A direct methanol fuel cell battery-free cold start bidirectional power management device and a cold start method thereof

Abstract

The application relates to a direct methanol fuel cell battery-free cold start bidirectional power management device and a cold start method thereof, and belongs to the technical field of direct methanol fuel cells. The device comprises a USB PD input and protocol unit, a synchronous step-up and step-down power conversion unit, a bidirectional power path control unit, an interface protection unit, a control unit and a voltage detection and state indication unit. Initial energy is obtained through an external portable USB PD fast charging power supply, and a full-process closed loop of DMFC auxiliary machine power supply, system start and battery charging is completed under the zero-voltage working condition of the energy storage battery. The application aims to solve the dead loop problem that the DMFC system cannot be started when the energy storage battery is completely discharged, and can realize real battery-free cold start, has the characteristics of bidirectional power efficient control, wide voltage adaptation and full-process automatic operation.

Description

Technical Field

[0001] This invention relates to the field of direct methanol fuel cells, and to a bidirectional power management device for cold start-up of direct methanol fuel cells without batteries, and more particularly to a bidirectional power management device for cold start-up of direct methanol fuel cells without batteries and its cold start method. Background Technology

[0002] Direct methanol fuel cell (DMFC) is a proton exchange membrane fuel cell that can directly convert the chemical energy of methanol into electrical energy at room temperature and pressure. It has core advantages such as convenient fuel storage and transportation, high energy density, fast start-up speed, low operating noise, and zero carbon emissions. It is widely used in field operations, emergency rescue, portable power supply, off-grid power generation and other scenarios without grid coverage.

[0003] The stable operation of a DMFC system relies on a supporting power management architecture. Its core operating logic is as follows: During the standby and startup phases, the supporting energy storage battery supplies power to the DMFC's auxiliary systems (hereinafter referred to as auxiliary equipment), including the methanol feed pump, air pump, solenoid valves, and main control board, to complete startup processes such as purging, preheating, and methanol feeding. After the DMFC successfully starts up and generates electricity stably, it supplies power to the load on one hand and charges the energy storage battery on the other, forming a complete power supply closed loop. With the commercialization of DMFC technology, higher requirements are placed on its power management system's emergency startup capability, operating condition adaptability, and operational reliability.

[0004] The following solutions are currently available to address the aforementioned issues: 1. Basic unidirectional power supply scheme: The energy storage battery is connected to the DMFC auxiliary power supply bus through devices such as diodes and relays, which can only realize unidirectional power supply from the battery to the DMFC; the output end of the DMFC is connected to the energy storage battery through an independent charging module, which can only realize unidirectional charging from the DMFC to the battery. The two paths are independent of each other and have no linkage control capability.

[0005] 2. Conventional cold start auxiliary solutions: For scenarios where the battery is depleted, existing solutions mostly use external power frequency AC power or high-power fixed DC auxiliary power to provide starting power for the DMFC auxiliary machine; some solutions use the battery management system (BMS) to set the minimum discharge cutoff voltage of the battery, forcibly retaining the battery's starting capacity and avoiding complete battery depletion.

[0006] 3. Bidirectional power management solution: A few high-end solutions use bidirectional DC / DC converters to realize bidirectional energy flow between the battery and the DMFC bus. However, they can only work when the battery has a basic voltage. They lack the ability to start cold when the battery is completely depleted, and the input and output voltage range is narrow, resulting in poor adaptability.

[0007] The above solution has the following drawbacks: 1. There is a core dead loop problem: it cannot achieve cold start in a completely depleted state. When the energy storage battery is completely depleted due to long-term storage, over-discharge, failure, or other reasons, the DMFC auxiliary machine has no power source and cannot start. The DMFC cannot generate electricity, and therefore cannot charge the energy storage battery, forming an unbreakable dead loop, causing the equipment to completely fail in emergency and field scenarios.

[0008] 2. Existing cold start solutions have extremely poor adaptability to various scenarios. Solutions using external power frequency AC power cannot be applied to outdoor or emergency scenarios without grid coverage; fixed high-power DC auxiliary power supplies are not portable and cannot meet the needs of mobile power supply; solutions that force the retention of battery capacity will significantly reduce the usable battery capacity and cannot solve extreme scenarios such as battery failure or complete over-discharge.

[0009] 3. Insufficient bidirectional power control capability and imperfect protection mechanism. Existing unidirectional power supply schemes suffer from large diode forward voltage drop, severe heat generation, and low efficiency; relay schemes suffer from contact arcing, short lifespan, and inability to achieve rapid reverse blocking; a few bidirectional schemes lack comprehensive protection against reverse connection, overvoltage, overcurrent, undervoltage lockout, and reverse backflow, making them prone to device burnout, battery overcharging, and DMFC backflow damage, resulting in low system reliability.

[0010] 4. Poor compatibility and inability to adapt to multiple system specifications. Most existing solutions are designed with a fixed voltage, which can only adapt to energy storage batteries of a single voltage level (12V or 24V) and cannot be compatible with DMFC systems of different power levels; the input voltage range is narrow, which cannot adapt to wide-range input sources such as portable fast charging power supplies, thus limiting application scenarios.

[0011] 5. Low level of automation and complex operation. Existing solutions mostly require manual intervention when switching operating conditions, starting charging, and handling faults. They cannot achieve fully automated control of the entire process. In emergency scenarios, the operation threshold is high, the response speed is slow, and equipment damage caused by human error is easy to occur. Summary of the Invention

[0012] To address the aforementioned technical problems, the present invention aims to provide a direct methanol fuel cell battery-free cold-start bidirectional power management device and its cold-start method.

[0013] To achieve the above objectives, the present invention adopts the following technical solution: A direct methanol fuel cell battery-free cold-start bidirectional power management device includes a USB PD fast charging power supply, a DMFC fuel cell system, and an energy storage battery. It also includes a USB PD input and protocol unit, a synchronous buck-boost power conversion unit, a bidirectional power path control unit, a control unit, and a voltage detection and status indication unit. The output of the USB PD fast charging power supply is connected to the input of the USB PD input and protocol unit. The output of the USB PD input and protocol unit is connected to the input of the synchronous buck-boost power conversion unit. The output of the synchronous buck-boost power conversion unit is connected to the input of the bidirectional power path control unit. The bidirectional power path control unit is interconnected with the DMFC fuel cell system and the energy storage battery. The output of the bidirectional power path control unit is connected to the input of the voltage detection and status indication unit. The output of the voltage detection and status indication unit is connected to the input of the control unit. The output of the control unit is connected to the inputs of the USB PD input and protocol unit, the synchronous buck-boost power conversion unit, and the bidirectional power path control unit.

[0014] Preferably, in the direct methanol fuel cell battery-free cold start bidirectional power management device, the USBPD input and protocol unit includes a USB-C interface, a PD protocol chip, a 3.3V LDO voltage regulator module, and an ESD electrostatic protection module. The input terminal of the USB-C interface is connected to the output terminal of the USB PD fast charging power supply, the output terminal of the USB-C interface is connected to the input terminal of the PD protocol chip, the output terminal of the PD protocol chip is connected to the input terminal of the 3.3V LDO voltage regulator module, and the ESD electrostatic protection module is connected in parallel to the USB-C interface. The PD protocol chip is model HUSB238; the 3.3V LDO voltage regulator module is model NCV8730; and the ESD electrostatic protection module uses a chip model USB4056.

[0015] Preferably, in the direct methanol fuel cell battery-free cold-start bidirectional power management device, the synchronous buck-boost power conversion unit includes a chip U8. The VIN pin of chip U8 connects the USB PD input to the output of the protocol unit; the input voltage range covers 4.5V~60V, perfectly adapting to the full range of PD power supply input from 5V to 20V; The HO / LO pins of chip U8 are connected to an external half-bridge drive circuit and connected to the gate of synchronous switch Q11. The SW pin of chip U8 is connected to one end of power inductor L1, and the other end of power inductor L1 is connected to the VFC output bus (DMFC auxiliary power supply bus) of the device. The feedback voltage regulator unit is connected to the VFC output bus through voltage divider resistors R55 and R56. The voltage divider signal is connected to the FB pin of chip U8 to realize closed-loop control of the output voltage. By adjusting the resistance value of the voltage divider resistor, the output voltage can be configured to cover 12V~24V to adapt to DMFC systems of different voltage levels. The current sampling resistor RS1 is connected in series in the power circuit, and the sampling signal is connected to the ISNS pin of the chip U8 to realize input and output overcurrent protection and short circuit protection, so as to avoid overload damage to the device during the startup process.

[0016] Preferably, the direct methanol fuel cell battery-free cold start bidirectional power management device uses chip U8 model LM25148QRGYQ1.

[0017] Preferably, in the direct methanol fuel cell battery-free cold start bidirectional power management device, the bidirectional power path control unit, used to realize bidirectional energy flow and operating condition switching between the DMFC and the energy storage battery, includes an independent battery-to-fuel cell power supply module, a fuel cell-to-battery charging module, and a cold start output anti-reverse module. The cold start output reverse protection module includes a gate driver U9 and a synchronous MOSFET Q10. The sixth pin of the gate driver U9 is connected to the output of the synchronous buck-boost power converter unit, and the second pin of the gate driver U9 is connected to the gate of the MOSFET Q10. The drain of the MOSFET Q10 is connected to the output of the synchronous buck-boost power converter unit, and the source of the MOSFET Q10 is connected to the VFC bus. The cold start output reverse protection module has a built-in 3.4V undervoltage lockout (UVLO), which turns on the MOSFET Q10 only when the output voltage of the synchronous buck-boost power converter unit is normal, achieving zero-dropout conduction. Among them, the gate driver U9 is an NCV6826, and the synchronous MOSFET Q10 is a CSD87312Q3E; it also has reverse blocking capability to prevent the voltage from flowing back to the front-end power conversion module after the DMFC starts up. The battery-to-fuel cell power supply module includes a gate driver U1 and a synchronous MOSFET Q1. The second pin of the gate driver U1 is connected to the gate of the synchronous MOSFET Q1, the drain of the MOSFET Q1 is connected to the VBAT bus of the energy storage battery interface, and the source of the MOSFET Q1 is connected to the VFC bus. Among them, the gate driver U1 is model NCV6826, and the synchronous MOSFET Q1 is model CSD87312Q3E. Under normal operating conditions, the energy storage battery supplies power to the DMFC auxiliary machine through this branch, realizing the energy flow from the battery to the DMFC, and also has reverse blocking, undervoltage lockout and overcurrent protection functions. The fuel cell to battery charging module includes a gate driver U2, a synchronous MOSFET Q3, and a synchronous MOSFET Q4, which are connected in parallel. The second pin of gate driver U2 is connected to the gates of synchronous MOSFETs Q4 and Q3. The sources of synchronous MOSFETs Q4 and Q3 are connected to the VFC bus, and the drains of synchronous MOSFETs Q4 and Q3 are connected to the VBAT bus. Gate driver U2 is an NCV6826, and synchronous MOSFETs Q3 and Q4 are both CSD87312Q3E. When the DMFC starts generating electricity and the VFC bus voltage is higher than the battery voltage, this branch automatically turns on, enabling the DMFC to supply charging energy to the energy storage battery. It also features reverse blocking, overvoltage and overcurrent protection, and automatic shutdown when the battery is fully charged.

[0018] Preferably, in the direct methanol fuel cell battery cold start bidirectional power management device, the control unit uses an STM32F070F6P6 chip.

[0019] Preferably, in the direct methanol fuel cell battery-free cold start bidirectional power management device, the voltage detection and status indication unit includes a voltage divider sampling module, a dual-channel voltage comparator, an LED status indication module, and a mode selection switch module. The voltage divider sampling module is connected in parallel to the VFC bus and the VBAT bus respectively; The dual-channel voltage comparator has its output connected to the input of the voltage divider sampling module. The dual-channel voltage comparator uses the SGM8772XMS10G chip, which has a built-in reference voltage source. By configuring the voltage divider resistor values, the voltage detection threshold, undervoltage and overvoltage protection threshold, and charging start / stop threshold of the 12V~24V battery can be set. The LED status indicator module provides a visual indication of the system's operating status. The input of the LED status indicator module is connected to the output of a dual-channel voltage comparator, which includes a battery voltage level indicator, a DMFC operating status indicator, a charging status indicator, and a fault alarm indicator. The mode selection switch module is connected to the control unit and is configured with four positions: OFF / USB-C, Battery, AUTO / 12V, and 24V. The device's operating mode can be manually selected, and manual adaptation of 12V~24V energy storage batteries can be achieved. The AUTO position can automatically identify the battery voltage level.

[0020] Preferably, the direct methanol fuel cell battery-free cold start bidirectional power management device further includes an interface protection unit, which includes a DMFC interface, an energy storage battery interface, and a debugging and downloading interface. The DMFC interface is a 2-pin reverse connection protection terminal block connected in parallel with an SMBJ28A TVS transient suppression diode. It connects the VFC bus to the DMFC system output to achieve overvoltage and electrostatic protection, and is marked with a reverse connection protection label. The energy storage battery interface is a 2-pin reverse connection protection terminal block connected in parallel with an SMBJ28A TVS transient suppression diode, which connects the VBAT bus to the positive and negative terminals of the energy storage battery. A 30A fuse is connected in series at the front end of the interface to achieve short circuit and extreme overload protection, and is also marked with a reverse connection protection label. The debugging and download interface is an SWD serial debugging interface, which connects to the debugging pin of the control unit to realize program burning, online debugging and parameter configuration.

[0021] A direct methanol fuel cell battery-free cold start method includes the following steps: Step 1: Connect the USB-C PD fast charging power supply to the device interface. The control unit controls the PD protocol chip to negotiate with the external power supply to obtain high voltage DC input. The 3.3 VLDO unit starts to supply power to the control unit and various functional modules. The device completes power-on initialization. Step 2: The control unit controls the synchronous buck-boost power conversion unit to start, stabilizes the PD input voltage to the rated operating voltage of the DMFC auxiliary machine, and simultaneously controls the cold start output anti-reverse branch to conduct, so that the power is delivered to the VFC bus to power the DMFC auxiliary machine. Step 3: After the DMFC auxiliary machine receives power, it completes the purging, preheating, and feeding start-up process. The DMFC stack starts generating electricity, and the VFC bus voltage rises and stabilizes within the rated operating range. Step 4: The voltage detection and status indication unit collects the VFC bus voltage and transmits it to the control unit. After the control unit recognizes that the DMFC power generation is stable, it controls the fuel cell to battery charging branch to be turned on, and the electrical energy output by the DMFC charges the energy storage battery. Step 5: After the control unit detects that the energy storage battery voltage has returned to the normal operating range, the control system switches to the normal operating mode, the battery to fuel cell power supply branch enters standby mode, and after disconnecting the external PD power supply, the DMFC system runs independently, completing the cold start closed loop.

[0022] By means of the above-described solution, the present invention has at least the following advantages: 1. This invention breaks the cold start dead loop of DMFC systems, achieving true battery-free cold start. This invention obtains initial energy through a USB PD portable fast-charging power supply, eliminating the need for an external power grid or high-power auxiliary power source. Even under extreme conditions where the energy storage battery is completely depleted, it completes the entire closed-loop process of DMFC auxiliary power supply, system startup, and battery charging. This is perfectly suited for scenarios without grid coverage, such as in the field and emergency rescue, significantly improving the environmental adaptability and emergency response capabilities of the DMFC system.

[0023] 2. This invention features a highly efficient and controllable bidirectional power path, with end-to-end protection significantly improving system reliability. The invention employs a diode topology of "high-side gate drive + synchronous MOSFET" to achieve zero-voltage drop conduction in the power path. Compared to traditional diode solutions, conduction losses are reduced by more than 80%, heat generation is significantly reduced, and system efficiency is significantly improved. Simultaneously, it possesses nanosecond-level reverse blocking capability, completely eliminating the risk of reverse backflow. Combined with end-to-end protection against reverse connection, overvoltage, overcurrent, undervoltage, and ESD, it achieves full-condition safety protection, increasing the device's mean time between failures (MTBF) by more than three times and significantly extending the lifespan of the DMFC system and energy storage battery.

[0024] 3. This invention offers wide compatibility and strong versatility. Its PD input is compatible with the full range of USB PD fast charging power supplies from 5V to 20V. The synchronous buck-boost power conversion unit's input range covers 4.5V to 60V, and its output is compatible with the full range of DMFC systems from 12V to 24V. The energy storage battery supports automatic identification and manual adaptation to both 12V and 24V specifications. It can be directly connected in series between existing DMFC systems and energy storage batteries without requiring hardware modifications to the original system. It is compatible with the full range of DMFC devices from 100W to 3000W, making its application extremely easy to promote.

[0025] 4. This invention enables fully automated control of the entire process, significantly improving ease of operation. Through voltage detection and a core MCU, this invention achieves fully automated system status identification, automatically completing the entire process control of PD negotiation, voltage regulation output, power path switching, charging startup, and protection shutdown. In AUTO mode, no manual operation is required to complete the cold start and normal operating condition switching, greatly reducing the operational threshold, improving response speed in emergency scenarios, and completely avoiding equipment damage caused by human error.

[0026] 5. This invention enables a highly integrated, miniaturized design with excellent portability. It integrates the PD protocol, power conversion, bidirectional path control, protection detection, and logic control onto two PCB boards. The compact size allows for direct installation within the DMFC system chassis without additional space. It also supports portable external use, catering to the application needs of both fixed and portable DMFC systems.

[0027] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0029] Figure 1 This is a schematic diagram of the principle of the present invention; Figure 2 This is a schematic block diagram of the USB PD input and protocol unit of the present invention; Figure 3a This is the actual circuit diagram of the PD protocol chip and ESD electrostatic protection module of the present invention; Figure 3b This is the actual circuit diagram of the 3.3V LDO voltage regulator module of the present invention; Figure 4 This is the actual circuit diagram of the synchronous buck-boost power conversion unit of the present invention; Figure 5 This is a schematic block diagram of the bidirectional power path control unit of the present invention; Figure 6 This is the actual circuit diagram of the cold start output anti-reverse module of the present invention; Figure 7 This is the actual circuit diagram of the battery-to-fuel cell power supply module of the present invention; Figure 8 This is the actual circuit diagram of the fuel cell to battery charging module of the present invention; Figure 9 This is a block diagram illustrating the principle of the voltage detection and status indication unit of the present invention; Figure 10 This is the actual circuit diagram of the dual-channel voltage comparator of the present invention; Figure 11 This is the actual circuit diagram of the control unit of the present invention; Figure 12 This is the actual circuit diagram of the energy storage battery interface of the present invention. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0031] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0032] Example like Figures 1 to 12 As shown, a direct methanol fuel cell battery-free cold-start bidirectional power management device includes a USB PD fast charging power supply 1, a DMFC fuel cell system 2 (including auxiliary power supply bus VFC), and an energy storage battery 3 (bus VBAT). It also includes a USB PD input and protocol unit 4, a synchronous buck-boost power conversion unit 5, a bidirectional power path control unit 6, a control unit 8, and a voltage detection and status indication unit 9. The output terminal of the USB PD fast charging power supply 1 is connected to the input terminal of the USB PD input and protocol unit 4. The output terminal of the USB PD input and protocol unit 4 is connected to the input terminal of the synchronous buck-boost power conversion unit 5. The output terminal of the synchronous buck-boost power conversion unit 5 is connected to the input terminal of the bidirectional power path control unit 6. The bidirectional power path control unit 6 is interconnected with the DMFC fuel cell system 2 and the energy storage battery 3. The output terminal of the bidirectional power path control unit 6 is connected to the input terminal of the voltage detection and status indication unit 9. The output terminal of the voltage detection and status indication unit 9 is connected to the input terminal of the control unit 8. The output terminal of the control unit 8 is connected to the USB PD input and protocol unit 4. The PD input is connected to the input terminals of protocol unit 4, synchronous buck-boost power conversion unit 5, and bidirectional power path control unit 6.

[0033] In this embodiment, the USB PD input and protocol unit 4 includes a USB-C interface 41, a PD protocol chip 42, a 3.3V LDO voltage regulator module 43, and an ESD electrostatic protection module 44. The input terminal of the USB-C interface 41 is connected to the output terminal of the USB PD fast charging power supply 1, the output terminal of the USB-C interface 41 is connected to the input terminal of the PD protocol chip 42, the output terminal of the PD protocol chip 42 is connected to the input terminal of the 3.3V LDO voltage regulator module 43, and the ESD electrostatic protection module 44 is connected in parallel to the USB-C interface 41. The PD protocol chip is model HUSB238; its VIN pin is connected to the VBUS pin of the USB-C interface, and the CC1 / CC2 pins are connected to the CC pin of the USB-C interface. The input current limit of 3.25A is set by connecting an external resistor to the ISET pin, and the PD negotiation maximum output level of 20V is configured by connecting an external resistor to the RPD pin, so as to realize fast charging protocol negotiation with the external PD power supply and obtain a stable high voltage DC input. The 3.3V LDO voltage regulator module uses the NCV8730 model. Its input pin is connected to the output of the PD protocol chip, and the output provides a stable 3.3V DC power supply to the PD protocol chip, the core control module, and the debugging interface. The ESD protection module uses a USB4056 chip, which is connected in parallel between the signal pins of the USB-C interface and ground to provide electrostatic protection during interface insertion and removal, preventing device breakdown and damage.

[0034] In this embodiment, the synchronous buck-boost power conversion unit 5 includes a chip U8, wherein the chip U8 is model LM25148QRGYQ1; The VIN pin of chip U8 connects the USB PD input to the output of protocol unit 4; the input voltage range covers 4.5V~60V, and it is compatible with the full range of USB PD power supply input from 5V to 20V. The HO / LO pins of chip U8 are connected to an external half-bridge drive circuit (resistors R64 and R65 and / or resistors R62 and R63), which is connected to the gate of synchronous switch Q11. The SW pin of chip U8 is connected to one end of power inductor L1, and the other end of power inductor L1 is connected to the VFC output bus and DMFC auxiliary power supply bus of the device. The feedback voltage regulator unit is connected to the VFC output bus through voltage divider resistors R55 and R56. The voltage divider signal is connected to the FB pin of chip U8 to realize closed-loop control of the output voltage. By adjusting the resistance value of the voltage divider resistor, the output voltage can be configured to cover 12V~24V to adapt to DMFC systems of different voltage levels. The current sampling resistor RS1 is connected in series in the power circuit, and the sampling signal is connected to the ISNS pin of the chip U8 to realize input and output overcurrent protection and short circuit protection, so as to avoid overload damage to the device during the startup process.

[0035] In this embodiment, the bidirectional power path control unit 6 is used to realize bidirectional energy flow and operating condition switching between the DMFC and the energy storage battery. It includes an independent battery-to-fuel cell power supply module 61, a fuel cell-to-battery charging module 62, and a cold start output anti-reverse module 63. The cold start output reverse protection module 63 has two parallel branches, each including a gate driver U9 and a synchronous MOSFET Q10. The sixth pin of the gate driver U9 is connected to the output terminal of the synchronous buck-boost power conversion unit 5, and the second pin of the gate driver U9 is connected to the gate of the MOSFET Q10. The drain of the MOSFET Q10 is connected to the output terminal of the synchronous buck-boost power conversion unit 5, and the source of the MOSFET Q10 is connected to the VFC bus. The cold start output reverse protection module 63 has a built-in 3.4V undervoltage lockout (UVLO), which turns on the MOSFET Q10 only when the output voltage of the synchronous buck-boost power conversion unit 5 is normal, achieving zero voltage drop conduction. At the same time, it has reverse blocking capability to prevent the voltage from flowing back to the front-end power conversion module after the DMFC starts. Among them, the gate driver U9 uses the NCV6826 model, and the synchronous MOSFET Q10 uses the CSD87312Q3E model; The battery-to-fuel cell power supply module 61 includes a gate driver U1 and a synchronous MOSFET Q1. The second pin of the gate driver U1 is connected to the gate of the synchronous MOSFET Q1. The drain of the MOSFET Q1 is connected to the VBAT bus of the energy storage battery interface 3. The source of the MOSFET Q1 is connected to the VFC bus. Under normal operating conditions, the energy storage battery supplies power to the DMFC auxiliary machine through the battery-to-fuel cell power supply module 61, realizing the energy flow from the battery to the DMFC. It also has reverse blocking, undervoltage lockout, and overcurrent protection functions. Among them, the gate driver U1 is model NCV6826, and the synchronous MOSFET Q1 is model CSD87312Q3E; The fuel cell to battery charging module 62 includes a gate driver U2, a synchronous MOSFET Q3, and a synchronous MOSFET Q4. The synchronous MOSFETs Q3 and Q4 are connected in parallel. The second pin of the gate driver U2 is connected to the gate of the synchronous MOSFETs Q4 and Q3. The source of the synchronous MOSFETs Q4 and Q3 is connected to the VFC bus, and the drain of the synchronous MOSFETs Q4 and Q3 is connected to the VBAT bus. When the DMFC starts generating electricity and the VFC bus voltage is higher than the battery voltage, this branch is automatically turned on to realize the flow of charging energy from the DMFC to the energy storage battery. It also has reverse blocking, overvoltage and overcurrent protection, and automatic shutdown function when the battery is fully charged. Among them, the gate driver U2 is model NCV6826, and the synchronous MOSFETs Q3 and Q4 are both model CSD87312Q3E.

[0036] In this embodiment, the control unit 8 uses an STM32F070F6P6 chip. The control unit 8 connects to the PD protocol chip via an I2C bus, to a voltage sampling unit via an ADC pin, and to a gate driver, voltage comparator, and status indicator unit via GPIO pins, thus achieving full system logic control. The control unit 8 includes: PD fast charging protocol negotiation control, synchronous buck-boost voltage regulation closed-loop control, three power path on / off linkage control, automatic identification of battery voltage and DMFC status, charging start / stop and protection control, and fault alarm and emergency shutdown control.

[0037] In this embodiment, the voltage detection and status indication unit 9 includes a voltage divider sampling module 91, a dual-channel voltage comparator 92, an LED status indication module 93, and a mode selection switch module 94. Voltage divider sampling module 91, the voltage divider sampling module is connected in parallel to VFC bus and VBAT bus respectively; The output of the voltage divider sampling module 91 is connected to the input of the dual-channel voltage comparator 92. The dual-channel voltage comparator 92 uses the SGM8772XMS10G chip, which has a built-in reference voltage source. By configuring the voltage divider resistor value, the voltage detection threshold, undervoltage and overvoltage protection threshold, and charging start / stop threshold of the 12V~24V battery can be set. LED status indicator module 93 enables visual indication of system operating conditions. The input terminal of LED status indicator module 93 is connected to the output terminal of dual-channel voltage comparator 92. It includes battery voltage level indicator, DMFC operation status indicator, charging status indicator and fault alarm indicator. The mode selection switch module 94 is configured with four positions: OFF / USB-C, Battery, AUTO / 12V, and 24V. It allows manual selection of the device's operating mode and enables manual adaptation of 12V / 24V energy storage batteries. The AUTO position enables automatic identification of the battery voltage level.

[0038] In this embodiment, the interface protection unit 7 includes a DMFC interface, an energy storage battery interface, and a debug download interface; The DMFC interface is a 2-pin reverse connection protection terminal block connected in parallel with an SMBJ28A TVS transient suppression diode. It connects the VFC bus to the DMFC system output to achieve overvoltage and electrostatic protection, and is marked with a reverse connection protection label. The energy storage battery interface is a 2-pin reverse connection protection terminal block connected in parallel with an SMBJ28A TVS transient suppression diode, which connects the VBAT bus to the positive and negative terminals of the energy storage battery. A 30A fuse is connected in series at the front end of the interface to achieve short circuit and extreme overload protection, and is also marked with a reverse connection protection label. The debugging and download interface is an SWD serial debugging interface, which connects to the debugging pin of the control unit to realize program burning, online debugging and parameter configuration; The circuitry covers all power interfaces with full-link protection, including reverse connection protection, overvoltage TVS protection, overcurrent sampling protection, undervoltage lockout protection, reverse backflow protection, and ESD electrostatic discharge protection module, achieving full-condition safety protection.

[0039] Under the condition of a completely depleted energy storage battery: Step 1: Connect the USB-C PD fast charging power supply to the device interface. The control unit controls the PD protocol chip to negotiate with the external power supply to obtain high voltage DC input. The 3.3 VLDO unit starts to supply power to the control unit and various functional modules. The device completes power-on initialization. Step 2: The control unit controls the synchronous buck-boost power conversion unit to start, stabilizes the PD input voltage to the rated operating voltage of the DMFC auxiliary machine, and simultaneously controls the cold start output anti-reverse branch to conduct, so that the power is delivered to the VFC bus to power the DMFC auxiliary machine. Step 3: After the DMFC auxiliary machine receives power, it completes the purging, preheating, and feeding start-up process. The DMFC stack starts generating electricity, and the VFC bus voltage rises and stabilizes within the rated operating range. Step 4: The voltage detection and status indication unit collects the VFC bus voltage and transmits it to the control unit. After the control unit recognizes that the DMFC power generation is stable, it controls the fuel cell to battery charging branch to be turned on, and the electrical energy output by the DMFC charges the energy storage battery. Step 5: After the control unit detects that the energy storage battery voltage has returned to the normal operating range, the control system switches to the normal operating mode, the battery to fuel cell power supply branch enters standby mode, and after disconnecting the external PD power supply, the DMFC system runs independently, completing the cold start closed loop.

[0040] Under normal operating conditions of the energy storage battery voltage: When the device switches to AUTO mode, the battery to fuel cell power supply module is automatically turned on. The energy storage battery supplies power to the VFC bus through the VBAT bus, providing power for the DMFC standby, preheating, and startup. After the DMFC starts and generates electricity stably, the VFC bus voltage is higher than the battery voltage, and the fuel cell to battery charging module is automatically turned on. The DMFC replenishes the energy storage battery, realizing fully automatic switching of operating conditions without manual intervention.

[0041] Fault Protection Workflow When the system encounters abnormal operating conditions such as reverse connection of interface, input overvoltage, output short circuit, overcurrent, battery undervoltage / overvoltage, or DMFC reverse flow, the protection circuit of the corresponding module will immediately activate, shut down the MOSFET of the corresponding power path, and the fault indicator light will illuminate. The core control module will execute emergency shutdown logic to prevent device damage. After the fault is cleared, normal operation will automatically resume.

[0042] Example 1 Battery-free cold start implementation of a 12V energy storage battery DMFC system: This first embodiment applies to a 1000W 12V rated voltage DMFC portable emergency power supply system, equipped with a 12V / 100Ah lithium iron phosphate energy storage battery. The specific implementation method is as follows: 1. Device parameter configuration: The output voltage of the synchronous buck-boost power conversion unit is configured to 13.8V. The voltage detection module is set with 12V battery detection thresholds: undervoltage protection threshold 10V, overvoltage protection threshold 15V, charging start threshold 12.5V, and charging stop threshold 14.6V. The PD protocol chip is configured to negotiate a maximum input of 20V / 3.25A with a current limit of 3.25A. 2. Initial operating condition: The energy storage battery is completely depleted due to long-term storage, with a terminal voltage of 0V. The DMFC system is in a shutdown state and has no power source. 3. Cold start operation: Connect the 65W 20V output PD fast charging power bank to the USB-C port of the device. The device will power on and initialize. The PD protocol chip will successfully negotiate with the power bank and obtain 20V DC input. 4. Power Conversion and Auxiliary Power Supply: The synchronous buck-boost power conversion unit starts up, converting the 20V input to a stable 13.8V output. The cold start output reverse protection branch is turned on, and the 13.8V voltage is delivered to the VFC bus to power the DMFC's 12V main control board, methanol pump, and air pump, and the auxiliary equipment starts up and runs. 5. DMFC Start-up and Power Generation: The DMFC auxiliary machine completes methanol feeding and purging in 30 seconds, the stack is successfully started, the no-load output voltage rises to 14.2V, and stabilizes at 13.8V under load, and the VFC bus voltage is stable. 6. Battery charging start-up: The voltage detection module recognizes that the DMFC power generation is stable and the VFC bus voltage is higher than the battery terminal voltage. The fuel cell to battery charging branch is automatically turned on, and the DMFC charges the energy storage battery with a constant current of 10A. 7. Operating mode switching: After charging for 2 hours, the battery terminal voltage rises to 12.6V, reaching the normal operating voltage range. The system automatically switches to normal operating mode, and the battery to fuel cell power supply branch enters standby mode. At this time, the PD fast charging power bank is unplugged, and the DMFC system operates independently and normally, completing the cold start process.

[0043] Example 2 Normal operation and charging implementation of 24V energy storage battery DMFC system This second embodiment applies to a 2000W 24V rated voltage DMFC off-grid power generation system, equipped with a 24V / 200Ah lithium iron phosphate energy storage battery. The specific implementation method is as follows: 1. Device parameter configuration: The output voltage of the synchronous buck-boost power converter is configured to 27.6V. The voltage detection module is set to a 24V battery detection threshold: undervoltage protection threshold 20V, overvoltage protection threshold 30V, charging start threshold 25V, and charging stop threshold 29.2V; the mode selection switch is switched to AUTO. 2. Standby mode: The energy storage battery terminal voltage is 25.2V, the power is sufficient, the DMFC system is in standby mode, and the load is off; 3. Start-up power supply: When the load starts and the DMFC system receives the start-up command, the battery to fuel cell power supply branch is automatically turned on. The energy storage battery outputs 24V voltage to the VFC bus through the VBAT bus to power the DMFC auxiliary equipment. The DMFC completes the start-up process and the stack begins to generate electricity. 4. Power generation and charging switching: After the DMFC stack generates power stably, the VFC bus voltage stabilizes at 27.6V, which is higher than the battery terminal voltage. The fuel cell to battery charging branch is automatically turned on. The DMFC supplies power to the load on one hand and charges the energy storage battery with a current of 20A on the other. 5. Full charge shutdown: When the battery terminal voltage rises to 29.2V, reaching the full charge threshold, the voltage detection module outputs a signal, and the fuel cell to battery charging branch is automatically shut off to stop charging and avoid overcharging the battery; when the load is turned off and the DMFC system is shut down, the device automatically switches to standby mode, and the battery to fuel cell power supply branch remains in standby mode, waiting for the next start command, without any manual intervention.

[0044] Example 3 Fault protection implementation This third embodiment verifies the end-to-end protection capability of the present invention for common system fault scenarios. The specific implementation method is as follows: 1. Reverse connection protection: When the positive and negative terminals of the energy storage battery interface are reversed, the TVS diode and the reverse connection protection circuit will immediately activate, shutting off the MOSFETs in all power paths, illuminating the fault alarm indicator, and locking the device output of the core control module to prevent battery short circuit and device burnout. The interface will automatically unlock after the positive and negative terminals are correctly connected. 2. Output short circuit protection: When a short circuit fault occurs on the VFC bus, the current sampling unit of the synchronous buck-boost power converter detects the short circuit current, turns off the power switch within 1μs, stops the output, and issues a fault alarm. After the short circuit fault is cleared, normal operation is automatically restored. 3. Reverse backflow protection: When the DMFC generator voltage rises abnormally and exceeds the output voltage of the synchronous buck-boost power converter unit, the cold start output reverse protection branch is immediately shut off to achieve reverse blocking and prevent high voltage backflow from damaging the PD power supply and the front-end power conversion devices; Battery overcharge protection: When the charging voltage of the energy storage battery reaches the overvoltage protection threshold, the fuel cell battery charging branch is immediately shut off to stop charging, and a fault alarm is triggered at the same time to avoid the risk of battery bulging and fire caused by overcharging.

[0045] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0046] In the description of this application, it should be noted that the terms "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use. They are used only for the convenience of describing this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0047] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or vertical, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0048] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0049] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A direct methanol fuel cell battery-free cold-start bidirectional power management device, comprising a USB PD fast charging power supply (1), a DMFC fuel cell system (2), and an energy storage battery (3), characterized in that: The system includes a USB PD input and protocol unit (4), a synchronous buck-boost power conversion unit (5), a bidirectional power path control unit (6), a control unit (8), and a voltage detection and status indication unit (9). The output terminal of the USB PD fast charging power supply (1) is connected to the input terminal of the USB PD input and protocol unit (4). The output terminal of the USB PD input and protocol unit (4) is connected to the input terminal of the synchronous buck-boost power conversion unit (5). The output terminal of the synchronous buck-boost power conversion unit (5) is connected to the input terminal of the bidirectional power path control unit (6). The bidirectional power path control unit (6) is interactively connected to the DMFC fuel cell system (2). The bidirectional power path control unit (6) is interactively connected to the energy storage battery (3). The output terminal of the bidirectional power path control unit (6) is connected to the input terminal of the voltage detection and status indication unit (9). The output terminal of the voltage detection and status indication unit (9) is connected to the input terminal of the control unit (8). The output terminal of the control unit (8) is connected to the input terminals of the USB PD input and protocol unit (4), the synchronous buck-boost power conversion unit (5), and the bidirectional power path control unit (6).

2. The direct methanol fuel cell battery-free cold-start bidirectional power management device according to claim 1, characterized in that: The USB PD input and protocol unit (4) includes a USB-C interface (41), a PD protocol chip (42), a 3.3V LDO voltage regulator module (43), and an ESD electrostatic protection module (44). The input terminal of the USB-C interface (41) is connected to the output terminal of the USB PD fast charging power supply (1). The output terminal of the USB-C interface (41) is connected to the input terminal of the PD protocol chip (42). The output terminal of the PD protocol chip (42) is connected to the input terminal of the 3.3V LDO voltage regulator module (43). The ESD electrostatic protection module (44) is connected in parallel on the USB-C interface (41).

3. The direct methanol fuel cell battery-free cold-start bidirectional power management device according to claim 1, characterized in that: The synchronous buck-boost power conversion unit (5) includes chip U8. The VIN pin of chip U8 is connected to the USB PD input and the output of protocol unit (4); The HO / LO pins of chip U8 are connected to an external half-bridge drive circuit and connected to the gate of synchronous switch Q11. The SW pin of chip U8 is connected to one end of power inductor L1, and the other end of power inductor L1 is connected to the VFC output bus of the device. The feedback voltage regulator unit is connected to the VFC output bus through voltage divider resistors R55 and R56, and the voltage divider signal is connected to the FB pin of chip U8 to realize closed-loop control of the output voltage. The current sampling resistor RS1 is connected in series in the power circuit, and the sampling signal is connected to the ISNS pin of chip U8 to realize input and output overcurrent protection and short circuit protection.

4. The direct methanol fuel cell battery-free cold-start bidirectional power management device according to claim 1, characterized in that: The bidirectional power path control unit (6) is used to realize bidirectional energy flow and operating condition switching between DMFC and energy storage battery. It includes an independent battery to fuel cell power supply module (61), fuel cell to battery charging module (62), and cold start output anti-reverse module (63). The cold start output reverse protection module (63) includes a gate driver U9 and a synchronous MOSFET Q10. The sixth pin of the gate driver U9 is connected to the output terminal of the synchronous buck-boost power conversion unit (5). The second pin of the gate driver U9 is connected to the gate of the MOSFET Q10. The drain of the MOSFET Q10 is connected to the output terminal of the synchronous buck-boost power conversion unit (5). The source of the MOSFET Q10 is connected to the VFC bus. The cold start output reverse protection module (63) has a built-in 3.4V undervoltage lockout (UVLO). The MOSFET Q10 is turned on only when the output voltage of the synchronous buck-boost power conversion unit (5) is normal, so as to achieve zero voltage drop conduction.

5. The direct methanol fuel cell battery-free cold-start bidirectional power management device according to claim 4, characterized in that: The battery-to-fuel cell power supply module (61) includes a gate driver U1 and a synchronous MOSFET Q1. The second pin of the gate driver U1 is connected to the gate of the synchronous MOSFET Q1, the drain of the MOSFET Q1 is connected to the VBAT bus of the energy storage battery (3) interface, and the source of the MOSFET Q1 is connected to the VFC bus.

6. The direct methanol fuel cell battery-free cold-start bidirectional power management device according to claim 4, characterized in that: The fuel cell to battery charging module (62) includes a gate driver U2, a synchronous MOSFET Q3, and a synchronous MOSFET Q4, wherein the synchronous MOSFET Q3 and the synchronous MOSFET Q4 are connected in parallel. The second pin of the gate driver U2 is connected to the gate of synchronous MOSFETs Q4 and Q3. The source of synchronous MOSFETs Q4 and Q3 is connected to the VFC bus, and the drain of synchronous MOSFETs Q4 and Q3 is connected to the VBAT bus.

7. The direct methanol fuel cell battery-free cold-start bidirectional power management device according to claim 1, characterized in that: The control unit (8) uses an STM32F070F6P6 chip.

8. The direct methanol fuel cell battery-free cold-start bidirectional power management device according to claim 1, characterized in that: The voltage detection and status indication unit (9) includes a voltage divider sampling module (91), a dual-channel voltage comparator (92), an LED status indication module (93), and a mode selection switch module (94). The voltage divider sampling module (91) is connected in parallel to the VFC bus and the VBAT bus respectively; The output of the voltage divider sampling module (91) is connected to the input of the dual-channel voltage comparator (92); LED status indicator module (93) realizes the visual indication of system operating conditions. The input terminal of LED status indicator module (93) is connected to the output terminal of dual-channel voltage comparator (92), which includes battery voltage level indicator, DMFC operation status indicator, charging status indicator and fault alarm indicator. The mode selection switch module (94) is configured with four positions: OFF / USB-C, Battery, AUTO / 12V, and 24V.

9. A cold start method for a direct methanol fuel cell battery-free cold start bidirectional power management device according to any one of claims 1 to 8, characterized in that, Includes the following steps: Step 1: Connect the USB-C PD fast charging power supply to the device interface. The control unit controls the PD protocol chip to negotiate with the external power supply to obtain high voltage DC input. The 3.3 VLDO unit starts to supply power to the control unit and various functional modules. The device completes power-on initialization. Step 2: The control unit controls the synchronous buck-boost power conversion unit to start, stabilizes the PD input voltage to the rated operating voltage of the DMFC auxiliary machine, and simultaneously controls the cold start output anti-reverse branch to conduct, so that the power is delivered to the VFC bus to power the DMFC auxiliary machine. Step 3: After the DMFC auxiliary machine receives power, it completes the purging, preheating, and feeding start-up process. The DMFC stack starts generating electricity, and the VFC bus voltage rises and stabilizes within the rated operating range. Step 4: The voltage detection and status indication unit collects the VFC bus voltage and transmits it to the control unit. After the control unit recognizes that the DMFC power generation is stable, it controls the fuel cell to battery charging branch to be turned on, and the electrical energy output by the DMFC charges the energy storage battery. Step 5: After the control unit detects that the energy storage battery voltage has returned to the normal operating range, the control system switches to the normal operating mode, the battery to fuel cell power supply branch enters standby mode, and after disconnecting the external PD power supply, the DMFC system runs independently, completing the cold start closed loop.

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