A capacitor isolated boost-buck converter topology

Abstract

This invention relates to the field of converter technology, and particularly to a capacitor-isolated buck-boost converter topology. It includes a switching transistor, a first energy storage inductor, a second energy storage inductor, a first isolation capacitor, a second isolation capacitor, a diode D, and an output filter capacitor. C o This invention achieves energy transfer and electrical isolation between the input and output sides through a capacitor isolation network. Compared to traditional magnetically isolated buck-boost converters, the converter provided by this invention eliminates the need for a high-frequency transformer, avoiding the spike problems caused by parasitic parameters of the high-frequency transformer and reducing the size of the system's magnetic components. Simultaneously, the isolation capacitor in this invention does not withstand DC bias voltage, exhibiting zero-mean voltage characteristics and improving the operational reliability of the isolation devices. This converter boasts advantages such as high power density, high efficiency, and low cost, making it suitable for isolated DC-DC conversion applications.

Description

Technical Field

[0001] This invention relates to the field of converter technology, and in particular to a capacitor-isolated buck-boost converter topology. Background Technology

[0002] Photovoltaic power generation is one of the most representative applications in the field of new energy power generation, with advantages such as flexible distributed access and wide application scenarios. Typical application scenarios include photovoltaic-storage DC microgrids, residential photovoltaic energy storage systems, and indoor DC power supply systems. In these systems, the output voltage of photovoltaic modules varies over a wide range due to the influence of light intensity, ambient temperature, and operating conditions, typically requiring a step-up / step-down isolated converter to achieve maximum power point tracking, bus voltage stabilization, and energy matching. Traditional isolated step-up / step-down converters introduce high-frequency transformers, which suffer from problems such as large transformer size, significant leakage inductance spikes, high losses, and complex high-frequency transformer design, hindering efficiency and power density improvements. Summary of the Invention

[0003] To address the shortcomings of existing technologies, this invention provides a capacitor-isolated buck-boost converter topology, which aims to solve the problems of large high-frequency transformer size, significant leakage inductance spikes, and low efficiency in traditional isolated buck-boost converters, thereby improving the power conversion efficiency and operational reliability of the entire system.

[0004] To achieve the above objectives, the present invention provides a capacitor-isolated buck-boost converter topology, comprising: a switching transistor S and a first energy storage inductor. L 1. Second energy storage inductor L 2. First isolation capacitor C 1. Second isolation capacitor C 2. Diode D and output filter capacitor C o ; One end of the switching transistor S is connected to the DC input power supply. V in The positive terminal is connected, and the other end is connected to the first energy storage inductor. L 1 and the first isolation capacitor C 1. The first terminal is connected; the first energy storage inductor L The second terminal of 1 is connected to the second isolation capacitor. C 2's first terminal, DC input power supply V in The negative terminal connection; the first isolation capacitor C The second terminal of 1 is connected to the second energy storage inductor. L The first terminal of 2 is connected to the anode of diode D; the cathode of diode D is connected to the output filter capacitor. C o The first terminal is connected to form the negative terminal of the output voltage; the second isolation capacitor CThe second terminal of 2 is connected to the second energy storage inductor. L The second terminal of 2 and the second terminal of the output filter capacitor are connected to form the positive terminal of the output voltage.

[0005] Furthermore, the DC input power supply V in Sequentially connected to the switching transistor S and the first energy storage inductor L 1. Connected in series to form the first closed loop; The DC input power supply V in Sequentially connected to the switching transistor S and the first isolation capacitor C 1. Second energy storage inductor L 2. Second isolation capacitor C 2 are connected in series to form a second closed loop; First energy storage inductor L 1. Sequentially connected to the second isolation capacitor C 2. Output filter capacitor C o Diode D, First isolation capacitor C 1. Connected in series to form the first freewheeling circuit; Second energy storage inductor L 2. Sequential connection with output filter capacitors C o Diode D is connected in series to form a second freewheeling circuit; The output filter capacitor C o It forms a third freewheeling loop with the output load R.

[0006] Furthermore, the first isolation capacitor C 1 and the second isolation capacitor C The capacitance values ​​of 2 are equal; The first isolation capacitor C 1 and second isolation capacitors C The capacitance value of 2 satisfies: The equivalent isolation capacitor C eq and equivalent energy storage inductance L eq The resulting resonant frequency satisfies: in: I L2 For the second energy storage inductor current, D The duty cycle of the switching transistor S is the on-state. T sThe switching cycle of the switching transistor S. V c This refers to the allowable voltage ripple of the isolation capacitor. f LC It is the equivalent resonant frequency. f s It is the switching frequency of the switching transistor S.

[0007] Furthermore, the capacitor-isolated buck-boost converter has two operating modes within one cycle; Mode 1: Switch S is off, diode D is on, and the capacitor-isolated buck-boost converter is in freewheeling mode; at time t1, switch S is on, diode D is off, and the DC input power supply... V in With the first energy storage inductor L 1. This forms the input-side energy storage circuit, and the current of the switch S... i S and the first energy storage inductor current i L1 The first isolation capacitor increases linearly. C 1. Second energy storage inductor L 2. Second isolation capacitor C 2. With its corresponding DC input power supply V in This forms an isolated energy transfer circuit, and the current of the second energy storage inductor... i L2 Linear increase, first energy storage inductor L 2 and second isolation capacitor C 2. Participates in energy transfer; during mode 1, the output filter capacitor... C o Power is supplied to the load R; Mode 2: When the switch S is turned off, since the currents of the first and second energy storage inductors cannot change abruptly, the diode D is turned on, and the first energy storage inductor... L 1. First isolation capacitor C 1. Second energy storage inductor L 2. Second isolation capacitor C 2. Diode D, output filter capacitor, and load R constitute the energy storage circuit; in this mode, the first energy storage inductor... L 1 and second energy storage inductors L 2. Energy is released and transmitted to the output side via a capacitor isolation network, affecting the output filter capacitor. C o Power supply to the load R.

[0008] Furthermore, the first isolation capacitor C 1. Second isolation capacitor C Both use film, CBB, or ceramic capacitors.

[0009] Furthermore, the switching transistor S is a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor.

[0010] Furthermore, the switching transistor S is controlled by pulse width modulation.

[0011] The beneficial effects of this invention are: 1. This invention achieves electrical isolation between the input and output sides solely through a capacitor isolation network. Compared to the magnetic isolation method of traditional buck-boost isolation converters, the converter provided by this invention is suitable for high-frequency operation and small-size applications. It improves power conversion efficiency while optimizing power density.

[0012] 2. The converter provided by this invention has an average isolation capacitor voltage of zero, which effectively eliminates the DC bias voltage, significantly reduces the withstand voltage requirements of passive components, and saves component costs. Attached Figure Description

[0013] Figure 1 This is a schematic diagram of the topology of a capacitor-isolated buck-boost converter according to an embodiment of the present invention.

[0014] Figure 2 is a circuit diagram of mode 1 to mode 2 of the capacitor-isolated buck-boost converter in steady state according to an embodiment of the present invention.

[0015] Figure 3 This is a schematic diagram of the main waveforms of the capacitor-isolated buck-boost converter in steady state according to an embodiment of the present invention.

[0016] in: V GS This represents the gate-source voltage of the switching transistor S. V DS This represents the drain-source voltage of the switching transistor S. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below in conjunction with the accompanying drawings and embodiments. The described embodiments should not be considered as limitations on this application, and all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this application.

[0018] In the following description, references to "some embodiments" or "one or more embodiments" describe a subset of all possible embodiments. However, it is understood that "some embodiments" or "one or more embodiments" may be the same subset or different subsets of all possible embodiments and may be combined with each other without conflict.

[0019] In the following description, the terms "first, second, third" are used only to distinguish similar objects and do not represent a specific ordering of objects. It is understood that "first, second, third" may be interchanged in a specific order or sequence where permitted, so that the embodiments of the present application described herein can be implemented in an order other than that shown in the illustrations or description.

[0020] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing embodiments of this application only and is not intended to limit this application.

[0021] like Figure 1 As shown, this embodiment of the invention provides a capacitor-isolated buck-boost converter topology, including: a DC input power supply. V in Switch S, first energy storage inductor L 1. Second energy storage inductor L 2. First isolation capacitor C 1. Second isolation capacitor C 2. Diode D, Output Filter Capacitor C o and load R.

[0022] In this embodiment of the invention, a DC input power supply V in It can provide DC power to all kinds of devices, such as photovoltaic cells, vehicle batteries, and fuel cells.

[0023] In this topology, one end of the switch S is connected to the DC input power supply. V in The positive terminal is connected, and the other end is connected to the first energy storage inductor. L 1 and the first isolation capacitor C 1. First terminal connection; First energy storage inductor L The second terminal of 1 is connected to the second isolation capacitor. C 2's first terminal, DC input power supply V in Negative terminal connection; first isolation capacitor C The second terminal of 1 is connected to the second energy storage inductor. L The first terminal of diode 2 is connected to the anode of diode D; the cathode of diode D is connected to the output filter capacitor. C o The first terminal is connected to form the negative terminal of the output voltage, and is connected to one end of the load R; the second isolation capacitor C The second terminal of 2 is connected to the second energy storage inductor. L The second terminal of 2 and the second terminal of the output filter capacitor are connected to form the positive terminal of the output voltage, and at the same time connected to the other terminal of the load R.

[0024] DC input power supply V in Sequentially connected to the switching transistor S and the first energy storage inductor L 1. Connected in series to form the first closed loop.

[0025] DC input power supply V in Sequentially connected to the switching transistor S and the first isolation capacitor C 1. Second energy storage inductor L 2. Second isolation capacitor C 2 are connected in series to form a second closed loop.

[0026] First energy storage inductor L 1. Sequentially connected to the second isolation capacitor C 2. Output filter capacitor C o Diode D, First isolation capacitor C 1. Connected in series to form the first freewheeling circuit.

[0027] Second energy storage inductor L 2. Sequential connection with output filter capacitors C o Diode D is connected in series to form a second freewheeling circuit.

[0028] Filter capacitor C o It is connected in series with the output load R to form a third freewheeling circuit.

[0029] In this embodiment of the invention, the first isolation capacitor C 1 and the second isolation capacitor C The capacitance values ​​of the two capacitors are equal. First isolation capacitor. C 1 and second isolation capacitors C The capacitance value of 2 satisfies: Equivalent isolation capacitance C eq and equivalent energy storage inductance L eq The resulting resonant frequency satisfies: in: I L2 For the second energy storage inductor current, D The duty cycle of the switching transistor S is the on-state. T s The switching cycle of the switching transistor S. Vc This refers to the allowable voltage ripple of the isolation capacitor. f LC It is the equivalent resonant frequency. f s It is the switching frequency of the switching transistor S.

[0030] To more clearly illustrate the embodiments of the present invention, the principle of the present invention will be described in detail below. This capacitor-isolated buck-boost converter has two operating modes when operating in CCM mode, as shown in Figure 2. The main operating waveforms are as follows: Figure 3 As shown, the specific description is as follows: Because of the first isolation capacitor C 1 and second isolation capacitors C The capacitance value of 2 is relatively large, so its voltage ripple is ignored. Meanwhile, the first isolation capacitor... C 1 and second isolation capacitors C Since the average voltage of 2 is zero, non-polarized film capacitors can be used in practice.

[0031] The switching transistor S is a metal-oxide-semiconductor field-effect transistor (MOSFET) or an insulated gate bipolar transistor (IGBT), which is controlled by pulse width modulation.

[0032] First energy storage inductor L 1 and second energy storage inductors L The sensitivity of 2 is large enough to ensure operation in CCM mode.

[0033] The two modes are as follows: Operating in Mode 1 from time t1 to t2: Before time t1, switch S is off and diode D is on, and the capacitor-isolated buck-boost converter is in freewheeling mode; at time t1, switch S is on and diode D is off, and the DC input power supply... V in With the first energy storage inductor L 1. This forms the input-side energy storage circuit, and the current of the switch S... i S and the first energy storage inductor current i L1 The first isolation capacitor increases linearly. C 1. Second energy storage inductor L 2. Second isolation capacitor C 2. With its corresponding DC input power supply V in This forms an isolated energy transfer circuit, and the current of the second energy storage inductor... i L2 Linear increase, first energy storage inductor L 2 and second isolation capacitor C2. Participates in energy transfer; during mode 1, the output filter capacitor... C o Power is supplied to the load R; Operating in mode 2 during times t2~t3: the switch S is off. Since the currents of the first and second energy storage inductors cannot change abruptly, the diode D is on, and the first energy storage inductor... L 1. First isolation capacitor C 1. Second energy storage inductor L 2. Second isolation capacitor C 2. Diode D, output filter capacitor, and load R constitute the energy storage circuit; in this mode, the first energy storage inductor... L 1 and second energy storage inductors L 2. Energy is released and transmitted to the output side via a capacitor isolation network, affecting the output filter capacitor. C o Power supply to the load R.

[0034] This invention utilizes a capacitive isolation network to achieve electrical isolation between the input and output sides. Furthermore, it addresses the issues of large high-frequency transformer size and leakage inductance spikes in traditional magnetically isolated buck-boost converters, ultimately optimizing power density and improving energy conversion efficiency.

[0035] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Any modifications, equivalent substitutions, and improvements made within the spirit and scope of this application are included within the scope of protection of this application.

Claims

1. A capacitor-isolated buck-boost converter topology, characterized in that, include: Switching transistor S, first energy storage inductor L 1. Second energy storage inductor L 2. First isolation capacitor C 1. Second isolation capacitor C 2. Diode D and output filter capacitor C o ; One end of the switching transistor S is connected to the DC input power supply. V in The positive terminal is connected, and the other end is connected to the first energy storage inductor. L 1 and the first isolation capacitor C 1. The first terminal is connected; the first energy storage inductor L The second terminal of 1 is connected to the second isolation capacitor. C 2's first terminal, DC input power supply V in The negative terminal connection; the first isolation capacitor C The second terminal of 1 is connected to the second energy storage inductor. L The first terminal of 2 is connected to the anode of diode D; the cathode of diode D is connected to the output filter capacitor. C o The first terminal is connected to form the negative terminal of the output voltage; the second isolation capacitor C The second terminal of 2 is connected to the second energy storage inductor. L The second terminal of 2 and the second terminal of the output filter capacitor are connected to form the positive terminal of the output voltage.

2. The capacitor-isolated buck-boost converter topology according to claim 1, characterized in that: The DC input power supply V in Sequentially connected to the switching transistor S and the first energy storage inductor L 1. Connected in series to form the first closed loop; The DC input power supply V in Sequentially connected to the switching transistor S and the first isolation capacitor C 1. Second energy storage inductor L 2. Second isolation capacitor C 2 are connected in series to form a second closed loop; First energy storage inductor L 1. Sequentially connected to the second isolation capacitor C 2. Output filter capacitor C o Diode D, First isolation capacitor C 1. Connected in series to form the first freewheeling circuit; Second energy storage inductor L 2. Sequential connection with output filter capacitors C o Diode D is connected in series to form a second freewheeling circuit; The output filter capacitor C o It forms a third freewheeling loop with the output load R.

3. The capacitor-isolated buck-boost converter topology according to claim 1, characterized in that: The first isolation capacitor C 1 and the second isolation capacitor C The capacitance values ​​of 2 are equal; The first isolation capacitor C 1 and second isolation capacitors C The capacitance of 2 satisfies: The equivalent isolation capacitor C eq and equivalent energy storage inductance L eq The resulting resonant frequency satisfies: in: I L2 For the second energy storage inductor current, D The duty cycle of the switching transistor S is the on-state. T s The switching cycle of the switching transistor S. V c This refers to the allowable voltage ripple of the isolation capacitor. f LC It is the equivalent resonant frequency. f s It is the switching frequency of the switching transistor S.

4. The capacitor-isolated buck-boost converter topology according to claim 1, characterized in that: The capacitor-isolated buck-boost converter has two operating modes within one cycle; Mode 1: Switch S is off, diode D is on, and the capacitor-isolated buck-boost converter is in freewheeling mode; at time t1, switch S is on, diode D is off, and the DC input power supply... V in With the first energy storage inductor L 1. This forms the input-side energy storage circuit, and the current of the switch S... i S and the first energy storage inductor current i L1 The first isolation capacitor increases linearly. C 1. Second energy storage inductor L 2. Second isolation capacitor C 2. With its corresponding DC input power supply V in This forms an isolated energy transfer circuit, and the current of the second energy storage inductor... i L2 Linear increase, first energy storage inductor L 2 and second isolation capacitor C 2. Participates in energy transfer; during mode 1, the output filter capacitor... C o Power is supplied to the load R; Mode 2: When the switch S is turned off, since the currents of the first and second energy storage inductors cannot change abruptly, the diode D is turned on, and the first energy storage inductor... L 1. First isolation capacitor C 1. Second energy storage inductor L 2. Second isolation capacitor C 2. Diode D, output filter capacitor, and load R constitute the energy storage circuit; in this mode, the first energy storage inductor... L 1 and second energy storage inductors L 2. Energy is released and transmitted to the output side via a capacitor isolation network, affecting the output filter capacitor. C o Power supply to the load R.

5. The capacitor-isolated buck-boost converter topology according to claim 1, characterized in that: The first isolation capacitor C 1. Second isolation capacitor C Both use film, CBB, or ceramic capacitors.

6. The capacitor-isolated buck-boost converter topology according to claim 1, characterized in that: The switching transistor S is a metal-oxide-semiconductor field-effect transistor or an insulated-gate bipolar transistor.

7. The capacitor-isolated buck-boost converter topology according to claim 1, characterized in that: The switching transistor S is controlled by pulse width modulation.

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