Topology of passive resonant converter based on optimized parameter calculation and control method thereof

Abstract

The application provides a topology of a passive resonant converter based on optimization parameter calculation and a control method thereof, and the resonant conversion cavity comprises a second inductor, a first capacitor, a third inductor and a first inductor which are sequentially connected in series at two ends of a first bridge arm circuit; the second inductor is connected in parallel with a second capacitor; in a process of solving a voltage gain, when an inductance ratio and a quality factor are calculated, a resonant inductance is represented by a ratio of an inductance of the first inductor and a resonant inductance coupling coefficient introduced, and the resonant inductance coupling coefficient is equal to a quotient of the inductance of the first inductor divided by a sum of the inductance of the first inductor and an inductance of the second inductor; the application adds two resonant devices on the basis of a classical LLC resonance, and achieves the purpose of being widely applied to occasions of wide-range voltage input, light load, heavy load and wide-range voltage output; meanwhile, for the improved topology, the analysis method can avoid the factors of multiple resonant devices, is convenient to understand, and can quickly obtain the parameter values.

Description

Technical Field

[0001] This invention belongs to the field of passive resonant converter technology, and particularly relates to a topology of a passive resonant converter based on optimized parameter calculation and its control method. Background Technology

[0002] Currently, for DC / DC converters capable of wide-range input and output, a two-stage isolation topology can be used. The first stage is a non-isolated two-level / three-level Buck-Boost circuit topology, and the second stage is an isolated LLC resonant circuit. The first stage is used to regulate the voltage, while the second stage is used for isolation. Alternatively, a single-stage Buck-Boost circuit topology can be used, which has good efficiency and dynamic response performance and can operate over a wide voltage input range. Cascaded LLC topologies are also a commonly used method. However, each of these methods has its own drawbacks, including high cost and complex circuit structure due to multi-stage conversion circuits, lack of isolation, large switching losses affecting converter efficiency, and reduced power density and efficiency due to increased switching transistors and passive components.

[0003] The inventors discovered that there is no simple topology with only one stage that can be obtained by improving the passive resonant converter topology to meet the application scenarios of wide-range voltage input, light load, heavy load and wide-range voltage output. Furthermore, improving the passive resonant converter topology by simply adding more resonant devices will directly lead to problems such as more parameters, more complex effects and greater difficulty in analysis. Summary of the Invention

[0004] To address the aforementioned problems, this invention proposes a passive resonant converter topology and its control method based on optimized parameter calculation. This invention adds two resonant devices to the classic LLC resonant converter, enabling its wide application in situations with wide-range voltage input, light load, heavy load, and wide-range voltage output. Furthermore, the proposed analysis method for the improved topology avoids the influence of multiple resonant devices, is easy to understand, and can quickly derive the values ​​of each parameter.

[0005] To achieve the above objectives, in a first aspect, the present invention provides a topology for a passive resonant converter based on optimized parameter calculation, employing the following technical solution:

[0006] The topology of the passive resonant converter based on optimized parameter calculation includes a DC voltage source, a first bridge arm circuit, a resonant converter cavity, a transformer, a second bridge arm circuit, and a load connected in sequence.

[0007] The resonant converter cavity includes a second inductor, a first capacitor, a third inductor, and a second capacitor connected in series at both ends of the first bridge arm circuit; a second capacitor is connected in parallel with the second inductor.

[0008] In the process of solving for voltage gain, when calculating the inductance ratio and quality factor, the resonant inductance is represented by the ratio of the inductance of the first inductor to the introduced resonant inductance coupling coefficient. The resonant inductance coupling coefficient is equal to the quotient of the inductance of the first inductor divided by the sum of the inductances of the first inductor and the second inductor.

[0009] Furthermore, the first bridge arm circuit is a full-bridge inverter circuit or a half-bridge inverter circuit; the second bridge arm circuit is a full-bridge rectifier circuit or a half-bridge rectifier circuit.

[0010] Furthermore, a third capacitor is connected in parallel to the DC voltage source, and a fourth capacitor is connected in parallel to the load; the third capacitor and the fourth capacitor are filter capacitors.

[0011] Furthermore, the voltage gain is calculated as follows: the product of the fourth power of the normalized frequency ratio, the inductance ratio, and 1 minus the difference in the resonant inductance coupling coefficient is used as the minuend; the product of the square of the normalized frequency ratio, the inductance ratio, and the capacitance ratio is used as the subtrahend; the ratio of the difference between the minuend and the subtrahend to the impedance is the voltage gain.

[0012] Furthermore, the inductance ratio is the ratio of the inductance of the third inductor to the product of the resonant inductor coupling coefficient and the inductance of the first inductor.

[0013] Furthermore, the impedance is,

[0014] Z(x) = x 4 k(1-d)+x 4 d(1-d)-x 2 nx 2 kn-x 2 (1-d)+n+jx 5 d(1-d)kQ-jx 3 knQ-jx 3 (1-d)kQ+jxknQ

[0015] Where x is the normalized frequency ratio; k is the inductance ratio; d is the resonant inductance coupling coefficient; n is the capacitance ratio; j is the imaginary unit; and Q is the quality factor.

[0016] Furthermore, the obtained voltage gain solution method is simulated, the gain curve is plotted, the influence of different parameters on the voltage gain is compared, the change curve that meets the requirements is selected, and the corresponding parameter values ​​are obtained. The parameter values ​​include the resonant inductance coupling coefficient, quality factor, n is the capacitance ratio, x is the normalized frequency ratio, inductance ratio, and resonant angular frequency.

[0017] Furthermore, the third inductor is a magnetizing inductor, provided by the transformer.

[0018] To achieve the above objectives, in a second aspect, the present invention also provides a topology control method for a passive resonant converter based on optimized parameter calculation, employing the following technical solution:

[0019] The topology control method for a passive resonant converter based on optimized parameter calculation adopts the topology of the passive resonant converter based on optimized parameter calculation as described in the first aspect; including: in the process of solving the voltage gain, when calculating the inductance ratio and quality factor, the resonant inductance is represented by the ratio of the inductance of the first inductor to the introduced resonant inductance coupling coefficient, wherein the resonant inductance coupling coefficient is equal to the quotient of the inductance of the first inductor divided by the sum of the inductance of the first inductor and the inductance of the second inductor.

[0020] Furthermore, the voltage gain is calculated as follows: the product of the fourth power of the normalized frequency ratio, the inductance ratio, and 1 minus the difference in the resonant inductance coupling coefficient is used as the minuend; the product of the square of the normalized frequency ratio, the inductance ratio, and the capacitance ratio is used as the subtrahend; the ratio of the difference between the minuend and the subtrahend to the impedance is the voltage gain.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention adds two resonant devices, a first capacitor and a first inductor, to the classic LLC resonant circuit, enabling its wide application in wide-range voltage input, light load, heavy load, and wide-range voltage output applications. Furthermore, the invention introduces a resonant inductor coupling coefficient during the voltage gain calculation of the improved topology. The proposed analysis method avoids the influence of multiple resonant devices, is easy to understand, and allows for rapid determination of parameter values. Attached Figure Description

[0023] 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.

[0024] Figure 1 This is the topology of Embodiment 1 of the present invention;

[0025] Figure 2 The equivalent circuit of the improved passive LC-LLC resonant converter in Embodiment 1 of the present invention;

[0026] Figure 3 This is the equivalent circuit of the LLC resonant converter in Embodiment 1 of the present invention;

[0027] Figure 4 The voltage gain curves of LLC and LC_LLC improved passive resonant converters under a certain set of parameters in Embodiment 1 of the present invention are shown. Detailed implementation method:

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] 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.

[0030] Example 1:

[0031] like Figure 1 As shown, this embodiment provides a topology for a passive resonant converter based on optimized parameter calculation, including a DC voltage source VDC, a first bridge arm circuit, a resonant converter cavity, a transformer, a second bridge arm circuit, and a DC load RL, etc. The first bridge arm circuit and the second bridge arm circuit can be configured as a full-bridge circuit or a half-bridge circuit.

[0032] A third capacitor C is connected in parallel to the DC voltage source VDC. IN The third capacitor C IN The capacitor serves as a voltage regulator and filter; the first bridge arm circuit consists of four or two controllable switching transistors. In this embodiment, the first bridge arm circuit may include a first switching transistor T1, a second switching transistor T2, a third switching transistor T3, and a fourth switching transistor T4; the resonant converter cavity includes a first inductor L1, a second inductor L2, and a first capacitor C. r Second capacitor C P and the third inductor L m The third inductor L m The magnetizing inductor is defined as follows: the second inductor L2 and the second capacitor C P It is a parallel structure, connected in series in the resonant circuit; the third inductor L m The magnetizing inductor can be provided by the transformer in practice, and its specific parameters can be obtained through the transformer design; the transformer has a turns ratio of n:1; the second bridge arm circuit consists of four or two uncontrolled / controllable switching transistors, which may include switching transistors D1, D2, D3, and D4; a fourth capacitor C is connected in parallel with the DC load RL. O The fourth capacitor C O For voltage regulation and filtering capacitor C O .

[0033] The improved passive resonant converter proposed in this embodiment includes the first inductor L1, the second inductor L2, and the first capacitor C. r The second capacitor C P and the third inductor L mWhile five resonant devices meet the requirements of wide-range input voltage, light load, heavy load, and wide-range output voltage, the modified passive resonant converter in this embodiment has many parameters with complex influences, making analysis difficult. Therefore, this embodiment also proposes a comparative analysis design method for a modified passive resonant converter combined with LLC resonant converter design. The proposed analysis method avoids the influence of multiple resonant devices, is easy to understand, can quickly derive the values ​​of each parameter, and can intuitively show the advantages of the modified passive resonant converter over the LLC resonant converter in wide-range adjustment. In this embodiment, the parameter design method is as follows:

[0034] like Figure 2 As shown, an AC equivalent circuit model is established for the improved passive resonant converter. The model includes the following components: AC power supply v ab A resonant cavity, resonant devices, and a resistor R; wherein, the AC power supply v ab The fundamental component of the square wave output voltage of the bridge arm of the inverter circuit; the resistor R is different from the DC load RL shown in the topology, the resistor R is the DC load RL on the secondary side of the transformer, and the fourth capacitor C O The resistance value is equivalent to that of the second bridge arm circuit on the primary side of the transformer.

[0035] Similarly, such as Figure 3 As shown, an AC equivalent circuit model of the LLC resonant converter is established, where: AC power supply v ab The fundamental component of the square wave output voltage of the bridge arm of the inverter circuit; resistor R is the load RL on the secondary side of the transformer; and capacitor C is the fourth capacitor. O The equivalent resistance value on the primary side of the transformer, which is the same as the overall resistance value of the rectifier bridge circuit.

[0036] In this embodiment, the fundamental harmonic approximation (FHA) and impedance method are used to calculate their respective voltage transfer gain G (Voltage Gain).

[0037] In this embodiment, firstly, a mathematical model analysis is established for the LLC resonant circuit, and its voltage gain G is determined. LLC The expression is:

[0038]

[0039] Wherein, the complex variable s = jω, j is the imaginary unit, ω is the operating angular frequency; R is the resistance, RL is the DC load on the secondary side of the transformer, and the fourth capacitor C is... O The equivalent resistance value on the primary side of the transformer for the second bridge arm circuit; L m C is the inductance of the magnetizing inductor. rL is the capacitance value of the first capacitor; r It is a resonant inductor.

[0040] For ease of analysis, the following auxiliary parameters are set:

[0041]

[0042]

[0043]

[0044]

[0045] Where Q is the quality factor; L r For resonant inductance; C r R is the capacitance value of the first capacitor; R is the resistance; RL is the DC load on the secondary side of the transformer; and C is the fourth capacitor. O The resistance value equivalent to that of the second bridge arm circuit on the primary side of the transformer; k is the inductance ratio; ω0 is the resonant angular frequency; f0 is the resonant frequency; f is the operating frequency; x is the normalized frequency ratio, which is equal to the ratio of the operating angular frequency to the resonant angular frequency; ω is the operating angular frequency.

[0046] From this we can obtain

[0047]

[0048] Then, a mathematical model analysis was established for the improved passive CL-LLC resonant converter, and its voltage gain G was analyzed. CL_LLC The expression is:

[0049]

[0050] Wherein, the complex variable s = jω; j is the imaginary unit, ω is the operating angular frequency; R is the resistance, RL is the DC load on the secondary side of the transformer, and the fourth capacitor C is the fourth capacitor. O The equivalent resistance value on the primary side of the transformer for the second bridge arm circuit; L m C is the inductance of the magnetizing inductor. r L1 is the capacitance of the first capacitor; L2 is the inductance of the first inductor; C is the inductance of the second inductor; P Z(s) is the capacitance value of the second capacitor; Z(s) is the impedance expression in the denominator.

[0051] Z(s) = s 5 L1L2L m C r C P +s 4 RL2L m C r C P+s 4 RL1L2C r C P +s 3 (L1+L2)C r +s 3 L2L m C P +s 2 R(L1+L2)C r +s 2 RL m C r +s 2 RL2C P +sL m +R

[0052] For G LC_LLC Further resolution yields:

[0053]

[0054] in:

[0055] Z(ω)=ω 4 RL2L m C r C P +ω 4 RL1L2C r C Pr -ω 2 R(L1+L2)C r -ω 2 RL m C r -ω 2 RL2C P +R+jω 5 L1L2L m C r C P -jω 3 (L1+L2)C-jω 3 L2L m C P +jωL m

[0056] Observe the voltage gain G CL_LLC The expression has many parameters, a wide degree of freedom, a high order, and a complex mathematical expression. Therefore, this embodiment has made a rational setting. Considering the resonant characteristics of the resonant cavity circuit, the resonant inductance L is set to... r =L1+L2, and at the same time, add the resonant inductance coupling coefficient d, let L1 = dL r .

[0057] Wherein, the value of d ranges from [0, 1), and d cannot be 0. This setting not only simplifies the calculation but also has practical physical meaning, indicating that the resonant inductance L1 formed by the first inductor L1 and the second inductor L2 is... r The overall impact of resonance.

[0058] In this embodiment, the following auxiliary parameters are set to simplify calculations and analysis:

[0059]

[0060]

[0061]

[0062]

[0063]

[0064] Where Q is the quality factor; L r For resonant inductance; C r R is the capacitance value of the first capacitor; R is the resistance; RL is the DC load on the secondary side of the transformer; and C is the fourth capacitor. O The resistance value equivalent to that of the second bridge arm circuit on the primary side of the transformer; k is the inductance ratio; ω0 is the resonant angular frequency; L2 is the inductance of the second inductor; f is the operating frequency; x is the normalized frequency ratio; ω is the operating angular frequency; d is the resonant inductor coupling coefficient.

[0065] Substituting into the above equation G LC_LLC have:

[0066]

[0067] in:

[0068] Z(x) = x 4 k(1-d)+x 4 d(1-d)-x 2 nx 2 kn-x 2 (1-d)+n+jx 5 d(1-d)kQ-jx 3 knQ-jx 3 (1-d)kQ+jxknQ

[0069] Where n is the capacitance ratio.

[0070] Finally, a mathematical model of the LLC resonant circuit is established for analysis and improvement. The voltage gain expression G obtained from the mathematical model analysis of the LLC resonant circuit is then presented. LLC and GLC_LLC Perform simulations, plot gain curves, compare the impact of different parameters on voltage gain, and select the parameter that meets the requirements or achieves the optimal performance G. LC_LLC The curves are used to obtain the corresponding parameter values, including the resonant inductance coupling coefficient d, quality factor Q, capacitance ratio n, normalized frequency ratio x, inductance ratio k, and resonant angular frequency ω0. Then, using the above parameter formulas, their respective parameters are deduced, including the first inductor L1, the second inductor L2, and the first capacitor C. r The second capacitor C P and the third inductor L m The value of .

[0071] like Figure 4 The figures show the voltage gain curves of the LLC and LC_LLC improved passive resonant converters under a certain set of parameters. It can be observed from the figures that the voltage gain range of LC_LLC is wider and changes faster. At the same time, the curve of LC_LLC is also better than that of LLC under different Q values ​​(representing the change of load R).

[0072] The improved passive resonant converter topology proposed in this embodiment features a single-stage structure, resulting in a simple design. Compared to LLC resonant converters, this topology uses a smaller resonant inductor value. Furthermore, the LC-LLC voltage gain characteristic curve is superior to that of LLC resonant converters, addressing both the shortcomings and advantages of LLC resonant converters. Compared to the original two-stage topology that enables wide-range input and output, this new topology uses fewer components, resulting in lower production costs. It also allows for the use of magnetic integration technology to optimize inductor / transformer design, significantly improving power density and reducing size. This topology can be widely applied to applications with wide-range voltage input, light load, heavy load, and wide-range voltage output, and it also enables soft-switching technology.

[0073] This embodiment proposes a parameter design method for an improved passive resonant converter with a wide input / output range. Compared with the classic LLC resonant converter, the improved passive LC-LLC resonant converter adds two resonant devices, increasing its order from third to fifth, which increases the analysis difficulty. At the same time, the correlation between the variables is strong and has many influences. Based on this, a parameter design method for an improved passive resonant converter with a wide input / output range is proposed, which is easy to understand and easy to analyze and compare. After modeling and plotting the voltage gain curve, it has observable characteristics.

[0074] Example 2:

[0075] This embodiment provides a topology control method for a passive resonant converter based on optimized parameter calculation, which adopts the topology of the passive resonant converter based on optimized parameter calculation as described in Embodiment 1; including: in the process of solving the voltage gain, when calculating the inductance ratio and quality factor, the resonant inductance is represented by the ratio of the inductance of the first inductor to the introduced resonant inductance coupling coefficient, wherein the resonant inductance coupling coefficient is equal to the quotient of the inductance of the first inductor divided by the sum of the inductance of the first inductor and the inductance of the second inductor.

[0076] In this embodiment, the voltage gain is calculated as follows: the product of the fourth power of the normalized frequency ratio, the inductance ratio, and 1 minus the difference in the resonant inductance coupling coefficient is used as the minuend; the product of the square of the normalized frequency ratio, the inductance ratio, and the capacitance ratio is used as the subtrahend; the ratio of the difference between the minuend and the subtrahend to the impedance is the voltage gain.

[0077] 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 topology for a passive resonant converter based on optimized parameter calculation, characterized in that, It includes a DC voltage source, a first bridge arm circuit, a resonant converter cavity, a transformer, a second bridge arm circuit, and a load connected in sequence; The resonant converter cavity includes a second inductor, a first capacitor, a third inductor, and a second capacitor connected in series at both ends of the first bridge arm circuit; a second capacitor is connected in parallel with the second inductor. In the process of solving for voltage gain, when calculating the inductance ratio and quality factor, the resonant inductance is represented by the ratio of the inductance of the first inductor to the introduced resonant inductance coupling coefficient. The resonant inductance coupling coefficient is equal to the quotient of the inductance of the first inductor divided by the sum of the inductance of the first inductor and the inductance of the second inductor. The voltage gain is calculated as follows: the product of the fourth power of the normalized frequency ratio, the inductance ratio, and 1 minus the difference in the resonant inductance coupling coefficient is used as the minuend; the product of the square of the normalized frequency ratio, the inductance ratio, and the capacitance ratio is used as the subtrahend; the ratio of the difference between the minuend and the subtrahend to the impedance is the voltage gain. The inductance ratio is the ratio of the inductance of the third inductor to the product of the resonant inductor coupling coefficient and the inductance of the first inductor.

2. The topology of the passive resonant converter based on optimized parameter calculation as described in claim 1, characterized in that, The first bridge arm circuit is a full-bridge inverter circuit or a half-bridge inverter circuit; the second bridge arm circuit is a full-bridge rectifier circuit or a half-bridge rectifier circuit.

3. The topology of the passive resonant converter based on optimized parameter calculation as described in claim 1, characterized in that, A third capacitor is connected in parallel to the DC voltage source, and a fourth capacitor is connected in parallel to the load; the third capacitor and the fourth capacitor are filter capacitors.

4. The topology of the passive resonant converter based on optimized parameter calculation as described in claim 1, characterized in that, The impedance is, in, Normalized frequency ratio; Inductance ratio; The resonant inductance coupling coefficient; It is the capacitance ratio; The imaginary unit; This is the quality factor.

5. The topology of the passive resonant converter based on optimized parameter calculation as described in claim 4, characterized in that, The obtained voltage gain solution is simulated, the gain curve is plotted, the influence of different parameters on the voltage gain is compared, the change curve that meets the requirements is selected, and the corresponding parameter values ​​are obtained. The parameter values ​​include resonant inductor coupling coefficient, quality factor, capacitance ratio, normalized frequency ratio, inductance ratio and resonant angular frequency.

6. The topology of the passive resonant converter based on optimized parameter calculation as described in claim 1, characterized in that, The third inductor is a magnetizing inductor, which is provided by the transformer.

7. A topology control method for a passive resonant converter based on optimized parameter calculation, characterized in that, The passive resonant converter topology based on optimized parameter calculation as described in any one of claims 1-6 is adopted; including: in the process of solving the voltage gain, when calculating the inductance ratio and quality factor, the resonant inductance is represented by the ratio of the inductance of the first inductor to the introduced resonant inductance coupling coefficient, wherein the resonant inductance coupling coefficient is equal to the quotient of the inductance of the first inductor divided by the sum of the inductance of the first inductor and the inductance of the second inductor.

8. The topology control method for a passive resonant converter based on optimized parameter calculation as described in claim 7, characterized in that, The voltage gain is calculated as follows: the product of the fourth power of the normalized frequency ratio, the inductance ratio, and 1 minus the difference in the resonant inductance coupling coefficient is used as the minuend; the product of the square of the normalized frequency ratio, the inductance ratio, and the capacitance ratio is used as the subtrahend; the ratio of the difference between the minuend and the subtrahend to the impedance is the voltage gain.

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