Dc-dc converter topology, system and method of implementation thereof

Abstract

The application provides a DC-DC converter topology, system and method, and relates to the technical field of electronic circuits.The voltage input end in the DC-DC converter is connected with the voltage output end through a first switching unit, a first flying capacitor and a first inductor, and the voltage input end is also connected with the voltage output end through a second switching unit, a second flying capacitor and a second inductor; the upper plate of the first flying capacitor is connected with the lower plate of the second flying capacitor through a third switching unit and a third flying capacitor; the upper plate of the second flying capacitor is connected with the lower plate of the first flying capacitor through a fourth switching unit and a fourth flying capacitor; the upper plate of the third flying capacitor is connected with the lower plate of the second flying capacitor through a fifth switching unit, and the upper plate of the fourth flying capacitor is connected with the lower plate of the first flying capacitor through a sixth switching unit; and the lower plates of the first flying capacitor and the second flying capacitor are also grounded. The DC-DC converter has the characteristics of high conversion efficiency and high power density.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and more specifically, to a DC-DC converter topology, system, and implementation method thereof. Background Technology

[0002] A DC-DC converter is an electrical device that can transform a DC voltage of a certain range or a fixed value into another DC voltage of a variable or fixed value. It is widely used in various fields. For example, in the automotive, industrial robot, and fast charging industries, a high input voltage is used to reduce conduction losses in the wires when transmitting electrical energy, and a DC-DC converter is used to convert the high input voltage to a lower voltage to power the load when using electrical energy.

[0003] However, existing DC-DC converter circuits are usually dual-step or triple-step topologies, which have characteristics such as asymmetrical current paths, insufficient step-down ratio, high switching withstand voltage, and large switching conduction current. When the voltage required by the load is low, this will lead to problems such as low conversion efficiency, low power density, and large switching losses in the DC-DC converter, making it difficult for existing DC-DC converters to achieve high voltage ratio conversion under high power density. Summary of the Invention

[0004] The purpose of this application is to address the shortcomings of the prior art by providing a DC-DC converter topology, system, and implementation method therein, so as to solve the problems existing in the prior art.

[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows:

[0006] In a first aspect, embodiments of this application provide a DC-DC converter topology, which includes: a voltage input terminal, a voltage output terminal, two inductors, eight switching units, four flying capacitors, and an output capacitor module;

[0007] The voltage input terminal is connected to the voltage output terminal in sequence through a first switching unit, a first flying capacitor, and a first inductor. The voltage input terminal is also connected to the voltage output terminal in sequence through a second switching unit, a second flying capacitor, and a second inductor.

[0008] The upper plate of the first flying capacitor is connected to the lower plate of the second flying capacitor in sequence through the third switching unit and the fourth flying capacitor; the upper plate of the second flying capacitor is connected to the lower plate of the first flying capacitor in sequence through the fourth switching unit and the third flying capacitor.

[0009] The upper plate of the third flying capacitor is connected to the lower plate of the second flying capacitor through the fifth switching unit, and the upper plate of the fourth flying capacitor is connected to the lower plate of the first flying capacitor through the sixth switching unit.

[0010] The lower plates of the first and second flying capacitors are also grounded through the seventh and eighth switching units, respectively.

[0011] The voltage output terminal is grounded through the output capacitor module, wherein the output capacitor module includes at least one output capacitor. Secondly, an embodiment of this application also provides a DC-DC converter system, including the DC-DC converter topology described in the above embodiment, and further including: eight switch drivers;

[0012] Each of the switch drivers is connected to one of the switch units in the DC-DC converter topology, wherein the input terminal of the switch driver is used to receive control signals from the control module, and the output terminal of the switch driver is connected to the control terminal of the switch unit.

[0013] In a possible implementation example, the DC-DC converter system further includes: a pre-charge module and a control module;

[0014] The input terminal of the pre-charge module is connected to the voltage input terminal, the four first output terminals of the pre-charge module are respectively connected to the upper plates of the four flying capacitors, the second output terminal of the pre-charge module is connected to the enable terminal of the soft-start module in the control module, and the output terminal of the control module is connected to the control terminals of the eight switch drivers corresponding to the eight switch units.

[0015] In a possible implementation example, the pre-charge module includes: a first pre-charge unit and a second pre-charge unit, wherein the input terminals of the first pre-charge unit and the second pre-charge unit are both connected to the voltage input terminal, the two first output terminals of the first pre-charge unit are respectively connected to the upper plates of the first flight capacitor and the second flight capacitor, and the two first output terminals of the second pre-charge unit are respectively connected to the upper plates of the third flight capacitor and the fourth flight capacitor.

[0016] The second output terminal of the first pre-charge unit and the second output terminal of the second pre-charge unit are both connected to the enable terminal of the soft-start module in the control module.

[0017] In a possible implementation example, the pre-charge module further includes an AND gate, wherein the second output terminal of the first pre-charge unit and the second output terminal of the second pre-charge unit are connected to the enable terminal of the soft-start module in the control module through the AND gate.

[0018] In a possible implementation example, the first pre-charge unit further includes: a first current mirror module and a first voltage divider module;

[0019] One end of the first current mirror module is connected to a preset current source, and the other end is connected to the two first output terminals of the first pre-charge unit. One end of the first voltage divider module is connected to the upper plate of the first flying capacitor, and the other end is connected to the second output terminal of the first pre-charge unit.

[0020] The second pre-charge unit further includes: a second current mirror module and a second voltage divider module;

[0021] One end of the second current mirror module is connected to the preset current source, and the other end is connected to the two first output terminals of the second pre-charge unit. One end of the second voltage divider module is connected to the upper plate of the third flying capacitor, and the other end is connected to the second output terminal of the second pre-charge unit.

[0022] In a possible implementation example, the control module includes: a soft-start module, a frequency compensator, a comparator, a latch, a digital logic unit, and a triangular wave generator;

[0023] The soft-start module has its power supply connected to a preset power supply, its input is the input of the control module, its output is connected to the first input of the frequency compensator, its second input is connected to the voltage output, its output is connected to the non-inverting input of the comparator, its inverting input is connected to the triangular wave generator, its output is connected to the first input of the latch, its second input is connected to a preset reference clock, and its output is connected to the input of the digital logic unit.

[0024] The first output terminal of the digital logic unit is connected to the control terminals of the switch driver corresponding to the first switch unit, the switch driver corresponding to the fourth switch unit, and the switch driver corresponding to the sixth switch unit. The second output terminal of the digital logic unit is connected to the control terminals of the switch driver corresponding to the second switch unit, the switch driver corresponding to the third switch unit, and the switch driver corresponding to the fifth switch unit. The third output terminal of the digital logic unit is connected to the control terminal of the switch driver corresponding to the seventh switch unit. The fourth output terminal of the digital logic unit is connected to the control terminal of the switch driver corresponding to the eighth switch unit.

[0025] Thirdly, embodiments of this application provide a method for implementing a DC-DC converter system, applied to the DC-DC converter system described in the above embodiments, the method comprising:

[0026] The pre-charge module in the DC-DC converter system is used to pre-charge the four flying capacitors in the DC-DC converter system, so that the voltage of the first flying capacitor and the second flying capacitor reaches the first preset voltage, and the voltage of the third flying capacitor and the fourth flying capacitor reaches the second preset voltage, and outputs a soft start signal to the control module of the DC-DC converter system.

[0027] The control module generates a first control signal based on the soft-start signal, and controls the on / off state of the first switching unit, the fourth switching unit, and the sixth switching unit in the DC-DC converter system according to the first control signal;

[0028] The control module generates a second control signal based on the soft-start signal, and controls the on / off state of the second, third, and fifth switching units in the DC-DC converter system according to the second control signal;

[0029] The control module generates a third control signal based on the soft-start signal, and controls the on / off state of the seventh switching unit in the DC-DC converter system according to the third control signal;

[0030] The control module generates a fourth control signal based on the soft-start signal, and controls the on / off state of the eighth switching unit in the DC-DC converter system according to the fourth control signal.

[0031] In a possible implementation example, if the first control signal and the fourth control signal are high-level signals, and the second control signal and the third control signal are low-level signals, then the DC-DC converter system is in a first operating state.

[0032] If the third control signal and the fourth control signal are high-level signals, and the first control signal and the second control signal are low-level signals, then the DC-DC converter system is in the second operating state.

[0033] If the second control signal and the third control signal are high-level signals, and the first control signal and the fourth control signal are low-level signals, then the DC-DC converter system is in the third operating state.

[0034] The beneficial effects of this application are as follows: The DC-DC converter topology provided by this application is a fully symmetrical topology composed of multiple switching units and multiple flying capacitors. The voltage value of the inductor and the current value conducted by each switching unit are reduced to one-third of the original, which reduces the switching loss and conduction loss of the DC-DC converter. Furthermore, while the voltage value on the switching unit on the high side of the inductor is reduced, the volt-second balance burden of the inductor can be reduced, allowing the DC-DC converter to use inductors with smaller inductance values. In addition, since the flying capacitors bear part of the input voltage, the DC-DC converter can use switching units with relatively lower voltage ratings and better quality. Finally, the fully symmetrical power stage and operating mode also ensure that the voltage drop on each current path is exactly the same, reducing the current mismatch flowing through each inductor. Therefore, the DC-DC converter provided by this application has the characteristics of high conversion efficiency and high power density. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1(a) and Figure 1(b) are circuit diagrams of two existing DC-DC converters;

[0037] Figure 2 A circuit diagram of a DC-DC converter provided in an embodiment of this application;

[0038] Figure 3 This is a schematic diagram of a DC-DC converter system provided in an embodiment of this application;

[0039] Figure 4 A schematic diagram of a pre-charging module provided in an embodiment of this application;

[0040] Figure 5 A circuit diagram of a control module provided in one embodiment of this application;

[0041] Figure 6 A schematic diagram illustrating the startup process of a DC-DC converter system according to an embodiment of this application;

[0042] Figure 7(a) is a schematic diagram of the DC-DC converter system in state one, Figure 7(b) is a schematic diagram of the DC-DC converter system in state two, and Figure 7(c) is a schematic diagram of the DC-DC converter system in state three.

[0043] Figure 8A circuit diagram of a first pre-charging unit provided in an embodiment of this application;

[0044] Figure 9 A circuit diagram of a second pre-charging unit provided in an embodiment of this application;

[0045] Figure 10 This is a flowchart illustrating the implementation method of a DC-DC converter system provided in an embodiment of this application. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of this application, but not all embodiments.

[0047] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0048] In the description of this application, it should be noted that if the terms "upper", "lower", etc. appear to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship that the product of this application is usually placed in, it is only for the convenience of describing this application and simplifying the description, and does 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.

[0049] Furthermore, the terms "first," "second," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of this application described herein can be implemented in orders other than those illustrated or described herein. Additionally, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0050] It should be noted that, where there is no conflict, the features in the embodiments of this application can be combined with each other.

[0051] Figures 1(a) and 1(b) are circuit diagrams of two existing Buck-type step-down DC-DC converters. As shown in Figures 1(a) and 1(b), in the prior art, the DC-DC converters using the dual-step-down topology shown in Figure 1(a) or the three-stage step-down topology shown in Figure 1(b) suffer from problems such as short conduction time, high switching losses, and high switching current, which leads to low conversion efficiency and low power density of the DC-DC converter.

[0052] Therefore, in order to solve the problems existing in the prior art, this application provides a DC-DC converter topology, system and implementation method thereof, which can solve the problems existing in the prior art.

[0053] The following, together with several accompanying drawings and through multiple embodiments, provides specific examples illustrating the DC-DC converter topology, system, and implementation method provided in this application.

[0054] Figure 2 This is a circuit diagram of a DC-DC converter provided according to an embodiment of this application. (Refer to...) Figure 2 The DC-DC converter provided in this embodiment includes: a voltage input terminal ( Figure 2 VIN), voltage output terminal ( Figure 2 VOUT in the middle), two inductors ( Figure 2 L1, L2), and eight switch units ( Figure 2 The four flying capacitors are S1A, S1B, S2A, S2B, S3A, S3B, S4A, and S4B. Figure 2 The C1, C2, C3, C4 and output capacitor modules.

[0055] In this embodiment, the voltage input terminal VIN is connected to the voltage output terminal VOUT in sequence through the first switching unit S1A, the first flying capacitor C1 and the first inductor L1. The voltage input terminal VIN is also connected to the voltage output terminal VOUT in sequence through the second switching unit S1B, the second flying capacitor C2 and the second inductor L2.

[0056] The upper plate of the first flying capacitor C1 is connected to the lower plate of the second flying capacitor C2 via the third switching unit S2A and the fourth flying capacitor C4. The upper plate of the second flying capacitor C2 is connected to the lower plate of the first flying capacitor C1 via the fourth switching unit S2B and the third flying capacitor C3. The upper plate of the third flying capacitor C3 is connected to the lower plate of the second flying capacitor C2 via the fifth switching unit S3B. The upper plate of the fourth flying capacitor C4 is connected to the lower plate of the first flying capacitor C1 via the sixth switching unit S3A. The lower plates of the first and second flying capacitors are also grounded via the seventh switching unit S4A and the eighth switching unit S4B, respectively.

[0057] In practical applications, situations may arise where the load current suddenly increases. Therefore, the DC-DC converter also includes an output capacitor module, and the voltage output terminal VOUT is grounded through the output capacitor module. The output capacitor module includes at least one output capacitor COUT. Figure 2 The diagram only shows one output capacitor COUT. In practical applications, the output capacitor module can contain multiple output capacitors COUT connected in parallel. Compared to using only one output capacitor, using multiple output capacitors in parallel can improve the energy storage effect of the output capacitor module.

[0058] The following explanation of the DC-DC converter in steady state is based on equations (1) to (7).

[0059] When the DC-DC converter provided in this embodiment is in a steady state, for Figure 2 SW1 and SW2 in the equations are given by equations (1)-(3):

[0060] V SW1 =V IN -V C1 =V C2 -V C3 =V C4 (1)

[0061] V SW2 =V IN -V C2 =V C1 -V C4 =V C3 (2)

[0062] V SW1 =V SW2 (3)

[0063] For the first inductor L1 and the second inductor L2, we have equations (4) and (5):

[0064]

[0065]

[0066] Combining equations (1)-(5) above, the steady-state voltages of each flight capacitor can be obtained as shown in equations (6)-(7):

[0067]

[0068]

[0069] As can be seen from the above equations (1)-(7), by using the DC-DC converter provided in this embodiment, by controlling the conduction or disconnection of each switching unit, the steady-state voltage on the first flying capacitor C1 and the second flying capacitor C2 can be 2 / 3 of the input voltage (i.e., the steady-state voltage on the first flying capacitor and the second flying capacitor is 2 / 3VIN), and the steady-state voltage on the third flying capacitor C3 and the fourth flying capacitor C4 can be 1 / 3 of the input voltage (i.e., the steady-state voltage on the third flying capacitor and the fourth flying capacitor is 1 / 3VIN). Thus, at the switching nodes of the two inductors SW1 and SW2, voltages of 1 / 3VIN and 0V are alternately provided with a 180-degree phase difference.

[0070] At the switching nodes of inductors SW1 and SW2, the durations of 1 / 3VIN and 0V are both DT. S and (1-D)T S Where D is the duty cycle and T is the duty cycle. S Given the conduction period of the switching unit, the voltage conversion ratio (VCR) can be obtained from the volt-second balance of the inductor current as follows:

[0071]

[0072]

[0073] As can be seen from equations (8) and (9), compared with the traditional Buck-type step-down DC-DC converter, the DC-DC converter provided in this embodiment can increase the duty cycle by three times, that is, increase the high-voltage switch conduction time by three times, thereby reducing the design requirements for the delay of the drive circuit and control circuit under high-frequency operating conditions.

[0074] Furthermore, since the flying capacitor bears part of the input voltage, the withstand voltage of each switching unit can be reduced to 2 / 3VIN or 1 / 3VIN, as summarized in Table I (taking the first switching unit S1A as an example, when the voltage input terminal VIN is connected to the voltage output terminal VOUT through the first switching unit S1A, the first flying capacitor C1, and the first inductor L1 in sequence, since the voltage on the first flying capacitor C1 is 2 / 3VIN, the withstand voltage on the first switching unit S1A is 1 / 3VIN, and so on for other switching units). Because the power transistors with low withstand voltage values ​​have a better quality factor (Ron*Qg), compared to existing DC-DC converters, the lower withstand voltage of each switching unit in this embodiment further reduces power loss and improves the conversion efficiency of the DC-DC converter.

[0075] Table I. Switching Units and Their Voltage Ratings in DC-DC Converters

[0076] Pressure resistance 1 / 3VIN 1 / 3VIN 2 / 3VIN 2 / 3VIN 2 / 3VIN 2 / 3VIN 1 / 3VIN 1 / 3VIN

[0077] Furthermore, from the perspective of current conduction, in the DC-DC converter topology proposed in this embodiment, the first inductor L1 and the second inductor L2 work alternately, and the average current carried by the first inductor L1 and the second inductor L2 is:

[0078]

[0079] Among them, I LOAD I represents the output current of the DC-DC converter (i.e., the current flowing through the load connected to the DC-DC converter). L1 and I L2 Let L1 and L2 represent the average current values ​​on the first inductor L1 and the second inductor L2, respectively. From equation (10), it can be seen that the average current values ​​on both inductors L1 and L2 are half the output current of the DC-DC converter. When each inductor is magnetized, current is simultaneously supplied by the branches containing the three flying capacitors (when the first inductor L1 is magnetized, current is supplied by the branch containing the first flying capacitor C1, the branch containing the second flying capacitor C2 and the third flying capacitor C3, and the branch containing the fourth flying capacitor C4; when the second inductor L2 is magnetized, current is supplied by the branch containing the second flying capacitor C2, the branch containing the first flying capacitor C1 and the fourth flying capacitor C4, and the branch containing the third flying capacitor C3 C4). Therefore, the average current supplied by the flying capacitors on each branch is:

[0080]

[0081] Among them, I C1 I C2 I C3 I C4 Let C1, C2, C3, and C4 represent the average current values ​​on the first flying capacitor C1, the second flying capacitor C2, the third flying capacitor C3, and the fourth flying capacitor C4, respectively. These current values ​​are also the current values ​​when the switching units in the series path of the branch containing each flying capacitor are turned on. As shown in equation (11), the average current values ​​on the first flying capacitor C1, the second flying capacitor C2, the third flying capacitor C3, and the fourth flying capacitor C4 are all one-sixth of the output current of the DC-DC converter. Since the conduction loss is proportional to the square of the current value, the conduction losses of the first inductor L1, the second inductor L2, and each switching unit are significantly reduced compared to the existing buck DC-DC converter.

[0082] Finally, since the DC-DC converter topology proposed in this embodiment has the characteristic of complete symmetry, the voltages of the magnetization and demagnetization paths of the two inductors L1 and L2 can be made completely consistent without considering the mismatch of the components themselves. Therefore, compared with the existing buck DC-DC converters, the DC-DC converter provided in this embodiment has a lower inductor current mismatch without the need for additional complex control circuits.

[0083] In summary, the DC-DC converter provided in this embodiment has a fully symmetrical topology consisting of multiple switching units and multiple flying capacitors. The voltage value of the inductor and the current value conducted by each switching unit are reduced to one-third of the original value, which reduces the switching loss and conduction loss of the DC-DC converter. Furthermore, while the voltage value on the high-side switching unit of the inductor is reduced, the volt-second balance burden of the inductor can be alleviated, allowing the DC-DC converter to use inductors with smaller inductance values. In addition, since the flying capacitors bear part of the input voltage, the DC-DC converter can use switching units with relatively lower voltage ratings and better quality. Finally, the fully symmetrical power stage and operating mode also ensure that the voltage drop on each current path is exactly the same, reducing the current mismatch flowing through each inductor. Therefore, the DC-DC converter provided in this embodiment has the characteristics of high conversion efficiency and high power density. Figure 3 This is a schematic diagram of a DC-DC converter system provided in an embodiment of this application, with reference to... Figure 3 The DC-DC converter system includes eight switch drivers, each of which is connected to a switch unit in the DC-DC converter topology. The input of the switch driver is used to receive control signals from the control module, and the output of the switch driver is connected to the control terminal of the switch unit.

[0084] like Figure 3 As shown, the switching unit can be, for example, an NMOS transistor, and a switch driver ( Figure 3 The input terminal of the switch driver (100) is used to receive control signals for the switching unit (the control signals can be provided by the control module, which will be described in detail in the following embodiments). The output terminal of the switch driver is connected to the control terminal of the switching unit (the control terminal of the switching unit is the gate of the NMOS transistor). Based on the control signals received at its input terminal, the output terminal can control the switching unit to be turned on or off, thereby realizing the control of the on or off of each branch in the DC-DC converter.

[0085] In practical operation, before using the DC-DC converter system provided in the above embodiments, the DC-DC converter system needs a startup process, which is described below. Figures 4-9 The startup process of the DC-DC converter system provided in this application is illustrated with specific examples through multiple embodiments.

[0086] Figure 4 This is a schematic diagram of a pre-charging module provided in one embodiment of this application. Figure 5 A circuit diagram of a control module provided in an embodiment of this application is shown below. Figure 4 and Figure 5 The DC-DC converter may also include a pre-charge module and a control module.

[0087] First, it should be noted that the startup of a DC-DC converter system consists of two processes in sequence: pre-charging and soft-start. Since the voltages of the first flying capacitor C1, second flying capacitor C2, third flying capacitor C3, and fourth flying capacitor C4 of the DC-DC converter are 2 / 3VIN, 2 / 3VIN, 1 / 3VIN, and 1 / 3VIN respectively during steady-state operation, a pre-charging module is needed to pre-charge these four flying capacitors to prevent damage to the power devices during the startup phase due to overvoltage. Simultaneously, a control module is added to slowly increase the input voltage at the positive terminal of the error amplifier in the control module, causing the duty cycle generated by the switching driver to rise slowly, thus preventing inductor current overshoot. This is equivalent to performing a soft start on the DC-DC converter system.

[0088] Among them, the input terminal of the pre-charge module (i.e. Figure 4 In the schematic diagram of the pre-charge module, VIN is connected to the voltage input terminal VIN of the DC-DC converter, and the four first output terminals of the pre-charge module are... Figure 4 VC1T, VCT2, VCT3, and VCT4 are respectively connected to the upper plates of the four flying capacitors (i.e., Figure 3 The upper plates of C1, C2, C3, and C4, and the second output terminal of the pre-charge module ( Figure 4 The ST in the middle of the control module is the enable terminal of the soft start module. Figure 5 ST), the power stage output voltage VOUT is connected to the control module input terminal (the second input terminal of the frequency compensator). Figure 5 The inverting input of the 120 comparator, the output of the control module ( Figure 5 The NC / CLK1 / 2 in the middle are connected to the control terminals of the eight switch drivers corresponding to the eight switch units (CLK1 is connected to the control terminals of the switch drivers corresponding to the first switch unit S1A, the fourth switch unit S2B, and the sixth switch unit S3A; CLK2 is connected to the control terminals of the switch drivers corresponding to the second switch unit S1B, the third switch unit S2A, and the fifth switch unit S3B; NCLK1 is connected to the control terminal of the switch driver corresponding to the seventh switch unit S4A; and NCLK2 is connected to the control terminal of the switch driver corresponding to the eighth switch unit S4B).

[0089] Continue to refer to Figure 5The control module includes a soft-start module ( Figure 5 110 in the middle), frequency compensator ( Figure 5 120 in the middle), comparator ( Figure 5 130 in the middle), latch ( Figure 5 140 in the middle) and digital logic unit ( Figure 5 150 in the figure), triangular wave generator (not shown in the figure).

[0090] The soft-start module can be composed of a preset soft-start circuit. The enable terminal of the soft-start module is the output signal ST of the pre-charge circuit. The input terminal of the soft-start module is connected to the preset power supply VREF, and the output terminal of the soft-start module is connected to the first input terminal of the frequency compensator (i.e., the first input terminal of the frequency compensator is...). Figure 5 The non-inverting input of the 120 comparator is connected to the second input of the frequency compensator, which is connected to the voltage output VOUT (the second input of the frequency compensator). Figure 5 The inverting input terminal of the 120 comparator (connected to the voltage output terminal VOUT of the DC-DC converter), and the output terminal of the frequency compensator (the output terminal of the frequency compensator is...) Figure 5 The output terminal VC of comparator 120 is connected to the non-inverting input terminal of comparator 130. The inverting input terminal of comparator 130 is connected to the triangular wave signal VSAW. The output terminal of comparator 130 is connected to the first input terminal (i.e., the R terminal) of latch 140. The second input terminal (i.e., the S terminal) of latch 140 is connected to the preset reference clock ECLK. The output terminal (i.e., the Q terminal) of latch 140 is connected to the input terminal of the digital logic unit. The triangular wave signal VSAW and the reference clock ECLK are both generated by the triangular wave generator in the control module.

[0091] The first output of the digital logic unit 150 ( Figure 5 The CLK1 output of the 150 is connected to the control terminals (control terminals of the switches, i.e., their corresponding switch drivers) of the first switch unit S1A, the fourth switch unit S2B, and the sixth switch unit S3A. The second output terminal of the digital logic unit ( Figure 5 The CLK2 output of the 150 is connected to the control terminals of the second switch unit S1B, the third switch unit S2A, and the fifth switch unit S3B. The third output terminal of the digital logic unit ( Figure 5 The NCLK1 output of the 150 is connected to the control terminal of the seventh switch unit S4A, and the fourth output of the digital logic unit ( Figure 5 The NCLK2 output terminal of the 150 is connected to the control terminal of the eighth switch unit S4B.

[0092] The specific implementation of the DC-DC converter system startup process is as follows: Taking the charging of the first flying capacitor C1 and the second flying capacitor C2 as an example, in the initial state, through the control of the digital logic unit and the switch driver, the switching units S4A and S4B in the DC-DC converter topology are turned on, and all other switching units are turned off, thereby grounding the lower plates of the first flying capacitor C1 and the second flying capacitor C2. At this time, the pre-charge circuit starts to work. The switches SCT1, SCT2, and SCT3 in the pre-charge circuit are all in the on state, and SCT4 is in the off state. The input voltage VIN of the DC-DC converter topology rises slowly. MC1 and MC2 in the pre-charge circuit replicate and amplify the current IREF through the current mirror to charge the first flying capacitor C1 and the second flying capacitor C2.

[0093] In the pre-charge circuit, resistors R1 and R2 divide the voltages of the upper plates of the first flying capacitor C1 and the second flying capacitor C2, respectively. This voltage is then compared with a preset reference voltage VDIV via a comparator. When VC1 / 2T exceeds the preset reference voltage VDIV, the comparator outputs a high potential, the RS latch in the pre-charge circuit flips, and the ST signal is transmitted to the control module. The soft-start module then begins operation, providing a slowly rising reference voltage to the non-inverting input of the frequency compensator. This causes the voltage VC at the output of the frequency compensator to rise slowly until VC intersects with the sawtooth wave voltage VSAW, generating a PWM wave with a specific duty cycle. This PWM wave is processed by the digital logic unit and sent to the DC-DC converter topology, driving the switching of multiple switching units within the topology, thus enabling the DC-DC converter to start operating. The startup process of the DC-DC converter system is as follows: Figure 6 As shown, it should be noted that in order to reduce the power consumption of the DC-DC converter system, after the pre-charging is completed, switches SCT1, SCT2, and SCT3 can be turned off, switch SCT4 can be turned on, and the comparator in the pre-charging circuit can be powered off.

[0094] Once pre-charging and soft-start are complete, the DC-DC converter system is in a stable operating state. The following is a summary... Figures 7(a)-7(c) This paper provides a detailed explanation of the stable operating conditions of a DC-DC converter system.

[0095] First, it should be noted that the DC-DC converter system operates in three states during steady-state operation: State 1, State 2, and State 3, and alternates between them in a complete working cycle of State 1, State 2, State 3, and State 2. Figure 7(a) shows a schematic diagram of the DC-DC converter system in State 1, Figure 7(b) shows a schematic diagram of the DC-DC converter system in State 2, and Figure 7(c) shows a schematic diagram of the DC-DC converter system in State 3.

[0096] Reference Figures 7(a)-7(c) At the beginning of each cycle, the converter is in state one as shown in Figure 7(a). The pulse signal ECLK is input to the S terminal of the RS latch in the control module 120, the RS latch outputs a high level, and the sawtooth wave signal rises from the lowest point. At this time, the control signals CLK1 and NCLK2 are high level, and CLK2 and NCLK1 are low level. The control signal turns on the switching units S1A, S2B, S3A, and S4B through the switch driver, and turns off S1B, S2A, S3B, and S4A. This allows the input voltage to charge the first flying capacitor C1 through the switching unit S1A, the second flying capacitor C2 to charge the third flying capacitor C3 through the switching unit S2B, and the fourth flying capacitor C4 to discharge through the switching unit S3A. The above three current paths together provide current to the first inductor L1, and form a voltage of VIN / 3 at its upper end SW1, causing the current of the first inductor to rise. At the same time, the upper end SW2 of the second inductor L2 is grounded, and the current of the second inductor L2 decreases.

[0097] Inductors L1 and L2 together provide current to the load terminal (ILOAD in the figure). The output voltage VOUT is collected and entered into the control module. After error amplification and frequency compensation with the reference voltage VREF, the output voltage VC of the frequency compensator is generated. When VSAW rises to intersect with VC, the comparator in the control module outputs a high level and the RS latch outputs a low level. After passing through the digital logic unit, the control signals NCLK1 and NCLK2 output a high level and CLK1 and CLK2 output a low level, entering state two as shown in Figure 7(b).

[0098] In state two, switching units S4A and S4B are turned on, while the remaining switching units are turned off. All upper plates of the flying capacitors are floating. Since SW1 and SW2 are grounded, the currents in inductors L1 and L2 decrease simultaneously. L1 and L2 together provide current to the load terminal ILOAD. At the same time, because the upper end SW1 of inductor L1 is grounded, the current in L1 decreases. L1 and L2 together provide current to the load terminal ILOAD. At the end of a switching cycle, ECLK outputs a pulse to set the RS latch output to a high level. After digital logic, control signals NCLK1 and CLK2 output high levels, and NCLK2 and CLK1 output low levels, entering state three as shown in Figure 7(c). At this time, VSAW immediately drops to its lowest voltage and begins to rise again.

[0099] In state three, the control signal turns on S1B, S2A, S3B, and S4A via the switch driver, and turns off S1A, S2B, S3A, and S4B. This allows the input voltage to charge the second flying capacitor C2 through S1B, the first flying capacitor C1 to charge the fourth flying capacitor C4 through S2A, and the third flying capacitor C3 to discharge through S3B. These three current paths together provide current to the second inductor L2, creating a voltage of VIN / 3 at its upper end SW2, causing the current in the second inductor L2 to rise. Simultaneously, the first inductor L... Since the upper terminal SW1 is grounded, the current of the first inductor L1 decreases. Inductors L1 and L2 together provide current to the load terminal ILOAD. The output voltage is collected and enters the control module. After error amplification and frequency compensation with the reference voltage VREF, the error amplifier output voltage VC is generated. When VSAW rises to intersect with VC, the comparator outputs a high level and the RS latch outputs a low level. After digital logic, the control signals NCLK1 and NCLK2 output a high level, and CLK1 and CLK2 output a low level, and the system re-enters state two.

[0100] When the DC-DC converter system is in a stable operating state, it cycles through the operating states described above (I, II, III, II) to provide appropriate voltage and current to the load. Note that the frequency of ECLK is twice the operating frequency of the converter's switching unit.

[0101] Based on the DC-DC converter system provided in the above embodiments, it should be further explained that, since the steady-state voltage of the first flying capacitor C1 and the second flying capacitor C2 is 2 / 3VIN, and the steady-state voltage of the third flying capacitor C3 and the fourth flying capacitor C4 is 1 / 3VIN, it is necessary to group the first flying capacitor C1 and the second flying capacitor C2 together, and the third flying capacitor C3 and the fourth flying capacitor C4 together, and precharge the two groups of flying capacitors respectively. The pre-charging module may include a first pre-charging unit and a second pre-charging unit. The first pre-charging unit is used to pre-charge the first flying capacitor C1 and the second flying capacitor C2, and the second pre-charging unit is used to pre-charge the third flying capacitor C3 and the fourth flying capacitor C4.

[0102] The following combination Figure 8 and Figure 9 The first pre-charging unit and the second pre-charging unit are illustrated with examples.

[0103] Figure 8 This is a circuit diagram of a first pre-charging unit provided in an embodiment of this application. Figure 9 This is a circuit diagram of a second pre-charging unit provided in an embodiment of this application. (Refer to...) Figure 8 and Figure 9The first pre-charge unit includes a first current mirror module (the first current mirror module includes three sets of current mirrors, namely...). Figure 8 PMOS transistors MC1 and MC2, MC3 and MC4, MC5 and MC6), and the first voltage divider module (the first voltage divider module is...). Figure 8 Resistors R1 and R2 in the first pre-charge unit are used to divide VIN, thereby controlling the voltage across the first flight capacitor C1 and the second flight capacitor C2 to 2 / 3 VIN. The second pre-charge unit includes a second current mirror module (the first current mirror module includes three sets of current mirrors, namely...). Figure 9 (MC7 and MC8, MC9 and MC10, MC11 and MC12), and the second voltage divider module (the second voltage divider module is...) Figure 9 Resistors R3 and R4 are used to divide VIN, thereby controlling the voltage across the third flying capacitor C3 and the fourth flying capacitor C4 to 1 / 3 VIN.

[0104] It should be noted that the resistance values ​​of resistors R1, R2, R3, and R4 are determined by the voltage required by the flight capacitor they divide. In actual operation, after knowing the voltage required by the flight capacitor, the resistance values ​​of each resistor can be calculated, and the resistors with the calculated values ​​can be installed in the first pre-charge unit and the second pre-charge unit.

[0105] Continue to refer to Figure 8 and Figure 9 The input terminals of both the first pre-charge unit and the second pre-charge unit are connected to the voltage input terminal. Figure 8 VIN and in the first pre-charge unit Figure 9 The VIN of the second pre-charge unit is connected to the voltage input terminal VIN of the DC-DC converter system. One end of the first current mirror module and one end of the second current mirror are both connected to a preset current source. Figure 8 MC6 and Figure 9 (All MC12 are connected to the same preset current source IREF).

[0106] The two first output terminals of the first pre-charge unit are respectively connected to the upper plates of the first flight capacitor C1 and the second flight capacitor C2, that is... Figure 8 MC1 and MC2 are connected to the upper plates of the first flight capacitor C1 and the second flight capacitor C2, respectively; one end of the first voltage divider module is connected to the upper plate of the first flight capacitor C1, and the other end is connected to the second output terminal of the first pre-charge unit, that is, one end of resistor R1 is connected to the upper plate of the first flight capacitor C1, and the other end of R1 and one end of R2 are connected to the comparator in the first pre-charge unit. Figure 8 The non-inverting input of comparator 160 is connected to the output of the latch ( ). Figure 8The second output terminal of the first pre-charge power supply is the output terminal of latch 170.

[0107] The two first output terminals of the second pre-charge unit are respectively connected to the upper plates of the third flight capacitor C3 and the fourth flight capacitor C4, that is... Figure 9 MC7 and MC8 are connected to the upper plates of the third flight capacitor C3 and the fourth flight capacitor C4, respectively; one end of the second voltage divider module is connected to the upper plate of the third flight capacitor C3, and the other end is connected to the second output terminal of the second pre-charge unit, that is, one end of resistor R3 is connected to the upper plate of the third flight capacitor C3, and the other end of R3 and one end of R4 are connected to the comparator in the second pre-charge unit. Figure 9 The non-inverting input of comparator 180 is connected to the output of the latch ( ). Figure 9 The second output terminal of the second pre-charge power supply is the output terminal of latch 190.

[0108] Since the pre-charge module contains both a first pre-charge unit and a second pre-charge unit, the control unit needs to perform a soft start only after both the first and second pre-charge units have completed pre-charging of the corresponding flight capacitors. Therefore, the pre-charge module can also include an AND gate (not shown in the figure). The second output terminal of the first pre-charge unit and the second output terminal of the second pre-charge unit are connected to the input terminal of the control module through the AND gate. In this way, the control unit can control the DC-DC converter system to perform a soft start only after both the first and second pre-charge units have completed pre-charging of the corresponding flight capacitors.

[0109] Finally, it should be noted that under stable operating conditions of the DC-DC converter system, the output capacitor COUT is fully charged. However, when the load current suddenly increases, the current provided by the DC-DC converter system is insufficient to support the load's current requirements. In this case, the output capacitor COUT will discharge a significant amount of charge, causing VOUT to decrease. Comparing this decreased VOUT with VREF, the frequency compensator will generate a higher VC, thus prolonging the intersection time of VSAW and VC. In other words, the converter remains in state one or state three for an extended period. Since the currents in inductors L1 and L2 are both increasing in these two states, the extended state one and state three facilitates the supply of larger inductor current to the load, thereby achieving a balance between the supply and demand of the output current and gradually restoring the VOUT value.

[0110] In a possible implementation example, one embodiment of this application also provides a method for implementing a DC-DC converter system, applied to the DC-DC converter system provided in the above embodiment. Figure 10 This is a flowchart illustrating the implementation method of a DC-DC converter system provided in an embodiment of this application, as shown below. Figure 10 As shown, the method includes the following steps:

[0111] S1. The four flying capacitors in the DC-DC converter system are precharged using the precharge module in the DC-DC converter system.

[0112] In this embodiment, the pre-charge module in the DC-DC converter system is used to pre-charge the four flying capacitors in the DC-DC converter system, so that the voltage of the first flying capacitor and the second flying capacitor reaches the first preset voltage (i.e., 2 / 3VIN), the voltage of the third flying capacitor and the fourth flying capacitor reaches the second preset voltage (i.e., 1 / 3VIN), and outputs a soft start signal to the control module in the DC-DC converter (i.e. inputs a soft start signal to the ST terminal of the soft start module 110). The specific steps are as shown in S2-S5.

[0113] S2. The control module generates the first control signal based on the soft start signal.

[0114] Specifically, the digital logic unit of the control module can generate a first control signal based on the soft-start signal and input the first control signal to the corresponding switch driver through the CLK1 terminal, so that the switch driver controls the on / off state of the first switch unit, the fourth switch unit and the sixth switch unit in the DC-DC converter system.

[0115] S3. The control module generates a second control signal based on the soft start signal.

[0116] The control module can generate a second control signal based on the soft-start signal and input the second control signal to the corresponding switch driver through the CLK2 terminal, so that the switch driver can control the on / off state of the second switch unit, the third switch unit and the fifth switch unit in the DC-DC converter system.

[0117] S4. The control module generates a third control signal based on the soft start signal.

[0118] The control module can generate a third control signal based on the soft-start signal and input the third control signal to the corresponding switch driver through the NCLK1 terminal so that the switch driver can control the on / off state of the seventh switch unit in the DC-DC converter system.

[0119] S5. The control module generates a fourth control signal based on the soft-start signal.

[0120] The control module can generate a fourth control signal based on the soft-start signal and input the fourth control signal to the corresponding switch driver through the NCLK2 terminal so that the switch driver controls the on / off state of the eighth switch unit in the DC-DC converter system.

[0121] When the first and fourth control signals are high-level signals and the second and third control signals are low-level signals, the DC-DC converter in the DC-DC converter system is in the first operating state as shown in Figure 7(a); when the third and fourth control signals are high-level signals and the first and second control signals are low-level signals, the DC-DC converter in the DC-DC converter system is in the second operating state as shown in Figure 7(b); when the second and third control signals are high-level signals and the first and fourth control signals are low-level signals, the DC-DC converter in the DC-DC converter system is in the third operating state as shown in Figure 7(c).

[0122] The method provided in this embodiment can realize the on / off control of multiple switching units and control the number of switching units that are turned on at the same time, so that the DC-DC converter can switch between state one, state two and state three, and the first inductor L1 and the second inductor L2 work alternately. This reduces the voltage value of the inductor and the current value conducted by each switching unit to one-third of the original value, thereby reducing the switching loss and conduction loss of the DC-DC converter. Furthermore, since the flying capacitor bears part of the input voltage, the DC-DC converter can use switching units with relatively lower voltage rating and better quality. The fully symmetrical power stage and operating mode also ensure that the voltage drop on each current path is exactly the same, reducing the mismatch of the current flowing through each inductor, so that the DC-DC converter has the characteristics of high conversion efficiency and high power density.

[0123] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A DC-DC converter topology, characterized in that, include: Voltage input terminal, voltage output terminal, two inductors, eight switching units, four flying capacitors and output capacitor module; The voltage input terminal is connected to the voltage output terminal in sequence through a first switching unit, a first flying capacitor, and a first inductor. The voltage input terminal is also connected to the voltage output terminal in sequence through a second switching unit, a second flying capacitor, and a second inductor. The upper plate of the first flying capacitor is connected to the lower plate of the second flying capacitor in sequence through the third switching unit and the fourth flying capacitor; the upper plate of the second flying capacitor is connected to the lower plate of the first flying capacitor in sequence through the fourth switching unit and the third flying capacitor. The upper plate of the third flying capacitor is connected to the lower plate of the second flying capacitor through the fifth switching unit, and the upper plate of the fourth flying capacitor is connected to the lower plate of the first flying capacitor through the sixth switching unit. The lower plates of the first and second flying capacitors are also grounded through the seventh and eighth switching units, respectively. The voltage output terminal is grounded through the output capacitor module, wherein the output capacitor module includes at least one output capacitor.

2. A DC-DC converter system, characterized in that, Including the DC-DC converter topology of claim 1, it further includes: eight switch drivers; Each of the switch drivers is connected to one of the switch units in the DC-DC converter topology, wherein the input of the switch driver is used to receive control signals from the control module, and the output of the switch driver is connected to the control terminal of the switch unit.

3. The DC-DC converter system as described in claim 2, characterized in that, The DC-DC converter system also includes: a pre-charge module and a control module; The input terminal of the pre-charge module is connected to the voltage input terminal, the four first output terminals of the pre-charge module are respectively connected to the upper plates of the four flying capacitors, the second output terminal of the pre-charge module is connected to the enable terminal of the soft-start module in the control module, and the output terminal of the control module is connected to the control terminals of the eight switch drivers corresponding to the eight switch units.

4. The DC-DC converter system as described in claim 3, characterized in that, The pre-charging module includes: a first pre-charging unit and a second pre-charging unit, wherein the input terminals of the first pre-charging unit and the second pre-charging unit are both connected to the voltage input terminal, the two first output terminals of the first pre-charging unit are respectively connected to the upper plates of the first flight capacitor and the second flight capacitor, and the two first output terminals of the second pre-charging unit are respectively connected to the upper plates of the third flight capacitor and the fourth flight capacitor. The second output terminal of the first pre-charge unit and the second output terminal of the second pre-charge unit are both connected to the enable terminal of the soft-start module in the control module.

5. The DC-DC converter system as described in claim 4, characterized in that, The pre-charge module further includes an AND gate, wherein the second output terminal of the first pre-charge unit and the second output terminal of the second pre-charge unit are connected to the enable terminal of the soft-start module in the control module through the AND gate.

6. The DC-DC converter system as described in claim 4, characterized in that, The first pre-charge unit further includes: a first current mirror module and a first voltage divider module; One end of the first current mirror module is connected to a preset current source, and the other end is connected to the two first output terminals of the first pre-charge unit. One end of the first voltage divider module is connected to the upper plate of the first flying capacitor, and the other end is connected to the second output terminal of the first pre-charge unit. The second pre-charge unit further includes: a second current mirror module and a second voltage divider module; One end of the second current mirror module is connected to the preset current source, and the other end is connected to the two first output terminals of the second pre-charge unit. One end of the second voltage divider module is connected to the upper plate of the third flying capacitor, and the other end is connected to the second output terminal of the second pre-charge unit.

7. The DC-DC converter system as described in claim 3, characterized in that, The control module includes: a soft-start module, a frequency compensator, a comparator, a latch, a digital logic unit, and a triangular wave generator; The soft-start module has its power supply connected to a preset power supply, its input providing a reference voltage to the control module, its output connected to the first input of the frequency compensator, its second input connected to the voltage output, its output connected to the non-inverting input of the comparator, its inverting input connected to the triangular wave generator, its output connected to the first input of the latch, its second input connected to a preset reference clock, and its output connected to the input of the digital logic unit. The first output terminal of the digital logic unit is connected to the control terminals of the switch driver corresponding to the first switch unit, the switch driver corresponding to the fourth switch unit, and the switch driver corresponding to the sixth switch unit. The second output terminal of the digital logic unit is connected to the control terminals of the switch driver corresponding to the second switch unit, the switch driver corresponding to the third switch unit, and the switch driver corresponding to the fifth switch unit. The third output terminal of the digital logic unit is connected to the control terminal of the switch driver corresponding to the seventh switch unit. The fourth output terminal of the digital logic unit is connected to the control terminal of the switch driver corresponding to the eighth switch unit.

8. A method for implementing a DC-DC converter system, characterized in that, The method, applied to the DC-DC converter system of claim 3, comprises: The pre-charge module in the DC-DC converter system is used to pre-charge the four flying capacitors in the DC-DC converter system, so that the voltage of the first flying capacitor and the second flying capacitor reaches the first preset voltage, and the voltage of the third flying capacitor and the fourth flying capacitor reaches the second preset voltage, and outputs a soft start signal to the control module of the DC-DC converter system. The control module generates a first control signal based on the soft-start signal, and controls the on / off state of the first switching unit, the fourth switching unit, and the sixth switching unit in the DC-DC converter system according to the first control signal; The control module generates a second control signal based on the soft-start signal, and controls the on / off state of the second, third, and fifth switching units in the DC-DC converter system according to the second control signal; The control module generates a third control signal based on the soft-start signal, and controls the on / off state of the seventh switching unit in the DC-DC converter system according to the third control signal; The control module generates a fourth control signal based on the soft-start signal, and controls the on / off state of the eighth switching unit in the DC-DC converter system according to the fourth control signal.

9. The method as described in claim 8, characterized in that, If the first control signal and the fourth control signal are high-level signals, and the second control signal and the third control signal are low-level signals, then the DC-DC converter system is in the first operating state; If the third control signal and the fourth control signal are high-level signals, and the first control signal and the second control signal are low-level signals, then the DC-DC converter system is in the second operating state. If the second control signal and the third control signal are high-level signals, and the first control signal and the fourth control signal are low-level signals, then the DC-DC converter system is in the third operating state.

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