A flying capacitor pre-charging method and switched capacitor converter

Abstract

The embodiment of the application provides a flying capacitor pre-charging method and a switched capacitor converter, the method is applied to a switched capacitor converter comprising a main power circuit and a pre-charging branch, and comprises the following steps: calculating a pre-bias duty cycle according to an input voltage and an output voltage of the main power circuit; calculating a steady-state voltage expected value of a flying capacitor according to the pre-bias duty cycle; enabling the pre-charging branch, and pre-charging the flying capacitor by an input power supply; when an actual voltage of the flying capacitor reaches the steady-state voltage expected value, stopping enabling the pre-charging branch and pre-biasing to start the main power circuit. The embodiment of the application calculates a target pre-charging voltage of the flying capacitor according to the actual relationship between the input voltage and the output voltage, adapts to different pre-bias starting conditions, and can realize control on the pre-charging voltage of the flying capacitor.

Description

Technical Field

[0001] This application relates to the field of switched capacitors, and more particularly to a flying capacitor pre-charging method and a switched capacitor converter. Background Technology

[0002] With the rapid development of artificial intelligence technology, the demand for computing power is exploding, posing unprecedented challenges to the power supply architecture of hardware systems. To meet the ever-decreasing core voltage and continuously increasing current requirements of high-performance chips under advanced manufacturing processes, server power supply systems are evolving towards low-voltage, high-current operation. Under this trend, the power rating and power density of intermediate bus converters, a key component of data center power supply architecture, are also continuously improving.

[0003] In non-isolated conversion applications, hybrid switched-capacitor converters have become a valuable power topology choice due to their ability to achieve extremely high power density and conversion efficiency. However, before startup, this type of topology requires pre-charging of the flying capacitors in the circuit to prevent damage from large inrush currents. Traditional pre-charging methods typically require additional complex circuitry, occupying valuable PCB space and incurring high costs. Furthermore, traditional solutions generally only pre-charge the flying capacitors to half of the input voltage, failing to precisely control the pre-charging voltage based on actual input and output voltage conditions. In addition, traditional solutions often employ open-loop control, making it impossible to determine whether the pre-charging process is complete, and only allowing for a passive, sufficient delay time. Summary of the Invention

[0004] This application aims to solve the problem of the inability to control the pre-charge voltage of the flying capacitor in existing switched capacitor converters.

[0005] In a first aspect, this application provides a flying capacitor pre-charging method applied to a switched capacitor converter including a main power circuit and a pre-charging branch. The main power circuit includes a flying capacitor, and the pre-charging branch is connected between the input power supply and the flying capacitor. The method includes the following steps: calculating a pre-bias duty cycle based on the input voltage and output voltage of the main power circuit; calculating the expected steady-state voltage of the flying capacitor based on the pre-bias duty cycle; enabling the pre-charging branch to pre-charge the flying capacitor using the input power supply; and when the current actual voltage of the flying capacitor reaches the expected steady-state voltage, stopping the pre-charging branch and pre-biasing the main power circuit.

[0006] Optionally, calculating the pre-bias duty cycle based on the input and output voltages of the main power circuit specifically includes the following steps: acquiring the input voltage and the output voltage; and calculating the ratio parameter according to the following formula:

[0007] Among them, V OUT V is the input voltage. IN The output voltage is given; when the ratio parameter is greater than a preset threshold, the pre-bias duty cycle is calculated according to the following formula:

[0008] When the ratio parameter is less than or equal to the preset threshold, the pre-bias duty cycle is calculated according to the following formula:

[0009] Optionally, calculating the expected steady-state voltage of the flying capacitor based on the pre-bias duty cycle specifically includes the following steps: when the ratio parameter is greater than the preset threshold, the expected steady-state voltage is calculated according to the following formula:

[0010] When the ratio parameter is less than or equal to the preset threshold, the expected steady-state voltage value is calculated according to the following formula:

[0011] Optionally, the step of stopping the pre-charge branch and starting the main power circuit when the actual voltage of the flying capacitor reaches the expected steady-state voltage value specifically includes the following steps: obtaining the actual voltage; determining whether the actual voltage is greater than or equal to the expected steady-state voltage value; if so, stopping the pre-charge branch and starting the main power circuit with pre-bias.

[0012] Optionally, before enabling the pre-charge branch to pre-charge the flying capacitor by the input power supply, the method further includes: acquiring the actual voltage; determining whether the actual voltage is greater than or equal to the expected steady-state voltage value; if the actual voltage is greater than the expected steady-state voltage value, determining whether a first voltage difference between the actual voltage and the expected steady-state voltage value is greater than a preset first error; if the actual voltage is equal to the expected steady-state voltage value, or the first voltage difference is not greater than the first error, directly pre-biasing and starting the main power circuit; if the first voltage difference is greater than the first error, outputting a first abnormal signal.

[0013] Optionally, obtaining the actual voltage specifically includes the following steps: sampling the node voltage at the connection point between the flying capacitor and the input power supply; and calculating the actual voltage according to the following formula:

[0014] Wherein, V1 is the node voltage.

[0015] Optionally, before enabling the pre-charge branch to pre-charge the flying capacitor by the input power supply, the method further includes: sampling the node voltage of the common node of the flying capacitor and the input power supply; determining whether the node voltage is less than the output voltage, and whether a second voltage difference between the node voltage and the output voltage is greater than a preset second error; if the second voltage difference is greater than the second error, then outputting a second abnormal signal.

[0016] Optionally, after enabling the pre-charge branch to pre-charge the flying capacitor by the input power supply, the method further includes: outputting a third abnormal signal when the actual voltage does not reach the expected steady-state voltage value within a preset time threshold.

[0017] Secondly, this application also provides a switched-capacitor converter, including: a main power circuit, including a first switching transistor, a second switching transistor, a fifth switching transistor, a sixth switching transistor, a flying capacitor, a coupling inductor, an output capacitor, and a load resistor; wherein, the drain of the first switching transistor is connected to the input power supply, the source of the first switching transistor is connected to the drain of the second switching transistor to form a common node, the first end of the flying capacitor is connected to the common node, the second end of the flying capacitor is connected to the drain of the fifth switching transistor and the first end of the first winding of the coupling inductor, and the source of the fifth switching transistor is grounded; the source of the second switching transistor is connected to the drain of the sixth switching transistor and the first end of the second winding of the coupling inductor, and the source of the sixth switching transistor is grounded. The first winding of the coupling inductor and the second winding are connected to the first terminal of the output capacitor and the first terminal of the load resistor, respectively. The second terminal of the output capacitor and the second terminal of the load resistor are grounded. A pre-charge branch is connected between the input power supply and the common node. A pre-charge control module has its input terminals connected to the input power supply, the common node, and the first terminal of the output capacitor, respectively, and its output terminal connected to the control terminal of the pre-charge branch. The pre-charge control module is configured to calculate the expected steady-state voltage of the flying capacitor based on the input voltage and output voltage of the main power circuit, and control the on / off state of the pre-charge branch based on the actual voltage of the flying capacitor and the expected steady-state voltage.

[0018] Optionally, the pre-charge branch includes a third switch, a fourth switch, a first diode, a current-limiting resistor, a first bias resistor, and a second bias resistor; the collector of the third switch is connected to the input power supply and the first terminal of the first bias resistor, the base of the third switch is connected to the second terminal of the first bias resistor and the first terminal of the second bias resistor, and the second terminal of the second bias resistor is connected to the drain of the fourth switch; the gate of the fourth switch is connected to the output terminal of the pre-charge control module, the source of the fourth switch is grounded, the emitter of the third switch is connected to the anode of the first diode, the cathode of the first diode is connected to the first terminal of the current-limiting resistor, and the second terminal of the current-limiting resistor is connected to the common node.

[0019] At least one advantage of the flying capacitor pre-charging method provided in this application embodiment is that by calculating the target pre-charging voltage of the flying capacitor based on the actual relationship between the input voltage and the output voltage, and adapting to different pre-bias start-up conditions, the pre-charging voltage of the flying capacitor can be controlled, thereby avoiding the start-up surge current caused by pre-charging voltage mismatch, reducing the current stress on the switching transistor and capacitor, improving system reliability, reducing passive waiting time, and accelerating system start-up speed. Attached Figure Description

[0020] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0021] Figure 1 This is the circuit schematic of the main power circuit of the switched capacitor converter. Figure 2 A schematic diagram of a switched capacitor converter provided for an embodiment of the present invention; Figure 3 A flowchart illustrating a method for pre-charging a flying capacitor provided for an embodiment of the present invention; Figure 4 Another structural schematic diagram of a switched capacitor converter provided for an embodiment of the present invention; Figure 5 A circuit diagram of a pre-charge branch provided for an embodiment of the present invention; Figure 6 The pre-charging process waveform of the switched capacitor converter provided in the embodiment of the present invention is shown; Figure 7 The pre-charging process waveform of the switched capacitor converter provided in the embodiment of the present invention is shown. Detailed Implementation

[0022] To facilitate understanding of this application, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as being "connected" to another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "upper," "lower," "inner," "outer," "bottom," etc., used in this specification indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0023] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items.

[0024] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.

[0025] Please see Figure 1 , Figure 1 This is a circuit schematic of the main power circuit 100 of the switched capacitor converter involved in this application embodiment. The main power circuit is a hybrid switched capacitor converter topology, which includes a first switch Q1, a second switch Q2, a fifth switch Q5, a sixth switch Q6, a flying capacitor Cfly, a coupling inductor, and an output filter circuit. The coupling inductor includes a first winding L1 and a second winding L2, and the output filter circuit includes an output capacitor Co and a load resistor Rload.

[0026] In this circuit, the drain of the first switching transistor Q1 is connected to the input power supply, and the source of the first switching transistor Q1 is connected to the drain of the second switching transistor Q2. The connection node between them is defined as the common node VS. The first terminal of the flying capacitor Cfly is connected to the common node VS, and the second terminal of the flying capacitor Cfly is connected to the drain of the fifth switching transistor Q5 and the first terminal of the first winding L1 of the coupling inductor. The source of the fifth switching transistor Q5 is grounded.

[0027] The source of the second switch Q2 is connected to the drain of the sixth switch Q6 and the first terminal of the second winding L2 of the coupling inductor. The source of the sixth switch Q6 is grounded. The second terminals of the first winding L1 and the second winding L2 of the coupling inductor are connected to the output terminal, specifically the first terminal of the output capacitor Co and the first terminal of the load resistor Rload. The second terminals of the output capacitor Co and the load resistor Rload are grounded. The voltage across the output capacitor Co is the output voltage Vout.

[0028] It should be noted that the first switch Q1 and the second switch Q2 are complementary in conduction; that is, when the first switch Q1 is on, the second switch Q2 is off, and when the first switch Q1 is off, the second switch Q2 is on. Their phase difference is 180°, and their duty cycles are both D. The fifth switch Q5 is complementary in conduction to the first switch Q1, and the sixth switch Q6 is complementary in conduction to the second switch Q2.

[0029] Based on the above structure and driving logic, the main power circuit operates in two alternating phases: In the first stage, the first switch Q1 and the sixth switch Q6 are turned on, while the second switch Q2 and the fifth switch Q5 are turned off. At this time, the first switch Q1 pulls the potential of the common node VS to the input voltage Vin. The second terminal of the flying capacitor Cfly (i.e., the connection between the drain of the fifth switch Q5 and the first terminal of the first winding L1) is in a floating state due to the fifth switch Q5 being turned off, and its potential is Vin. VF, where VF is the voltage across the flying capacitor Cfly.

[0030] Therefore, the voltage across the first winding L1 is (Vin VF) Vout, the first winding L1 is in a charging state. Simultaneously, the sixth switch Q6 turns on, pulling the first terminal of the second winding L2 to ground potential, and the voltage across the second winding L2 is... Vout, the second winding L2 is in freewheeling mode.

[0031] In the second stage, the second switch Q2 and the fifth switch Q5 are turned on, while the first switch Q1 and the sixth switch Q6 are turned off. At this time, the fifth switch Q5 pulls the second terminal of the flying capacitor Cfly to ground potential, and the voltage VF on the flying capacitor Cfly makes the potential of the common node VS VF. The second switch Q2 connects the common node VS to the first terminal of the second winding L2, therefore the potential of the first terminal of the second winding L2 is VF.

[0032] The voltage across the second winding L2 is VF Vout, the second winding L2 is in a charging state. Simultaneously, the sixth switch Q6 is turned off, and the first terminal of the first winding L1 is pulled to ground potential by the fifth switch Q5. The voltage across the first winding L1 is... Vout, the first winding L1 is in freewheeling mode.

[0033] The two stages described above operate alternately, with the first winding L1 and the second winding L2 charging and freewheeling alternately, effectively reducing output ripple. Understandably, before the main power circuit starts, the flying capacitor Cfly needs to be pre-charged to prevent surge current damage caused by the deviation between the voltage across Cfly and the voltage required for steady-state operation during startup.

[0034] Please see Figure 2 , Figure 2 This is a schematic diagram of a switched-capacitor converter provided in an embodiment of the present invention. This switched-capacitor converter adds a pre-charge branch to the aforementioned main power circuit, used to pre-charge the flying capacitor Cfly before the main power circuit starts.

[0035] like Figure 2 As shown, the switched capacitor converter includes a main power circuit 100 and a pre-charge branch 200. The topology of the main power circuit 100 is as described in the previous embodiment and will not be repeated here.

[0036] The precharge branch 200 is connected between the input power supply and the common node VS. Specifically, the input terminal of the precharge branch 200 is connected to the input power supply Vin, and the output terminal of the precharge branch 200 is connected to the common node VS, which is the connection node between the source of the first switching transistor Q1 and the drain of the second switching transistor Q2. The precharge branch 200 is used to transfer the energy of the input power supply Vin to the flying capacitor Cfly before the main power circuit 100 starts, thus precharging the flying capacitor Cfly.

[0037] It should be noted that the precharge branch 200 has a unidirectional conduction characteristic, that is, the charging current can only flow from the input power source Vin through the precharge branch 200 to the common node VS, and cannot flow in the reverse direction.

[0038] Before the main power circuit 100 starts, since the first switch Q1 is in the off state, the input power supply Vin cannot charge the flying capacitor Cfly through the first switch Q1. Therefore, an independent charging path needs to be provided through the pre-charge branch 200. During the pre-charge process, the charging current flows from the input power supply Vin through the pre-charge branch 200 to the common node VS, then through the flying capacitor Cfly and the first winding L1 to the output terminal Vout, and finally flows back to the ground terminal through the output capacitor Co, thereby realizing the pre-charge of the flying capacitor Cfly.

[0039] After the pre-charge branch 200 completes the pre-charging of the flying capacitor Cfly and stops working, the main power circuit 100 performs a pre-bias start-up and enters normal operation. During the normal operation of the main power circuit 100, the pre-charge branch 200 remains closed and does not affect the normal operation of the main power circuit 100.

[0040] Under steady-state operating conditions, the relationship between the voltage VF across the flying capacitor Cfly and the duty cycle D depends on the ratio of the input voltage Vin to the output voltage Vout. Define the ratio parameter k = 2 × Vout / Vin. Based on the relationship between the ratio parameter k and a preset threshold, the steady-state voltage VF of the flying capacitor Cfly has the following two operating modes: In the first operating mode, when the ratio parameter k is less than or equal to the preset threshold, i.e., 2×Vout / Vin≤0.5, the duty cycle D is less than or equal to 50%. The formula for calculating the duty cycle D is:

[0041] In this mode, the steady-state voltage of the flying capacitor Cfly is:

[0042] That is, the flying capacitor Cfly is always charged to half of the input voltage, playing the classic charge pump voltage divider role.

[0043] In the second operating mode, when the ratio parameter k is greater than the preset threshold, i.e., 2×Vout / Vin>0.5, the duty cycle D is greater than 50%, and the conduction times of the first switch Q1 and the second switch Q2 overlap. The formula for calculating the duty cycle D is:

[0044] In this mode, the steady-state voltage of the flying capacitor Cfly is:

[0045] That is, the voltage across the flying capacitor Cfly is no longer fixed at Vin / 2, but changes dynamically with the relationship between the input voltage and the output voltage.

[0046] As can be seen from the two working modes above, if there is already residual voltage at the output terminal when the main power circuit starts up (i.e., pre-biased startup state), the pre-charge target voltage of the flying capacitor Cfly needs to be calculated based on the actual input voltage Vin and output voltage Vout at this time, rather than simply charging to Vin / 2.

[0047] Please see Figure 3 , Figure 3This is a flowchart illustrating a flying capacitor pre-charging method according to an embodiment of the present invention. This flying capacitor pre-charging method is applied to a switched capacitor converter as described in the foregoing embodiments, including a main power circuit 100 and a pre-charging branch 200, and specifically includes the following steps: Step S100: Calculate the pre-bias duty cycle based on the input voltage and output voltage of the main power circuit.

[0048] Before the main power circuit 100 starts, the input voltage Vin and the output voltage Vout are first acquired. The so-called pre-bias duty cycle refers to the duty cycle D required for the main power circuit 100 to start up, calculated based on the current actual input voltage Vin and output voltage Vout, under the condition that there may be residual voltage at the output terminal (i.e., pre-bias start-up state).

[0049] As described in the preceding embodiments, the ratio parameter k is defined as 2 × Vout / Vin. Based on the relationship between the ratio parameter k and the preset threshold, the calculation of the pre-bias duty cycle D falls into the following two cases: When the ratio parameter k is greater than the preset threshold, the pre-bias duty cycle is calculated according to the following formula:

[0050] When the ratio parameter k is less than or equal to the preset threshold, the pre-bias duty cycle is calculated according to the following formula:

[0051] In this embodiment, the preset threshold is set to 0.5. Continuing with the previous example data, assume the input voltage Vin = 48V: If the output voltage Vout=5V, then the ratio parameter k=2×5 / 48≈0.208, which is less than the preset threshold of 0.5, belonging to the first case, and the pre-bias duty cycle D=2×5 / 48≈0.208.

[0052] If the output voltage Vout=12V, then the ratio parameter k=2×12 / 48=0.5, which is equal to the preset threshold of 0.5, belonging to the second case, and the pre-bias duty cycle D=2×12 / 48=0.5.

[0053] If the output voltage Vout = 16V, then the ratio parameter k = 2 × 16 / 48 ≈ 0.667, which is greater than the preset threshold of 0.5, belonging to the first case, the pre-bias duty cycle. .

[0054] It should be noted that when there is no residual voltage at the output terminal, i.e., Vout=0V, the ratio parameter k=0, which is less than the preset threshold of 0.5, and the pre-bias duty cycle D=0. This is the cold start condition of the main power circuit 100 under the condition of no pre-bias.

[0055] Step S200: Calculate the expected steady-state voltage of the flying capacitor based on the pre-bias duty cycle.

[0056] The so-called steady-state voltage expectation value refers to the voltage value that the flying capacitor Cfly should reach after the main power circuit 100 enters steady-state operation under the pre-bias duty cycle D calculated in step S100. This steady-state voltage expectation value is the pre-charge target voltage of the flying capacitor Cfly.

[0057] Based on the relationship between the ratio parameter k and the preset threshold in step S100, the calculation of the expected steady-state voltage value VF is also divided into the following two cases: When the ratio parameter k is greater than the preset threshold, the expected steady-state voltage value is calculated according to the following formula:

[0058] When the ratio parameter k is less than or equal to a preset threshold, the expected steady-state voltage value is calculated according to the following formula:

[0059] Continuing with the previous example data, assume the input voltage Vin = 48V: If the output voltage Vout=5V, then the ratio parameter k≈0.208, which is less than the preset threshold of 0.5, and the expected steady-state voltage value VF=0.5×48=24V.

[0060] If the output voltage Vout=12V, then the ratio parameter k=0.5, which is equal to the preset threshold of 0.5, and the expected steady-state voltage value VF=0.5×48=24V.

[0061] If the output voltage Vout = 16V, then the ratio parameter k ≈ 0.667, which is greater than the preset threshold of 0.5, the pre-bias duty cycle D ≈ 0.577, and the expected steady-state voltage VF = (1 0.577)×48≈20.3V.

[0062] As can be seen from the above example, if the output voltage Vout=5V or the output voltage Vout=12V, the pre-charge target voltage of the flying capacitor Cfly is Vin / 2=24V. At this time, the traditional solution of charging only to half of the input voltage can just meet the requirements.

[0063] However, if the output voltage Vout=16V, the pre-charge target voltage of the flying capacitor Cfly is 20.3V, which is lower than Vin / 2=24V. If the traditional method is still used to charge the flying capacitor Cfly to 24V, there will be a deviation of 3.7V between the voltage of the flying capacitor Cfly and the actual required steady-state voltage at startup, which may cause a surge current to be generated at startup.

[0064] Step S300: Enable the pre-charge branch to pre-charge the flying capacitor with the input power supply.

[0065] After calculating the expected steady-state voltage VF in step S200, the pre-charge branch 200 is enabled, so that the input power supply pre-charges the flying capacitor Cfly through the pre-charge branch 200.

[0066] As described in the aforementioned embodiments, during the pre-charging process, the charging current flows from the input power supply Vin through the pre-charging branch 200 to the common node VS, then through the flying capacitor Cfly and the first winding L1 to the output terminal Vout, and finally flows back to the ground terminal through the output capacitor Co.

[0067] During the pre-charging process, as the voltage across the flying capacitor Cfly gradually increases, the potential of the common node VS also increases, the voltage difference between the input power supply Vin and the common node VS gradually decreases, and the charging current flowing through the pre-charging branch 200 decreases accordingly. This process will continue until the stop condition in step S400 is met.

[0068] Step S400: When the actual voltage of the flying capacitor reaches the expected steady-state voltage value, stop enabling the pre-charge branch and pre-bias the main power circuit.

[0069] During the pre-charging process of the flying capacitor Cfly in the pre-charging branch 200, the current actual voltage VFR of the flying capacitor Cfly is continuously acquired, and the actual voltage VFR is compared with the expected steady-state voltage VF calculated in step S200.

[0070] When the actual voltage VFR reaches the expected steady-state voltage VF, it is determined that the pre-charging of the flying capacitor Cfly has been completed. At this time, the pre-charging branch 200 is stopped, and the pre-bias duty cycle D calculated in step S100 is used as the start-up duty cycle to pre-bias start the main power circuit 100.

[0071] Pre-biased startup refers to starting the main power circuit 100 with a duty cycle D that matches the residual voltage, under the condition that there is already a certain voltage (i.e., residual voltage) at the output terminal of the main power circuit 100, in order to avoid large fluctuations in the output voltage at the moment of startup.

[0072] Continuing with the example data above: input voltage Vin = 48V, output voltage Vout = 16V, and expected steady-state voltage VF ≈ 20.3V. During the pre-charge process, the actual voltage VFR of the flying capacitor Cfly gradually increases from its initial value. When the actual voltage VFR reaches 20.3V, the pre-charge branch 200 is deactivated, and the main power circuit 100 is then started with a pre-bias duty cycle D ≈ 0.577.

[0073] Since the voltage of the flying capacitor Cfly has been precisely charged to a steady-state voltage that matches the current input and output conditions, the main power circuit 100 will not generate surge current due to the voltage deviation of the flying capacitor at the moment of startup, thus achieving smooth pre-bias startup.

[0074] The flying capacitor pre-charging method of this application calculates the pre-charging target voltage in segments based on the actual input and output voltages, adapting to different pre-bias start-up conditions. This solves the problem that traditional solutions can only charge to half the input voltage and cannot accurately control the pre-charging voltage. Furthermore, by monitoring the actual voltage of the flying capacitor in real time and comparing it with the expected steady-state voltage, pre-charging is immediately stopped and the main power circuit is started after the target voltage is reached. This achieves precise control of the pre-charging time and solves the problem that traditional solutions can only passively reserve a delay time to wait for the pre-charging to end.

[0075] As described in the aforementioned embodiments, the first end of the flying capacitor Cfly is connected to the common node VS, and the second end of the flying capacitor Cfly is connected to the drain of the fifth switch Q5 and the first end of the first winding L1.

[0076] Before the main power circuit 100 is started, all switching transistors are in the off state, and the main power circuit 100 is not working. At this time, the second terminal of the flying capacitor Cfly is connected to the output terminal through the first winding L1, and its potential is equal to the output voltage Vout. Therefore, the voltage across the flying capacitor Cfly is the difference between the potential of the common node VS and the output voltage Vout.

[0077] Based on the above analysis, obtaining the actual voltage VFR of the flying capacitor Cfly includes the following sub-steps: First, the node voltage of the common node of the flying capacitor Cfly and the precharge branch 200 is sampled, that is, the node voltage of the common node VS is sampled. In practical applications, the voltage of the common node VS can be stepped down by a resistor divider network and then sampled by an analog-to-digital converter (ADC) to obtain the value of the node voltage.

[0078] It should be noted that the voltage of the common node VS is referenced to the common ground GND. The sampling circuit design is simple. In actual switched capacitor converter systems, sampling circuits for the input voltage Vin and the output voltage Vout are usually already available. Therefore, only one sampling circuit for the common node VS needs to be added, without making significant modifications to the existing system.

[0079] Then, calculate the actual voltage VFR of the flying capacitor Cfly according to the following formula:

[0080] Where V1 is the node voltage of the common node, and Vout is the output voltage.

[0081] Continuing with the previous example data: input voltage Vin = 48V, output voltage Vout = 16V, and expected steady-state voltage VF ≈ 20.3V. Assuming that at a certain moment during the pre-charging process, the node voltage V1 of the common node is sampled as 30V, then the actual voltage VFR of the flying capacitor Cfly is 30V. 16 = 14V. At this time, the actual voltage VFR has not yet reached the expected steady-state voltage value VF≈20.3V, so the pre-charge branch 200 continues to work.

[0082] As pre-charging progresses, the node voltage V1 of the common node VS gradually increases. When V1 is sampled to be 36.3V, the actual voltage VFR is 36.3V. 16 = 20.3V. At this time, the actual voltage VFR has reached the steady-state voltage expected value VF, which satisfies the stop condition in step S400. The pre-charge branch 200 is stopped and the main power circuit 100 is pre-biased and started.

[0083] It should be noted that the above method of indirectly obtaining the actual voltage of the flying capacitor Cfly by sampling the node voltage V1 of the common node VS avoids the complexity of directly measuring the floating voltage across the flying capacitor Cfly. Since the common node VS references ground GND, its sampling circuit structure is simple and low in implementation cost, making it suitable for practical engineering applications.

[0084] In practical applications, the pre-charging process may encounter various abnormal operating conditions. If these are not detected and addressed, they may lead to device damage or system failure, including but not limited to abnormal flying capacitor voltage before the pre-charging branch is enabled. Therefore, the flying capacitor pre-charging method provided in this invention further includes the following steps before enabling the pre-charging branch: First, obtain the current actual voltage VFR of the flying capacitor Cfly. The actual voltage VFR is obtained as described in the previous embodiment by sampling the node voltage V1 of the common node VS, according to the formula VFR=V1. Vout is calculated.

[0085] After obtaining the actual voltage VFR, determine whether the actual voltage VFR is greater than or equal to the expected steady-state voltage value VF.

[0086] If the actual voltage VFR is less than the expected steady-state voltage VF, that is, the current voltage of the flying capacitor Cfly has not yet reached the pre-charge target, then the process proceeds normally to step S300, enabling the pre-charge branch 200 to pre-charge the flying capacitor Cfly.

[0087] If the actual voltage VFR is greater than the expected steady-state voltage VF, then it is further determined whether the first voltage difference between the actual voltage VFR and the expected steady-state voltage VF is greater than the preset first error.

[0088] The so-called first voltage difference refers to the absolute value of the difference between the actual voltage VFR and the expected steady-state voltage VF, that is, first voltage difference = |VFR| VF|.

[0089] The so-called first error refers to the maximum deviation range of the actual voltage of the flying capacitor Cfly from the expected steady-state voltage VF allowed by the system. This value can be set according to the withstand voltage margin of the devices and the system startup requirements in actual applications.

[0090] If the actual voltage VFR is equal to the expected steady-state voltage VF, or the first voltage difference is not greater than the first error, it indicates that the current voltage of the flying capacitor Cfly has reached or is close to the expected steady-state voltage VF, and the deviation is within a reasonable range. At this time, there is no need to precharge, and the main power circuit 100 is started directly with the pre-bias duty cycle D calculated in step S100.

[0091] This situation may occur when the system restarts after a brief shutdown. The flying capacitor Cfly still retains the residual voltage from the last operation, and this voltage happens to match the steady-state voltage required for the current operating conditions.

[0092] If the first voltage difference is greater than the first error, it indicates that the current voltage of the flying capacitor Cfly is much higher than the expected steady-state voltage VF, which exceeds the reasonable deviation range. The system may be abnormal, and the first abnormal signal will be output at this time.

[0093] The so-called first abnormal signal refers to the alarm signal sent by the upper-level controller or fault management module of the system to indicate an abnormal voltage state of the flying capacitor Cfly. Upon receiving the first abnormal signal, the system can execute corresponding protection strategies according to actual needs, such as disabling the main power circuit 100 from starting or entering fault protection mode.

[0094] Continuing with the previous example data: input voltage Vin = 48V, output voltage Vout = 16V, and expected steady-state voltage VF ≈ 20.3V. Assume the first error is set to 1V.

[0095] Example a: Sampling yields V1=30V, actual voltage VFR=30V. 16 = 14V, VFR is not greater than VF, so proceed normally to step S300 for pre-charging.

[0096] Example b: Sampling yields V1=37V, actual voltage VFR=37V. 16 = 21V, VFR > VF ≈ 20.3V, first voltage difference = |21 20.3|=0.7V, not greater than the first error of 1V, directly pre-biased to start the main power circuit 100.

[0097] Example c: Sampling yields V1=40V, actual voltage VFR=40V. 16 = 24V, VFR > VF ≈ 20.3V, first voltage difference = |24 20.3|=3.7V, which is greater than the first error of 1V, so the first abnormal signal is output.

[0098] The abnormal operating conditions encountered during the pre-charging process may also include abnormal node voltages before the pre-charging branch is enabled. In view of this, the flying capacitor pre-charging method provided in this embodiment of the invention further includes the following steps before enabling the pre-charging branch: Sample the node voltage V1 of the common node VS, determine whether the node voltage V1 is less than the output voltage Vout, and whether the second voltage difference between the node voltage V1 and the output voltage Vout is greater than the preset second error.

[0099] The so-called second voltage difference refers to the difference between the output voltage Vout and the node voltage V1, that is, the second voltage difference = Vout V1. The so-called second error refers to the maximum deviation range that the node voltage V1 can be below the output voltage Vout.

[0100] If the node voltage V1 is less than the output voltage Vout, and the second voltage difference is greater than the second error, then the second abnormal signal is output.

[0101] The principle behind this judgment is that when the main power circuit 100 is not working, the second terminal of the flying capacitor Cfly is connected to the output terminal via the first winding L1, and its potential is equal to Vout. The first terminal of the flying capacitor Cfly is connected to the common node VS. Under normal circumstances, the voltage VFR across the flying capacitor Cfly should be greater than or equal to zero, that is, the voltage at the common node VS should be greater than or equal to Vout.

[0102] If the node voltage V1 is much lower than Vout, it means that a reverse voltage has appeared across the flying capacitor Cfly, indicating that there may be an anomaly in the system, such as a short circuit in the flying capacitor Cfly, leakage, or an external circuit fault. At this time, a second abnormal signal is output, and the system executes the corresponding protection strategy.

[0103] Continuing with the previous example data: input voltage Vin = 48V, output voltage Vout = 16V. Assume the second error is set to 2V.

[0104] Example d: The sampled voltage is V1=30V, VS is greater than Vout=16V, the node voltage is normal, and no abnormality judgment is triggered.

[0105] Example e: Sampling yields V1=12V, VS is less than Vout=16V, the second voltage difference is 16. 12 = 4V, which is greater than the second error of 2V, so the second abnormal signal is output.

[0106] It should be noted that the aforementioned flying capacitor voltage anomaly detection and node voltage anomaly detection are both performed before the pre-charge branch 200 is enabled. In practical applications, the node voltage anomaly detection can be performed first, followed by the flying capacitor voltage anomaly detection, or both can be performed simultaneously or in any other order. This application does not limit the execution order of the two. Only when none of the above anomaly detections trigger an anomaly signal will the process proceed normally to step S300 to enable the pre-charge branch 200 for pre-charging.

[0107] The abnormal detection of flying capacitor voltage and node voltage before enabling the precharge branch can identify the abnormal state of the system before the precharge starts, avoiding blindly starting the precharge or main power circuit under abnormal conditions.

[0108] The pre-charging process may encounter abnormal operating conditions, including pre-charging timeout after the pre-charging branch is enabled. In view of this, the flying capacitor pre-charging method provided by the embodiments of the present invention further includes the following steps after enabling the pre-charging branch: When the actual voltage VFR of the flying capacitor Cfly fails to reach the expected steady-state voltage VF within a preset time threshold, a third abnormal signal is output.

[0109] The so-called time threshold refers to the maximum allowable duration of the pre-charging process preset by the system. This value can be calculated or set empirically based on the capacitance of the flying capacitor Cfly, the current limiting characteristics of the pre-charging branch 200, and the input and output voltage conditions.

[0110] The principle behind this judgment is that, during normal pre-charging, the voltage of the flying capacitor Cfly should continue to rise as the charging time progresses and reach the expected steady-state voltage value VF within a finite time.

[0111] If the actual voltage VFR fails to reach the expected steady-state voltage VF within the preset time threshold, there may be abnormalities such as open circuit or damage to components in the pre-charge branch 200, severe leakage of the flying capacitor Cfly, or poor contact in the charging circuit, which may prevent the pre-charge from being completed normally. In this case, a third abnormal signal is output, and the system executes the corresponding protection strategy to prevent the system from staying in the pre-charge stage for an extended period and failing to start normally.

[0112] Continuing with the previous example data: input voltage Vin = 48V, output voltage Vout = 16V, and expected steady-state voltage VF ≈ 20.3V. Assume the time threshold is set to 100ms.

[0113] Example f: After enabling the precharge branch 200, the actual voltage VFR of the flying capacitor Cfly rises from the initial value to 20.3V within 35ms, reaching the expected steady-state voltage VF, which does not exceed the time threshold of 100ms, and the normal execution of step S400 is performed.

[0114] Example g: After enabling the precharge branch 200, after 100ms, the actual voltage VFR of the flying capacitor Cfly only rises from the initial value to 10V, which does not reach the expected steady-state voltage value VF≈20.3V. This exceeds the time threshold, and the third abnormal signal is output.

[0115] Through the aforementioned three-tiered anomaly detection and protection mechanisms, the flying capacitor pre-charging method of this application can promptly detect and handle potential abnormal operating conditions at different stages of the pre-charging process. The timeout detection after enabling the pre-charging branch can detect faults in the pre-charging circuit itself, preventing the system from waiting indefinitely for pre-charging to complete. These anomaly detection mechanisms solve the problem that traditional open-loop pre-charging schemes cannot handle abnormal operating conditions such as pre-charging circuit failure, thus enhancing the reliability and safety of the system.

[0116] Please see Figure 4 , Figure 4 This is another structural schematic diagram of a switched capacitor converter provided for an embodiment of the present invention. Referring to the foregoing embodiments... Figure 2 The switched-capacitor converter described above only shows the main power circuit 100 and the pre-charge branch 200 to illustrate the application of the pre-charge method. This embodiment further introduces a pre-charge control module 300 to form a complete switched-capacitor converter architecture, illustrating the specific hardware implementation of the pre-charge method described in the foregoing embodiments.

[0117] like Figure 4 As shown, the switched capacitor converter includes a main power circuit 100, a precharge branch 200, and a precharge control module 300. The topology of the main power circuit 100 and the connection relationships of its components are as described in the previous embodiments and will not be repeated here. The precharge branch 200 is connected between the input power supply and the common node VS, and its connection relationship and function are as described in the previous embodiments and will not be repeated here.

[0118] The so-called precharge control module refers to the control unit used to execute the precharge control logic described in the aforementioned embodiments. It calculates the expected steady-state voltage VF of the flying capacitor Cfly by collecting the input voltage Vin, the output voltage Vout, and the node voltage V1 of the common node VS, and controls the on / off state of the precharge branch 200 based on the comparison between the actual voltage VFR of the flying capacitor Cfly and the expected steady-state voltage VF.

[0119] The input terminals of the precharge control module 300 are connected to the input power supply, the common node VS, and the first terminal of the output capacitor Co, respectively. Specifically, the first input terminal of the precharge control module 300 is connected to the input power supply and is used to acquire the input voltage Vin.

[0120] The second input terminal of the precharge control module 300 is connected to the common node VS, which is the connection node between the source of the first switch Q1 and the drain of the second switch Q2, and is used to collect the node voltage V1 of the common node VS.

[0121] The third input terminal of the precharge control module 300 is connected to the first terminal of the output capacitor Co, and is used to acquire the output voltage Vout. The output terminal of the precharge control module 300 is connected to the control terminal of the precharge branch 200, and is used to output a control signal to control the on / off state of the precharge branch 200.

[0122] First, the precharge control module 300 collects the input voltage Vin and the output voltage Vout through the first input terminal and the third input terminal respectively, calculates the pre-bias duty cycle D according to the method described in step S100, and then calculates the steady-state voltage expected value VF of the flying capacitor Cfly according to the method described in step S200.

[0123] Then, the precharge control module 300 acquires the node voltage V1 of the common node VS through the second input terminal, according to the formula Calculate the actual voltage VFR of the flying capacitor Cfly.

[0124] Before enabling the precharge branch 200, the precharge control module 300 executes the abnormal judgment logic described in the aforementioned embodiments, including abnormal judgment of the voltage of the flying capacitor Cfly and abnormal judgment of the voltage of the common node VS node.

[0125] If no abnormal signal is triggered by any abnormality judgment, the precharge control module 300 outputs an enable signal to the control terminal of the precharge branch 200 through the output terminal, enabling the precharge branch 200 to precharge the flying capacitor Cfly.

[0126] During the pre-charging process, the pre-charging control module 300 continuously collects the node voltage V1 of the common node VS and calculates the actual voltage VFR, comparing it with the expected steady-state voltage VF. Simultaneously, the pre-charging control module 300 performs the pre-charging timeout judgment described in the aforementioned embodiment.

[0127] When the actual voltage VFR reaches the expected steady-state voltage VF, the pre-charge control module 300 stops outputting an enable signal to the pre-charge branch 200, the pre-charge branch 200 is turned off, and then the main power circuit 100 is pre-biased and started. During the normal operation of the main power circuit 100, the pre-charge control module 300 never outputs an enable signal to the pre-charge branch 200, the pre-charge branch 200 remains closed, and the normal operation of the main power circuit 100 is not affected.

[0128] It should be noted that the precharge control module 300 can be implemented in various hardware forms in practical applications. In one embodiment, the precharge control module 300 may include an analog-to-digital converter (ADC) sampling module and a digital control logic module. After the input voltage Vin, output voltage Vout, and node voltage V1 of the common node VS are stepped down by a resistor divider network, they are digitized by the ADC sampling module. The digital control logic module executes the precharge control logic and anomaly judgment logic in the aforementioned embodiments on the sampling results, and controls the on / off state of the precharge branch 200 through the output terminal.

[0129] In practical switched capacitor converter systems, sampling circuits for the input voltage Vin and the output voltage Vout are usually already in place. Therefore, only one sampling circuit for the common node VS needs to be added, and the hardware modification is minimal.

[0130] In another embodiment, the precharge control module 300 may include an analog-to-digital converter (ADC) sampling module, a digital-to-analog converter (DAC) module, and an analog comparator. After sampling the input voltage Vin and output voltage Vout through the ADC sampling module, the precharge control module 300 calculates the expected steady-state voltage VF using digital control logic, and generates multiple sets of analog threshold voltages corresponding to the expected steady-state voltage VF through the DAC module. These threshold voltages correspond to the precharge completion threshold, the flying capacitor Cfly overvoltage threshold, and the undervoltage threshold, respectively.

[0131] The aforementioned threshold voltages are compared with the node voltage of the common node VS using an analog comparator. The comparator's output signal is directly used for the on / off control of the precharge branch 200 and the generation of abnormal signals. In this embodiment, the voltage of the common node VS does not need to be sampled by an ADC but directly participates in the analog comparison, resulting in a faster response speed.

[0132] Please see Figure 5 , Figure 5 A circuit schematic diagram of a pre-charge branch 200 provided for an embodiment of the present invention is shown below. Figure 5As shown, the pre-charge branch 200 includes a third switch Q3, a fourth switch Q4, a first diode D1, a current-limiting resistor R1, a first bias resistor R2, and a second bias resistor R3. The third switch Q3 is a PNP transistor, and the fourth switch Q4 is an NMOS field-effect transistor.

[0133] In this configuration, the collector of the third switch Q3 is connected to the input power supply Vin and the first terminal of the first bias resistor R2. The base of the third switch Q3 is connected to the second terminal of the first bias resistor R2 and the first terminal of the second bias resistor R3. The second terminal of the second bias resistor R3 is connected to the drain of the fourth switch Q4. The gate of the fourth switch Q4 is connected to the output terminal of the precharge control module 300 to receive the control signal output by the precharge control module 300. The source of the fourth switch Q4 is grounded. The emitter of the third switch Q3 is connected to the anode of the first diode D1. The cathode of the first diode D1 is connected to the first terminal of the current-limiting resistor R1. The second terminal of the current-limiting resistor R1 is connected to the common node VS.

[0134] When the precharge control module 300 outputs a high-level control signal to the gate of the fourth switch Q4, the fourth switch Q4 is turned on, and its drain is pulled low to near ground potential. At this time, current flows from the input power supply Vin through the first bias resistor R2, the second bias resistor R3, and the fourth switch Q4 to ground. The base voltage of the third switch Q3 is determined by the voltage division of the first bias resistor R2 and the second bias resistor R3, and is pulled low to a level far below the input voltage Vin.

[0135] Since the third switch Q3 is a PNP transistor, its base voltage is lower than its emitter voltage, the emitter junction of the third switch Q3 is forward biased, and the third switch Q3 is turned on.

[0136] The charging current path is as follows: the input power supply Vin flows to the third switch Q3 (collector to emitter), then through the first diode D1 (anode to cathode), the current limiting resistor R1, the common node VS, the flying capacitor Cfly, and the first winding L1 to the output terminal Vout and the output capacitor Co, and finally to the ground terminal GND.

[0137] When the precharge control module 300 outputs a low-level control signal, the fourth switch Q4 is turned off. No current flows through the second bias resistor R3, and the base of the third switch Q3 is pulled to the input voltage Vin potential through the first bias resistor R2. The base and collector are at the same potential, the emitter junction of the third switch Q3 is zero biased, the third switch Q3 is turned off, and the charging current path is disconnected.

[0138] In the above circuit structure, the third switch Q3 serves as the main power switch device of the pre-charge branch 200, controlling the on / off state of the charging current path. The fourth switch Q4 acts as the driving switch for the third switch Q3, converting the low-voltage control signal output by the pre-charge control module 300 into a drive for the third switch Q3. The first bias resistor R2 and the second bias resistor R3 form a bias network, used to provide a suitable bias voltage to the base of the third switch Q3 when the fourth switch Q4 is turned on, and to restore the base potential of the third switch Q3 to the input voltage Vin when the fourth switch Q4 is turned off.

[0139] The first diode D1 provides unidirectional conduction, ensuring that the charging current can only flow from the input power supply Vin to the common node VS, preventing the voltage of the common node VS from backflowing to the input power supply Vin through the precharge branch 200 during the operation of the main power circuit 100. The current-limiting resistor R1 is used to limit the amplitude of the charging current during the precharge process, preventing damage to the device from transient large currents.

[0140] It should be noted that since the pre-charge branch 200 does not have high requirements for the pre-charge current, power devices such as the third switch Q3 and the first diode D1 can be implemented using devices with smaller current specifications, which helps to reduce the size of the devices and the PCB area occupied.

[0141] However, since the precharge branch 200 is connected between the input power supply Vin and the common node VS, the third switch Q3 and the first diode D1 need to withstand the voltage difference between the input voltage Vin and the common node VS in the off state. Therefore, in the actual design, it is necessary to select devices with sufficient reverse cutoff voltage withstand capability.

[0142] Continuing with the example data above: input voltage Vin = 48V, output voltage Vout = 16V, and expected steady-state voltage VF ≈ 20.3V. At the start of pre-charging, the voltage at the common node VS is low, the voltage difference between the input power supply Vin and the common node VS is large, and the charging current flowing through the current-limiting resistor R1 is large.

[0143] As precharging progresses, the voltage across the flying capacitor Cfly gradually increases, and the voltage at the common node VS also increases accordingly. The voltage difference between the input power supply Vin and the common node VS gradually decreases, and the charging current decreases accordingly. When the actual voltage VFR of the flying capacitor Cfly reaches the expected steady-state voltage VF≈20.3V, that is, when the voltage at the common node VS reaches VF+Vout=20.3+16=36.3V, the precharge control module 300 outputs a low-level control signal, the fourth switch Q4 is turned off, the third switch Q3 is turned off, and the precharge branch 200 stops working.

[0144] In other embodiments, the third switch Q3 can be replaced with other types of controllable switching devices, such as PMOS field-effect transistors; the first diode D1 can also be replaced with other devices with unidirectional conduction characteristics. This application does not limit the specific types of each device in the precharge branch 200, as long as it can realize the function of providing unidirectional controllable charging current from the input power supply Vin to the flying capacitor Cfly under the control of the precharge control module 300.

[0145] Please see Figure 6 , Figure 6 The pre-charging process waveform of the switched capacitor converter provided in the embodiment of the present invention is shown. Figure 6 The data from top to bottom shows the time-varying relationships of four waveforms: the actual voltage of the flying capacitor Cfly, the output voltage Vout, the pre-charge drive pulse, and the pre-charge current.

[0146] In this scheme, the precharge control module 300 outputs a soft-start pulse signal to the gate of the fourth switch Q4 at a fixed frequency, driving the third switch Q3 to work periodically in the saturation region, thereby enabling the precharge branch 200 to precharge the flying capacitor Cfly in a pulse manner.

[0147] The so-called soft-start pulse refers to a periodic pulse signal with a fixed frequency and a certain duty cycle output by the pre-charge control module 300. This pulse signal causes the third switch Q3 to alternately turn on and off in each pulse cycle, thereby transforming the continuous charging process into an intermittent pulse charging process. The third switch Q3 operates in the saturation region, meaning that during each pulse conduction period, the collector current of the third switch Q3 is mainly determined by the current-limiting resistor R1 and the input-output voltage difference. The third switch Q3 itself is in a fully conducting state, and the voltage drop between its collector and emitter is small.

[0148] from Figure 6 As can be seen from the waveform, the actual voltage of the flying capacitor Cfly gradually increases in a stepwise manner from its initial value as the pre-charge pulse continues. During the conduction period of each drive pulse, the charging current flows from the input power supply Vin through the pre-charge branch 200 to the flying capacitor Cfly, causing a slight increase in the voltage of the flying capacitor Cfly. During the turn-off period of the drive pulse, the charging current is zero, and the voltage of the flying capacitor Cfly remains unchanged. This process repeats, and the voltage of the flying capacitor Cfly gradually increases in a stepwise manner until it reaches the expected steady-state voltage value VF.

[0149] The output voltage Vout rises slowly and synchronously during the pre-charging process. This is because the pre-charging current path flows to the output terminal through the flying capacitor Cfly and the first winding L1, charging the output capacitor Co, which causes the output voltage Vout to increase slightly as well.

[0150] The pre-charge current is relatively large in the initial stage of pre-charge and gradually decreases as the pre-charge process progresses. This is because in the initial stage of pre-charge, the voltage difference between the input power supply Vin and the common node VS is large, resulting in a large current flowing through the current-limiting resistor R1. As the voltage of the flying capacitor Cfly gradually increases, the potential of the common node VS also increases, the voltage difference between the input power supply and the common node gradually decreases, and the amplitude of the charging current during each pulse conduction period also decreases accordingly.

[0151] Please see Figure 7 , Figure 7 The pre-charging process waveform of the switched capacitor converter provided in the embodiment of the present invention is shown. Figure 7 for Figure 6 The magnified waveform of the pre-charging process nearing its end allows for a clearer observation of the impact of a single drive pulse on various electrical quantities.

[0152] from Figure 7 The unfolded waveform shows that as pre-charging nears completion, the actual voltage of the flying capacitor Cfly is close to the expected steady-state voltage VF, with only a small voltage increment during each drive pulse. The output voltage Vout exhibits a small step increase during each pulse. The pre-charge drive pulse maintains a fixed frequency and duty cycle. The pre-charge current presents as a current pulse during each pulse, with its amplitude significantly reduced compared to the initial pre-charge stage, reflecting a substantial decrease in the voltage difference between the input power supply and the common node.

[0153] When the precharge control module 300 detects that the actual voltage VFR of the flying capacitor Cfly reaches the expected steady-state voltage VF, the precharge control module 300 stops outputting drive pulses, the precharge branch 200 is turned off, and then the pre-biased main power circuit 100 is started.

[0154] Pulse charging breaks down the continuous charging process into multiple short charging pulses. The charging current during each pulse is limited by a current-limiting resistor, effectively avoiding the impact of continuous high current on the device and reducing its thermal stress. Furthermore, the intermittent charging method facilitates the pre-charge control module in sampling the actual voltage of the flying capacitor during pulse intervals, enabling precise monitoring of the pre-charge voltage.

[0155] In another embodiment, the precharge control module 300 can also precharge the flying capacitor Cfly by controlling the third switch Q3 to operate in the linear amplification region.

[0156] Unlike the previous embodiment where the third switch Q3 operates in the saturation region, in this embodiment, the pre-charge control module 300 adjusts the gate voltage of the fourth switch Q4 to control the base current of the third switch Q3, thereby controlling the third switch Q3 to operate in the linear amplification region. At this time, the collector current of the third switch Q3 is controlled by the base current, and the magnitude of the charging current can be actively adjusted by the pre-charge control module 300, rather than being passively determined solely by the current-limiting resistor R1 and the voltage difference.

[0157] Using a linear amplification region drive method, the precharge control module 300 can dynamically adjust the charging current based on the difference between the actual voltage VFR of the flying capacitor Cfly and the expected steady-state voltage VF. For example, when the voltage difference is large in the early stage of precharge, a larger charging current can be controlled to speed up the precharge process; when the voltage difference is small near the end of precharge, the charging current can be reduced to improve the accuracy of the precharge voltage.

[0158] It should be noted that both of the above-mentioned pre-charge power control schemes can be applied to the pre-charge methods described in the foregoing embodiments. In practical applications, a suitable power control scheme can be selected based on the specific requirements of the system regarding pre-charge speed, voltage accuracy, control complexity, etc. This application does not limit the power control method of the pre-charge branch 200, as long as it can achieve controllable pre-charge of the flying capacitor Cfly under the control of the pre-charge control module 300.

[0159] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for pre-charging a flying capacitor, applied to a switched capacitor converter including a main power circuit and a pre-charging branch, wherein the main power circuit includes a flying capacitor, and the pre-charging branch is connected between the input power supply and the flying capacitor, characterized in that, The method includes the following steps: Calculate the pre-bias duty cycle based on the input and output voltages of the main power circuit; The expected steady-state voltage of the flying capacitor is calculated based on the pre-bias duty cycle. Enable the pre-charge branch so that the input power supply pre-charges the flying capacitor; When the actual voltage of the flying capacitor reaches the expected steady-state voltage value, the pre-charge branch is stopped from being enabled and the main power circuit is pre-biased and started.

2. The method according to claim 1, characterized in that, The step of calculating the pre-bias duty cycle based on the input and output voltages of the main power circuit specifically includes the following steps: The input voltage and the output voltage are acquired. Calculate the ratio parameter using the following formula: Among them, V OUT V is the input voltage. IN The output voltage; When the ratio parameter is greater than a preset threshold, the pre-offset duty cycle is calculated according to the following formula: When the ratio parameter is less than or equal to the preset threshold, the pre-bias duty cycle is calculated according to the following formula: 。 3. The method according to claim 2, characterized in that, The step of calculating the expected steady-state voltage of the flying capacitor based on the pre-bias duty cycle specifically includes the following steps: When the ratio parameter is greater than the preset threshold, the expected steady-state voltage value is calculated according to the following formula: When the ratio parameter is less than or equal to the preset threshold, the expected steady-state voltage value is calculated according to the following formula: 。 4. The method according to claim 1, characterized in that, When the actual voltage of the flying capacitor reaches the expected steady-state voltage value, the pre-charge branch is stopped from being enabled and the main power circuit is started. This specifically includes the following steps: Obtain the actual voltage; Determine whether the actual voltage is greater than or equal to the expected steady-state voltage value; If so, then disable the precharge branch and pre-bias the main power circuit.

5. The method according to claim 1, characterized in that, Before enabling the pre-charge branch to pre-charge the flying capacitor using the input power supply, the method further includes: Obtain the actual voltage; Determine whether the actual voltage is greater than or equal to the expected steady-state voltage value; If the actual voltage is greater than the expected steady-state voltage, then determine whether the first voltage difference between the actual voltage and the expected steady-state voltage is greater than a preset first error; If the actual voltage is equal to the expected steady-state voltage, or the first voltage difference is not greater than the first error, then the main power circuit is directly pre-biased and started. If the first voltage difference is greater than the first error, then the first abnormal signal is output.

6. The method according to claim 4 or 5, characterized in that, The process of obtaining the actual voltage specifically includes the following steps: Sample the node voltage of the common node of the flying capacitor and the pre-charge branch; The actual voltage is calculated using the following formula: Wherein, V1 is the node voltage.

7. The method according to claim 1, characterized in that, Before enabling the pre-charge branch to pre-charge the flying capacitor using the input power supply, the method further includes: Sample the node voltage of the common node of the flying capacitor and the pre-charge branch; Determine whether the node voltage is less than the output voltage, and whether the second voltage difference between the node voltage and the output voltage is greater than a preset second error; If the second voltage difference is greater than the second error, then a second abnormal signal is output.

8. The method according to claim 1, characterized in that, After enabling the pre-charge branch to pre-charge the flying capacitor using the input power supply, the method further includes: When the actual voltage fails to reach the expected steady-state voltage value within a preset time threshold, a third abnormal signal is output.

9. A switched-capacitor converter, characterized in that, include: The main power circuit includes a first switching transistor, a second switching transistor, a fifth switching transistor, a sixth switching transistor, a flying capacitor, a coupling inductor, an output capacitor, and a load resistor; Wherein, the drain of the first switching transistor is connected to the input power supply, the source of the first switching transistor is connected to the drain of the second switching transistor to form a common node, the first end of the flying capacitor is connected to the common node, the second end of the flying capacitor is connected to the drain of the fifth switching transistor and the first end of the first winding of the coupling inductor, and the source of the fifth switching transistor is grounded. The source of the second switching transistor is connected to the drain of the sixth switching transistor and the first end of the second winding of the coupling inductor. The source of the sixth switching transistor is grounded. The second end of the first winding and the second end of the second winding of the coupling inductor are connected to the first end of the output capacitor and the first end of the load resistor. The second end of the output capacitor and the second end of the load resistor are grounded. A pre-charge branch is connected between the input power supply and the common node; The precharge control module has its input terminals connected to the input power supply, the common node, and the first terminal of the output capacitor, respectively, and its output terminal connected to the control terminal of the precharge branch. The precharge control module is configured to calculate the expected steady-state voltage of the flying capacitor based on the input voltage and output voltage of the main power circuit, and control the on / off state of the precharge branch based on the actual voltage of the flying capacitor and the expected steady-state voltage.

10. The switched capacitor converter according to claim 9, characterized in that, The precharge branch includes a third switch, a fourth switch, a first diode, a current-limiting resistor, a first bias resistor, and a second bias resistor; The collector of the third switch is connected to the input power supply and the first end of the first bias resistor, the base of the third switch is connected to the second end of the first bias resistor and the first end of the second bias resistor, and the second end of the second bias resistor is connected to the drain of the fourth switch. The gate of the fourth switch is connected to the output terminal of the precharge control module, the source of the fourth switch is grounded, the emitter of the third switch is connected to the anode of the first diode, the cathode of the first diode is connected to the first terminal of the current limiting resistor, and the second terminal of the current limiting resistor is connected to the common node.

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