A bidirectional power supply module and control method for electric vehicles with ultra-wide voltage adaptability

Abstract

This invention relates to the field of electric vehicle battery capacity expansion technology, specifically to an ultra-wide voltage adaptability bidirectional power supply module and control method for electric vehicles. The module employs a four-phase interleaved parallel topology and silicon carbide devices to achieve wide voltage range adaptability. The control method includes: waking up via the edge of the optocoupler-isolated key ignition signal and performing multi-level self-testing and soft-start to reduce standby power consumption to the microampere level; identifying the charging status without protocol by detecting the voltage of the 12V auxiliary power supply pin of the charging pile and performing step-down charging; autonomously determining the SOC range based on the voltage platform characteristics of the lithium iron phosphate battery, initiating boost collaborative discharge only in the platform region and dynamically adjusting the injection current; and implementing graded power reduction or emergency shutdown protection when the temperature exceeds a threshold. This invention achieves ultra-wide voltage adaptability, low static power consumption, high-efficiency charging and discharging, and intelligent collaborative control, and can be installed non-destructively in various new energy commercial vehicles, effectively revitalizing existing assets with battery degradation.

Description

Technical Field

[0001] This invention relates to the field of electric vehicle battery capacity expansion technology, and in particular to an ultra-wide voltage adaptable bidirectional power supply module and control method for electric vehicles. Background Technology

[0002] In the field of new energy commercial vehicles (such as freight and taxi vehicles that operate frequently), the irreversible degradation of power batteries as they age is a common pain point. The vehicle's range drops sharply from the nominal 300 kilometers to just over 100 kilometers, resulting in a significant depreciation of assets, high insurance costs, and low rental rates, creating a "negative asset" dilemma.

[0003] In existing technologies, a common solution to extend driving range is to directly replace the original vehicle's large battery pack. However, this is costly (tens of thousands to hundreds of thousands of yuan) and involves disassembling the high-voltage system, which can easily violate the original manufacturer's high-voltage safety protocols and warranty terms. Another approach is to simply connect an additional battery in parallel, but this has the following technical drawbacks:

[0004] Voltage platform incompatibility: Different vehicle models (400V / 800V / 1000V) have different high voltage platform standards, and additional batteries need to be customized and packaged, which cannot be used interchangeably, resulting in high R&D and inventory costs.

[0005] The charging and discharging control is crude: lacking intelligent coordination with the original vehicle's charging protocol and battery management system (BMS), it is prone to risks such as the charging pile not being recognized, internal circulation with the original vehicle's battery during discharge, or damage to the original vehicle's battery due to over-discharge.

[0006] Low power transmission efficiency: When a low-voltage auxiliary battery (such as 48V / 64V) is boosted to a high-voltage platform, the traditional silicon device has a large on-state voltage drop (0.7V), resulting in a loss of more than 100 watts under high current (>200A), and serious heat dissipation problems.

[0007] Excessive static power consumption: The standby current of the added module causes the small battery to deplete after the vehicle has been parked for several weeks, making it unable to start.

[0008] Therefore, there is an urgent need for a bidirectional power module and control method that can be installed without damage, has an ultra-wide voltage range, high efficiency, and intelligent collaborative control, in order to achieve low-cost and high-safety capacity expansion of existing commercial vehicle battery systems. Summary of the Invention

[0009] The purpose of this invention is to provide an ultra-wide voltage adaptable bidirectional power module and control method for electric vehicles, enabling low-cost and high-safety capacity expansion of existing commercial vehicle battery systems.

[0010] To achieve the above objectives, in a first aspect, the present invention provides a bidirectional power supply control method for electric vehicles with ultra-wide voltage adaptability, comprising the following steps:

[0011] When the vehicle is turned off and not connected to a charging station, the digital control unit enters a deep sleep mode, retaining only the optocoupler-isolated key ignition signal detection branch with power; when a key ignition signal edge transition is detected, the digital control unit is awakened, performs multi-level self-tests and sequentially soft-starts the auxiliary power supply, and enters standby monitoring state;

[0012] The signal detection unit monitors the voltage value of the 12V auxiliary power supply pin in the charging pile interface. When the voltage jumps from low level to high level and remains stable for more than the preset de-jitter time, the charging start is confirmed, and the bidirectional power conversion unit is controlled to enter the buck charging mode to charge the additional small battery.

[0013] When the vehicle is not connected to a charging pile and is in motion, the total voltage of the original high-voltage battery pack is sampled in real time to determine the current state of charge range. When it is determined to be in the plateau range, the boost discharge mode is activated, and the low-voltage electricity of the auxiliary small battery is boosted to match the voltage of the original high-voltage battery pack and then injected in parallel. The injection current is dynamically adjusted according to the original vehicle load. When it is determined to be in the high charge range, discharge is prohibited. When it is determined to be in the low charge range, the injection current is linearly reduced until it is completely cut off.

[0014] The system monitors the values ​​of key temperature points in the bidirectional power conversion unit in real time. When any temperature point reaches the preset derating threshold, it performs graded power reduction protection. When any temperature point reaches the preset shutdown threshold, it performs an emergency shutdown and enters a fault lockout state.

[0015] The multi-level self-testing and step-by-step soft-start auxiliary power supply includes:

[0016] The first stage involves the digital control unit self-testing the core and clock; the second stage involves a soft-start low-dropout linear regulator powering the analog front-end circuit; the third stage involves a self-test of each differential amplifier sampling channel; and the fourth stage involves a soft-start isolated DC-DC converter powering the silicon carbide MOSFET drive circuit. If any stage of self-test fails, the system enters fail-safe mode.

[0017] The specific process for confirming the start of charging is as follows:

[0018] A high threshold and a low threshold are set by a hysteresis comparator, and a de-jitter delay filter is used. Charging is only confirmed when the voltage of the 12V auxiliary power supply pin exceeds the high threshold and remains stable for more than 200 milliseconds.

[0019] Specifically, charging is confirmed to be complete when the voltage drops below the low threshold and remains below it for more than 200 milliseconds.

[0020] The buck charging modes include:

[0021] First, a pre-charge check is performed to confirm that the auxiliary small battery is connected normally, the charging pile input voltage is normal, and the temperature conditions are permissible. Then, the constant current charging stage is entered, and the charging current follows the set value through current closed-loop control. When the voltage of the auxiliary small battery rises to the constant voltage transition voltage, the constant voltage charging stage is switched to maintain the voltage constant until the charging current decays to the cutoff current. Finally, charging is terminated and standby monitoring is entered.

[0022] The interval for determining the current state of charge includes:

[0023] The system retrieves a pre-stored voltage-state-of-charge (SOC) range mapping table and calculates the average voltage of each cell based on the total number of series-connected cells in the original vehicle's high-voltage battery pack. When the average voltage of a cell is higher than a first threshold, it is determined to be in a high-charge zone, corresponding to a SOC higher than 80%. When the average voltage of a cell is between the first and second thresholds, it is determined to be in a plateau zone, corresponding to a SOC between 20% and 80%. When the average voltage of a cell is lower than the second threshold, it is determined to be in a low-charge zone, corresponding to a SOC lower than 20%. The system also features dynamic calibration and temperature compensation functions.

[0024] Among them, dynamically adjusting the injected current according to the original vehicle load includes:

[0025] The load condition is determined based on the voltage change rate of the original vehicle's high-voltage bus. The injected current is increased during rapid acceleration or climbing, and the injected current is maintained or decreased during constant speed or coasting. Furthermore, the rise and fall of the injected current are achieved by using a ramp function to smoothly cut in and out, avoiding sudden changes in current.

[0026] The graded power reduction protection includes: when the temperature reaches the derating threshold, progressive measures are taken in sequence to reduce the output current, reduce the PWM switching frequency, and reduce the number of interleaved parallel working phases, until the temperature drops below the derating threshold by a hysteresis amount and stabilizes, and then the power is gradually restored.

[0027] Emergency shutdown includes: immediately blocking the PWM drive signals of all silicon carbide MOSFETs through hardware-level interrupt, cutting off the drive bias of the ideal diode, disconnecting the input contactor in charging mode, recording fault information and illuminating the red fault indicator light. To exit the fault lockout state, manual power-off and restart are required and the temperature must be reduced to a safe range.

[0028] The method further includes:

[0029] When the discharge current or charging current exceeds the rated maximum continuous current but is lower than the hardware peak current, the current is limited to the rated value by reducing the PWM duty cycle; when the current exceeds the hardware peak current, the hardware comparator triggers cycle-by-cycle current limiting or directly blocks all silicon carbide MOSFETs.

[0030] The method further includes:

[0031] The voltage of the additional small battery is monitored in real time. When the voltage is lower than the over-discharge protection point, any discharge behavior is prohibited, and only charging is allowed.

[0032] When a failure of the temperature or current sensor is detected, the output power will be limited to the minimum safe level and a fault will be reported.

[0033] Secondly, the present invention provides an ultra-wide voltage adaptable bidirectional power supply module for electric vehicles, applied to an ultra-wide voltage adaptable bidirectional power supply control method for electric vehicles as provided in the first aspect, comprising:

[0034] The bidirectional power conversion unit adopts a four-phase interleaved parallel topology. The main power switching device is a silicon carbide MOSFET, and an ideal diode composed of silicon carbide Schottky diodes is connected in series at the output end of each bridge arm. The low-voltage side of the unit is connected to an additional small battery, and the high-voltage side is connected in parallel to the original vehicle high-voltage battery pack through a T-connector. By replacing silicon carbide devices with different voltage ratings, the input and output voltage range covers 39V to 1000V.

[0035] The signal detection unit includes multiple differential amplifier sampling circuits, a 12V auxiliary power supply signal detection circuit, and an optocoupler-isolated key ignition signal detection circuit. The differential amplifiers are used to collect the voltage of the original vehicle's high-voltage battery pack, the voltage of the auxiliary small battery, the current of each phase, and the temperature. The 12V auxiliary power supply signal detection circuit is connected to the 12V auxiliary power supply pin in the charging pile interface. The optocoupler-isolated key ignition signal detection circuit is connected to the 12VACC signal line of the original vehicle's key ignition switch.

[0036] The digital control unit receives the digital signal from the signal detection unit and executes the ultra-wide voltage adaptation bidirectional power control method for electric vehicles as described in the first aspect, generating a PWM drive signal to control the switching state of the silicon carbide MOSFET and the conduction and turn-off of the ideal diode.

[0037] This invention discloses an ultra-wide voltage adaptable bidirectional power supply module and control method for electric vehicles, providing a non-destructive installation solution without disrupting the original manufacturer's protocol. The module employs a four-phase interleaved parallel topology and silicon carbide devices to achieve wide voltage range (39V-1000V) adaptability. The control method includes: wake-up via optocoupler-isolated key ignition signal edge and multi-level self-testing and soft-start, reducing standby power consumption to the microampere level; identification of charging status without protocol by detecting the 12V auxiliary power supply pin voltage of the charging pile, and execution of step-down charging; autonomous determination of the SOC range based on the voltage platform characteristics of lithium iron phosphate batteries, initiating boost-coordinated discharge only in the platform range and dynamically adjusting the injection current; and implementation of graded power reduction or emergency shutdown protection when the temperature exceeds a threshold. This invention achieves ultra-wide voltage adaptability, low static power consumption, high-efficiency charging and discharging, and intelligent coordinated control, and can be non-destructively installed in various new energy commercial vehicles, effectively revitalizing existing assets with battery degradation. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below.

[0039] Figure 1 This is a schematic diagram of the steps of a bidirectional power supply control method for an electric vehicle with ultra-wide voltage adaptability according to the first embodiment of the present invention.

[0040] Figure 2 This is a flowchart illustrating a bidirectional power supply control method for electric vehicles with ultra-wide voltage adaptability provided by the present invention.

[0041] Figure 3 This is a schematic diagram of the structure of an ultra-wide voltage-adaptive bidirectional power supply module for electric vehicles according to the second embodiment of the present invention. Detailed Implementation

[0042] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0043] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0044] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0045] The first embodiment of this application is as follows:

[0046] Please see Figures 1-3 This invention provides a bidirectional power supply control method for electric vehicles with ultra-wide voltage adaptability, comprising the following steps:

[0047] S1. When the vehicle is turned off and not connected to a charging station, the digital control unit enters a deep sleep mode, retaining only the optocoupler-isolated key ignition signal detection branch with power. When a transition of the key ignition signal edge is detected, the digital control unit is awakened, performs multi-level self-tests, and soft-starts the auxiliary power supply step by step, entering the standby monitoring state.

[0048] Specifically, when the vehicle is turned off (key removed or in the LOCK position) and not connected to any charging station (i.e., the 12V auxiliary power pin voltage of the charging port is zero), the digital control unit (DSP) executes a sleep command, entering a deep sleep mode. In this mode:

[0049] Inside the digital control unit: the master clock stops oscillating, and only a very low-power wake-up interrupt controller and an ultra-low leakage static random access memory (SRAM) are maintained to hold critical configuration registers. Core power is cut off, and all unused peripheral clocks are turned off.

[0050] External circuit power failure: The silicon carbide MOSFET drive circuit, differential amplifier sampling circuit, PWM signal generation circuit, etc. in the bidirectional power conversion unit are all powered off by the digital control unit through a controllable load switch array (composed of low-voltage MOSFETs). The input terminals of these circuits are all pulled to ground potential to ensure no floating leakage.

[0051] The only retained circuit: a single optocoupler-isolated key ignition signal detection branch is in a energized standby state. This branch consists of a high-resistance pull-down resistor (e.g., 10MΩ) and an LED on the input side of the optocoupler connected in series, and is connected to the original car key ignition switch's 12V ACC signal line. The entire branch has a quiescent current of approximately 10 microamps when there is no signal.

[0052] With the above settings, the total static power consumption of the entire bidirectional power module in the parked state is strictly controlled at the microampere level. The actual monthly power consumption is less than a few milliamp-hours. Even if the vehicle is parked for 2 to 3 months, the voltage drop of the additional small battery (48V / 20Ah or higher) will not exceed 2%, completely eliminating the phenomenon of starting due to power depletion.

[0053] When the user inserts the key and turns it to the ACC or ON position, the original vehicle's 12V ignition signal wire jumps from 0V to approximately 12V. This signal directly affects the optocoupler isolation detection branch:

[0054] Optocoupler input side: 12V voltage drives the internal LED of the optocoupler through the current limiting resistor, and the LED conducts and emits light.

[0055] Optocoupler output side: After the phototransistor inside the optocoupler receives the light signal, it turns on. The potential of its collector (connected to the wake-up interrupt pin of the digital control unit) is pulled down from the original pull-up high level (e.g., 3.3V) to the ground potential, generating a falling edge interrupt.

[0056] Electrical isolation advantages: Due to the use of optocoupler isolation, there is no direct electrical connection between the original vehicle's 12V ignition system and the low-voltage 3.3V system of the digital control unit. Even if the original vehicle's alternator generates transient surge voltages of up to hundreds of volts, they cannot be conducted to the digital control unit through the optocoupler, thus protecting the module's core controller. At the same time, the optocoupler also blocks possible fault current from flowing back into the original vehicle's ignition system, achieving bidirectional safety.

[0057] Upon detecting the falling edge, the wake-up interrupt controller of the digital control unit immediately triggers the wake-up startup process. It is important to note that this module only responds to rising or falling edge changes, and is not at a very low level. This means that even if the ignition signal remains at 12V for an extended period, the wake-up logic will not be repeatedly triggered. Similarly, if the ignition signal jitters due to poor contact, only the first valid edge will trigger the wake-up; subsequent jitter is ignored by the de-jitter filtering algorithm within the digital control unit, preventing repeated restarts.

[0058] Once awakened, the digital control unit does not immediately enable the main power conversion. Instead, it performs a four-level sequential self-test and step-by-step power-on process, which takes about 50 milliseconds in total, ensuring that all peripheral circuits start up stably under safe voltage.

[0059] Level 1: Kernel and clock self-test (takes approximately 5 milliseconds)

[0060] The digital control unit resumes core power from hibernation and starts the internal high-speed oscillator (e.g., a 16MHz RC oscillator). This oscillator does not require an external crystal, avoiding startup failure due to vibration damage.

[0061] The built-in power-on self-test program is executed, including: cyclic redundancy check (CRC) of the program memory (Flash) to ensure that the firmware has not been tampered with or damaged; and read / write tests of critical registers (such as watchdog timer and interrupt vector table).

[0062] If the self-test fails, the digital control unit will enter fail-safe mode: a red fault indicator light will illuminate (via the reserved LED driver pin), and all subsequent power-on steps will be blocked, leaving the module silent. If the self-test passes, it will proceed to the second stage.

[0063] Second stage: Low-voltage auxiliary power supply soft start (takes approximately 10 milliseconds)

[0064] The digital control unit slowly drives the enable pin of an external low-dropout linear regulator (LDO) via a general purpose input / output pin (GPIO), gradually ramping its output voltage from 0V to a stable 5V / 3.3V (e.g., at a 1% duty cycle per millisecond). This LDO is specifically designed to power analog front-end circuitry such as differential amplifiers, optocoupler outputs, and temperature sensors.

[0065] The advantages of soft start: It avoids the surge current generated by the charging of the output capacitor when the LDO is turned on instantly, preventing damage to the small battery. It also prevents the LDO from entering hiccup protection due to overcurrent.

[0066] After the LDO output voltage reaches a stable value, the digital control unit samples the feedback value of this voltage through its internal analog-to-digital converter (ADC) pin to confirm that the power supply is normal (within ±5% error). If the voltage is abnormal (e.g., a short circuit causing the voltage to drop), the LDO is immediately shut down and a fault is reported.

[0067] Level 3: Critical signal chain self-check (takes approximately 15 milliseconds)

[0068] The digital control unit sequentially enables the sampling circuits of each differential amplifier in the signal detection unit, including: the original high-voltage battery voltage sampling channel, the additional small battery voltage sampling channel, the current sampling channels of each phase of the bidirectional power conversion unit (using Hall effect current sensors or shunt resistors plus differential amplifiers), and the temperature sampling channels of each key node (silicon carbide MOSFET heat dissipation substrate, four-phase inductor core).

[0069] For each channel, the digital control unit injects an internally known reference voltage (e.g., a 1.25V reference generated by resistor division), then reads the ADC conversion result and compares it with the theoretical value. If the deviation exceeds the allowable range (e.g., ±2%), the channel is considered faulty, a fault code is recorded, and the startup is aborted.

[0070] This step ensures that the power, current, and temperature data upon which all subsequent control decisions are based are accurate and reliable, preventing damage from incorrect charging, over-discharging, or overheating due to sensor failure.

[0071] Level 4: Power stage auxiliary power supply and drive circuit power on (takes approximately 20 milliseconds)

[0072] The digital control unit enables the isolated DC-DC converters one by one via another set of GPIOs. This converter converts the low-voltage power supply (48V / 64V, etc.) from the small battery to the +15V / -3V gate drive voltage required by the silicon carbide MOSFETs, as well as the power supply for the current sampling isolation amplifier in the four-phase inductor.

[0073] Each isolated DC-DC converter is also enabled with a ramp soft start: the digital control unit increases the PWM duty cycle in 2% increments per millisecond, driving the transformer inside the converter to slowly increase its output voltage. This avoids a large inrush current to the small battery when multiple converters start simultaneously.

[0074] After all converter output voltages stabilize, the digital control unit controls the auxiliary drive circuit of the ideal diode (silicon carbide Schottky diode) to enter standby mode, but the PWM output of the main power circuit is still not enabled at this time.

[0075] After completing the above four-level self-test and step-by-step power-on, the digital control unit illuminates a green standby indicator light (via LED) and outputs a high level through a dedicated status pin, indicating that "the module is ready and awaiting operating instructions." At this time, the module is in standby monitoring mode.

[0076] All sensors (voltage, current, temperature) are functioning normally, and real-time sampled data is being sent to the digital control unit.

[0077] The main power circuit (silicon carbide MOSFET) of the bidirectional power conversion unit is still in a blocked state (all drive signals are low level, that is, all switching transistors are turned off), so no energy flows from the auxiliary small battery to the original vehicle high voltage bus, nor from the charging pile to the auxiliary small battery.

[0078] The digital control unit continuously monitors two wake-up sources: one is the key ignition signal that has already taken effect (i.e., the signal is still at a high level, indicating that the vehicle is powered on); the other is the voltage change of the 12V auxiliary power pin of the charging interface (used for charging identification in the subsequent step 2).

[0079] S2. Monitor the voltage value of the 12V auxiliary power supply pin in the charging pile interface through the signal detection unit. When the voltage jumps from low level to high level and remains stable for more than the preset de-jitter time, confirm the start of charging and control the bidirectional power conversion unit to enter the buck charging mode to charge the additional small battery.

[0080] Specifically, both standard DC fast charging stations (9-pin interface) and AC slow charging stations (7-pin interface) include a pair of 12V auxiliary power pins (usually labeled A+ and A-, or 12V). + and 12V - The characteristics of this pin are as follows:

[0081] Physical presence: All public charging stations that comply with national or European standards must provide this pin to provide wake-up power to the vehicle charging controller (such as BMS motherboard, display screen, etc.).

[0082] Logic timing: When the user does not perform any operation, the voltage of this pin is 0V. Only when the user completes the payment by swiping the card, scanning the code, or activating the charging button, and the internal control relay of the charging pile is closed, is a 12V voltage applied to this pin (the actual range is between 10V and 14V).

[0083] Continuous power supply: Once charging begins, the 12V auxiliary power supply will continue to output until the user manually stops charging or the charging station determines that the main circuit power is cut off. After charging is completed, the voltage on this pin returns to 0V.

[0084] The signal detection unit includes a dedicated 12V auxiliary power supply signal detection circuit. This circuit consists of the following parts:

[0085] Resistor voltage divider network: Divides the 12V auxiliary power supply pin voltage of the charging pile interface to the acceptable 0-3.3V range of the digital control unit (DSP) analog-to-digital converter (ADC). The voltage division ratio is precisely designed to ensure that even if the pin voltage fluctuates to 14V, the divided voltage will not exceed 3.3V.

[0086] Low-pass filter circuit: An RC low-pass filter (time constant of about 5 milliseconds) is connected in series after the voltage divider resistor to filter out spikes or high-frequency interference that may be generated when the charging pile relay is engaged.

[0087] Comparator: To enhance anti-interference capability, the signal can pass through a hysteresis comparator (Schmitt trigger) before being sent to the ADC, with two thresholds: a high threshold (e.g., 8V) and a low threshold (e.g., 4V). The output is only determined to be logic "1" when the input voltage exceeds the high threshold; the output returns to logic "0" when the voltage drops below the low threshold. This hysteresis characteristic avoids repeated misjudgments caused by voltage jitter near the critical point.

[0088] The digital control unit periodically (e.g., sampling once every 50 milliseconds) reads the conversion result of the ADC channel, converts it into the actual voltage value, and determines the charging status based on the following logic:

[0089] Non-charging state (idle): When the voltage is detected to be below 4V (equivalent to 0V, allowing for slight noise), the digital control unit considers the charging station to be inactive. At this time, the module maintains a deep sleep or standby monitoring state and does not perform any charging-related operations.

[0090] Charging activation state (start): When a voltage jump from below 4V to above 8V is detected, and this high voltage state is maintained stably for more than 200 milliseconds (debouncing delay), the digital control unit confirms that "charging has been legally started". At this time, the digital control unit generates an internal flag "charging mode enabled" and triggers the charging process.

[0091] Charging Completed (Stopped): If, during charging, the digital control unit detects that the 12V auxiliary power supply pin voltage drops from above 8V to below 4V, and this low voltage state persists for more than 200 milliseconds, then charging is considered complete. The digital control unit immediately clears the "Charging Mode Enable" flag and executes the charging termination procedure.

[0092] Once the digital control unit confirms "charging mode enabled," this module will control the bidirectional power conversion unit to enter buck charging mode. The goal of this mode is to efficiently and safely step down the high-voltage DC power output from the charging station (400V, 800V, or 1000V, depending on the vehicle platform) to the rated voltage of the auxiliary small battery (e.g., 48V, 64V, or 90V), and replenish the auxiliary small battery according to a preset charging curve. The entire process is independent of the original vehicle's high-voltage battery pack charging process; both are connected in parallel to the same charging station but do not interfere with each other.

[0093] The four-phase interleaved parallel topology in the bidirectional power converter operates in reverse buck mode during charging. Specifically:

[0094] The original vehicle's high-voltage DC bus (connecting the charging pile and the original vehicle battery) is used as the input terminal and connected to the high-voltage side of the conversion unit.

[0095] An additional small battery is connected to the low-voltage side of the conversion unit.

[0096] The digital control unit generates four sets of PWM drive signals with a phase difference of 90 degrees, which control the silicon carbide MOSFET to operate in a high-frequency switching mode. The high-voltage DC is chopped into high-frequency pulses, which are then stored and filtered by four inductors to output a stable low-voltage DC to charge the additional small battery.

[0097] In this mode, the ideal diode (silicon carbide Schottky diode) is always in reverse bias. Its built-in low on-state voltage drop ensures unidirectional current flow and prevents the additional small battery current from flowing back to the charging pile or the original vehicle high-voltage bus.

[0098] The entire charging process is executed in four stages: pre-charge check, constant current charging, constant voltage charging, and termination and shutdown. Each stage is subject to strict safety monitoring and protection.

[0099] Phase 1: Pre-charge check (takes approximately 100 milliseconds)

[0100] Before officially initiating power transmission, the digital control unit performs the following checks:

[0101] Additional small battery connection verification: The voltage of the additional small battery is sampled using a differential amplifier. If the voltage is lower than the minimum allowable charging voltage (e.g., 36V for a 48V battery system), the battery pack is considered to be severely over-discharged or disconnected. In this case, charging is prohibited and a fault is reported.

[0102] Charging pile input voltage confirmation: Sample the high-voltage side voltage and confirm that its value is within the allowable range (e.g., 350V-450V corresponds to a 400V platform, 700V-850V corresponds to an 800V platform). If the voltage is abnormal (e.g., below 200V), it is considered that the charging pile is not outputting normally, and a retry is required.

[0103] Temperature condition check: Read the values ​​of each temperature sensor to confirm that the temperature of the silicon carbide MOSFET and four-phase inductor is within the allowable charging window (e.g., -20℃ to +55℃). If it is outside the range, delay the start-up or adjust the charging current.

[0104] Original vehicle battery status monitoring: This module monitors but does not intervene. The digital control unit samples the original vehicle's high-voltage battery voltage to confirm normal charging (the voltage shows a slow upward trend). If an abnormality is detected in the original vehicle's battery voltage (such as remaining stationary or decreasing), this module will not initiate charging to avoid safety issues caused by charging malfunctions in the original vehicle.

[0105] Once all checks are passed, the digital control unit issues a "charging permission" command, initiating the constant current charging phase.

[0106] Phase Two: Constant Current Charging

[0107] Current setting: The digital control unit sets a safe constant current charging current value based on the preset specifications of the auxiliary battery (which can be determined via an external DIP switch or self-learning upon initial connection). For example, for an auxiliary battery with a capacity of 50Ah, a 0.5C rate is used, which is 25A.

[0108] Current closed-loop control: The digital control unit reads the value of the low-voltage side current sampling channel in real time and compares it with the set value. By adjusting the PWM duty cycle and switching frequency of the four-phase interleaved parallel topology, the actual charging current closely follows the set value. Due to the use of the four-phase interleaved structure, the output current ripple is extremely small (less than 5% of the set value), which helps to extend the life of the auxiliary small battery.

[0109] Voltage limit monitoring: During constant current charging, the digital control unit simultaneously monitors the terminal voltage of the additional small battery. When the voltage rises to the constant voltage transition voltage (for example, for a 48V lithium iron phosphate battery, it is approximately 57.6V, i.e., 3.6V per cell × 16 cells), the digital control unit records the current capacity and automatically switches to the constant voltage charging stage.

[0110] Phase 3: Constant Voltage Charging

[0111] Voltage setting: The digital control unit sets the output voltage to the full charge voltage of the auxiliary small battery (i.e., constant voltage transition voltage, which will not increase further). At this time, the control objective of the digital control unit switches from constant current to constant voltage: by sampling the low-voltage side voltage, the PWM output is adjusted to stabilize the voltage at the set value.

[0112] Natural current decay: As the SOC of the additional small battery gradually approaches 100%, its internal polarization electromotive force increases, and the charging current will naturally decrease. The digital control unit continuously monitors the charging current.

[0113] Termination condition determination: When the charging current decays to the preset cutoff current (e.g., 10% of the constant current value, i.e., 2.5A) and remains stable for more than 30 seconds, the digital control unit determines that the auxiliary small battery is fully charged. If the auxiliary small battery uses a lithium iron phosphate system, a "voltage inflection point detection" can also be added as an auxiliary criterion: when the voltage no longer rises and the current continues to drop to a very low level, it is considered fully charged.

[0114] Phase 4: Charging terminated and module shut down

[0115] Power output cut-off: The digital control unit immediately blocks the PWM drive signals of all silicon carbide MOSFETs, causing the bidirectional power conversion unit to completely stop energy transmission.

[0116] Status recording and reporting: The starting SOC, ending SOC, maximum temperature, charging time and other information of this charge are stored in the non-volatile memory inside the digital control unit for subsequent maintenance or fault analysis.

[0117] Entering Standby Monitoring: After the module stops charging, it does not immediately enter deep sleep mode, but remains in standby monitoring mode, continuing to monitor the 12V auxiliary power supply pin voltage. This is because the charging station may still be charging the original vehicle battery (which has a larger capacity and may take longer). If the 12V auxiliary power supply pin voltage remains high (indicating that the charging station is still active), the module remains silent but does not enter sleep mode; once it detects that the pin voltage changes from high to low (the user stops charging or the charging station is turned off), the digital control unit will execute the deep sleep process described in step 1 to save power.

[0118] Throughout the charging process, the digital control unit monitors the following key parameters in real time at millisecond intervals, and takes appropriate protective measures immediately if any abnormality is triggered:

[0119] Over-temperature protection: If the junction temperature of the silicon carbide MOSFET or the temperature of the four-phase inductor exceeds the preset warning value (e.g., 85°C), the digital control unit automatically reduces the charging current to 50% or lower of the rated value. If the temperature continues to rise to 105°C, charging will be terminated immediately and a fault will be reported.

[0120] Overvoltage protection: If the high-voltage side input voltage (from the charging pile) unexpectedly spikes above the module's tolerance limit (e.g., 1100V), the digital control unit immediately blocks the PWM and simultaneously closes a varistor or transient voltage suppressor (TVS) connected in parallel to the input terminal for clamping.

[0121] Undervoltage protection: If the voltage of the additional small battery drops abnormally during charging (which may indicate an internal short circuit in the battery), charging will stop immediately.

[0122] Communication timeout protection: Although this module does not rely on CAN communication, the digital control unit monitors the status changes of the 12V auxiliary power supply pin. If, during constant current or constant voltage charging, the voltage of this pin suddenly drops to 0V and remains there for more than 1 second, it indicates that the charging station has been manually stopped or has malfunctioned. The digital control unit will immediately terminate charging and safely shut down.

[0123] S3. When the vehicle is not connected to a charging pile and is in motion, the total voltage of the original vehicle's high-voltage battery pack is sampled in real time to determine the current state of charge range. When it is determined to be in the plateau range, the boost discharge mode is activated to boost the low voltage of the auxiliary small battery to match the voltage of the original vehicle's high-voltage battery pack and then inject it in parallel. The injection current is dynamically adjusted according to the original vehicle load. When it is determined to be in the high charge range, discharge is prohibited. When it is determined to be in the low charge range, the injection current is linearly reduced until it is completely cut off.

[0124] Specifically, the discharge curve of a lithium iron phosphate (LFP) cell has the following significant characteristics:

[0125] Plateau region: Within a wide SOC range of approximately 20% to 80%, the individual cell voltage changes very smoothly, stabilizing between approximately 3.20V and 3.30V (nominal plateau voltage approximately 3.25V). Within this range, the voltage variation is minimal (only about 0.1V), while the SOC variation reaches 60%.

[0126] High-voltage inflection point region: When the SOC is higher than 80%, charging enters the constant voltage stage, and the voltage will rise rapidly to above 3.40V, reaching a maximum of 3.65V (fully charged). At this time, the voltage is sensitive to the SOC, and the slope is steep.

[0127] Low-voltage inflection point region: When the state of charge (SOC) is below 20%, the discharge enters its final stage, and the voltage drops rapidly from 3.20V to 2.80V or even lower (cutoff voltage). At this time, the voltage is also sensitive to the SOC, and the slope is steep.

[0128] Based on this characteristic of being "flat in the middle and steep at both ends," this invention uses voltage as a reliable indicator for determining the SOC range. Although there is no strict linear relationship between voltage and SOC within the plateau region, this invention does not require precise SOC percentage values. It only needs to determine whether the battery is in one of three coarse-grained ranges: "high charge range (>80%)", "plateau operating range (20%-80%)", or "low charge range (<20%)". Minor voltage fluctuations are insufficient to cross the voltage thresholds between these three ranges, therefore this method is extremely robust.

[0129] The differential amplifier sampling circuit in the signal detection unit continuously collects the total voltage of the original vehicle's high-voltage battery pack. The specific implementation is as follows:

[0130] High-precision differential sampling: An isolated differential amplifier is used, with its input connected to the positive and negative terminals of the original vehicle's high-voltage battery pack via a high-resistance resistor voltage divider network. This amplifier has a high common-mode rejection ratio (>80dB), effectively suppressing common-mode noise generated by high-power loads such as the motor controller and air conditioning compressor. The amplified analog voltage signal is then fed into the analog-to-digital converter (ADC) channel of the digital control unit.

[0131] Digital filtering: The digital control unit performs a moving average filter on the original sampled values ​​(e.g., sampling once every 10 milliseconds and taking the average of the most recent 20 samples) to eliminate instantaneous spike interference. The filtered voltage value is used as the basis for interval determination.

[0132] Voltage-SOC Range Mapping Table: The digital control unit internally contains a voltage-range mapping table based on the characteristics of lithium iron phosphate batteries. This table is automatically calculated based on the total number of series-connected cells in the original vehicle's high-voltage battery pack (e.g., 96 or 108 series lithium iron phosphate batteries on a 400V platform, and 192 or 216 series on an 800V platform). The mapping relationship is as follows:

[0133] High charge threshold: When the average voltage of a single cell is > 3.40V, the SOC is considered > 80% (high voltage inflection point). For a 96-cell battery pack, this means the total voltage is > 326.4V.

[0134] Plateau zone determination threshold: When the average voltage of a single cell is between 3.20V and 3.40V, the SOC is considered to be between 20% and 80% (plateau zone).

[0135] Low charge threshold: When the average voltage of a single cell is < 3.20V, the state of charge (SOC) is considered to be < 20% (low voltage inflection point). To provide a safety margin, an even lower threshold (e.g., 3.00V for a single cell, corresponding to an SOC of approximately 10%) can be set as a protection point for forced discharge termination.

[0136] Since factors such as battery aging and temperature changes can affect voltage characteristics, the digital control unit also has dynamic calibration capabilities to improve the long-term accuracy of range determination.

[0137] Full charge self-calibration: When the module detects that the vehicle is connected to the charging pile and the original vehicle battery is fully charged (by observing that the voltage remains stable near the full charge voltage for several minutes and the 12V auxiliary power pin of the charging pile is de-energized), it records the full charge voltage value at this time and updates the high charge threshold reference point.

[0138] Low battery self-calibration: When the module detects that the original vehicle battery voltage drops to near the cutoff voltage (e.g., 2.80V per cell), and the vehicle experiences significant power limitation or the driver actively stops driving, it records the low voltage value at this time and updates the low battery threshold reference point.

[0139] Temperature compensation: Ambient temperature is obtained through a temperature sensor installed near the battery pack (or a temperature probe integrated into the module). When the temperature is below 0°C, the digital control unit automatically corrects the voltage threshold of the plateau region downwards (e.g., from 3.20V to 3.10V), because the plateau voltage of the lithium iron phosphate battery decreases slightly at low temperatures. Conversely, it is slightly adjusted upwards at high temperatures.

[0140] Based on the calculated SOC range, the digital control unit executes differentiated discharge control logic. The entire discharge process is divided into three stages: discharge exit / discharge prohibition (high charge area), adaptive cooperative discharge (platform area), and power reduction and protection exit (low charge area), and includes sub-processes such as smooth cut-in and cut-out, and dynamic current regulation.

[0141] 1. High charge zone (SOC > 80%): Do not discharge, keep it undisturbed.

[0142] When the digital control unit determines that the original vehicle battery is in a high-charge area through voltage sampling, the module performs the following operations:

[0143] Without boost discharge: All silicon carbide MOSFETs in the bidirectional power conversion unit remain off, and the PWM output is completely blocked. The additional small battery does not inject any current into the original vehicle's high-voltage bus.

[0144] Rationale: At this point, the original vehicle battery has sufficient charge and a relatively high voltage. Forcing parallel discharge would first waste the energy of the additional small battery (which could have been saved for lower charge levels). Second, the original battery has low internal resistance at high SOC, and the injected current from the additional small battery could cause unnecessary circulating current or trigger overvoltage protection in the original vehicle's BMS. Finally, in some models, when the original battery has a high charge, the motor's energy recovery function may be more aggressive, and externally injected current could interfere with its control strategy.

[0145] Continuous monitoring: The module remains in standby monitoring mode, continuously sampling the original vehicle battery voltage at millisecond intervals. Once a voltage drop is detected and the battery enters a plateau (e.g., due to power consumption from continuous vehicle operation), it immediately switches to cooperative discharge mode.

[0146] 2. Plateau region (SOC 20% - 80%): Adaptive cooperative discharge

[0147] This is the core operating range of this module. When the original vehicle battery voltage falls between the upper and lower thresholds of the platform zone, the digital control unit initiates the boost discharge mode and executes the following refined collaborative control strategy.

[0148] (1) The physical process of boost discharge

[0149] The digital control unit controls the bidirectional power conversion unit to operate in boost mode: the low-voltage DC power (e.g., 48V, 64V or 90V) from the additional small battery is boosted to the current real-time sampled original vehicle high-voltage battery voltage (a dynamically changing value that slowly decreases as discharge occurs) through a four-phase interleaved parallel topology and high-frequency switching of silicon carbide MOSFETs.

[0150] The boosted voltage is unidirectionally clamped by an ideal diode (silicon carbide Schottky diode) to ensure that the current can only flow from the additional small battery to the original vehicle high-voltage bus, and will not flow in the reverse direction.

[0151] Because the boost output voltage is precisely adjusted to be slightly higher than the original vehicle battery voltage (e.g., 0.5V to 1V higher, the specific value is automatically adjusted by the digital control unit according to the current demand), the power of the additional small battery can naturally flow into the original vehicle circuit and be connected in parallel with the original vehicle battery to power the drive motor.

[0152] (2) Dynamic current injection control

[0153] The digital control unit does not discharge at a fixed power, but dynamically adjusts the injected current based on the real-time status of the auxiliary small battery and the original vehicle load.

[0154] Basic injection current setting: First, set a maximum allowable discharge current based on the rated capacity of the additional small battery (e.g., 0.5C, or 25A for a 50Ah battery). The digital control unit defaults to using 70% of this current value as the initial injection current.

[0155] Current closed-loop regulation: By sampling the output current of the auxiliary small battery (low-voltage side current sensor), the digital control unit adjusts the PWM duty cycle to make the actual current follow the target value. Due to the use of a four-phase interleaved parallel topology, the ripple of the output current is extremely small, and the interference to the original vehicle electrical system is minimal.

[0156] Load Adaptive: The digital control unit simultaneously monitors the voltage change rate of the original vehicle's high-voltage bus. If the voltage drops rapidly (indicating high-load conditions such as rapid acceleration or climbing), the digital control unit will appropriately increase the injected current (up to 100% of the maximum allowable current) to provide more auxiliary power. Conversely, if the voltage is stable or slightly rising (such as when the vehicle is traveling at a constant speed or coasting slightly), the injected current will be maintained or slightly reduced. This dynamic response ensures that the energy from the auxiliary small battery is utilized when it is most needed.

[0157] (3) Avoid conflicts with the original vehicle BMS control strategy

[0158] No priority preemption: This module always operates as a "slave" power supply and will not actively boost the original vehicle bus voltage to an abnormal level. The boost output voltage is only less than 1V higher than the real-time sampled original vehicle voltage. Therefore, the original vehicle battery continues to discharge normally according to its own voltage characteristics, and the original vehicle BMS will not report errors or limit power due to detecting abnormal voltage.

[0159] Without interfering with energy recovery: When the driver releases the accelerator or applies the brake, the drive motor switches to generator mode, and the energy recovery current flows in reverse into the original vehicle battery. At this time, the original vehicle bus voltage will rise momentarily. The digital control unit will immediately detect this voltage rise and quickly reduce or even completely cut off the injection current of the auxiliary small battery (by reducing the PWM duty cycle or turning off the ideal diode) to avoid conflict between the energy of the auxiliary small battery and the recovered energy. After the voltage stabilizes, the decision to resume discharge is reassessed.

[0160] Smooth start and stop: During discharge initiation and termination, the digital control unit does not instantly jump the current from 0 to the target value. Instead, it uses a ramp function (e.g., linearly increasing the duty cycle over 2 seconds) to slowly increase the injected current. Similarly, a ramp-down is used when discharging stops. This avoids sudden current surges impacting the original vehicle's high-voltage circuit and also prevents surge stress on the additional small battery.

[0161] During the discharge process within the platform area, the digital control unit continuously monitors two key parameters:

[0162] Is the original vehicle battery voltage stable within the plateau range? If the voltage rises to the high charge threshold due to discharge or other reasons (such as energy recovery), discharge will be temporarily stopped; if the voltage drops to the low charge threshold, the power reduction phase will begin.

[0163] The additional small battery's own SOC (State of Charge). The digital control unit also estimates its remaining capacity by detecting the voltage of the additional small battery and the integral of its accumulated discharge capacity. When the additional small battery's SOC falls below a preset reserve value (e.g., 15%), the module will gradually reduce the injected current to prevent the additional small battery from being over-discharged.

[0164] 3. Low battery level (SOC < 20%): Reduce power and disable protection.

[0165] When the original vehicle battery voltage drops to the low charge threshold, the digital control unit performs the following actions to ensure that the original vehicle battery does not break down due to over-discharge:

[0166] Linear power reduction: As the original vehicle voltage drops further from the lower limit of the plateau region (e.g., 3.20V per cell) to the cutoff voltage (e.g., 3.00V per cell), the digital control unit linearly reduces the injection current of the auxiliary small battery from its current value to zero. For example, for every 0.05V drop in voltage, the injection current is reduced by 20%. This linear relationship avoids the feeling of power jerkiness caused by sudden cutoff.

[0167] Complete cut-off point: When the original vehicle voltage reaches the set minimum safe voltage (e.g., 2.90V for a single cell, close to the discharge cut-off voltage of the BMS), the digital control unit immediately blocks all PWM outputs and turns off the ideal diode, completely cutting off the discharge path of the auxiliary small battery.

[0168] Rationale: At this point, the original vehicle battery's charge is extremely low. The vehicle's dashboard will typically illuminate a low battery warning light and may limit motor power. Continuing to inject current, while temporarily maintaining operation, will cause the original battery voltage to drop further to the BMS's hardware protection point (e.g., 2.50V per cell). The BMS will then forcibly cut off the high-voltage output, causing the vehicle to completely lose power and break down—a situation that must be avoided. Therefore, this module exits when the original vehicle battery still has a remaining charge (approximately 10% SOC), reserving the remaining charge for the vehicle's safety redundancy strategy.

[0169] Recovery Conditions: After discharging is cut off, the module will not immediately attempt to resume. Discharging will only be reassessed if the original vehicle battery voltage is detected to have rebounded to the plateau zone (e.g., through energy recovery or voltage rebound after the vehicle stops) and the driver has not turned off the engine (the ignition signal is still valid).

[0170] Throughout the discharge process, the digital control unit monitors the following protection parameters in real time and takes action in case of abnormalities:

[0171] Overcurrent protection: If the sampled discharge current of the additional small battery exceeds the maximum value allowed by the hardware (e.g., 250A, corresponding to 10kW power), the digital control unit will block the PWM within microseconds to prevent damage to the silicon carbide MOSFET.

[0172] Over-temperature protection: Similar to the charging mode, when the temperature sensor detects that the temperature of the silicon carbide MOSFET or four-phase inductor exceeds 85°C, the discharge current is automatically reduced; when it exceeds 105°C, the discharge is completely stopped.

[0173] Additional small battery undervoltage protection: If the voltage of the additional small battery drops to the over-discharge protection point (e.g., 2.50V for a single cell), the discharge will stop immediately to prevent damage.

[0174] Original vehicle voltage abnormal fluctuation protection: If the original vehicle high voltage bus voltage fluctuates drastically (e.g., changes exceeding 50V within 1 millisecond), it may indicate that the original vehicle BMS has cut off the output or other faults have occurred. The module will immediately block the output and enter a fault state, waiting for manual reset.

[0175] The module uses a tri-color LED indicator to provide feedback on the current discharge status to the driver or maintenance personnel:

[0176] Solid green light: Module is normal and is discharging collaboratively.

[0177] Green flashing: The module is normal, but is currently in a high or low power zone and has not been discharged (standby).

[0178] Solid yellow light: Reduced power operation (e.g., derating due to overheating).

[0179] Red flashing: Fault (such as overcurrent, overtemperature shutdown, sensor malfunction, etc.).

[0180] S4. Monitor the values ​​of key temperature points in the bidirectional power conversion unit in real time. When any temperature point reaches the preset derating threshold, perform graded power reduction protection. When any temperature point reaches the preset shutdown threshold, perform emergency shutdown and enter fault lockout state.

[0181] Specifically, the temperature sensor in the signal detection unit is located in the following positions:

[0182] Silicon carbide MOSFET heat dissipation substrate: A negative temperature coefficient thermistor (NTC) is attached to the common source connection of each phase silicon carbide MOSFET to reflect the junction temperature change of the power switching device.

[0183] The magnetic core surface of the four-phase inductor: Each phase inductor has an NTC mounted on its outer surface to monitor the temperature rise caused by copper loss and iron loss.

[0184] Ideal diode heatsink: Silicon carbide Schottky diodes are mounted together on the same copper substrate, and their temperature is monitored by an NTC.

[0185] Ambient temperature reference: An NTC is installed inside the module housing near the air inlet to obtain the operating ambient temperature as an auxiliary reference for derating decisions.

[0186] All NTC analog signals are conditioned by differential amplifiers before being sent to the digital control unit. The digital control unit internally sets three threshold levels for each temperature monitoring point: a warning threshold, a derating threshold, and a shutdown threshold. Taking a silicon carbide MOSFET as an example:

[0187] Warning threshold: 80℃. Below this temperature, the module can operate at full power for extended periods.

[0188] Derating threshold (first threshold): 85℃. When the temperature of any silicon carbide MOSFET heat sink reaches 85℃, it enters the power derating protection mode.

[0189] Shutdown threshold (second threshold): 105℃. When any temperature reaches 105℃, emergency shutdown protection will be immediately executed.

[0190] For four-phase inductors and ideal diodes, the derating threshold and shutdown threshold are set to 95°C and 115°C, respectively (because their temperature resistance is higher than that of silicon carbide devices). Ambient temperature does not directly trigger protection, but the digital control unit automatically adjusts the offset of the derating threshold according to the ambient temperature (for example, when the ambient temperature exceeds 60°C, the derating threshold is reduced by 5°C).

[0191] When the digital control unit detects that the value of any critical temperature monitoring point reaches or exceeds its corresponding derating threshold (e.g., the silicon carbide MOSFET reaches 85°C), the module immediately enters a power reduction operation mode. This mode does not aim to shut down immediately, but rather to dynamically reduce the output power to stabilize the temperature within a safe range, while maintaining the vehicle's normal charging and discharging functions as much as possible.

[0192] The digital control unit selects one or more of the following power reduction measures based on the current operating status of the module (charging mode or discharging mode) and the specific location where the temperature exceeds the limit:

[0193] Reducing the PWM switching frequency: The original switching frequency of a four-phase interleaved parallel topology is designed to be a relatively high value (e.g., 100kHz) to obtain lower current ripple. When power reduction is required, the digital control unit gradually reduces the switching frequency to a lower value (e.g., 50kHz or 25kHz). Lowering the switching frequency reduces the switching losses of the silicon carbide MOSFETs (reducing the number of switches per cycle), thereby lowering the junction temperature. However, excessively low frequencies increase current ripple, so the reduction is limited and will not fall below the minimum safe operating frequency (e.g., 20kHz to avoid noise in the audible frequency range).

[0194] Reducing the output injection current or charging current: In discharge mode, the digital control unit lowers the target injection current setting. For example, it gradually reduces it from the maximum allowable current of 200A to 150A, 100A, or even lower. In charging mode, it lowers the charging current setting of the auxiliary small battery. This method of directly limiting output power is most effective for temperature control.

[0195] Reducing the number of interleaved parallel operating phases: The four-phase interleaved parallel topology supports single-phase, two-phase, or three-phase operation. When the temperature exceeds the limit and the current reduction effect is insufficient, the digital control unit can select to shut down the drive signals of one or two phases, allowing the module to operate with fewer phases. Reducing the number of operating phases will cause the remaining phases to bear greater current stress, but it will also reduce the total number of power devices and total losses, which helps to disperse heat sources. The digital control unit will rotate the shut-down phases to avoid uneven temperature caused by devices in a certain phase not working for a long time.

[0196] The digital control unit executes the commands in the following priority order: first reduce current, then reduce frequency, and finally reduce phase. The specific logic is as follows:

[0197] Phase 1 (Mild Overheating, 85℃-90℃): The digital control unit linearly reduces the output current or charging current to 80% of its rated value. Simultaneously, the PWM switching frequency is reduced to 75% of its original frequency (e.g., from 100kHz to 75kHz). During this phase, the module still provides most of its auxiliary functions.

[0198] Second stage (moderate overheating, 90℃-95℃): The digital control unit further reduces the output current to 50% of the rated value. The switching frequency is reduced to 50% of the original frequency. If currently operating in four-phase interleaved mode, one phase is shut down (reducing to three-phase operation).

[0199] The third stage (approaching the shutdown threshold, 95℃-105℃): The current is reduced to 20% of the rated value, the switching frequency is reduced to the minimum safe frequency (e.g., 25kHz), and the number of operating phases is reduced to two phases. At the same time, the digital control unit illuminates the yellow fault indicator light and sends a "power reduction warning" level through the reserved signal output port.

[0200] Throughout the power reduction process, the digital control unit continuously monitors temperature changes at millisecond intervals. If the temperature begins to drop and falls below the derating threshold (e.g., from 88°C to 84°C), the module does not immediately restore full power. Instead, it employs a hysteresis recovery mechanism: power is gradually restored to normal only after the temperature drops to the derating threshold minus a hysteresis amount (e.g., minus 5°C, i.e., 80°C) and remains stable for more than 10 seconds. This hysteresis design avoids frequent power jumps caused by repeated temperature fluctuations at the threshold boundary.

[0201] In addition to electrical derating, the digital control unit can also trigger the following auxiliary cooling measures (if the module hardware is configured with the appropriate components):

[0202] Increase cooling fan speed: If the module has a built-in or external cooling fan, the digital control unit outputs a PWM signal with a higher duty cycle to drive the fan to run at full speed, forcibly increasing airflow.

[0203] Reduce the charging and discharging requests of the auxiliary small battery: In discharge mode, the digital control unit indirectly reduces the discharge rate of the auxiliary small battery by limiting the injected current, thereby reducing the battery's own heat generation.

[0204] When the digital control unit detects that the value of any critical temperature monitoring point reaches or exceeds the shutdown threshold (e.g., 105°C for a silicon carbide MOSFET, 115°C for a four-phase inductor, or 115°C for an ideal diode heatsink), it determines that the module is in a dangerous overheating state and must immediately stop all power transmission. At this time, the emergency shutdown protection procedure is executed. This procedure has the highest priority and cannot be interrupted by any other task.

[0205] Immediately block the PWM drive signal: The digital control unit, through a hardware-level interrupt service routine, forcibly pulls the drive signals of all silicon carbide MOSFETs low within microseconds (regardless of the current state of the PWM generation logic). This ensures that all power switches quickly enter a fully off state, cutting off energy flow.

[0206] Auxiliary drive cut-off of ideal diode: At the same time, the digital control unit shuts off the bias power supply in the ideal diode drive circuit, so that the silicon carbide Schottky diode can restore its intrinsic unidirectional conduction characteristics and prevent any reverse current.

[0207] Disconnecting charging input or discharging output: If the module is in charging mode, an emergency stop will also trigger a control signal of a DC contactor (relay) connected in series at the high-voltage input terminal, causing the contactor to disconnect and electrically isolate the module from the charging pile. In discharging mode, since the module is directly connected in parallel to the original vehicle's high-voltage bus, it cannot be physically disconnected (to avoid affecting the original vehicle's power supply), but blocking the PWM and the ideal diode is sufficient to prevent the current output of the additional small battery.

[0208] Fault Lockout: After an emergency shutdown, the digital control unit enters a fault lockout state. In this state, all PWM outputs remain locked, and the digital control unit does not attempt any automatic recovery. Fault information (including which temperature point triggered the shutdown, the temperature value at the time of shutdown, timestamp, etc.) is written to the internal non-volatile memory.

[0209] Red fault indicator light: The LED indicator light on the module panel turns red and stays on or flashes rapidly (at a specific flashing frequency, such as 5 times per second), clearly indicating to the operator that an over-temperature fault has occurred.

[0210] Fault signal output: The digital control unit outputs a low-level or closed signal through a dedicated fault output pin (open collector or relay contact) for the vehicle controller (if connected) or external monitoring equipment to read.

[0211] The fault lockout state will not be cleared automatically. The digital control unit will only exit the fault lockout and attempt a restart after all of the following conditions are met:

[0212] Manual power-off restart: The module's auxiliary power supply (the power cable connected to the additional small battery) must be completely disconnected for at least 10 seconds, and then power restored. During the power-on self-test, the digital control unit checks the fault flags in the non-volatile memory. If a fault flag is detected, it first verifies that all current temperature points have dropped to a safe range (e.g., below 70°C). The fault flags will only be cleared after the temperature is safe and a manual restart is performed.

[0213] Alternatively, a fault clearing command can be sent via a dedicated programming interface (such as CAN or serial port) (operation is limited to professional maintenance personnel only).

[0214] In addition to temperature protection, this module also integrates protection logic for anomalies such as overcurrent, overvoltage, undervoltage, and short circuit. These protections also trigger graded responses or emergency shutdowns upon reaching set thresholds.

[0215] 1. Overcurrent protection

[0216] Derating threshold: When the discharge or charging current exceeds the rated maximum continuous current (e.g., 210A) but is below the hardware peak current (e.g., 300A), the digital control unit first attempts to reduce power (reduce the PWM duty cycle) to limit the current to within the rated value. If power reduction is ineffective (e.g., a load short circuit causes the current to continue to rise), an emergency shutdown is initiated.

[0217] Shutdown threshold: When the current instantaneously exceeds the hardware peak current (300A), the comparator inside the digital control unit directly triggers PWM cycle-by-cycle current limiting or hardware-level blocking, turning off all silicon carbide MOSFETs within 1 microsecond, while the ideal diode drive is also cut off. This hardware-level protection does not rely on software sampling delay, ensuring that the device is not burned out.

[0218] 2. Overvoltage and undervoltage protection

[0219] Overvoltage of charging input: When the input voltage of the charging pile exceeds the maximum rated value of the high voltage side of the module (e.g., 1050V), the digital control unit blocks the PWM and disconnects the input contactor to prevent silicon carbide devices from breaking down.

[0220] Overvoltage discharge output: When the voltage of the original vehicle's high-voltage bus unexpectedly spikes (exceeding the rated platform voltage by more than 15%), possibly due to excessive energy recovery or malfunction of the original vehicle's BMS, the module immediately stops discharging to prevent the electrical energy of the auxiliary small battery from being forcibly poured into the high-voltage circuit.

[0221] Additional small battery undervoltage: When the voltage of the additional small battery is lower than the over-discharge protection point (e.g., the value corresponding to 2.50V for a single cell), the digital control unit blocks the discharge PWM and prohibits any discharge behavior, allowing only charging (if a 12V charging signal is detected).

[0222] 3. Short circuit protection

[0223] Output short circuit: If a short circuit occurs in the original vehicle high-voltage bus during discharge mode (e.g., due to a vehicle accident), the internal current of the module will rise sharply. At this time, the overcurrent protection will be triggered in microseconds, and the reverse blocking characteristic of the ideal diode will prevent the additional small battery from feeding energy to the short circuit point, avoiding secondary disasters.

[0224] Input short circuit: If the positive and negative terminals of the attached small battery are accidentally short-circuited, the input fuse inside the module will blow, and the digital control unit will detect the abnormal voltage drop and immediately shut down all drives.

[0225] 4. Communication or sensor failure protection

[0226] Sensor open circuit or short circuit detection: The digital control unit periodically applies a small test current (without interfering with normal sampling) to each temperature and current sensor to check their response. If a sensor failure is detected (readings out of range or remain unchanged), the module reports a sensor fault and limits the power output to a minimum safe level (e.g., 10% of the rated current) until the fault is resolved.

[0227] The second embodiment of this application is as follows:

[0228] Please see Figure 3 This invention provides an ultra-wide voltage adaptable bidirectional power supply module for electric vehicles, applied to an ultra-wide voltage adaptable bidirectional power supply control method for electric vehicles as provided in the first embodiment, comprising:

[0229] The bidirectional power conversion unit employs a four-phase interleaved parallel topology. The main power switching devices are silicon carbide MOSFETs, and an ideal diode circuit composed of silicon carbide Schottky diodes is connected in series at the output of each bridge arm. The low-voltage side of this unit connects to an additional small battery pack (this small battery pack is of low-voltage specification, such as 48V / 64V / 90V, and is provided by the user). The high-voltage side is connected in parallel to the positive and negative terminals of the original vehicle's high-voltage battery pack via a T-connector. The four-phase interleaved parallel structure cancels out the current ripple of each phase, supporting a high current output of over 200A when the low-voltage side input is 64V, achieving a power transmission of up to 10kW. By replacing the silicon carbide devices with different voltage ratings (e.g., from 750V to 1700V), the input and output voltage range of this unit can cover 39V to 1000V, adapting to vehicle models with different voltage platforms.

[0230] The signal detection unit includes multiple differential amplifier sampling circuits, a 12V auxiliary power supply signal detection circuit, and an optocoupler-isolated key ignition signal detection circuit. Among these:

[0231] The differential amplifier is used to collect the voltage of the original high-voltage battery pack, the voltage of the auxiliary battery, the current and temperature of each phase of the bidirectional conversion unit in real time. All analog signals are converted into digital signals after being conditioned by the differential amplifier and sent to the digital control unit.

[0232] The 12V auxiliary power signal detection circuit is used to connect to the 12V auxiliary power pin in the DC charging pile interface (±12V pin in the 9-pin fast charging or 7-pin slow charging) to identify the physical connection and payment activation status of the charging pile.

[0233] The key ignition signal detection circuit is connected to the original car key switch's 12V ACC signal, which is then isolated by an optocoupler and input to the digital control unit as the trigger source for system wake-up.

[0234] The digital control unit receives the digital signal from the signal detection unit and executes the ultra-wide voltage adaptation bidirectional power control method for electric vehicles as described in the first embodiment, generating a PWM drive signal to control the switching state of the silicon carbide MOSFET and the conduction and turn-off of the ideal diode.

[0235] Regarding the system in the above embodiments, the specific ways in which each module performs operations have been described in detail in the embodiments related to the method, and will not be elaborated here.

[0236] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the disclosure herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein.

[0237] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope.

Claims

1. A bidirectional power supply control method for electric vehicles with ultra-wide voltage adaptability, characterized in that, Includes the following steps: When the vehicle is turned off and not connected to a charging station, the digital control unit enters a deep sleep mode, retaining only the optocoupler-isolated key ignition signal detection branch with power; when a key ignition signal edge transition is detected, the digital control unit is awakened, performs multi-level self-tests and sequentially soft-starts the auxiliary power supply, and enters standby monitoring state; The signal detection unit monitors the voltage value of the 12V auxiliary power supply pin in the charging pile interface. When the voltage jumps from low level to high level and remains stable for more than the preset de-jitter time, the charging start is confirmed, and the bidirectional power conversion unit is controlled to enter the buck charging mode to charge the additional small battery. When the vehicle is not connected to a charging pile and is in motion, the total voltage of the original high-voltage battery pack is sampled in real time to determine the current state of charge range. When it is determined to be in the plateau range, the boost discharge mode is activated, and the low-voltage electricity of the auxiliary small battery is boosted to match the voltage of the original high-voltage battery pack and then injected in parallel. The injection current is dynamically adjusted according to the original vehicle load. When it is determined to be in the high charge range, discharge is prohibited. When it is determined to be in the low charge range, the injection current is linearly reduced until it is completely cut off. The system monitors the values ​​of key temperature points in the bidirectional power conversion unit in real time. When any temperature point reaches the preset derating threshold, it performs graded power reduction protection. When any temperature point reaches the preset shutdown threshold, it performs an emergency shutdown and enters a fault lockout state.

2. The ultra-wide voltage adaptability bidirectional power supply control method for electric vehicles as described in claim 1, characterized in that, Multi-stage self-testing and step-by-step soft-start auxiliary power supply, including: The first stage involves the digital control unit self-testing the core and clock; the second stage involves a soft-start low-dropout linear regulator powering the analog front-end circuit; the third stage involves a self-test of each differential amplifier sampling channel; and the fourth stage involves a soft-start isolated DC-DC converter powering the silicon carbide MOSFET drive circuit. If any stage of self-test fails, the system enters fail-safe mode.

3. The ultra-wide voltage adaptability bidirectional power supply control method for electric vehicles as described in claim 1, characterized in that, The specific process for confirming the charging start-up is as follows: A high threshold and a low threshold are set by a hysteresis comparator, and a de-jitter delay filter is used. Charging is only confirmed when the voltage of the 12V auxiliary power supply pin exceeds the high threshold and remains stable for more than 200 milliseconds. Specifically, charging is confirmed to be complete when the voltage drops below the low threshold and remains below it for more than 200 milliseconds.

4. The ultra-wide voltage adaptability bidirectional power supply control method for electric vehicles as described in claim 1, characterized in that, Buck charging modes include: First, a pre-charge check is performed to confirm that the auxiliary small battery is connected normally, the charging pile input voltage is normal, and the temperature conditions are permissible. Then, the constant current charging stage is entered, and the charging current follows the set value through current closed-loop control. When the voltage of the auxiliary small battery rises to the constant voltage transition voltage, the constant voltage charging stage is switched to maintain the voltage constant until the charging current decays to the cutoff current. Finally, charging is terminated and standby monitoring is entered.

5. The ultra-wide voltage adaptability bidirectional power supply control method for electric vehicles as described in claim 1, characterized in that, Determining the current state of charge interval includes: The system retrieves a pre-stored voltage-state-of-charge (SOC) range mapping table and calculates the average voltage of each cell based on the total number of series-connected cells in the original vehicle's high-voltage battery pack. When the average voltage of a cell is higher than a first threshold, it is determined to be in a high-charge zone, corresponding to a SOC higher than 80%. When the average voltage of a cell is between the first and second thresholds, it is determined to be in a plateau zone, corresponding to a SOC between 20% and 80%. When the average voltage of a cell is lower than the second threshold, it is determined to be in a low-charge zone, corresponding to a SOC lower than 20%. The system also features dynamic calibration and temperature compensation functions.

6. The ultra-wide voltage adaptability bidirectional power supply control method for electric vehicles as described in claim 1, characterized in that, The injected current is dynamically adjusted according to the original vehicle load, including: The load condition is determined based on the voltage change rate of the original vehicle's high-voltage bus. The injected current is increased during rapid acceleration or climbing, and the injected current is maintained or decreased during constant speed or coasting. Furthermore, the rise and fall of the injected current are achieved by using a ramp function to smoothly cut in and out, avoiding sudden changes in current.

7. The ultra-wide voltage adaptability bidirectional power supply control method for electric vehicles as described in claim 1, characterized in that, The graded power reduction protection includes: when the temperature reaches the derating threshold, progressive measures are taken in sequence to reduce the output current, reduce the PWM switching frequency, and reduce the number of interleaved parallel working phases, until the temperature drops below the derating threshold by a hysteresis amount and stabilizes, and then the power is gradually restored. Emergency shutdown includes: immediately blocking the PWM drive signals of all silicon carbide MOSFETs through hardware-level interrupt, cutting off the drive bias of the ideal diode, disconnecting the input contactor in charging mode, recording fault information and illuminating the red fault indicator light. To exit the fault lockout state, manual power-off and restart are required and the temperature must be reduced to a safe range.

8. The ultra-wide voltage adaptability bidirectional power supply control method for electric vehicles as described in claim 1, characterized in that, The method further includes: When the discharge current or charging current exceeds the rated maximum continuous current but is lower than the hardware peak current, the current is limited to the rated value by reducing the PWM duty cycle; when the current exceeds the hardware peak current, the hardware comparator triggers cycle-by-cycle current limiting or directly blocks all silicon carbide MOSFETs.

9. The ultra-wide voltage adaptability bidirectional power supply control method for electric vehicles as described in claim 1, characterized in that, The method further includes: The voltage of the additional small battery is monitored in real time. When the voltage is lower than the over-discharge protection point, any discharge behavior is prohibited, and only charging is allowed. When a failure of the temperature or current sensor is detected, the output power will be limited to the minimum safe level and a fault will be reported.

10. A bidirectional power supply module for electric vehicles with ultra-wide voltage adaptability, applied to the bidirectional power supply control method for electric vehicles with ultra-wide voltage adaptability as described in claim 1, characterized in that, include: The bidirectional power conversion unit adopts a four-phase interleaved parallel topology. The main power switching device is a silicon carbide MOSFET, and an ideal diode composed of silicon carbide Schottky diodes is connected in series at the output end of each bridge arm. The low-voltage side of the unit is connected to an additional small battery, and the high-voltage side is connected in parallel to the original vehicle high-voltage battery pack through a T-connector. By replacing silicon carbide devices with different voltage ratings, the input and output voltage range covers 39V to 1000V. The signal detection unit includes multiple differential amplifier sampling circuits, a 12V auxiliary power supply signal detection circuit, and an optocoupler-isolated key ignition signal detection circuit. The differential amplifiers are used to collect the voltage of the original vehicle's high-voltage battery pack, the voltage of the auxiliary small battery, the current of each phase, and the temperature. The 12V auxiliary power supply signal detection circuit is connected to the 12V auxiliary power supply pin in the charging pile interface. The optocoupler-isolated key ignition signal detection circuit is connected to the 12V ACC signal line of the original vehicle's key ignition switch. The digital control unit receives the digital signal from the signal detection unit and executes the ultra-wide voltage adaptation bidirectional power control method for electric vehicles as described in any one of claims 1 to 9, generating a PWM drive signal to control the switching state of the silicon carbide MOSFET and the conduction and turn-off of the ideal diode.

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