level reduces the influence of the input offset current, reducing the drift of the output voltage and the low-frequency noise. The single-ended signal output by the instrumentation amplifier is input to the positive input terminal of the differential amplifier, and the reference output of the instrumentation amplifier is input to the negative input terminal of the differential amplifier. Among them, the voltage of the positive input terminal is G*(V in + -V in - )+V ref , and the voltage of the negative input terminal is V ref . Assuming that the differential-mode gain of the differential amplifier is 1, the final output signal is G*(V in + -V in - ) relative to the voltage value of the fuel cell anode.

[0033] As an implementation manner of an embodiment of the present invention, the linear voltage regulator includes: an instrumentation amplifier positive power supply circuit 1, an instrumentation amplifier negative power supply circuit 7, a differential amplifier positive power supply circuit 2, and a differential amplifier negative power supply circuit 8; wherein, the instrumentation amplifier positive power supply circuit 1 includes: an instrumentation amplifier positive power supply voltage regulator U12, a first input capacitor C9, and a first output capacitor C12; the instrumentation amplifier negative power supply circuit 7 includes: an instrumentation amplifier negative power supply voltage regulator U11, a second input capacitor C11, and a second output capacitor C10; the differential amplifier positive power supply circuit 2 includes: a differential amplifier positive power supply voltage regulator U13, a third input capacitor C13, and a third output capacitor C14; the differential amplifier negative power supply circuit 8 includes: a differential amplifier negative power supply voltage regulator U14, a fourth input capacitor C16, and a fourth output capacitor C15; wherein, the input pin 1 (IN) of the instrumentation amplifier positive power supply voltage regulator U12 is connected to the common point of +12VIN and the first input capacitor C9, the ground pins 2 and 4 (GND) of the instrumentation amplifier positive power supply voltage regulator U12 are connected to a floating ground, the output pin 3 (OUT) of the instrumentation amplifier positive power supply voltage regulator U12 is connected to one end of the first output capacitor C12, and the other ends of the first input capacitor C9 and the first output capacitor C12 are both grounded; the input pins 2 and 4 (IN) of the instrumentation amplifier negative power supply voltage regulator U11 are connected to the common point of -12VIN and the second input capacitor C11, the ground pin 1 (GND) of the instrumentation amplifier negative power supply voltage regulator is grounded, the output pin 3 (OUT) of the instrumentation amplifier negative power supply voltage regulator is connected to one end of the second output capacitor C10, and the other ends of the second input capacitor C11 and the second output capacitor C10 are both connected to a floating ground; the input pin 1 (IN) of the differential amplifier positive power supply voltage regulator U13 is connected to the common point of +12VIN and the third input capacitor C13, the ground pins 2 and 4 (GND) of the differential amplifier positive power supply voltage regulator U13 are grounded, the output pin 3 (OUT) of the differential amplifier positive power supply voltage regulator U13 is connected to one end of the third output capacitor C14, and the other ends of the third input capacitor C13 and the third output capacitor C14 are both grounded; the input pins 2 and 4 (IN) of the differential amplifier negative power supply voltage regulator U14 are connected to the common point of -12VIN and the fourth input capacitor C16, the ground pin 1 (GND) of the differential amplifier negative power supply voltage regulator U14 is grounded, the output pin 3 (OUT) of the differential amplifier negative power supply voltage regulator U14 is connected to one end of the fourth output capacitor C15, and the other ends of the fourth input capacitor C16 and the fourth output capacitor C15 are both grounded. During actual use, a suitable linear voltage regulator needs to be selected according to the common-mode input range and output voltage range of the instrumentation amplifier.

[0034] As an implementation manner of an embodiment of the present invention, the RC lag circuit includes: an output resistor R3 and a fifth output capacitor C5; wherein, one end of the output resistor R3 is connected to the output pin (OUTPUT) of the differential amplifier U2, and the other end is connected to the output terminal UOUT and one end of the fifth output capacitor C5, and the other end of the fifth output capacitor C5 is grounded. The final phase shift angle θ of the RC lag circuit is θ = arctan(1 / 2πfR3C5).

[0035] As an implementation manner of an embodiment of the present invention, the reference grounds of the instrumentation amplifier U1 and its positive and negative power supply regulators U11, U12 are both connected to the negative pole of the sampling resistor in the signal acquisition board. The reference grounds of the differential amplifier U2 and its positive and negative power supply regulators U13, U14 are both connected to the anode current collector plate of the fuel cell.

[0036] When detecting the cathode partition current density, due to the existence of a high common-mode voltage on the cathode side relative to the anode side, the reference ground of the instrumentation amplifier U1 should be connected to the cathode current collector plate of the instrumentation amplifier, that is, connected to the negative pole of the sampling resistor R0. Otherwise, the input common-mode voltage will be equal to the fuel cell output voltage value, which is much larger than the voltage range allowed by the instrumentation amplifier U1, resulting in damage to the instrumentation amplifier.

[0037] When the data acquisition board is placed on the cathode or anode, the current direction flowing through the sampling resistor R0 is different, resulting in the voltage signal being input to the instrumentation amplifier with positive and negative swings. At this time, the instrumentation amplifier U1 can output with positive and negative swings, so the instrumentation amplifier U1 is powered by positive and negative power supplies.

[0038] The above-described embodiments are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention should fall within the protection scope determined by the claims of the present invention.

Claims

1. A signal conditioning circuit for a partition current detection device on both sides of the anode and cathode, characterized in that, Comprising: A voltage signal conditioning module, the voltage signal conditioning module comprising: an RC input filter circuit, a differential mode amplifier circuit, a common mode rejection circuit, a linear voltage regulator, and an RC lag circuit; wherein, An RC input filter for eliminating radio frequency interference in the input line; A differential mode amplifier circuit for amplifying the differential mode signal across the sampling resistor and converting the differential signal across the sampling resistor into a single-ended signal; wherein, the differential signal includes: a high common mode voltage and a differential mode signal; A common mode rejection circuit for suppressing the high common mode voltage in the single-ended signal and retaining the amplified differential mode signal; The linear voltage regulator is used to supply power to the instrumentation amplifier and the differential amplifier; The RC lag circuit performs lag compensation on the voltage signal output by the common mode rejection circuit; The RC input filter includes: a reverse input resistor, a first filter capacitor, a forward input resistor, a second filter capacitor, and a differential mode filter capacitor; The differential mode amplifier circuit includes: an instrumentation amplifier, a gain adjustment resistor, a first positive power supply decoupling capacitor, and a second negative power supply decoupling capacitor; The common mode rejection circuit includes: a differential amplifier, a second positive power supply decoupling capacitor, and a second negative power supply decoupling capacitor; The single-ended signal output by the instrumentation amplifier goes to the positive input terminal of the differential amplifier, and pin 6 of the instrumentation amplifier is connected to the negative input terminal of the differential amplifier; Pin 6 of the instrumentation amplifier, pin 1 of the positive and negative power supply voltage regulator U11, pins 2 and 4 of the positive power supply voltage regulator U12 for the instrumentation amplifier are all connected to the negative pole of the sampling resistor in the signal acquisition board; Pins 1 and 5 of the differential amplifier, pins 2 and 4 of the positive and negative power supply voltage regulator U13, and pin 1 of the negative power supply voltage regulator U14 for the differential amplifier are all connected to the anode current collector plate of the fuel cell; When detecting the cathode partition current density, due to the existence of a high common mode voltage on the cathode side relative to the anode side, pin 6 of the instrumentation amplifier U1 is connected to the cathode current collector plate, that is, connected to the negative pole of the sampling resistor R0.

2. The signal conditioning circuit of the partition current detection device on both sides of the anode and cathode according to claim 1, wherein The linear voltage regulator includes: a positive power supply circuit for the instrumentation amplifier, a negative power supply circuit for the instrumentation amplifier, a positive power supply circuit for the differential amplifier, and a negative power supply circuit for the differential amplifier; wherein, the positive power supply circuit for the instrumentation amplifier includes: a positive power supply voltage regulator for the instrumentation amplifier, a first input capacitor, and a first output capacitor; the negative power supply circuit for the instrumentation amplifier includes: a negative power supply voltage regulator for the instrumentation amplifier, a second input capacitor, and a second output capacitor; the positive power supply circuit for the differential amplifier includes: a positive power supply voltage regulator for the differential amplifier, a third input capacitor, and a third output capacitor; the negative power supply circuit for the differential amplifier includes: a negative power supply voltage regulator for the differential amplifier, a fourth input capacitor, and a fourth output capacitor.

3. The signal conditioning circuit of the partition current detection device on both sides of the anode and cathode according to claim 2, characterized in that The RC lag circuit includes: an output resistor and a fifth output capacitor.

Images