A high-frequency LLC power supply and a control method thereof

Abstract

The application is suitable for the technical field of switching power supply, and provides a high-frequency LLC power supply and a control method thereof.The high-frequency LLC power supply comprises a switching network, a resonant network, a high-frequency transformer unit and a rectifier bridge unit.The switching network comprises first to third switching groups and is configured as a three-phase full-bridge switch.The resonant network comprises first to third resonant circuits and is connected with the first to third switching groups in one-to-one correspondence.The high-frequency transformer unit comprises first to third high-frequency transformers, and each high-frequency transformer is connected with the first to third resonant circuits in one-to-one correspondence.The rectifier bridge unit comprises first to third rectifier bridges in parallel connection, and the first to third rectifier bridges are connected with the corresponding secondary side coils of the first to third high-frequency transformers.Compared with the conventional power supply, the high-frequency LLC power supply and the control method thereof do not need a filter inductor on the DC output side, the output ripple frequency is increased to 12 times of the switching frequency, and the ripple amplitude is greatly reduced.

Description

Technical Field

[0001] This application belongs to the field of switching power supply technology, and in particular relates to a high-frequency LLC power supply and its control method. Background Technology

[0002] Plasma spraying is a technique for strengthening and modifying material surfaces using a plasma arc. A plasma arc is a compressed electric arc; compared to a free arc, it has a thinner arc column, higher current density, and higher gas ionization, thus exhibiting characteristics such as high temperature, concentrated energy, and good arc stability. Plasma spraying can impart properties to substrate surfaces such as wear resistance, corrosion resistance, high-temperature oxidation resistance, electrical insulation, heat insulation, radiation protection, friction reduction, and sealing.

[0003] Plasma spraying arcs are highly sensitive to power supply ripple, and ultra-low current ripple is crucial for precision spraying processes. Conventional power supplies reduce ripple by increasing the output filter inductance, but a larger filter inductance reduces the dynamic characteristics of the arc, which is unsuitable for plasma spraying applications. Summary of the Invention

[0004] To overcome the problems existing in related technologies, embodiments of this application provide a high-frequency LLC power supply and its control strategy.

[0005] This application is achieved through the following technical solution:

[0006] In a first aspect, embodiments of this application provide a high-frequency LLC power supply, characterized in that it comprises: a switching network including a first switch group to a third switch group, the first switch group to the third switch group being connected in parallel to form a three-phase full-bridge switch; a resonant network including a first resonant circuit to a third resonant circuit, each connected to the first switch group to the third switch group in a one-to-one correspondence; a high-frequency transformer unit including a first high-frequency transformer to a third high-frequency transformer, each high-frequency transformer including a primary winding and two secondary windings, a first secondary winding and a second secondary winding, the three primary windings being connected to the first resonant circuit to the third resonant circuit in a one-to-one correspondence; and a rectifier bridge unit including a first rectifier bridge to a third rectifier bridge connected in parallel, the first rectifier bridge to the third rectifier bridge being connected to the secondary windings of the corresponding first high-frequency transformer to the third high-frequency transformer in a one-to-one correspondence.

[0007] Based on the first aspect, in some possible implementations, each of the switch groups includes a first switch and a second switch, and the resonant circuit correspondingly connected to the switch group is connected in parallel with the second switch of the switch group.

[0008] Based on the first aspect, in some possible implementations, each of the resonant circuits includes a first capacitor, a first inductor, and the primary side of the corresponding high-frequency transformer connected in sequence, and the signal phase difference between the resonant circuits is 120°.

[0009] Based on the first aspect, in some possible implementations, each of the rectifier bridges includes a first input terminal and a second input terminal, the first input terminal of each rectifier bridge is connected to the first secondary coil of the corresponding high-frequency transformer, and the second input terminal of each rectifier bridge is connected to the second secondary coil of the corresponding high-frequency transformer.

[0010] Based on the first aspect, in some possible implementations, the switch network performs soft switching control, there is no direct connection between the first switch and the second switch of the switch group, the phase difference of the drive signals between the first switch of the first switch group, the first switch of the second switch group and the first switch of the third switch group is 120°, the phase difference of the drive signals between the second switch of the first switch group, the second switch of the second switch group and the second switch of the third switch group is 120°, and the first switch group to the third switch group is driven by an interleaved timing sequence with a phase difference of 120°.

[0011] Based on the first aspect, in some possible implementations, the duty cycle of each drive signal in the interleaved timing drive is the same.

[0012] Based on the first aspect, in some possible implementations, the high-frequency transformer operates in two modes: isolation step-down and isolation step-up. In the isolation step-down mode, the primary windings of the first to third high-frequency transformers are connected in a delta configuration. In the isolation step-up mode, the primary windings of the first to third high-frequency transformers are connected in a star configuration, the first secondary windings of the first to third high-frequency transformers are connected in a delta configuration to form a delta winding, and the second secondary windings of the first to third high-frequency transformers are connected in a star configuration to form a star winding.

[0013] Based on the first aspect, in some possible implementations, the turns ratio of the angular winding to the star winding is 1.732:1.

[0014] Based on the first aspect, in some possible implementations, the first phase of the angle winding and the first phase of the star winding share a first rectifier bridge, the second phase of the angle winding and the second phase of the star winding share a second rectifier bridge, and the third phase of the angle winding and the third phase of the star winding share a third rectifier bridge.

[0015] Secondly, this application provides a high-frequency LLC power supply control method, characterized in that it includes: the power supply described above, which widens the output voltage range through frequency conversion and PWM control, including two working modes: normal heavy load operation and light load operation. In the normal heavy load operation, the power supply operates through frequency conversion; in the light load operation, the switching frequency is increased to the highest frequency through PFM control. If closed-loop control is not completed, PWM control is performed at the highest frequency until closed-loop control is completed.

[0016] Compared with conventional power supplies, the above-mentioned high-frequency LLC power supply and its control method do not require a filter inductor on the DC output side, thus improving the overall efficiency. By using a star / star / delta connected high-frequency transformer, the ripple is superimposed on the star / delta phase shift characteristics of the high-frequency transformer on the basis of three-phase interleaving, increasing the output ripple frequency to 12 times the switching frequency and significantly reducing the amplitude of the ripple.

[0017] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit this specification. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the main circuit topology of a high-frequency LLC power supply provided in an embodiment of this application;

[0020] Figure 2 This is a schematic diagram of the circuit principle of a high-frequency LLC power supply provided in an embodiment of this application;

[0021] Figure 3 This is a timing diagram of the drive signals for a high-frequency LLC power supply provided in an embodiment of this application;

[0022] Figure 4 This is a schematic flowchart of a high-frequency LLC power supply control method provided in an embodiment of this application;

[0023] Figure 5 This is a waveform diagram of the three-phase current on the primary side of the high-frequency transformer of a high-frequency LLC power supply provided in an embodiment of this application;

[0024] Figure 6 This is an output current waveform diagram of a high-frequency LLC power supply provided in an embodiment of this application;

[0025] Figure 7This is an output voltage waveform diagram of a high-frequency LLC power supply provided in an embodiment of this application;

[0026] Figure 8 This is a 100kHz resonant waveform diagram of the high-frequency LLC power supply provided in the embodiments of this application;

[0027] Figure 9 This is an 86kHz resonant waveform diagram of a high-frequency LLC power supply provided in an embodiment of this application. Detailed Implementation

[0028] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0029] It should be understood that, when used in this application specification and the appended claims, the term "comprising" indicates the presence of the described features, integrals, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or a collection thereof.

[0030] It should also be understood that the term “and / or” as used in this application specification and the appended claims means any combination of one or more of the associated listed items and all possible combinations, and includes such combinations.

[0031] As used in this application specification and the appended claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if detected [the described condition or event]" may be interpreted, depending on the context, as meaning "once determined," "in response to determination," "once detected [the described condition or event]," or "in response to detection [the described condition or event]."

[0032] Furthermore, in the description of this application and the appended claims, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0033] References to "one embodiment" or "some embodiments" as described in this specification mean that one or more embodiments of this application include a specific feature, structure, or characteristic described in connection with that embodiment. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including but not limited to," unless otherwise specifically emphasized.

[0034] When faced with situations requiring ultra-low current ripple, existing power supplies often reduce current ripple by increasing the output filter inductance. However, the output ripple frequency of existing power supplies can only be increased to a maximum of 6 times the switching frequency. The large amount of filter inductance reduces the dynamic characteristics of the arc, which is insufficient to meet the requirements of precision spraying processes such as plasma spraying.

[0035] To address the aforementioned problems, this application provides a high-frequency LLC power supply. For the high-frequency LLC power supply in the embodiments of this application, please refer to... Figure 1 The system includes a switching network 100, a resonant network 200, a high-frequency transformer unit 300, and a rectifier bridge unit 400. The switching network 100 includes a first to a third switching group, which are connected in parallel to form a three-phase full-bridge switch. The resonant network 200 includes a first to a third resonant circuit, each connected to one of the first to third switching groups. The high-frequency transformer unit 300 includes a first to a third high-frequency transformer, each transformer including a primary winding and two sets of secondary windings (a first secondary winding and a second secondary winding), with each set of primary windings connected to one of the first to third resonant circuits. The rectifier bridge unit 400 includes a first to a third rectifier bridge connected in parallel, each bridge connected to the secondary winding of its corresponding high-frequency transformer.

[0036] The following combination Figure 1 The high-frequency LLC power supply of this application is described in detail.

[0037] Figure 2 This is a schematic diagram of the circuit principle of a high-frequency LLC power supply provided in an embodiment of this application, with reference to... Figure 2 The following is a detailed description of this high-frequency LLC power supply:

[0038] In some embodiments, see Figure 2The first switch TR1 and the second switch TR2 form the first switching group; the third switch TR3 and the fourth switch TR4 form the second switching group; and the fifth switch TR5 and the sixth switch TR6 form the third switching group. The first resonant circuit is connected to the first switch TR1 and forms a parallel connection with the second switch TR2; the second resonant circuit is connected to the third switch TR3 and forms a parallel connection with the fifth switch TR4; and the third resonant circuit is connected to the fifth switch TR5 and forms a parallel connection with the sixth switch TR6. The switching network uses soft-switching control, and there is no direct connection between the first switch TR1 and the second switch TR2, the third switch TR3 and the fourth switch TR4, and the fifth switch TR5 and the sixth switch TR6.

[0039] In some embodiments, see Figure 2 The first resonant capacitor Cx1, the first resonant inductor Lx1, and the primary winding of the first high-frequency transformer TB1 form the primary A-phase resonant circuit, i.e., the first resonant circuit; the second resonant capacitor Cx2, the second resonant inductor Lx2, and the primary winding of the second high-frequency transformer TB2 form the primary B-phase resonant circuit, i.e., the second resonant circuit; the third resonant capacitor Cx3, the resonant inductor Lx3, and the primary winding of the third high-frequency transformer TB3 form the primary C-phase resonant circuit, i.e., the third resonant circuit.

[0040] The signal phase difference between the primary A-phase resonant circuit, the primary B-phase resonant circuit, and the primary C-phase resonant circuit is 120°.

[0041] In some embodiments, see Figure 2 The first secondary coil A1 of the first high-frequency transformer TB1 is connected to the first input terminal of the first rectifier bridge D1, and the second secondary coil A2 is connected to the second input terminal of the first rectifier bridge D1; the first secondary coil B2 of the second high-frequency transformer TB2 is connected to the first input terminal of the second rectifier bridge D2, and the second secondary coil B2 is connected to the second input terminal of the second rectifier bridge D2; the first secondary coil C1 of the third high-frequency transformer TB3 is connected to the first input terminal of the third rectifier bridge D3, and the second secondary coil C2 is connected to the second input terminal of the third rectifier bridge D3.

[0042] In some embodiments, see Figure 2The high-frequency transformers operate in two modes: isolation step-down and isolation step-up. In isolation step-down mode, the primary windings A, B, and C of the first high-frequency transformer TB1, the second high-frequency transformer TB2, and the third high-frequency transformer TB2 are connected in a delta configuration. In isolation step-up mode, the primary windings A, B, and C of the first high-frequency transformer TB1, the second high-frequency transformer TB2, and the third high-frequency transformer TB3 are connected in a star configuration. The primary secondary windings A1, B1, and C1 of the first high-frequency transformer TB1, the second high-frequency transformer TB2, and the third high-frequency transformer TB3 are connected in a delta configuration to form a delta winding, and the primary secondary windings A2, B2, and C2 of the first high-frequency transformer TB1, the second high-frequency transformer TB2, and the third high-frequency transformer TB3 are connected in a star configuration to form a star winding.

[0043] Optionally, the turns ratio of the angle winding to the star winding is 1.732:1.

[0044] Optionally, the A phase of the delta winding and the star winding share the first rectifier bridge D1, the B phase of the delta winding and the star winding share the second rectifier bridge D2, and the C phase of the delta winding and the star winding share the third rectifier bridge D3.

[0045] In some embodiments, see Figure 3 The phase difference between the drive signals Q1, Q3 and Q5 between TR1, TR3 and TR5 is 120°, and the phase difference between the drive signals Q2, Q4 and Q6 between TR2, TR4 and TR6 is 120°. The switches TR1 to TR6 in the switching network are driven by the drive signals Q1 to Q6 in an interleaved timing sequence of 120°. The duty cycle of each drive signal Q1 to Q6 in the interleaved timing drive is the same, which is 0.48.

[0046] Based on the above-mentioned high-frequency LLC power supply, this application embodiment also provides a high-frequency LLC power supply control method.

[0047] See Figure 4 In some embodiments, based on Figure 2 The embodiment shown above, the high-frequency LLC power supply control method may include: widening the output voltage range through frequency conversion and PWM control, including two working modes: normal heavy load operation and light load operation. During normal heavy load operation, the power supply operates through frequency conversion; during light load operation, the switching frequency is increased to the highest frequency through PFM control. If closed-loop control is not completed at this time, PWM control is performed at the highest frequency until closed-loop control is completed.

[0048] Optionally, during normal heavy-load operation, by using a frequency converter, the power supply frequency is further adjusted by regulating the duty cycle during startup; and the duty cycle is adjusted by regulating the frequency during shutdown. The frequency range of the power supply is f. min -fmax f min It is 0.8 times the resonant frequency, f max It is 1.5 times the resonant frequency. The resonant frequency is achieved through... Calculate Lx and Cx, which are the resonant inductance and capacitance in the circuit diagram, respectively.

[0049] Optionally, during light-load operation, the switching frequency can be increased to f by adjusting the duty cycle of the power-on signal and controlling the PWM soft-start switch. max After a soft start, it switches to PFM control for closed-loop control.

[0050] In some embodiments, based on Figure 2 The embodiment shown illustrates the three-phase current waveforms of phases A, B, and C on the primary side of the high-frequency transformer in a high-frequency LLC power supply, as follows: Figure 5 As shown, the output current waveform and the current waveforms of the star winding and delta winding of the high-frequency LLC power supply are as follows: Figure 6 As shown, the output voltage waveform of the high-frequency LLC power supply is as follows: Figure 7 As shown.

[0051] In some embodiments, based on Figure 2 In the embodiment shown, the 100kHz resonant waveform of the high-frequency LLC power supply is as follows: Figure 8 As shown, the 86kHz resonant waveform of the high-frequency LLC power supply is as follows: Figure 9 As shown.

[0052] Compared with conventional power supplies, the above-mentioned high-frequency LLC power supply and its control method do not require a filter inductor on the DC output side, thus improving the overall efficiency. By using a star / star / delta connected high-frequency transformer, the ripple is superimposed on the star / delta phase shift characteristics of the high-frequency transformer on the basis of three-phase interleaving, increasing the output ripple frequency to 12 times the switching frequency and significantly reducing the amplitude of the ripple.

[0053] It should be understood that the sequence number of each step in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0054] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the above-described division of functional units and modules is merely an example. In practical applications, the above functions can be assigned to different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above. The functional units and modules in the embodiments can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit. Furthermore, the specific names of the functional units and modules are only for easy differentiation and are not intended to limit the scope of protection of this application. The specific working process of the units and modules in the above system can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0055] In the above embodiments, the descriptions of each embodiment have different focuses. For parts that are not described in detail or recorded in a certain embodiment, please refer to the relevant descriptions of other embodiments.

[0056] Those skilled in the art will recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0057] In the embodiments provided in this application, it should be understood that the disclosed apparatus / network devices and methods can be implemented in other ways. For example, the apparatus / network device embodiments described above are merely illustrative. For instance, the division of modules or units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between devices or units may be electrical, mechanical, or other forms.

[0058] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0059] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A high-frequency LLC power supply, characterized in that, include: The switching network includes a first switch group to a third switch group, which are connected in parallel to form a three-phase full-bridge switch. The resonant network includes a first resonant circuit to a third resonant circuit, which are respectively connected to the first switch group to the third switch group; The high-frequency transformer unit includes a first high-frequency transformer to a third high-frequency transformer. Each of the high-frequency transformers includes a set of primary windings and two sets of secondary windings, namely a first secondary winding and a second secondary winding. The three sets of primary windings are respectively connected to the first resonant circuit to the third resonant circuit. The rectifier bridge unit includes a first rectifier bridge to a third rectifier bridge connected in parallel, and the first rectifier bridge to the third rectifier bridge are respectively connected to the secondary coils of the corresponding first high-frequency transformer to the third high-frequency transformer. Each of the aforementioned switch groups includes a first switch and a second switch. The resonant circuit corresponding to the switch group is connected in parallel with the second switch of the switch group. The switch network performs soft switching control. There is no direct connection between the first switch and the second switch of the switch group. The phase difference of the driving signals between the first switch of the first switch group, the first switch of the second switch group, and the first switch of the third switch group is 120°. The phase difference of the driving signals between the second switch of the first switch group, the second switch of the second switch group, and the second switch of the third switch group is 120°. The first switch group to the third switch group is driven by an interleaved timing sequence with a phase difference of 120°. The high-frequency transformer operates in two modes: isolation step-down and isolation step-up. In isolation step-down mode, the primary windings of the first to third high-frequency transformers are connected in a delta configuration. In isolation step-up mode, the primary windings of the first to third high-frequency transformers are connected in a star configuration. The first secondary windings of the first to third high-frequency transformers are connected in a delta configuration to form a delta winding, and the second secondary windings of the first to third high-frequency transformers are connected in a star configuration to form a star winding. The turns ratio of the delta winding to the star winding is 1.732:

1. The first phases of the delta winding and the star winding share a first rectifier bridge, the second phases of the delta winding and the star winding share a second rectifier bridge, and the third phases of the delta winding and the star winding share a third rectifier bridge. The first resonant capacitor, the first resonant inductor, and the primary winding of the first high-frequency transformer form a primary phase resonant circuit, i.e., the first resonant circuit; the second resonant capacitor, the second resonant inductor, and the primary winding of the second high-frequency transformer form a primary phase resonant circuit, i.e., the second resonant circuit; the third resonant capacitor, the resonant inductor, and the primary winding of the third high-frequency transformer form a primary phase resonant circuit, i.e., the third resonant circuit.

2. The high-frequency LLC power supply as described in claim 1, characterized in that, Each of the resonant circuits includes a first capacitor, a first inductor, and the primary side of the corresponding high-frequency transformer connected in sequence, and the signal phase difference between the resonant circuits is 120°.

3. The high-frequency LLC power supply as described in claim 1, characterized in that, Each rectifier bridge includes a first input terminal and a second input terminal. The first input terminal of each rectifier bridge is connected to the first secondary coil of the corresponding high-frequency transformer, and the second input terminal of each rectifier bridge is connected to the second secondary coil of the corresponding high-frequency transformer.

4. The high-frequency LLC power supply as described in claim 3, characterized in that, The duty cycle of each drive signal in the interleaved timing drive is the same.

5. A high-frequency LLC power supply control method, characterized in that, include: The power supply as described in any one of claims 1 to 4, through frequency conversion and PWM control, widens the output voltage range, including two operating modes: normal heavy load operation and light load operation. During normal heavy-load operation, the power supply operates in frequency conversion mode. When operating under light load, the switching frequency is increased to the maximum frequency through PFM control. If closed-loop control is not completed, PWM control is performed at the maximum frequency until closed-loop control is completed.

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