Battery charger, method and chip based on a continuous variable-ratio capacitor converter

Abstract

The embodiment of the application provides a battery charger based on a continuous variable-ratio capacitor converter, a method and a chip, and belongs to the technical field of power electronics. The charger comprises an input port, an output port, four flying capacitors, a switch network composed of seventeen switches and a controller. The switch network adopts a network connection topology, so that each two flying capacitors are directly connected. The controller executes a predetermined timing control strategy, dynamically reconfigures the capacitor network by periodically operating all switches, so that continuous and efficient voltage conversion is realized within a preset voltage conversion ratio range. By optimizing the topology and control, the number of series conduction switches on the main energy transmission path is significantly reduced from eight in the prior art to five, thereby greatly reducing the path impedance and conduction loss. The actual measurement shows that under the condition of input 12V and output 4.2V, the peak conversion efficiency can reach 92%, and the efficiency remains above 90% in the output current range of up to 3.3A.

Description

Technical Field

[0001] This application relates to the field of power electronics technology, and in particular to a battery charger, method and chip based on a continuous ratio capacitor converter. Background Technology

[0002] In battery charging applications, especially in fast charging scenarios for portable electronic devices, high-efficiency, high-power-density power converters capable of adapting to a wide range of input and output voltages are key components. Currently, mainstream solutions can be categorized as follows: 1) Inductive power converters: such as Figure 1 As shown, this type of converter achieves voltage conversion by controlling the switching transistor to regulate the energy storage and release of the inductor. Its advantages include high conversion efficiency and flexible adjustment. However, to achieve high current transmission, bulky inductors are often required, leading to a reduction in overall power density and making it difficult to meet the demands of increasingly miniaturized devices.

[0003] 2) Fixed conversion ratio switched capacitor power converter: such as Figure 2 As shown, this type of converter operates using the charge pump principle of capacitors, offering potential advantages such as low switching losses, fast transient response, and high power density. However, its peak efficiency is heavily dependent on a specific input-output voltage ratio (e.g., 2:1). In practical fast charging applications, to match different battery voltages, complex pre- or post-stage regulation circuits (such as Buck or Boost converters) must be added. This not only increases the complexity and cost of the system but also negates its original power density advantage.

[0004] 3) Continuously Turning Capacitor Power Converter: To overcome the limitation of a fixed conversion ratio, researchers have proposed, for example... Figure 3 The diagram shows a continuous-ratio converter. Theoretically, this type of converter can achieve continuous voltage conversion within a certain range by switching the connection of multiple flying capacitors. However, the existing architecture has significant drawbacks: firstly, its charging and discharging path typically requires current to flow through a large number of series-connected switching elements, such as... Figure 5 As shown, the high path impedance leads to high conduction losses, which limits the maximum output power. Secondly, there are multiple "ineffective phases" in its switching sequence that do not participate in effective energy transmission, which further reduces the actual usable output power capability and overall efficiency. Summary of the Invention

[0005] The main objective of this application is to propose a battery charger, method, and chip based on a continuously variable capacitor converter, aiming to solve the technical problems of large charging and discharging path impedance, many invalid phases, and limited output power and efficiency of the existing continuously variable capacitor converter.

[0006] To achieve the above objectives, one aspect of this application proposes a battery charger based on a continuously variable capacitor converter, comprising: The input port is used to connect an input voltage source; The output port is used to connect the battery to be charged. Four flying capacitors ( ); The switching network consists of seventeen switches ( to ), used to connect the four flying capacitors in a network connection topology, wherein every two flying capacitors are directly connected by a switch; The controller is configured to execute a predetermined timing control strategy, which dynamically reconfigures the network connection mode of the four flying capacitors by periodically controlling the on and off of the seventeen switches, so that the converter can achieve continuously adjustable voltage conversion within a preset voltage conversion ratio range and provide charging current for the battery.

[0007] In some embodiments, one end of each flying capacitor is connected to the input port or the output port via at least one switch, and the other end is connected to the common ground or the output port via at least one switch.

[0008] In some embodiments, the predetermined timing control strategy includes multiple repetitive switching cycles, each containing at least three different operating states, including: Charging status: Connect at least one flying capacitor to the input port for charging; Boost transmission mode: Connect at least one charged flying capacitor in series with the input source to boost the output voltage; Charge redistribution state: Charge transfer occurs between flying capacitors to maintain voltage balance by reconfiguring network connections.

[0009] In some embodiments, the controller is configured to control the switching network such that the number of switches connected in series on the main power transmission path does not exceed five during each switching cycle.

[0010] In some embodiments, the battery charger has a peak power conversion efficiency of not less than 92% when the input voltage is 12V and the output voltage is 4.2V, and the power conversion efficiency remains above 90% when the charging current reaches 3.3A.

[0011] In some embodiments, the battery charger is a switched capacitor DC-DC converter, which does not require a pre-stage voltage regulation circuit and can directly adapt to various fast charging protocols.

[0012] In some embodiments, the preset voltage conversion ratio ranges from 0.25 to 0.5.

[0013] In some embodiments, the controller is further configured to adjust the voltage conversion ratio in real time based on a feedback signal of the output port voltage or battery charging current.

[0014] To achieve the above objectives, another aspect of this application provides a method for controlling a battery charger as described above, comprising the steps of: A switch network consisting of four flying capacitors and seventeen switches is provided, wherein every two flying capacitors are directly connected through a switch; The controller generates periodic switching control signals; According to the control signal, the connection state of the switching network is switched sequentially, so that the circuit cycles through the charging state, the boost transmission state and the charge redistribution state. By dynamically reconfiguring the network connection of the flying capacitor, the output voltage is continuously adjusted within a preset voltage conversion ratio range.

[0015] To achieve the above objectives, another aspect of the embodiments of this application proposes a chip including a battery charger based on a continuously variable capacitor converter as described above.

[0016] Compared with the prior art, the battery charger and control method provided in this application have the following significant advantages: 1) High efficiency and high output power: Through optimized network connection topology and timing control, the number of series switches in critical energy transmission paths is reduced from eight in existing technologies to five, significantly reducing path on-resistance. For example... Figure 7 As shown, under typical conditions of 12V input voltage and 4.2V output voltage, this application achieves a peak power conversion efficiency (PCE) of up to 92%, and the efficiency remains above 90% over a wide range of battery currents up to 3.3A, demonstrating its superior power handling capability and efficiency characteristics.

[0017] 2) Continuous conversion ratio capability and system simplification: This application can achieve continuous and efficient voltage regulation within a conversion ratio range of 0.25 to 0.5, and can directly adapt to the characteristics of the gradual voltage rise during battery charging, as well as different fast charging protocols (such as from 3.6V constant current charging to 4.2V constant voltage charging), thereby eliminating the need for the front-end voltage regulation circuit required by traditional switched capacitor solutions, simplifying the system structure and reducing costs.

[0018] 3) High power density: The all-capacitor architecture avoids bulky inductor components. At the same time, the topology has been optimized, using only four flying capacitors and seventeen switches. While achieving continuous transformation ratio, the number of components is effectively controlled, which is conducive to achieving high power density and miniaturized design.

[0019] 4) Elimination of invalid operating phases: The control strategy of this application ensures that the circuit is in an effective energy transfer or redistribution state in every switching phase, avoiding invalid phases present in the prior art, thereby improving the effective output power and overall performance of the converter. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of an inductive power converter in the prior art.

[0021] Figure 2 This is a schematic diagram of the structure of a switched capacitor power converter with a fixed conversion ratio of 2:1 in the prior art.

[0022] Figure 3 This is a schematic diagram of the structure of a continuous ratio capacitor power converter (bus connection) in the prior art.

[0023] Figure 4 This is an overall structural block diagram of a continuously variable ratio capacitor battery charger based on network connection topology provided in an embodiment of this application.

[0024] Figure 5 yes Figure 3 The diagram shown illustrates the equivalent path of the prior art in the energy transmission stage, demonstrating that the current needs to pass through eight series switches.

[0025] Figure 6 This is an equivalent path diagram of the energy transfer stage in an embodiment of this application, showing that the current only needs to pass through five series switches.

[0026] Figure 7 This is a measured curve of the power conversion efficiency (PCE) versus battery current (IBAT) in an embodiment of this application when the input voltage is 12V and the output voltages are 3.6V and 4.2V respectively. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit it. In the following description, when referring to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with those of this application; they are merely examples of apparatuses and methods consistent with some aspects of the embodiments of this application as detailed in the appended claims.

[0028] 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.

[0029] In battery charging applications, the choice of power converter topology directly affects charging efficiency and system performance. Currently, the most common structure is as follows: Figure 1 The inductive power converter shown achieves efficient and flexible voltage conversion and power regulation by controlling switching devices to regulate the energy storage and release of inductors, and is widely used in various charging scenarios. In recent years, switched-capacitor converters with a fixed 2:1 conversion ratio have also attracted increasing attention. They utilize the charge pump effect of capacitors for energy transfer, exhibiting low switching losses and fast transient response, making them particularly suitable for high-current fast charging requirements. Furthermore, to further improve power density, some research has introduced continuously variable converters into high-power-density designs; these converters can achieve higher efficiency within a certain range.

[0030] like Figure 1 The traditional inductive power converter shown is widely used, but it relies on large-size inductors when transmitting large currents, resulting in a large overall size and low power density, making it difficult to meet the needs of applications with strict size restrictions.

[0031] Figure 2 While the switched-capacitor converter with a fixed 2:1 conversion ratio shown can achieve efficient charging, its peak efficiency is heavily dependent on a specific input-output voltage ratio. Therefore, in practical applications, a pre-stage regulation circuit must be added to match the fast charging protocol to ensure the voltage is at the optimal conversion ratio. This undoubtedly increases the complexity and cost of the system, and the additional circuitry also diminishes its power density advantage.

[0032] And for Figure 3 The continuous-ratio converter shown [3] also presents significant technical challenges: First, it requires a large number of capacitors and switching elements to support continuous voltage regulation. Even if the number of flying capacitors is optimized to four, its inherent capacitor bus connection structure will significantly increase the impedance on the charging and discharging path, resulting in a reduction in maximum output power. In addition, there are a large number of invalid operating phases in this architecture, which do not participate in effective energy transfer, thereby significantly reducing the actual output power capability of the converter.

[0033] To address the technical problems existing in the prior art, this application proposes a continuously variable ratio capacitor-type battery charger based on network connection topology, the core architecture of which is as follows: Figure 4As shown. This design achieves a high degree of optimization in terms of the number of components, using only 4 flying capacitors, and each pair of capacitors is directly connected through only one switching element, so only 17 switches are needed to build a complete conversion network. This structure is much simpler than the traditional scheme [3]. Its core innovation lies in a special timing control strategy, which can dynamically reconstruct the network connection mode of the flying capacitors by precisely controlling the turn-on and turn-off sequence of these 17 switches, thereby achieving high-efficiency power conversion within a voltage conversion ratio of 0.25 to 0.5. Specifically, the core of its control strategy is: through a carefully arranged, periodic switching sequence, the 17 switches are driven to operate in an orderly manner, so that the network connection of the 4 flying capacitors is cyclically switched between several preset topology states. In each switching cycle, the circuit will enter different states in sequence, such as charging the capacitor, connecting the capacitor in series with the input source to increase the voltage, and redistributing the charge to maintain balance.

[0034] The solutions of the embodiments of this application will be described in detail below with reference to the accompanying drawings and specific application examples.

[0035] refer to Figure 4 The battery charger in this application embodiment includes an input port. Output ports (Connected battery), four flying capacitors and seventeen switches to The resulting switching network. The specific connection relationship of the switching network is an optimized "network connection topology," distinct from... Figure 3 and Figure 5 The diagram shows a "bus topology". In this topology, every two flying capacitors are directly connected through an independent switch, forming a highly interconnected network structure.

[0036] In one embodiment, the controller (which may be an MCU, FPGA, or dedicated driver chip) generates seventeen PWM control signals according to a predetermined timing control strategy to drive the switches. to .

[0037] The control strategy defines a recurring switching cycle T. Each cycle T is divided into multiple phases (e.g., 6 phases). The core states within a typical cycle are briefly described below: 1) Phase 1 (Charging State): Close the corresponding switch to transfer the input voltage. Applied to capacitor and Charge it.

[0038] 2) Phase 2 and Phase 3 (Boost Transmission State): By reconfiguring the network, for example, by converting the already charged... With input source Series connection, and simultaneously It is connected to the output in parallel in a specific manner. In this state, refer to... Figure 6 From input From capacitor network to output On the main energy transmission path, there are only switches , , , , Five switches are in series and conducting, and the path impedance is significantly lower than that of the circuit. Figure 5 The path shown is an eight-switch series connection.

[0039] 3) Phase 4 to Phase 6 (charge redistribution state): By operating the connection switch between the flying capacitors, charge flows between the capacitors in the network, balancing the voltage of each flying capacitor, and preparing for charging and transmission in the next cycle.

[0040] By precisely designing the switching combinations and durations of each phase, the controller can smoothly adjust the output voltage. Relative to input voltage The ratio varies continuously between 0.25 and 0.5.

[0041] In summary, Figure 5 and Figure 6 The bus-type connection in reference [3] and the network-type connection structure of this application are shown respectively. Through the analysis of the charging and discharging path, it can be seen that in the process of completing a complete power transfer from input to output, the bus-type structure in reference [3] requires the current to pass through the on-resistance generated by the series connection of up to 8 switching devices. In contrast, the network-type structure proposed in this application significantly reduces the number of series switches on the key energy transfer path to 5 through optimized topology connection. According to the theory explained in reference [3], the output power of the power converter is inversely proportional to the total on-resistance on the charging and discharging path. The smaller the path impedance, the greater the output power that can be achieved. In summary, since this application successfully reduces the core physical quantity behind the path impedance—the number of series switches—from 8 to 5, it can achieve a higher output power than the scheme in reference [3].

[0042] like Figure 7 As shown, Figure 7 To illustrate the performance of this application at input voltages of 12V and output voltages of 3.6V and 4.2V, the power conversion efficiency (PCE) versus battery current (IBAT) curves are presented. Test results show that at an output voltage of 4.2V, the converter achieves a peak power conversion efficiency of 92%, and its efficiency remains above 90% across a battery current range up to 3.3A.

[0043] The above description is merely a preferred embodiment of this application, but the scope of protection of this application is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope disclosed in this invention, based on the technical solution and inventive concept of this application, should be included within the scope of protection of this application.

Claims

1. A battery charger based on a continuously variable capacitor converter, characterized in that, include: The input port is used to connect an input voltage source; The output port is used to connect the battery to be charged. Four flying capacitors ( ); The switching network consists of seventeen switches ( to ), used to connect the four flying capacitors in a network connection topology, wherein every two flying capacitors are directly connected by a switch; The controller is configured to execute a predetermined timing control strategy, which dynamically reconfigures the network connection mode of the four flying capacitors by periodically controlling the on and off of the seventeen switches, so that the converter can achieve continuously adjustable voltage conversion within a preset voltage conversion ratio range and provide charging current for the battery.

2. The battery charger according to claim 1, characterized in that, One end of each flying capacitor is connected to the input port or the output port via at least one switch, and the other end is connected to the common ground or the output port via at least one switch.

3. The battery charger according to claim 1, characterized in that, The predetermined timing control strategy includes multiple repetitive switching cycles, each containing at least three different operating states, including: Charging status: Connect at least one flying capacitor to the input port for charging; Boost transmission mode: Connect at least one charged flying capacitor in series with the input source to boost the output voltage; Charge redistribution state: Charge transfer occurs between flying capacitors to maintain voltage balance by reconfiguring network connections.

4. The battery charger according to claim 3, characterized in that, The controller is configured to control the switching network in each switching cycle such that the number of switches connected in series on the main energy transmission path does not exceed five.

5. The battery charger according to claim 1, characterized in that, The battery charger has a peak power conversion efficiency of no less than 92% when the input voltage is 12V and the output voltage is 4.2V.

6. The battery charger according to claim 1, characterized in that, The battery charger is a switched capacitor type DC-DC converter, which does not require a pre-stage voltage regulation circuit and is directly compatible with various fast charging protocols.

7. The battery charger according to claim 1, characterized in that, The preset voltage conversion ratio range is 0.25 to 0.

5.

8. The battery charger according to claim 1, characterized in that, The controller is further configured to adjust the voltage conversion ratio in real time based on feedback signals from the output port voltage or battery charging current.

9. A method for controlling a battery charger according to any one of claims 1 to 8, characterized in that, Including the following steps: A switch network consisting of four flying capacitors and seventeen switches is provided, wherein every two flying capacitors are directly connected through a switch; The controller generates periodic switching control signals; According to the control signal, the connection state of the switching network is switched sequentially, so that the circuit cycles through the charging state, the boost transmission state and the charge redistribution state. By dynamically reconfiguring the network connection of the flying capacitor, the output voltage is continuously adjusted within a preset voltage conversion ratio range.

10. A chip, characterized in that, The battery charger includes the continuously variable capacitor converter based on any one of claims 1 to 8.

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