A wide-range LLC resonant converter topology and its control method

Abstract

The application provides a wide-range LLC resonant converter topology and a control method thereof. The converter topology designed by the application is mainly characterized by connecting a first inductor at an output end of a primary circuit, connecting a first capacitor and a second inductor in sequence at the first inductor, connecting an input end of the primary circuit at one end of the second inductor away from an electric energy conversion cavity, connecting an active inductor module in parallel with the first capacitor, and comprising two first switch tubes and second switch tubes connected in series opposition, and a third inductor connected in series with the second switch tube. The first switch tube and the second switch tube are respectively provided with a first switch tube and a second switch tube. The topology is a single-stage structure, and can be widely applied to occasions of wide-range voltage input, load size change, wide-range voltage output, and can realize soft switching technology.

Description

Technical Field

[0001] This invention belongs to the field of converter technology, and particularly relates to a wide-range LLC resonant converter topology and its control method. Background Technology

[0002] Large data centers, aerospace systems, new energy power generation, LED lighting, and electric vehicle charging are all placing increasingly higher demands on the capacity, efficiency, and power density of DC / DC converters. Developing high-efficiency, high-power-density, and high-reliability DC / DC converters is a necessity for industrial energy conservation and applications. Compared to other DC / DC converters, LLC resonant converters offer higher efficiency and higher power density, thus experiencing faster development and possessing broader application prospects.

[0003] However, LLC resonant converters struggle to maintain high reliability while achieving a wide input range. Furthermore, they clearly lack advantages when faced with varying loads and demands for a wide output range. Therefore, research into wide-input resonant converters has become particularly important.

[0004] The inventors discovered that among the existing technologies for implementing DC / DC converters with wide input / output ranges: Single-stage Buck-Boost circuits offer good efficiency and dynamic response, operating over a wide voltage input range; however, they lack isolation, suffer from high switching losses, and have low efficiency. Two-stage isolated topologies, with a non-isolated two-level / three-level Buck-Boost circuit in the front stage and an isolated LLC resonant circuit in the rear stage (the front stage regulates voltage, the rear stage provides isolation), offer high efficiency and are technically mature; however, the cost of multi-stage conversion circuits is high, and the circuit structure is complex. Cascaded LLC topologies suffer from reduced power density and efficiency due to the increased number of switching transistors and passive components. While combining PFM and PWM control strategies allows the resonant converter to operate over a wide input voltage range, frequency conversion control degrades the operating frequency characteristics of the LLC resonant converter at high frequencies, severely impacting the converter's conversion efficiency. Summary of the Invention

[0005] To address the aforementioned problems, this invention proposes a wide-range LLC resonant converter topology and its control method. The invention presents a novel single-stage LLC resonant converter topology that can be widely applied to applications with wide-range voltage input, varying load sizes, and wide-range voltage output. This topology also meets the requirements of soft-switching technology.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a wide-range LLC resonant converter topology, employing the following technical solution:

[0007] A wide-range LLC resonant converter topology includes a DC voltage source, a primary circuit, a power conversion cavity, a transformer, a secondary circuit, and a load connected in sequence.

[0008] The power conversion cavity includes a first inductor connected to the output terminal of the primary circuit, and a first capacitor and a second inductor connected in sequence to the first inductor. The end of the second inductor away from the power conversion cavity is connected to the input terminal of the primary circuit. An active inductor module is connected in parallel to the first capacitor. The active inductor module includes two first and second switching transistors connected in series and connected to each other, and a third inductor connected in series with the second switching transistor.

[0009] Furthermore, a second capacitor is connected in parallel with the DC voltage source.

[0010] Furthermore, the primary-side circuit includes a DC voltage source and a bridge arm circuit connected to the DC power source; the bridge arm circuit is a full-bridge circuit or a half-bridge circuit.

[0011] Furthermore, the end of the first inductor furthest from the first capacitor is connected between the third and fourth switching transistors; the end of the second inductor furthest from the first capacitor is connected between the fifth and sixth switching transistors.

[0012] Furthermore, a third capacitor is connected in parallel to the load.

[0013] Furthermore, the secondary circuit includes a load and a bridge arm circuit connected to the load; the bridge arm circuit is a full-bridge circuit or a half-bridge circuit.

[0014] Furthermore, one end of the transformer is connected between the seventh and eighth switching transistors, and the other end is connected between the ninth and tenth switching transistors.

[0015] Furthermore, the method by which the overall external capacitance value of the active inductor module is changed by controlling the phase shift angle is as follows: the difference between twice pi and twice the phase shift angle is then summed with the sine value of twice the phase shift angle to obtain the dividend. Four times the product of the cube of pi, the cube of the switching frequency, and the inductance value of the active inductor module is used as the divisor. The quotient is obtained based on the obtained dividend and divisor. The overall external capacitance value of the active inductor module is obtained by subtracting the quotient from the capacitance value of the first capacitor.

[0016] To achieve the above objectives, in a second aspect, the present invention also provides a wide-range LLC resonant converter topology control method, employing the following technical solution:

[0017] A wide-range LLC resonant converter topology control method, employing the wide-range LLC resonant converter topology as described in the first aspect, includes:

[0018] The first control strategy includes: sampling the voltage of the first capacitor and detecting the zero-crossing point of the voltage; converting the collected voltage data into a digital signal; performing signal delay, signal reset, and closed-loop regulation on the obtained digital signal; using the processed digital signal to control the first and second switching transistors in the active inductor module, and dynamically adjusting the output voltage by using phase shifting; keeping the switching signals of the third and sixth switching transistors synchronized, keeping the switching signals of the fourth and fifth switching transistors synchronized, and keeping the switching signals of the third and fourth switching transistors complementary; and keeping the switching frequencies of the first and second switching transistors the same as those of the third, fourth, fifth, and sixth switching transistors.

[0019] Furthermore, the output current of the primary circuit is sampled to detect the zero-crossing point of the current. At this time, the current delay is advanced by a quarter of a working or control cycle.

[0020] Furthermore, a second control strategy is adopted, in which the drive signals of the first, second, third, fourth, fifth, and sixth switching transistors are all given through a control algorithm, adding one degree of control freedom.

[0021] Furthermore, it includes at least a first switching mode, a second switching mode, a third switching mode, and a fourth switching mode;

[0022] The first switching mode is completed within the first preset time and the second preset time. The third and sixth switching transistors are turned on, and the current flows through the third switching transistor, the fourth switching transistor, the first inductor, the first capacitor, the second inductor, the transformer, the secondary circuit and the third capacitor, and finally supplies power to the load.

[0023] The second switching mode is completed within the second preset time and the third preset time. At the second preset time, the first switch is closed and the active inductor module starts to work. The current inside the active inductor module passes through the third inductor, the body diode in the second switch, and the first switch. The current first increases from zero and then begins to decrease. At the same time, the voltage across the third inductor undergoes a process of changing from negative to positive.

[0024] The third switching mode is completed within the third and fourth preset times. At the third preset time, the third and fourth switches are turned off simultaneously. The capacitors in the third and sixth switches are charged, while the capacitors in the fourth and fifth switches are discharged. The current freewheels through the body diodes of the third and fourth switches. At this time, the voltage across the fourth and fifth switches is zero. Continuing the operation of the previous mode, the voltage across the third inductor rises, and the current in the third inductor decreases in the reverse direction until it drops to zero, at which point the voltage across the third inductor disappears.

[0025] The fourth switching mode is completed within the fourth and fifth preset times, and the current is reversed; at the fourth preset time, the fourth and fifth switching transistors achieve zero-voltage conduction; the voltage across the third inductor remains zero, and the current in the third inductor is zero; at the fifth preset time, the first switching transistor achieves zero-current turn-off.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. This invention designs a novel single-stage LLC resonant converter topology. The main feature is the connection of a first inductor to the output of the primary circuit. The first inductor is sequentially connected to a first capacitor and a second inductor. The end of the second inductor furthest from the power conversion cavity is connected to the input of the primary circuit. An active inductor module is connected in parallel to the first capacitor. The active inductor module includes two series-connected, top-to-bottom switching transistors (first and second), and a third inductor connected in series with the second switching transistor. This topology is a single-stage structure and can be widely applied to applications with wide-range input voltage, varying load sizes, and wide-range output voltage. This topology also enables soft-switching technology.

[0028] 2. When the topology in this invention operates in the forward direction, it ensures the superiority of the LLC resonant circuit; when operating in the reverse direction, because of the addition of an active variable inductor, it is easier for it to operate in the inductive region, which creates convenient conditions for the implementation of reverse soft switching.

[0029] 3. This invention provides a method for calculating the external capacitance value generated by the parallel connection of the active variable inductor module and the first capacitor. The external capacitance of the active variable inductor module has a significant impact, and it is related to the values ​​of the switching frequency, inductance, and phase shift angle.

[0030] 4. This invention proposes two control strategies for a novel LLC resonant converter topology, with two implementation schemes for each strategy. Overall, the control strategy is relatively simple and can also eliminate the influence of factors such as device component parameters. Attached Figure Description

[0031] The accompanying drawings, which form part of this embodiment, are used to provide a further understanding of this embodiment. The illustrative embodiments and their descriptions are used to explain this embodiment and do not constitute an improper limitation of this embodiment.

[0032] Figure 1 This is a schematic diagram of the structure of Embodiment 1 of the present invention;

[0033] Figure 2 These are key waveforms of the AL-LLC resonant converter in Embodiment 1 of the present invention;

[0034] Figure 3 This is a schematic diagram of the operation of the topology in the first switching mode of Embodiment 1 of the present invention;

[0035] Figure 4 This is a schematic diagram of the operation of the topology in the second switching mode of Embodiment 1 of the present invention;

[0036] Figure 5 This is a schematic diagram of the operation of the first-stage topology in the third switching mode of Embodiment 1 of the present invention;

[0037] Figure 6 This is a schematic diagram of the second-stage topology structure under the third switching mode in Embodiment 1 of the present invention.

[0038] Figure 7 This is a schematic diagram of the operation of the topology in the fourth switching mode of Embodiment 1 of the present invention;

[0039] Figure 8 This is a schematic diagram of the structure corresponding to the first control strategy in Embodiment 1 of the present invention;

[0040] Figure 9 This is a schematic diagram of the structure corresponding to the second control strategy in Embodiment 1 of the present invention;

[0041] Figure 10 This is a schematic diagram of the AL parameter relationship in Embodiment 1 of the present invention;

[0042] Figure 11 This is a schematic diagram of the structure of Embodiment 2 of the present invention. Detailed implementation method:

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0044] It should be noted that the following detailed descriptions are exemplary and intended to provide further explanation of this application. Unless otherwise specified, 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 pertains.

[0045] Example 1:

[0046] like Figure 1 As shown, this embodiment provides a wide-range LLC resonant converter topology, including a DC voltage source V. dc Primary circuit, power conversion cavity, transformer, secondary circuit and load;

[0047] The DC voltage source V dc A second capacitor C is connected in parallel. IN The second capacitor C IN This is a voltage stabilizing filter capacitor; the primary-side circuit can be configured as a full-bridge circuit or a half-bridge circuit, consisting of four or two controllable switching transistors. When a full-bridge circuit is selected, it may include a third switching transistor T1, a fourth switching transistor T2, a fifth switching transistor T3, and a sixth switching transistor T4. The primary-side circuit includes a DC voltage source V. dc and the DC power supply V dc The connected bridge arm circuit is either a full-bridge circuit or a half-bridge circuit; the power conversion cavity includes capacitors, inductors, and controllable switches, specifically including an active inductor module AL (AL), a first inductor Lr, and a third inductor L... S First capacitor C, second inductor L m The second inductor L m The inductor is a magnetizing inductor; wherein, the active inductor module includes two series-connected top-to-bottom switching transistors and a third inductor L. S Series configuration; the two series-connected top-to-bottom switching transistors are the first switching transistor S. a Second switch S b The first switch S a and the second switch S b Both are controllable switches; the second inductor L m In practice, this can be provided by a transformer, and specific parameters can be obtained through transformer design; the transformer has a turns ratio of n:1; the secondary circuit can be set as a full-bridge circuit or a half-bridge circuit, consisting of four or two uncontrollable / controllable switching transistors, including the seventh switching transistor D1, the eighth switching transistor D2, the ninth switching transistor D3, and the tenth switching transistor D4; the load is a DC load, with a third capacitor C connected in parallel. O The third capacitor C O The capacitor is used for voltage regulation and filtering; the secondary circuit includes a load and a bridge arm circuit connected to the load, wherein the bridge arm circuit is a full-bridge circuit or a half-bridge circuit.

[0048] The key waveforms of the wide-range LLC resonant converter topology (AL-LLC resonant converter main circuit topology) in this embodiment are as follows: Figure 2 As shown, Figure 2 In the middle, v cd i represents the instantaneous output voltage of the bridge arm of the full bridge;Lr The instantaneous output current of the bridge arms of the full bridge from the third switch T1 to the fourth switch T4; T1 / T2 / T3 / T4 represent the drive signals of their corresponding switches; v C This is the instantaneous voltage across the first capacitor C, or it can be expressed as v. ab Indicates; S a / S b This represents the drive signal for the switching transistor in the AL structure; v Ls i is the instantaneous voltage across the third inductor Ls; Ls To pass through the third inductor L S The instantaneous current; α is the phase shift angle of the controllable switch drive signal of the active variable inductor module AL, which serves as the control signal and capacitor voltage v. C Phase difference at the zero point.

[0049] The novel topology AL-LLC resonant converter has eight switching modes within one conversion cycle. Before modal analysis, to simplify the analysis, the following basic assumptions are made: the third inductor L... S The first inductor Lr, the first capacitor C, and the load RL are all ideal devices, and their additional losses are negligible; all switching transistors are ideal devices, and the parasitic capacitance C of the switching transistors is negligible. T The capacitance value remains consistent; for ease of analysis, the bridge arm output current i ab It approximates an alternating sine wave.

[0050] like Figure 3 As shown, the first switching mode corresponds to the time [t0-t1], which are the first preset time t0 and the second preset time t1, respectively; at the first preset time t0, the third switch T1 and the fourth switch T4 are turned on, and the bridge arm current i flowing from c to d Lr The circuit passes through the third switch T1, the fourth switch T4, the first inductor Lr, the first capacitor C, and the second inductor L. m Transformer, secondary circuit, and the third capacitor C O Finally, power is supplied to the load RL; the first inductor Lr stores energy during this stage, while the bridge arm current increases, and the active variable inductor module AL.

[0051] like Figure 4 As shown, the second switching mode corresponds to the time [t1-t2], which are the second preset time t1 and the third preset time t2, respectively. The bridge arm current i in this mode is... Lr Maintain the flow from c to d; at the second preset time t1, the first switch S a When the switch is closed, the AL starts working, and the internal current i of the AL... Ls The current flows from b to a, that is, through the third inductor L. S The second switching transistor S bbody diode D Sb The first switching transistor S a During this process, i Ls It will first increase from zero to a certain value, and then begin to decrease, while the third inductor L... S The voltage at both ends also undergoes a process of changing from negative to positive.

[0052] like Figure 5 and Figure 6 As shown, the third switching mode corresponds to the time [t2-t3], which are the third preset time t2 and the fourth preset time t3, respectively. This process will last for two stages. At the third preset time t2, the third switch T1 and the fourth switch T4 are turned off simultaneously. To prevent voltage source shoot-through, the third switch T1, the fourth switch T2, the fifth switch T3, and the sixth switch T4 are all equipped with a short dead time to maintain the current i. Lr The current flows from c to d, and freewheeling occurs through the parasitic capacitance of the controllable switch, wherein the capacitor C in the third switch T1... T1 and the capacitor C in the sixth switch T4 T4 During charging, the capacitor C in the fourth switch T2 T2 and the capacitor C in the fifth switch T3 T3 Discharge occurs; after the parasitic capacitance of the controllable switch has released its charge, the current i Lr The body diode D of the fourth switch T2 and the fifth switch T3 will continue to pass through. T2 and D T3 During freewheeling, the voltage across the fourth switch T2 and the fifth switch T3 is zero, laying the foundation for the implementation of zero-voltage switching (ZVS) technology for the two controllable switches in the next mode. The active inductor module AL continues the operation of the previous mode, and the voltage v across the third inductor... Ls The current i in the third inductor rises. Ls Reverse descent, until i in the third inductor Ls After the voltage drops to zero, the voltage v across the third inductor... Ls Disappearance; the current i in the third inductor Ls It will remain at zero; this state is the first switching transistor S in the next mode. a This laid the foundation for realizing Zero Current Switching (ZCS) technology.

[0053] like Figure 7 As shown, the fourth switching mode corresponds to the time [t3-t4], which are the fourth preset time t3 and the fifth preset time t4, respectively; during this process, the bridge arm current i LrThis will achieve commutation; at the fourth preset time t3, the fourth switch T2 and the fifth switch T3 will achieve ZVS conduction; the voltage v across the third inductor in the active variable inductor module AL will be... Ls The current i in the third inductor remains zero. Ls The value is zero; at the fifth preset time t4, the first switch S... a Implement ZCS shutdown.

[0054] The remaining working modes are similar to those in the first half of the transformation cycle, and will not be repeated here.

[0055] In this implementation, two control strategy methods are provided, wherein the first control strategy is one-dimensional control and the second control strategy is two-dimensional control;

[0056] In this embodiment, as Figure 8 As shown, in Scheme 1, the first capacitor C in SCL is sampled by a high-precision voltage sensor for zero-crossing detection; the output voltage can be accurately quantized using methods such as resistor voltage divider and voltage sensor; the collected data is converted from analog to digital signals by an analog-to-digital converter module such as ADC, and then the obtained digital signals are subjected to a series of control algorithm operations, including signal delay, signal reset, closed-loop regulation, etc., and finally used to control the first switching transistor S in AL. a Second switch S b The output voltage is dynamically adjusted using phase shifting; the first switch S of AL participates in the closed-loop control. a Second switch S b The controllable switches in the full-bridge circuit monitor soft-start, overvoltage, and overcurrent conditions. The switching signals of the third switch T1 and the sixth switch T4 are synchronized, as are the switching signals of the third switch T2 and the fourth switch T3. The switching signals of the third switch T1 and the fourth switch T2 are complementary. The controllable switches in the full-bridge circuit do not participate in closed-loop control. The first switch S of AL... a Second switch S b The switching frequencies of the controllable switching transistors T1, T2, T3, and T4 of the full-bridge circuit are the same.

[0057] The main difference between Option 2 and Option 1 lies in the sampling location and devices for AL; everything else remains the same. Option 2 uses different sampling methods for the bridge arm current i. Lr Sampling is performed using a high-precision voltage sensor to detect the zero-crossing point of the current. The signal delay settings for the two schemes are different in the control module. The voltage delay of Scheme 1 is later than the current delay of Scheme 2 by a quarter of a working or control cycle.

[0058] Similarly, such as Figure 9 As shown, the main difference between the two-dimensional control scheme and Scheme 2 lies in the sampling location and devices for AL; everything else remains the same. Scheme 1 samples the first capacitor C of AL using a high-precision voltage sensor for zero-crossing detection; Scheme 2 samples the bridge arm current i... Lr Sampling is performed using a high-precision voltage sensor to detect the zero-crossing point of the current. The signal delay settings for the two schemes are different in the control module. The voltage delay of Scheme 1 is later than the current delay of Scheme 2 by a quarter of a working or control cycle.

[0059] The main difference between two-dimensional control and one-dimensional control lies in the drive signals of the controllable switching transistors T1, T2, T3, and T4 in the full-bridge circuit, as well as the switching transistor S of A1. a and S b The drive signals are all given through the control algorithm, which increases the control degree of freedom by one. This means that the third switch T1, the fourth switch T2, the fifth switch T3, and the sixth switch T4 also participate in the closed-loop control. The full-bridge circuit and AL simultaneously perform phase shifting to adjust the output voltage. The phase shift angle β of the full-bridge circuit is the leading angle of the drive signal of the third switch T1 compared to the drive signal of the fifth switch T3. The controllable switch S of AL... a / S b The switching frequencies of the controllable switching transistors T1, T2, T3, and T4 of the full-bridge circuit are the same.

[0060] like Figure 10 As shown, the active variable inductor AL is used to control the first switch S. a Second switch S b For the third inductor L S Charging and discharging control enables the inductor to participate in or exit the circuit operation, thereby changing the external inductance value of the structure. When it is connected in parallel with the first capacitor C, AL can change the overall external capacitance value Cr by controlling the phase shift angle α. The derivation formula for its external capacitance value Cr is as follows:

[0061]

[0062] Where α is the phase shift angle of the AL controllable switch, with a value ranging from [π / 2, π]; f is the switching frequency; L S α is the inductance value; C is the capacitance value. As α increases, the external capacitance Cr continuously increases.

[0063] 1. The topology in this embodiment has only one stage, which is simple. Compared with the original two-stage topology, this new topology uses fewer components and has lower production costs. It can also utilize magnetic integration technology to optimize inductor / transformer design, greatly improving power density and reducing size. This topology can be widely used in applications with wide-range input voltage, varying load sizes, and wide-range output voltage. It also enables soft-switching technology.

[0064] 2. In this embodiment, the topology ensures the superiority of the LLC resonant circuit when operating in the forward direction; when operating in the reverse direction, the addition of an active variable inductor AL makes it easier to operate in the inductive region, creating convenient conditions for the implementation of reverse soft switching.

[0065] 3. In this embodiment, a method for implementing soft-switching technology in this topology is proposed. All six switches in this topology can implement soft-switching technology, which greatly reduces switching losses and can also further increase the switching frequency and improve the conversion efficiency.

[0066] 4. This embodiment proposes two control strategies for a novel LLC resonant converter topology based on active variable inductance, with two implementation schemes for each strategy. Overall, the control strategy is relatively simple and can also eliminate the influence of factors such as device component parameters.

[0067] 5. This embodiment provides a formula for calculating the external capacitance Cr generated by the parallel structure of the active variable inductor AL and capacitor C. AL has a significant impact on Cr, and its effect is related to the switching frequency and inductance L. S It is related to the value of the phase shift angle α.

[0068] Example 2:

[0069] like Figure 11 As shown, the main difference between this embodiment and Embodiment 1 lies in the full-bridge circuit in the fifth part, both of which are composed of controllable switching transistors Q1, Q2, Q3, and Q4; the sixth part includes a DC voltage source, a voltage regulator, and a filter capacitor C. O .

[0070] Example 3:

[0071] This embodiment provides a wide-range LLC resonant converter topology control method, which adopts the wide-range LLC resonant converter topology as described in Embodiment 1, including:

[0072] The first control strategy includes: sampling the voltage of the first capacitor and detecting the zero-crossing point of the voltage; converting the collected voltage data into a digital signal; performing signal delay, signal reset, and closed-loop regulation on the obtained digital signal; using the processed digital signal to control the first and second switching transistors in the active inductor module, and dynamically adjusting the output voltage by using phase shifting; keeping the switching signals of the third and sixth switching transistors synchronized, keeping the switching signals of the fourth and fifth switching transistors synchronized, and keeping the switching signals of the third and fourth switching transistors complementary; and keeping the switching frequencies of the first and second switching transistors the same as those of the third, fourth, fifth, and sixth switching transistors.

[0073] In this embodiment, the output current of the primary circuit is sampled and the zero-crossing point of the current is detected. At this time, the current delay is advanced by one-quarter of the working or control cycles.

[0074] In this embodiment, a second control strategy is adopted, which includes: the drive signals of the first, second, third, fourth, fifth, and sixth switching transistors are all given through a control algorithm, thereby increasing the control degree of freedom.

[0075] In this embodiment, at least a first switching mode, a second switching mode, a third switching mode, and a fourth switching mode are included;

[0076] The first switching mode is completed within the first preset time and the second preset time. The third and sixth switching transistors are turned on, and the current flows through the third switching transistor, the fourth switching transistor, the first inductor, the first capacitor, the second inductor, the transformer, the secondary circuit and the third capacitor, and finally supplies power to the load.

[0077] The second switching mode is completed within the second preset time and the third preset time. At the second preset time, the first switch is closed and the active inductor module starts to work. The current inside the active inductor module passes through the third inductor, the body diode in the second switch, and the first switch. The current first increases from zero and then begins to decrease. At the same time, the voltage across the third inductor undergoes a process of changing from negative to positive.

[0078] The third switching mode is completed within the third and fourth preset times. At the third preset time, the third and fourth switches are turned off simultaneously. The capacitors in the third and sixth switches are charged, while the capacitors in the fourth and fifth switches are discharged. The current freewheels through the body diodes of the third and fourth switches. At this time, the voltage across the fourth and fifth switches is zero. Continuing the operation of the previous mode, the voltage across the third inductor rises, and the current in the third inductor decreases in the reverse direction until it drops to zero, at which point the voltage across the third inductor disappears.

[0079] The fourth switching mode is completed within the fourth and fifth preset times, and the current is reversed; at the fourth preset time, the fourth and fifth switching transistors achieve zero-voltage conduction; the voltage across the third inductor remains zero, and the current in the third inductor is zero; at the fifth preset time, the first switching transistor achieves zero-current turn-off.

[0080] The above description is merely a preferred embodiment of this practice and is not intended to limit the scope of this practice. Various modifications and variations can be made to this practice by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this practice should be included within the protection scope of this practice.

Claims

1. A wide-range LLC resonant converter topology, characterized in that, It includes a DC voltage source, primary circuit, power conversion cavity, transformer, secondary circuit and load connected in sequence; The power conversion cavity includes a first inductor connected to the output terminal of the primary circuit, and a first capacitor and a second inductor connected in sequence to the first inductor. The end of the second inductor away from the power conversion cavity is connected to the input terminal of the primary circuit. An active inductor module is connected in parallel to the first capacitor. The active inductor module includes two first and second switching transistors connected in series and connected to each other, and a third inductor connected in series with the second switching transistor. The active inductor module changes its overall external capacitance value by controlling the phase shift angle as follows: The difference between twice the value of pi and twice the phase shift angle is summed with the sine of twice the phase shift angle to obtain the dividend. Four times the product of the cube of pi, the cube of the switching frequency, and the inductance value of the active inductor module is used as the divisor. The quotient is obtained based on the dividend and divisor. The overall external capacitance value of the active inductor module is obtained by subtracting the quotient from the capacitance value of the first capacitor.

2. The wide-range LLC resonant converter topology as described in claim 1, characterized in that, A second capacitor is connected in parallel with the DC voltage source.

3. The wide-range LLC resonant converter topology as described in claim 1, characterized in that, The primary circuit includes a DC voltage source and a bridge arm circuit connected to the DC voltage source; the bridge arm circuit is a full-bridge circuit or a half-bridge circuit.

4. The wide-range LLC resonant converter topology as described in claim 3, characterized in that, The end of the first inductor furthest from the first capacitor is connected between the third and fourth switching transistors; the end of the second inductor furthest from the first capacitor is connected between the fifth and sixth switching transistors.

5. The wide-range LLC resonant converter topology as described in claim 1, characterized in that, A third capacitor is connected in parallel to the load.

6. The wide-range LLC resonant converter topology as described in claim 1, characterized in that, The secondary circuit includes a load and a bridge arm circuit connected to the load; the bridge arm circuit is a full-bridge circuit or a half-bridge circuit.

7. A wide-range LLC resonant converter topology as described in claim 6, characterized in that, One end of the transformer is connected between the seventh and eighth switching transistors, and the other end is connected between the ninth and tenth switching transistors.

8. A topology control method for a wide-range LLC resonant converter, characterized in that, The wide-range LLC resonant converter topology described in any one of claims 1-7 is adopted, comprising: The first control strategy includes: sampling the voltage of the first capacitor and detecting the zero-crossing point of the voltage; converting the collected voltage data into a digital signal; performing signal delay, signal reset, and closed-loop regulation on the obtained digital signal; using the processed digital signal to control the first and second switching transistors in the active inductor module, and dynamically adjusting the output voltage by using phase shifting; keeping the switching signals of the third and sixth switching transistors synchronized, keeping the switching signals of the fourth and fifth switching transistors synchronized, and keeping the switching signals of the third and fourth switching transistors complementary; and keeping the switching frequencies of the first and second switching transistors the same as those of the third, fourth, fifth, and sixth switching transistors. Alternatively, the output current of the primary circuit can be sampled to detect the zero-crossing point of the current. The signal delay settings for the two types of signals are different in the control module, while other settings remain the same. In this case, the current delay is advanced by a quarter of the working or control cycle. Alternatively, a second control strategy can be adopted, including: the drive signals of the first, second, third, fourth, fifth, and sixth switching transistors are all given through a control algorithm, adding one degree of control freedom; the third, fourth, fifth, and sixth switching transistors also participate in closed-loop control, and the full-bridge circuit and AL simultaneously perform phase shifting to adjust the output voltage, with the phase shift angle of the full-bridge circuit being the leading angle of the third switching transistor's drive signal compared to the fifth switching transistor's drive signal; the controllable switching transistors Sa / Sb of AL and the controllable switching transistors T4 of the full-bridge circuit, namely the third, fourth, fifth, and sixth switching transistors, have the same switching frequency.

9. The wide-range LLC resonant converter topology control method as described in claim 8, characterized in that, It includes at least a first switching mode, a second switching mode, a third switching mode, and a fourth switching mode; The first switching mode is completed within the first preset time and the second preset time. The third and sixth switching transistors are turned on, and the current flows through the third switching transistor, the fourth switching transistor, the first inductor, the first capacitor, the second inductor, the transformer, the secondary circuit and the third capacitor, and finally supplies power to the load. The second switching mode is completed within the second preset time and the third preset time. At the second preset time, the first switch is closed and the active inductor module starts to work. The current inside the active inductor module passes through the third inductor, the body diode in the second switch, and the first switch. The current first increases from zero and then begins to decrease. At the same time, the voltage across the third inductor undergoes a process of changing from negative to positive. The third switching mode is completed within the third and fourth preset times. At the third preset time, the third and fourth switches are turned off simultaneously. The capacitors in the third and sixth switches are charged, while the capacitors in the fourth and fifth switches are discharged. The current freewheels through the body diodes of the third and fourth switches. At this time, the voltage across the fourth and fifth switches is zero. Continuing the operation of the previous mode, the voltage across the third inductor rises, and the current in the third inductor decreases in the reverse direction until it drops to zero, at which point the voltage across the third inductor disappears. The fourth switching mode is completed within the fourth and fifth preset times, and the current is reversed; at the fourth preset time, the fourth and fifth switching transistors achieve zero-voltage conduction; the voltage across the third inductor remains zero, and the current in the third inductor is zero; at the fifth preset time, the first switching transistor achieves zero-current turn-off.

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