A multi-threshold hierarchical undervoltage protection control method and device for a battery-powered fan

Abstract

The application discloses a kind of multi-threshold value grading under-voltage protection control method and device of battery-powered fan, and relates to the field of battery-powered fan control.The multi-threshold value grading under-voltage protection control method and device of battery-powered fan include the following steps: S1, obtain fan under-voltage protection response data, and carry out sampling synchronization, sampling frame marking and scale unification;S2, identify disturbance frame and candidate sampling window, generate sampling phase lock identification;S3, identify current under-voltage control interval, construct under-voltage protection state feature vector;S4, execute grading speed reduction, under-voltage shutdown, recovery lockout and soft start control, generate under-voltage control label.The application effectively improves the credibility of battery terminal voltage sampling, the continuity of low-voltage stage fan operation and the stability of under-voltage protection action, solves the problem of under-voltage misjudgment, misshutdown, misrecovery and frequent start-stop caused by voltage sampling time and driving switch phase coupling.

Description

Technical Field

[0001] This invention relates to the field of battery-powered fan control, specifically to a multi-threshold hierarchical undervoltage protection control method and device for battery-powered fans. Background Technology

[0002] With the development of portable fans, mobile fans, and fans without mains power, fan motors mostly use PWM drive for speed control. During the switching of the MOSFET between on and off, duty cycle updates, and sudden changes in motor current, ripple, spikes, and transient rebounds occur in the battery terminal voltage. Existing solutions often filter the voltage after sampling and then compare the filtered voltage value with voltage warning thresholds, undervoltage protection thresholds, and undervoltage recovery thresholds, without specifying the correspondence between the voltage sampling trigger position and the PWM drive state.

[0003] For example, the invention patent with publication number CN104300509B discloses an undervoltage protection load latch circuit applicable to various lithium battery protection schemes, including: an undervoltage detection circuit and a load / charger detection circuit; in the latter, the positive input terminal of the first comparator is connected to the load detection reference voltage, and the negative input terminal is connected to the load detection terminal; the positive input terminal of the second comparator is connected to the first charger detection reference voltage, and the negative input terminal is connected to the charger detection terminal; the positive input terminal of the third comparator is connected to the charger detection terminal, and the negative input terminal is connected to the second charger detection reference voltage; the input terminal of the three-input OR gate is connected to the output terminals of the three comparators, and the output terminal is connected to the input terminal of the filter circuit; the clock terminal of the D flip-flop is connected to the output terminal of the filter circuit, the reset terminal is connected to the non-undervoltage state terminal, and the Q terminal is connected to the undervoltage release terminal; the gate of the high-voltage NMOS transistor is connected to the undervoltage state terminal, the source is grounded, and the drain is connected to the load detection terminal through the first resistor; the gate of the high-voltage PMOS transistor is connected to the non-undervoltage state terminal, the source is connected to the power supply terminal, and the drain is connected to the charger detection terminal through the second resistor.

[0004] For example, invention patent CN111864840B discloses a solar charge controller with load control function, including: a solar cell delay access circuit, a solar cell open-circuit voltage detection circuit, a battery floating voltage detection circuit, an MPPT maximum power point switching circuit, a battery charging voltage switching circuit, a battery charging circuit, and a charging management IC chip; a battery undervoltage detection circuit, a solar start-up self-locking circuit, a load switch circuit, and a charging status detection circuit; the MPPT maximum power point switching circuit generates a maximum power point switching signal for the charging management IC chip; the battery charging circuit charges the battery under the management of the charging management IC chip; the solar start-up self-locking circuit, after obtaining the undervoltage detection signal and delaying for a threshold time T, controls the load switch circuit to supply power to the load. This invention has strong anti-interference capability, requires no programming, and the controller can track the maximum power point of the solar panel and control the load switch according to the battery voltage.

[0005] In existing technologies, when the sampling trigger position continuously falls within PWM ripple peak frames, ripple valley frames, or MOSFET switching edge disturbance frames, the voltage value involved in threshold judgment will deviate from the stable load voltage for a long period, leading to deviations in warning speed reduction, undervoltage shutdown, and recovery restart actions. If the sampling rhythm of the voltage detection module has a fixed relationship with the PWM switching rhythm, it may always sample near ripple valleys or peaks, causing the sampling results to deviate from the true average voltage for a long period.

[0006] Therefore, in order to address the above problems, there is an urgent need for a multi-threshold hierarchical undervoltage protection control method and device for battery-powered fans. Summary of the Invention

[0007] Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a multi-threshold hierarchical undervoltage protection control method and device for battery-powered fans, which solves the problems of undervoltage misjudgment, false shutdown, false recovery, and frequent start-stop caused by the phase coupling between voltage sampling time and drive switch.

[0008] Technical solution

[0009] To achieve the above objectives, the present invention provides the following technical solution: a multi-threshold hierarchical undervoltage protection control method and apparatus for a battery-powered fan, comprising: S1, acquiring fan undervoltage protection response data and performing sampling synchronization, sampling frame marking, and scale unification to obtain a fan undervoltage protection response dataset; S2, based on the fan undervoltage protection response dataset, identifying disturbance frames and candidate sampling windows, generating sampling phase lock identifiers, and constructing a load voltage dataset; S3, based on the load voltage dataset, generating a reliable load voltage, identifying the current undervoltage control interval, and constructing an undervoltage protection state feature vector; S4, based on the undervoltage protection state feature vector, performing hierarchical speed reduction, undervoltage shutdown, recovery lockout, and soft start control, and generating an undervoltage control tag.

[0010] Further, the specific process of acquiring fan undervoltage protection response data and performing sampling synchronization, sampling frame marking, and scale unification to obtain the fan undervoltage protection response dataset is as follows: Data is collected during the operation of the battery-powered fan to obtain fan undervoltage protection response data. This data includes the battery terminal voltage detection value, sampling trigger time, PWM cycle identifier, PWM phase position, MOSFET switch edge identifier, current duty cycle setting, current speed limit setting, motor current detection value, current battery specification identifier, safety parameter group, and fan load identifier. Using the PWM cycle identifier as the synchronization reference for voltage sampling, the cycle number is recorded at the beginning of each PWM cycle. When acquiring the battery terminal voltage detection value within the same cycle, the voltage detection value is compared with the corresponding... The PWM cycle number, PWM phase position, MOSFET switching edge identifier, and current speed limit setting are written into the same sampling frame, which is a voltage sampling frame. When the voltage sampling frame is within the sampling frame containing the MOSFET's on or off edge, or within the preceding and following N sampling frames, the voltage sampling frame is marked as a disturbance sampling frame. When the voltage sampling frame is within the period when the MOSFET switching edge identifier has not switched, the voltage sampling frame is marked as a stable sampling frame. When the PWM phase position cannot be determined, the voltage sampling frame is marked as a frame to be resampled, and it is re-acquired in the next sampling cycle. The battery terminal voltage detection value, current duty cycle setting, motor current detection value, and current speed limit setting in the stable sampling frame are subjected to amplitude normalization and scaling processing to generate a fan undervoltage protection response dataset.

[0011] Furthermore, based on the fan undervoltage protection response dataset, the specific process for identifying disturbance frames and candidate sampling windows is as follows: Based on the fan undervoltage protection response dataset, the sampling frames are grouped according to the PWM cycle identifier, with each group of sampling frames corresponding to one PWM output cycle; taking the sampling frame where the MOSFET turn-on edge is located as the reference, the sampling frame and the N sampling frames before and after it are marked as turn-on edge disturbance frames; taking the sampling frame where the MOSFET turn-off edge is located as the reference, the sampling frame and the N sampling frames before and after it are marked as turn-off edge disturbance frames; taking the sampling frame where the PWM duty cycle update is located as the reference, the sampling frame and the N sampling frames after it are marked as duty cycle transition disturbance frames; the difference between the motor current detection values ​​of adjacent sampling frames within the same PWM cycle is compared, and if the absolute value of the motor current difference between two adjacent frames is greater than the current change threshold, then the next sampling frame and the N sampling frames after it are marked as current disturbance frames; The battery terminal voltage detection values ​​of adjacent sampling frames within the same PWM cycle are compared by difference. If the absolute value of the difference between the battery terminal voltages of two adjacent frames is greater than the voltage change threshold, the next sampling frame and the following N sampling frames are marked as voltage disturbance frames. After removing the five types of disturbance frames, sampling frame segments are searched from the remaining sampling frames within the same PWM cycle. When the number of sampling frames in the sampling frame segment is not less than the number of stable window frames, and the interval between the starting sampling frame of the sampling frame segment and the sampling frame of the MOSFET switching edge is not less than the edge interval frame, the sampling frame segment is marked as a candidate sampling window. When only one candidate sampling window is identified within the same PWM cycle, the candidate sampling window is used as the target sampling window. When there is no candidate sampling window within the same PWM cycle, the PWM cycle is marked as an unusable sampling cycle, and the candidate sampling window is re-identified after adjusting the voltage sampling trigger position in the next round.

[0012] Furthermore, the specific process for generating the sampling phase lock identifier is as follows: when the voltage sampling trigger frames within K consecutive PWM cycles do not fall into the target sampling window and all fall into the same type of disturbance frame, it is determined that the voltage sampling trigger position and the PWM cycle form a fixed phase coupling, a sampling phase lock identifier is generated, and the sampling frame number range and disturbance frame type corresponding to the phase lock are recorded; in the next PWM cycle, the voltage sampling trigger position is adjusted so that the voltage sampling trigger position moves into the target sampling window; when the voltage sampling trigger frames within K consecutive PWM cycles all fall into the target sampling window, the corresponding PWM cycles are not marked as unusable sampling cycles, and the voltage sampling trigger frames do not carry a disturbance frame identifier, it is determined that the voltage sampling trigger position does not form a fixed phase coupling, and a sampling phase normal identifier is generated.

[0013] Furthermore, the specific process for constructing the on-load voltage dataset is as follows: Write determination is performed on the voltage sampling frame within each PWM cycle; if the current PWM cycle is marked as an unavailable sampling cycle, or the current voltage sampling frame carries any identifier from the disturbance frame, or the current PWM cycle has a sampling phase lock identifier, then writing the voltage sampling frame into the on-load voltage dataset is prohibited, and the voltage sampling frame is written to the disturbance recording area; when the current voltage sampling frame is within the target sampling window, is not marked as an unavailable sampling cycle, does not carry a disturbance frame identifier, and does not have a sampling phase lock identifier, the current voltage sampling frame is read. The current voltage sampling frame is marked as a stable sampling frame when the absolute value of the difference between the two values ​​is not greater than the voltage fluctuation threshold. When the absolute value of the difference is greater than the voltage fluctuation threshold, the current voltage sampling frame is marked as a voltage verification frame, and the target sampling window identification and sampling frame writing determination are re-executed in the next PWM cycle. Starting from the PWM cycle in which the first stable sampling frame is obtained, stable sampling frames in subsequent PWM cycles are continuously read according to the number of recording cycles R. When the number of continuously obtained stable sampling frames reaches R, R stable sampling frames are written into the load voltage dataset.

[0014] Furthermore, the specific process for generating a reliable on-load voltage based on the on-load voltage dataset is as follows: Based on the on-load voltage dataset, when the voltage sampling frame is within the target sampling window, and the current PWM cycle is not marked as an unavailable sampling cycle, and the voltage sampling frame does not carry any identifier from the disturbance frame, and the current PWM cycle does not generate a sampling phase lock identifier, the voltage sampling frame is marked as a candidate valid voltage sampling frame; when the current duty cycle level or the current speed limit level is higher than the level corresponding to the previous valid voltage sampling frame, the current drive state is recorded as a drive output increase state; when the drive output increases... In the current state, if the current battery terminal voltage detection value is not higher than the sum of the battery terminal voltage detection value and the voltage fluctuation threshold of the previous effective voltage sampling frame, and the current motor current detection value is not lower than the difference between the motor current detection value and the current fluctuation threshold of the previous effective voltage sampling frame, the current candidate effective voltage sampling frame is determined to have passed the drive response consistency check. Candidate effective voltage sampling frames that fail the drive response consistency check are marked as voltage verification frames, and vice versa. The battery terminal voltage detection values ​​of the M effective voltage sampling frames are then arithmetically averaged to generate a reliable load voltage.

[0015] Further, the specific process of identifying the current undervoltage control interval and constructing the undervoltage protection state feature vector is as follows: When all M effective voltage sampling frames originate from the target sampling window, and the corresponding PWM cycles do not carry disturbance frame identifiers and sampling phase lock identifiers, the reliable load voltage is marked as the first reliability level; when a voltage verification frame is reconfirmed and participates in the generation, it is marked as the second reliability level; when the number of effective voltage sampling frames does not reach M, no reliable load voltage for recovery and restart is generated; the reliable load voltage is compared with the voltage warning threshold, undervoltage protection threshold, and undervoltage recovery threshold respectively to identify the current battery power supply state; if... If the trusted load voltage is higher than the voltage warning threshold, it is identified as the normal operation range; if the trusted load voltage is lower than or equal to the voltage warning threshold but higher than the undervoltage protection threshold, it is identified as the warning speed reduction range; if the trusted load voltage is lower than or equal to the undervoltage protection threshold, it is identified as the undervoltage protection range; if the fan has stopped and the trusted load voltage has not reached the undervoltage recovery threshold, it is identified as the recovery lockout range; if the fan has stopped and the trusted load voltage has reached the undervoltage recovery threshold, and the trusted load voltage is at the first trusted level, it is identified as the allowed recovery range; the undervoltage protection status feature vector is constructed by comparing threshold ranges and using sampling status coding.

[0016] Furthermore, based on the undervoltage protection state feature vector, the specific process of performing graded speed reduction, undervoltage shutdown, recovery lockout, and soft start control is as follows: Extract the undervoltage protection state feature vector. If the current undervoltage control interval is within the normal operating interval, maintain the current fan speed setting and continuously perform drive phase collaborative sampling. If the current undervoltage control interval is within the warning speed reduction interval, based on the voltage sub-interval where the reliable load voltage is located, retrieve the corresponding target speed limit setting from the speed limit setting table in the storage module and output a graded speed reduction command to the PWM drive module, causing the fan to decrease from the current speed setting according to the order of adjacent speed limits in the speed limit setting table. Each time a speed control cycle is completed, the speed limit setting is decreased by one level. The fan speed is adjusted until it matches the target speed limit. If the current undervoltage control range is within the undervoltage protection range, an undervoltage shutdown command is output to the PWM drive module to stop the fan motor and mark the current state as undervoltage shutdown. Directly relying on the voltage rebound value at the moment of shutdown for recovery judgment is prohibited. If the current undervoltage control range is within the recovery lockout range, the fan remains off, and candidate sampling window identification and reliable load voltage generation continue. If the current undervoltage control range is within the allowable recovery range, the recovery lockout is released, and the recovery start speed is matched according to the range of the current reliable load voltage, outputting a soft-start command to the PWM drive module.

[0017] Further, the specific process for generating the undervoltage control tag is as follows: The control action type, battery specification identifier, fan load identifier, PWM phase position, target sampling window position, and trusted load voltage are written into the same undervoltage control tag. When the same PWM phase position experiences an undervoltage shutdown within a statistical period and fails to reach the undervoltage recovery threshold before generating a recovery start command, it is marked as a recovery erroneous trigger. When the trusted load voltage falls below or equals the undervoltage protection threshold again within a continuous verification period after a soft start, it is marked as undervoltage again after a soft start, and the corresponding PWM phase position is written into the phase avoidance record. The phase avoidance record is written into the non-volatile storage module. After power-on, the current battery specification identifier and the current fan load identifier are checked. If they match and the record is complete, the tag continues to be used. If they do not match, the record is missing, or the record verification fails, the safety parameter group is called, and the target sampling window identification is re-executed.

[0018] Furthermore, a second aspect of the present invention provides a multi-threshold graded undervoltage protection control device for a battery-powered fan, applied to a multi-threshold graded undervoltage protection control method for a battery-powered fan, comprising: a voltage detection module connected to the battery output terminal, used to collect the battery terminal voltage detection value and the motor current detection value, and output the collected signals to a control module after voltage division sampling and filtering; a control module connected to the voltage detection module, the fan drive module, and the storage module respectively, used to read the battery terminal voltage detection value, the motor current detection value, the PWM period identifier, the PWM phase position, the MOSFET switch edge identifier, the current duty cycle level, the current speed limit level, the battery specification identifier, and the fan load identifier, and based on the fan undervoltage protection response data, to perform disturbance frame identification, target sampling window determination, sampling phase lock determination, load voltage dataset construction, reliable load voltage generation, and multi-threshold interval judgment; and a fan drive module connected to the control module and the fan motor respectively, used to receive data from the control module. The system outputs graded speed reduction commands, undervoltage shutdown commands, hold shutdown commands, and soft-start commands, and controls the switching state of MOSFETs via PWM signals to adjust the fan motor speed, stop the fan motor, or restart the fan motor. The storage module, connected to the control module, is a non-volatile memory unit used to store voltage warning thresholds, undervoltage protection thresholds, undervoltage recovery thresholds, speed limit tables, recovery start speed tables, speed regulation cycles, battery specification identifiers, fan load identifiers, disturbance spread frame counts, phase lock determination cycle counts, reliable load voltage generation frame counts, stable sampling record counts, stable window frame counts, edge interval frames, current surge thresholds, voltage surge thresholds, voltage fluctuation thresholds, current fluctuation thresholds, statistical cycles, continuous verification cycles, phase avoidance records, target sampling window records, and safety parameter groups. The power supply module, connected to the battery, voltage detection module, control module, fan drive module, and storage module, converts the battery output voltage into the operating voltage required by each module.

[0019] Beneficial effects

[0020] The present invention has the following beneficial effects: (1) In this invention, by using the marking rules of turn-on edge disturbance frame, turn-off edge disturbance frame, duty cycle transition disturbance frame, current disturbance frame and voltage disturbance frame, the sampling frames corresponding to MOS transistor switching spikes, motor current sudden changes and battery terminal voltage jumps are excluded from direct threshold comparison, thereby reducing false alarms, false protection triggers and false recovery judgments caused by PWM ripple and switching transients.

[0021] (2) In this invention, by sampling phase locking determination, it is identified whether the voltage sampling trigger frame falls into the same type of disturbance frame within K consecutive PWM cycles, and when a fixed phase coupling is formed, the voltage sampling trigger position of the next cycle is adjusted so that the sampling trigger position is moved into the target sampling window, thereby solving the problem of systematically high or low voltage values ​​caused by long-term phase overlap between the sampling cycle and the PWM cycle.

[0022] (3) In this invention, by comparing the voltage warning threshold, undervoltage protection threshold and undervoltage recovery threshold, the current state is divided into normal operation interval, warning speed reduction interval, undervoltage protection interval, recovery lockout interval and allowed recovery interval, and the confidence level is used as the restriction condition for recovery restart, so that the fan first performs graded speed reduction in the low voltage stage, and then performs undervoltage shutdown and recovery lockout, thereby reducing the risk of repeated start-stop at the low power end.

[0023] (4) In this invention, the voltage range status code, sampled reliable status code, load control status code, current stability status code, sampled phase status code and sampled disturbance status code are arranged in a fixed order through the undervoltage protection status feature vector, so that the control module can select graded speed reduction, undervoltage shutdown, recovery lockout or soft start action based on the same judgment record, thereby improving the reproducibility of the undervoltage protection process and the consistency of control action.

[0024] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0025] Figure 1 This is a flowchart of a multi-threshold hierarchical undervoltage protection control method for a battery-powered fan according to the present invention; Figure 2 This is a block diagram of a multi-threshold graded undervoltage protection control device for a battery-powered fan according to the present invention; Figure 3 This is a distribution diagram of the disturbance frame and the target sampling window within the PWM cycle of this invention; Figure 4 This is a candidate sampling window screening matrix diagram of the present invention; Figure 5 This is a comparison chart showing the misjudgments between the ordinary sampling method and the target window sampling method of this invention. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Please see Figures 1-5 This invention provides a technical solution: a multi-threshold hierarchical undervoltage protection control method for a battery-powered fan, comprising: S1, acquiring fan undervoltage protection response data and performing sampling synchronization, sampling frame marking, and scale unification to obtain a fan undervoltage protection response dataset; S2, based on the fan undervoltage protection response dataset, identifying disturbance frames and candidate sampling windows, generating sampling phase lock identifiers, and constructing a load voltage dataset; S3, based on the load voltage dataset, generating a reliable load voltage, identifying the current undervoltage control interval, and constructing an undervoltage protection state feature vector; S4, based on the undervoltage protection state feature vector, performing hierarchical speed reduction, undervoltage shutdown, recovery lockout, and soft start control, and generating an undervoltage control label.

[0028] Specifically, the process of acquiring fan undervoltage protection response data, performing sampling synchronization, sampling frame labeling, and scale unification to obtain the fan undervoltage protection response dataset is as follows: Data is collected during the operation of the battery-powered fan to obtain fan undervoltage protection response data. This data includes the battery terminal voltage detection value, sampling trigger time, PWM cycle identifier, PWM phase position, MOSFET switch edge identifier, current duty cycle setting, current speed limit setting, motor current detection value, current battery specification identifier, safety parameter group, and fan load identifier. The safety parameter group is a default control parameter group pre-written into the storage module. It includes voltage warning threshold, undervoltage protection threshold, undervoltage recovery threshold, default speed limit setting table, disturbance spread frame count N, phase lock determination cycle count K, reliable load voltage generation frame count M, stable sampling recording cycle count R, stable window frame count, edge interval frame, current surge threshold, voltage surge threshold, voltage fluctuation threshold, and current fluctuation threshold. When the threshold parameter group corresponding to the current battery specification identifier and fan load identifier is missing, record verification fails, or parameter calls are inconsistent, the safety parameter group is invoked.

[0029] Using the PWM cycle identifier as the synchronization reference for voltage sampling, the cycle number is recorded at the beginning of each PWM cycle. When acquiring the battery terminal voltage detection value within the same cycle, the voltage detection value, the corresponding PWM cycle number, PWM phase position, MOSFET switching edge identifier, and current speed limit gear are written into the same sampling frame. This written sampling frame is the voltage sampling frame. When the voltage sampling frame falls within the sampling frame containing the MOSFET's turn-on or turn-off edge, and within the preceding and following N sampling frames, the voltage sampling frame is marked as a disturbance sampling frame. When the voltage sampling frame does not fall within the MOSFET's turn-on or turn-off edge, it is marked as a disturbance sampling frame. Within the sampling frame containing the turn-on or turn-off edge and the preceding and following N sampling frames, and provided that no PWM duty cycle update occurs within the current PWM cycle, and the absolute value of the difference between the battery terminal voltage detection value of the current voltage sampling frame and the previous voltage sampling frame is not greater than the voltage fluctuation threshold, and the absolute value of the difference between the motor current detection value of the current voltage sampling frame and the previous voltage sampling frame is not greater than the current fluctuation threshold, when the voltage sampling frame falls within the period marked by the MOSFET switching edge not switching, the voltage sampling frame is marked as a stable sampling frame; when the PWM phase position cannot be determined, the voltage sampling frame is marked as... The frame to be resampled is collected again in the next sampling cycle. If the voltage sampling trigger frame falls into the same type of disturbance frame within K consecutive PWM cycles, the voltage sampling trigger position is adjusted so that the sampling point moves from the period with large switching disturbances to the PWM output period. The battery terminal voltage detection value, current duty cycle level, motor current detection value, and current speed limit level in the stable sampling frame are normalized for scale uniformity. The battery terminal voltage detection value is normalized according to the rated voltage scale parameter corresponding to the current battery specification, the motor current detection value is normalized according to the rated current scale parameter corresponding to the current fan load specification, the current duty cycle level is normalized according to the upper limit of the duty cycle level in the storage module, and the current speed limit level is normalized according to the highest level in the speed limit level table. The normalized data are all written to the same sampling frame field as input for subsequent disturbance frame identification, load voltage dataset construction, and reliable load voltage generation. This allows data collected under different battery specifications, different fan power, and different speed levels to be compared in the same undervoltage protection logic to generate a fan undervoltage protection response dataset.

[0030] like Figure 3The diagram shows the distribution of disturbance frames and the target sampling window within a PWM cycle. The horizontal axis represents the sampling frame number, the left vertical axis represents the battery terminal voltage detection value, and the right vertical axis represents the motor current detection value. It illustrates the correspondence between battery terminal voltage, motor current, disturbance sampling frames, stable sampling frames, and the target sampling window during the same PWM drive period. The light-colored vertical area represents the target sampling window, indicating that these sampling frames are located within a relatively stable sampling segment and can serve as a valid source for subsequent load voltage datasets. The blue broken line represents the battery terminal voltage detection value, and the dashed curve with square markings represents the motor current detection value. Crosses indicate disturbance sampling frames, mainly corresponding to the MOSFET's turn-on edge, turn-off edge, current abrupt change, or voltage jump position; dots indicate stable sampling frames, mainly distributed within the target sampling window.

[0031] As can be seen from the figure, the battery terminal voltage at the location corresponding to the disturbance sampling frame exhibits significant fluctuations, while the motor current also shows abrupt changes. Directly using these sampling frames to determine the voltage warning threshold, undervoltage protection threshold, and undervoltage recovery threshold can easily lead to false triggering of warnings, protection mechanisms, or recovery decisions. In contrast, the stable sampling frames within the target sampling window show more gradual voltage changes and smaller motor current fluctuations, making them more suitable as a source for calculating reliable load voltage.

[0032] This implementation improves the voltage sampling stability of the battery-powered fan under PWM drive conditions, reduces the risk of false alarms, false protection triggers, and false recovery caused by transient switching of MOSFETs, sudden changes in motor current, and fluctuations in battery terminal voltage, and provides a stable data foundation for reliable load voltage generation, graded speed reduction, undervoltage shutdown, and recovery startup.

[0033] Specifically, based on the fan undervoltage protection response dataset, the process of identifying disturbance frames and candidate sampling windows is as follows: Based on the fan undervoltage protection response dataset, sampling frames are grouped according to the PWM cycle identifier, with each group corresponding to one PWM output cycle. Within each group, the sampling frame number at the MOSFET turn-on edge, the sampling frame number at the MOSFET turn-off edge, the sampling frame number at the PWM duty cycle update, the motor current detection value, and the battery terminal voltage detection value are read. N represents the disturbance propagation frame number, measured in sampling frames, derived from the disturbance propagation frame number parameter in the storage module and consistent with the disturbance propagation frame number in the safety parameter group. N is determined based on the total number of sampling frames within the PWM cycle, the number of voltage stabilization sampling frames after the MOSFET turn-on edge, the number of voltage stabilization sampling frames after the MOSFET turn-off edge, and the number of current stabilization sampling frames after the PWM duty cycle update. The sampling frame number at the MOSFET turn-on edge is used as the sampling frame number. Using the sample frame as a reference, the sample frame and the N sample frames before and after it are marked as conduction edge disturbance frames; using the sample frame where the MOSFET turn-off edge is located as a reference, the sample frame and the N sample frames before and after it are marked as turn-off edge disturbance frames; using the sample frame where the PWM duty cycle update is located as a reference, the sample frame and the N sample frames after it are marked as duty cycle transition disturbance frames; the difference between the motor current detection values ​​of adjacent sample frames within the same PWM cycle is compared. If the absolute value of the difference between the motor currents of two adjacent frames is greater than the current mutation threshold, then the next sample frame and the N sample frames after it are marked as current disturbance frames; the difference between the battery terminal voltage detection values ​​of adjacent sample frames within the same PWM cycle is compared. If the absolute value of the difference between the battery terminal voltages of two adjacent frames is greater than the voltage mutation threshold, then the next sample frame and the N sample frames after it are marked as voltage disturbance frames.

[0034] The conduction edge disturbance frame is the sampling frame within the sampling frame containing the MOSFET's conduction edge and the N sampling frames before and after it; the turn-off edge disturbance frame is the sampling frame within the sampling frame containing the MOSFET's turn-off edge and the N sampling frames before and after it; the duty cycle transition disturbance frame is the sampling frame within the sampling frame containing the PWM duty cycle update and the N sampling frames after it; the current disturbance frame is the sampling frame within the N consecutive sampling frames starting from the next sampling frame when the absolute value of the motor current difference between adjacent sampling frames is greater than the current sudden change threshold; voltage disturbance... When the absolute value of the battery terminal voltage difference between adjacent sampling frames exceeds the voltage surge threshold, the next sampling frame is used as the starting point for sampling frames within N consecutive sampling frames. Conduction edge disturbance frames, deactivation edge disturbance frames, duty cycle transition disturbance frames, current disturbance frames, and voltage disturbance frames are not directly compared to the voltage warning threshold, undervoltage protection threshold, and undervoltage recovery threshold; they are only recorded as drive disturbances. After removing these five types of disturbance frames, the sampling frame segment is searched from the remaining sampling frames within the same PWM cycle. When the number of sampling frames in the sampling frame segment... When the sampling frame segment is not less than the number of stable window frames, and the interval between the starting sampling frame of the sampling frame segment and the MOSFET switching edge sampling frame is not less than the edge interval frame, the sampling frame segment is marked as a candidate sampling window. The edge interval frame is the minimum interval frame number between the starting sampling frame of the candidate sampling window and the adjacent MOSFET switching edge sampling frame, in units of sampling frames, derived from the edge interval frame parameter in the memory module. The value of the edge interval frame is not less than the number of disturbance extension frames N, used to ensure that the candidate sampling window does not fall within the range of the conduction edge disturbance frame and the turn-off edge disturbance frame. When only one candidate sampling window is identified in the same PWM cycle, the candidate sampling window is used as the target sampling window. When at least two candidate sampling windows are identified in the same PWM cycle, the target sampling window is determined in the following order: calculate the difference between the maximum and minimum detected values ​​of the battery terminal voltage in each candidate sampling window, retain the candidate sampling window whose difference is not greater than the window voltage range threshold as the first candidate window, and discard the candidate sampling window that exceeds the window voltage range threshold.

[0035] Calculate the difference between the maximum and minimum detected motor current values ​​within each first candidate window. First candidate windows with differences not exceeding the window current range threshold are retained as second candidate windows, while those exceeding the threshold are eliminated. The phase avoidance record in the storage module is read. If the PWM phase position corresponding to the second candidate window has been written into the phase avoidance record, the selection order of that second candidate window is reduced. The interval frame number between the starting sampling frame and the most recent MOSFET switching edge sampling frame for each second candidate window is counted. The most recent MOSFET switching edge sampling frame is the MOSFET turn-on edge sampling frame or MOSFET turn-off edge sampling frame with the smallest difference in sampling frame number between it and the starting sampling frame. The second candidate window with the largest interval frame number is determined as the target sampling window. If two second candidate windows have the same interval frame number, the sampling frame is selected. The second candidate window with a larger number of samples is determined as the target sampling window; if two second candidate windows still have the same number of sampling frames, the second candidate window with the later sampling frame number is determined as the target sampling window; if two second candidate windows have both been written into the phase avoidance record, the second candidate window with fewer avoidance records is selected first; when there is no candidate sampling window in the same PWM cycle, the PWM cycle is marked as an unusable sampling cycle, and the battery terminal voltage detection value in the unusable sampling cycle is not used to trigger recovery restart or to update the undervoltage recovery judgment result; if a preset number of consecutive PWM cycles are marked as unusable sampling cycles, after adjusting the voltage sampling trigger position in the next round, the voltage sampling trigger position will avoid the MOSFET turn-on edge, MOSFET turn-off edge, and PWM duty cycle update sampling frame, and the candidate sampling window will be re-identified.

[0036] As shown in Table 1, the candidate sampling window selection data table is used to determine the best sample based on the electrical fluctuation and timing characteristics of the window: PWM period C01 corresponds to W1, sampling frames 4-6, voltage range 0.03, current range 0.05, edge interval frame 3, and is selected as the target sampling window; C02 corresponds to W1, sampling frames 5-7, voltage range 0.04, current range 0.06, edge interval frame 4, and is selected as the target sampling window; C03 corresponds to W1, sampling frames 3-5, voltage range 0.09, current range 0.18, edge interval frame 2, and is removed due to large fluctuations in the indicators; C04 For W1, sampling frames 6-8, voltage range 0.02, current range 0.04, edge interval frame 5, selected as target sampling window; for C05, sampling frames 2-4, voltage range 0.11, current range 0.21, edge interval frame 1, electrical fluctuation exceeding limits is rejected; for C06, sampling frames 5-8, voltage range 0.03, current range 0.05, edge interval frame 4, determined as target sampling window; for C07, sampling frames 6-9, voltage range 0.02, current range 0.04, edge interval frame 5, filtered as target sampling window.

[0037] The overall pattern shows that windows with large voltage and current ranges and small edge intervals have poor sampling stability and are directly rejected; windows with small electrical ranges and sufficient edge intervals have stable waveforms and are all retained as valid target sampling windows, thus achieving fine-grained selection of PWM sampling intervals.

[0038] Table 1 Candidate Sampling Window Filtering Data Table

[0039] like Figure 4 The diagram shows the candidate sampling window selection matrix. The matrix uses the PWM cycle number as the vertical axis and the candidate sampling window number as the horizontal axis, displaying the window disturbance score for each candidate sampling window within different PWM cycles through matrix color blocks. The window disturbance score is characterized by the fluctuation of battery voltage, motor current, and the interval between the sampling frame and the MOSFET switching edge within the window. A smaller value indicates a more stable voltage sampling state within the candidate sampling window, making it more suitable as a target sampling window. Each row in the diagram corresponds to a PWM output cycle, and each column corresponds to a candidate sampling window. The positions marked with bold borders indicate the selected target sampling window within the corresponding PWM cycle. For example, window W1 has the lowest disturbance score in cycle C01, therefore W1 is selected as the target sampling window; window W2 has the lowest disturbance score in cycle C04, therefore W2 is selected as the target sampling window; and window W3 has the lowest disturbance score in cycle C05, therefore W3 is selected as the target sampling window. This demonstrates that this scheme does not perform voltage sampling at a fixed phase position, but rather dynamically selects the target sampling window based on the window disturbance score within each PWM cycle.

[0040] As illustrated in the figure, this process avoids disturbances caused by PWM switching edges, MOSFET turn-on / turn-off transients, and sudden changes in motor current. By moving the voltage sampling trigger position to a window with lower disturbance scores, it reduces the likelihood of sampled values ​​consistently falling within ripple peaks or valleys. This process makes the generated reliable load voltage more stable, reducing the risk of misjudgments during the comparison of voltage warning thresholds, undervoltage protection thresholds, and undervoltage recovery thresholds. It provides a more reliable data foundation for graded speed reduction, undervoltage shutdown, recovery lockout, and soft-start control.

[0041] In this implementation, the battery terminal voltage sampling location is changed from fixed sampling to target window sampling with periodic filtering. This reduces the occurrence of sampled values ​​falling at PWM ripple peaks, ripple valleys, and MOSFET switching spikes, improving the stability of the load voltage dataset. This provides a stable sampling source for generating reliable load voltage, comparing voltage warning thresholds, comparing undervoltage protection thresholds, and comparing undervoltage recovery thresholds, thereby reducing the probability of false triggering of graded speed reduction, false triggering of undervoltage shutdown, and false judgment of recovery restart.

[0042] Specifically, the process for generating the sampling phase lock identifier is as follows: When the voltage sampling trigger frames within K consecutive PWM cycles do not fall into the target sampling window and all fall into the same type of disturbance frame, it is determined that the voltage sampling trigger position and the PWM cycle form a fixed phase coupling, generating a sampling phase lock identifier. K is the number of phase lock determination cycles, with the unit being the PWM cycle. K is derived from the phase lock determination cycle number parameter in the storage module. K is determined based on the PWM frequency, sampling cycle, and the number of recovery false trigger tolerances, and is consistent with the number of phase lock determination cycles in the safety parameter group. The same type of disturbance frame includes conduction edge disturbance frames, turn-off edge disturbance frames, and so on. Duty cycle transition disturbance frames, current disturbance frames, and voltage disturbance frames are used. When the same voltage sampling trigger frame carries two or more types of disturbance frame identifiers, the main disturbance type is determined in the order of turn-on edge disturbance frame, turn-off edge disturbance frame, duty cycle transition disturbance frame, current disturbance frame, and voltage disturbance frame. The main disturbance type is then used to participate in the same type of disturbance judgment for K consecutive PWM cycles. When the voltage sampling trigger frames within K consecutive PWM cycles do not fall into the target sampling window, and the main disturbance types are not completely the same, but all carry disturbance frame identifiers, a mixed disturbance avoidance identifier is generated and executed in the next PWM cycle. The sampling trigger position is adjusted; and the sampling frame number range and disturbance frame type corresponding to phase locking are recorded; the voltage sampling trigger position is adjusted in the next PWM cycle. During adjustment, if the target sampling window has been identified in the next PWM cycle, the starting sampling frame number and ending sampling frame number of the target sampling window are read, the intermediate sampling frame number of the target sampling window is calculated, and the current voltage sampling trigger frame number is adjusted to the intermediate sampling frame number; when there is a sampling frame number corresponding to the phase avoidance record in the target sampling window, the voltage sampling trigger frame number is adjusted to the sampling frame number that is farthest from the MOSFET switch edge sampling frame in the target sampling window that has not been written with the phase avoidance record; the control module generates a sampling trigger delay amount according to the adjusted sampling frame number and the start of the PWM cycle, and triggers voltage sampling according to the sampling trigger delay amount in the next PWM cycle, and then moves the voltage sampling trigger position to the target sampling window; if the target sampling window is not identified in the next PWM cycle, the PWM cycle is marked as an unusable sampling cycle, and the battery terminal voltage detection value in the cycle is not used to trigger recovery restart and undervoltage recovery judgment; thus, the voltage sampling trigger position is moved to the target sampling window. When the next PWM cycle is marked as an unavailable sampling cycle, the sampling trigger position of the previous cycle is not used for threshold comparison, and the target sampling window is re-identified in the next PWM cycle.

[0043] When the voltage sampling trigger frames within K consecutive PWM cycles all fall into the target sampling window, the corresponding PWM cycles are not marked as unavailable sampling cycles, and the voltage sampling trigger frames do not carry disturbance frame identifiers, it is determined that the voltage sampling trigger position has not formed a fixed phase coupling, and a sampling phase normal identifier is generated; if neither the sampling phase locking condition nor the sampling phase normal condition is met, the sampling trigger configuration of the previous cycle is maintained, and the sampling phase locking status determination is re-executed in the next PWM cycle.

[0044] In this implementation scheme, voltage sampling avoids switching edges, current surges, and voltage jumps. This reduces the probability of the sampling trigger position remaining at the peak or valley of the PWM ripple for an extended period, improving the stability of the load voltage sampling results and providing reliable sampling data for generating reliable load voltages, determining undervoltage recovery, and implementing soft-start control.

[0045] Specifically, the process of constructing the on-load voltage dataset is as follows: Write decisions are made for the voltage sampling frames within each PWM cycle. If the current PWM cycle is marked as an unavailable sampling cycle, or the current voltage sampling frame carries any identifier from the disturbance frame, or the current PWM cycle has a sampling phase lock identifier, then writing the voltage sampling frame to the load voltage dataset is prohibited, and the voltage sampling frame is written to the disturbance recording area. When the current voltage sampling frame is within the target sampling window, is not marked as an unavailable sampling cycle, does not carry a disturbance frame identifier, and does not have a sampling phase lock identifier, the battery terminal voltage detection values ​​of the current voltage sampling frame and the previous stable sampling frame are read. When the absolute value of the difference between the two is not greater than the voltage fluctuation threshold, the current voltage sampling frame is marked as a stable sampling frame. When the absolute value of the difference between the two is greater than the voltage fluctuation threshold, the current voltage sampling frame is marked as a voltage verification frame. The target sampling window identification and sampling frame writing judgment are re-executed in the next PWM cycle. Starting from the PWM cycle in which the first stable sampling frame is obtained, stable sampling frames in subsequent PWM cycles are continuously read according to the number of recording cycles R. R is the number of stable sampling recording cycles, in units of PWM cycles, derived from the stable sampling recording cycle number parameter in the storage module, and consistent with the stable sampling recording cycle number in the safety parameter group. R is determined based on the PWM frequency, sampling cycle, the number of cycles required for the battery terminal voltage detection value to stabilize, and the number of consecutive stable cycles required for undervoltage recovery judgment. When R corresponding to the current battery specification identifier and fan load identifier is missing or the record verification fails, R in the safety parameter group is called. When the number of consecutively obtained stable sampling frames reaches R, R stable sampling frames are written to the load voltage dataset. The load voltage dataset includes at least the battery terminal voltage detection value, PWM cycle identifier, sampling frame number, PWM phase position, current duty cycle gear, current speed limit gear, motor current detection value, target sampling window identifier, and sampling phase status identifier.

[0046] This implementation scheme can improve the data stability and source reliability of the on-load voltage dataset, providing a continuous and stable sampling basis for reliable on-load voltage generation, voltage warning threshold comparison, undervoltage protection threshold comparison, and undervoltage recovery threshold comparison, reducing the risk of false speed reduction, false shutdown, and false recovery caused by instantaneous voltage jumps, PWM phase locking, or erroneous writing of disturbance frames.

[0047] Specifically, the process of generating a reliable on-load voltage based on the on-load voltage dataset is as follows: Based on the load voltage dataset, when the voltage sampling frame is within the target sampling window, and the current PWM cycle is not marked as an unavailable sampling cycle, and the voltage sampling frame does not carry any identifier from the disturbance frame, and the current PWM cycle does not generate a sampling phase lock identifier, the voltage sampling frame is marked as a candidate valid voltage sampling frame; the previous valid voltage sampling frame is the latest sampling frame that has passed the drive response consistency check and participated in the generation of trusted load voltage before the current voltage sampling frame; when the drive response consistency check is performed for the first time, the latest stable sampling frame before the current voltage sampling frame is used as the previous valid voltage sampling frame; the duty cycle value corresponding to the current duty cycle gear comes from the duty cycle gear table in the storage module, and the maximum allowable speed corresponding to the current speed limit gear comes from the speed limit gear table in the storage module; when If the current duty cycle value is greater than the duty cycle value corresponding to the previous effective voltage sampling frame, or if the current maximum allowable speed is greater than the maximum allowable speed corresponding to the previous effective voltage sampling frame, the current drive state is recorded as the drive output increase state. In the drive output increase state, if the current battery terminal voltage detection value is not higher than the battery terminal voltage detection value of the previous effective voltage sampling frame, and the absolute value of the difference between the battery terminal voltage detection value of the previous effective voltage sampling frame and the current battery terminal voltage detection value is not greater than the voltage fluctuation threshold, and the current motor current detection value is not lower than the motor current detection value of the previous effective voltage sampling frame, and the absolute value of the difference between the current motor current detection value and the motor current detection value of the previous effective voltage sampling frame is not greater than the current fluctuation threshold, the current candidate effective voltage sampling frame is determined to have passed the drive response consistency check.

[0048] If the current duty cycle value is less than the duty cycle value of the previous effective voltage sampling frame, or the current maximum allowable speed is less than the maximum allowable speed of the previous effective voltage sampling frame, then the current drive state is recorded as the drive output reduction state. In the drive output reduction state, if the current battery terminal voltage detection value is not lower than the battery terminal voltage detection value of the previous effective voltage sampling frame, and the absolute value of the difference between the current battery terminal voltage detection value and the battery terminal voltage detection value of the previous effective voltage sampling frame is not greater than the voltage fluctuation threshold, and the current motor current detection value is not higher than the motor current detection value of the previous effective voltage sampling frame, and the absolute value of the difference between the motor current detection value of the previous effective voltage sampling frame and the current motor current detection value is not greater than the current fluctuation threshold, then the current candidate effective voltage sampling frame is determined to have passed the drive response consistency check.

[0049] If the current duty cycle value is the same as the duty cycle value of the previous effective voltage sampling frame, and the current maximum allowable speed is the same as the maximum allowable speed of the previous effective voltage sampling frame, then the current drive state is recorded as the drive output holding state. In the drive output holding state, if the absolute value of the difference between the current battery terminal voltage detection value and the battery terminal voltage detection value of the previous effective voltage sampling frame is not greater than the voltage fluctuation threshold, and the absolute value of the difference between the current motor current detection value and the motor current detection value of the previous effective voltage sampling frame is not greater than the current fluctuation threshold, then the current candidate effective voltage sampling frame is determined to have passed the drive response consistency check.

[0050] Candidate valid voltage sampling frames that fail the drive response consistency check are marked as voltage verification frames, and the target sampling window identification and stable sampling frame determination are re-executed in the next PWM cycle; candidate valid voltage sampling frames that pass the drive response consistency check are marked as valid voltage sampling frames; M is the number of reliable load voltage generation frames, in units of sampling frames, which comes from the reliable load voltage generation frame number parameter in the storage module and is consistent with the reliable load voltage generation frame number in the safety parameter group; M is not greater than the number of recording cycles R, and the most recent M valid voltage sampling frames are selected from the load voltage dataset in the order of sampling time; when the M corresponding to the current battery specification identifier and fan load identifier is missing or the record verification fails, M in the safety parameter group is called; and the battery terminal voltage detection values ​​of the M valid voltage sampling frames are arithmetically averaged to generate a reliable load voltage.

[0051] In this implementation scheme, voltage sampling frames inconsistent with fan drive changes are removed. A reliable load voltage is generated using the battery terminal voltage detection values ​​from the most recent M valid voltage sampling frames. This reduces the deviation caused by PWM ripple, MOSFET switching spikes, or sudden changes in motor current in individual sampling frames, making the reliable load voltage more stably reflect the current battery load power supply status. This provides a reliable voltage basis for undervoltage control interval identification, graded speed reduction, undervoltage shutdown, recovery lockout, and soft-start control.

[0052] Specifically, the process of identifying the current undervoltage control range and constructing the undervoltage protection state feature vector is as follows: When all M effective voltage sampling frames originate from the target sampling window, and none of the corresponding PWM cycles carry a disturbance frame identifier or a sampling phase lock identifier, the reliable load voltage is marked as the first reliability level. When a voltage verification frame is reconfirmed and participates in the generation, it is marked as the second reliability level. When the number of effective voltage sampling frames is less than M, no reliable load voltage for recovery restart is generated. The first reliability level corresponds to the sampling reliability status code T1, and the reliable load voltage of the first reliability level is allowed to participate in the comparison of the voltage warning threshold, the undervoltage protection threshold, and the undervoltage recovery threshold. The second reliability level corresponds to the sampling reliability status code T2, and the reliable load voltage of the second reliability level is only allowed to participate in the comparison of the voltage warning threshold and the undervoltage protection threshold, and is not used to trigger recovery restart. When the number of effective voltage sampling frames is less than M, the corresponding sampling reliability status code is T0, and the sampling reliability status code T0 must not trigger recovery restart or update the undervoltage recovery judgment result.

[0053] The current battery power supply status is identified by comparing the trusted load voltage with the voltage warning threshold, undervoltage protection threshold, and undervoltage recovery threshold. The units for these three thresholds are all volts, derived from the threshold parameter table corresponding to the current battery specification and fan load identifier. The voltage warning threshold is greater than the undervoltage recovery threshold, and the undervoltage recovery threshold is greater than the undervoltage protection threshold, creating a recovery hysteresis interval between undervoltage shutdown and recovery restart. If the trusted load voltage is higher than the voltage warning threshold, it is identified as the normal operation interval. If the trusted load voltage is lower than or equal to the voltage warning threshold but higher than the undervoltage protection threshold, it is identified as the warning speed reduction interval. If the trusted load voltage is lower than or equal to the undervoltage protection threshold, it is identified as the undervoltage protection interval. If the fan has stopped and the trusted load voltage has not reached the undervoltage recovery threshold, it is identified as the recovery lockout interval. If the fan has stopped, the trusted load voltage has reached the undervoltage recovery threshold, and the trusted load voltage is at the first trusted level, it is identified as the allowed recovery interval. An undervoltage protection status feature vector is constructed through threshold interval comparison and sampling status coding.

[0054] The normal operation range, warning speed reduction range, undervoltage protection range, recovery lockout range, and allowed recovery range are assigned voltage range status codes C0, C1, C2, C3, and C4, respectively; the first confidence level, the second confidence level, and the state where the number of effective voltage sampling frames has not reached M are assigned sampling confidence status codes T1, T2, and T0, respectively; the drive output increase state, drive output decrease state, and drive output hold state are assigned load control status codes L1, L2, and L0, respectively; the state where the absolute value of the motor current difference is not greater than the current fluctuation threshold is assigned the current stability status code I0, and the state where the absolute value of the motor current difference is greater than the current fluctuation threshold is assigned the current fluctuation status code I1; the sampling phase normal identifier and the sampling phase locked identifier are assigned the sampling phase status codes P0 and P1, respectively; the identifiers without disturbance frames and the identifiers with disturbance frames are assigned the sampling disturbance status codes D0 and D1, respectively; and the undervoltage protection status feature vector is formed by arranging the voltage range status codes, sampling confidence status codes, load control status codes, current stability status codes, sampling phase status codes, and sampling disturbance status codes in a fixed order.

[0055] This implementation scheme enables the control module to select graded speed reduction, undervoltage shutdown, recovery lockout, or allow recovery actions based on a unified status record. This improves the consistency of undervoltage state identification and reduces the risk of false recovery, false shutdown, and repeated start-stop operations caused by insufficient sampling reliability, unclear threshold relationships, or missing status fields.

[0056] Specifically, based on the undervoltage protection state feature vector, the specific process of performing graded speed reduction, undervoltage shutdown, recovery interlocking, and soft start control is as follows: Extract the undervoltage protection status feature vector. If the current undervoltage control interval is within the normal operation interval, maintain the current fan speed setting and continue to perform drive phase collaborative sampling. If the current undervoltage control interval is within the warning speed reduction interval, retrieve the corresponding target speed limit setting from the voltage sub-interval and speed limit setting correspondence table in the storage module based on the voltage sub-interval where the trusted load voltage is located. The voltage sub-interval is formed by dividing the voltage range from the voltage warning threshold to the undervoltage protection threshold. Each voltage sub-interval corresponds to a target speed limit setting, and the target speed limit setting corresponding to the voltage sub-interval closer to the undervoltage protection threshold is lower than the target speed limit setting corresponding to the voltage sub-interval closer to the voltage warning threshold. The voltage sub-interval and speed limit setting correspond to... The speed limit table is derived from the threshold parameter group corresponding to the current battery specification identifier and fan load identifier, and is stored in the storage module. The corresponding target speed limit is retrieved from the speed limit table in the storage module, and a graded speed reduction command is output to the PWM drive module, so that the fan speed is reduced from the current speed level according to the order of adjacent levels in the speed limit table. After each speed regulation cycle, the speed level is reduced by one level until the current speed level matches the target speed limit level, at which point the reduction stops. If the current undervoltage control range is the undervoltage protection range, an undervoltage shutdown command is output to the PWM drive module to stop the fan motor and mark the current state as undervoltage shutdown state. It is forbidden to directly judge the recovery based on the voltage rebound value at the moment of shutdown. If the current undervoltage control interval is a recovery lockout interval, the fan remains off, and shutdown recovery sampling continues. The shutdown recovery sampling involves collecting battery voltage and motor current detection values ​​according to the recovery sampling cycle while the fan drive module remains off, and marking the sampling frame as a shutdown recovery sampling frame. The shutdown recovery sampling frame update does not rely on the MOSFET turn-on edge, MOSFET turn-off edge, or PWM duty cycle, and does not perform target sampling window identification. When consecutive shutdown recovery sampling frames that reach the required recovery sampling frame number do not carry a sampling phase lockout flag, and the battery voltage detection values ​​all reach the undervoltage recovery threshold, a reliable recovery voltage is generated based on the shutdown recovery sampling frames, and this reliable recovery voltage is used as the allowable recovery interval. Judgment criteria: candidate sampling window identification and reliable load voltage generation; if the current undervoltage control range is an allowable recovery range, the recovery lockout is released, and the recovery start speed range is retrieved from the recovery start speed range table in the storage module according to the range where the current reliable load voltage is located or the recovery voltage range where the reliable recovery voltage is located; wherein, the recovery start speed range table includes the recovery voltage range above the undervoltage recovery threshold and the corresponding start speed range, the recovery voltage range closer to the undervoltage recovery threshold corresponds to a lower start speed range, and the recovery voltage range corresponds to a higher start speed range as the voltage increases; the recovery start speed range table is derived from the threshold parameter group corresponding to the current battery specification identifier and fan load identifier, and a soft start command is output to the PWM drive module.

[0057] like Figure 5 The chart shows a comparison of misjudgments between the standard sampling method and the target window sampling method. The horizontal axis represents different anomalies or sampling problem types, and the vertical axis represents the number of statistical occurrences, comparing the differences between the standard sampling method, the target window sampling method of this solution, and the method that reduces the number of occurrences. The chart shows that the standard sampling method has a high number of statistical occurrences in areas such as false alarm triggering, false protection triggering, false recovery judgment, frequent start-stop, phase locking, and invalid sampling. Frequent start-stop has the highest number of occurrences, indicating that the standard sampling method is easily affected by PWM ripple, MOSFET switching edges, and sudden changes in motor current, causing the sampled values ​​to deviate from the stable load voltage, thus resulting in unstable undervoltage judgment.

[0058] After adopting the target window sampling method, the number of various anomalies decreased significantly. This is because this scheme first identifies conduction edge disturbance frames, turn-off edge disturbance frames, duty cycle transition disturbance frames, current disturbance frames, and voltage disturbance frames. Then, it determines the target sampling window from the remaining sampling frames, ensuring that the voltage sampling frames participating in the threshold comparison avoid the PWM switching disturbance range. As a result, the comparison results of the voltage warning threshold, undervoltage protection threshold, and undervoltage recovery threshold are more stable, reducing false warning triggers, false protection triggers, and false recovery judgments.

[0059] In this implementation scheme, a soft start is achieved by matching a lower starting speed to the restored starting speed gear table, thereby reducing the instantaneous current surge during startup. This reduces false alarms, false protection triggers, misjudgments during recovery, and frequent start-stop cycles during low battery phases, improving the operational continuity, recovery stability, and battery protection reliability of the battery-powered fan under undervoltage critical conditions.

[0060] Specifically, the process for generating an undervoltage control tag is as follows: The control action type, battery specification identifier, fan load identifier, PWM phase position, target sampling window position, and reliable load voltage are written into the same undervoltage control tag. The undervoltage control tag also includes disturbance frame type, undervoltage control interval, reliability level, control action trigger time, and tag verification code. The tag verification code is generated by the control module based on the fields in the undervoltage control tag and is used for record integrity verification after power-on. When the same PWM phase position experiences an undervoltage shutdown within the statistical period but fails to reach the undervoltage recovery threshold before generating a recovery start command, it is marked as a recovery false trigger. The statistical period is a preset number of PWM cycles. The period is derived from the statistical period parameter in the storage module and is consistent with the statistical period in the safety parameter group; the statistical period starts from the first PWM period after the undervoltage shutdown command is output and ends when a preset number of PWM periods are reached; when the reliable load voltage falls below or equals the undervoltage protection threshold again within the continuous review period after soft start, it is marked as undervoltage again after soft start. The continuous review period is a preset number of PWM periods continuously read after the soft start command is output, derived from the continuous review period parameter in the storage module and consistent with the continuous review period in the safety parameter group; within the continuous review period, according to claim 6 The reliable load voltage generation method is verified by sampling, and the number of consecutive verification cycles is not less than the number of reliable load voltage generation frames M and not greater than the number of stable sampling record cycles R. The corresponding PWM phase position is written into the phase avoidance record. The phase avoidance record includes the PWM phase position, target sampling window position, disturbance frame type, undervoltage control tag, number of recovery false triggers, number of undervoltage re-emergences after soft start, applicable battery specification identifier, applicable fan load identifier, record writing time, and record verification code. The validity period of the phase avoidance record is calculated based on the number of statistical cycles. When the phase avoidance record is within a consecutive preset number of statistical cycles... If the recovery from a false trigger or the undervoltage occurs again after a soft start, the control module lowers the priority of calling the phase avoidance record; writes the phase avoidance record to the non-volatile storage module; after power-on, it checks the current battery specification identifier and the current fan load identifier. If they match and the record is complete, it continues to use the record and avoids the PWM phase position in the phase avoidance record when selecting the target sampling window; if it cannot be completely avoided, it prioritizes the PWM phase position with fewer false triggers and fewer undervoltage occurrences after a soft start; if the check is inconsistent, the record is missing, or the record verification fails, it calls the safety parameter group and re-executes the target sampling window identification.

[0061] In this implementation scheme, phase avoidance records are only used in target sampling window selection when parameters match and verification passes, preventing erroneous records from affecting sampling. This reduces the likelihood of abnormal PWM phase positions being repeatedly selected as sampling positions, improves the stability of target sampling window selection and the traceability of undervoltage control tags, and reduces the probability of false triggering during recovery, re-undervoltage after soft start, and repeated start-stop cycles during low battery phases.

[0062] Specifically, the second aspect of the present invention provides a multi-threshold graded undervoltage protection control device for a battery-powered fan, applied to a multi-threshold graded undervoltage protection control method for a battery-powered fan, comprising: a voltage detection module connected to the battery output terminal, used to collect the battery terminal voltage detection value and the motor current detection value, and output the collected signals to a control module after voltage division sampling and filtering; a control module connected to the voltage detection module, the fan drive module and the storage module respectively, used to read the battery terminal voltage detection value, the motor current detection value, the PWM period identifier, the PWM phase position, the MOSFET switch edge identifier, the current duty cycle level, the current speed limit level, the battery specification identifier and the fan load identifier, and based on the fan undervoltage protection response data, to perform disturbance frame identification, target sampling window determination, sampling phase lock determination, load voltage dataset construction, reliable load voltage generation and multi-threshold interval judgment; and a fan drive module connected to the control module and the fan motor respectively, used to receive the input from the control module. The system outputs graded speed reduction commands, undervoltage shutdown commands, hold shutdown commands, and soft-start commands, and controls the switching state of MOSFETs via PWM signals to adjust the fan motor speed, stop the fan motor, or restart the fan motor; the storage module, connected to the control module, is a non-volatile storage unit used to store voltage warning thresholds, undervoltage protection thresholds, undervoltage recovery thresholds, speed limit gear tables, recovery start speed gear tables, speed regulation cycles, battery specification identifiers, fan load identifiers, disturbance spread frame counts, phase lock determination cycle counts, reliable load voltage generation frame counts, stable sampling record counts, stable window frame counts, edge interval frames, current mutation thresholds, voltage mutation thresholds, voltage fluctuation thresholds, current fluctuation thresholds, statistical cycles, continuous verification cycles, phase avoidance records, target sampling window records, and safety parameter groups; the power supply module, connected to the battery, voltage detection module, control module, fan drive module, and storage module, is used to convert the battery output voltage into the operating voltage required by each module.

[0063] This implementation improves the device's ability to suppress PWM ripple, MOSFET switching transients, and sudden changes in motor current, reduces false alarms, false shutdowns due to voltage sampling deviations, and false restarts during recovery, enabling battery-powered fans to have more stable speed control, undervoltage protection, and recovery start-up performance under low power conditions.

[0064] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0065] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A multi-threshold hierarchical undervoltage protection control method for a battery-powered fan, characterized in that, Includes the following steps: S1. Obtain fan undervoltage protection response data, and perform sampling synchronization, sampling frame marking and scale unification to obtain fan undervoltage protection response dataset; S2, based on the fan undervoltage protection response dataset, identifies disturbance frames and candidate sampling windows, generates sampling phase lock-in identifiers, and constructs a load voltage dataset; S3. Based on the on-load voltage dataset, generate a reliable on-load voltage, identify the current undervoltage control range, and construct an undervoltage protection state feature vector. S4, based on the undervoltage protection state feature vector, performs graded speed reduction, undervoltage shutdown, recovery interlock and soft start control, and generates undervoltage control tags.

2. The multi-threshold hierarchical undervoltage protection control method for a battery-powered fan according to claim 1, characterized in that: The specific process of acquiring fan undervoltage protection response data, performing sampling synchronization, sampling frame marking and scaling to obtain the fan undervoltage protection response dataset is as follows: Data is collected during the operation of the battery-powered fan to obtain fan undervoltage protection response data. The fan undervoltage protection response data includes battery terminal voltage detection value, sampling trigger time, PWM cycle identifier, PWM phase position, MOSFET switch edge identifier, current duty cycle level, current speed limit level, motor current detection value, current battery specification identifier, safety parameter group, and fan load identifier. Using the PWM cycle identifier as the synchronization reference for voltage sampling, the cycle number is recorded at the beginning of each PWM cycle. When acquiring the battery terminal voltage detection value within the same cycle, the voltage detection value, the corresponding PWM cycle number, PWM phase position, MOSFET switching edge identifier, and current speed limit gear are written into the same sampling frame. The written sampling frame is the voltage sampling frame. When the voltage sampling frame is within the sampling frame containing the MOSFET turn-on or turn-off edge and the N sampling frames before and after it, the voltage sampling frame is marked as a disturbance sampling frame. When the voltage sampling frame is in the period when the MOSFET switching edge identifier has not switched, the voltage sampling frame is marked as a stable sampling frame. When the PWM phase position cannot be determined, the voltage sampling frame is marked as a frame to be resampled and is resampled in the next sampling cycle; The battery terminal voltage detection value, current duty cycle gear, motor current detection value, and current speed limit gear in the stable sampling frame are subjected to amplitude normalization and scale unification processing to generate a fan undervoltage protection response dataset.

3. The multi-threshold hierarchical undervoltage protection control method for a battery-powered fan according to claim 1, characterized in that: The specific process of identifying disturbance frames and candidate sampling windows based on the fan undervoltage protection response dataset is as follows: Based on the fan undervoltage protection response dataset, the sampling frames are grouped according to the PWM cycle identifier, and each group of sampling frames corresponds to one PWM output cycle. Taking the sampling frame where the MOSFET is turned on as the reference, the sampling frame and the N sampling frames before and after it are marked as the turn-on edge disturbance frame. Taking the sampling frame where the MOSFET is turned off as the reference, the sampling frame and the N sampling frames before and after it are marked as the turn-off edge disturbance frame. Based on the sampling frame where the PWM duty cycle is updated, the sampling frame and the following N sampling frames are marked as duty cycle transition disturbance frames. The difference between the motor current detection values ​​of adjacent sampling frames in the same PWM cycle is compared. If the absolute value of the difference between the motor current of two adjacent frames is greater than the current change threshold, the next sampling frame and the following N sampling frames are marked as current disturbance frames. The difference between the battery terminal voltage detection values ​​of adjacent sampling frames in the same PWM cycle is compared. If the absolute value of the difference between the battery terminal voltage of two adjacent frames is greater than the voltage change threshold, the next sampling frame and the following N sampling frames are marked as voltage disturbance frames. After removing the five types of disturbance frames, a sampling frame segment is searched from the remaining sampling frames in the same PWM cycle. When the number of sampling frames in the sampling frame segment is not less than the number of stable window frames, and the interval between the starting sampling frame of the sampling frame segment and the sampling frame of the MOSFET switching edge is not less than the edge interval frame, the sampling frame segment is marked as a candidate sampling window. When only one candidate sampling window is identified in the same PWM cycle, the candidate sampling window is used as the target sampling window. When there is no candidate sampling window in the same PWM cycle, the PWM cycle is marked as an unusable sampling cycle, and the candidate sampling window is re-identified after the voltage sampling trigger position is adjusted in the next round.

4. The multi-threshold hierarchical undervoltage protection control method for a battery-powered fan according to claim 1, characterized in that: The specific process for generating the sampling phase lock identifier is as follows: When the voltage sampling trigger frames within K consecutive PWM cycles do not fall into the target sampling window and all fall into the same type of disturbance frame, it is determined that the voltage sampling trigger position and the PWM cycle form a fixed phase coupling, a sampling phase lock flag is generated, and the sampling frame number range and disturbance frame type corresponding to the phase lock are recorded; in the next PWM cycle, the voltage sampling trigger position is adjusted so that the voltage sampling trigger position moves into the target sampling window; When the voltage sampling trigger frames within K consecutive PWM cycles all fall into the target sampling window, the corresponding PWM cycles are not marked as unavailable sampling cycles, and the voltage sampling trigger frames do not carry disturbance frame identifiers, it is determined that the voltage sampling trigger position has not formed a fixed phase coupling, and a normal sampling phase identifier is generated.

5. The multi-threshold hierarchical undervoltage protection control method for a battery-powered fan according to claim 1, characterized in that: The specific process for constructing the on-load voltage dataset is as follows: Write determination is performed on the voltage sampling frames within each PWM cycle. If the current PWM cycle is marked as an unavailable sampling cycle, or the current voltage sampling frame carries any identifier from the disturbance frame, or the current PWM cycle has a sampling phase lock identifier, then writing the voltage sampling frame to the load voltage dataset is prohibited, and the voltage sampling frame is written to the disturbance recording area. When the current voltage sampling frame is within the target sampling window, is not marked as an unavailable sampling cycle, does not carry a disturbance frame identifier, and does not have a sampling phase lock identifier, the battery terminal voltage detection value of the current voltage sampling frame and the previous stable sampling frame is read. When the absolute value of the difference between the two is not greater than the voltage fluctuation threshold, the current voltage sampling frame is marked as a stable sampling frame. When the absolute value of the difference between the two is greater than the voltage fluctuation threshold, the current voltage sampling frame is marked as a voltage verification frame, and the target sampling window identification and sampling frame write determination are re-executed in the next PWM cycle. Starting from the PWM cycle in which the first stable sampling frame is obtained, stable sampling frames in subsequent PWM cycles are read continuously according to the number of recording cycles R. When the number of consecutively obtained stable sampling frames reaches R, write R stable sampling frames into the on-load voltage dataset.

6. The multi-threshold hierarchical undervoltage protection control method for a battery-powered fan according to claim 1, characterized in that: The specific process for generating a reliable on-load voltage based on the on-load voltage dataset is as follows: Based on the on-load voltage dataset, when the voltage sampling frame is within the target sampling window, and the current PWM cycle is not marked as an unavailable sampling cycle, and the voltage sampling frame does not carry any identifier from the disturbance frame, and the current PWM cycle does not generate a sampling phase lock identifier, the voltage sampling frame is marked as a candidate valid voltage sampling frame. When the current duty cycle setting or the current speed limit setting is higher than the corresponding setting of the previous effective voltage sampling frame, the current drive state is recorded as the drive output increase state. In the drive output increase state, when the current battery terminal voltage detection value is not higher than the sum of the battery terminal voltage detection value and the voltage fluctuation threshold of the previous effective voltage sampling frame, and the current motor current detection value is not lower than the difference between the motor current detection value and the current fluctuation threshold of the previous effective voltage sampling frame, the current candidate effective voltage sampling frame is determined to have passed the drive response consistency verification. Candidate effective voltage sampling frames that fail the drive response consistency verification are marked as voltage verification frames, and vice versa. The battery terminal voltage detection values ​​of the M effective voltage sampling frames are then arithmetically averaged to generate a reliable load voltage.

7. The multi-threshold hierarchical undervoltage protection control method for a battery-powered fan according to claim 1, characterized in that: The specific process of identifying the current undervoltage control interval and constructing the undervoltage protection state feature vector is as follows: When all M effective voltage sampling frames originate from the target sampling window, and none of the corresponding PWM cycles carry a disturbance frame identifier or a sampling phase lock identifier, the reliable load voltage is marked as the first reliability level; when a voltage verification frame is reconfirmed and participates in the generation, it is marked as the second reliability level. When the number of effective voltage sampling frames does not reach M, a reliable load voltage for recovery and restart is not generated; the reliable load voltage is compared with the voltage warning threshold, undervoltage protection threshold and undervoltage recovery threshold respectively to identify the current battery power supply status. If the reliable load voltage is higher than the voltage warning threshold, it is identified as being in the normal operating range; If the reliable load voltage is lower than or equal to the voltage warning threshold and higher than the undervoltage protection threshold, it is identified as a warning speed reduction zone; If the reliable load voltage is lower than or equal to the undervoltage protection threshold, it is identified as an undervoltage protection zone; if the fan has stopped and the reliable load voltage has not reached the undervoltage recovery threshold, it is identified as a recovery lockout zone. If the fan has stopped, the trusted load voltage has reached the undervoltage recovery threshold, and the trusted load voltage is at the first level of trust, then it is identified as an allowable recovery range. The undervoltage protection state feature vector is constructed by comparing threshold intervals and assigning codes to the sampling state.

8. The multi-threshold hierarchical undervoltage protection control method for a battery-powered fan according to claim 1, characterized in that: The specific process of performing graded speed reduction, undervoltage shutdown, recovery interlocking, and soft start control based on the undervoltage protection state feature vector is as follows: Extract the undervoltage protection status feature vector. If the current undervoltage control range is within the normal operating range, maintain the current fan speed and continue to perform drive phase collaborative sampling. If the current undervoltage control range is within the warning speed reduction range, retrieve the corresponding target speed limit from the speed limit table in the storage module based on the voltage sub-range where the reliable load voltage is located, and output a graded speed reduction command to the PWM drive module. This causes the fan speed to decrease from the current speed level according to the order of adjacent speed limits in the speed limit table. After each speed control cycle, decrease the speed by one level until the current speed level matches the target speed limit. If the current undervoltage control range is within the undervoltage protection range, an undervoltage shutdown command is output to the PWM drive module to stop the fan motor and mark the current state as undervoltage shutdown state, prohibiting direct recovery judgment based on the voltage rebound value at the moment of shutdown; if the current undervoltage control range is within the recovery lockout range, the fan remains in the shutdown state, and candidate sampling window identification and reliable load voltage generation continue; if the current undervoltage control range is within the allowable recovery range, the recovery lockout is released, and the recovery start speed gear is matched according to the range where the current reliable load voltage is located, and a soft start command is output to the PWM drive module.

9. A multi-threshold hierarchical undervoltage protection control method for a battery-powered fan according to claim 1, characterized in that: The specific process for generating the undervoltage control tag is as follows: The control action type, battery specification identifier, fan load identifier, PWM phase position, target sampling window position, and reliable load voltage are written into the same undervoltage control tag. When the same PWM phase position generates a recovery start command before reaching the undervoltage recovery threshold after an undervoltage shutdown within the statistical period, it is marked as a recovery false trigger. When the reliable load voltage falls below or equals the undervoltage protection threshold again within the continuous verification period after a soft start, it is marked as an undervoltage recurrence after a soft start, and the corresponding PWM phase position is written into the phase avoidance record. The phase avoidance record is written into the non-volatile storage module. After powering on again, check the current battery specification identifier and the current fan load identifier. If they match and the record is complete, continue using it. If they do not match, the record is missing, or the record verification fails, call the safety parameter group and re-execute the target sampling window identification.

10. A multi-threshold hierarchical undervoltage protection control device for a battery-powered fan, employing the multi-threshold hierarchical undervoltage protection control method for a battery-powered fan as described in any one of claims 1-9, characterized in that, include: The voltage detection module is connected to the battery output terminal to collect the battery terminal voltage detection value and the motor current detection value. After performing voltage division sampling and filtering on the collected signals, it outputs them to the control module. The control module is connected to the voltage detection module, fan drive module and storage module respectively. It is used to read the battery terminal voltage detection value, motor current detection value, PWM period identifier, PWM phase position, MOSFET switch edge identifier, current duty cycle level, current speed limit level, battery specification identifier and fan load identifier. Based on the fan undervoltage protection response data, it performs disturbance frame identification, target sampling window determination, sampling phase lock determination, load voltage dataset construction, reliable load voltage generation and multi-threshold interval judgment. The fan drive module is connected to the control module and the fan motor respectively. It is used to receive the graded speed reduction command, undervoltage shutdown command, hold shutdown command and soft start command output by the control module, and control the switching state of the MOSFET through the PWM signal to adjust the fan motor speed, stop the fan motor or restart the fan motor. The storage module, connected to the control module, is a non-volatile storage unit used to store voltage warning thresholds, undervoltage protection thresholds, undervoltage recovery thresholds, speed limit gear tables, recovery start speed gear tables, speed regulation cycles, battery specification identifiers, fan load identifiers, disturbance spread frame counts, phase lock determination cycle counts, reliable load voltage generation frame counts, stable sampling record counts, stable window frame counts, edge interval frames, current mutation thresholds, voltage mutation thresholds, voltage fluctuation thresholds, current fluctuation thresholds, statistical cycles, continuous review cycles, phase avoidance records, target sampling window records, and safety parameter groups. The power module is connected to the battery, voltage detection module, control module, fan drive module, and storage module, respectively, and is used to convert the battery output voltage into the operating voltage required by each module.

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