Self-powered methanol concentration sensing system of direct methanol fuel cell

Abstract

The invention discloses a self-powered methanol concentration sensing system of a direct methanol fuel cell, and belongs to the technical field of methanol concentration sensing of fuel cells. The invention aims to solve the problems that the existing methanol concentration sensor cannot realize self-power supply and is high in cost. Comprising a fuel cell voltage detection module, which adopts a shunt resistor to detect a working voltage provided by a fuel cell, and adopts an operational amplifier to obtain an amplified value of the working voltage as a voltage feedback value of the fuel cell; the power supply management module is used for periodically disconnecting the fuel cell from the load based on the working voltage by adopting a maximum power tracking point algorithm, measuring the current open-circuit voltage of the fuel cell, and enabling the fuel cell to work in a maximum power state by adjusting the ratio of the working voltage to the current open-circuit voltage; and the display module is used for converting the voltage feedback value into a current signal, determining the current methanol concentration of the fuel cell based on the current signal, and displaying the current methanol concentration. The method is used for detecting the methanol concentration of the fuel cell.

Description

Technical Field

[0001] The invention relates to a self-powered methanol concentration sensing system of 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 more and more highly integrated and high-performance, which puts forward higher requirements on the integration and energy density of micro energy supply devices. Micro direct methanol fuel cells (μDMFC) are competitive in the field of micro energy supply devices due to their advantages such as easy miniaturization, high theoretical energy density, fast charging speed, easy fuel storage, and no pollution. They are considered to be one of the most promising micro energy sources to replace lithium-ion batteries. In addition, μDMFC has the advantages of simple structure, small size, easy operation, convenient storage and carrying, etc. It is widely used in portable products such as mobile phones, and has good development prospects in military applications, small vehicles, emergency auxiliary power supplies, etc.

[0003] At present, the materials and battery assembly methods used in μDMFC research are borrowed from proton exchange membrane fuel cell (PEMFC), so they are not completely applicable to μDMFC. Although a lot of research has been done on the performance of μDMFC at home and abroad in recent years, and certain results have been achieved, the road to commercial use of μDMFC is still very long, and there are many problems to be overcome. The performance of μDMFC is affected by many parameters, such as temperature, pressure, methanol concentration, catalyst type, etc. Among them, the concentration of methanol used as fuel is a crucial factor affecting the performance of μDMFC. When the methanol concentration is lower than the predetermined value, the power output is low and unstable. When the methanol concentration is higher than the predetermined value, methanol permeation is a serious problem, resulting in a significant loss of efficiency. Therefore, the fuel needs to be supplied to the fuel cell when its methanol concentration remains consistent within the predetermined concentration range. In short, if the closed-loop control of methanol concentration is to operate stably for a long time, a concentration sensor is required to provide feedback for injecting supplementary methanol into the circulating flow. Therefore, a device that can detect methanol concentration in real time is of great significance to ensure efficient and stable operation of the system.

[0004] Among the methods currently used to measure methanol concentration, the most common and commonly used are spectrophotometry and gas chromatography. The measuring instruments are large in size, complex in operation, not easy to integrate and miniaturize, and have high costs. In addition to the measurement methods based on physical principles, there are also methods for measuring methanol concentration using sensors, including electrochemical methanol sensors, capacitive methanol sensors, photochemical methanol sensors, and resistive methanol sensors. Among them, electrochemical methanol sensors have high sensitivity, simple structure, and are easy to integrate and miniaturize, but there are also a series of problems, such as the cost of catalysts and the permeation of proton exchange membranes. In the specific application process, fuel cells also have common disadvantages related to fuel injection and decomposition, which also exist in non-self-powered sensor applications based on batteries and electrochemical sensors. In addition, batteries need to be replaced in a timely manner, and electrochemical sensors also need to be re-calibrated accurately and replaced regularly, which is also an obvious disadvantage of traditional methanol sensors. At present, sensors on the market also have problems such as high power consumption and slow response speed. Summary of the invention

[0005] In view of 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 working voltage provided by the fuel cell, and uses an operational amplifier to obtain an amplified value of the working voltage, and uses the amplified value as a voltage feedback value of the fuel cell;

[0008] The power management module uses the maximum power tracking point algorithm based on the working 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 working voltage to the current open circuit voltage, the fuel cell can be operated at the maximum power state.

[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 is used as the output end of the working voltage of the fuel cell; the negative electrode of the fuel cell is grounded;

[0012] One end of the resistor R1 is connected to the non-inverting input end of the operational amplifier T2, and the other end of the resistor R1 is connected to the non-inverting input end of the operational amplifier T1; the inverting input end 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 end and the output end of the operational amplifier T1; the resistor R4 is connected between the output end of the operational amplifier T1 and the inverting input end of the operational amplifier T2; the resistor R5 is connected between the inverting input end and the output end of the operational amplifier T2; the output end 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 conversion chip,

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

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

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

[0017] The OK-PROG pin is connected to one end of the resistor ROK1, and the other end of the resistor ROK1 is grounded. The resistor ROK2 is connected between the OK-PROG pin and the OK-HYST pin. The resistor ROK3 is connected between the OK-HYST pin and the VRDIV pin. The VRDIV pin is connected to one end of the resistor RUV2, and the other end of the resistor RUV2 is connected to one end of the resistor RUV1, and the other end of the resistor RUV1 is grounded. The VBAT-UV pin is connected to the other end of the resistor RUV2, the VRDIV pin is connected to one end of the resistor ROV2, and the other end of the resistor ROV2 is connected to one end of the resistor ROV1, and the other end of the resistor ROV1 is grounded. The VBAT-OV pin is connected to the other end of the 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 DVSS pin and AVSS pin; XIN pin is connected to one end of crystal oscillator X2, the other end of crystal oscillator X2 is connected to XOUT pin, XOUT pin is connected to one end of capacitor C7, the other end of capacitor C7 is grounded, the other end of capacitor C7 is connected to one end of crystal oscillator X2 Capacitor C8 is connected 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 end VOUT of the output voltage of the power management module; 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 correspondingly; 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 directly utilize the fuel cell to supply energy to the system while realizing the detection of the methanol concentration of the fuel cell through circuit structure and parameter design, and has the advantages of low power consumption, low cost and fast response.

[0023] The system of the present invention uses the methanol to be tested as fuel to power the system, does not require other additional power supplies, has low power consumption and fast response speed. The power management module adopts the maximum power point tracking algorithm to extract energy from the methanol fuel cell with maximum efficiency, thereby realizing self-power supply of the sensor device. The fuel cell voltage detection module collects the output voltage index that is correlated with the methanol concentration, converts it into current and displays it through the display module, thereby displaying the methanol concentration and the fuel cell output current in real time on the display screen, thereby realizing real-time and rapid measurement of the methanol concentration.

[0024] In the system of the present invention, energy extraction and concentration detection of the fuel cell can be performed simultaneously, the detection sensitivity is high, and it is not easily interfered with. It has been verified by experiments that the response time is 0.34 seconds.

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

[0026] Figure 1 It 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 It is a schematic diagram of the circuit structure of the fuel cell voltage detection module;

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

[0029] Figure 4 1 is a schematic diagram of the circuit structure of the display module;

[0030] Figure 5 It is a front schematic diagram of a printed circuit board for realizing the self-powered methanol concentration sensing system of the direct methanol fuel cell of the present invention;

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

[0032] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are 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 in conjunction with 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 working voltage provided by the fuel cell, and uses an operational amplifier to obtain an amplified value of the working voltage, and uses the amplified value as a voltage feedback value of the fuel cell;

[0037] The power management module uses the maximum power tracking point algorithm based on the working 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 working voltage to the current open circuit voltage, the fuel cell can be operated at the maximum power state.

[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 small power loss on the resistor at low current level, 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, and has a high degree of integration; it uses a maximum power tracking point algorithm for power management, which can extract energy from the methanol fuel cell with maximum efficiency; it can be implemented using mature silicon-based manufacturing technology, and has 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 tested as fuel to power the system, and no other additional power source is required.

[0043] Compared with the existing methanol sensor, 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 the display module, with high energy conversion efficiency; the methanol solution to be tested is used as fuel to power the sensor system, thereby realizing self-power supply of the sensor, and there is no need to regularly replace the power battery.

[0044] Further, combined with 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 is used as the output end of the working voltage of the fuel cell; the negative electrode of the fuel cell is grounded;

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

[0047] Combination 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 working voltage is connected to the VIN-DC pin of the boost converter chip, the capacitor C1 is connected between the VIN-DC pin and the OT-PROG pin of the boost converter chip, and the OT-PROG pin is grounded; the resistor ROC2 is connected between the VIN-DC pin and the VOC-SAMP pin of the boost converter chip, and the resistor ROC1 is connected between the VOC-SAMP pin and the OT-PROG pin; the capacitor C2 is connected between the VREF-SAMP pin and the OT-PROG pin of the boost converter chip;

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

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

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

[0052] Combination Figure 4 As shown, 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.

[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 DVSS pin and AVSS pin; XIN pin is connected to one end of crystal oscillator X2, the other end of crystal oscillator X2 is connected to XOUT pin, XOUT pin is connected to one end of capacitor C7, the other end of capacitor C7 is grounded, the other end of capacitor C7 is connected to one end of crystal oscillator X2 Capacitor C8 is connected 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 end VOUT of the output voltage of the power management module; 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 correspondingly; 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 rear-end display module is connected to the voltage feedback value of the fuel cell 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 is displayed on the user interface.

[0057] Combination 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. The supported power supply voltage can be 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 satisfies the following conditions:

[0059]

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

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

[0062] In this implementation, in order to implement the maximum power tracking point algorithm of the power management module, the parameter setting of the boost converter chip satisfies the following formula:

[0063]

[0064] Where V REF_SAMP is the voltage value of the 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 order to prevent the power management module from deep discharge and prevent the capacitor storage element from being completely consumed, the chip needs to set undervoltage protection. The undervoltage threshold (VBAT_UV) is set by the RUV2 and RUV1 resistors in the peripheral circuit. Similarly, in order 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 value of RUV1 and RUV2 is 10MΩ. The typical value of the sum of ROV1 and ROV2 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] In order for VBAT_UV in the power management module to work properly, the load must be connected to VSTOR, which is the VOUT that powers the load in this system. The storage unit 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 pin and the VBAT pin will be effectively shorted through an internal transistor, and the switch will remain in the off state until the VSTOR voltage is lower than 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 port will output a normal operating voltage signal, and the pin can be connected to other chips. This range is also mainly connected to the VBAT_PROG and VBAT_OK_HYST interfaces through an external voltage divider circuit. The sum of the typical values ​​of ROK1, ROK2, and ROK3 is 10MΩ.

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

[0071]

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

[0073] Combination Figure 4 As shown, the back-end display module can be realized by using a single-chip microcomputer of model MSP430F149 to drive the LCD1602 liquid crystal display screen. The ADC12 module of MSP430F149 is used to collect the VSEN voltage output by the front-end measurement module. Connecting VSEN to the P6.0 port of MSP430F149 can convert the analog quantity into a digital quantity, and then display the corresponding current and the concentration of the methanol fuel cell through LCD1602 by writing program code. The clock modules of the MSP430 series single-chip microcomputer are: auxiliary clock signal (ACLK), which is connected to the 32.768kHz crystal oscillator X2; main clock signal (MCLK), the main clock when the CPU is running normally, is connected to an 8kHz crystal oscillator X1, and the two ends of the crystal oscillator are respectively connected to the XT2IN and XT2OUT pins of MSP430F149; subsystem clock (SMCLK) is used for high-speed peripheral modules. The JTAG interface of the MSP430F149 chip is brought out to facilitate the user to burn the chip, and the different functions of the microcontroller can be realized through coding on the user side. The TDO\TDI, TMS, and TCK of the JTAG interface are connected to the 54-pin TDO / TDI, 55-pin TDI / TCLK, 56-pin TMS, and 57-pin TCK of the microcontroller respectively.

[0074] Combination 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 examples of the principles and applications of the present invention. It should therefore be understood that many modifications may be made to the exemplary embodiments and that other arrangements may be devised without departing from the spirit and scope of the present invention as defined by the appended claims. It should be understood that the various dependent claims and features described herein may be combined in a manner different from that described in the original claims. It should also be understood that the features described in conjunction with a single embodiment may be used in other described embodiments.

Claims

1. A self-powered methanol concentration sensing system for direct methanol fuel cells, It is characterized in that include: The fuel cell voltage detection module uses a shunt resistor to detect the working voltage provided by the fuel cell, and uses an operational amplifier to obtain an amplified value of the working voltage, and uses the amplified value as a voltage feedback value of the fuel cell; The power management module uses the maximum power tracking point algorithm based on the working 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 working voltage to the current open circuit voltage, the fuel cell can be operated at the maximum power state. 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, It is 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 is used as the output end of the working voltage of the fuel cell; the negative electrode of the fuel cell is grounded; One end of the resistor R1 is connected to the non-inverting input end of the operational amplifier T2, and the other end of the resistor R1 is connected to the non-inverting input end of the operational amplifier T1; the inverting input end 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 end and the output end of the operational amplifier T1; the resistor R4 is connected between the output end of the operational amplifier T1 and the inverting input end of the operational amplifier T2; the resistor R5 is connected between the inverting input end and the output end of the operational amplifier T2; the output end 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, It is 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 working voltage is connected to the VIN-DC pin of the boost converter chip, the capacitor C1 is connected between the VIN-DC pin and the OT-PROG pin of the boost converter chip, and the OT-PROG pin is grounded; the resistor ROC2 is connected between the VIN-DC pin and the VOC-SAMP pin of the boost converter chip, and the resistor ROC1 is connected between the VOC-SAMP pin and the OT-PROG pin; the capacitor C2 is connected between the VREF-SAMP pin and the OT-PROG pin of the boost converter chip; An inductor L1 is connected between the VIN-DC pin and the LBST pin of the boost converter chip; The VSTOR pin of the boost converter chip is connected to one end of the capacitor C3, the other end of the capacitor C3 is grounded, and the capacitor C4 is connected in parallel with the capacitor C3; the VSTOR pin of the boost converter chip serves as the output end 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 the capacitor CDD, the negative electrode of the capacitor CDD is connected to the AVSS pin, the VBAT-OK pin is connected to the anode of the photodiode LED3, the cathode of the photodiode LED3 is connected to one end of the resistor R6, and the other end of the resistor R6 is grounded; The OK-PROG pin is connected to one end of the resistor ROK1, and the other end of the resistor ROK1 is grounded. The resistor ROK2 is connected between the OK-PROG pin and the OK-HYST pin. The resistor ROK3 is connected between the OK-HYST pin and the VRDIV pin. The VRDIV pin is connected to one end of the resistor RUV2, and the other end of the resistor RUV2 is connected to one end of the resistor RUV1, and the other end of the resistor RUV1 is grounded. The VBAT-UV pin is connected to the other end of the resistor RUV2, the VRDIV pin is connected to one end of the resistor ROV2, and the other end of the resistor ROV2 is connected to one end of the resistor ROV1, and the other end of the resistor ROV1 is grounded. The VBAT-OV pin is connected to the other end of the resistor ROV2.

4. The self-powered methanol concentration sensing system for a direct methanol fuel cell according to claim 3, It is 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 output voltage of the power management module, 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 DVSS pin and AVSS pin; XIN pin is connected to one end of crystal oscillator X2, the other end of crystal oscillator X2 is connected to XOUT pin, XOUT pin is connected to one end of capacitor C7, the other end of capacitor C7 is grounded, the other end of capacitor C7 is connected to one end of crystal oscillator X2 Capacitor C8 is connected 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 end VOUT of the output voltage of the power management module; 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 correspondingly; 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, It is characterized in that The parameter settings of the fuel cell voltage detection module meet the following conditions: Wherein V1 is the output voltage of the operational amplifier T1, VOP is the operating voltage of the fuel cell, VFC is the inverting input voltage of the operational amplifier T2, VSEN is the voltage feedback value output by the operational amplifier T2; IFC is the current flowing through the resistor R1.

6. The self-powered methanol concentration sensing system for a direct methanol fuel cell according to claim 5, It is characterized in that In order to implement the maximum power tracking point algorithm of the power management module, the parameter setting of the boost converter chip satisfies the following formula: Where V REF_SAMP is the voltage value of the 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, It is 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, It is characterized in that In order to make the boost converter chip work within the normal operating voltage range, the parameter settings meet the following conditions: Where V BAT_OK_PROG When the VBAT pin voltage drops, the VBAT-OK pin voltage threshold value; V BAT_OK_HYST It is the voltage threshold of VBAT-OK pin when the voltage of VBAT pin rises.

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

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

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