A hybrid architecture BUCK DC-DC step-down converter

Abstract

The present invention belongs to the field of integrated circuit technology, and specifically is a BUCK DC-DC buck converter with a hybrid architecture. The buck converter of the present invention includes eight power switches, three switch capacitors, two switch inductors and one output capacitor, assisted by a control system and a drive system; the present invention utilizes switch capacitors to reduce the voltage pressure of the input voltage on the power switch, while utilizing switch inductors to provide output current capability, and utilizes mode control to realize the conversion of high-voltage input voltage into a low-voltage output with high conversion efficiency, high power density, and strong load capacity. The present invention uses a power switch with a lower voltage resistance to realize high-voltage input conversion, greatly reducing the size of the power switch, reducing the loss of the power switch, and improving its conversion efficiency; adopting a hybrid architecture can greatly reduce the inductance value and improve the power density of the system. The present invention solves the problems faced by traditional half-bridge BUCK DC-DC in high-voltage input and low-voltage output, and has broad application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuits, and in particular relates to a Buck DC-DC step-down converter. Background Art

[0002] The rapid development of new energy vehicles, 5G communications, and data centers has greatly increased the demand for high-voltage input, high-conversion-ratio, and high-power-density switching power supplies, such as 12V, 24V, and even 48V high-voltage inputs. Furthermore, continuous advancements in semiconductor manufacturing processes have reduced load power supply voltages to 1V or even below. To bridge the significant voltage gap between the input power rail and the terminal module, high-step-down-ratio buck power converters are crucial.

[0003] Traditional half-bridge buck DC-DC converters have gained widespread adoption due to their simple topology and ease of control, offering direct benefits in terms of efficiency, switching frequency, and cost. However, the advantages of the traditional half-bridge structure diminish rapidly when the input voltage is significantly greater than the output voltage. To achieve a high conversion ratio, the on-time of the half-bridge buck DC-DC converter must be significantly shortened, as this is determined by the ratio of the output voltage to the input voltage. To achieve this short on-time, the feedback control loop and the drive time of the power transistors must be reduced accordingly. Furthermore, to accommodate rising input voltages, larger power switches must be used to withstand higher device voltages, which inevitably results in longer drive delays. Furthermore, for high step-down ratios, the low-side power switch of the half-bridge buck converter is on for the majority of each switching cycle, significantly increasing its conduction losses. Therefore, its size must be significantly larger than the high-side power switch, resulting in significantly increased switching losses and a more complex trade-off between gate drive, dead-time control, and switching noise control. However, in a half-bridge buck DC-DC converter, when the power input voltage V IN Much higher than the output voltage V OUT First, in order to achieve a large voltage conversion ratio, the high-side power switch on-time t of the half-bridge buck DC-DC step-down converter must be greatly shortened, which is related to V OUT / V IN In order to achieve a short on-time, the propagation delay caused by the power transistor, gate driver, and feedback control loop must be reduced accordingly. However, on the other hand, in order to adapt to the increasing V IN , a larger power transistor must be used to maintain a high breakdown voltage, which results in a longer delay. OUT / V INDue to the defined high step-down ratio, the low-voltage side power switch of a half-bridge buck DC-DC step-down converter is on for most of each switching cycle, significantly increasing its conduction losses. Therefore, its size must be much larger than the high-voltage side, resulting in a significant increase in switching losses, which further complicates the design trade-offs between gate drive, dead-time control, and switching noise control. Finally, high switching frequency helps reduce the size of power passive components, especially inductors, thereby achieving higher power density. However, as the switching frequency increases further, switching losses also increase significantly, placing higher demands on internal control delays and drivers. Summary of the Invention

[0004] The object of the present invention is to provide a hybrid architecture of a BUCK DC-DC step-down converter to overcome the shortcomings of the prior art.

[0005] The hybrid-architecture buck DC-DC step-down converter provided by the present invention includes several power switches, three switched capacitors, and two switched inductors. The switched capacitors are used to reduce the voltage stress of the input voltage on the power switches, while the switched inductors are used to provide output current capacity. Mode control, including but not limited to a voltage mode or current mode based on pulse width control, a voltage mode or current mode based on constant on-time control, or a voltage mode based on ripple control, is used to convert a high-voltage input voltage into a low-voltage output with high conversion efficiency, high power density, and strong load capacity.

[0006] The hybrid architecture BUCK DC-DC step-down converter provided by the present invention specifically includes: eight power switches, three switch capacitors, two switch inductors and one output capacitor; assisted by a control system and a drive system; wherein:

[0007] The input terminal is connected to the drain of the first power switch, and the source of the first power switch is connected to the positive electrode of the first switch capacitor storing three-fifths of the input voltage, so that the first power switch only needs to withstand two-fifths of the input voltage pressure;

[0008] The source of the first power switch is connected to the drain of the second power switch, and the source of the second power switch is connected to the positive electrode of the second switch capacitor storing two-fifths of the input voltage, so that the second power switch only bears one-fifth of the input voltage pressure;

[0009] The source of the second power switch is connected to the drain of the third power switch, and the source of the third power switch is connected to the positive electrode of the third switch capacitor storing one-fifth of the input voltage, so that the third power switch is only subjected to one-fifth of the input voltage pressure;

[0010] The source of the third power switch is connected to the drains of the fourth and fifth power switches, the negative electrode of the third switch capacitor is connected to the drain of the sixth power switch and the input of the first switch inductor, and the source of the sixth power switch is connected to ground. Due to the stored voltage in the switch capacitor, the drain and source of the sixth power switch only withstand a voltage pressure of one-fifth of the input voltage.

[0011] The output of the first switching inductor is connected to the positive terminal of the output capacitor, while the negative terminal of the output capacitor is connected to ground. The output capacitor provides transient charge to the load to maintain a stable output voltage. The negative terminal of the first switching capacitor is connected to the source of the fifth power switch and the drain of the seventh power switch. The fifth power switch only withstands a voltage stress of one-fifth of the input voltage.

[0012] The source of the seventh power switch is grounded and is subjected to a voltage pressure of two-fifths of the input voltage;

[0013] The negative electrode of the second switch capacitor is connected to the source electrode of the fourth power switch and the drain electrode of the eighth power switch, and the fourth power switch only withstands a voltage pressure of one fifth of the input voltage;

[0014] The source of the eighth power switch is grounded, bearing one fifth of the input voltage, and is also connected to the input of the second switch inductor, while the output of the second switch inductor is connected to the positive electrode of the output capacitor to provide charge for the load;

[0015] The gates of the eight power switches are connected to the drive system, which drives the power switches separately according to the control system. The control system determines the corresponding power switch control by sampling the input voltage, output voltage and inductor current information, and performs the driving task through the drive system.

[0016] The hybrid-architecture buck DC-DC step-down converter provided by the present invention can achieve high-voltage input conversion using power switches with lower voltage resistance, significantly reducing the size of the power switches, lowering their driving and switching losses, and improving their conversion efficiency. Furthermore, due to the hybrid architecture, the voltage at the input terminals of the two switching inductors is reduced from the input voltage of a traditional half-bridge to one-fifth of the input voltage, significantly reducing the conduction losses of the sixth and eighth power switches. Simultaneously, the equivalent switching frequency is increased fivefold, significantly reducing the inductance value, and thus improving the system's power density. This invention addresses the problems existing in the application of the traditional half-bridge buck DC-DC architecture to high step-down ratios and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The diagram shows the structure of a hybrid BUCK DC-DC buck converter for high voltage input and high step-down ratio.

[0018] Figure 2Schematic diagram of power switch control for charging the first switching inductor and freewheeling the second switching inductor in a buck converter.

[0019] Figure 3 Schematic diagram of power switch control for charging the second switching inductor and freewheeling the first switching inductor in a buck converter.

[0020] Figure 4 A schematic diagram of the drive system.

[0021] Figure 5 This is a structural diagram of the control system. DETAILED DESCRIPTION

[0022] The present invention will be described in more detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, rather than all of the components.

[0023] Many specific details of the present invention, such as control timing and techniques, are described below to provide a clearer understanding of the present invention. However, as will be appreciated by those skilled in the art, the present invention may be implemented without these specific details.

[0024] The schematic diagram of the BUCK DC-DC step-down converter structure of the hybrid architecture of the present invention is as follows: Figure 1 As shown; the buck converter 100 of the present invention includes eight power switches with different voltage requirements, three switch capacitors storing different voltages, two identical switch inductors, and an output capacitor; the drive system 200 includes dead zone control, a level shift circuit and a drive circuit to achieve fast opening and closing of the eight power switches; the control system 300 includes output voltage sampling, inductor current sampling, error judgment and comparison, timing generation circuit, etc.

[0025] The power switch control schematic diagram of the present invention in which the first switch inductor is charged and the second switch inductor is freewheeling is shown as follows: Figure 2 As shown. Among them:

[0026] The first power switch, the third power switch, the fifth power switch, and the eighth power switch are turned on; the second power switch, the fourth power switch, the sixth power switch, and the seventh power switch are turned off; the input voltage charges the first switch inductor through the first power switch, the first switch capacitor, the fifth power switch, and the third switch capacitor, while the second switch capacitor charges the first switch inductor through the eighth power switch, the third power switch, and the third switch capacitor; and the second switch inductor is discharged through the eighth power switch.

[0027] The power switch control diagram of the second switch inductor charging and the first switch inductor freewheeling in the present invention is as follows: Figure 3 As shown. Among them:

[0028] The second power switch, the fourth power switch, the sixth power switch, and the seventh power switch are turned on; the first power switch, the third power switch, the fifth power switch, and the eighth power switch are turned off; the first switch capacitor charges the second switch inductor through the seventh power switch, the second power switch, and the second switch capacitor, while the third switch capacitor charges the second switch inductor through the sixth power switch and the fourth power switch; and the first switch inductor is discharged through the sixth power switch.

[0029] The structural diagram of the drive system 200 in the present invention is as follows Figure 4 The driving system consists of dead zone control, level shift and driving circuit. Since the driving system is not the focus of the present invention, it is illustrated with a functional frame.

[0030] The structural diagram of the control system 300 in the present invention is as follows Figure 5 The control system consists of output voltage sampling, inductor current sampling, error judgment and comparison, and control timing generation. Since the drive system is not the focus of this invention, it is illustrated with a functional frame.

Claims

1. A hybrid architecture BUCK DC-DC step-down converter, characterized in that: The system comprises a plurality of power switches, three switching capacitors and two switching inductors; the switching capacitors are used to reduce the voltage pressure of the input voltage on the power switches, while the switching inductors are used to provide output current capability. Mode control is used, including voltage mode or current mode control based on pulse width control, voltage mode or current mode control based on constant on-time control, or voltage mode control based on ripple control, to achieve conversion of high-voltage input voltage into low-voltage output with high conversion efficiency, high power density and strong load capacity; Its structure includes: eight power switches, three switch capacitors, two switch inductors and one output capacitor; V IN is the input terminal, V OUT It is the output terminal, GND is the ground, and it assists the control system and drive system; among them: The input terminal is connected to the drain of the first power switch, and the source of the first power switch is connected to the positive electrode of the first switch capacitor storing three-fifths of the input voltage, so that the first power switch only needs to withstand two-fifths of the input voltage pressure; The source of the first power switch is connected to the drain of the second power switch, and the source of the second power switch is connected to the positive electrode of the second switch capacitor storing two-fifths of the input voltage, so that the second power switch only bears one-fifth of the input voltage pressure; The source of the second power switch is connected to the drain of the third power switch, and the source of the third power switch is connected to the positive electrode of the third switch capacitor storing one-fifth of the input voltage, so that the third power switch is only subjected to one-fifth of the input voltage pressure; The source of the third power switch is connected to the drains of the fourth and fifth power switches, the negative electrode of the third switch capacitor is connected to the drain of the sixth power switch and the input of the first switch inductor, and the source of the sixth power switch is connected to ground. Due to the stored voltage in the switch capacitor, the drain and source of the sixth power switch only withstand a voltage pressure of one-fifth of the input voltage. The output of the first switching inductor is connected to the positive terminal of the output capacitor, while the negative terminal of the output capacitor is connected to ground. The output capacitor provides transient charge to the load to maintain a stable output voltage. The negative terminal of the first switching capacitor is connected to the source of the fifth power switch and the drain of the seventh power switch. The fifth power switch only withstands a voltage stress of one-fifth of the input voltage. The source of the seventh power switch is grounded and is subjected to a voltage pressure of two-fifths of the input voltage; The negative electrode of the second switch capacitor is connected to the source electrode of the fourth power switch and the drain electrode of the eighth power switch, and the fourth power switch only withstands a voltage pressure of one fifth of the input voltage; The source of the eighth power switch is grounded, bearing one fifth of the input voltage, and is also connected to the input of the second switch inductor, while the output of the second switch inductor is connected to the positive electrode of the output capacitor to provide charge for the load.

2. The hybrid architecture BUCK DC-DC step-down converter according to claim 1, wherein: The gates of the eight power switches are connected to the drive system, which drives the power switches separately according to the control system. The control system determines the corresponding power switch control by sampling the input voltage, output voltage and inductor current information, and performs the driving task through the drive system.

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