Biphase hybrid buck converter

Abstract

The invention belongs to the technical field of converters, and particularly relates to a two-phase hybrid buck converter. A switched capacitor converter and a switched inductor converter are combined, a flying capacitor is used for bearing half of input voltage, and meanwhile, a bus capacitor is used as an intermediate node, so that the voltage swing of a switch node is reduced to half of the input voltage. Therefore, the switching stress of the power device is reduced, the switching loss is reduced, meanwhile, the power device with relatively low withstand voltage can be used, the conduction resistance is reduced, and the conduction loss is reduced. Flying capacitor voltage self-balancing and inductance self-current-sharing can be achieved, even double-phase output is achieved, an additional current-sharing circuit is not needed, and circuit expenditure is reduced. And the bus nodes of a plurality of units can be conveniently connected together so as to realize multiphase expansion, reduce output voltage ripples and improve current output capability.

Description

Technical Field

[0001] This invention belongs to the field of converter technology, specifically relating to a two-phase hybrid buck converter. Background Technology

[0002] With the increasing demands for energy efficiency and power density from portable electronic devices, computing devices, and other power systems, the structural design of DC-DC converters faces greater challenges. To improve the efficiency of DC-DC converters, existing technologies typically employ switched capacitors to preprocess the input voltage, thereby reducing the switching stress on power devices and minimizing switching losses. For example... Figure 1 As shown, the two-stage architecture of switched capacitor + Buck typically requires more power switches and control units, which increases the system complexity. Furthermore, the single-phase structure limits its current output capability, and the switching losses caused by too many power switches also limit the improvement of efficiency.

[0003] The hybrid topology combines the advantages of switched-capacitor converters and switched-inductor converters, simplifying the two-stage architecture into a single-stage architecture. It also reduces switching stress and allows for the use of flying capacitors to balance the inductor currents across phases in multi-phase output applications. For example... Figure 2 The DSD converter shown is one such example. The flying capacitor handles half of the input voltage, reducing switching stress, and the two-phase output improves load-carrying capacity. However, it doesn't completely avoid the use of high-voltage components; switch S2 bears the switching stress of twice the input voltage. Furthermore, due to its operating principle, the DSD converter can only operate with a duty cycle less than 50%. A duty cycle greater than 50% will cause overvoltage, resulting in an imbalance between the flying capacitor voltage and inductor current. This limits its maximum voltage conversion ratio to 0.25. The duty cycle limitation also leads to a limited inductor current rise rate during transients, resulting in poor transient response. Summary of the Invention

[0004] To address the aforementioned issues, this invention proposes a two-phase hybrid buck converter that utilizes a flying capacitor to handle part of the input voltage and a bus capacitor as an intermediate power supply node. The switching stress on all power devices is only half the input voltage, effectively reducing switching losses and improving voltage conversion efficiency. Furthermore, it eliminates duty cycle limitations, enabling a wide output range. It is also easily scalable, allowing for convenient multi-phase expansion to enhance current output capability.

[0005] The technical solution adopted in this invention is:

[0006] A two-phase hybrid buck converter, characterized in that it includes a DC input power supply V IN First switch S1, second switch S2, third switch S3, fourth switch S4, fifth switch S5, first inductor L1, second inductor L2, bus capacitor CBUS Flying capacitor C F Output capacitor C L ;

[0007] The first terminal of the first switch S1 is connected to the input power supply V. IN The second terminal of the first switch S1 is connected to the first terminal of the second switch S2 and the flying capacitor C, respectively. F The positive end;

[0008] The second terminal of the second switch S2 is connected to the bus capacitor C. BUS The positive terminal and the first terminal of the third switch S3;

[0009] The second end of the third switch S3 is connected to the first end of the fourth switch S4 and the first end of the second inductor L2, respectively.

[0010] The flying capacitor C F The negative terminals are respectively connected to the first terminal of the fifth switch S5 and the first terminal of the first inductor L1;

[0011] The output capacitor C L The positive terminals are respectively connected to the second terminals of the first inductor L1 and the second inductor L2;

[0012] The bus capacitor C BUS The negative terminal, the second terminal of the fourth switch S4, the second terminal of the fifth switch S5, and the output capacitor C L The negative terminals are all grounded;

[0013] The converter includes four operating states, defined as state 1, state 2, state 3, and state 4:

[0014] In the first state, the first switch S1 and the fourth switch S4 are closed, and the second switch S2, the third switch S3, and the fifth switch S5 are open. At this time, the voltage at the connection point SW1 between the first switch S1 and the second switch S2 is V. IN Fifth switch S5, flying capacitor C F The voltage at connection point SW2 is V. IN -V BUS The voltage at the connection point SW3 of the third switch S3 and the fourth switch S4 is 0, and the voltage across the first inductor L1 is V. IN -V BUS -V OUT If V is positive, OUT It is the output voltage, therefore the current in the first inductor L1 increases linearly, and the voltage across the second inductor L2 is -V. OUT Since the value is negative, the current in the second inductor L2 decreases linearly, and the flying capacitor C... FIt is connected in series with the first inductor L1, and the current in the first inductor L1 is equal to the current in the flying capacitor C. F Replenish charge;

[0015] In the second state, the second switch S2, the third switch S3, and the fifth switch S5 are closed, while the first switch S1 and the fourth switch S4 are open; at this time, the voltage at the connection point SW1 is V. BUS The voltage at node SW2 is 0, and the voltage at node SW3 is V. BUS The voltage across the first inductor L1 is -V OUT Since the value is negative, the current in the first inductor L1 decreases linearly, and the voltage V across the second inductor L2... BUS -V OUT Since the value is positive, the current in the second inductor L2 increases linearly, and the flying capacitor C... F With bus capacitor C BUS Parallel connection, flying capacitor C F For bus capacitor C BUS Provide charge;

[0016] In the third state, the second switch S2, the fourth switch S4, and the fifth switch S5 are closed, while the first switch S1 and the third switch S3 are open; at this time, the voltage at the connection point SW1 is V. BUS The voltage at connection point SW2 is 0, and the voltage at connection point SW3 is 0; the voltage across the first inductor L1 is -V. OUT Since the value is negative, the current in the first inductor L1 decreases linearly, and the voltage across the second inductor L2 is -V. OUT Since the value is negative, the current in the second inductor L2 decreases linearly, and the flying capacitor C... F With bus capacitor C BUS Parallel connection, flying capacitor C F For bus capacitor C BUS Provide charge;

[0017] In the fourth state, the first switch S1 and the third switch S3 are closed, while the second switch S2, the fourth switch S4, and the fifth switch S5 are open; at this time, the voltage at the connection point SW1 is V. IN The voltage at node SW2 is V. IN -V BUS The voltage at node SW3 is V. BUS The voltage V across the first inductor L1 IN -V BUS -V OUT Since the value is positive, the current in the first inductor L1 increases linearly, and the voltage V across the second inductor L2... BUS -V OUT Since the value is positive, the current in the second inductor L2 increases linearly, and the flying capacitor C... F It is connected in series with the first inductor L1, and the current in the first inductor L1 is equal to the current in the flying capacitor C. FTo replenish the charge, the second inductor L2 draws from the bus capacitor C. BUS Extract charge;

[0018] When the duty cycle of the switch control signal is less than 0.5, the converter cycles through the first state, the second state, the third state, and the second state. When the duty cycle of the switch control signal is greater than or equal to 0.5, the converter cycles through the first state, the fourth state, the third state, and the fourth state.

[0019] Furthermore, the first switch S1, the second switch S2, and the third switch S3 are all made of one of the following devices: MOSFET, IGBT, or GaN HEMT.

[0020] Furthermore, the fourth switch S4 and the fifth switch S5 are made of one of the following devices: diode, MOSFET, IGBT, and GaNHEMT.

[0021] The beneficial effects of this invention are as follows: This invention combines a switched-capacitor converter and a switched-inductor converter, utilizing a flying capacitor to bear half of the input voltage, while employing a bus capacitor as an intermediate node, thus reducing the voltage swing of the switching node to half of the input voltage. This reduces the switching stress on power devices, decreases switching losses, and allows the use of power devices with lower withstand voltage, reducing on-resistance and conduction losses. It achieves self-balancing of the flying capacitor voltage and self-current sharing of the inductor, eliminating the need for additional current sharing circuits even in two-phase outputs, reducing circuit overhead. It is easily scalable, allowing multiple units to be conveniently connected to achieve multi-phase expansion, reducing output voltage ripple and increasing current output capability. Attached Figure Description

[0022] Figure 1 This is a circuit diagram of a two-stage architecture: switched capacitor and Buck.

[0023] Figure 2 This is a DSD topology circuit diagram;

[0024] Figure 3 The circuit diagram of the two-phase hybrid buck converter proposed in this invention is shown below.

[0025] Figure 4 These are schematic diagrams illustrating different states in embodiments of the present invention;

[0026] Figure 5 This is a schematic diagram of the working waveforms in an embodiment of the present invention;

[0027] Figure 6 This is a multiphase parallel circuit diagram according to an embodiment of the present invention. Detailed Implementation

[0028] The method of the present invention will now be described in detail with reference to the accompanying drawings.

[0029] Appendix Figure 3 This is a circuit diagram of the power stage topology of the present invention, including a DC input power supply V. IN First switch S1, second switch S2, third switch S3, fourth switch S4, fifth switch S5, first inductor L1, second inductor L2, bus capacitor C BUS Flying capacitor C F Output capacitor CL, load resistor R L The dual-phase hybrid buck converter proposed in this invention adds a flying capacitor to the traditional dual-phase Buck converter to absorb the voltage drop, reducing the voltage stress on the power switching transistors to V. IN / 2, which improves its energy conversion efficiency. Furthermore, the flying capacitor in the topology automatically balances the current in the two-phase inductors, eliminating the need for additional auxiliary current sharing circuits. The intermediate node V can also be utilized. BUS It facilitates multiphase expansion.

[0030] As attached Figure 4 As shown, depending on the different switching conditions, this invention has four operating states: State 1, State 2, State 3, and State 4. As will be seen later, in the stable state, the flying capacitor C... F Voltage and bus capacitance C BUS The voltages are equal, and are V. BUS .

[0031] In state 1, switches S1 and S4 are closed, and switches S2, S3, and S5 are open. At this time, the voltage at switch node SW1 is V. IN The voltage of SW2 is V. IN -V BUS The voltage across SW3 is 0. The voltage across inductor L1 is V. IN -V BUS -V OUT Since the current is positive, the current in L1 increases linearly, and the voltage across inductor L2 is -V. OUT Since the value is negative, the current in L2 decreases linearly. Flying capacitor C F It is connected in series with inductor L1, and the current in L1 is C. F Replenish the charge.

[0032] In state 2, switches S2, S3, and S5 are closed, and switches S1 and S4 are open. At this time, the voltage at switch node SW1 is V. BUS The voltage at switch node SW2 is 0, and the voltage at switch node SW3 is V. BUS The voltage across inductor L1 is -V. OUT Since the value is negative, the current in L1 decreases linearly, and the voltage across inductor L2 is V. BUS -V OUTSince the value is positive, the current in L2 increases linearly. The flying capacitor C... F With bus capacitor C BUS Parallel, C F C BUS Provides electrical charge.

[0033] In state 3, switches S2, S4, and S5 are closed, while switches S1 and S3 are open. At this time, the voltage at switch node SW1 is V. BUS The voltage at switch node SW2 is 0, and the voltage at switch node SW3 is 0. The voltage across inductor L1 is -V. OUT Since the value is negative, the current in L1 decreases linearly, and the voltage across inductor L2 is -V. OUT Since the value is negative, the current in L2 decreases linearly. Flying capacitor C F With bus capacitor C BUS Parallel, C F C BUS Provides electrical charge.

[0034] In state 4, switches S1 and S3 are closed, and switches S2, S4, and S5 are open. At this time, the voltage at switch node SW1 is V. IN The voltage at switch node SW2 is V. IN -V BUS The voltage of SW3 is V. BUS The voltage across inductor L1 is V. IN -V BUS -V OUT Since the value is positive, the current in L1 increases linearly, and the voltage across inductor L2 is V. BUS -V OUT Since the value is positive, the current in L2 increases linearly. The flying capacitor C... F It is connected in series with inductor L1, and the current in L1 is C. F To replenish the charge, inductor L2 draws from bus capacitor C. BUS Extracting charge.

[0035] Appendix Figure 5The waveform diagrams shown in this embodiment of the invention illustrate the different duty cycles. Control signals D1 and D2 are PWM waves with equal frequency and duty cycle, but 180° out of phase. D1 controls switches S1, S2, and S5; when D1 is high, S1 is closed and S2 and S5 are open; when D1 is low, S1 is open and S2 and S5 are closed. D2 controls switches S3 and S4; when D2 is high, S3 is closed and S4 is open; when D2 is low, S3 is open and S4 is closed. Unlike the DSD topology, which has a duty cycle limitation of D < 0.5, the two-phase hybrid converter proposed in this invention can still operate normally when D > 0.5, exhibiting a wide-range output characteristic. When D < 0.5, the converter cycles through states 1, 3, 2, and 3; when D = 0.5, the converter cycles through states 1 and 2; when D > 0.5, the converter cycles through states 1, 4, 2, and 4.

[0036] For ease of derivation, let T be the period of control signals D1 and D2, and D be the duty cycle. From the above analysis, it can be seen that within one cycle, the charging time of inductors L1 and L2 is D*T, and the discharging time is (1-D)*T. Under steady-state conditions, the increase in current of the inductor within one cycle is equal to the decrease.

[0037] For inductor L1, the equation can be obtained:

[0038] ,

[0039] For inductor L2, the equation can be obtained:

[0040] ,

[0041] Combining the two equations, we get:

[0042] ,

[0043] Therefore, the intermediate bus voltage V BUS The value is V IN / 2, thus the voltage swings of switching nodes SW1, SW2, and SW3 are all V. IN / 2, thus reducing the switching stress on power devices. Furthermore, this topology has a voltage conversion ratio of D / 2 and is unrestricted by duty cycle, enabling 0-V... IN Wide output range of / 2 voltage.

[0044] For C F and C BUS Overall, when D1 is high, the inductor current I L1 To replenish its charge, when D2 is high, the inductor current I... L2If charge is extracted from it, the net change in charge over one period in a steady state is 0. And I L1 and I L2 The sum is the load current I OUT Therefore, the equation can be written as follows:

[0045] ,

[0046] Thus, I can be obtained L1 =I L2 =I LOAD / 2, meaning the topology itself can achieve self-current sharing of the inductor.

[0047] Appendix Figure 6 In the case where the present invention is configured as a multi-phase parallel output, the V of each unit circuit is... IN V BUS V OUT By connecting them individually, multi-phase parallel output can be achieved, thereby reducing output voltage ripple and improving load capacity. The analysis is similar to the above; when N unit circuits are connected in parallel, the relevant parameter expressions are:

[0048] ,

[0049] As can be seen from the above specific implementation, this two-phase hybrid buck converter combines the advantages of a two-phase Buck converter and a hybrid converter. It utilizes a flying capacitor to handle half of the input voltage and a bus capacitor as an intermediate power supply node. The switching stress of all power devices is only half of the input voltage, effectively reducing the switching losses of the power devices and improving voltage conversion efficiency compared to traditional converters. Simultaneously, it overcomes the shortcomings of traditional DSD converters, eliminating duty cycle limitations, achieving a wide output range, and possessing easy scalability, allowing for convenient multi-phase expansion to reduce output voltage ripple and increase current output capability.

Claims

1. A two-phase hybrid buck converter, characterized in that, Including DC input power supply V IN First switch S1, second switch S2, third switch S3, fourth switch S4, fifth switch S5, first inductor L1, second inductor L2, bus capacitor C BUS Flying capacitor C F Output capacitor C L ; The first terminal of the first switch S1 is connected to the input power supply V. IN The second terminal of the first switch S1 is connected to the first terminal of the second switch S2 and the flying capacitor C, respectively. F The positive end; The second terminal of the second switch S2 is connected to the bus capacitor C. BUS The positive terminal and the first terminal of the third switch S3; The second end of the third switch S3 is connected to the first end of the fourth switch S4 and the first end of the second inductor L2, respectively. The flying capacitor C F The negative terminals are respectively connected to the first terminal of the fifth switch S5 and the first terminal of the first inductor L1; The output capacitor C L The positive terminals are respectively connected to the second terminals of the first inductor L1 and the second inductor L2; The bus capacitor C BUS The negative terminal, the second terminal of the fourth switch S4, the second terminal of the fifth switch S5, and the output capacitor C L The negative terminals are all grounded; The converter includes four operating states, defined as state 1, state 2, state 3, and state 4: In the first state, the first switch S1 and the fourth switch S4 are closed, and the second switch S2, the third switch S3, and the fifth switch S5 are open. At this time, the voltage at the connection point SW1 between the first switch S1 and the second switch S2 is V. IN Fifth switch S5, flying capacitor C F The voltage at connection point SW2 is V. IN -V BUS The voltage at the connection point SW3 of the third switch S3 and the fourth switch S4 is 0, and the voltage across the first inductor L1 is V. IN -V BUS -V OUT If V is positive, OUT It is the output voltage, therefore the current in the first inductor L1 increases linearly, and the voltage across the second inductor L2 is -V. OUT Since the value is negative, the current in the second inductor L2 decreases linearly, and the flying capacitor C... F It is connected in series with the first inductor L1, and the current in the first inductor L1 is equal to the current in the flying capacitor C. F Replenish charge; In the second state, the second switch S2, the third switch S3, and the fifth switch S5 are closed, while the first switch S1 and the fourth switch S4 are open; at this time, the voltage at the connection point SW1 is V. BUS The voltage at node SW2 is 0, and the voltage at node SW3 is V. BUS The voltage across the first inductor L1 is -V OUT Since the value is negative, the current in the first inductor L1 decreases linearly, and the voltage V across the second inductor L2... BUS -V OUT Since the value is positive, the current in the second inductor L2 increases linearly, and the flying capacitor C... F With bus capacitor C BUS Parallel connection, flying capacitor C F For bus capacitor C BUS Provide charge; In the third state, the second switch S2, the fourth switch S4, and the fifth switch S5 are closed, while the first switch S1 and the third switch S3 are open; at this time, the voltage at the connection point SW1 is V. BUS The voltage at connection point SW2 is 0, and the voltage at connection point SW3 is 0; the voltage across the first inductor L1 is -V. OUT Since the value is negative, the current in the first inductor L1 decreases linearly, and the voltage across the second inductor L2 is -V. OUT Since the value is negative, the current in the second inductor L2 decreases linearly, and the flying capacitor C... F With bus capacitor C BUS Parallel connection, flying capacitor C F For bus capacitor C BUS Provide charge; In the fourth state, the first switch S1 and the third switch S3 are closed, while the second switch S2, the fourth switch S4, and the fifth switch S5 are open; at this time, the voltage at the connection point SW1 is V. IN The voltage at node SW2 is V. IN -V BUS The voltage at node SW3 is V. BUS The voltage V across the first inductor L1 IN -V BUS -V OUT Since the value is positive, the current in the first inductor L1 increases linearly, and the voltage V across the second inductor L2... BUS -V OUT Since the value is positive, the current in the second inductor L2 increases linearly, and the flying capacitor C... F It is connected in series with the first inductor L1, and the current in the first inductor L1 is equal to the current in the flying capacitor C. F To replenish the charge, the second inductor L2 draws from the bus capacitor C. BUS Extract charge; When the duty cycle of the switch control signal is less than 0.5, the converter cycles through the first state, the third state, the second state, and the third state. When the duty cycle of the switch control signal is equal to 0.5, the converter cycles through the first state and the second state. When the duty cycle of the switch control signal is greater than 0.5, the converter cycles through the first state, the fourth state, the second state, and the fourth state.

2. The novel hybrid buck converter according to claim 1, characterized in that, The first switch S1, the second switch S2, and the third switch S3 use one of the following devices: MOSFET, IGBT, and GaN HEMT.

3. The novel hybrid buck converter according to claim 1, characterized in that, The fourth switch S4 and the fifth switch S5 use one of the following devices: diode, MOSFET, IGBT, or GaN HEMT.

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