Buck converter circuit with flying capacitor
By introducing a pre-charge switch and control system into the buck converter circuit, flying capacitor charging without additional components is achieved, solving the problems of system complexity and high cost in traditional methods, improving charging efficiency and reducing energy loss.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ABB E-MOBILITY BV
- Filing Date
- 2025-12-11
- Publication Date
- 2026-06-16
AI Technical Summary
Traditional buck converter circuits require an additional active converter to charge the flying capacitor, which increases system complexity and cost.
By employing a pre-charge switch and control system, a charging process without additional components is achieved through a series-connected switching element and a flying capacitor. The flying capacitor is alternately charged and discharged using the pre-charge process and the cyclic conversion process, thereby reducing the voltage difference of the switching element.
It reduces production costs and circuit system complexity, improves charging efficiency, reduces energy loss, and enables the use of switching elements with low voltage ratings.
Smart Images
Figure CN122225835A_ABST
Abstract
Description
Technical Field
[0001] This technical field relates to power electronic converters based on flying capacitor topologies. More specifically, this technical field relates to buck converter circuits including flying capacitors and methods for operating the flying capacitors in the buck converter circuits. Background Technology
[0002] Traditionally, buck converter circuits are used to reduce the voltage supplied by a voltage supply device to a user-defined output voltage. The output voltage is then used, for example, in connected circuitry. One buck converter circuit includes multiple switching elements. Flying capacitors can be used to reduce the voltage difference across the switching elements.
[0003] In this scenario, the flying capacitor must be charged before the buck converter circuit can supply the user-defined output voltage. Traditionally, the flying capacitor is charged via an additional converter regulated by a constant current controller. However, this requires an additional active converter consisting of semiconductors, inductors, capacitors, drivers, controllers, and protection logic. Summary of the Invention
[0004] According to aspects of this disclosure, the buck converter circuit includes a precharge switch, switching elements Q1, Q2, Q3, and Q4, a flying capacitor, a voltage supply node, a first flying capacitor node, a second flying capacitor node, a switching node, and a control system.
[0005] The voltage supply node, pre-charge switch, and first flying capacitor node are connected in series sequentially. The voltage supply node, switching element Q1, and first flying capacitor node are connected in series sequentially. The first flying capacitor node, flying capacitor, second flying capacitor node, and switching element Q4 are connected in series sequentially. The first flying capacitor node, switching element Q2, switching node, switching element Q3, and second flying capacitor node are connected in series sequentially. An input voltage V is supplied at the voltage supply node. in .
[0006] The control system is configured to perform the pre-charge process and the cycle switching process. During the pre-charge process, the control system controls the pre-charge switch and the switching element Q4 to turn on. This builds up a voltage difference in the flying capacitor.
[0007] The cyclic switching process includes alternating charging and discharging steps for cyclically discharging and charging the flying capacitor. During the cyclic switching process, the control system controls the pre-charge switch to be isolated when switching element Q1 is isolated. The cyclic switching process also includes charging and discharging steps. During the charging step of the cyclic switching process, the control system controls switching elements Q1 and Q3 to be turned on, and controls switching elements Q2 and Q4 to be isolated, to charge the flying capacitor. During the discharging step of the cyclic switching process, the control system controls switching elements Q2 and Q4 to be turned on, and controls switching elements Q1 and Q3 to be isolated, to discharge the flying capacitor.
[0008] According to aspects of this disclosure, the buck converter circuit includes a precharge switch, switching elements Q1, Q2, Q3, and Q4, a flying capacitor, a voltage supply node, a first flying capacitor node, a second flying capacitor node, a switching node, and a control system.
[0009] The voltage supply node, pre-charge switch, and first flying capacitor node are connected in series sequentially. The voltage supply node, switching element Q1, and first flying capacitor node are connected in series sequentially. The first flying capacitor node, flying capacitor, second flying capacitor node, and switching element Q4 are connected in series sequentially. The first flying capacitor node, switching element Q2, switching node, switching element Q3, and second flying capacitor node are connected in series sequentially.
[0010] Methods for operating the flying capacitor in a buck converter circuit include: supplying an input voltage V at the voltage supply node. in Perform a pre-charge process to build a voltage difference in the flying capacitor; and perform a cyclic conversion process.
[0011] The pre-charge process involves controlling the pre-charge switch and turning on the switching element Q4 to establish a voltage difference in the flying capacitor. The cyclic conversion process includes alternating charge and discharge steps for cyclic discharge and charge of the flying capacitor.
[0012] The cyclic conversion process includes: when switching element Q1 is isolated, controlling the pre-charge switch to be isolated; during the charging step of the cyclic conversion process, controlling switching elements Q1 and Q3 to be turned on, and controlling switching elements Q2 and Q4 to be isolated, to charge the flying capacitor; during the discharging step of the cyclic conversion process, controlling switching elements Q2 and Q4 to be turned on, and controlling switching elements Q1 and Q3 to be isolated, to discharge the flying capacitor.
[0013] According to aspects of this disclosure, only a pre-charge switch may be needed to charge the flying capacitor. Optionally, a pre-charge switch may be included before the pre-charge switch. Additional electrical components may not be required. The buck converter circuit may include an isolated electrical connection from the voltage supply device to the flying capacitor and a ground connection. In particular, the buck converter circuit may include an isolated electrical connection from the voltage supply device to the flying capacitor. This reduces manufacturing costs, circuit complexity, control system complexity, and / or efficiency.
[0014] According to aspects of this disclosure, the precharge switch may specifically include a switching element. For example, the precharge switch may include a solid-state switch, a transistor, a semiconductor transistor, a logic gate, a bipolar junction transistor, a metal-oxide-semiconductor field-effect transistor (MOSFET), an analog switch, an electromechanical relay, a power transistor, an insulated-gate bipolar transistor, a silicon controlled rectifier, an AC-6b rated contactor, or a power MOSFET.
[0015] According to aspects of this disclosure, the voltage difference across most (optionally all) switching elements can be reduced. The voltage difference constructed in the flying capacitor can reduce the voltage difference across most (optionally all) switching elements. The voltage difference can be converted from the input voltage V. in Reduce to input voltage V in Subtract the voltage difference built up in the flying capacitor. Alternatively, the voltage difference can be reduced to the voltage difference built up in the flying capacitor. This allows the use of switching elements with lower voltage ratings. Alternatively, this allows the use of switching elements with voltage ratings lower than the input voltage V. in Switching elements Q1, Q2, Q3, and Q4 have power ratings. A pre-charge resistor allows for the use of switching elements with a voltage lower than the input voltage V. in The pre-charge switch with the power rating.
[0016] According to aspects of this disclosure, the voltage difference built up in the flying capacitor can be measured throughout the pre-charge process. This can allow the controller to terminate the pre-charge process and / or react to irregularities. It can also allow the voltage difference built up in the flying capacitor at the start of the pre-charge process to determine whether the pre-charge process is necessary.
[0017] According to aspects of this disclosure, the voltage difference built up in the flying capacitor can be measured throughout the cycle conversion process. This allows the controller to monitor the voltage difference built up in the flying capacitor. If the measured voltage difference built up is too low and / or reacts to irregularities, the controller can restart the pre-charge process. Furthermore, this allows the voltage difference built up in the flying capacitor to be measured at the beginning of the cycle conversion process to determine if a pre-charge process is needed.
[0018] According to aspects of this disclosure, the duration of the pre-charging process can be reduced. The isolated electrical connection between the voltage supply device and the flying capacitor allows for the use of an input voltage V. in The flying capacitor is continuously charged. Optionally, the isolated electrical connection between the voltage supply device and the flying capacitor allows for charging with an input voltage V. in The flying capacitor is continuously charged after subtracting the voltage drop caused by the pre-charge resistor.
[0019] According to aspects of this disclosure, the efficiency of the pre-charging process can be improved. The isolated electrical connection between the voltage supply device and the flying capacitor allows for the use of an input voltage V. in The flying capacitor is continuously charged. No energy may be lost in other electrical components. Alternatively, energy may be lost only in the electrical connections, pre-charge switches, and / or pre-charge resistors.
[0020] According to aspects of this disclosure, a switching element can be controlled to be on or isolated. Optionally, multiple components can be combined in a single switching element. For example, switching elements A and B connected in series can be interpreted as a single switching element. If switching elements A and B are on, then the single switching element in this example will be on, and if switching elements A and / or B are isolated, then the single switching element in this example will be isolated. Examples of switching elements can be solid-state switches, transistors, semiconductor transistors, logic gates, bipolar junction transistors, metal-oxide-semiconductor field-effect transistors (MOSFETs), analog switches, electromechanical relays, power transistors, insulated-gate bipolar transistors, silicon controlled rectifiers, AC-6b rated contactors, and / or power MOSFETs.
[0021] According to aspects of this disclosure, the precharge switch may be a switching element.
[0022] According to aspects of this disclosure, a node can be an electrical connection. A node can connect at least two electrical components. Alternatively, a node can be understood as an electrical connection of multiple electrical components. Electrical components can be capacitors, resistors, inductors, switching elements, any other electrical components and / or combinations thereof.
[0023] According to aspects of this disclosure, the control system can be implemented in a microcontroller, by means of an analog hardware circuit system, in a digital signal processor, any other processor, and / or a combination thereof.
[0024] According to an aspect of this disclosure, the control system may have a memory containing program code that, when executed by the control system, executes the corresponding method steps configured for use by the control system.
[0025] According to aspects of this disclosure, if electrical component A is electrically connected to electrical component C via electrical component B, then electrical components A, B, and C are connected in series sequentially. An electrical connection can be interpreted as a connection that allows current to flow at least once. For example, an electrical connection may include wires, capacitors, resistors, inductors, switching elements, any other electrical components, and / or combinations thereof. For example, electrical component A may be connected to electrical component B by means of wires and / or switching elements and / or any other electrical components.
[0026] According to aspects of this disclosure, a pre-charge process can be performed to charge the flying capacitor. For example, initially no voltage difference is established in the flying capacitor and / or a voltage difference that is too low is established. Therefore, a pre-charge process is performed to charge the flying capacitor before the cycle conversion process. The pre-charge process terminates once the pre-charge conditions are met. The pre-charge conditions may include, for example, that the voltage difference established in the flying capacitor exceeds a predetermined pre-charge voltage, and / or a predetermined pre-charge time or integral current exceeds a corresponding threshold.
[0027] According to aspects of this disclosure, the cyclic switching process can supply an AC voltage level at the switching node.
[0028] According to aspects of this disclosure, the buck converter circuit may further include a pre-charge resistor. The voltage supply node, the pre-charge resistor, and the pre-charge switch are connected in series sequentially. Advantageously, the pre-charge resistor can reduce the voltage difference across the pre-charge switch. Optionally, the pre-charge resistor can reduce the voltage difference across the pre-charge switch to the input voltage V. in 50%.
[0029] According to aspects of this disclosure, the control system may include a voltage measuring device for measuring the voltage difference built up in the flying capacitor. The control system may be configured to terminate the pre-charging process once the measured voltage difference built up in the flying capacitor exceeds a predetermined pre-charging voltage threshold. Optionally, the pre-charging voltage threshold is the input voltage V. in 50%.
[0030] According to aspects of this disclosure, the voltage measuring device may be a voltmeter connected in parallel with a flying capacitor. For example, the voltmeter may be connected to a first flying capacitor node and also to a second flying capacitor node connected in parallel with the flying capacitor.
[0031] According to aspects of this disclosure, the buck converter circuit may further include an inductor, a capacitor, an output node, and a ground connection. The second flying capacitor node, the switching element Q4, and the ground connection may be connected in series sequentially. Alternatively, the buck converter circuit may further include an output resistor. The output node, the output resistor, and the ground connection may be connected in series sequentially.
[0032] According to aspects of this disclosure, at least two of the ground connections in the buck converter circuit can be connected to a ground node. The ground node can be connected to a ground connection. Optionally, all ground connections of the buck converter circuit can be connected to a ground node.
[0033] According to aspects of this disclosure, the buck converter circuit can provide a user-defined output voltage V at the output node. out During the cyclic conversion process, the controller can perform pulse width modulation to adjust the input voltage V. in Reduce to the user-defined output voltage V out .
[0034] According to aspects of this disclosure, the cyclic conversion process may include at least sequentially repeated charging steps, intermediate steps, discharging steps, and intermediate steps.
[0035] According to aspects of this disclosure, pulse width modulation can define the duty cycle. For a duty cycle less than 0.5, during an intermediate step of the cyclic switching process, switching elements Q3 and Q4 can be configured to be on, and switching elements Q1 and Q2 can be configured to be isolated. For a duty cycle greater than 0.5, during an intermediate step of the cyclic switching process, switching elements Q1 and Q2 can be configured to be on, and switching elements Q3 and Q4 can be configured to be isolated.
[0036] According to aspects of this disclosure, the duty cycle can be determined by the output voltage V. out Divide by the input voltage V in The duty cycle can be defined as follows: Alternatively, it can be defined as a portion of a cycle in which the cyclic switching process is in a charging or discharging phase. Alternatively, the duty cycle can be defined as a portion of a cycle in which the flying capacitor is conductively connected to the switching node.
[0037] According to aspects of this disclosure, during the pre-charging process, the control system can control switching elements Q1, Q2, and Q3 to be isolated.
[0038] According to aspects of this disclosure, the control system can control switching elements Q1, Q2, Q3 and Q4 during a cyclic switching process.
[0039] According to aspects of this disclosure, the control system can be configured to restart the pre-charge process. The control system can restart the pre-charge process if the measured voltage difference built up in the flying capacitor is outside the tolerance range. Alternatively, the control system can restart the pre-charge process if the maximum measured voltage difference built up in the flying capacitor during one or more cycles is outside the tolerance range.
[0040] According to aspects of this disclosure, the tolerance range can be defined as a variation of 15%, optionally 10%, or more preferably 5% of the pre-charge voltage.
[0041] According to aspects of this disclosure, the buck converter circuit can be a multilevel buck converter circuit including at least one flying capacitor. Optionally, the multilevel buck converter circuit may have a flying capacitor for each level.
[0042] According to aspects of this disclosure, the method for operating the flying capacitor in a buck converter circuit can be performed by a buck converter circuit according to any buck converter circuit according to this disclosure. Alternatively, the method for operating the flying capacitor in a buck converter circuit can be performed by a buck converter circuit according to any embodiment of the buck converter circuit described herein.
[0043] According to aspects of this disclosure, the method may further include measuring the voltage difference built up in the flying capacitor during the pre-charging process. Optionally, the method may further include terminating the pre-charging process once the measured voltage difference built up in the flying capacitor exceeds a predetermined pre-charging voltage threshold.
[0044] According to aspects of this disclosure, the method may further include providing a user-defined output voltage V at the output node. out During the cyclic conversion process, the controller can perform pulse width modulation to adjust the input voltage V. in Reduce to the user-defined output voltage V out The cyclic conversion process may include at least sequentially repeated charging steps, intermediate steps, discharging steps, and intermediate steps. Optionally, all intermediate steps may be the same, or at least two intermediate steps may be different.
[0045] According to aspects of this disclosure, in the case of a buck converter circuit with at least four levels, for each additional level, the cyclic conversion process may include a transfer step and an intermediate step. Optionally, all intermediate steps may be the same, or at least two intermediate steps may be different.
[0046] According to an aspect of this disclosure, the method may further include: for a duty cycle less than 0.5, during an intermediate step of the cyclic switching process, controlling switch elements Q3 and Q4 to be turned on, and controlling switch elements Q1 and Q2 to be isolated; for a duty cycle greater than 0.5, during an intermediate step of the cyclic switching process, controlling switch elements Q1 and Q2 to be turned on, and controlling switch elements Q3 and Q4 to be isolated.
[0047] According to aspects of this disclosure, the method may further include controlling switching elements Q1, Q2 and Q3 in isolation by the control system during the pre-charging process.
[0048] According to aspects of this disclosure, the method may further include controlling switching elements Q1, Q2, Q3 and Q4 by the control system during the cyclic switching process.
[0049] According to aspects of this disclosure, the method may further include measuring the voltage difference that builds up in the flying capacitor during the cycle switching process. Optionally, the method may further include measuring the maximum voltage difference that builds up in the flying capacitor during the cycle switching process.
[0050] According to aspects of this disclosure, the method may further include restarting the pre-charge process. The pre-charge process can be restarted if the measured voltage difference built up in the flying capacitor is outside the tolerance range. Optionally, the pre-charge process can be restarted if the maximum measured voltage difference built up in the flying capacitor during one or more cycles is outside the tolerance range.
[0051] According to aspects of this disclosure, the method for operating flying capacitors can be performed for at least one (optionally all) flying capacitors in a multilevel buck converter circuit.
[0052] According to an aspect of this disclosure, the buck converter circuit satisfies at least one of the following conditions: (a) the voltage difference built across the flying capacitor is at least 500V; (b) the user-defined output voltage V out (c) Input voltage V in (d) The energy required to charge the flying capacitor is at least 20 J; (e) The input voltage V in It is the DC voltage; and / or (f) the user-defined output voltage V. out It is DC voltage.
[0053] According to aspects of this disclosure, the buck converter circuit can have a buck-boost converter circuit topology. Attached Figure Description
[0054] Examples of this disclosure are described in more detail below with reference to the accompanying drawings. Wherein: Figure 1 The figure shows a buck converter circuit according to an embodiment described herein; Figure 2 The diagram illustrates a buck converter circuit according to another embodiment described herein; Figure 3 The diagram illustrates a buck converter circuit according to another embodiment described herein; Figure 4 The diagram illustrates a buck converter circuit according to another embodiment described herein; Figure 5 The diagram illustrates a buck converter circuit according to another embodiment described herein; Figure 6 The diagram illustrates a buck converter circuit according to another embodiment described herein; Figure 7a Plot the voltage at the switching node and the current in the inductor during one cycle with a duty cycle of less than 0.5; Figure 7b Plot the voltage at the switching node and the current in the inductor during a cycle with a duty cycle greater than 0.5; Figure 8a The diagram illustrates the sequence of pre-charge processing and cycle conversion processing; and Figure 8b The diagram illustrates the cyclical conversion process. Detailed Implementation
[0055] Figure 1 The diagram shows a step-down converter circuit, which includes a precharge switch (10), switching elements Q1 (11), Q2 (12), Q3 (13), Q4 (14), a flying capacitor (20), a voltage supply node (40), a voltage supply device (34), a first flying capacitor node (41), a second flying capacitor node (42), a switching node (43), a ground connection (35), and a control system (50).
[0056] The ground connection (35), voltage supply device (34), voltage supply node (40), pre-charge switch (10), and first flying capacitor node (41) are connected in series sequentially. The voltage supply node (40), switching element Q1 (11), and first flying capacitor node (41) are connected in series sequentially. The first flying capacitor node (41), flying capacitor (20), second flying capacitor node (42), switching element Q4 (14), and ground connection (35) are connected in series sequentially. The first flying capacitor node (41), switching element Q2 (12), switching node (43), switching element Q3 (13), and second flying capacitor node (42) are connected in series sequentially.
[0057] The input voltage V is provided at the voltage supply node (40) by the voltage supply device (34). in .
[0058] The control system (50) is configured to perform a pre-charging process (100) and a cyclic conversion process (200). During the pre-charging process (100), the control system (50) controls the pre-charging switch (10) and the switching element Q4 (14) to turn on. This creates a voltage difference in the flying capacitor (20). The voltage difference created in the flying capacitor (20) reduces the voltage difference supplied at the switching node (43) during different steps of the cyclic conversion process. Furthermore, the voltage difference created in the flying capacitor (20) reduces the voltage difference across at least some (optionally all) of the switching elements (10, 11, 12, 13, 14) of the buck converter circuit.
[0059] The cyclic conversion process (200) includes alternating charging and discharging steps (210, 230) for cyclic discharging and charging of the flying capacitor (20). During the cyclic conversion process (200), the control system (50) controls the pre-charge switch (10) to be isolated when the switching element Q1 is in isolation (11). The cyclic conversion process (200) also includes a charging step (210) and a discharging step (230). During the charging step (210) of the cyclic conversion process (200), the control system (50) controls the switching elements Q1 (11) and Q3 (13) to be turned on, and controls the switching elements Q2 (12) and Q4 (14) to be isolated to charge the flying capacitor (20). During the discharge step (230) of the cyclic conversion process (200), the control system (50) controls the switching elements Q2 (12) and Q4 (14) to be turned on, and controls the switching elements Q1 (11) and Q3 (13) to be isolated, so as to discharge the flying capacitor (20). Optionally, the voltage source (34) and the switching element Q4 (14) can be connected to the ground connection (35) via a common ground node (36).
[0060] Figures 2 to 5 include Figure 1 The electronic components shown in the figure. Figures 2 to 5 Additional electrical components may be included. Various embodiments of the additional electrical components can be combined. An individual electrical component of one embodiment can be combined with other embodiments. For example, Figure 4 The pre-charge resistor (30) shown in the figure can be used with Figure 1 The embodiments described herein are combined, excluding the inductor (32), output node (44), capacitor (31) and / or ground connection (35).
[0061] Figure 2The diagram illustrates a buck converter circuit. The control system (50) includes a voltage measuring device. The voltage measuring device is connected in parallel to a flying capacitor (20). For example, the voltage measuring device is connected across the two ends of the flying capacitor (20). Alternatively, the voltage measuring device may be connected to a first flying capacitor node (41) and a second flying capacitor node (42).
[0062] Figure 3 The diagram illustrates a buck converter circuit, which also includes a pre-charge resistor (30). A voltage supply node (40), the pre-charge resistor (30), and a pre-charge switch (10) are connected in series. Furthermore, a voltage supply device (34) and a switching element Q4 (14) are connected to a ground connection (35) via a common ground node (36). Optionally, the voltage supply device (34) and the switching element Q4 (14) may have separate ground connections (35).
[0063] Figure 4 The diagram illustrates a buck converter circuit, which also includes a pre-charge resistor (30), an inductor (32), a capacitor (31), and an output node (44). The voltage supply node (40), the pre-charge resistor (30), and the pre-charge switch (10) are connected in series. The switch node (43), the inductor (32), the output node (44), the capacitor (31), and the ground connection (35) are connected in series. Optionally, the voltage supply device (34), the switching element Q4 (14), and the capacitor (31) can be connected to the ground connection (35) via a common ground node (36).
[0064] Figure 5 The diagram illustrates a buck converter circuit, which also includes an output resistor (33). The output node (44), output resistor (33), and ground connection (35) are connected in series. Optionally, the voltage supply device (34), switching element Q4 (14), capacitor (31), and output resistor (33) can be connected to the ground connection (35) via a common ground node (36).
[0065] Figure 6The diagram shows a four-level buck converter circuit. The buck converter circuit includes a precharge switch A (10a), a precharge switch B (10b), a precharge resistor A (30a), a precharge resistor B (30b), switching elements Q1A (11a), Q1B (11b), Q2 (12), Q3 (13), Q4A (14a), Q4B (14b), flying capacitor A (20a), flying capacitor B (20b), a voltage supply device (34), a voltage supply node (40), a first flying capacitor node A (41a), a first flying capacitor node B (41b), a second flying capacitor node A (42b), a second flying capacitor node B (42b), a switching node (43), a ground connection (35), a control system (50), an inductor (32), a capacitor (31), an output resistor (33), and an output node (44).
[0066] The grounding connection (35), voltage supply device (34), voltage supply node, pre-charge resistor A (30a), pre-charge switch A (10a), and first flying capacitor node A (41a) are connected in series in sequence. The voltage supply node, pre-charge resistor B (30b), pre-charge switch B (10b), and first flying capacitor node B (41b) are connected in series in sequence.
[0067] The voltage supply node, the switching element Q1A (11a), and the first flying capacitor node A (41a) are connected in series sequentially. The first flying capacitor node A (41a), the switching element Q1B (11b), and the first flying capacitor node B (41b) are connected in series sequentially.
[0068] The first flying capacitor node A (41a), flying capacitor A (20a), second flying capacitor node A (42b), switching element Q4A (14a), and ground connection (35) are connected in series sequentially. The first flying capacitor node B (41b), flying capacitor B (20b), second flying capacitor node B (42b), switching element Q4B (14b), and second flying capacitor node A (42b) are connected in series sequentially.
[0069] The first flying capacitor node B (41b), switching element Q2 (12), switching node (43), switching element Q3 (13), and the second flying capacitor node B (42b) are connected in series sequentially. The switching node (43), inductor (32), output node (44), capacitor (31), and ground connection (35) are connected in series sequentially. The output node (44), output resistor (33), and ground connection (35) are connected in series sequentially. Optionally, the voltage supply device (34), switching element Q4A (14a), capacitor (31), and output resistor (33) can be connected to the ground connection (35) via a common ground node (36).
[0070] The input voltage V is provided at the voltage supply node by the voltage supply device (34). in The control system (50) is configured to perform pre-charge process A (100), pre-charge process B (100) and cycle conversion process (200).
[0071] During pre-charge process A (100), the control system (50) controls the pre-charge switch A (10a) and switching element Q4A (14a) to turn on. This creates a voltage difference in the flying capacitor A (20a). During pre-charge process B (100), the control system (50) controls the pre-charge switch B (10b), switching element Q4B (14b), and switching element Q4A (14a) to turn on. This creates a voltage difference in the flying capacitor B (20b). Pre-charge process A (100) and pre-charge process B (100) can be performed sequentially or simultaneously.
[0072] In an alternative embodiment, Figure 6 The four-level buck converter circuit illustrated does not include the pre-charge resistor B (30b) and the pre-charge switch B (10b). In this embodiment, during the pre-charge process B (100), the control system (50) controls the pre-charge switch A, switching element Q1B (11b), switching element Q4A (14a), and switching element Q4B (14b) to turn on. This creates a voltage difference in the flying capacitor B (20b). The pre-charge process A (100) and the pre-charge process B (100) can be performed sequentially or simultaneously.
[0073] The cyclic switching process (200) includes alternating charging and discharging steps (210, 230) for cyclic discharging and charging of flying capacitor A (20a) and flying capacitor B (20b). During the cyclic switching process (200), the control system (50) controls the precharge switch A (10a) to be isolated when the switching element Q1A (11a) is isolated, and the precharge switch B (10b) to be isolated when the switching element Q1B (11b) is isolated.
[0074] The cyclic conversion process (200) includes a charging step (210), a transfer step, and a discharging step (230). The transfer step discharges one flying capacitor and charges another flying capacitor.
[0075] During the charging step (210) of the cyclic conversion process (200), the control system (50) controls the switching elements Q1A (11a), Q4B (14b), and Q3 (13) to be turned on, and controls the switching elements Q1B (11b), Q2 (12), and Q4A (14a) to be isolated. This charges the flying capacitor A (20a).
[0076] During the conversion step of the cyclic conversion process (200), the control system (50) controls the switching elements Q1B (11b), Q3 (13), and Q4A (14a) to be turned on, and controls the switching elements Q1A (11a), Q2 (12), and Q4B (14b) to be isolated. This discharges the flying capacitor A (20a) and charges the flying capacitor B (20b).
[0077] During the discharge step (230) of the cyclic conversion process (200), the control system (50) controls the switching elements Q2 (12), Q4A (14a), and Q4B (14b) to be turned on, and controls the switching elements Q1A (11a), Q1B (11b), and Q3 (13) to be isolated. This discharges the flying capacitor B (20b).
[0078] Depending on the duty cycle, during the intermediate steps (220, 240) of the cyclic switching process (200), the control system (50) can control the switching elements Q1A (11a), Q1B (11b) and Q2 (12) to be isolated, and control the switching elements Q3 (13), Q4A (14a) and Q4B (14b) to be on.
[0079] Depending on the duty cycle, during the intermediate steps (220, 240) of the cyclic switching process (200), the control system (50) can control the switching elements Q1A (11a), Q1B (11b) and Q2 (12) to be on, and control the switching elements Q3 (13), Q4A (14a) and Q4B (14b) to be in isolation.
[0080] The cyclic conversion process may include at least the sequentially repeated charging step (210), intermediate step (220, 240), transfer step, intermediate step (220, 240), discharge step (230), and intermediate step (220, 240).
[0081] Figure 6 The four-level buck converter circuit illustrated herein includes the buck converter circuit of this disclosure in at least two embodiments. In embodiment A, switching element Q1A (11a) corresponds to switching element Q1, switching element Q1B (11b) is part of switching element Q2 (12), switching element Q4B (14b) is part of switching element Q3 (13), switching element Q4A (14a) corresponds to switching element Q4, and flying capacitor A (20a) corresponds to flying capacitor. In embodiment B, switching element Q1 includes switching element Q1A (11a) and switching element Q1B (11b), switching element Q4 includes switching element Q4A (14a) and switching element Q4B (14b), and flying capacitor B (20b) corresponds to flying capacitor.
[0082] This disclosure can be incorporated into any level of buck converter circuit including at least one flying capacitor.
[0083] Figure 7a The graph at the top shows the voltage supplied at the switching node (43) during one cycle of the cyclic switching process (200) for duty cycles less than 0.5. During the charging step (210) and discharging step (230), the input voltage V is supplied. in 50% of the voltage. Optionally, during the charging step (210), the supply voltage is equal to 50% of the input voltage V. in The voltage is reduced by the pre-charge voltage, and the pre-charge voltage is supplied during the discharge step (230). No voltage is supplied during the intermediate steps (220, 240).
[0084] Figure 7a The bottom shows the current I flowing in the inductor (32) during one cycle of the cyclic switching process (200) for a duty cycle less than 0.5. L The curve. During the charging step (210) and discharging step (230), the current I... L Increase. During the intermediate steps (220, 240), the current I... L Decrease.
[0085] Figure 7b The graph at the top shows the voltage supplied at the switching node (43) during one cycle of the cyclic switching process (200) for duty cycles greater than 0.5. During the charging step (210) and discharging step (230), the input voltage V is supplied. in 50% of the voltage. Optionally, during the charging step (210), the supply voltage is equal to 50% of the input voltage V. inThe voltage is subtracted from the pre-charge voltage, and the pre-charge voltage is supplied during the discharge step (230). During the intermediate steps (220, 240), the input voltage V is supplied. in .
[0086] Figure 7b The current I flowing into the inductor (32) during one cycle of the cyclic switching process (200) with a duty cycle of less than 0.5 is shown at the bottom. L The curve. During the charging step (210) and discharging step (230), the current I... L Decrease. During the intermediate steps (220, 240), the current I... L Increase.
[0087] Figure 8a The diagram illustrates a simplified method for operating a flying capacitor in a buck converter circuit. The method includes a pre-charge process (100) and a cyclic conversion process (200). The pre-charge process (100) is performed prior to the cyclic conversion process (200). Optionally, the pre-charge process (100) can be restarted if the measured voltage difference built into the flying capacitor is outside a tolerance range. Optionally, this tolerance range can be a variation of 15%, optionally 10%, or more preferably 5% of the pre-charge voltage.
[0088] Figure 8b The diagram illustrates a simplified cyclic conversion process (200). The cyclic conversion process (200) includes at least sequentially repeated charging steps (210) and discharging steps (230). Optionally, the cyclic conversion process (200) includes at least sequentially repeated charging steps (210), intermediate steps (220, 240), discharging steps (230), and intermediate steps (220, 240). In the case of a buck converter circuit with at least four levels, for each additional level, the cyclic conversion process (200) may include a transfer step and an intermediate step (220, 240). Optionally, all intermediate steps (220, 240) may be the same, or at least two intermediate steps (220, 240) may be different.
[0089] Reference Symbol List 10 Precharge Switch 11 Switching element Q1 12 Switching Element Q2 13 Switching Element Q3 14 Switching Element Q4 20 Flying Capacitor 30 pre-charge resistor 31 capacitor 32 Inductors 33 Output Resistor 34 Voltage Supply Device 35 Grounding Connection 36 grounding nodes 40Voltage Supply Node 41 First Flying Capacitor Node 42 Second flying capacitor node 43 switch nodes 44 output nodes 50 control system 100 pre-charge process 200-cycle conversion process 210 charging steps 220 intermediate steps 230 discharge steps 240 intermediate steps.
Claims
1. A buck converter circuit, the circuit comprising: The precharge switch (10), switching element Q1 (11), switching element Q2 (12), switching element Q3 (13), switching element Q4 (14), flying capacitor (20), voltage supply node (40), first flying capacitor node (41), second flying capacitor node (41), switching node (43) and control system (50); The voltage supply node (40), the pre-charge switch (10), and the first flying capacitor node (41) are connected in series in sequence. The voltage supply node (40), the switching element Q1 (11), and the first flying capacitor node (41) are connected in series in sequence; The first flying capacitor node (41), the flying capacitor (20), the second flying capacitor node (41), and the switching element Q4 (14) are connected in series in sequence; The first flying capacitor node (41), the switching element Q2 (12), the switching node (43), the switching element Q3 (13) and the second flying capacitor node (41) are connected in series in sequence; The input voltage V is supplied at the voltage supply node (40). in The control system (50) is configured to perform a pre-charging process (100) and a cycle conversion process (200); During the pre-charging process (100), the control system (50) controls the pre-charging switch (10) and the switching element Q4 (14) to be turned on in order to build a voltage difference in the flying capacitor (20); The cyclic conversion process (200) includes alternating charge and discharge steps (210, 230) for cyclic discharge and charge of the flying capacitor (20), and wherein during the cyclic conversion process (200): - When the switching element Q1 is isolated, the control system (50) controls the pre-charge switch (10) to be isolated; - During the charging step (210) of the cyclic conversion process (200), the control system (50) controls the switching elements Q1 (11) and Q3 (13) to be turned on, and controls the switching elements Q2 (12) and Q4 (14) to be isolated to charge the flying capacitor (20); - During the discharge step (230) of the cyclic conversion process (200), the control system (50) controls the switching elements Q2 (12) and Q4 (14) to be turned on, and controls the switching elements Q1 (11) and Q3 (13) to be isolated to discharge the flying capacitor (20).
2. The buck converter circuit according to claim 1, further comprising: Pre-charge resistor (30); The voltage supply node (40), the pre-charge resistor (30), and the pre-charge switch (10) are connected in series in sequence.
3. The buck converter circuit according to claim 1, in, The control system (50) includes a voltage measuring device for measuring the voltage difference constructed in the flying capacitor (20); The control system (50) is configured to terminate the pre-charging process (100) once the measured voltage difference built up in the flying capacitor (20) exceeds a predetermined pre-charging voltage threshold.
4. The buck converter circuit according to claim 1, further comprising: Inductor (32), capacitor (31), output node (43) and ground connection (35); in, The second flying capacitor (20) node (41), the switching element Q4 (14) and the ground connection (35) are connected in series in sequence; and The switching node (43), the inductor (32), the output node (43), the capacitor (31), and the ground connection (35) are connected in series in sequence.
5. The buck converter circuit according to claim 1, in, The buck converter circuit provides a user-defined output voltage V at the output node (43). out ; During the cyclic conversion process, the controller performs pulse width modulation to adjust the input voltage V. in Reduce to the user-defined output voltage V out , The cyclic conversion process (200) includes at least the charging step (210), intermediate steps (220, 240), discharging step (230), and intermediate steps (220, 240) to be repeated sequentially.
6. The buck converter circuit according to claim 1, in, The pulse width modulation defines the duty cycle; Wherein, for a duty cycle less than 0.5, during the intermediate steps (220, 240) of the cyclic switching process (200), the switching element Q3 (13) and the switching element Q4 (14) are configured to be on, and the switching element Q1 (11) and the switching element Q2 (12) are configured to be in isolation; Wherein, for a duty cycle greater than 0.5, during the intermediate steps (220, 240) of the cyclic switching process (200), the switching element Q1 (11) and the switching element Q2 (12) are configured to be on, and the switching element Q3 (13) and the switching element Q4 (14) are configured to be in isolation.
7. The buck converter circuit according to claim 1, in, The control system (50) controls the switching elements Q1 (11), Q2 (12) and Q3 (13) to be isolated during the pre-charging process (100); and The control system (50) controls the switching elements Q1 (11), Q2 (12), Q3 (13) and Q4 (14) during the cyclic switching process (200).
8. The buck converter circuit according to claim 1: in, The control system is configured to restart the pre-charging process (100); If the measured voltage difference constructed in the flying capacitor (20) is outside the tolerance range, the control system restarts the pre-charge process (100).
9. The buck converter circuit according to claim 1, in, The tolerance range is defined by a 15% variation in the pre-charge voltage.
10. A method for operating a flying capacitor (20) in a buck converter circuit, wherein the buck converter circuit comprises: The pre-charge switch (10), switching element Q1 (11), switching element Q2 (12), switching element Q3 (13), switching element Q4 (14), the flying capacitor, voltage supply node (40), first flying capacitor node (41), second flying capacitor node (41), switching node (43) and control system (50); The voltage supply node (40), the pre-charge switch (10), and the first flying capacitor node (41) are connected in series in sequence. The voltage supply node (40), the switching element Q1 (11), and the first flying capacitor node (41) are connected in series in sequence; The first flying capacitor node (41), the flying capacitor (20), the second flying capacitor node (41), and the switching element Q4 (14) are connected in series in sequence; The first flying capacitor node (41), the switching element Q2 (12), the switching node (43), the switching element Q3 (13) and the second flying capacitor node (41) are connected in series in sequence; The method includes: The input voltage V is supplied at the voltage supply node (40). in A pre-charge process (100) is performed to build a voltage difference in the flying capacitor (20); and Perform a cyclic conversion process (200), wherein the cyclic conversion process (200) includes alternating charge and discharge steps (210, 230) for cyclic discharge and charge of the flying capacitor (20); The pre-charging process (100) includes: Control the pre-charge switch (10) and the switching element Q4 (14) to be turned on, so as to build a voltage difference in the flying capacitor (20); The cyclic conversion process (200) mentioned above includes: When the switching element Q1 is isolated, the pre-charge switch (10) is controlled to be isolated; During the charging step (210) of the cyclic conversion process (200), the switching elements Q1 (11) and Q3 (13) are controlled to be turned on, and the switching elements Q2 (12) and Q4 (14) are controlled to be isolated to charge the flying capacitor (20). During the discharge step (230) of the cyclic conversion process (200), the switching elements Q2 (12) and Q4 (14) are controlled to be turned on, and the switching elements Q1 (11) and Q3 (13) are controlled to be isolated to discharge the flying capacitor (20).
11. The method of operating the flying capacitor (20) in a buck converter circuit according to claim 10, in, The method is performed by a buck converter circuit according to any one of claims 1 to 9.