Phase shift control method and DC / DC converter

Abstract

The invention discloses a phase shift control method of a DC / DC converter. The phase shift control method comprises the following steps: judging a working mode of the DC / DC converter; when the DC / DC converter is in a boost mode and the output power is smaller than a first power value, setting the switching frequency of the DC / DC converter as a first preset frequency, controlling the second switching bridge arm to lag behind the first dynamic phase of the first switching bridge arm, and controlling the third switching bridge arm to advance the first preset phase of the first switching bridge arm, controlling the fourth switch bridge arm to lag behind the first switch bridge arm by a second preset phase, wherein the first dynamic phase is in negative correlation with the output power; and when the DC / DC converter is in the boost mode and the output power is greater than a second power value, setting the switching frequency of the DC / DC converter to be in negative correlation with the output power, and controlling the fourth switching bridge arm to lag behind the first switching bridge arm at a third preset phase, the second power value being greater than the first power value.

Description

Technical Field

[0001] The present invention relates to a phase shift control method and a DC / DC converter, and in particular to a phase shift control method and a DC / DC converter for reducing light-load ripple. Background Art

[0002] Converters with a wide output voltage range based on an LLC resonant topology employ pulse frequency modulation (PFM) control. Due to frequency range limitations, high power output is still possible when the switching frequency reaches its highest point (i.e., the gain is lowest).

[0003] Under light load conditions, a specific control method is required to meet output gain while outputting a lower power. The conventional control method for this requirement is burst mode control. However, burst mode produces significant output ripple, which may not meet user needs.

[0004] Therefore, how to design a phase shift control method and a DC / DC converter to solve the problems and technical bottlenecks in the prior art is an important topic studied by the inventors of the present disclosure. Summary of the Invention

[0005] An object of the present invention is to provide a phase shift control method for a DC / DC converter to solve the problems of the prior art.

[0006] The present invention provides a phase shift control method for a DC / DC converter, wherein the DC / DC converter includes a primary circuit, a secondary circuit, and a resonant cavity disposed between the primary and secondary circuits, wherein the primary circuit includes a first switching arm and a second switching arm, and the secondary circuit includes a third switching arm and a fourth switching arm. The phase shift control method includes: determining an operating mode of the DC / DC converter; when the DC / DC converter is in boost mode and the output power is less than a first power value, setting the switching frequency of the DC / DC converter to a first preset frequency, controlling the second switching arm to lag behind the first switching arm by a first dynamic phase, controlling the third switching arm to lead the first switching arm by a first preset phase, and controlling the fourth switching arm to lag behind the first switching arm by a second preset phase, wherein the first dynamic phase is negatively correlated with the output power; and when the DC / DC converter is in boost mode and the output power is greater than a second power value, setting the switching frequency of the DC / DC converter to be negatively correlated with the output power, controlling the fourth switching arm to lag behind the first switching arm by a third preset phase, wherein the second power value is greater than the first power value.

[0007] In one embodiment, setting the first dynamic phase to be negatively correlated with the output power includes: controlling the first dynamic phase to gradually decrease to 0 as the output power increases, and controlling the first dynamic phase to gradually increase from 0 as the output power decreases.

[0008] In one embodiment, setting the switching frequency of the DC / DC converter to be negatively correlated with the output power includes: controlling the switching frequency of the DC / DC converter to gradually decrease from a second preset frequency as the output power increases, and controlling the switching frequency of the DC / DC converter to gradually increase to the second preset frequency as the output power decreases, wherein the second preset frequency is greater than the first preset frequency.

[0009] In one embodiment, the first switch bridge arm includes a first upper switch and a first lower switch connected in series, the second switch bridge arm includes a second upper switch and a second lower switch connected in series, the third switch bridge arm includes a third upper switch and a third lower switch connected in series, and the fourth switch bridge arm includes a fourth upper switch and a fourth lower switch connected in series, and the first upper switch and the first lower switch are complementary to each other, wherein: controlling the second switch bridge arm to lag behind the first switch bridge arm by a first dynamic phase includes: controlling the second upper switch of the second switch bridge arm to lag behind the first lower switch of the first switch bridge arm by a first dynamic phase, and controlling the second lower switch of the second switch bridge arm to lag behind the first upper switch of the first switch bridge arm by a first dynamic phase; controlling the third switch bridge arm to advance ahead of the first switch bridge arm by a first preset phase includes: controlling the third upper switch of the third switch bridge arm to advance ahead of the first upper switch of the first switch bridge arm by a first preset phase, and controlling the third lower switch of the third switch bridge arm to advance ahead of the first lower switch of the first switch bridge arm by a first preset phase. Controlling the fourth switch bridge arm to lag behind the second preset phase of the first switch bridge arm includes controlling the four upper switches of the fourth switch bridge arm to lag behind the first lower switch of the first switch bridge arm by the second preset phase, and controlling the four lower switches of the fourth switch bridge arm to lag behind the first upper switch of the first switch bridge arm by the second preset phase; controlling the fourth switch bridge arm to lag behind the third preset phase of the first switch bridge arm includes controlling the four upper switches of the fourth switch bridge arm to lag behind the first lower switch of the first switch bridge arm by the third preset phase, and controlling the four lower switches of the fourth switch bridge arm to lag behind the first upper switch of the first switch bridge arm by the third preset phase.

[0010] In one embodiment, when the output power of the DC / DC converter increases from a first power value to a second power value, the phase angle at which the fourth switching bridge arm lags behind the first switching bridge arm is controlled to gradually increase from a second preset phase to a fourth preset phase, the switching frequency of the DC / DC converter is controlled to be a first preset frequency, and the third switching bridge arm is controlled to lead the first switching bridge arm by a first preset phase.

[0011] In one embodiment, when the output power of the DC / DC converter gradually increases and becomes equal to a second power value, the phase angle at which the fourth switching bridge arm lags behind the first switching bridge arm is controlled to be adjusted from a fourth preset phase to a third preset phase, the switching frequency of the DC / DC converter is controlled to be adjusted from the first preset frequency to the second preset frequency, the phase angle at which the third switching bridge arm leads the first switching bridge arm is controlled to linearly decrease from the first preset phase to 0, and the rate of change of the phase angle at which the fourth switching bridge arm lags behind the first switching bridge arm is controlled to be greater than the rate of change of the switching frequency of the DC / DC converter.

[0012] In one embodiment, when the output power of the DC / DC converter decreases from the second power value to the first power value, the phase angle at which the fourth switching bridge arm lags behind the first switching bridge arm is controlled to gradually decrease from a fourth preset phase to a second preset phase, the switching frequency of the DC / DC converter is controlled to be the first preset frequency, and the third switching bridge arm is controlled to lead the first switching bridge arm by the first preset phase.

[0013] In one embodiment, when the output power of the DC / DC converter gradually decreases and becomes equal to a second power value, the phase angle at which the fourth switching bridge arm lags behind the first switching bridge arm is controlled to decrease from a third preset phase to a fourth preset phase, the switching frequency of the DC / DC converter is controlled to decrease from the second preset frequency to the first preset frequency, the phase angle at which the third switching bridge arm leads the first switching bridge arm is controlled to linearly increase from 0 to the first preset phase, and the rate of change of the phase angle at which the fourth switching bridge arm lags behind the first switching bridge arm is controlled to be less than or equal to the switching frequency of the DC / DC converter.

[0014] In one embodiment, the first preset frequency, the second preset frequency, the first preset phase, the second preset phase, the third preset phase, the fourth preset phase, and the first dynamic phase are determined based on the output power of the DC / DC converter, the first power value and the second power value are determined based on the output voltage of the DC / DC converter, and the second preset frequency is less than or equal to the maximum frequency limit of the DC / DC converter.

[0015] In one embodiment, the phase shift control method further includes: when the DC / DC converter is in step-down mode and the output power is less than a third power value, setting the switching frequency of the DC / DC converter to a third preset frequency, controlling the second switching bridge arm to lag behind the first switching bridge arm by a second dynamic phase, wherein the second dynamic phase is negatively correlated with the output power; and when the DC / DC converter is in step-down mode and the output power is greater than the third power value, setting the switching frequency of the DC / DC converter to be negatively correlated with the output power.

[0016] In one embodiment, setting the second dynamic phase to be negatively correlated with the output power includes: controlling the second dynamic phase to gradually decrease to a fifth preset phase as the output power increases, and controlling the second dynamic phase to gradually increase from the fifth preset phase as the output power decreases, wherein the fifth preset phase is not 0.

[0017] In one embodiment, setting the switching frequency of the DC / DC converter to be negatively correlated with the output power includes: controlling the switching frequency of the DC / DC converter to gradually decrease as the output power increases, and controlling the switching frequency of the DC / DC converter to gradually increase as the output power decreases.

[0018] In one embodiment, when the output power of the DC / DC converter gradually increases and becomes equal to a third power value, the switching frequency of the DC / DC converter is controlled to increase from the third preset frequency to a fourth preset frequency as the second dynamic phase decreases to 0, and then the switching frequency of the DC / DC converter is controlled to gradually decrease from the fourth preset frequency.

[0019] In one embodiment, when the output power of the DC / DC converter gradually decreases and becomes equal to a third power value, the switching frequency of the DC / DC converter is controlled to gradually increase to a fourth preset frequency, and then the switching frequency of the DC / DC converter is controlled to decrease from the fourth preset frequency to the third preset frequency as the second dynamic phase increases from 0.

[0020] In one embodiment, the third power value is determined according to the output voltage of the DC / DC converter, the third preset frequency, the fourth preset frequency, and the fifth preset phase are determined according to the output power of the DC / DC converter, and the fourth preset frequency is less than or equal to the maximum frequency limit of the DC / DC converter.

[0021] In one embodiment, when the DC / DC converter is in a boost mode, a value corresponding to the second power value when the output power gradually increases is equal to the sum of the value corresponding to the second power value when the output power gradually decreases and the buffer power; and / or, when the DC / DC converter is in a buck mode, a value corresponding to the third power value when the output power gradually increases is equal to the sum of the value corresponding to the third power value when the output power gradually decreases and the buffer power.

[0022] In one embodiment, the resonant cavity includes a transformer, the first switch bridge arm includes a first upper switch and a first lower switch connected in series, the second switch bridge arm includes a second upper switch and a second lower switch connected in series, the third switch bridge arm includes a third upper switch and a third lower switch connected in series, and the fourth switch bridge arm includes a fourth upper switch and a fourth lower switch connected in series, wherein the connection midpoint of the first switch bridge arm and the connection midpoint of the second switch bridge arm are correspondingly connected to the two terminal points of the primary winding of the transformer, and the connection midpoint of the third switch bridge arm and the connection midpoint of the fourth switch bridge arm are correspondingly connected to the two terminal points of the primary winding of the transformer.

[0023] In one embodiment, the DC / DC converter is a bidirectional converter; and / or the resonant cavity is an LLC resonant cavity or a CLLC resonant cavity.

[0024] Another object of the present invention is to provide a DC / DC converter that addresses the problems of the prior art. The DC / DC converter proposed in the present invention includes a primary circuit, a secondary circuit, a resonant cavity, and a control unit. The control unit executes the aforementioned phase shift control method.

[0025] The proposed phase-shift control method and DC / DC converter vary the gain of DC / DC converter 100 by combining phase shifting with a frequency modulation control strategy. This phase-shift control method prevents the DC / DC converter (e.g., LLC circuit, CLLC circuit, etc.) from entering burst mode under light load conditions, enabling it to operate in continuous mode. This resolves the issue of excessive output ripple caused by burst mode. Furthermore, this phase-shift control method also maintains light-load efficiency.

[0026] In order to further understand the technologies, means and technical effects adopted by the present invention to achieve the intended objectives, please refer to the following detailed description of the present invention and the accompanying drawings. It is believed that the objectives, features and characteristics of the present invention can be understood in depth and in detail. However, the accompanying drawings are provided for reference and illustration only and are not intended to limit the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 : This is the circuit diagram of the DC / DC converter.

[0028] Figure 2 : A schematic diagram of the control signal for phase shift control of the present invention.

[0029] Figure 3 : This is a flow chart of the phase shift control method of the present invention for determining whether the DC / DC converter is in the boost mode.

[0030] Figure 4 : This is a flow chart of the phase shift control method of the present invention for determining whether the DC / DC converter is in the buck mode.

[0031] Figure 5 : A schematic diagram of phase shift control for power increase when the DC / DC converter of the present invention is in boost mode.

[0032] Figure 6 : is a schematic diagram of phase shift control for power reduction when the DC / DC converter of the present invention is in boost mode.

[0033] Figure 7 : A schematic diagram of phase shift control for power increase when the DC / DC converter of the present invention is in step-down mode.

[0034] Figure 8 : is a schematic diagram of phase shift control for power reduction when the DC / DC converter of the present invention is in step-down mode.

[0035] Figure 9 : A schematic diagram of the phase shift control of the switching point (second power value) when the DC / DC converter of the present invention is in the boost mode and the output power increases.

[0036] Figure 10 : A schematic diagram of the phase shift control of the switching point (second power value) when the DC / DC converter of the present invention is in the boost mode and the output power is reduced.

[0037] Figure 11 : A schematic diagram of the phase shift control of the switching point (third power value) when the DC / DC converter of the present invention is in the step-down mode.

[0038] Description of reference numerals:

[0039] 100: DC / DC converter;

[0040] 10: Primary circuit;

[0041] 20: Secondary circuit;

[0042] 30: resonant cavity;

[0043] 11: first switch bridge arm;

[0044] 12: second switch bridge arm;

[0045] 21: the third switch bridge arm;

[0046] 22: fourth switch bridge arm;

[0047] TR: transformer;

[0048] Cr1: first resonant capacitor;

[0049] Cr2: second resonant capacitor;

[0050] Lr: resonant inductance;

[0051] Q1: first upper switch;

[0052] Q2: second upper switch;

[0053] Q3: First switch;

[0054] Q4: Second switch;

[0055] Q5: The third upper switch;

[0056] Q6: Fourth upper switch;

[0057] Q7: The third switch;

[0058] Q8: The fourth switch;

[0059] N1~N4: connecting midpoints;

[0060] Cin: input capacitance unit;

[0061] Cout: output capacitor unit;

[0062] Vin: input voltage;

[0063] Vo: output voltage;

[0064] P21: first dynamic phase;

[0065] P22: second dynamic phase;

[0066] P11: first preset phase;

[0067] P12: second preset phase;

[0068] P13: third preset phase;

[0069] P14: fourth preset phase;

[0070] P15: fifth preset phase;

[0071] Fs: switching frequency;

[0072] F1: first preset frequency;

[0073] F2: Second preset frequency;

[0074] F3: The third preset frequency;

[0075] F4: The fourth preset frequency;

[0076] Fmax: maximum frequency limit;

[0077] PW1: first power value;

[0078] PW2: second power value;

[0079] PW3: third power value;

[0080] S10-S30: steps;

[0081] S21-S24: steps;

[0082] S31~S34: steps. DETAILED DESCRIPTION

[0083] Some typical embodiments that embody the characteristics and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various changes in different ways, which do not depart from the scope of the present invention, and the description and drawings therein are essentially for illustrative purposes, rather than for limiting the present invention. For example, if the following content of the present invention describes that a first feature is set on or above a second feature, it means that it includes an embodiment in which the first feature and the second feature are in direct contact, and also includes an embodiment in which additional features can be set between the first feature and the second feature, so that the first feature and the second feature may not be in direct contact. In addition, different embodiments of the present invention may use repeated reference symbols and / or marks. These repetitions are for the purpose of simplicity and clarity, and are not used to limit the relationship between the various embodiments and / or the described appearance structures.

[0084] Furthermore, to facilitate descriptions of the relationship between a component or feature and another (plural) component or (plural) feature in the drawings, spatially relative terms such as "upper," "lower," "top," "bottom," and similar terms may be used. Spatially relative terms are used to cover different orientations of the device in use or operation in addition to the orientations depicted in the drawings. The device may also be positioned otherwise (e.g., rotated 90 degrees or in other orientations), and the descriptions of the spatially relative terms used interpreted accordingly. In addition, when a component is referred to as being "connected to" or "coupled to" another component, it may be directly connected to or coupled to the other component, or there may be intervening components. Although the numerical ranges and parameters of the broad scope of the present invention are approximate, the numerical values are stated as precisely as possible in the specific examples.

[0085] In addition, it is understood that although terms such as "first" and "second" may be used in the claims to describe different components, these components should not be limited by these terms. In the embodiments, these components are represented by different component symbols. These terms are used to distinguish different components. For example, a first component can be referred to as a second component, and similarly, a second component can be referred to as a first component without departing from the scope of the embodiments. The term "and / or" as used in this manner includes any or all combinations of one or more of the related listed items. Except in the operating / working examples, or unless expressly provided, all numerical ranges, amounts, values, and percentages disclosed herein (such as those percentages of angles, time durations, temperatures, operating conditions, quantitative ratios, and the like) should be understood to be modified by the terms "approximately" or "substantially" in all embodiments. Accordingly, unless otherwise indicated, the numerical parameters stated in the present invention and the accompanying claims are approximate values that may vary as needed. For example, each numerical parameter should be interpreted at least in accordance with the number of significant figures stated and by applying ordinary rounding principles. Ranges may be expressed herein as from one endpoint to the other or between two endpoints. All ranges disclosed herein are inclusive unless otherwise specified.

[0086] The technical content and detailed description of the present invention are described as follows with reference to the accompanying drawings.

[0087] See Figure 1 , which is a circuit diagram of a DC / DC converter according to the present invention. The DC / DC converter 100 includes an input terminal, a primary circuit 10, a secondary circuit 20, a resonant cavity 30 disposed between the primary circuit and the secondary circuit, and an output terminal. In one embodiment, the DC / DC converter 100 may be a bidirectional converter, so the input terminal and the output terminal may be transposed, which is not limited by the present invention. The input terminal of the DC / DC converter 100 is connected to an input source to receive an input voltage Vin, and the output terminal of the DC / DC converter 100 is connected to a load and outputs an output voltage Vo. It is understood that the input terminal of the DC / DC converter 100 may also be connected to other converters and receive the input voltage Vin transmitted by the previous converter, and the output terminal of the DC / DC converter 100 may also be connected to other converters and output the output voltage Vo to the next converter, which is not limited by the present invention.

[0088] Please see again Figure 1As shown, the resonant cavity 30 includes a transformer TR, a first resonant capacitor Cr1, and a resonant inductor Lr. The transformer TR includes a primary winding and a secondary winding. The primary circuit 10 is electrically connected between the input terminal and the primary winding of the transformer TR, and the secondary circuit 20 is electrically connected between the secondary winding of the transformer TR and the output terminal. The first resonant capacitor Cr1 is electrically connected between the primary circuit 10 and the primary winding of the transformer TR. Specifically, for example, the first resonant capacitor Cr1 is connected between the connection point N1 of the first switching bridge leg 11 and an end point of the primary winding of the transformer TR, or between the connection point N2 of the second switching bridge leg 12 and an end point of the primary winding of the transformer TR. The resonant inductor Lr is electrically connected between the primary circuit 10 and the primary winding of the transformer TR. Specifically, for example, the resonant inductor Lr is connected between the connection point N1 of the first switching bridge leg 11 and an end point of the primary winding of the transformer TR, or between the connection point N2 of the second switching bridge leg 12 and an end point of the primary winding of the transformer TR. At this time, the resonant inductor Lr in the resonant cavity 30, the first resonant capacitor Cr1, and the excitation inductance of the transformer TR form an LLC resonant cavity. The resonant inductor Lr is, for example, the leakage inductance of the transformer TR or an external inductor, which is not limited by the present invention. The primary circuit 10 includes a first switch bridge arm 11 and a second switch bridge arm 12 connected in parallel; the secondary circuit 20 includes a third switch bridge arm 21 and a fourth switch bridge arm 22 connected in parallel. The first switch bridge arm 11 includes a first upper switch Q1 and a first lower switch Q3 connected in series; the second switch bridge arm 12 includes a second upper switch Q2 and a second lower switch Q4 connected in series; the third switch bridge arm 21 includes a third upper switch Q5 and a third lower switch Q7 connected in series; and the fourth switch bridge arm 22 includes a fourth upper switch Q6 and a fourth lower switch Q8 connected in series. The connection midpoint N1 of the first switching bridge arm 11 and the connection midpoint N2 of the second switching bridge arm 12 are connected to the two ends of the primary winding of the transformer TR; the connection midpoint N3 of the third switching bridge arm 21 and the connection midpoint N4 of the fourth switching bridge arm 22 are connected to the two ends of the secondary winding of the transformer TR. In one embodiment, the resonant cavity 30 further includes a second resonant capacitor Cr2, which is electrically connected between the secondary circuit 20 and the secondary winding of the transformer TR. Specifically, for example, the second resonant capacitor Cr2 is connected between the connection midpoint N3 of the third switching bridge arm 21 and an end point of the secondary winding of the transformer TR, or between the connection midpoint N4 of the fourth switching bridge arm 22 and an end point of the secondary winding of the transformer TR. The resonant inductor Lr of the resonant cavity 30, the first resonant capacitor Cr1, the second resonant capacitor Cr2, and the magnetizing inductance of the transformer TR form a CLLC resonant cavity. Of course, the resonant cavity 30 in the present invention can also be other resonant cavities besides the LLC resonant cavity and CLLC resonant cavity mentioned above, and the present invention is not limited thereto.

[0089] In some embodiments, the DC / DC converter 100 further includes an input capacitor unit Cin and an output capacitor unit Cout. The input capacitor unit Cin is electrically connected between the input terminal and the primary circuit 10, and is connected in parallel with the first and second switch bridge arms 11 and 12. The input capacitor unit Cin can be a single capacitor element, or it can be composed of multiple capacitor elements connected in series, in parallel, or in a combination of series and parallel. The output capacitor unit Cout is electrically connected between the output terminal and the secondary circuit 20, and is connected in parallel with the third and fourth switch bridge arms 21 and 22. Similarly, the output capacitor unit Cout can be a single capacitor element, or it can be composed of multiple capacitor elements connected in series, in parallel, or in a combination of series and parallel, which is not limited by the present invention.

[0090] To reduce output ripple, the present invention proposes a phase shift (or phase shift) control method for the DC / DC converter 100. This control method employs both frequency modulation and phase shifting control strategies. The phase shift control strategy, for example, includes PS (phase shift) applied to the second switching leg 12, LT (lead time) applied to the third switching leg 21, and DT (delay time) applied to the fourth switching leg 22. The gain of the DC / DC converter 100 is varied by combining phase shifting with the frequency modulation control strategy. This control method prevents the DC / DC converter 100 (e.g., LLC circuit, CLLC circuit, etc.) from entering burst mode under light load conditions, enabling it to operate in continuous mode, thereby resolving the problem of excessive output ripple caused by burst mode. Furthermore, this control method also takes into account light-load efficiency.

[0091] See Figure 2 As shown in FIG, it is a schematic diagram of the control signal of the phase shift control of the present invention. The DC / DC converter 100 has four pairs of switch bridge arms ( Figure 1 From left to right, for example, these represent the first through fourth switching arms. Taking the primary-side first switching arm 11 as a reference, but not limiting the present invention, phase shifting the drive signals for the other three pairs of switching arms can alter the operating mode and gain of the DC / DC converter 100, thereby preventing the converter from entering intermittent mode under light loads and reducing output ripple. PS (Phase shift) applies to the second switching arm 12, lagging relative to the first switching arm 11; LT (Lead time) applies to the third switching arm 21, leading relative to the first switching arm 11; and DT (Delay time) applies to the fourth switching arm 22, lagging relative to the first switching arm 11.

[0092] See Figure 3As shown, it is a flow chart of the phase shift control method of the present invention for determining whether the DC / DC converter is in the boost mode. The phase shift control method includes: first, determining the working mode of the DC / DC converter 100 (step S10). Figure 5 and Figure 6 As shown in FIG, they are schematic diagrams of phase shift control of output power increase and output power decrease when the DC / DC converter of the present invention is in boost mode.

[0093] Then, when it is determined that the DC / DC converter 100 is in the boost mode (step S20) and the output power is less than the first power value (step S21), the switching frequency Fs of the DC / DC converter 100 is set to the first preset frequency F1, the second switching bridge arm 12 is controlled to lag behind the first switching bridge arm 11 by a first dynamic phase P21, the third switching bridge arm 21 is controlled to advance the first switching bridge arm 11 by a first preset phase P11, and the fourth switching bridge arm 22 is controlled to lag behind the first switching bridge arm 11 by a second preset phase P12, wherein the first dynamic phase P21 is negatively correlated with the output power.

[0094] In addition, when it is determined that the DC / DC converter 100 is in the boost mode (step S20) and the output power is greater than the second power value (step S22), the switching frequency Fs of the DC / DC converter 100 is set to be negatively correlated with the output power, and the fourth switching bridge arm 22 is controlled to lag behind the first switching bridge arm 11 by a third preset phase P13, wherein the second power value is greater than the first power value.

[0095] When the DC / DC converter 100 is in boost mode, the maximum frequency of the DC / DC converter 100 is set to the maximum frequency limit Fmax, and the intermediate frequency Fmid of the DC / DC converter 100, the maximum phase shift angle PS_max of the second switching bridge arm 12, and different DT values (e.g., the second predetermined phase and the third predetermined phase) acting on the fourth switching bridge arm 22 are set. The maximum frequency limit Fmax, the intermediate frequency Fmid, the maximum phase shift PS_max, and the different DT values can be obtained in advance through testing and recorded in software or a control unit of the DC / DC converter 100.

[0096] When the output power of the DC / DC converter 100 is less than the second power value PW2, the switching frequency Fs of the DC / DC converter 100 is maintained at the first preset frequency F1, the LT value of the third switching bridge arm 21 is maintained at the first preset phase P11, and the PS value of the second switching bridge arm 12 (the first dynamic phase P21) and the DT value of the fourth switching bridge arm 22 are adjusted by a single variable. That is, when the PS value of the second switching bridge arm 12 changes, the DT value of the fourth switching bridge arm 22 is maintained at the second preset phase P12 (corresponding to the period when the output power is less than the first power value PW1). After the PS value of the second switching bridge arm 12 changes to 0, the DT value of the fourth switching bridge arm 22 is closed-loop adjusted (corresponding to the period when the output power is greater than the first power value PW1 and less than the second power value PW2, such as the third stage later described). The change in DT value of the fourth switch bridge arm 22 can be calculated by closed-loop period change. In addition, the closed-loop adjustment PS value can meet the gain requirement of the DC / DC converter 100 , wherein the first dynamic phase P21 is not greater than the maximum phase shift value (PSMax).

[0097] When the output power of the DC / DC converter 100 is greater than the second power value PW2, the PS value of the second switching bridge arm 12 is equal to 0, the LT value of the third switching bridge arm 21 is equal to 0, and the DT value of the fourth switching bridge arm 22 remains unchanged at the third preset phase P13. At the same time, the switching frequency Fs of the DC / DC converter 100 is closed-loop regulated, wherein the third preset phase P13 is greater than the second preset phase P12.

[0098] Therefore, for boost mode control, this control method involves at least two stages of parameter changes. The output power is less than the first power value PW1 in the first stage, and the output power is greater than the second power value PW2 in the second stage. In the first stage, closed-loop regulation of the PS value of the second switching leg 12 can reduce the gain under light load conditions, ensuring that the DC / DC converter 100 does not enter intermittent mode. Setting the DT value (second preset phase P12) of the fourth switching leg 22 is done to meet the gain requirements of the boost mode; setting the LT value (first preset phase P11) of the third switching leg 21 is done to achieve soft switching in the boost mode. Simultaneously, setting the switching frequency Fs in the first stage to the first preset frequency F1 (e.g., the intermediate frequency Fmid) and combining the DT value of the fourth switching leg 22 and the LT value of the third switching leg 21 with the closed-loop regulation of the PS value of the second switching leg 12 allows for high efficiency under light load conditions. Furthermore, the closed-loop regulation of the switching frequency Fs in the second phase and the open-loop control of the DT value of the fourth switching bridge arm 22 (the third predetermined phase P13) can jointly adjust the gain of the DC / DC converter 100, consistent with a normal LLC mode, ensuring high-power stability. In some embodiments, to simplify software control, a single variable is selected for closed-loop regulation in each phase, while other parameters are open-loop controlled.

[0099] When the DC / DC converter 100 outputs different voltages, they all correspond to the power value Pburst when entering the intermittent mode under conventional intermittent mode control. Therefore, in some embodiments of the present invention, when the output power gradually increases and equals the first power value PW1, the first power value PW1 can be the power value Pburst, and the second power value PW2 can be a value that exceeds the power value Pburst by a certain amount (in a typical embodiment, "a certain amount" refers to 500W, but this is not intended to limit the present invention), that is, the second power value PW2 is equal to the sum of the power value Pburst and the certain amount. When the output power gradually decreases and equals the second power value PW2, the second power value PW2 can be the power value Pburst. That is, see Figure 5 and Figure 6 As shown, when the DC / DC converter 100 is in boost mode, the value corresponding to the second power value PW2 (the sum of the power value Pburst and a certain amount) when the output power gradually increases is equal to the sum of the value corresponding to the second power value PW2 (the power value Pburst) and a buffer power (the certain amount) when the output power gradually decreases. The power value Pburst can be obtained in advance through testing and recorded in software or a control unit of the DC / DC converter 100.

[0100] In some embodiments, when the DC / DC converter 100 is in boost mode, the phase shift control method of setting the first dynamic phase P21 to be negatively correlated with the output power includes: controlling the first dynamic phase P21 to gradually decrease to 0 as the output power increases, and controlling the first dynamic phase P21 to gradually increase from 0 as the output power decreases. Specifically, when the DC / DC converter 100 is in boost mode and the output power gradually increases and becomes less than a first power value PW1, the first dynamic phase P21 is controlled to gradually decrease, for example, from a maximum phase shift PS_max to 0, as the output power increases. When the DC / DC converter 100 is in boost mode and the output power gradually decreases and becomes less than a first power value PW1, the first dynamic phase P21 is controlled to gradually increase, for example, from 0 to the maximum phase shift PS_max, as the output power decreases.

[0101] In some embodiments, when the DC / DC converter 100 is in the boost mode, the phase shift control method for setting the switching frequency Fs of the DC / DC converter 100 to be negatively correlated with the output power includes: controlling the switching frequency Fs of the DC / DC converter 100 to gradually decrease from a second preset frequency F2 as the output power increases, and controlling the switching frequency Fs of the DC / DC converter 100 to gradually increase to the second preset frequency F2 as the output power decreases. Specifically, when the DC / DC converter 100 is in the boost mode and the output power gradually increases and exceeds the second power value PW2, the switching frequency Fs is controlled to gradually decrease from the second preset frequency F2 as the output power increases; and when the DC / DC converter 100 is in the boost mode and the output power gradually decreases and exceeds the second power value PW2, the switching frequency Fs is controlled to gradually increase to the second preset frequency F2 as the output power decreases.

[0102] How to implement the above-mentioned phase shift control method and principle in the switching bridge arm of the DC / DC converter 100 will be described in more detail below. Figure 1 , with the first switching bridge arm 11 of the primary side as a reference, the first upper switch Q1 and the first lower switch Q3 are complementary conductive. Incidentally, the "complementary conductive" here is not strictly complementary conductive. It can also include a dead zone to prevent direct conduction between the upper and lower switches. In other words, the first upper switch Q1 and the first lower switch Q3 in the first switching bridge arm 11 are both in the off state, which is also included in the complementary conductive state mentioned here.

[0103] Controlling the second switching bridge arm 12 to lag behind the first switching bridge arm 11 by the first dynamic phase P21 includes: controlling the second upper switch Q2 of the second switching bridge arm 12 to lag behind the first lower switch Q3 of the first switching bridge arm 11 by the first dynamic phase P21, and controlling the second lower switch Q4 of the second switching bridge arm 12 to lag behind the first upper switch Q1 of the first switching bridge arm 11 by the first dynamic phase P21.

[0104] Controlling the third switching bridge arm 21 to advance the first switching bridge arm 11 by the first preset phase P11 includes controlling the third upper switch Q5 of the third switching bridge arm 21 to advance the first upper switch Q1 of the first switching bridge arm 11 by the first preset phase P11, and controlling the third lower switch Q7 of the third switching bridge arm 21 to advance the first lower switch Q3 of the first switching bridge arm 11 by the first preset phase P11.

[0105] Controlling the fourth switch bridge arm 22 to lag behind the first switch bridge arm 11 by the second preset phase P12 includes controlling the fourth upper switch Q6 of the fourth switch bridge arm 22 to lag behind the first lower switch Q3 of the first switch bridge arm 11 by the second preset phase P12, and controlling the fourth lower switch Q8 of the fourth switch bridge arm 22 to lag behind the first upper switch Q1 of the first switch bridge arm 11 by the second preset phase P12.

[0106] Controlling the fourth switch bridge arm 22 to lag behind the first switch bridge arm 11 by the third preset phase P13 includes controlling the fourth upper switch Q6 of the fourth switch bridge arm 22 to lag behind the first lower switch Q3 of the first switch bridge arm 11 by the third preset phase P13, and controlling the fourth lower switch Q8 of the fourth switch bridge arm 22 to lag behind the first upper switch Q1 of the first switch bridge arm 11 by the third preset phase P13.

[0107] In addition, please refer to Figure 5 The control method also has a third stage. When the output power of the DC / DC converter 100 increases from the first power value PW1 to the second power value PW2, the phase angle of the fourth switching bridge arm 22 lagging behind the first switching bridge arm 11 is controlled to gradually increase from the second preset phase P12 to the fourth preset phase P14, the switching frequency Fs of the DC / DC converter 100 is controlled to be the first preset frequency F1, and the third switching bridge arm 21 is controlled to lead the first switching bridge arm 11 by the first preset phase P11.

[0108] Furthermore, please refer to Figure 5 and Figure 9When the output power of the DC / DC converter 100 gradually increases and reaches the second power value PW2, the phase angle at which the fourth switching arm 22 lags behind the first switching arm 11 is controlled to increase from a fourth preset phase P14 to a third preset phase P13. The switching frequency Fs of the DC / DC converter 100 is controlled to increase from the first preset frequency F1 to the second preset frequency F2. The LT value of the third switching arm 21 is controlled to linearly decrease from the first preset phase P11 to 0. Furthermore, the rate of change of the phase angle at which the fourth switching arm 22 lags behind the first switching arm 11 is controlled to be greater than the rate of change of the switching frequency Fs of the DC / DC converter 100. The increase in the DT value of the fourth switching arm 22 to the third preset phase P13 is not synchronized with the increase in the switching frequency Fs to the second preset frequency F2; the former occurs before the latter. When the switching frequency Fs and the DT value of the fourth switching arm 22 switch, their respective rates of change are limited to ensure smooth switching. Incidentally, regarding the aforementioned “output power of the DC / DC converter 100 is equal to the second power value PW2,” the entire switching process (i.e., the DT value of the fourth switch bridge arm 22 increases from the fourth preset phase P14 to the third preset phase P13, the LT value of the third switch bridge arm 21 linearly decreases from the first preset phase P11 to 0, and the switching frequency Fs of the DC / DC converter 100 increases from the first preset frequency F1 to the second preset frequency F2) is basically completed in microseconds or milliseconds.

[0109] In addition, please refer to Figure 6 The control method also has a third stage. When the output power of the DC / DC converter 100 decreases from the second power value PW2 to the first power value PW1, the phase angle of the fourth switching bridge arm 22 lagging behind the first switching bridge arm 11 is controlled to gradually decrease from the fourth preset phase P14 to the second preset phase P12, the switching frequency Fs of the DC / DC converter 100 is controlled to be the first preset frequency F1, and the third switching bridge arm 21 is controlled to lead the first switching bridge arm 11 by the first preset phase P11.

[0110] Furthermore, please refer to Figure 6 and Figure 10When the output power of the DC / DC converter 100 gradually decreases and reaches the second power value PW2, the phase angle at which the fourth switching arm 22 lags behind the first switching arm 11 is controlled to decrease from the third preset phase P13 to the fourth preset phase P14. The switching frequency Fs of the DC / DC converter 100 is controlled to decrease from the second preset frequency F2 to the first preset frequency F1. The LT value of the third switching arm 21 is controlled to linearly increase from 0 to the first preset phase P11. Furthermore, the rate of change of the phase angle at which the fourth switching arm 22 lags behind the first switching arm 11 is controlled to be less than or equal to the switching frequency Fs of the DC / DC converter 100. The DT value of the fourth switching arm 22 decreases to the fourth preset phase P14 simultaneously with the decrease in the switching frequency Fs to the first preset frequency F1. Incidentally, regarding the aforementioned “output power of the DC / DC converter 100 is equal to the second power value PW2,” the entire switching process (i.e., the DT value of the fourth switch bridge arm 22 decreases from the third preset phase P13 to the fourth preset phase P14, the LT value of the third switch bridge arm 21 linearly increases from 0 to the first preset phase P11, and the switching frequency Fs of the DC / DC converter 100 decreases from the second preset frequency F2 to the first preset frequency F1) is basically completed in microseconds or milliseconds.

[0111] To ensure the gain requirements of the DC / DC converter 100 during the switching process, in the output power increasing mode, the DT value of the fourth switching bridge arm 22 is adjusted at a faster rate than the switching frequency Fs, thereby ensuring that the gain of the DC / DC converter 100 meets the voltage boost requirements at any time. Similarly, in the output power decreasing mode, the DT value of the fourth switching bridge arm 22 is adjusted at a rate that is synchronized with or slower than the switching frequency Fs. When the switching frequency Fs and the DT value of the fourth switching bridge arm 22 are switched, smooth switching is ensured by limiting their respective adjustment rates.

[0112] Incidentally, the first preset frequency F1, the second preset frequency F2, the first preset phase P11, the second preset phase P12, the third preset phase P13, the fourth preset phase P14, and the first dynamic phase P21 are determined based on the output power of the DC / DC converter 100, the first power value PW1 and the second power value PW2 are determined based on the output voltage of the DC / DC converter 100, and the second preset frequency F2 is less than or equal to the maximum frequency limit Fmax of the DC / DC converter 100.

[0113] See Figure 4 , which is a flow chart of the phase shift control method of the present invention for determining whether the DC / DC converter is in the buck mode. The phase shift control method includes: first, determining the operating mode of the DC / DC converter 100 (step S10).

[0114] See also Figure 7and Figure 8 , which are schematic diagrams of phase shift control for output power increase and output power decrease when the DC / DC converter of the present invention is in buck mode. Then, when it is determined that the DC / DC converter 100 is in buck mode (step S30) and the output power is less than a third power value (step S31), the switching frequency Fs of the DC / DC converter 100 is set to a third preset frequency F3, and the second switching bridge arm 12 is controlled to lag the first switching bridge arm 11 by a second dynamic phase P22, wherein the second dynamic phase P22 is negatively correlated with the output power. When it is determined that the DC / DC converter 100 is in buck mode (step S30) and the output power is greater than the third power value (step S32), the switching frequency Fs of the DC / DC converter 100 is set to be negatively correlated with the output power.

[0115] When the DC / DC converter 100 is in step-down mode, the maximum frequency of the DC / DC converter 100 is set to the maximum frequency limit Fmax, and the intermediate frequency Fmid of the DC / DC converter 100 and the maximum phase shift value PS_max of the second switching bridge arm 12 are set. The maximum frequency limit Fmax, the intermediate frequency Fmid, and the maximum phase shift PS_max can be obtained in advance through testing and recorded in software or a control unit of the DC / DC converter 100.

[0116] When the output power is less than the third power value PW3, the switching frequency Fs of the DC / DC converter 100 is set to a fixed value (i.e., the third preset frequency F3), such as the intermediate frequency Fmid, and the PS value of the second switching bridge arm 12 (i.e., the second dynamic phase P22) is closed-loop adjusted to meet the gain requirement, wherein the second dynamic phase P22 is not greater than the maximum phase shift value (PSMax).

[0117] When the output power is greater than the third power value PW3, the second dynamic phase P22 is 0, and the switching frequency Fs of the DC / DC converter 100 is closed-loop regulated to meet the gain requirement. The maximum value of the switching frequency Fs is the maximum frequency limit Fmax.

[0118] Therefore, for the control of the buck mode, this control method has two stages of parameter changes. The output power is less than the third power value PW3 corresponding to the first stage, and the output power is greater than the third power value PW3 corresponding to the second stage. The closed-loop adjustment of the PS value of the second switch bridge arm 12 in the first stage is to reduce the gain under light load to ensure that the intermittent mode does not occur. At the same time, the selection of the intermediate frequency (i.e., the third preset frequency F3) of this stage and the combination of the PS value adjustment can take into account the high efficiency of light load. In addition, the single closed-loop adjustment of the switching frequency Fs in the second stage to control the gain is consistent with the normal LLC mode, which can ensure the stability of high power. In some embodiments, in order to simplify the software control, a single variable can be selected for closed-loop adjustment in each stage, while other parameters are open-loop controlled. For example, when the output power gradually decreases and the load changes, the DC / DC converter 100 first performs closed-loop regulation on the switching frequency Fs to meet the gain. However, when the switching frequency Fs rises to, for example, the maximum frequency Fmax, the gain of the DC / DC converter 100 is still greater than the required gain. In this case, the PS value is increased through closed-loop regulation to reduce the gain of the DC / DC converter 100.

[0119] When the DC / DC converter 100 outputs different voltages, they all correspond to the power value Pburst when entering the intermittent mode under conventional intermittent mode control. Therefore, in some embodiments of the present invention, when the output power gradually increases and equals the third power value PW3, the third power value PW3 may be a value that exceeds the power value Pburst by a certain amount (in a typical embodiment, "a certain amount" refers to 500W, but this is not intended to limit the present invention), that is, the third power value PW3 is equal to the sum of the power value Pburst and the certain amount. When the output power gradually decreases and equals the third power value PW3, the third power value PW3 may be the power value Pburst. That is, see Figure 7 and Figure 8 When the DC / DC converter 100 is in step-down mode, the value corresponding to the third power value PW3 (the sum of the power value Pburst and the predetermined amount) when the output power gradually increases is equal to the sum of the value corresponding to the third power value PW3 (the power value Pburst) and a buffer power (the predetermined amount) when the output power gradually decreases. The power value Pburst can be obtained in advance through testing and recorded in software or a control unit of the DC / DC converter 100.

[0120] In some embodiments, when the DC / DC converter 100 is in the buck mode, the phase shift control method of setting the second dynamic phase P22 to be negatively correlated with the output power includes: controlling the second dynamic phase P22 to gradually decrease to a fifth preset phase P15 as the output power increases, and controlling the second dynamic phase P22 to gradually increase from the fifth preset phase P15 as the output power decreases, wherein the fifth preset phase P15 is not 0. Specifically, when the DC / DC converter 100 is in the step-down mode and the output power gradually increases and is less than the third power value PW3, the second dynamic phase P22 is controlled to gradually decrease from the maximum phase shift PS_max to the fifth preset phase P15 as the output power increases, for example; and when the DC / DC converter 100 is in the step-down mode and the output power gradually decreases and is less than a third power value PW3, the second dynamic phase P22 is controlled to gradually increase from the fifth preset phase P15 to, for example, the maximum phase shift PS_max as the output power decreases, where the fifth preset phase P15 is any value not equal to 0, and its value can be determined according to the output power of the DC / DC converter 100.

[0121] In some embodiments, when the DC / DC converter 100 is in step-down mode, the phase shift control method for setting the switching frequency Fs of the DC / DC converter 100 to be negatively correlated with the output power includes: controlling the switching frequency Fs of the DC / DC converter 100 to gradually decrease as the output power increases, and controlling the switching frequency Fs of the DC / DC converter 100 to gradually increase as the output power decreases. Specifically, when the DC / DC converter 100 is in step-down mode and the output power gradually increases and exceeds a third power value PW3, the switching frequency Fs is controlled to gradually decrease as the output power increases, and when the DC / DC converter 100 is in step-down mode and the output power gradually decreases and exceeds a third power value PW3, the switching frequency Fs is controlled to gradually increase as the output power decreases.

[0122] In addition, please refer to Figure 7 as well as Figure 11 When the output power of the DC / DC converter 100 gradually increases and reaches the third power value PW3, the switching frequency Fs of the DC / DC converter 100 is controlled to increase from the third preset frequency F3 to the fourth preset frequency F4 as the second dynamic phase P22 decreases to 0. The switching frequency Fs of the DC / DC converter 100 is then controlled to gradually decrease from the fourth preset frequency F4. The fourth preset frequency F4 is less than the maximum frequency limit Fmax. Incidentally, regarding the aforementioned "output power of the DC / DC converter 100 equals the third power value PW3," the entire switching process (i.e., the second dynamic phase P22 decreases to 0 and the switching frequency Fs increases from the third preset frequency F3 to the fourth preset frequency F4 and then gradually decreases) is essentially completed in microseconds or milliseconds.

[0123] In addition, please refer to Figure 8 as well as Figure 11 When the output power of the DC / DC converter 100 gradually decreases and becomes equal to the third power value PW3, the switching frequency Fs of the DC / DC converter 100 is controlled to gradually increase to a fourth preset frequency F4. The switching frequency Fs of the DC / DC converter 100 is then controlled to decrease from the fourth preset frequency F4 to the third preset frequency F3 as the second dynamic phase P22 increases from 0. The fourth preset frequency F4 is less than the maximum frequency limit Fmax. Incidentally, regarding the aforementioned "output power of the DC / DC converter 100 becomes equal to the third power value PW3," the entire switching process (i.e., the second dynamic phase P22 increases from 0 and the switching frequency Fs gradually increases to the fourth preset frequency F4 and then decreases to the third preset frequency F3) is essentially completed in microseconds or milliseconds.

[0124] Incidentally, the third power value PW3 is determined according to the output voltage Vo of the DC / DC converter 100, and the third preset frequency F3, the fourth preset frequency F4 and the fifth preset phase P15 are determined according to the output power of the DC / DC converter 100.

[0125] When the switching frequency Fs and the PS value of the second switching bridge arm 12 (ie, the second dynamic phase P22 ) are switched, smooth switching is ensured by limiting their respective change rates.

[0126] Incidentally, due to the selection of the switching point (e.g., the third power value PW3), the PS value of the second switching arm 12 must be 0 for the DC / DC converter 100 to operate at the maximum frequency during switching. Therefore, in the output power increase mode, the maximum frequency limit of the DC / DC converter 100 is increased from the intermediate frequency Fmid to the maximum frequency limit Fmax. The actual switching frequency Fs of the DC / DC converter 100 initially increases with the maximum frequency limit. Due to the increased gain required at this time, the PS value of the second switching arm 12 is synchronously decreased to meet the gain requirement. After the PS value of the second switching arm 12 decreases to 0, the switching frequency Fs decreases as the gain increases.

[0127] In the output power reduction mode, the maximum frequency limit of the DC / DC converter 100 is reduced from the maximum frequency limit Fmax to the intermediate frequency Fmid. The actual switching frequency Fs of the DC / DC converter 100 initially increases gradually as the required gain decreases until it reaches the maximum frequency limit Fmax. At this point, the PS value of the second switching bridge arm 12 begins to increase from 0. When the switching frequency Fs drops to the intermediate frequency Fmid, the PS value of the second switching bridge arm 12 also completes the switch.

[0128] In summary, the present invention has the following features and advantages: The present invention proposes a phase-shift control method and a DC / DC converter 100 that adjusts the gain of the DC / DC converter 100 by combining phase shifting with a frequency modulation control strategy. This phase-shift control method prevents the DC / DC converter 100 (e.g., LLC circuit, CLLC circuit, etc.) from entering burst mode under light loads, enabling it to operate in continuous mode, thus resolving the issue of excessive output ripple caused by burst mode. Furthermore, this phase-shift control method also maintains light-load efficiency.

[0129] The above description is only a detailed description and drawings of preferred specific embodiments of the present invention, and the features of the present invention are not limited thereto and are not intended to limit the present invention. The full scope of the present invention shall be based on the following claims. All embodiments that are consistent with the concepts of the claims of the present invention and similar variations thereof shall be included in the scope of the present invention. Any changes or modifications that can be easily conceived by any person skilled in the art within the field of the present invention shall be covered by the following claims of the present disclosure.

Claims

1. A phase shift control method for a DC / DC converter, the DC / DC converter comprising a primary circuit, a secondary circuit, and a resonant cavity disposed between the primary circuit and the secondary circuit, wherein the primary circuit comprises a first switching arm and a second switching arm, and the secondary circuit comprises a third switching arm and a fourth switching arm, wherein: The phase shift control method comprises: Determining an operating mode of the DC / DC converter; When the DC / DC converter is in a boost mode and the output power is less than a first power value, setting the switching frequency of the DC / DC converter to a first preset frequency, controlling the second switch bridge arm to lag behind the first switch bridge arm by a first dynamic phase, controlling the third switch bridge arm to lead the first switch bridge arm by a first preset phase, and controlling the fourth switch bridge arm to lag behind the first switch bridge arm by a second preset phase, wherein the first dynamic phase is negatively correlated with the output power; and When the DC / DC converter is in a boost mode and the output power is greater than a second power value, the switching frequency of the DC / DC converter is set to be negatively correlated with the output power, and the fourth switching bridge arm is controlled to lag behind the first switching bridge arm by a third preset phase, wherein the second power value is greater than the first power value.

2. The phase shift control method according to claim 1, wherein: Setting the first dynamic phase to be negatively correlated with the output power includes: controlling the first dynamic phase to gradually decrease to 0 as the output power increases, and controlling the first dynamic phase to gradually increase from 0 as the output power decreases.

3. The phase shift control method according to claim 1, wherein: Setting the switching frequency of the DC / DC converter to be negatively correlated with the output power includes: controlling the switching frequency of the DC / DC converter to gradually decrease from a second preset frequency as the output power increases, and controlling the switching frequency of the DC / DC converter to gradually increase to the second preset frequency as the output power decreases, wherein the second preset frequency is greater than the first preset frequency.

4. The phase shift control method according to claim 1, wherein: The first switch bridge arm includes a first upper switch and a first lower switch connected in series, the second switch bridge arm includes a second upper switch and a second lower switch connected in series, the third switch bridge arm includes a third upper switch and a third lower switch connected in series, and the fourth switch bridge arm includes a fourth upper switch and a fourth lower switch connected in series, the first upper switch and the first lower switch are complementary to each other, wherein: The controlling the second switch bridge arm to lag behind the first switch bridge arm by a first dynamic phase further comprises the following steps: controlling the second upper switch of the second switch bridge arm to lag behind the first lower switch of the first switch bridge arm by the first dynamic phase, and controlling the second lower switch of the second switch bridge arm to lag behind the first upper switch of the first switch bridge arm by the first dynamic phase; The controlling the third switch bridge arm to be ahead of the first switch bridge arm by a first preset phase further comprises the following steps: controlling the third upper switch of the third switch bridge arm to be ahead of the first upper switch of the first switch bridge arm by the first preset phase, and controlling the third lower switch of the third switch bridge arm to be ahead of the first lower switch of the first switch bridge arm by the first preset phase; The controlling the fourth switch bridge arm to lag behind the first switch bridge arm by a second preset phase further comprises the following steps: controlling the fourth upper switch of the fourth switch bridge arm to lag behind the first lower switch of the first switch bridge arm by the second preset phase, and controlling the fourth lower switch of the fourth switch bridge arm to lag behind the first upper switch of the first switch bridge arm by the second preset phase; The controlling of the fourth switch bridge arm to lag behind the first switch bridge arm by a third preset phase further includes the following steps: controlling the fourth upper switch of the fourth switch bridge arm to lag behind the first lower switch of the first switch bridge arm by the third preset phase, and controlling the fourth lower switch of the fourth switch bridge arm to lag behind the first upper switch of the first switch bridge arm by the third preset phase.

5. The phase shift control method according to claim 1, wherein: When the output power of the DC / DC converter increases from the first power value to the second power value, the phase angle of the fourth switching bridge arm lagging behind the first switching bridge arm is controlled to gradually increase from the second preset phase to a fourth preset phase, the switching frequency of the DC / DC converter is controlled to be the first preset frequency, and the third switching bridge arm is controlled to lead the first switching bridge arm by the first preset phase.

6. The phase shift control method according to claim 5, wherein: When the output power of the DC / DC converter gradually increases and becomes equal to the second power value, the phase angle at which the fourth switching bridge arm lags behind the first switching bridge arm is controlled to increase from the fourth preset phase to the third preset phase, the switching frequency of the DC / DC converter is controlled to increase from the first preset frequency to the second preset frequency, the phase angle at which the third switching bridge arm leads the first switching bridge arm is controlled to linearly decrease from the first preset phase to 0, and the rate of change of the phase angle at which the fourth switching bridge arm lags behind the first switching bridge arm is controlled to be greater than the rate of change of the switching frequency of the DC / DC converter.

7. The phase shift control method according to claim 1, wherein: When the output power of the DC / DC converter decreases from the second power value to the first power value, the phase angle of the fourth switching bridge arm lagging behind the first switching bridge arm is controlled to gradually decrease from a fourth preset phase to the second preset phase, the switching frequency of the DC / DC converter is controlled to be the first preset frequency, and the third switching bridge arm is controlled to lead the first switching bridge arm by the first preset phase.

8. The phase shift control method according to claim 7, wherein: When the output power of the DC / DC converter gradually decreases and becomes equal to the second power value, the phase angle at which the fourth switching bridge arm lags behind the first switching bridge arm is controlled to decrease from the third preset phase to the fourth preset phase, the switching frequency of the DC / DC converter is controlled to decrease from the second preset frequency to the first preset frequency, the phase angle at which the third switching bridge arm leads the first switching bridge arm is controlled to linearly increase from 0 to the first preset phase, and the rate of change of the phase angle at which the fourth switching bridge arm lags behind the first switching bridge arm is controlled to be less than or equal to the switching frequency of the DC / DC converter.

9. The phase shift control method according to claim 5 or 6, wherein: The first preset frequency, the second preset frequency, the first preset phase, the second preset phase, the third preset phase, the fourth preset phase, and the first dynamic phase are determined according to the output power of the DC / DC converter, the first power value and the second power value are determined according to the output voltage of the DC / DC converter, and the second preset frequency is less than or equal to the maximum frequency limit of the DC / DC converter.

10. The phase shift control method according to claim 1, wherein: The phase shift control method further comprises: When the DC / DC converter is in a step-down mode and the output power is less than a third power value, setting the switching frequency of the DC / DC converter to a third preset frequency, controlling the second switching bridge arm to lag behind the first switching bridge arm by a second dynamic phase, wherein the second dynamic phase is negatively correlated with the output power; and When the DC / DC converter is in a step-down mode and the output power is greater than the third power value, the switching frequency of the DC / DC converter is set to be negatively correlated with the output power.

11. The phase shift control method according to claim 10, wherein: Setting the second dynamic phase to be negatively correlated with the output power includes: controlling the second dynamic phase to gradually decrease to a fifth preset phase as the output power increases, and controlling the second dynamic phase to gradually increase from the fifth preset phase as the output power decreases, wherein the fifth preset phase is not 0.

12. The phase shift control method according to claim 10, wherein: Setting the switching frequency of the DC / DC converter to be negatively correlated with the output power includes: controlling the switching frequency of the DC / DC converter to gradually decrease as the output power increases, and controlling the switching frequency of the DC / DC converter to gradually increase as the output power decreases.

13. The phase shift control method according to claim 10, wherein: When the output power of the DC / DC converter gradually increases and becomes equal to the third power value, the switching frequency of the DC / DC converter is controlled to increase from the third preset frequency to a fourth preset frequency as the second dynamic phase decreases to 0, and then the switching frequency of the DC / DC converter is controlled to gradually decrease from the fourth preset frequency.

14. The phase shift control method according to claim 10, wherein: When the output power of the DC / DC converter gradually decreases and becomes equal to the third power value, the switching frequency of the DC / DC converter is controlled to gradually increase to a fourth preset frequency, and then the switching frequency of the DC / DC converter is controlled to decrease from the fourth preset frequency to a third preset frequency as the second dynamic phase increases from 0.

15. The phase shift control method according to claim 13 or 14, wherein: The third power value is determined according to the output voltage of the DC / DC converter, the third preset frequency, the fourth preset frequency, and the fifth preset phase are determined according to the output power of the DC / DC converter, and the fourth preset frequency is less than or equal to the maximum frequency limit of the DC / DC converter.

16. The phase shift control method according to claim 10, wherein: When the DC / DC converter is in a boost mode, a value corresponding to the second power value when the output power gradually increases is equal to a sum of a value corresponding to the second power value when the output power gradually decreases and a buffer power; and / or, When the DC / DC converter is in a step-down mode, a value corresponding to the third power value when the output power gradually increases is equal to a sum of a value corresponding to the third power value when the output power gradually decreases and a buffer power.

17. The phase shift control method according to claim 1, wherein: The resonant cavity includes a transformer, the first switching bridge arm includes a first upper switch and a first lower switch connected in series, the second switching bridge arm includes a second upper switch and a second lower switch connected in series, the third switching bridge arm includes a third upper switch and a third lower switch connected in series, and the fourth switching bridge arm includes a fourth upper switch and a fourth lower switch connected in series, wherein the connection midpoint of the first switching bridge arm and the connection midpoint of the second switching bridge arm are correspondingly connected to the two terminal points of a primary winding of the transformer, and the connection midpoint of the third switching bridge arm and the connection midpoint of the fourth switching bridge arm are correspondingly connected to the two terminal points of a secondary winding of the transformer.

18. The phase shift control method according to claim 1, wherein: The DC / DC converter is a bidirectional converter; and / or the resonant cavity is an LLC resonant cavity or a CLLC resonant cavity.

19. A DC / DC converter, characterized in that: The DC / DC converter comprises: A primary circuit includes a first switch bridge arm and a second switch bridge arm; A secondary circuit includes a third switch bridge arm and a fourth switch bridge arm; a resonant cavity disposed between the primary circuit and the secondary circuit; and A control unit, configured to execute the phase shift control method according to any one of claims 1 to 18.

Images