Self-powered methanol concentration sensing system for direct methanol fuel cells

Abstract

A self-powered methanol concentration sensing system for a direct methanol fuel cell belongs to the technical field of methanol concentration sensing for fuel cells. The present invention is proposed to address the problem that existing methanol concentration sensors cannot achieve self-power supply and are costly. It includes a fuel cell voltage detection module, which uses a shunt resistor to detect the operating voltage provided by the fuel cell, and uses an operational amplifier to obtain the amplified value of the operating voltage as the voltage feedback value of the fuel cell; a power management module, which uses a maximum power tracking point algorithm based on the operating voltage to periodically disconnect the fuel cell from the load and measure the current open circuit voltage of the fuel cell, and by adjusting the ratio of the operating voltage to the current open circuit voltage, the fuel cell operates at maximum power; a display module, which is used to convert the voltage feedback value into a current signal, and then determine the current methanol concentration of the fuel cell based on the current signal and display it. The present invention is used for methanol concentration detection in fuel cells.

Description

Technical Field

[0001] The invention relates to a self-powered methanol concentration sensing system for a direct methanol fuel cell, belonging to the technical field of methanol concentration sensing of fuel cells. Background Art

[0002] Portable electronic products and wireless devices are becoming increasingly highly integrated and high-performance, placing higher demands on the integration and energy density of micro-energy devices. Micro direct methanol fuel cells (μDMFCs) are competitive in the field of micro-energy devices due to their ease of miniaturization, high theoretical energy density, fast charging speed, easy fuel storage, and pollution-free operation. They are considered one of the micro-energy sources with the greatest potential to replace lithium-ion batteries. Furthermore, μDMFCs offer advantages such as simple structure, small size, ease of operation, and convenient storage and portability. They are widely used in portable products such as mobile phones and have great prospects for development in military applications, small vehicles, and emergency auxiliary power sources.

[0003] Currently, the materials and cell assembly methods used in μDMFC research are borrowed from proton exchange membrane fuel cells (PEMFCs) and are therefore not fully applicable to μDMFCs. Although extensive research has been conducted domestically and internationally on the performance of μDMFCs in recent years, with some success, the road to commercialization is still long, with many challenges to overcome. μDMFC performance is affected by numerous parameters, including temperature, pressure, methanol concentration, and catalyst type. The methanol concentration of the fuel is a crucial factor affecting μDMFC performance. When the methanol concentration is below a predetermined value, power output is low and unstable. When the methanol concentration exceeds this value, methanol crossover becomes a serious problem, resulting in significant efficiency loss. Therefore, the fuel must be supplied to the fuel cell while maintaining a consistent methanol concentration within a predetermined range. In short, for long-term stable closed-loop control of methanol concentration, a concentration sensor is required to provide feedback for the injection of replenished methanol into the circulating stream. Therefore, a device capable of real-time monitoring of methanol concentration is crucial to ensuring efficient and stable system operation.

[0004] Among the currently used methods for measuring methanol concentration, spectrophotometry and gas chromatography are the most common and widely used. However, these instruments are bulky, complex to operate, difficult to integrate and miniaturize, and relatively expensive. In addition to physical-based measurement methods, there are also sensor-based methods for measuring methanol concentration, including electrochemical, capacitive, photochemical, and resistive methanol sensors. Electrochemical methanol sensors offer high sensitivity, a simple structure, and are easy to integrate and miniaturize, but they also present a number of challenges, such as catalyst cost and proton exchange membrane permeability. In specific applications, fuel cells also suffer from common drawbacks related to fuel injection and decomposition, which also apply to non-self-powered sensor applications based on batteries and electrochemical sensors. Furthermore, the need for timely battery replacement and the need for precise recalibration and regular replacement of electrochemical sensors are significant drawbacks of traditional methanol sensors. Currently, commercially available sensors also suffer from high power consumption and slow response speeds. Summary of the Invention

[0005] Aiming at the problem that the existing methanol concentration sensor cannot realize self-power supply and has high cost, the present invention provides a self-powered methanol concentration sensing system for a direct methanol fuel cell.

[0006] A self-powered methanol concentration sensing system for a direct methanol fuel cell of the present invention comprises:

[0007] The fuel cell voltage detection module uses a shunt resistor to detect the operating voltage provided by the fuel cell, and uses an operational amplifier to obtain an amplified value of the operating voltage, which is used as the voltage feedback value of the fuel cell;

[0008] The power management module uses the maximum power tracking point algorithm based on the operating voltage to periodically disconnect the fuel cell from the load and measure the current open circuit voltage of the fuel cell. By adjusting the ratio of the operating voltage to the current open circuit voltage, the fuel cell can operate at maximum power.

[0009] The display module is used to convert the voltage feedback value into a current signal, and then determine the current methanol concentration of the fuel cell based on the current signal and display it.

[0010] According to the self-powered methanol concentration sensing system of the direct methanol fuel cell of the present invention, the circuit structure of the fuel cell voltage detection module includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, an operational amplifier T1 and an operational amplifier T2;

[0011] The positive electrode of the fuel cell is connected to one end of the resistor R1, and the other end of the resistor R1 serves as the output end of the fuel cell working voltage; the negative electrode of the fuel cell is grounded;

[0012] One end of the resistor R1 is connected to the non-inverting input of the operational amplifier T2, and the other end of the resistor R1 is connected to the non-inverting input of the operational amplifier T1; the inverting input of the operational amplifier T1 is connected to one end of the resistor R3, and the other end of the resistor R3 is grounded; the resistor R2 is connected between the inverting input and output of the operational amplifier T1; the resistor R4 is connected between the output of the operational amplifier T1 and the inverting input of the operational amplifier T2; the resistor R5 is connected between the inverting input and output of the operational amplifier T2; and the output of the operational amplifier T2 outputs the voltage feedback value of the fuel cell.

[0013] According to the self-powered methanol concentration sensing system of the direct methanol fuel cell of the present invention, the circuit structure of the power management module includes capacitor C1, capacitor C2, capacitor C3, capacitor C4, inductor L1, resistor ROC1, resistor ROC2, capacitor CDD, photodiode LED3, resistor R6, resistor ROK1, resistor ROK2, resistor ROK3, resistor RUV1, resistor RUV2, resistor ROV1, resistor ROV2 and a boost converter chip.

[0014] The output end of the fuel cell operating voltage is connected to the VIN-DC pin of the boost converter chip. A capacitor C1 is connected between the VIN-DC pin and the OT-PROG pin of the boost converter chip. The OT-PROG pin is grounded. A resistor ROC2 is connected between the VIN-DC pin and the VOC-SAMP pin of the boost converter chip. A resistor ROC1 is connected between the VOC-SAMP pin and the OT-PROG pin. A capacitor C2 is connected between the VREF-SAMP pin and the OT-PROG pin of the boost converter chip.

[0015] Connect inductor L1 between the VIN-DC pin and LBST pin of the boost converter chip;

[0016] The VSTOR pin of the boost converter chip is connected to one end of capacitor C3, the other end of capacitor C3 is grounded, and capacitor C4 is connected in parallel with capacitor C3; the VSTOR pin of the boost converter chip serves as the output terminal VOUT of the output voltage of the power management module; the VBAT pin of the boost converter chip is connected to the positive electrode of capacitor CDD, the negative electrode of capacitor CDD is connected to the AVSS pin, the VBAT-OK pin is connected to the anode of photodiode LED3, the cathode of photodiode LED3 is connected to one end of resistor R6, and the other end of resistor R6 is grounded;

[0017] The OK-PROG pin is connected to one end of resistor ROK1, and the other end of resistor ROK1 is grounded. Resistor ROK2 is connected between the OK-PROG pin and the OK-HYST pin. Resistor ROK3 is connected between the OK-HYST pin and the VRDIV pin. The VRDIV pin is connected to one end of resistor RUV2, the other end of resistor RUV2 is connected to one end of resistor RUV1, and the other end of resistor RUV1 is grounded. The VBAT-UV pin is connected to the other end of resistor RUV2, the VRDIV pin is connected to one end of resistor ROV2, the other end of resistor ROV2 is connected to one end of resistor ROV1, and the other end of resistor ROV1 is grounded. The VBAT-OV pin is connected to the other end of resistor ROV2.

[0018] According to the self-powered methanol concentration sensing system of the direct methanol fuel cell of the present invention, the circuit structure of the display module includes an MSP430F149 single-chip microcomputer, a liquid crystal display, a resistor R7, a capacitor C5, a switch SW1, a capacitor C6, a capacitor C7, a capacitor C8, a crystal oscillator X2, a resistor R8, a photodiode LED2, a sliding rheostat RP1, a capacitor C9, a capacitor C10, a capacitor C11 and a crystal oscillator X1.

[0019] One end of the resistor R7 is connected to the output terminal VOUT of the power management module output voltage, the other end of the resistor R7 is connected to one end of the capacitor C5, and the other end of the capacitor C5 is grounded; the capacitor C5 is connected in parallel with the switch SW1;

[0020] One end of resistor R7 is connected to the DVCC pin of MSP430F149 microcontroller, the DVCC pin is connected to one end of capacitor C6, and the other end of capacitor C6 is grounded; one end of resistor R7 is connected to the AVSS pin of MSP430F149 microcontroller, the AVSS pin is connected to one end of capacitor C9, and the other end of capacitor C9 is grounded; the other end of capacitor C9 is connected to both the DVSS pin and the AVSS pin; the XIN pin is connected to one end of crystal oscillator X2, the other end of crystal oscillator X2 is connected to the XOUT pin, the XOUT pin is connected to one end of capacitor C7, the other end of capacitor C7 is grounded, and the other end of capacitor C7 is connected to one end of crystal oscillator X2 Connect capacitor C8 between them; P2.0 / ACLK pin is connected to the cathode of photodiode LED2, the anode of photodiode LED2 is connected to one end of resistor R8, and the other end of resistor R8 is connected to the output terminal VOUT of the power management module output voltage; XT2IN pin is connected to one end of crystal oscillator X1, the other end of crystal oscillator X1 is connected to XT2OUT pin, one end of crystal oscillator X1 is connected to one end of capacitor C10, and the other end of capacitor C10 is grounded; XT2OUT pin is connected to one end of capacitor C11, and the other end of capacitor C11 is grounded; P6.0 / A0 pin of MSP430F149 microcontroller is used to receive voltage feedback value;

[0021] The control display pins of the MSP430F149 microcontroller and the LCD are connected accordingly; the BLA pin of the LCD is connected to the output terminal VOUT of the output voltage of the power management module; the VCC pin of the LCD is connected to the output terminal VOUT of the output voltage of the power management module; the VCC pin of the LCD is connected to one end of the sliding resistor RP1, the other end of the sliding resistor RP1 is grounded, and the V0 pin of the LCD is connected to the sliding end of the sliding resistor RP1.

[0022] Beneficial effects of the present invention: The methanol concentration sensing system of the present invention can realize the detection of methanol concentration in the fuel cell through circuit structure and parameter design, and can directly use the fuel cell to supply energy to the system, with the advantages of low power consumption, low cost and fast response.

[0023] The system uses the methanol to be measured as fuel to power the system, eliminating the need for an additional power source, resulting in low power consumption and a fast response speed. The power management module utilizes a maximum power point tracking algorithm to extract energy from the methanol fuel cell with maximum efficiency, enabling the sensor device to self-power itself. The fuel cell voltage detection module collects output voltage indicators correlated with methanol concentration, converts them into current, and displays them via the display module. This allows for real-time display of the methanol concentration and the fuel cell output current on the screen, enabling rapid, real-time measurement of methanol concentration.

[0024] In the system of the present invention, energy extraction and concentration detection of the fuel cell can be carried out simultaneously, with high detection sensitivity and not easily interfered with. Experimental verification shows that the response time is 0.34 seconds.

[0025] The system of the present invention has a simple circuit implementation, is easy to integrate, and has low cost. The overall power consumption of the system is approximately 1.1 mW. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a principle block diagram of the self-powered methanol concentration sensing system of the direct methanol fuel cell of the present invention;

[0027] Figure 2 This is a schematic diagram of the circuit structure of the fuel cell voltage detection module;

[0028] Figure 3 This is a schematic diagram of the circuit structure of the power management module;

[0029] Figure 4 It is a schematic diagram of the circuit structure of the display module;

[0030] Figure 5 This is a front view of a printed circuit board for implementing the self-powered methanol concentration sensing system for a direct methanol fuel cell according to the present invention;

[0031] Figure 6yes Figure 5 Schematic diagram of the reverse side. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only 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 making any creative efforts shall fall within the scope of protection of the present invention.

[0033] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0034] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0035] Specific implementation method 1. Combination Figures 1 to 4 As shown, the present invention provides a self-powered methanol concentration sensing system for a direct methanol fuel cell, comprising:

[0036] The fuel cell voltage detection module uses a shunt resistor to detect the operating voltage provided by the fuel cell, and uses an operational amplifier to obtain an amplified value of the operating voltage, which is used as the voltage feedback value of the fuel cell;

[0037] The power management module uses the maximum power tracking point algorithm based on the operating voltage to periodically disconnect the fuel cell from the load and measure the current open circuit voltage of the fuel cell. By adjusting the ratio of the operating voltage to the current open circuit voltage, the fuel cell can operate at maximum power.

[0038] The display module is used to convert the voltage feedback value into a current signal, and then determine the current methanol concentration of the fuel cell based on the current signal and display it.

[0039] In this embodiment, the fuel cell voltage detection module has low power loss on the resistor at low current levels, does not require additional power supply to operate, does not need to deal with thermal drift, hysteresis or electromagnetic interference, etc., and has low cost; the fuel cell voltage detection module is connected in series between the fuel cell and the power management module.

[0040] The power management module can use a DC-DC converter to increase the low-level voltage provided by the fuel cell, with high integration. It uses a maximum power tracking point algorithm for power management to extract energy from the methanol fuel cell with maximum efficiency. It can be implemented using mature silicon-based manufacturing technology and is low-cost.

[0041] The display module may include a microcontroller module and a user interface. The microcontroller module converts the voltage feedback value into a current signal through a corresponding relationship, and then determines the current methanol concentration of the fuel cell based on the current signal; and then displays the current signal and the current methanol concentration on the user interface.

[0042] The methanol concentration sensing system described in this embodiment uses the methanol solution to be measured as fuel to power the system, and no other additional power source is required.

[0043] Compared with existing methanol sensors, the power management module in this embodiment can efficiently extract the higher chemical energy in methanol, effectively convert it into electrical energy, and output a stable voltage to power the front-end fuel cell voltage detection module and display module, with high energy conversion efficiency; the methanol solution to be tested is used as fuel to power the sensing system, realizing self-power supply of the sensor, and there is no need to regularly replace the power supply battery.

[0044] Further, combined Figure 2 As shown, the circuit structure of the fuel cell voltage detection module includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, an operational amplifier T1 and an operational amplifier T2;

[0045] The positive electrode of the fuel cell is connected to one end of the resistor R1, and the other end of the resistor R1 serves as the output end of the fuel cell working voltage; the negative electrode of the fuel cell is grounded;

[0046] One end of the resistor R1 is connected to the non-inverting input of the operational amplifier T2, and the other end of the resistor R1 is connected to the non-inverting input of the operational amplifier T1; the inverting input of the operational amplifier T1 is connected to one end of the resistor R3, and the other end of the resistor R3 is grounded; the resistor R2 is connected between the inverting input and output of the operational amplifier T1; the resistor R4 is connected between the output of the operational amplifier T1 and the inverting input of the operational amplifier T2; the resistor R5 is connected between the inverting input and output of the operational amplifier T2; and the output of the operational amplifier T2 outputs the voltage feedback value of the fuel cell.

[0047] Combine Figure 3 As shown, the circuit structure of the power management module includes capacitor C1, capacitor C2, capacitor C3, capacitor C4, inductor L1, resistor ROC1, resistor ROC2, capacitor CDD, photodiode LED3, resistor R6, resistor ROK1, resistor ROK2, resistor ROK3, resistor RUV1, resistor RUV2, resistor ROV1, resistor ROV2 and a boost converter chip.

[0048] The output end of the fuel cell operating voltage is connected to the VIN-DC pin of the boost converter chip. A capacitor C1 is connected between the VIN-DC pin and the OT-PROG pin of the boost converter chip. The OT-PROG pin is grounded. A resistor ROC2 is connected between the VIN-DC pin and the VOC-SAMP pin of the boost converter chip. A resistor ROC1 is connected between the VOC-SAMP pin and the OT-PROG pin. A capacitor C2 is connected between the VREF-SAMP pin and the OT-PROG pin of the boost converter chip.

[0049] Connect inductor L1 between the VIN-DC pin and LBST pin of the boost converter chip;

[0050] The VSTOR pin of the boost converter chip is connected to one end of capacitor C3, the other end of capacitor C3 is grounded, and capacitor C4 is connected in parallel with capacitor C3; the VSTOR pin of the boost converter chip serves as the output terminal VOUT of the output voltage of the power management module; the VBAT pin of the boost converter chip is connected to the positive electrode of capacitor CDD, the negative electrode of capacitor CDD is connected to the AVSS pin, the VBAT-OK pin is connected to the anode of photodiode LED3, the cathode of photodiode LED3 is connected to one end of resistor R6, and the other end of resistor R6 is grounded;

[0051] The OK-PROG pin is connected to one end of resistor ROK1, and the other end of resistor ROK1 is grounded. Resistor ROK2 is connected between the OK-PROG pin and the OK-HYST pin. Resistor ROK3 is connected between the OK-HYST pin and the VRDIV pin. The VRDIV pin is connected to one end of resistor RUV2, the other end of resistor RUV2 is connected to one end of resistor RUV1, and the other end of resistor RUV1 is grounded. The VBAT-UV pin is connected to the other end of resistor RUV2, the VRDIV pin is connected to one end of resistor ROV2, the other end of resistor ROV2 is connected to one end of resistor ROV1, and the other end of resistor ROV1 is grounded. The VBAT-OV pin is connected to the other end of resistor ROV2.

[0052] Combine Figure 4 As shown, the circuit structure of the display module includes MSP430F149 single chip microcomputer, liquid crystal display, resistor R7, capacitor C5, switch SW1, capacitor C6, capacitor C7, capacitor C8, crystal oscillator X2, resistor R8, photodiode LED2, sliding rheostat RP1, capacitor C9, capacitor C10, capacitor C11 and crystal oscillator X1.

[0053] One end of the resistor R7 is connected to the output terminal VOUT of the power management module output voltage, the other end of the resistor R7 is connected to one end of the capacitor C5, and the other end of the capacitor C5 is grounded; the capacitor C5 is connected in parallel with the switch SW1;

[0054] One end of resistor R7 is connected to the DVCC pin of MSP430F149 microcontroller, the DVCC pin is connected to one end of capacitor C6, and the other end of capacitor C6 is grounded; one end of resistor R7 is connected to the AVSS pin of MSP430F149 microcontroller, the AVSS pin is connected to one end of capacitor C9, and the other end of capacitor C9 is grounded; the other end of capacitor C9 is connected to both the DVSS pin and the AVSS pin; the XIN pin is connected to one end of crystal oscillator X2, the other end of crystal oscillator X2 is connected to the XOUT pin, the XOUT pin is connected to one end of capacitor C7, the other end of capacitor C7 is grounded, and the other end of capacitor C7 is connected to one end of crystal oscillator X2 Connect capacitor C8 between them; P2.0 / ACLK pin is connected to the cathode of photodiode LED2, the anode of photodiode LED2 is connected to one end of resistor R8, and the other end of resistor R8 is connected to the output terminal VOUT of the power management module output voltage; XT2IN pin is connected to one end of crystal oscillator X1, the other end of crystal oscillator X1 is connected to XT2OUT pin, one end of crystal oscillator X1 is connected to one end of capacitor C10, and the other end of capacitor C10 is grounded; XT2OUT pin is connected to one end of capacitor C11, and the other end of capacitor C11 is grounded; P6.0 / A0 pin of MSP430F149 microcontroller is used to receive voltage feedback value;

[0055] The control display pins of the MSP430F149 microcontroller and the LCD are connected accordingly; the BLA pin of the LCD is connected to the output terminal VOUT of the output voltage of the power management module; the VCC pin of the LCD is connected to the output terminal VOUT of the output voltage of the power management module; the VCC pin of the LCD is connected to one end of the sliding resistor RP1, the other end of the sliding resistor RP1 is grounded, and the V0 pin of the LCD is connected to the sliding end of the sliding resistor RP1.

[0056] In this embodiment, the back-end display module is connected to the fuel cell voltage feedback value output by the amplifier T2 of the front-end fuel cell voltage detection module through the P6.0 / A0 pin of the MSP430F149 microcontroller, and is used to convert the voltage feedback signal into a current signal and methanol concentration, which are displayed on the user interface.

[0057] Combine Figure 2As shown, the fuel cell voltage detection module measures the current provided by the fuel cell through a shunt resistor and an instrumentation amplifier. The instrumentation amplifier provides a voltage signal that is proportional to the measured current. The instrumentation amplifier includes a dual operational amplifier, which can be implemented by two LPV521 operational amplifiers. The LPV521 has the characteristics of ultra-low power consumption and can provide a minimum power consumption of 552nW. It supports a power supply voltage as low as 1.6V, which is suitable for powering the power management module. In addition, the input voltage drift of the LPV521 is smaller and more stable, which can ensure that the current detection process is stable and reliable, and the measurement is more accurate. The output voltage (VSEN) of the operational amplifier is proportional to the measured current of the fuel cell. By changing the resistance value, different multiples of amplification can be achieved. Figure 1 The magnification of the medium measurement module is 143 times.

[0058] Furthermore, the parameter setting of the fuel cell voltage detection module meets the following conditions:

[0059]

[0060] Where V1 is the output voltage of operational amplifier T1, VOP is the operating voltage of the fuel cell, VFC is the inverting input voltage of operational amplifier T2, VSEN is the voltage feedback value output by operational amplifier T2; IFC is the current flowing through resistor R1.

[0061] Combine Figure 3 As shown, the power management module can use the BQ25504 boost converter chip. This chip collects and manages the energy of the direct methanol fuel cell, providing an adjustable voltage for the load circuit. It also uses a maximum power point tracking algorithm to extract energy from the direct methanol fuel cell with maximum efficiency. The MPPT algorithm periodically disconnects the fuel cell from the system and measures the fuel cell's open circuit voltage (OCV). By adjusting the ratio of the operating voltage to the OCV, the fuel cell can operate at maximum power. The sum of the resistors used for voltage division is typically 20MΩ. By designing different resistance values ​​for ROC1 and ROC2, the system does not need to disconnect the fuel cell. By setting the input voltage to the maximum power point voltage, more energy can be extracted from the fuel cell.

[0062] In this embodiment, in order to implement the maximum power point tracking algorithm of the power management module, the parameters of the boost converter chip are set to meet the following formula:

[0063]

[0064] Where V REF_SAMP is the voltage value of VREF-SAMP pin of the boost converter chip, V IN_DC It is the voltage value of the VIN-DC pin of the boost converter chip.

[0065] Recombination Figure 3 As shown in the figure, to prevent the power management module from deep discharge and the complete consumption of the capacitor storage element, the chip requires undervoltage protection. The undervoltage threshold (VBAT_UV) is set by the RUV2 and RUV1 resistors in the peripheral circuit. Similarly, to prevent the PMU from being damaged by excessively high charging voltages, the chip uses external resistors ROV1 and ROV2 to set the overvoltage (VBAT_OV) threshold level. The typical sum of RUV1 and RUV2 is 10MΩ.

[0066] In order to achieve undervoltage protection of the power management module, the parameters of the boost converter chip are set to meet the following formula:

[0067]

[0068] Where V BAT_UV is the voltage value of the VBAT-UV pin, V BIAS is the reference voltage of the boost converter chip, V BAT_OV is the voltage value of the VBAT-OV pin.

[0069] For the VBAT_UV pin in the power management module to function properly, the load must be connected to VSTOR, which is the VOUT pin powering the load in this system. The memory cell CDD should be connected to the VBAT pin. Once the VSTOR voltage exceeds the sum of the VBAT_UV and VBAT_UV_HYST thresholds, the VSTOR and VBAT pins are effectively shorted via an internal transistor, and the switch remains off until the VSTOR voltage falls below the VBAT_UV threshold. In addition to setting the UV and OV thresholds, the chip also sets the normal operating voltage range. The VBAT_OK pin outputs a normal operating voltage signal, which can be connected to other chips. This range is also typically connected to the VBAT_PROG and VBAT_OK_HYST pins via an external voltage divider circuit. The typical sum of the ROK1, ROK2, and ROK3 resistors is 10MΩ.

[0070] In order to make the boost converter chip work within the normal operating voltage range, the parameter settings must meet the following conditions:

[0071]

[0072] Where V BAT_OK_PROG When the VBAT pin voltage drops, the VBAT-OK pin voltage threshold value is V BAT_OK_HYST This is the VBAT-OK pin voltage threshold when the VBAT pin voltage rises.

[0073] Combine Figure 4 As shown, the back-end display module can be implemented using an MSP430F149 microcontroller to drive an LCD1602 liquid crystal display. The MSP430F149's ADC12 module is used to collect the VSEN voltage output by the front-end measurement module. Connecting VSEN to the MSP430F149's P6.0 port converts the analog value into a digital value. Program code is then written to display the corresponding current and methanol fuel cell concentration on the LCD1602. The clock modules of the MSP430 series microcontroller are: the auxiliary clock signal (ACLK), which is connected to an external 32.768kHz crystal oscillator X2; the main clock signal (MCLK), the main clock for normal CPU operation, is connected to an external 8kHz crystal oscillator X1, the two ends of which are connected to the MSP430F149's XT2IN and XT2OUT pins respectively; and the subsystem clock (SMCLK) is used for high-speed peripheral modules. The MSP430F149 chip's JTAG interface is exposed to facilitate chip programming, allowing users to implement different MCU functions through coding. The JTAG interface's TDO, TDI, TMS, and TCK pins are connected to the MCU's 54-pin TDO / TDI, 55-pin TDI / TCLK, 56-pin TMS, and 57-pin TCK, respectively.

[0074] Combine Figure 5 and Figure 6 As shown, the system of the present invention can be implemented on a printed circuit board.

[0075] Although the present invention is described herein with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the invention. It should be understood that many modifications may be made to the illustrative embodiments, and that other arrangements may be devised, without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in ways other than those described in the original claims. It should also be understood that features described in conjunction with individual embodiments may be used in conjunction with other described embodiments.

Claims

1. A self-powered methanol concentration sensing system for a direct methanol fuel cell, characterized in that: include: The fuel cell voltage detection module uses a shunt resistor to detect the operating voltage provided by the fuel cell, and uses an operational amplifier to obtain an amplified value of the operating voltage, which is used as the voltage feedback value of the fuel cell; The power management module uses the maximum power tracking point algorithm based on the operating voltage to periodically disconnect the fuel cell from the load and measure the current open circuit voltage of the fuel cell. By adjusting the ratio of the operating voltage to the current open circuit voltage, the fuel cell can operate at maximum power. The display module is used to convert the voltage feedback value into a current signal, and then determine the current methanol concentration of the fuel cell based on the current signal and display it.

2. The self-powered methanol concentration sensing system for a direct methanol fuel cell according to claim 1, characterized in that: The circuit structure of the fuel cell voltage detection module includes a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, an operational amplifier T1 and an operational amplifier T2; The positive electrode of the fuel cell is connected to one end of the resistor R1, and the other end of the resistor R1 serves as the output end of the fuel cell working voltage; the negative electrode of the fuel cell is grounded; One end of the resistor R1 is connected to the non-inverting input of the operational amplifier T2, and the other end of the resistor R1 is connected to the non-inverting input of the operational amplifier T1; the inverting input of the operational amplifier T1 is connected to one end of the resistor R3, and the other end of the resistor R3 is grounded; the resistor R2 is connected between the inverting input and output of the operational amplifier T1; the resistor R4 is connected between the output of the operational amplifier T1 and the inverting input of the operational amplifier T2; the resistor R5 is connected between the inverting input and output of the operational amplifier T2; and the output of the operational amplifier T2 outputs the voltage feedback value of the fuel cell.

3. The self-powered methanol concentration sensing system for a direct methanol fuel cell according to claim 2, characterized in that: The circuit structure of the power management module includes capacitor C1, capacitor C2, capacitor C3, capacitor C4, inductor L1, resistor ROC1, resistor ROC2, capacitor CDD, photodiode LED3, resistor R6, resistor ROK1, resistor ROK2, resistor ROK3, resistor RUV1, resistor RUV2, resistor ROV1, resistor ROV2 and a boost converter chip. The output end of the fuel cell operating voltage is connected to the VIN-DC pin of the boost converter chip. A capacitor C1 is connected between the VIN-DC pin and the OT-PROG pin of the boost converter chip. The OT-PROG pin is grounded. A resistor ROC2 is connected between the VIN-DC pin and the VOC-SAMP pin of the boost converter chip. A resistor ROC1 is connected between the VOC-SAMP pin and the OT-PROG pin. A capacitor C2 is connected between the VREF-SAMP pin and the OT-PROG pin of the boost converter chip. Connect inductor L1 between the VIN-DC pin and LBST pin of the boost converter chip; The VSTOR pin of the boost converter chip is connected to one end of capacitor C3, the other end of capacitor C3 is grounded, and capacitor C4 is connected in parallel with capacitor C3; the VSTOR pin of the boost converter chip serves as the output terminal VOUT of the output voltage of the power management module; the VBAT pin of the boost converter chip is connected to the positive electrode of capacitor CDD, the negative electrode of capacitor CDD is connected to the AVSS pin, the VBAT-OK pin is connected to the anode of photodiode LED3, the cathode of photodiode LED3 is connected to one end of resistor R6, and the other end of resistor R6 is grounded; The OK-PROG pin is connected to one end of resistor ROK1, and the other end of resistor ROK1 is grounded. Resistor ROK2 is connected between the OK-PROG pin and the OK-HYST pin. Resistor ROK3 is connected between the OK-HYST pin and the VRDIV pin. The VRDIV pin is connected to one end of resistor RUV2, the other end of resistor RUV2 is connected to one end of resistor RUV1, and the other end of resistor RUV1 is grounded. The VBAT-UV pin is connected to the other end of resistor RUV2, the VRDIV pin is connected to one end of resistor ROV2, the other end of resistor ROV2 is connected to one end of resistor ROV1, and the other end of resistor ROV1 is grounded. The VBAT-OV pin is connected to the other end of resistor ROV2.

4. The self-powered methanol concentration sensing system for a direct methanol fuel cell according to claim 3, characterized in that: The circuit structure of the display module includes MSP430F149 single chip microcomputer, liquid crystal display, resistor R7, capacitor C5, switch SW1, capacitor C6, capacitor C7, capacitor C8, crystal oscillator X2, resistor R8, photodiode LED2, sliding rheostat RP1, capacitor C9, capacitor C10, capacitor C11 and crystal oscillator X1. One end of the resistor R7 is connected to the output terminal VOUT of the power management module output voltage, the other end of the resistor R7 is connected to one end of the capacitor C5, and the other end of the capacitor C5 is grounded; the capacitor C5 is connected in parallel with the switch SW1; One end of resistor R7 is connected to the DVCC pin of MSP430F149 microcontroller, the DVCC pin is connected to one end of capacitor C6, and the other end of capacitor C6 is grounded; one end of resistor R7 is connected to the AVSS pin of MSP430F149 microcontroller, the AVSS pin is connected to one end of capacitor C9, and the other end of capacitor C9 is grounded; the other end of capacitor C9 is connected to both the DVSS pin and the AVSS pin; the XIN pin is connected to one end of crystal oscillator X2, the other end of crystal oscillator X2 is connected to the XOUT pin, the XOUT pin is connected to one end of capacitor C7, the other end of capacitor C7 is grounded, and the other end of capacitor C7 is connected to one end of crystal oscillator X2 Connect capacitor C8 between them; P2.0 / ACLK pin is connected to the cathode of photodiode LED2, the anode of photodiode LED2 is connected to one end of resistor R8, and the other end of resistor R8 is connected to the output terminal VOUT of the power management module output voltage; XT2IN pin is connected to one end of crystal oscillator X1, the other end of crystal oscillator X1 is connected to XT2OUT pin, one end of crystal oscillator X1 is connected to one end of capacitor C10, and the other end of capacitor C10 is grounded; XT2OUT pin is connected to one end of capacitor C11, and the other end of capacitor C11 is grounded; P6.0 / A0 pin of MSP430F149 microcontroller is used to receive voltage feedback value; The control display pins of the MSP430F149 microcontroller and the LCD are connected accordingly; the BLA pin of the LCD is connected to the output terminal VOUT of the output voltage of the power management module; the VCC pin of the LCD is connected to the output terminal VOUT of the output voltage of the power management module; the VCC pin of the LCD is connected to one end of the sliding resistor RP1, the other end of the sliding resistor RP1 is grounded, and the V0 pin of the LCD is connected to the sliding end of the sliding resistor RP1.

5. The self-powered methanol concentration sensing system for a direct methanol fuel cell according to claim 4, characterized in that: The parameter settings of the fuel cell voltage detection module meet the following conditions: Where V1 is the output voltage of operational amplifier T1, VOP is the operating voltage of the fuel cell, VFC is the inverting input voltage of operational amplifier T2, VSEN is the voltage feedback value output by operational amplifier T2; IFC is the current flowing through resistor R1.

6. The self-powered methanol concentration sensing system for a direct methanol fuel cell according to claim 5, characterized in that: In order to implement the maximum power tracking point algorithm of the power management module, the parameters of the boost converter chip are set to meet the following formula: Where V REF_SAMP is the voltage value of VREF-SAMP pin of the boost converter chip, V IN_DC It is the voltage value of the VIN-DC pin of the boost converter chip.

7. The self-powered methanol concentration sensing system for a direct methanol fuel cell according to claim 6, characterized in that: In order to achieve undervoltage protection of the power management module, the parameters of the boost converter chip are set to meet the following formula: Where V BAT_UV is the voltage value of the VBAT-UV pin, V BIAS is the reference voltage of the boost converter chip, V BAT_OV is the voltage value of the VBAT-OV pin.

8. The self-powered methanol concentration sensing system for a direct methanol fuel cell according to claim 7, characterized in that: In order to make the boost converter chip work within the normal operating voltage range, the parameter settings must meet the following conditions: Where V BAT_OK_PROG When the VBAT pin voltage drops, the VBAT-OK pin voltage threshold value is V BAT_OK_HYST This is the VBAT-OK pin voltage threshold when the VBAT pin voltage rises.

9. The self-powered methanol concentration sensing system for a direct methanol fuel cell according to claim 1, characterized in that: The operational amplifier T1 and the operational amplifier T2 are both LPV521.

10. The self-powered methanol concentration sensing system for a direct methanol fuel cell according to claim 4, characterized in that: The model of the boost converter chip is BQ25504; The model of the LCD is LCD1602.

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