Power control method of resonant converter and resonant converter
By adjusting the frequency of the resonant converter and precisely designing the resonant cavity circuit, the problems of high difficulty and low efficiency in soft switching of dual active bridge converters over a wide power range were solved, achieving near unity power factor operation and stable power regulation with low loss.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- HOYMILES POWER ELECTRONICS INC
- Filing Date
- 2026-05-07
- Publication Date
- 2026-06-16
AI Technical Summary
Existing dual active bridge converters are difficult to implement soft switching over a wide power range, and the modulation algorithm is complex, which leads to increased reactive current and resonant current, low efficiency, and easy loss of soft switching under light load.
By adjusting the frequency of the resonant converter within a limited frequency adjustment range, the constraints for achieving unity power factor of the resonant converter are determined, the resonant cavity circuit is precisely designed, and near unity power factor operation is achieved, reducing input-side current and losses.
It achieves soft switching over a wide power range, reduces reactive power and losses, improves efficiency, avoids the difficulties caused by modulation methods, and ensures stable operation under light and full load conditions.
Smart Images
Figure CN122225802A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power electronics technology, and more specifically, to a power control method for a resonant converter and a resonant converter. Background Technology
[0002] In the field of power electronics, dual active bridge (DAB) converters are widely used due to their advantages such as electrical isolation, bidirectional power transmission, and ease of soft switching.
[0003] In related technologies, phase shifting, frequency modulation, or hybrid modulation methods are typically used to enable soft switching of dual active bridge converters over a wide power range.
[0004] However, the shortcomings of the related technologies are as follows: First, the modulation algorithm is complex and difficult to implement; second, modulation will lead to a decrease in the equivalent voltage, which will increase the current under the same power conditions, especially the reactive current and resonant current; third, in order to achieve soft switching, a phase deviation will be generated between the modulated voltage and current, which is easy to lose soft switching under light load, and the deeper the modulation, the lower the efficiency. Summary of the Invention
[0005] The present invention aims to at least solve one of the technical problems existing in the prior art, and provides a power control method and a resonant converter for a resonant converter. By adjusting the frequency of the resonant converter within a limited frequency adjustment range to achieve power regulation, the invention solves the problems of complex modulation algorithms, high implementation difficulty, increased reactive current and resonant current, and low efficiency in related technologies.
[0006] In a first aspect, the present invention provides a power control method for a resonant converter, the resonant converter comprising a primary-side inverter circuit, at least one resonant cavity circuit, and a secondary-side rectifier circuit connected in sequence; the primary-side inverter circuit comprising a plurality of switching transistors forming a primary-side full-bridge circuit; the resonant cavity circuit comprising a transformer, at least one inductor, and at least one capacitor; the secondary-side rectifier circuit comprising a plurality of switching transistors forming a secondary-side full-bridge circuit; the power control method comprising the following steps:
[0007] Based on the circuit equations of the resonant converter, the constraints for achieving unity power factor of the resonant converter are determined, and the constraints include the resonant parameter conditions of the resonant cavity circuit.
[0008] The frequency adjustment range of the resonant converter is determined based on the aforementioned constraints.
[0009] Within the frequency adjustment range, power regulation is achieved by adjusting the frequency of the resonant converter.
[0010] In some embodiments, the step of determining the constraint conditions for the resonant converter to achieve unity power factor based on the circuit equations of the resonant converter includes:
[0011] The expression for the output power of the resonant converter is determined based on the circuit equations.
[0012] The expression for the input impedance angle corresponding to the resonant converter is determined based on the circuit equation and the expression for the output power.
[0013] The constraint condition is determined when the input impedance angle is zero.
[0014] In some embodiments, before determining the constraint conditions for the resonant converter to achieve unity power factor based on the circuit equations of the resonant converter, the power control method further includes: establishing the circuit equations of the resonant converter based on the fundamental wave analysis method, wherein the circuit equations include expressions for the input voltage phasors of the primary-side inverter circuit and expressions for the output voltage phasors of the secondary-side rectifier circuit.
[0015] In some embodiments, the resonant cavity circuit includes a transformer, a central capacitor, a first LC branch, and a second LC branch. The central capacitor is connected in parallel with the primary winding or secondary winding of the transformer, and the first LC branch and the second LC branch are symmetrically arranged with respect to the central capacitor.
[0016] The parameter values of each component in the first LC branch and the second LC branch, as well as the parameter value of the center capacitor, are equivalently converted to the same side of the transformer according to the turns ratio of the transformer to obtain the corresponding equivalent values. The constraints include that the equivalent inductance values in the first LC branch and the second LC branch are equal, the equivalent capacitance values in the first LC branch and the second LC branch are equal, and the effective value of the input voltage of the primary inverter circuit is equal to the product of the effective value of the output voltage of the secondary rectifier circuit and the turns ratio of the transformer.
[0017] In some embodiments, the frequency adjustment range includes an upper limit value and a lower limit value for frequency adjustment;
[0018] The upper limit value for frequency adjustment is:
[0019] ;
[0020] The lower limit value for frequency adjustment is:
[0021] ;
[0022] In the formula, This represents the equivalent capacitance value of the central capacitor; This represents the equivalent capacitance value in the first LC branch and the second LC branch; This represents the equivalent inductance value in the first LC branch and the second LC branch.
[0023] In some embodiments, the resonant cavity circuit includes a transformer, a center inductor, a first LC branch, and a second LC branch. The center inductor is connected in parallel with the primary winding or secondary winding of the transformer, and the first LC branch and the second LC branch are symmetrically arranged with respect to the center inductor.
[0024] The parameter values of each component in the first LC branch and the second LC branch, as well as the parameter value of the center inductor, are equivalently converted to the same side of the transformer based on the turns ratio of the transformer to obtain the corresponding equivalent values. The constraints include that the equivalent inductance values in the first LC branch and the second LC branch are equal, the equivalent capacitance values in the first LC branch and the second LC branch are equal, and the effective value of the input voltage of the primary-side inverter circuit is equal to the product of the effective value of the output voltage of the secondary-side rectifier circuit and the turns ratio of the transformer.
[0025] In some embodiments, the frequency adjustment range includes an upper limit value and a lower limit value for frequency adjustment;
[0026] The upper limit value for frequency adjustment is:
[0027] ;
[0028] The lower limit value for frequency adjustment is:
[0029] ;
[0030] In the formula, This represents the equivalent inductance value of the central inductor; This represents the equivalent capacitance value in the first LC branch and the second LC branch; This represents the equivalent inductance value in the first LC branch and the second LC branch.
[0031] In a second aspect, the present invention provides a resonant converter, the resonant converter comprising a controller, a primary-side inverter circuit, at least one resonant cavity circuit, and a secondary-side rectifier circuit connected in sequence; the primary-side inverter circuit comprises a plurality of switching transistors forming a primary-side full-bridge circuit; the resonant cavity circuit comprises a transformer, at least one inductor, and at least one capacitor; the secondary-side rectifier circuit comprises a plurality of switching transistors forming a secondary-side full-bridge circuit; the controller applies the power control method of the resonant converter described in any one of the embodiments of the first aspect.
[0032] In some embodiments, the resonant cavity circuit includes a transformer, a center capacitor, a first LC branch, and a second LC branch. The center capacitor is connected in parallel with the primary winding or secondary winding of the transformer, and the first LC branch and the second LC branch are symmetrically arranged with respect to the center capacitor.
[0033] In some embodiments, the resonant cavity circuit includes a transformer, a center inductor, a first LC branch, and a second LC branch. The center inductor is connected in parallel with the primary winding or secondary winding of the transformer, and the first LC branch and the second LC branch are symmetrically arranged with respect to the center inductor.
[0034] The present invention has the following beneficial effects:
[0035] The power control method and resonant converter provided by this invention, by determining the constraints for the resonant converter to achieve a unity power factor, further limits the resonant parameter conditions of the resonant cavity circuit, and precisely designs the resonant cavity circuit, so that the phase difference between the fundamental current and fundamental voltage on the input side of the resonant converter is very small (close to 0), and the power factor is close to 1. The resonant converter can achieve an operating state with approximately unity power factor and significantly reduce the reactive power on the input side. Within the frequency adjustment range determined based on the constraints, the power regulation of the resonant converter from full load to light load can be achieved by frequency adjustment alone. Furthermore, while achieving soft switching, the current and losses on the power input side can be reduced, and the power output side can operate in rectification mode with low losses. This effectively avoids the problems of difficulty in achieving soft switching, increased equivalent current, increased reactive power, and reduced efficiency caused by modulation methods in related technologies. Attached Figure Description
[0036] Figure 1 This is a circuit structure block diagram of a dual active bridge converter provided in an embodiment of the present invention;
[0037] Figure 2 This is a first topology diagram of the resonant cavity circuit provided in an embodiment of the present invention;
[0038] Figure 3 This is a second topology diagram of the resonant cavity circuit provided in an embodiment of the present invention;
[0039] Figure 4 This is a third topology diagram of the resonant cavity circuit provided in an embodiment of the present invention;
[0040] Figure 5 This is a fourth topology diagram of the resonant cavity circuit provided in an embodiment of the present invention;
[0041] Figure 6 This is a circuit structure diagram of a three-phase dual active bridge converter provided in an embodiment of the present invention;
[0042] Figure 7 A flowchart of a power control method for a resonant converter provided in an embodiment of the present invention;
[0043] Figure 8 A flowchart for determining constraints provided in an embodiment of the present invention;
[0044] Figure 9 This is a diagram illustrating the relationship between the output power and operating frequency of the resonant converter provided in an embodiment of the present invention.
[0045] Figure 10 This is a diagram illustrating the power regulation effect of the resonant converter operating frequency near the lower limit of the frequency regulation, as provided in an embodiment of the present invention.
[0046] Figure 11 This is a diagram illustrating the relationship between output power and operating frequency when the resonant parameters change, as provided in an embodiment of the present invention.
[0047] Figure 12 This is a diagram illustrating another form of resonant cavity circuit structure provided in an embodiment of the present invention. Detailed Implementation
[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0049] It should be noted that although functional modules are divided in the device schematic diagram and the logical order is shown in the flowchart, in some cases, the steps shown or described may be executed in a different order than the module division in the device or the order in the flowchart. In the description of this invention, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features. Unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "setting," and "arrangement," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.
[0050] like Figure 1 and Figure 2As shown, the resonant converter includes a primary-side inverter circuit 10, at least one resonant cavity circuit 20, and a secondary-side rectifier circuit 30 connected in sequence. The primary-side inverter circuit 10 includes multiple switching transistors forming a primary-side full-bridge circuit. The resonant cavity circuit 20 includes a transformer, at least one inductor, and at least one capacitor. The secondary-side rectifier circuit 30 includes multiple switching transistors forming a secondary-side full-bridge circuit. When the resonant converter is a single-phase resonant converter, there is only one resonant cavity circuit 20; when the resonant converter is a multi-phase resonant converter, there are multiple resonant cavity circuits 20.
[0051] In some specific embodiments of the present invention, such as Figure 2 As shown, the resonant converter includes a primary-side inverter circuit 10, a resonant cavity circuit 20, and a secondary-side rectifier circuit 30 connected in sequence. The primary-side inverter circuit 10 is a primary-side full-bridge circuit composed of four switching transistors S1, S2, S3, and S4 and a power supply Vp. The resonant cavity circuit 20 includes a transformer T, a center capacitor, a first LC branch, and a second LC branch. The center capacitor is connected in parallel with either the primary or secondary winding of the transformer T. The first and second LC branches are symmetrically arranged with respect to the center capacitor. The secondary-side rectifier circuit 30 is a secondary-side full-bridge circuit composed of four switching transistors Q1, Q2, Q3, and Q4 and a power supply Vs.
[0052] In some embodiments, as a first topology of the resonant cavity circuit 20, such as Figure 2 As shown, the first LC branch, the second LC branch, and the central capacitor C3 are all located on one side of the primary winding of transformer T. The first LC branch and the second LC branch are symmetrically arranged with respect to the central capacitor C3. Specifically, the first LC branch includes a first inductor L1 and a first capacitor C1, and the second LC branch includes a second inductor L2 and a second capacitor C2. The first inductor L1, the first capacitor C1, the second capacitor C2, and the second inductor L2 are connected in series at one end of the primary winding of transformer T. One end of the central capacitor C3 is connected to the node between the first capacitor C1 and the second capacitor C2, and the other end of the central capacitor C3 is connected to the other end of the primary winding of transformer T.
[0053] In some embodiments, as a second topology of the resonant cavity circuit 20, such as Figure 3As shown, the first LC branch and the second LC branch are symmetrically arranged with respect to the center capacitor C3. The first LC branch includes a first inductor L1 and a first capacitor C1, and the second LC branch includes a second inductor L2 and a second capacitor C2. The first inductor L1, the first capacitor C1, the second capacitor C2, and the center capacitor C3 are arranged on the primary side of the transformer T, and the second inductor L2 is arranged on the secondary side of the transformer T. Specifically, the first inductor L1, the first capacitor C1, and the second capacitor C2 are connected in series at one end of the primary winding of the transformer T. One end of the center capacitor C3 is connected to the node between the first capacitor C1 and the second capacitor C2, and the other end of the center capacitor C3 is connected to the other end of the primary winding of the transformer T. The second inductor L2 is connected in series at one end of the secondary winding of the transformer T.
[0054] In some embodiments, as a third topology of the resonant cavity circuit 20, such as Figure 4 As shown, the first LC branch and the second LC branch are symmetrically arranged with respect to the center capacitor C3. The first LC branch is located on the primary winding side of transformer T, and the second LC branch and the center capacitor C3 are located on the secondary winding side of transformer T. The first LC branch includes a first inductor L1 and a first capacitor C1, and the second LC branch includes a second inductor L2 and a second capacitor C2. Specifically, the first inductor L1 and the first capacitor C1 are connected in series at one end of the primary winding of transformer T, the second capacitor C2 and the second inductor L2 are connected in series at one end of the secondary winding of transformer T, one end of the center capacitor C3 is connected to the end of the second capacitor C2 away from the second inductor L2, and the other end of the center capacitor C3 is connected to the other end of the secondary winding of transformer T.
[0055] In some embodiments, as a fourth topology of the resonant cavity circuit 20, such as Figure 5 As shown, the first LC branch, the second LC branch, and the central capacitor C3 are all located on one side of the secondary winding of transformer T. The first LC branch and the second LC branch are symmetrically arranged with respect to the central capacitor C3. Specifically, the first LC branch includes a first inductor L1 and a first capacitor C1, and the second LC branch includes a second inductor L2 and a second capacitor C2. The first inductor L1, the first capacitor C1, the second capacitor C2, and the second inductor L2 are connected in series at one end of the secondary winding of transformer T. One end of the central capacitor C3 is connected to the node between the first capacitor C1 and the second capacitor C2, and the other end of the central capacitor C3 is connected to the other end of the secondary winding of transformer T.
[0056] It should be noted that other topologies of the resonant cavity circuit 20 will not be listed here. Their equivalent structures can satisfy the CLCLC type arrangement and ensure that the first LC branch and the second LC branch are symmetrically arranged with respect to the center capacitor.
[0057] In some embodiments, the resonant converter can also be a multiphase resonant converter, such as a three-phase resonant converter, like... Figure 6 As shown. The resonant cavity circuit 20 in the multiphase resonant converter can be adjusted according to the above-described topology, which will not be elaborated here.
[0058] Based on the structure of the resonant converter described above, in a first aspect, embodiments of the present invention provide a power control method for the resonant converter, such as... Figure 7 As shown, it includes the following steps:
[0059] S710. Based on the circuit equations of the resonant converter, determine the constraints for the resonant converter to achieve unity power factor. The constraints include the resonant parameter conditions of the resonant cavity circuit.
[0060] S720. Determine the frequency adjustment range of the resonant converter based on constraints;
[0061] S730: Within the frequency adjustment range, power regulation is achieved by adjusting the frequency of the resonant converter.
[0062] The above-described constraints for achieving unity power factor in the resonant converter further limit the resonant parameters of the resonant cavity circuit, enabling precise design of the circuit. This results in a very small (near-zero) phase difference between the fundamental current and voltage at the input of the resonant converter, leading to a power factor close to 1. The resonant converter can achieve near-unity power factor operation and significantly reduce reactive power at the input. Within the frequency adjustment range determined by the constraints, power regulation from full load to light load can be achieved solely through frequency adjustment. Furthermore, while implementing soft switching, it reduces current and losses at the power input, allowing the power output to operate in rectification mode with lower losses. This effectively avoids the difficulties in achieving soft switching, increased equivalent current, increased reactive power, and reduced efficiency associated with modulation methods in related technologies.
[0063] In some specific embodiments of the present invention, in step S710, the resonance parameter condition refers to the condition that the parameters of the energy storage elements (inductors and capacitors) in the circuit must meet in order for the circuit to resonate at a specific frequency (i.e., the port exhibits pure resistance, and the voltage and current are in phase).
[0064] In some specific embodiments of the present invention, before performing step S710, the power control method further includes: establishing the circuit equation of the resonant converter based on the fundamental wave analysis method, wherein the circuit equation includes the expression of the input voltage phasor of the primary side inverter circuit and the expression of the output voltage phasor of the secondary side rectifier circuit.
[0065] Specifically, based on the fundamental frequency analysis method and Thevenin's circuit theorem, the circuit equation expression of the resonant converter is as follows:
[0066] (1)
[0067] Formula (1) can be converted into matrix form as follows:
[0068] (2)
[0069] In the formula, This represents the effective value of the input voltage of the primary-side inverter circuit. Indicates the corresponding phasor; This represents the effective value of the input current in the primary-side inverter circuit. Indicates the corresponding phasor; This indicates the effective value of the output voltage of the secondary rectifier circuit. Indicates the corresponding phasor; This represents the effective value of the output current of the secondary rectifier circuit. Indicates the corresponding phasor; This represents the capacitive reactance of a capacitor. Values are 1, 2, and 3; Indicating the inductive reactance of an inductor Values 1 and 2; This indicates the turns ratio of the primary and secondary windings of the transformer; Indicates frequency.
[0070] In some specific embodiments of the present invention, such as Figure 8 As shown, step S710 includes:
[0071] S711. Determine the expression for the output power of the resonant converter based on the circuit equations;
[0072] S712. Determine the expression for the input impedance angle of the resonant converter based on the circuit equation and the expression for output power;
[0073] S713. Determine the constraint conditions when the input impedance angle is zero.
[0074] Specifically, in step S711, formula (2) is processed, and the upper and lower formulas are... Substituting phasors into the equation for elimination leaves only one equation, containing only... , , Phasors and resonance parameters. Divide both sides of the equation by . phasors, then only remain phasor sum Phasor. Phasors can be simplified to , Phasors can be simplified to .
[0075] calculate The output power of the resonant converter can be obtained by determining the magnitude of the phasor. The expression for output power. The expression is as follows:
[0076] (3)
[0077] Specifically, in step S712, formula (2) is processed, and the two formulas are... Substituting phasors into the equation for elimination leaves only one equation, containing only... , , Phasors and resonance parameters. Divide both sides of the equation by . phasors, then only remain phasor sum phasor. phasor sum Substituting the phasor into formula (3) yields the input impedance angle. The expression for the input impedance angle. The expression is as follows:
[0078] (4)
[0079] Specifically, in step S713, at the input impedance angle When it is zero, that is The numerator of the function must always be zero, so we can obtain...
[0080] (5)
[0081] According to formula (5), based on the structure of the resonant converter described above, when the components in the first LC branch and the second LC branch are located on the same side of the transformer T (for example...), Figure 2 and Figure 5 As shown), at this point, the constraint conditions for the resonant converter to achieve unity power factor can be determined as follows: the inductance values in the first LC branch and the second LC branch are equal, the capacitance values in the first LC branch and the second LC branch are equal, and the effective value of the input voltage of the primary inverter circuit is equal to the product of the effective value of the output voltage of the secondary rectifier circuit and the turns ratio of the transformer.
[0082] When the components in the first LC branch and the second LC branch, as well as the central capacitor C3, are located on opposite sides of the transformer T (for example...), Figure 3 and Figure 4As shown in the diagram, the parameter values of each component in the first and second LC branches, as well as the parameter value of the center capacitor C3, need to be equivalently converted to the same side of the transformer based on the transformer's turns ratio (for example, the side with fewer components is equivalently converted to the side with more components) to obtain the corresponding equivalent values. At this point, the constraint condition for the resonant converter to achieve unity power factor can be determined as follows: the equivalent values of the inductors in the first and second LC branches are equal; the equivalent values of the capacitors in the first and second LC branches are equal; and the effective value of the input voltage of the primary inverter circuit is equal to the product of the effective value of the output voltage of the secondary rectifier circuit and the transformer's turns ratio. For components not involved in the equivalent conversion, their equivalent values are taken as their original values.
[0083] For example, such as Figure 3 As shown, the inductance value of the second inductor L2 in the second LC branch located on the secondary winding side of transformer T is equivalently converted to the primary winding side of transformer T. The second capacitor C2 in the second LC branch, the first inductor L1 and the first capacitor C1 in the first LC branch, and the center capacitor C3 are already on the primary winding side of transformer T. Therefore, their parameter values do not need to participate in the equivalent conversion. The equivalent values of the second capacitor C2, the first inductor L1 and the first capacitor C1, and the center capacitor C3 are taken as their original values.
[0084] If the resonant converter satisfies the above constraints, the input impedance angle can be guaranteed. When the power factor is zero, it achieves an operating state close to unity. When power is transferred in the reverse direction, i.e. from... Lateral When energy is transferred to the side, the constraints obtained are the same as those described above.
[0085] In some specific embodiments of the present invention, in step S720, the resonance parameters are simplified as follows, based on satisfying the above constraints:
[0086] (6)
[0087] Based on formula (6), the output power in formula (3) The expression is simplified as follows:
[0088] (7)
[0089] According to formula (7), when the output power When both the numerator and denominator are 0 in the expression, the output power is... Approaching infinity, from which two... The values are the upper and lower limits of frequency adjustment.
[0090] The upper limit for frequency adjustment is:
[0091] (8)
[0092] The lower limit for frequency adjustment is:
[0093] (9)
[0094] In the formula, This represents the equivalent capacitance of the center capacitor. This represents the equivalent capacitance value in the first LC branch and the second LC branch; This represents the equivalent inductance value in the first LC branch and the second LC branch. For components not involved in the equivalent conversion, their equivalent values are taken as their original values.
[0095] It should be noted that due to the presence of non-ideal parameters such as component resistance and inductance in actual resonant converter systems, the actual power of the resonant converter tends to a relatively large value, making it impossible to achieve ideal infinite power. When the operating frequency is... and Between these values, the output power is relatively low, which can be used to achieve light-load operation of the system. Using the power control method described above for the resonant converter, the power characteristics and input impedance angle characteristics of the resonant converter are obtained as follows: Figure 9 As shown, the left vertical axis represents the output power. For rated power The per-unit value, with the right vertical axis representing the input impedance angle. The horizontal axis represents the operating frequency. .from Figure 9 From this, we can derive the input impedance angle. The value is always 0, indicating that the inverter side square wave voltage and sinusoidal current are always in phase. and The frequencies are 100kHz and 190kHz respectively.
[0096] Resonant converter at the lower limit of frequency adjustment Nearby frequency control, such as Figure 10 As shown, at an operating frequency of 100.2kHz (i.e. Figure 10 When the resonant converter is at X100290 (as shown in the diagram), it can output full-load power. When the resonant converter needs to output light-load power, simply implement frequency control and adjust the frequency to 116kHz (i.e., ...). Figure 10 At X116000 (in the settings), 15% of the full-load power output can be achieved. Similarly, the upper limit of the frequency adjustment can also be selected. Frequency control is being implemented in the vicinity.
[0097] The resonant converter achieves soft switching by slightly increasing or decreasing a certain resonant parameter (inductance value, capacitance value, etc.) while satisfying the above constraints. Since the resonant parameter is only slightly adjusted, its impact on power characteristics can be considered minimal.
[0098] Taking zero-voltage switching (ZVS) with a switching transistor as an example, the equivalent impedance of the high-frequency full-bridge inverter resistor needs to be weakly inductive. Therefore, while satisfying the above constraints, the inductance value of the first inductor L1 can be slightly increased to 1.05 to 1.10 times, thereby achieving zero-voltage switching. Figure 11 As shown, taking a slight increase in the inductance value of the first inductor L1 as an example, the input impedance angle of the resonant converter is... The input impedance changes from a constant zero to around 5°–7°, remaining weakly inductive throughout, with the current slightly lagging behind the square wave voltage, allowing the resonant converter to achieve zero-voltage switching. Furthermore, due to the small input impedance angle, the introduced reactive power is negligible, and the resonant converter efficiency remains unaffected. Additionally, the full-load frequency and the 15% light-load frequency become 98.8kHz (i.e.,...). Figure 11 (at X98790 in the text) and 114.9kHz (i.e. Figure 11 (At X114970 in the diagram). Therefore, it can be seen that increasing the first inductor L1 has minimal impact on the power characteristics of the resonant converter.
[0099] In some specific embodiments of the present invention, the structure of the resonant cavity circuit 20 can also be a CLLLC structure, provided that the number of magnetic components (such as inductors) is ignored. Figure 12 As shown, the resonant cavity circuit includes a transformer T, a center inductor L3, a first LC branch, and a second LC branch. The center inductor L3 is connected in parallel with either the primary or secondary winding of the transformer. The first and second LC branches are symmetrically arranged with respect to the center inductor L3. Specifically, the first LC branch includes a first inductor L1 and a first capacitor C1, and the second LC branch includes a second inductor L2 and a second capacitor C2. The first inductor L1, the first capacitor C1, the second capacitor C2, and the second inductor L2 are connected in series at one end of the primary winding of the transformer T. One end of the center inductor L3 is connected to the node between the first capacitor C1 and the second capacitor C2, and the other end of the center inductor L3 is connected to the other end of the primary winding of the transformer T.
[0100] Other topologies of the resonant cavity circuit 20 will not be listed here. Their equivalent structures can satisfy the CLLLC type arrangement and ensure that the first LC branch and the second LC branch are symmetrically arranged with respect to the center inductor.
[0101] In some embodiments, the resonant converter can also be a multiphase resonant converter, such as a three-phase resonant converter. The resonant cavity circuit 20 in the multiphase resonant converter can be adjusted according to the topology that meets the requirements described above, which will not be elaborated here.
[0102] For the resonant converter with CLLLC structure in resonant cavity circuit 20, the power control method is the same as that of the resonant converter with CLCLC structure in resonant cavity circuit 20, and will not be repeated here.
[0103] The resonant converter using the CLLLC structure in resonant cavity circuit 20 is based on the above power control method. The constraints for achieving unity power factor for the resonant converter are determined as follows:
[0104] (10)
[0105] According to formula (10), for a resonant converter based on a CLLLC structure, when the components in the first LC branch and the second LC branch are located on the same side of the transformer T (e.g., ...), ... Figure 12 As shown), at this point, the constraint conditions for the resonant converter to achieve unity power factor can be determined as follows: the inductance values in the first LC branch and the second LC branch are equal, the capacitance values in the first LC branch and the second LC branch are equal, and the effective value of the input voltage of the primary inverter circuit is equal to the product of the effective value of the output voltage of the secondary rectifier circuit and the turns ratio of the transformer.
[0106] When the components in the first and second LC branches, as well as the center inductor L3, are located on opposite sides of transformer T, the parameter values of each component in the first and second LC branches, along with the parameter value of the center inductor L3, must first be equivalently converted to the same side of the transformer based on the transformer's turns ratio (e.g., the side with fewer components is equivalently converted to the side with more components) to obtain the corresponding equivalent values. At this point, the constraint condition for the resonant converter to achieve unity power factor can be determined as follows: the equivalent values of the inductors in the first and second LC branches are equal; the equivalent values of the capacitors in the first and second LC branches are equal; and the effective value of the input voltage of the primary-side inverter circuit is equal to the product of the effective value of the output voltage of the secondary-side rectifier circuit and the transformer's turns ratio. For components not involved in the equivalent conversion, their equivalent values are taken as their original values.
[0107] For example, when the second inductor L2 in the second LC branch is located on the secondary winding side of transformer T, while the second capacitor C2 in the second LC branch, the first inductor L1 and first capacitor C1 in the first LC branch, and the center inductor L3 are located on the primary winding side of transformer T, the inductance value of the second inductor L2 needs to be equivalently converted to the primary winding side of transformer T. However, the second capacitor C2 in the second LC branch, the first inductor L1 and first capacitor C1 in the first LC branch, and the center inductor L3 are already on the primary winding side of transformer T; therefore, their parameter values do not need to participate in the equivalent conversion, and the equivalent values of the second capacitor C2, the first inductor L1 and first capacitor C1, and the center inductor L3 are taken as their original values.
[0108] Based on the power control method described above, the determined upper limit for frequency regulation is:
[0109] (11)
[0110] The lower limit for frequency adjustment is:
[0111] (12)
[0112] In the formula, This represents the equivalent inductance of the center inductance. This represents the equivalent capacitance value in the first LC branch and the second LC branch; This represents the equivalent inductance value in the first LC branch and the second LC branch. For components not involved in the equivalent conversion, their equivalent values are taken as their original values.
[0113] Combining formulas (9) and (11), it can be seen that the lower limit of frequency regulation for the CLLLC resonant converter is the same as the upper limit of frequency regulation for the CLLLC resonant converter. This indicates that the operating frequency range of the CLLLC resonant converter is lower, and its corresponding lower limit of frequency regulation is significantly smaller than the upper limit of frequency regulation. Therefore, when performing power regulation, the CLLLC resonant converter can be selected to operate near the lower limit of frequency regulation, working within a smaller frequency range, thereby reducing switching losses and magnetic component losses, and achieving higher efficiency.
[0114] In a second aspect, an embodiment of the present invention provides a resonant converter, which includes a controller, a primary-side inverter circuit, at least one resonant cavity circuit, and a secondary-side rectifier circuit connected in sequence; the primary-side inverter circuit includes multiple switching transistors forming a primary-side full-bridge circuit; the resonant cavity circuit includes a transformer, at least one inductor, and at least one capacitor; the secondary-side rectifier circuit includes multiple switching transistors forming a secondary-side full-bridge circuit; the controller applies the power control method of the resonant converter described in any one of the embodiments of the first aspect.
[0115] In some embodiments, the controller may be a CPU, a general-purpose processor, a DSP, an ASIC, an FPGA, or other programmable logic device, transistor logic device, hardware component, or any combination thereof. It may implement or execute the various exemplary logic blocks, modules, and circuits described in connection with this disclosure. The controller may also be a combination that implements computational functions, such as a combination of one or more microprocessors, a combination of a DSP and a microprocessor, etc.
[0116] In some embodiments, the resonant cavity circuit includes a transformer, a central capacitor, a first LC branch, and a second LC branch. The central capacitor is connected in parallel with the primary or secondary winding of the transformer, and the first and second LC branches are symmetrically arranged with respect to the central capacitor. The specific structure of the resonant cavity circuit is as described above and will not be repeated here.
[0117] In some embodiments, the resonant cavity circuit includes a transformer, a center inductor, a first LC branch, and a second LC branch. The center inductor is connected in parallel with the primary or secondary winding of the transformer, and the first and second LC branches are symmetrically arranged with respect to the center inductor. The specific structure of the resonant cavity circuit is as described above and will not be repeated here.
[0118] The above is a detailed description of the preferred embodiments of the present invention. However, this application is not limited to the above embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of this application. All such equivalent modifications or substitutions are included within the scope defined by the claims of this application.
Claims
1. A power control method of a resonant converter, characterized by, The resonant converter includes a primary-side inverter circuit, at least one resonant cavity circuit, and a secondary-side rectifier circuit connected in sequence; the primary-side inverter circuit includes multiple switching transistors forming a primary-side full-bridge circuit; the resonant cavity circuit includes a transformer, at least one inductor, and at least one capacitor; the secondary-side rectifier circuit includes multiple switching transistors forming a secondary-side full-bridge circuit; the power control method includes the following steps: Based on the circuit equations of the resonant converter, the constraints for achieving unity power factor of the resonant converter are determined, and the constraints include the resonant parameter conditions of the resonant cavity circuit. The frequency adjustment range of the resonant converter is determined based on the aforementioned constraints. Within the frequency adjustment range, power regulation is achieved by adjusting the frequency of the resonant converter.
2. The power control method for the resonant converter according to claim 1, characterized in that, The step of determining the constraint conditions for the resonant converter to achieve unity power factor based on the circuit equations of the resonant converter includes: The expression for the output power of the resonant converter is determined based on the circuit equations. The expression for the input impedance angle corresponding to the resonant converter is determined based on the circuit equation and the expression for the output power. The constraint condition is determined when the input impedance angle is zero.
3. The power control method for the resonant converter according to claim 1, characterized in that, Before determining the constraint conditions for the resonant converter to achieve unity power factor based on the circuit equations of the resonant converter, the power control method further includes: establishing the circuit equations of the resonant converter based on the fundamental wave analysis method, wherein the circuit equations include the expression of the input voltage phasor of the primary-side inverter circuit and the expression of the output voltage phasor of the secondary-side rectifier circuit.
4. The power control method for the resonant converter according to claim 1, characterized in that, The resonant cavity circuit includes a transformer, a central capacitor, a first LC branch, and a second LC branch. The central capacitor is connected in parallel with the primary winding or secondary winding of the transformer. The first LC branch and the second LC branch are symmetrically arranged with respect to the central capacitor. The parameter values of each component in the first LC branch and the second LC branch, as well as the parameter value of the center capacitor, are equivalently converted to the same side of the transformer according to the turns ratio of the transformer to obtain the corresponding equivalent values. The constraints include that the equivalent inductance values in the first LC branch and the second LC branch are equal, the equivalent capacitance values in the first LC branch and the second LC branch are equal, and the effective value of the input voltage of the primary inverter circuit is equal to the product of the effective value of the output voltage of the secondary rectifier circuit and the turns ratio of the transformer.
5. The power control method for the resonant converter according to claim 4, characterized in that, The frequency adjustment range includes an upper limit value and a lower limit value for frequency adjustment; The upper limit value for frequency adjustment is: ； The lower limit value for frequency adjustment is: ； In the formula, This represents the equivalent capacitance value of the central capacitor; This represents the equivalent capacitance value in the first LC branch and the second LC branch; This represents the equivalent inductance value in the first LC branch and the second LC branch.
6. The power control method for the resonant converter according to claim 1, characterized in that, The resonant cavity circuit includes a transformer, a center inductor, a first LC branch, and a second LC branch. The center inductor is connected in parallel with the primary winding or secondary winding of the transformer. The first LC branch and the second LC branch are symmetrically arranged with respect to the center inductor. The parameter values of each component in the first LC branch and the second LC branch, as well as the parameter value of the center inductor, are equivalently converted to the same side of the transformer based on the turns ratio of the transformer to obtain the corresponding equivalent values. The constraints include that the equivalent inductance values in the first LC branch and the second LC branch are equal, the equivalent capacitance values in the first LC branch and the second LC branch are equal, and the effective value of the input voltage of the primary-side inverter circuit is equal to the product of the effective value of the output voltage of the secondary-side rectifier circuit and the turns ratio of the transformer.
7. The power control method for the resonant converter according to claim 6, characterized in that, The frequency adjustment range includes an upper limit value and a lower limit value for frequency adjustment; The upper limit value for frequency adjustment is: ； The lower limit value for frequency adjustment is: ； In the formula, This represents the equivalent inductance value of the central inductor; This represents the equivalent capacitance value in the first LC branch and the second LC branch; This represents the equivalent inductance value in the first LC branch and the second LC branch.
8. A resonant converter, characterized in that, The resonant converter includes a controller, a primary-side inverter circuit, at least one resonant cavity circuit, and a secondary-side rectifier circuit connected in sequence; the primary-side inverter circuit includes multiple switching transistors forming a primary-side full-bridge circuit; the resonant cavity circuit includes a transformer, at least one inductor, and at least one capacitor; the secondary-side rectifier circuit includes multiple switching transistors forming a secondary-side full-bridge circuit; the controller applies the power control method of the resonant converter according to any one of claims 1 to 7.
9. The resonant converter according to claim 8, characterized in that, The resonant cavity circuit includes a transformer, a central capacitor, a first LC branch, and a second LC branch. The central capacitor is connected in parallel with the primary winding or secondary winding of the transformer. The first LC branch and the second LC branch are symmetrically arranged with respect to the central capacitor.
10. The resonant converter according to claim 8, characterized in that, The resonant cavity circuit includes a transformer, a center inductor, a first LC branch, and a second LC branch. The center inductor is connected in parallel with the primary winding or secondary winding of the transformer. The first LC branch and the second LC branch are symmetrically arranged with respect to the center inductor.