LLC resonant converter charging device

Abstract

The utility model provides an LLC resonant converter charging device which is composed of a pre-stage Boost PFC circuit and a post-stage full-bridge LLC resonant converter circuit, and the pre-stage Boost PFC circuit comprises an LT4320 ideal diode bridge controller and a UCC28019 controller which are connected with each other. The Boost PFC circuit utilizes an LT4320 ideal diode bridge and a UCC28019 controller, so that the rectification loss is effectively reduced, and the overall energy efficiency of the system is improved. The four N-channel MOSFETs are driven by adopting the LT4320 ideal diode bridge controller, so that the voltage utilization rate is improved and the energy consumption is reduced in the voltage rectification process from direct current to 600Hz, and the low-voltage LED driving circuit is particularly suitable for low-voltage application.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of power electronics, switching power supply, LLC resonant converter and the like, and particularly relates to a LLC resonant converter charging device. BACKGROUND

[0002] In the prior art, LLC resonant converters have been widely used in high-efficiency power conversion. Their working principle effectively reduces switching loss and improves system efficiency through zero-voltage switching (ZVS) and zero-current switching (ZCS) technologies. Patent CN202411398185 (A Method for Protecting a Charging Module Based on LLC Resonant Frequency and Storage Medium) proposes a method for protecting a charging module based on LLC resonant frequency, which uses frequency regulation and voltage control to optimize output voltage and protect the circuit from overvoltage, overcurrent, and other problems. However, this solution has obvious limitations under light load conditions. Since the frequency regulation mechanism cannot be fully adjusted under low load, the output voltage range of the charging module is limited, making it impossible to provide stable voltage and resulting in low efficiency. This solution lacks a dynamic frequency regulation mechanism, resulting in excessive switching frequency under low load, which increases energy loss and reduces overall system efficiency.

[0003] In addition, the adaptability and protection mechanism of the prior art also has shortcomings when facing complex working conditions. Although this solution provides basic overvoltage and overcurrent protection, it cannot handle dynamic changes under different load conditions in actual applications (such as electric vehicle charging or LED lighting scenarios), resulting in poor flexibility and adaptability of the system. If the output voltage range cannot be effectively expanded, the adaptability of the charging device will be limited, especially in applications that require a wide voltage regulation range (such as electric vehicle charging, LED driving, etc.). Under light load conditions, the frequency regulation mechanism fails to function fully, resulting in excessively high switching frequency and causing additional switching loss and energy waste, further affecting efficiency and system stability.

[0004] To address the above problems, some existing solutions propose a one-way Boost PFC + full-bridge LLC resonant converter design, but it still has problems such as low overall system efficiency, high power consumption, and insufficient stability. SUMMARY

[0005] In view of the defects and deficiencies existing in the prior art, the utility model discloses a combination of boost PFC circuit and the later stage full -bridge LLC resonant converter on the basis of using boost PFC circuit with LT4320 ideal diode bridge and UCC28019 controller constitutes to effectively reduce rectification loss, improve the overall energy efficiency of system.

[0006] It specifically adopts the following technical solutions:

[0007] An LLC resonant converter charging device is composed of a front-stage boost PFC circuit and a rear-stage full-bridge LLC resonant converter circuit: the front-stage boost PFC circuit includes a connected LT4320 ideal diode bridge controller and a UCC28019 controller.

[0008] Further, the front-stage boost PFC circuit is connected with an EMI suppression circuit, which includes a 2mH common-mode inductor, a 470nF differential-mode capacitor as an X capacitor and a 2.2nF common-mode capacitor as a Y capacitor connected in parallel; the Y capacitor is connected with a MOSFET of a main power circuit.

[0009] Further, the front-stage boost PFC circuit uses a 470nF CBB capacitor as an input capacitor, a 330μH inductor as a chopping inductor and a BSC070N10NS as a switching tube; in the peripheral circuit of the UCC28019 controller, a 600kΩ feedback resistor is used, a 220Ω resistor is connected in series with the No. 3 pin and a 1nF capacitor is connected in parallel with the No. 3 pin.

[0010] Further, the primary side of the full-bridge LLC resonant converter circuit is connected in series with seven 220nF / 50V film capacitors connected in parallel; the secondary side is connected in series with two fast recovery diodes.

[0011] Further, the driving circuit of the full-bridge LLC resonant converter circuit uses a 5kV isolation driving IC, and the primary side driving circuit includes an RC filter.

[0012] Further, the sampling circuit of the full-bridge LLC resonant converter circuit is an operational amplifier differential sampling circuit, the voltage sampling part includes an RC filter, the current sampling part includes a C filter, and the DSP sampling port is connected with a secondary RC filter.

[0013] Compared to existing technologies, this invention and its preferred solution significantly reduce the rectified voltage drop (from approximately 1V to 30-40mV in actual tests) by using an LT4320 ideal diode bridge controller and N-channel MOSFETs instead of a traditional rectifier bridge design, thereby improving system efficiency and reducing power consumption. Furthermore, the selection of low-resistance MOSFETs reduces heat generation and optimizes the heat dissipation design. In addition, by dynamically adjusting the rectifier control, the system can adapt to a wider range of input voltage and load variations, outperforming existing solutions in terms of power efficiency and adaptability. Further hardware optimization significantly improves the system's performance in power conversion efficiency, electromagnetic compatibility, and dynamic adjustment capabilities, further enhancing the system's practicality and reliability.

[0014] In addition, to enhance the system's stability and anti-interference capability in high-frequency operating environments, multi-level EMI suppression measures are adopted in the optimized design, including common-mode inductors, differential-mode capacitors, and varistors, which can effectively suppress conducted and radiated interference. Attached Figure Description

[0015] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0016] Figure 1 This is a block diagram of the overall hardware system of this utility model embodiment;

[0017] Figure 2 This is an EMI circuit diagram of an embodiment of the present invention;

[0018] Figure 3 This is a circuit diagram of the Boost PFC according to an embodiment of the present invention;

[0019] Figure 4 This is a peripheral circuit diagram of the UCC28019 embodiment of the present invention;

[0020] Figure 5 This is a schematic diagram of the LLC main topology circuit of an embodiment of this utility model;

[0021] Figure 6 This is a driving circuit diagram of an embodiment of the present utility model;

[0022] Figure 7 This is a sampling circuit diagram of an embodiment of the present invention. Detailed Implementation

[0023] To make the features and advantages of this utility model more apparent and understandable, specific embodiments are described below in conjunction with the accompanying drawings:

[0024] The power supply system provided in this embodiment consists of a front-end Boost PFC circuit and a rear-end full-bridge LLC resonant converter circuit, aiming to optimize power conversion efficiency and improve system stability. The system hardware framework is as follows: Figure 1 As shown. The front-end Boost PFC circuit uses an Analog Devices LT4320 ideal diode bridge controller combined with a Texas Instruments (TI) UCC28019 PFC controller. By operating in continuous conduction mode (CCM), it effectively achieves power factor correction (PFC), improving the overall system efficiency. The rear-end section consists of a full-bridge LLC circuit, including primary-side MOSFETs, current / voltage sampling modules, LLC resonant networks, output rectifier and filter circuits, signal acquisition and drive controllers, and auxiliary power supplies (12V and 5V). The rectifier circuit of the rear-end LLC resonant converter consists of four Schottky rectifiers STPS15L60C. Through the coordinated operation of these modules, a highly efficient and stable power output is achieved. The main circuit design of the rear-end full-bridge LLC circuit is existing technology.

[0025] For the front-end Boost PFC circuit, to ensure the stability and reliability of the system under high-frequency operation, this embodiment pays special attention to the design of electromagnetic interference (EMI) suppression and protection circuits. For example... Figure 2 As shown, the EMI suppression circuit employs a 2mH common-mode inductor, a 470nF differential-mode capacitor (X capacitor), and a 2.2nF common-mode capacitor (Y capacitor), effectively suppressing conducted interference and radiation issues. To further improve the system's anti-interference capability, the MOSFET is connected to the Y capacitor to further reduce common-mode interference. Furthermore, this embodiment also uses a varistor to absorb transient interference in the circuit and a 5A fuse for overload protection.

[0026] In this embodiment, by employing the LT4320 ideal diode bridge controller to drive four N-channel MOSFETs, voltage utilization is improved and energy consumption is reduced during DC to 600Hz voltage rectification, making it particularly suitable for low-voltage applications. Simultaneously, the LT4320's fast turn-off function enhances circuit stability.

[0027] Boost PFC circuit, such as Figure 3 and Figure 4As shown, in the design of the Boost PFC circuit, a 470nF CBB capacitor is selected as the input capacitor to ensure the filtering of high-frequency components. Based on the calculation in Formula 1.1, the capacitor value required for power factor correction in the PFC circuit is reasonably selected. The input voltage range is 20V to 36V. After calculation, the minimum value of the chopper inductor is determined to be 256μH. In this embodiment, a 330μH inductor is actually selected. For specific calculations, refer to Formula 1.2. The switching transistor is a BSC070N10NS, which has a low internal resistance, reducing switching losses and thus improving circuit efficiency. The UCC28019 chip provides the drive signal for the PFC circuit. In its peripheral circuit, a 220Ω resistor is connected in series with pin 3 and a 1nF capacitor is connected in parallel to enhance anti-interference capability. A 600kΩ feedback resistor ensures the accuracy of the feedback voltage. The sliding rheostat is connected to pin FB (pin 6) of the UCC28019 for voltage feedback.

[0028]

[0029]

[0030] From a functional perspective, the full-bridge LLC resonant converter circuit consists of three parts: the main power circuit, the drive circuit, and the sampling circuit. The main power circuit uses a four-MOSFET half-bridge configuration to provide efficient power conversion. To optimize resonant performance and reduce losses, this embodiment uses seven 220nF / 50V film capacitors instead of traditional ceramic capacitors. The higher capacitance of the film capacitors effectively disperses current, reduces heat loss, and thus improves system efficiency and reliability. Two fast recovery diodes are used in the secondary-side rectification section to ensure thermal performance and rectification efficiency. Figure 5 The diagram shown is the schematic of the main power circuit, illustrating the configuration of each component.

[0031] For the drive circuit, a 5kV isolated driver IC (SI8233BD) is used to drive the high-order and low-order MOSFETs, simplifying the circuit design and reducing the number of components. The primary-side drive circuit uses an RC filter to suppress high-frequency noise, ensuring the stability of the drive signal. The schematic diagram of the drive circuit is shown below. Figure 6 As shown, the paths of each driving signal are illustrated.

[0032] In the sampling circuit design, to address potential interference signals from high-frequency switching, an operational amplifier differential sampling method was employed to accurately sample voltage and current, ensuring stable system operation. Voltage sampling uses an RC filter to remove high-frequency voltage components, while current sampling uses a C filter to remove high-frequency current signals. Adding a secondary RC filter to the DSP sampling port effectively improved sampling accuracy and eliminated noise signals. The schematic diagram of the sampling circuit is shown below.Figure 7 As shown, the configuration and function of each filter are illustrated.

[0033] When selecting power devices, the peak current of the MOSFET is calculated to be 7.8A based on the minimum input voltage and full-load conditions. A BSC050N04LS diode (with a withstand voltage ≥40V and low internal resistance) is selected with a margin of 2 times and 1.3 times the peak current. A 10kΩ resistor is connected in parallel between the gate and source to prevent static mis-conduction. The secondary-side rectification uses a center-tapped full-wave rectification method. Based on the output voltage and current, the maximum current of a single diode is calculated, and an MBRD10100CT fast recovery diode (rated current 13A, withstand voltage 100V) is selected with a margin of 2-3 times to meet the requirements of high-frequency operation and short-circuit inrush current.

[0034] In the design of the resonant element, the resonant frequency is set to 50kHz, the input and output voltages are both 24V, the output current is 4A, and the rectified voltage drop is assumed to be 1.5V. The primary-to-secondary ratio of the transformer is calculated using formula 1.3, and the H value and gain coefficient are defined using empirical formula 1.4. Different gain curves are plotted to analyze load changes. The transformer uses a PQ3230 magnetic core with a maximum magnetic flux density of 150mT and a turns ratio of 5. The coil is wound with 0.1mm enameled wire, with 150 strands on the primary side and 50 strands on the secondary side. The resonant inductor uses a PQ2020 magnetic core made of PC40 material, with a calculated number of 7 turns.

[0035]

[0036]

[0037] The filtering section uses aluminum electrolytic capacitors. Under full load of 4A, the target ripple value is 120mV. The total capacitance needs to be greater than 1mF. Finally, three 35V, 470μF capacitors are connected in parallel to effectively smooth the output voltage.

[0038] This utility model is not limited to the above-described preferred embodiment. Anyone can derive other forms of LLC resonant converter charging devices under the guidance of this utility model. All equivalent changes and modifications made within the scope of the claims of this utility model shall fall within the scope of this utility model.

Claims

1. A LLC resonant converter charging device, consisting of a front-stage Boost PFC circuit and a rear-stage full-bridge LLC resonant converter circuit, characterized in that: The front-stage Boost PFC circuit comprises a LT4320 ideal diode bridge controller and a UCC28019 controller connected in series; four N-channel MOSFETs are driven by the LT4320 ideal diode bridge controller to replace the traditional rectifier bridge design.

2. The LLC resonant converter charging apparatus of claim 1, wherein: The front-stage Boost PFC circuit is connected with an EMI suppression circuit, which comprises 2mH common-mode inductors connected in parallel, 470nF differential-mode capacitors as X capacitors and 2.2nF common-mode capacitors as Y capacitors; the Y capacitors are connected with MOSFETs of the main power circuit.

3. The LLC resonant converter charging apparatus of claim 1, wherein: The front-stage Boost PFC circuit adopts 470nF CBB capacitors as input capacitors, 330μH inductors as chopping inductors and BSC070N10NS as switching tubes; in the peripheral circuit of the UCC28019 controller, 600kΩ feedback resistors are adopted, a 220Ω resistor is connected in series with the No.3 pin and a 1nF capacitor is connected in parallel with the No.3 pin.

4. The LLC resonant converter charging apparatus of claim 1, wherein: Seven 220nF / 50V film capacitors connected in parallel are connected in series with the primary side of the full-bridge LLC resonant converter circuit; two fast recovery diodes are connected in series with the secondary side.

5. The LLC resonant converter charging apparatus of claim 1, wherein: The driving circuit of the full-bridge LLC resonant converter circuit adopts a 5kV isolation driving IC, and the primary side driving circuit comprises an RC filter.

6. The LLC resonant converter charging apparatus of claim 1, wherein: The sampling circuit of the full-bridge LLC resonant converter circuit is an operational amplifier differential sampling circuit, the voltage sampling part comprises an RC filter, the current sampling part comprises a C filter, and a secondary RC filter is connected with the DSP sampling port.

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