Flying capacitor voltage control method and device for flying capacitor three-level buck circuit

Abstract

This application relates to the field of power electronic control technology, and provides a method and apparatus for controlling the flying capacitor voltage in a three-level buck circuit with a flying capacitor. In response to the circuit entering a light-load condition, an initialization operation is performed, clearing the duty cycle adjustment. Based on the current charging and discharging state of the circuit, a corresponding control state is entered, and a PI loop is used to control the flying capacitor voltage. In the control state, the control direction is determined based on the change in the flying capacitor voltage error. If the control direction is correct, the current control state is maintained and the PI loop parameters are adjusted. If the control direction is reversed, a disturbance-suppression control state is entered, the duty cycle adjustment is linearly reduced to zero, and then the opposite control state is switched. This solves the technical problem of traditional control methods failing under light-load conditions, significantly expands the stable operating range of the three-level buck circuit with a flying capacitor, and improves the reliability of the system under wide load conditions.

Description

Technical Field

[0001] This application relates to the field of power electronic control technology, specifically to a method and device for controlling the voltage of a flying capacitor in a three-level buck circuit. Background Technology

[0002] like Figure 1 As shown, the flying capacitor three-level buck converter, as an advanced DC-DC converter topology, has been widely used in new energy storage, electric vehicle charging piles, and high-performance power supplies due to its advantages such as low voltage stress on switching devices, small output current ripple, and fast dynamic response. This topology achieves voltage clamping through the charging and discharging of the flying capacitor during the switching cycle, ensuring that the voltage across the switching transistors is only half of the input bus voltage. This allows for high-voltage, high-power conversion using lower voltage-level devices. Under normal operating conditions, when the duty cycles of the first and third switching transistors are equal, the voltage across the flying capacitor naturally balances to half of the input bus voltage. This characteristic is a fundamental condition for stable circuit operation.

[0003] However, in practical applications, due to non-ideal factors such as the on-state voltage drop of the switching transistors, drive signal delay, and equivalent series resistance of the capacitors, the actual duty cycle output to each switching transistor will deviate, causing the flying capacitor voltage to deviate from the ideal median value. To solve this problem, a dual closed-loop control structure is commonly used in engineering practice. The outer loop controls the output voltage to determine the reference duty cycle, while the inner loop detects the flying capacitor voltage and outputs a fine-tuning amount to compensate for the duty cycle of each transistor. This control strategy can effectively maintain the balance of the flying capacitor voltage under medium to heavy load conditions, keeping the circuit operating in a stable state.

[0004] The aforementioned conventional control method has a fundamental limitation: it fails to consider the special characteristics of circuit operation under light load or no-load conditions. Under light load conditions, the average value of the inductor current is very small, while the proportion of its ripple current amplitude in the total current increases significantly. This causes the inductor current to approach zero or even reverse during certain periods of the switching cycle. When the inductor current flows in reverse, the charging and discharging direction of the flying capacitor changes accordingly, and the originally correct duty cycle adjustment direction becomes the wrong direction, completely reversing the conventional control logic. At this time, the adjustment effect of the PI loop not only fails to bring the flying capacitor voltage closer to the median value, but also forms positive feedback, accelerating the divergence of the flying capacitor voltage towards the input bus voltage or zero potential, ultimately leading to circuit malfunction or damage.

[0005] Therefore, there is an urgent need for a new control method that can identify and adapt to changes in control direction under light load conditions, so as to achieve reliable control of the flying capacitor voltage across the full load range. Summary of the Invention

[0006] In view of this, embodiments of this application provide a method and apparatus for controlling the voltage of a flying capacitor in a three-level buck circuit, in order to solve the problem that traditional control methods fail due to reverse inductor current under light load conditions.

[0007] The first aspect of this application provides a method for controlling the voltage of a flying capacitor in a three-level buck circuit with a flying capacitor, comprising: In response to the circuit entering a light-load condition, an initialization operation is performed to clear the duty cycle adjustment. Based on the current charging and discharging state of the circuit, it enters the corresponding regulation state and uses a PI loop to control the voltage of the flying capacitor. In the aforementioned control state, the correctness of the control direction is determined based on the change in the flying capacitor voltage error. If the control direction is correct, the current control state is maintained and the PI loop parameters are adjusted; if the control direction is reversed, the disturbance reduction control state is entered, the duty cycle adjustment is linearly reduced to zero, and then the opposite control state is switched.

[0008] A second aspect of this application provides a flying capacitor voltage control device for a flying capacitor three-level buck circuit, comprising: The initialization module is used to perform initialization operations and clear the duty cycle adjustment in response to the circuit entering a light load condition. The state determination module is used to enter the corresponding control state according to the current charging and discharging state of the circuit, and uses a PI loop to control the voltage of the flying capacitor. The direction detection module is used to determine whether the control direction is correct based on the change in the voltage error of the flying capacitor under the control state. The control execution module is used to maintain the current control state and adjust the PI loop parameters when the control direction is correct. When the control direction is reversed, it enters the disturbance reduction control state, linearly reduces the duty cycle adjustment amount to zero, and then switches to the opposite control state.

[0009] The flying capacitor voltage control method for a three-level buck circuit with a flying capacitor provided in the first aspect of this application effectively eliminates interference from historical adjustment states by performing initialization and clearing the duty cycle adjustment when entering a light-load condition. By selecting the corresponding control state based on the charging and discharging state and using a slower PI loop for trial control, the control effect can be observed without causing drastic system fluctuations. By monitoring the changing trend of the flying capacitor voltage error to determine whether the control direction is correct, adaptive identification of inductor current direction changes under light-load conditions is achieved. When a reverse control direction is detected, the disturbance-suppressing control state smoothly transitions to the opposite control state, avoiding voltage surges during state switching. This method solves the technical problem of traditional control methods failing under light-load conditions, significantly expands the stable operating range of the three-level buck circuit with a flying capacitor, and improves the reliability of the system under wide load conditions.

[0010] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here. Attached Figure Description

[0011] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0012] Figure 1 This is a schematic diagram of the topology of a flying capacitor three-level buck circuit provided in an embodiment of this application; Figure 2 This is a schematic flowchart of a method for controlling the voltage of a flying capacitor in a three-level buck circuit with a flying capacitor according to an embodiment of this application. Figure 3 This is a schematic flowchart of a method for controlling the voltage of a flying capacitor in a three-level buck circuit with a flying capacitor, provided in another embodiment of this application. Figure 4 This is a schematic flowchart of a method for controlling the voltage of a flying capacitor in a three-level buck circuit with a flying capacitor, provided in another embodiment of this application. Figure 5 This is a schematic diagram of the flying capacitor voltage control device of the flying capacitor three-level buck circuit provided in the embodiments of this application. Detailed Implementation

[0013] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0014] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0015] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0016] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0017] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0018] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0019] like Figure 2As shown, the flying capacitor voltage control method for the flying capacitor three-level buck circuit provided in this application embodiment includes the following steps S101 to S104: Step S101: In response to the circuit entering a light load condition, perform an initialization operation and clear the duty cycle adjustment.

[0020] Step S102: Based on the current charging and discharging state of the circuit, enter the corresponding control state and use a PI loop to control the voltage of the flying capacitor.

[0021] Step S103: Under the control state, determine whether the control direction is correct based on the change of the flying capacitor voltage error; wherein, the flying capacitor voltage error is the difference between half of the bus voltage and the flying capacitor voltage.

[0022] Step S104: If the control direction is correct, maintain the current control state and adjust the PI loop parameters; if the control direction is reversed, enter the disturbance reduction control state, linearly reduce the duty cycle adjustment amount to zero, and then switch to the opposite control state.

[0023] In applications, responding to the circuit entering a light-load condition and performing an initialization operation to clear the duty cycle adjustment means that when the control system detects that the circuit load current has decreased below the light-load threshold, it triggers the start-up process of the light-load control mode. A light-load condition refers to a situation where the circuit output current is small, causing a significant increase in the ripple component of the inductor current during the switching cycle, and potentially even resulting in the inductor current crossing zero or reversing. The core purpose of the initialization operation is to eliminate the historical value of the duty cycle adjustment ΔD accumulated by the PI controller before entering the light-load mode, allowing the control system to start executing the light-load control algorithm from a defined initial state. Clearing the duty cycle adjustment means setting the first switching transistor... With the third switching transistor The duty cycle difference is adjusted to zero, that is, let = =D, where D is the reference duty cycle of the outer loop voltage control output. This operation is necessary because the accumulated regulation in the normal control mode may be opposite to the actual required regulation direction in the light load mode. If it is not cleared, it will lead to an incorrect judgment of the control direction in the initial stage.

[0024] In applications, based on the current charging and discharging state of the circuit, the system enters the corresponding control state and uses a PI loop to control the flying capacitor voltage. This means the control system selects the appropriate control strategy based on the current flow direction of the inductor current. The charging state refers to current flowing from the input bus to the output terminal; in this state, the circuit operates in energy transfer mode. The discharging state refers to current feeding back from the output terminal to the input side, commonly seen in energy storage applications with bidirectional energy flow capabilities or during load shedding transients. Entering the corresponding control state means the system will select different PI loop parameters or adjustment logic depending on the charging and discharging direction. A PI loop is a proportional-integral controller. Its input is the flying capacitor voltage error, which is half the bus voltage minus the measured flying capacitor voltage. The output is the duty cycle adjustment ΔD. This adjustment is used to fine-tune the duty cycle of the first and third switching transistors, making the flying capacitor voltage approach the median of the bus voltage. In light-load mode, the PI loop typically uses conservative parameter settings to reduce the adjustment speed, facilitating subsequent observation of the control effect and judgment of the correctness of the control direction.

[0025] In applications, determining the correctness of the control direction based on the change in the flying capacitor voltage error under controlled conditions means that the system observes the evolution trend of the flying capacitor voltage error over a period of time to confirm whether the currently adopted control strategy can bring the error to convergence. The flying capacitor voltage error is defined as ΔE = 0.5 × - ,in For the input bus voltage, This represents the measured voltage across the flying capacitor. A positive error indicates the flying capacitor voltage is below the median; a negative error indicates the flying capacitor voltage is above the median. Determining the correctness of the control direction essentially involves checking whether the PI loop output reduces the absolute value of the error. Under normal load conditions, the determined charging / discharging direction corresponds to the determined control polarity, and the PI loop converges correctly. However, under light load conditions, because the inductor current may reverse during the switching cycle, the actual charging / discharging direction may be opposite to the macroscopically determined direction. In this case, the originally correct control polarity becomes the incorrect polarity, causing the absolute value of the error to increase instead of decrease, exhibiting a divergent trend. This judgment step is the core innovation of this method, enabling the system to identify and autonomously correct control direction errors.

[0026] In application, if the control direction is correct, the current control state is maintained and the PI loop parameters are adjusted; if the control direction is reversed, a disturbance-suppression control state is entered, and the duty cycle adjustment is linearly reduced to zero before switching to the opposite control state. Correct control direction means that the absolute value of the flying capacitor voltage error decreases during the control process. In this case, the current control state should be maintained, and the PI loop response speed can be appropriately increased to shorten the convergence time. Reverse control direction means that the absolute value of the error increases during the control process, indicating that the current control polarity is opposite to the actual requirement. In this situation, the control state cannot be switched immediately because the PI loop has already accumulated a certain amount of duty cycle adjustment. A sudden switch would cause a step change in the control output, potentially leading to severe fluctuations in the flying capacitor voltage. Therefore, a disturbance-suppression control state is introduced as a transition, in which the duty cycle adjustment ΔD is linearly and gradually reduced to zero to achieve a smooth transition. After the adjustment reaches zero, the opposite control state is switched to restart the control process. This design ensures the smoothness of the state switching and avoids impacting the circuit.

[0027] The determination of light-load conditions can be achieved by comparing the measured value of the current sensor with a preset threshold. A light-load condition is defined as when the charging current is less than the positive threshold or the absolute value of the discharging current is less than the absolute value of the negative threshold. Alternatively, a method based on output power estimation can be used, calculating the instantaneous power by multiplying the output voltage and output current. A light-load condition is defined as when the power is lower than a preset percentage of the rated value. The control direction determination can be achieved by comparing the absolute values ​​of the initial error and the current error. The control effect can be directly judged by comparing the magnitude of the absolute values ​​of the errors over a period of time. Alternatively, a method of accumulating error changes can be used, separately summing the upward and downward changes in error, and comparing their magnitudes to determine the overall trend of error change.

[0028] This application's embodiments establish a control framework encompassing three states—initialization, regulation, and disturbance suppression—under light load conditions. By adaptively determining the control direction based on the changing trend of the flying capacitor voltage error, it solves the problem of positive feedback runaway caused by the inability to identify reverse inductor current in traditional control methods. It can automatically identify changes in control polarity caused by changes in inductor current direction under light load conditions without prior calibration or manual intervention. The disturbance suppression regulation state achieves smooth transitions between states, avoiding voltage surges caused by step changes in duty cycle and protecting circuit safety. Even if the initial direction judgment is incorrect, iterative correction eventually achieves stable convergence of the flying capacitor voltage to the bus median, demonstrating strong robustness. No additional hardware detection circuitry is required; it can be implemented on existing control platforms using only software algorithms, resulting in low cost.

[0029] In one embodiment, step S101 includes the following steps S201 to S202: Step S201: Detect the charging and discharging current value of the detection circuit.

[0030] Step S202: When the circuit is in a charging state and the charging current is less than the preset positive threshold, or when the circuit is in a discharging state and the absolute value of the discharging current is less than the absolute value of the preset negative threshold, the circuit is determined to enter a light load condition.

[0031] In applications, the charging and discharging current value of the detection circuit refers to the magnitude and direction of the current flowing through the main power loop of the circuit, measured in real time by a current detection device. The charging and discharging current is the current observed from the input bus side; a positive value indicates a charging state where energy is transferred from the input side to the output side, while a negative value indicates a discharging state where energy is fed back from the output side to the input side. Current detection is typically achieved using Hall effect current sensors, current transformers, or series sampling resistors. Hall effect sensors offer advantages such as fast response and good isolation, making them suitable for high-current applications; the sampling resistor method is inexpensive and highly accurate, but suffers from power loss and common-mode interference issues. The detected current value will serve as the basis for subsequent light-load determination.

[0032] In application, the circuit is determined to enter a light-load condition when it is charging and the charging current is less than a preset positive threshold, or when it is discharging and the absolute value of the discharging current is less than the absolute value of a preset negative threshold. The preset positive threshold is a positive number representing the light-load determination boundary in the charging direction; a typical value is set according to circuit parameters, usually between 3 and 5 amps. The preset negative threshold is a negative number, and its absolute value represents the light-load determination boundary in the discharging direction. When the detected charging current is positive but less than the positive threshold, it indicates that the forward power transmission is low, and the circuit is in a light-load charging state. When the detected discharging current is negative but its absolute value is less than the absolute value of the negative threshold, it indicates that the feedback power is low, and the circuit is in a light-load discharging state. In either case, as long as the condition is met, the circuit is determined to enter a light-load condition, thus triggering the subsequent light-load control process. This method of setting thresholds based on charging and discharging states makes the determination logic more flexible and adaptable to bidirectional operation scenarios.

[0033] Specifically, taking a bidirectional flying capacitor three-level buck converter applied to an energy storage system as an example, the specific process of light load determination is explained. This converter has a rated charging current of 20A and a rated discharging current of -20A, with a set positive threshold of 4A and a negative threshold of -4A. The control system samples the current value every 100 microseconds and calculates the moving average of the most recent 10 samples to filter out high-frequency noise. When the average current is 15A, it is in normal charging condition and does not trigger the light load mode. When the average current drops to 3A, although it is still in positive charging, it is less than the positive threshold of 4A, and the system determines that it has entered the light load condition and starts the light load control algorithm. Similarly, when the average current is -2A, it indicates a low-power discharging state, and its absolute value of 2A is less than the absolute value of the negative threshold of 4A, which is also determined to be a light load condition. This determination mechanism ensures that regardless of whether the circuit is operating in the charging or discharging direction, as long as the power level drops to the light load range, it can promptly identify and switch the control strategy.

[0034] The charging and discharging current can be detected by directly measuring the power circuit current using a Hall current sensor, or indirectly by connecting a milliohm-level sampling resistor in series with the source of the low-side switching transistor. The threshold for light load determination can be set using a fixed constant, pre-set according to circuit design parameters and written into the control program; alternatively, an adaptive threshold can be used, calculating in real-time the critical load value that ensures continuous inductor current based on the input bus voltage and inductor parameters, and using this as the light load determination boundary.

[0035] This application's embodiments determine light-load conditions by detecting the charging and discharging current value and comparing it with a bidirectional threshold. This direct judgment based on current, a physical quantity reflecting load intensity, is more direct and reliable than power estimation-based methods, avoiding interference from voltage fluctuations. The current detection sampling rate can reach microsecond levels, enabling rapid identification of the entry or exit of light-load conditions after load changes, ensuring timely switching of control strategies. Separate positive and negative thresholds are set, making the method applicable to different application scenarios such as unidirectional and bidirectional converters, demonstrating strong versatility.

[0036] In one embodiment, step S102 includes the following steps S301 to S303: Step S301: When the circuit is in the charging state, it enters the positive control state.

[0037] Step S302: When the circuit is in a discharge state, it enters the reverse control state.

[0038] Step S303: Under each control state, the duty cycle adjustment amount ΔD is output through the PI loop to make the first switching transistor... duty cycle With the third switching transistor duty cycle This generates a difference; specifically, when the voltage across the flying capacitor is higher than half the bus voltage, =D+ΔD, =D-ΔD; When the voltage across the flying capacitor is less than half of the bus voltage, =D-ΔD, =D+ΔD.

[0039] In applications, when the circuit is in a charging state, entering the positive regulation state means that when the system detects that the average inductor current is positive, it selects to regulate the flying capacitor voltage according to the control logic of positive energy flow. In the positive regulation state, the charging and discharging of the flying capacitor follows a conventional pattern: when... and When both are simultaneously activated, the input bus passes through... Charge the flying capacitor; when and When both are conducting simultaneously, the flying capacitor passes through... Discharge to the load. Therefore, increase The conduction time may be reduced The on-time of the circuit will cause the voltage across the flyback capacitor to rise, and vice versa. Entering the positive control state means that the PI loop will output the duty cycle adjustment according to this logic.

[0040] In applications, when the circuit is in a discharging state, entering the reverse regulation state means that when the system detects that the average inductor current is negative, it selects to regulate the flying capacitor voltage according to the control logic of reverse energy flow. In the reverse regulation state, due to the change in the direction of the inductor current, the charging and discharging relationship of the flying capacitor is reversed. When the circuit is turned on, the flying capacitor is discharged. When the circuit is on, the flying capacitor is charged. Therefore, in the reverse control state, the duty cycle adjustment of the PI loop output has the opposite polarity on the flying capacitor voltage compared to the forward control state. Entering the reverse control state means that the control system will configure the output polarity of the PI loop according to the logic of reverse energy flow.

[0041] In application, under various control states, the duty cycle adjustment ΔD is output through the PI loop to control the first switching transistor. Duty cycle and third switch The difference in duty cycle is the core method for controlling the flying capacitor voltage. The input of the PI loop is the flying capacitor voltage error ΔE, which is then processed by a proportional circuit. And points process The processed output duty cycle adjustment amount ΔD is then added to the reference duty cycle D to form... and Each has its own actual duty cycle. When the flying capacitor voltage is higher than half of the bus voltage, ΔE is negative. According to the polarity configuration of the PI loop, the output ΔD makes... =D+ΔD increases, =D-ΔD decreases, thereby increasing the discharge time and decreasing the charging time of the flying capacitor, causing the flying capacitor voltage to drop closer to the median. When the flying capacitor voltage is lower than half of the bus voltage, ΔE is positive, and the output ΔD makes... =D-ΔD decreases, As ΔD increases, the charging time increases and the discharging time decreases, causing the flying capacitor voltage to rise closer to the median. This symmetrical adjustment logic ensures that the flying capacitor voltage can converge to the median from any initial state.

[0042] The selection of the control state can be achieved through a direct judgment method based on the current sign: a positive current indicates the positive state, and a negative current indicates the reverse state. Alternatively, a judgment method based on power flow direction can be used, determining the energy flow direction by comparing the input and output power. The PI loop parameters can be tuned using engineering tuning methods, manually adjusting the proportional and integral coefficients based on empirical formulas and system response characteristics. Alternatively, an automatic tuning algorithm can be used, determining the optimal parameters online based on relay feedback or model identification methods.

[0043] This application embodiment enables the flyover capacitor voltage control to adapt to bidirectional energy flow scenarios by selecting the corresponding control state based on the charging and discharging state. The duty cycle adjustment is configured according to the direction of the flyover capacitor voltage deviation via a PI loop output. and The duty cycle difference is used to achieve closed-loop negative feedback control of the flying capacitor voltage. The complex bidirectional control problem is decomposed into two symmetrical control states, reducing algorithm complexity. The PI loop combines the fast response of the proportional term with the steady-state error-free characteristics of the integral term, enabling precise tracking of the flying capacitor voltage midpoint. The limiting design of the duty cycle adjustment ΔD prevents overvoltage of the switching transistor or overcharging / over-discharging of the flying capacitor caused by excessive adjustment.

[0044] In one embodiment, step S103 includes the following steps S401 to S404: Step S401: Record the initial value of the flying capacitor voltage error during the initialization operation. .

[0045] Step S402: After entering the control state, a PI loop with slower parameters is used for control. After a preset control period, the current flying capacitor voltage error value is obtained. .

[0046] Step S403, Judgment and Are the signs the same? If the signs are different, it means that the voltage across the flying capacitor has crossed the median voltage, and the control direction is correct. If the signs are the same, then the absolute values ​​of the two are compared.

[0047] Step S404, when | |<| When |, the control direction is determined to be correct; when | |>| When |, the control direction is determined to be reversed.

[0048] In the application, the initial value of the flying capacitor voltage error is recorded during the initialization operation. This refers to immediately sampling the current flying capacitor voltage when the light-load control process is started. and bus voltage Calculate the error value =0.5× - The initial value is then stored in the controller's variable register. This initial value serves as the benchmark for subsequent control direction determination, reflecting the deviation of the flying capacitor voltage from the median value when entering light-load mode. A positive initial value indicates that the flying capacitor voltage is below the median value, while a negative initial value indicates that the flying capacitor voltage is above the median value; the absolute value reflects the magnitude of the deviation.

[0049] In application, after entering the control state, a slower PI loop is used for control. After a preset control period, the current flying capacitor voltage error value is obtained. A slower PI loop refers to a PI controller that, compared to one operating under normal conditions, has a slower proportional coefficient. and integral coefficient Setting this value to a smaller value slows down the adjustment speed. This provides the system with a sufficient observation window, allowing for smaller fluctuations in the flyaway capacitor voltage during adjustment. This facilitates accurate trend assessment without causing oscillations or overshoot interference due to excessively rapid adjustment. The preset control period is a fixed length, typically 100 milliseconds. At the end of this period, the current flyaway capacitor voltage error is read as... It is compared with the initial value.

[0050] In application, judgment and Whether the signs are the same is the first level of logic controlling the direction determination. If the signs are different, for example... >0 and A value less than 0 indicates that the flying capacitor voltage has changed from below the median to above the median, meaning the voltage has crossed the median point. This directly indicates that the control is effective and the direction is correct. If both values ​​have the same sign, it means the flying capacitor voltage has not yet crossed the median, and further judgment is needed through a second layer of logic.

[0051] In application, when | |<| When |, the control direction is determined to be correct; when | |>| When the current error is less than the absolute value of the initial error, it indicates that the voltage across the capacitor is moving towards the median, the error is converging, and the control direction is correct. When the absolute value of the current error is greater than the absolute value of the initial error, it indicates that the voltage across the capacitor is moving away from the median, the error is diverging, and this is a clear signal of an incorrect control direction, requiring a switch to the control state.

[0052] The sampling of the flying capacitor voltage can be achieved by directly measuring the voltage across the flying capacitor using a high-resolution ADC, or indirectly by calculating the difference between the bus voltage and the switching node voltage. The length of the preset control period can be a fixed value, set to 50 to 200 milliseconds based on the circuit time constant; alternatively, an adaptive adjustment method can be used, dynamically adjusting the observation window length according to the error magnitude, shortening it when the error is large and extending it when the error is small.

[0053] This application's embodiment achieves a reliable judgment of the correctness of the control direction by recording the initial error and comparing it with the current error after a control period using both sign and absolute value. Based on the observation of the error change trend, the physical meaning is clear, facilitating understanding and debugging; the two-layer judgment using sign and absolute value comparison covers all possible situations, eliminating any blind spots; the slow PI loop reduces the adjustment amplitude, and with sufficient observation time, effectively reduces the impact of measurement noise and transient disturbances on the judgment results.

[0054] In one embodiment, step S103 may further include the following steps S501 to S503: Step S501: After entering the control state, a PI loop with a response speed lower than the normal parameter is used for control. The current error is recorded each time the PI loop is entered. and previous error .

[0055] Step S502, when - When the absolute value of the difference is greater than 0, the absolute value of this difference is added to the change in the uplink error. ;when - When the difference is less than 0, the absolute value of this difference is added to the change in downlink error. .

[0056] Step S503: After a preset control period, compare... and :when - When <0, the control direction is determined to be correct; when - When the value is greater than 0, the control direction is determined to be reversed.

[0057] In application, after entering the control state, a PI loop with slower parameters is used for control, and the current error is recorded each time the PI loop is entered. and previous error This refers to storing the currently sampled and calculated flying capacitor voltage error as a data source during each PI operation in each control cycle. At the same time, the error of the previous control cycle is retained as... These two variables are updated sequentially each period, forming a sliding window of the error sequence. This design enables the system to track the periodic changes in error, providing raw data for subsequent calculations of cumulative changes.

[0058] In application, when - When the absolute value of the difference is greater than 0, the absolute value of this difference is added to the change in the uplink error. ;when - When the difference is less than 0, the absolute value of this difference is added to the change in downlink error. Upward change The cumulative shift in the direction of increasing error, the downward change. This reflects the cumulative movement in the direction of error reduction. Calculated for each control cycle. - If the value is positive, add its absolute value to the expression. If it is negative, add its absolute value to the expression. This method of accumulating both upward and downward changes separately can comprehensively reflect the net trend of error changes over the entire observation period, rather than just comparing the first and last points.

[0059] In the application, after a preset control period, the comparison is performed. and :when - When <0, the control direction is determined to be correct; when - When the value is greater than 0, the control direction is determined to be reversed. At the end of the preset control period, if the cumulative downward movement is greater than the cumulative upward movement, it indicates that the number or magnitude of error reductions dominated during the entire observation period, the overall trend of the flying capacitor voltage converges towards the median, and the control direction is correct. If the cumulative upward movement is greater than the cumulative downward movement, it indicates that error increases dominated, the overall voltage trend diverges away from the median, and the control direction is reversed. This judgment method based on the comparison of cumulative changes, compared to simply comparing the initial and final errors, can more accurately reflect the overall effect of the control process and reduce misjudgments caused by transient fluctuations.

[0060] The accumulation of error changes can be achieved through simple summation, directly adding the absolute values ​​of each change; alternatively, a weighted accumulation method can be used, assigning greater weight to recent changes to enhance timeliness. Variable processing after the control period ends can be done by immediately clearing the values ​​after each judgment. and It can be reset to zero for future use; alternatively, a sliding window method can be used to retain the change records of the most recent N periods for dynamic updates.

[0061] This application's embodiment determines the control direction by accumulating the changes in uplink and downlink errors and comparing their magnitudes. By accumulating over multiple periods, it reflects the overall trend, eliminating the influence of single measurement noise and short-term fluctuations, resulting in a more robust judgment. By adjusting the length of the accumulation period, a balance can be struck between judgment speed and accuracy. Short periods offer fast response but are susceptible to interference, while long periods provide stability but increase latency. It requires only two accumulation variables and one comparison operation, resulting in low computational load and making it suitable for implementation in resource-constrained embedded controllers.

[0062] In one embodiment, if the control direction is correct in step S104, the current control state is maintained and the PI loop parameters are adjusted, including the following: when and Same symbols and | |<| At the same time, the response speed of the PI loop should be increased appropriately.

[0063] when and When the symbols are different, according to Adjust the PI loop parameters according to the degree of deviation until stable.

[0064] In application, when and Same symbols and | |<| At this point, the response speed of the PI loop should be appropriately increased. This situation indicates that the flying capacitor voltage is moving towards the median but has not yet crossed it, and the control direction has been confirmed as correct. Continuing to use slow PI parameters at this time, while safe, results in excessively slow convergence, impacting system performance. Therefore, the proportional gain of the PI loop should be appropriately increased. and integral coefficient This accelerates the adjustment process. Parameter adjustments can be made incrementally, increasing the parameter by a certain percentage after each observation period until the set value under normal operating conditions is reached. This gradual acceleration strategy minimizes the convergence time while ensuring stability.

[0065] In application, when and When the symbols are different, according to Adjust the PI loop parameters according to the degree of deviation until stable. Different signs indicate that the flying capacitor voltage has crossed the median point and moved from one side to the other. At this point, it is necessary to adjust the current error... The absolute value of the value is used to determine whether overshoot has occurred. If | If the value is very small, it indicates that the voltage is stable near the median value, and the current parameters can be maintained or the system can switch to normal control mode. If | A large deviation indicates significant overshoot; the voltage has exceeded the median and then deviated considerably. In this case, the PI parameter should be appropriately reduced to slow down the adjustment speed and avoid oscillation. The parameters should be dynamically adjusted according to the degree of deviation so that the system eventually stabilizes within a small range around the median.

[0066] The PI parameter can be adjusted using a preset speed setting method, defining several sets of parameters corresponding to different adjustment speed levels, and switching between speed settings based on the judgment result; alternatively, continuous adjustment can be used, calculating parameter increments based on the error change rate to achieve smooth adjustment. Stability can be judged by using a method where the absolute value of the error is less than a threshold; when | | When the value is less than a certain set value, such as 1V, it is considered to be stable; alternatively, the error change rate can be less than a threshold, and when the error change is very small for several consecutive cycles, it is considered to be stable.

[0067] This application embodiment achieves a balanced optimization of control speed and stability by dynamically adjusting the PI loop parameters based on changes in the sign and absolute value of the error. After confirming the correct control direction, the adjustment speed is gradually increased, avoiding the slow convergence problem caused by continuously using slow parameters. After the voltage crosses the median, the speed is appropriately reduced based on the degree of overshoot, effectively suppressing oscillations caused by excessive parameter adjustments. The parameter adjustment employs a gradual strategy rather than abrupt switching, ensuring the continuity of the control output and reducing the impact on the circuit.

[0068] In one embodiment, step S104 involves entering a disturbance suppression control state, linearly reducing the duty cycle adjustment to zero, and then switching to the opposite control state, including the following steps S701 to S703: Step S701: When it is determined that the control direction is reversed, enter the disturbance suppression control state.

[0069] Step S702: Under the disturbance suppression control state, the duty cycle adjustment ΔD is linearly reduced to zero, and the current flying capacitor voltage error is recorded as the new starting error value. .

[0070] Step S703: After entering the disturbance-reducing control state from the positive control state, switch to the reverse control state; after entering the disturbance-reducing control state from the reverse control state, switch to the positive control state.

[0071] In application, when the control direction is determined to be reversed, entering the disturbance-suppression control state means that when the control direction judgment circuit detects that the absolute value of the flying capacitor voltage error is increasing instead of decreasing, confirming that the polarity of the current control state is opposite to the actual demand, the system does not immediately switch the control state, but first enters a transitional disturbance-suppression control state. The purpose of entering the disturbance-suppression control state is to eliminate the interference of the erroneous regulation amount accumulated by the PI loop on subsequent control. Since the PI loop has already output a certain duty cycle regulation amount ΔD during the erroneous direction control period, if it is directly switched to the opposite state without elimination, this historical regulation amount will be superimposed with the new regulation amount, which may lead to an excessively large overall regulation amount and cause violent voltage fluctuations.

[0072] In application, under disturbance suppression control, the duty cycle adjustment ΔD is linearly reduced to zero, and the current flying capacitor voltage error is recorded as the new initial error value. Linear reduction refers to decreasing the voltage by a fixed amount per control cycle at a constant slope until ΔD reaches zero. For example, if the current ΔD = 0.08, and the setting is to decrease it by 0.001 per millisecond, it will take 80 milliseconds to reduce it to zero. During the process of ΔD reaching zero, the difference in duty cycles between the first and third switching transistors gradually disappears, and they approach equality, causing the net charging and discharging of the flying capacitor to reach equilibrium. When ΔD is completely zero, the voltage error of the flying capacitor at this moment is recorded as the new starting value. This serves as a benchmark for determining the direction of control in a new round after switching to the opposite control state.

[0073] In application, after entering the disturbance-reducing control state from the positive control state, the system switches to the reverse control state, and vice versa. This rule defines the state transition direction after the disturbance-reducing control state ends. Since entering the disturbance-reducing control state is due to an incorrect direction of the current control state, it is necessary to switch to the opposite control state. Switching from positive to reverse means that the system will reconfigure the output polarity of the PI loop according to the logic of reverse energy flow; the same applies to switching from reverse to positive. After the switch, the system re-enters the control state, using slow PI parameters to begin a new round of tentative control and direction determination, repeating this cycle until the correct control direction is found and successful convergence is achieved.

[0074] The slope of the linear decrease in duty cycle adjustment can be a fixed value, preset according to the system response speed requirements; or an adaptive slope method can be used, adjusting the decrease rate according to the current ΔD value—a larger slope when ΔD is large to shorten the transition time, and a smaller slope when ΔD is small to ensure smoothness. The determination of the end of the disturbance cancellation state can be a precise determination of ΔD=0; or an approximate determination of |ΔD| being less than a certain small threshold can be used to address truncation errors in numerical calculations.

[0075] This application's embodiments achieve smooth and controllable state switching by introducing a disturbance-suppressing control state as a transitional link in the control state switching process. Linearly reducing the duty cycle adjustment amount allows the switching transistor's duty cycle to change gradually rather than abruptly, preventing transient spikes in voltage and current. Switching the state after resetting the erroneous adjustment amount to zero ensures that the new state starts control from clean initial conditions, unaffected by historical errors. Recording the new initial error at the end of disturbance suppression provides an accurate reference point for subsequent judgments, improving the reliability of the judgment.

[0076] In one embodiment, when judging based on the cumulative error change in step S104, the system enters a disturbance suppression control state, linearly reduces the duty cycle adjustment to zero, and then switches to the opposite control state, including the following steps S801 to S803: Step S801: When the control direction is determined to be reversed, enter the disturbance suppression control state.

[0077] Step S802: Under the disturbance suppression control state, the duty cycle adjustment amount ΔD is linearly reduced to zero.

[0078] Step S803: After entering the disturbance-dissipating control state from the positive control state, switch to the reverse control state; after entering the disturbance-dissipating control state from the reverse control state, switch to the positive control state.

[0079] In application, when the control direction is determined to be reversed based on the method of cumulative error change, the system enters a disturbance suppression control state. Specifically, when... - When the cumulative upward amount is greater than the cumulative downward amount, it indicates that the overall error of the flying capacitor voltage is increasing during the observation period. The control polarity is opposite to the actual demand. The system determines that the control direction is reversed and triggers a jump to the disturbance cancellation control state.

[0080] In application, under disturbance suppression control, the duty cycle adjustment ΔD is linearly reduced to zero. Unlike methods based on comparing initial and final errors, methods based on cumulative changes do not require re-recording the initial error value under disturbance suppression control because their control direction determination relies on real-time accumulated uplink and downlink changes, rather than comparison with a fixed initial value. The core task of disturbance suppression control remains to smoothly reduce the historically accumulated duty cycle adjustment to zero, creating conditions for switching to the opposite control state. The specific execution method of linear reduction is the same as in the aforementioned embodiments.

[0081] In application, the state transition rules are consistent with the aforementioned embodiments: switching from the positive control state to the reverse control state after disturbance cancellation, and switching from the reverse control state to the positive control state after disturbance cancellation. When entering a new control state after switching, the uplink and downlink cumulative amounts need to be cleared to zero so that they can be re-accumulated in the new state and a new round of control direction determination can be performed.

[0082] The timing for clearing the accumulated variable can be either immediately upon entering a new control state, or upon entering a disturbance cancellation state, allowing accumulation to continue during the disturbance cancellation period to prepare for subsequent judgments. The PI parameter initialization after a state transition can use a fixed slow parameter, or it can be done by selecting the initial parameter level based on the error magnitude at the end of disturbance cancellation, using a slower parameter to ensure stability when the error is large.

[0083] This application's embodiment uses a method based on the cumulative error change, combined with a disturbance cancellation control state, to achieve adaptive switching of the control direction. This approach has its own advantages compared to methods based on comparing the initial and final errors. Based on the statistical characteristics of error changes throughout the entire observation period rather than a two-point comparison, it has stronger resistance to transient disturbances; in the disturbance cancellation state, there is no need to record new initial errors, resulting in fewer state variables and a simpler implementation; it has a high degree of compatibility with cumulative judgment methods, and after disturbance cancellation, the accumulated variables are cleared, naturally connecting to a new round of judgment, ensuring logical coherence.

[0084] In one embodiment, after switching to a new control state via a disturbance reduction control state, the following steps S901 to S903 are further included: Step S901: First, use a PI loop with slower parameters (i.e., a PI loop with a response speed lower than normal parameters) to control the voltage of the flying capacitor.

[0085] Step S902: Gradually increase the response speed of the PI loop while monitoring the changing trend of the absolute value of the flying capacitor voltage error.

[0086] Step S903: If the absolute value of the flying capacitor voltage error continues to decrease, maintain the current control state until the loop parameters accelerate to normal parameters; if the absolute value of the flying capacitor voltage error shows an increasing trend, re-enter the disturbance suppression control state.

[0087] In applications, using a slower PI loop to control the flying capacitor voltage initially means that after switching from a noise-suppressing control state to a new control state, the normal PI parameters are not immediately used; instead, control restarts from the slower parameters. The purpose of this design is to provide a stable starting point for the subsequent gradual acceleration of the parameters. Since the state switch has just occurred, whether the polarity of the new control state truly matches the current actual requirements needs to be verified. Using slower parameters allows for a smaller adjustment range during the verification process, facilitating observation of the effects and timely correction.

[0088] In application, gradually increasing the PI loop parameters while monitoring the changing trend of the absolute value of the flying capacitor voltage error means that after confirming good control performance during the slow control phase, the PI parameters are systematically increased to accelerate convergence, while continuously monitoring error changes during the parameter increase process. Parameter acceleration can be achieved using a step-by-step approach, increasing the proportional and integral coefficients by one level at regular intervals. Simultaneously, the system continuously samples the flying capacitor voltage and calculates the absolute value of the error, observing whether its overall trend is decreasing or increasing.

[0089] In application, if the absolute value of the flying capacitor voltage error continues to decrease, the current control state is maintained until the loop parameters accelerate to normal parameters. A continuously decreasing absolute value indicates that the control direction is correct and the system remains stable after parameter increases; acceleration can continue until the normal operating parameters are reached. Once the parameters reach normal values ​​and the error converges below the set threshold, the light-load control process is considered complete, and the system can switch to the normal control mode. If the absolute value of the flying capacitor voltage error shows an increasing trend, the disturbance-suppression control state is re-entered. An increasing absolute value indicates that the polarity of the current control state is still incorrect, or that the parameter increase is too rapid, causing system instability. Regardless of the reason, the current control process needs to be stopped, the disturbance-suppression control state needs to be re-entered, the adjustment value reset to zero, and then the opposite control state needs to be switched to try again.

[0090] One strategy for gradually accelerating parameters is to use a fixed-increment method at fixed time intervals, increasing the parameters by a fixed percentage every preset period. Another approach is an adaptive adjustment based on the error convergence rate, accelerating the parameter increase when the error decreases rapidly and slowing it down when the error decreases slowly. Monitoring the error change trend can be done by comparing two adjacent observation points; alternatively, a sliding window linear regression method can be used to fit the slope of the error change curve and determine the trend.

[0091] This application's embodiments construct a robust adaptive convergence mechanism by employing a strategy of gradually accelerating parameters and continuously monitoring error trends after switching to a new control state. It not only verifies the correctness of the direction during the slow-speed phase but also continuously monitors stability during the parameter acceleration phase, providing dual protection. During parameter enhancement, it dynamically decides whether to continue accelerating or revert to a retry based on the error change trend, flexibly responding to various operating conditions. Through a closed-loop iteration of disturbance reduction, switching, verification, and speed adjustment, it ensures that the system will eventually find the correct direction and converge, exhibiting extremely strong robustness.

[0092] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0093] like Figure 3 As shown in the figure, this application embodiment also provides a method for controlling the voltage of the flying capacitor in a three-level buck circuit with a flying capacitor, the process of which is as follows: S1. Initial state: Clear According to the error Calculation formula Record the initial error value Depending on the current charging / discharging status of the device, it will switch to S2 or S3.

[0094] S2. Positive (State of Charge) Regulation: Upon entering this state, the state entry point is first determined, and the following situations exist: A. Enter directly from S1 B. Jump from S3 to S4 and then enter. In case A, determine if the current charging current of the device is greater than n (n > 0, generally taken as 3-5A, obtained according to the actual circuit parameters). If it is greater than n, and the device is not in a light load state, directly apply positive control. When the charging current is less than n, first use a slower PI loop to adjust the current. Implement control measures and record the current error after a period of time. to When comparing, the following situations arise: like and This indicates that the control is reversed, and the process jumps to S4; like and This indicates that the control is in the positive direction, and the PI loop should be accelerated appropriately; like This indicates that the control is in a positive direction and has already exceeded the control value. The deviation should be appropriately slowed down or accelerated in the PI loop; like and This indicates that the control is reversed, and the process jumps to S4; like and This indicates that the control is in the positive direction, and the PI loop should be accelerated appropriately; like This indicates that the control is in a positive direction and has already exceeded the control value. The deviation should be appropriately slowed down or accelerated in the PI loop; i = 1, 2, 3...n, where i in S1 is 1, and i + 1 is executed each time S4 ​​is executed.

[0095] In case B, first use the slower PI loop. Implement control measures, gradually increase the speed of the loop, and observe the control process. In this situation, until the loop accelerates to normal parameters; if During the loop adjustment process, maintain a decreasing trend (converging to 0), and keep operating in S2. Gradually increase (deviating from 0), then jump to S4.

[0096] S3. Reverse (discharge state) control: Upon entering this state, the state entry point is first determined, and the following situations exist: A. Enter directly from S1 B. Jump from S2 to S4 and then enter. In case A, determine if the current discharge current of the device is less than n (n < 0). If it is less than n, and the device is not in a light load state, enter the normal loop for reverse regulation. If the discharge current is greater than n, first use a slower PI loop to... Implement control measures and record the current error after a period of time. to Compare this to the case of S2.

[0097] In case B, first use the slower PI loop. Implement control measures, gradually increase the speed of the loop, and observe the control process. In this situation, until the loop accelerates to normal parameters; if During the loop adjustment process, maintain the decreasing trend (converging to 0), and keep operating in S3. Gradually increase (deviating from 0), then jump to S4.

[0098] S4. Disturbance reduction control: Upon entering this state, the linear reduction occurs. Record the initial error up to 0. The jump is based on the previous state. If the jump is from S2, the state enters S3, and if the jump is from S3, the state enters S2.

[0099] like Figure 4 As shown in the figure, this application embodiment also provides a method for controlling the voltage of the flying capacitor in a three-level buck circuit with a flying capacitor, the process of which is as follows: S1. Initial state: Clear Depending on the current charging / discharging status of the device, it will switch to S2 or S3.

[0100] S2. Positive (State of Charge) Regulation: Upon entering this state, the state entry point is first determined, and the following situations exist: A. Enter directly from S1 B. Jump from S3 to S4 and then enter. In case A, determine if the current charging current of the device is greater than n (n > 0, generally taken as 3-5A, obtained according to the actual circuit parameters). If it is greater than n, and the device is not in a light load state, directly apply positive control. When the charging current is less than n, first use a slower PI loop to adjust the current. Control is implemented, and the current error is recorded each time the loop is entered. (The previous error is recorded as) ): like ,Record ; like ,Record ; After controlling for a period of time (usually 100ms), and Compare them.

[0101] like This indicates that the error is increasing in the direction of deviating from the median voltage, so the control reverses and jumps to S4; like Record the change in error towards the median voltage, control the positive direction, and appropriately speed up the PI loop; In case B, first use the slower PI loop. Implement control measures, gradually increase the speed of the loop, and observe the control process. In this situation, until the loop accelerates to normal parameters; if During the loop adjustment process, maintain a decreasing trend (converging to 0), and keep operating in S2. Gradually increase (deviating from 0), then jump to S4.

[0102] S3. Reverse (discharge state) control: A. Enter directly from S1 B. Jump from S2 to S4 and then enter. In case A, determine if the current discharge current of the device is less than n (n < 0). If it is less than n, and the device is not in a light load state, directly reverse the control. If the discharge current is greater than n, first use a slower PI loop to... Control is implemented, and each time the loop is entered, a record is made. The situation is the same as in S2.

[0103] In case B, first use the slower PI loop. Implement control measures, gradually increase the speed of the loop, and observe the control process. In this situation, until the loop accelerates to normal parameters; if During the loop adjustment process, maintain a decreasing trend (converging to 0), and keep operating in S2. Gradually increase (deviating from 0), then jump to S4.

[0104] S4. Disturbance reduction control: Upon entering this state, the linear reduction occurs. When the state reaches 0, a transition is made based on the previous state. If the state transitioned from S2, the state enters S3; if the state transitioned from S3, the state enters S2.

[0105] like Figure 5 As shown in the embodiment of this application, the flying capacitor voltage control device 100 for a three-level buck circuit with a flying capacitor includes: The initialization module 101 is used to perform initialization operations and clear the duty cycle adjustment amount in response to the circuit entering a light load condition.

[0106] The state determination module 102 is used to enter the corresponding control state according to the current charging and discharging state of the circuit, and to control the voltage of the flying capacitor using a PI loop.

[0107] The direction detection module 103 is used to determine whether the control direction is correct based on the change in the voltage error of the flying capacitor under the control state.

[0108] The control execution module 104 is used to maintain the current control state and adjust the PI loop parameters when the control direction is correct, and enter the disturbance elimination control state when the control direction is reversed, linearly reducing the duty cycle adjustment amount to zero and then switching to the opposite control state.

[0109] In applications, the initialization module is the functional unit responsible for the light-load mode startup process in the control device. This module receives a light-load judgment signal from the current detection circuit and triggers the initialization operation when the signal is valid. The specific contents of the initialization operation include clearing the integral accumulation value of the PI loop to zero, setting the duty cycle adjustment ΔD to zero, resetting all status flags to their initial states, and recording the current flying capacitor voltage error as the starting value as needed. After completing the above operations, the initialization module sends a ready signal to the status judgment module to start the subsequent control process. The key design point of this module is to ensure the integrity and atomicity of the initialization process, that is, all relevant variables must be reset synchronously to avoid some variables retaining historical values ​​and affecting subsequent judgments.

[0110] In applications, the state determination module is the functional unit in the control device responsible for selecting the control state and performing PI loop calculations. Based on the charging / discharging state signal provided by the current detection circuit, this module determines whether the system should enter a forward or reverse control state. Upon entering the appropriate state, the state determination module executes PI loop calculations according to preset parameter configurations, calculates the flying capacitor voltage error, and outputs a duty cycle adjustment ΔD after processing with proportional and integral terms. ΔD is then distributed to the duty cycles of the first and third switching transistors according to the direction of deviation of the flying capacitor voltage from its median value. The state determination module also manages the switching of PI parameters, performing corresponding parameter update operations upon receiving parameter adjustment commands from the direction detection module.

[0111] In applications, the direction detection module is the functional unit in the control device responsible for determining the correctness of the control direction. This module continuously acquires the flying capacitor voltage signal and calculates the error value, recording the initial error and current error, or the cumulative changes in upward and downward errors, according to the adopted judgment method. At the end of the preset observation period, the direction detection module outputs a judgment result based on the error changes: if the control direction is determined to be correct, it sends a command to the control execution module to maintain the state or accelerate the parameters; if the control direction is determined to be reversed, it sends a command to the control execution module to enter the disturbance cancellation state. The direction detection module also needs to reset its internal variables at appropriate times, such as clearing the cumulative changes after switching control states and updating the initial error value after disturbance cancellation ends.

[0112] In applications, the control execution module is the functional unit in the control device responsible for executing control actions and switching states. When the direction detection module determines that the control direction is correct, the control execution module maintains the current control state and adjusts the PI loop parameters in a timely manner according to instructions to accelerate convergence. When the direction detection module determines that the control direction is reversed, the control execution module switches the system to the disturbance-suppression control state and executes a linear decrease in the duty cycle adjustment. When the adjustment reaches zero, the control execution module jumps the system to the opposite control state according to the switching rules and sends the corresponding reset or start signal to the initialization module or state determination module to start a new round of control process. The control execution module is also responsible for the interface with the external drive circuit, converting the calculated duty cycle value into a PWM drive signal and outputting it to each switching transistor.

[0113] Specifically, the aforementioned control device can be implemented in software on a digital signal processor or microcontroller platform. The initialization module, status determination module, direction detection module, and control execution module can be designed as independent software tasks or functions, coordinated by a task scheduler. The modules communicate with each other through shared variables or message queues. Shared variables are suitable for simple and fast data exchange, while message queues are suitable for instruction transmission that requires precise timing. Alternatively, the modules can be integrated into a complete interrupt service routine, executing the functions of each module sequentially within the PWM synchronization interrupt to ensure the accuracy of the control timing.

[0114] The hardware implementation of the control device can adopt a high-performance DSP-based solution, utilizing the powerful computing capabilities of the DSP to implement complex control algorithms and fast AD sampling; alternatively, a high-speed FPGA-based solution can be used, designing each module as hardware logic to achieve nanosecond-level response speeds. The software architecture can employ a foreground / background system architecture, with the control algorithm executed in timed interrupts and status monitoring performed in the main loop; alternatively, a real-time operating system architecture can be used, with each module designed as an independent task, running in parallel via kernel scheduling.

[0115] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for controlling the voltage of a flying capacitor in a three-level buck circuit, characterized in that, include: In response to the circuit entering a light-load condition, an initialization operation is performed to clear the duty cycle adjustment. Based on the current charging and discharging state of the circuit, it enters the corresponding regulation state and uses a PI loop to control the voltage of the flying capacitor. In the aforementioned control state, the correctness of the control direction is determined based on the change in the flying capacitor voltage error. If the control direction is correct, the current control state is maintained and the PI loop parameters are adjusted; if the control direction is reversed, the disturbance reduction control state is entered, the duty cycle adjustment is linearly reduced to zero, and then the opposite control state is switched.

2. The bus mid-voltage control method as described in claim 1, characterized in that, The response to the circuit entering a light-load condition includes: The charging and discharging current value of the detection circuit; When the circuit is in a charging state and the charging current is less than the preset positive threshold, or when the circuit is in a discharging state and the absolute value of the discharging current is less than the absolute value of the preset negative threshold, the circuit is determined to enter a light load condition.

3. The bus mid-voltage control method as described in claim 1, characterized in that, The step of entering the corresponding control state based on the current charging and discharging state of the circuit includes: When the circuit is in the charging state, it enters the positive control state; When the circuit is in a discharging state, it enters a reverse control state; Under each control state, the duty cycle adjustment is output through the PI loop to create a difference in the duty cycle between the first and third switching transistors.

4. The bus mid-voltage control method as described in claim 1, characterized in that, The method of determining whether the control direction is correct based on the change in the flying capacitor voltage error includes: Record the initial value of the flying capacitor voltage error during initialization. ; After entering the control state, a PI loop with a response speed lower than normal parameters is used for control. After a preset control period, the current flying capacitor voltage error value is obtained. ; judge and Are the signs the same? If the signs are different, the control direction is correct; if the signs are the same, compare the absolute values ​​of the two. When | |<| When |, the control direction is determined to be correct; when | |>| When |, determine that the control direction is reversed; The flying capacitor voltage error is the difference between half of the bus voltage and the flying capacitor voltage.

5. The bus mid-voltage control method as described in claim 1, characterized in that, The method of determining whether the control direction is correct based on the change in the flying capacitor voltage error includes: After entering the control state, a PI loop with a response speed lower than the normal parameters is used for control, and the current error is recorded each time the PI loop is entered. and previous error ; when - When the absolute value of the difference is greater than 0, the absolute value of the difference is added to the change in the upward error. ;when - When the difference is less than 0, the absolute value of the difference is added to the change in downward error. ; After a preset control period, the comparison and :when < When the control direction is correct, it is determined that the control direction is correct; when > When this happens, the control direction is determined to be reversed; The flying capacitor voltage error is the difference between half of the bus voltage and the flying capacitor voltage.

6. The bus mid-voltage control method as described in claim 4, characterized in that, If the control direction is correct, the current control state is maintained and the PI loop parameters are adjusted, including: when and Same symbols and | |<| |At the same time, improve the response speed of the PI loop; when and When the symbols are different, according to Adjust the PI loop parameters according to the degree of deviation until stable.

7. The bus mid-voltage control method as described in claim 4, characterized in that, The process of entering the disturbance suppression control state, which involves linearly reducing the duty cycle adjustment to zero and then switching to the opposite control state, includes: When the control direction is determined to be reversed, the system enters the disturbance suppression control state. Under the aforementioned disturbance suppression control state, the duty cycle adjustment ΔD is linearly reduced to zero, and the current flying capacitor voltage error is recorded as the new initial error value. ; After entering the disturbance-reducing control state from the positive control state, it switches to the reverse control state; after entering the disturbance-reducing control state from the reverse control state, it switches to the positive control state.

8. The bus mid-voltage control method as described in claim 5, characterized in that, The process of entering the disturbance suppression control state, which involves linearly reducing the duty cycle adjustment to zero and then switching to the opposite control state, includes: When the control direction is determined to be reversed, the system enters the disturbance suppression control state. Under the aforementioned disturbance reduction control state, the duty cycle adjustment amount ΔD is linearly reduced to zero; After entering the disturbance-reducing control state from the positive control state, it switches to the reverse control state; after entering the disturbance-reducing control state from the reverse control state, it switches to the positive control state.

9. The bus mid-voltage control method as described in claim 7 or 8, characterized in that, After switching from the disturbance reduction control state to the new control state, the following is also included: First, use a PI loop with a response speed lower than normal parameters to control the voltage of the flying capacitor; Gradually increase the response speed of the PI loop while monitoring the changing trend of the absolute value of the flying capacitor voltage error; If the absolute value of the flying capacitor voltage error shows a decreasing trend, the current control state is maintained until the PI loop parameters reach normal parameters; if the absolute value of the flying capacitor voltage error shows an increasing trend, the disturbance suppression control state is entered again.

10. A flying capacitor voltage control device for a three-level buck circuit with a flying capacitor, characterized in that, include: The initialization module is used to perform initialization operations and clear the duty cycle adjustment in response to the circuit entering a light load condition. The state determination module is used to enter the corresponding control state according to the current charging and discharging state of the circuit, and uses a PI loop to control the voltage of the flying capacitor. The direction detection module is used to determine whether the control direction is correct based on the change in the voltage error of the flying capacitor under the control state. The control execution module is used to maintain the current control state and adjust the PI loop parameters when the control direction is correct. When the control direction is reversed, it enters the disturbance reduction control state, linearly reduces the duty cycle adjustment amount to zero, and then switches to the opposite control state.

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