A phase-shift control compensation method
By introducing a calculation logic inversely proportional to sinθ into the compensation network of the LLC converter, the problem of large open-loop gain variation in phase-shifting mode is solved, and a more stable closed-loop control effect is achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- UNITED AUTOMOTIVE ELECTRONICS SYST
- Filing Date
- 2023-01-28
- Publication Date
- 2026-06-12
Smart Images
Figure CN116111845B_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of control technology, specifically to a phase-shift control compensation method. Background Technology
[0002] LLC (Limited-Loop) is a widely used power electronic topology with significant efficiency advantages in medium-to-high power applications. LLC achieves output voltage / power regulation based on frequency modulation, reaching optimal efficiency when operating near the resonant point. However, in practical applications, loads are generally not fixed. For example, with battery loads, a voltage range of 2 to 2.5 times the load voltage is common, and the load power needs to cover from no-load to full-load. This wide load range results in a wide operating frequency for the LLC converter, making it difficult for the LLC topology to achieve efficiency under both high-voltage and low-voltage conditions. Therefore, phase-shifting mode is introduced into LLC converters to handle low-voltage output conditions in wide-voltage applications. When the load voltage drops to a set value, the LLC operates at a fixed frequency, adjusting the phase shift angle of the primary-side switch to regulate voltage / power.
[0003] However, in phase-shifted mode, the transfer function gain of the power stage varies significantly with different phase-shift angles. If a fixed compensation function is used, the open-loop gain of the system will vary greatly over a wide phase-shift angle range. This problem poses a significant challenge to compensation design and may even lead to instability in the closed-loop operation of the system. Summary of the Invention
[0004] This application provides a phase-shift control compensation method that can solve the problem of unstable closed-loop operation of the system in related technologies.
[0005] This application provides a phase-shift control compensation method, which adopts the following technical solution:
[0006] A phase-shift control compensation method, comprising:
[0007] A closed-loop control system in LLC phase-shift mode is provided. The closed-loop control system includes a compensation network G_comp(s), a power circuit equivalent transfer function G_power(s), and a feedback network H(s). The three together constitute the open-loop gain of the closed-loop control system. The power circuit equivalent transfer function G_power(s) is a function proportional to sinθ, where θ is the phase shift angle.
[0008] In the compensation network G_comp(s), a calculation logic inversely proportional to sin φ is introduced to eliminate the influence of the phase shift angle φ on the open-loop gain of the system.
[0009] The expression for the equivalent transfer function of the power circuit is as follows: ;
[0010] Wherein, G_LLC(𝜃) is the power converter gain in phase-shift mode, expressed as: ;
[0011] The This is the gain of the LLC when it is operating in frequency modulation mode.
[0012] In some embodiments, the ;
[0013] in, , , , , ;
[0014] Lr is the resonant inductance, Cr is the resonant capacitance, Lm is the transformer magnetizing inductance, RL is the output-side equivalent load, n is the transformer turns ratio, and fs is the switching frequency.
[0015] In some embodiments, the phase shift angle t_ps is the phase shift time, and T is the switching period.
[0016] In some embodiments, the calculation logic is 1 / sinφ.
[0017] In some embodiments, the calculation logic has a limit, which is a positive integer. When the actual value of the calculation logic is greater than or equal to the limit, the value of the calculation logic is defined as the limit.
[0018] In some embodiments, the feedback network H(s) has a fixed feedback ratio.
[0019] In some embodiments, the method can also be applied to other resonant converters operating in phase-shifting mode.
[0020] The technical solution of this application has at least the following advantages:
[0021] 1. By introducing a calculation logic inversely proportional to sin φ into the compensation network G_comp(s), the influence of sin φ on the open-loop gain of the system can be eliminated, thereby achieving better closed-loop control performance compared to existing technologies. Attached Figure Description
[0022] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0023] Figure 1 This is a circuit diagram showing the introduction of phase-shifting mode into LLC converters in wide-voltage applications, a common feature in existing technologies.
[0024] Figure 2 It is in frequency modulation mode and phase shift mode. Figure 1 The waveform of the input voltage to the resonant cavity of the circuit;
[0025] Figure 3 This is a schematic diagram of a closed-loop control system in LLC phase-shifting mode;
[0026] Figure 4 This is a flowchart of a phase-shift control compensation method provided in an exemplary embodiment of this application. Detailed Implementation
[0027] The technical solutions of this application will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.
[0028] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0029] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components; and they can refer to a wireless connection or a wired connection. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.
[0030] Furthermore, the technical features involved in the different embodiments of this application described below can be combined with each other as long as they do not conflict with each other.
[0031] refer to Figure 1It shows the circuit where phase-shifting mode is introduced into LLC converters in common wide voltage applications, where the potential difference between points A and B is the input voltage of the resonant cavity.
[0032] Reference Figure 2 The figures show the waveforms of the resonant cavity input voltage in frequency modulation mode and phase-shifting mode, respectively. The former represents frequency modulation mode, and the latter represents phase-shifting mode. In LLC phase-shifting mode, the waveform is affected by the phase shift angle φ.
[0033] Then, the gain of LLC in phase-shifting mode was analyzed using the fundamental frequency analysis method, and the gain was obtained as follows:
[0034] ;
[0035] in, , , , , .
[0036] Where Lr is the resonant inductance, Cr is the resonant capacitance, Lm is the transformer magnetizing inductance, RL is the equivalent load on the output side, n is the transformer turns ratio, and fs is the switching frequency.
[0037] After that, Figure 2 By performing Fourier decomposition on the two input voltages of the resonant cavity, the fundamental peak value in frequency modulation mode can be obtained as follows: The fundamental peak value in frequency modulation phase shift mode is .in, It refers to the input voltage of the resonant cavity, and 𝜃∈[0°, 180°].
[0038] As can be seen, when entering phase-shift mode, the power converter gain will become an expression related to the phase shift angle φ:
[0039] ;
[0040] Reference Figure 3 The diagram shows a simplified closed-loop control system in LLC phase-shift mode. Since the switching frequency fs has reached its maximum, the control variable changes from fs to the phase shift angle φ. Here, G_comp(s) is the compensation network, G_power(s) is the equivalent transfer function of the power circuit, and H(s) is the feedback network. G_comp(s), G_power(s), and H(s) together constitute the system open-loop gain.
[0041] Among them, the power circuit equivalent transfer function ;
[0042] Let fs and RL be constants, then It is also a constant. However, sinφ is a variable related to the phase shift angle φ, and when φ changes from 0° to 90° to 180°, sinφ changes from 0° to 1° to 0°. Therefore, in phase-shift mode, the equivalent transfer function G_power(s) of the power circuit changes by a large factor. If the compensation network uses a fixed function, the open-loop gain of the system changes greatly in the wide phase shift angle range.
[0043] For the reasons mentioned above, this application provides a phase-shift control compensation method, which mainly adopts the following technical solution:
[0044] S1: Provides a closed-loop control system in LLC phase-shifting mode as described above.
[0045] For example, this method can be mainly applied to LLC circuits in the phase-shifting mode described above. For such circuits, the closed-loop control system includes a compensation network G_comp(s), a power circuit equivalent transfer function G_power(s), and a feedback network H(s). The feedback ratio of the feedback network H(s) is a fixed value.
[0046] S2: Introduce a calculation logic inversely proportional to sinφ in the compensation network G_comp(s) to improve the stability of the system's open-loop gain over the full phase shift range.
[0047] In digital systems, the phase shift angle φ is a readily identifiable physical quantity. Where t_ps is the phase shift time and T is the switching period. Therefore, this method places very little burden on computation and control.
[0048] For example, by introducing calculation logic related to the phase shift angle φ into the compensation network G_comp(s), the DC gain of G_comp(s) * G_power(s) is made relatively stable, and the system open-loop gain becomes only equal to the sum of the phase shift angle φ and the phase shift angle φ. The relevant constants can be used to eliminate the influence of the phase shift angle φ on system stability.
[0049] Optionally, in some embodiments, the calculation logic can be 1 / sinφ, which can be combined with... They cancel each other out, thus eliminating the effect of the phase shift angle φ.
[0050] Furthermore, in some embodiments, since 1 / sinθ is approximately infinite when θ is approximately equal to 0° or 180°, for practical applications, 1 / sinθ can be limited so that it actually reaches its maximum value. Taking a limit of 5 as an example, when the actual value of 1 / sinθ is greater than or equal to 5, the value of 1 / sinθ can be defined as 5 during calculation.
[0051] Furthermore, the phase-shift control compensation method described above can also be applied to other resonant converters operating in phase-shift mode, such as CLLC and CLLLC.
[0052] The phase-shift control compensation method disclosed in this application can eliminate the influence of sin𝜃, i.e., the phase-shift angle𝜃, on the open-loop gain of the system by introducing a calculation logic inversely proportional to sin𝜃 into the compensation network G_comp(s), thereby achieving better closed-loop control performance compared to the prior art.
[0053] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this application.
Claims
1. A phase-shift control compensation method, characterized in that, include: A closed-loop control system in LLC phase-shift mode is provided. The closed-loop control system includes a compensation network G_comp(s), a power circuit equivalent transfer function G_power(s), and a feedback network H(s). The three together constitute the open-loop gain of the closed-loop control system. The power circuit equivalent transfer function G_power(s) is a function proportional to sinθ, where θ is the phase shift angle. In the compensation network G_comp(s), a calculation logic inversely proportional to sin φ is introduced to eliminate the influence of the phase shift angle φ on the open-loop gain of the system. The expression for the equivalent transfer function of the power circuit is as follows: ; Wherein, G_LLC(𝜃) is the power converter gain in phase-shift mode, expressed as: ; The This is the gain of the LLC when it is operating in frequency modulation mode.
2. The method according to claim 1, characterized in that, The ; in, , , , , ; Lr is the resonant inductance, Cr is the resonant capacitance, Lm is the transformer magnetizing inductance, RL is the output-side equivalent load, n is the transformer turns ratio, and fs is the switching frequency.
3. The method according to claim 1, characterized in that, The phase shift angle t_ps is the phase shift time, and T is the switching period.
4. The method according to claim 1, characterized in that, The calculation logic is 1 / sin𝜃.
5. The method according to claim 1, characterized in that, The calculation logic has a limit, which is a positive integer. When the actual value of the calculation logic is greater than or equal to the limit, the value of the calculation logic is defined as the limit.
6. The method according to claim 1, characterized in that, The feedback network H(s) has a fixed feedback ratio.
7. The method according to claim 1, characterized in that, The method can also be applied to other resonant converters operating in phase-shifting mode.