Resonant converter and control method thereof

Abstract

The invention provides a resonant converter and a control method thereof. The resonant converter comprises a primary circuit, a secondary circuit and a transformer. The control method includes: in a first control mode, controlling a plurality of primary switches and secondary switches of the primary and secondary circuits at a variable switching frequency; controlling a phase shift between the plurality of primary switches and the plurality of secondary switches in a second control mode; when the input voltage is within the preset range, controlling the resonant converter in a first control mode; when the input voltage is changed from the preset range to the outside of the preset range, the first control mode is transited to the second control mode so as to maintain the output voltage within the preset range; and when the input voltage is changed from the outside of the preset range to the inside of the preset range, the second control mode is transited to the first control mode.

Description

Technical Field

[0001] This case relates to a resonant converter and its control method, and more particularly to a resonant converter and its transient control method. Background Technology

[0002] Resonant converters, such as series resonant converters (SRC) and LLC converters, are widely used in data centers due to their zero-voltage-switching (ZVS) capability from light load to full load, high efficiency, and high power density. They are typically controlled using variable frequencies.

[0003] In some applications, such as Open Computer Project 3 (OCP3), the output voltage range becomes very narrow, and the DC-DC converter is designed to maximize efficiency during normal operation. Therefore, the ratio of magnetizing inductance to resonant inductance may be higher than in previous designs. However, the gain may be insufficient to meet hold-up time requirements. Instead, lead-time control can be used during the hold-up time because it provides (1) higher gain compared to frequency conversion control; and (2) a smooth transition between frequency conversion control and lead-time control. However, the secondary switch is a hard switch, and the resonant capacitor voltage increases significantly compared to normal operation. These problems are not severe in conventional power supply units due to their relatively low power ratings (1.5–3 kW).

[0004] However, with the rapid development of information technology, especially cloud computing, big data, and artificial intelligence, the power consumption of data centers has increased dramatically. It is necessary to significantly increase the power rating of each power supply unit without increasing the floor space. Conventional lead time control methods will face even greater challenges.

[0005] Delay-time control is also widely used in resonant converters because it features zero-voltage switching (ZVS) on the secondary side, lower resonant capacitor voltage, and lower peak and RMS currents. However, it is not suitable for hold-up times because the switching frequency of delay-time control is higher than the resonant frequency, while the switching frequency of variable frequency control is typically lower than the resonant frequency when the input voltage drops to a lower value.

[0006] Therefore, it is necessary to provide a resonant converter and its control method to solve the problems faced by the existing technology. Summary of the Invention

[0007] This invention provides a resonant converter and its control method, wherein a delay time control is applied during the hold time by controlling the switch on the primary side. Accordingly, the switch on the secondary side can achieve zero-voltage switching, and the voltage and current of the resonant capacitor can be reduced.

[0008] According to the concept of this invention, a control method for a resonant converter is provided. The resonant converter includes a primary circuit, a transformer, and a secondary circuit. The transformer is coupled between the primary circuit and the secondary circuit. The control method includes: in a first control mode, controlling a plurality of primary switches in the primary circuit and a plurality of secondary switches in the secondary circuit at a variable switching frequency; in a second control mode, controlling the phase offset between the plurality of primary switches and the plurality of secondary switches; when the input voltage of the resonant converter is within a preset range, controlling the resonant converter in the first control mode; when the input voltage changes from within the preset range to outside the preset range, transitioning from the first control mode to the second control mode to maintain the output voltage of the resonant converter within a predetermined range; and when the input voltage changes from outside the preset range to within the preset range, transitioning from the second control mode to the first control mode.

[0009] According to another concept of this invention, a resonant converter is provided. The resonant converter includes a primary circuit, a secondary circuit, a transformer, and a control module. The primary circuit includes multiple primary switches. The secondary circuit includes multiple secondary switches. The transformer is coupled between the primary circuit and the secondary circuit. The control module is structured as follows: in a first control mode, it controls the multiple primary switches of the primary circuit and the multiple secondary switches of the secondary circuit at a variable switching frequency; in a second control mode, it controls the phase offset between the multiple primary switches and the multiple secondary switches; when the input voltage of the resonant converter is within a preset range, the resonant converter is controlled in the first control mode; when the input voltage changes from within the preset range to outside the preset range, it transitions from the first control mode to the second control mode to maintain the output voltage of the resonant converter within a predetermined range; and when the input voltage changes from outside the preset range to within the preset range, it transitions from the second control mode to the first control mode. Attached Figure Description

[0010] Figure 1A This is a schematic circuit diagram of a resonant converter according to an embodiment of the present invention.

[0011] Figure 1B for Figure 1A The diagram shows a schematic circuit of a variation of the resonant converter.

[0012] Figure 2 The following is an example of the magnetizing current waveform when primary advance time control and secondary delay time control are applied during the transition period of a sudden change in switching frequency and phase offset between primary and secondary switches.

[0013] Figure 3A and Figure 3B The example shows the waveform and trajectory when transitioning directly from the first control mode to the second control mode which applies DT-DT (delay time-delay time) control.

[0014] Figure 4A and Figure 4B The example shows the waveform and trajectory diagram when seamlessly transitioning from the first control mode to the second control mode using DT-DT control.

[0015] Figure 4C , Figure 4D , Figure 4E , Figure 4F , Figure 4G and Figure 4H It shows in Figure 4A When in different intervals, Figure 1A The equivalent circuit of the resonant converter.

[0016] Figure 5A and Figure 5B The example shows the waveform and trajectory diagram when transitioning from the first control mode to the second control mode with DT-DT control.

[0017] Figure 6 The entire hold time process is illustrated when transitioning from the first control mode to the second control mode that applies DT-DT control.

[0018] Figure 7A and Figure 7B The example shows the waveform and trajectory when transitioning directly from the first control mode to the second control mode which applies SR-DT (synchronous rectification-delay time) control.

[0019] Figure 8 The entire hold time process is illustrated when transitioning from the first control mode to the second control mode that applies SR-DT control.

[0020] Figure 9 The example shows the operating waveform when transitioning directly from the second control mode with DT-DT control to the first control mode.

[0021] Figure 10A and Figure 10B The example shows the operating waveforms and trajectory diagrams when transitioning from the second control mode with DT-DT control to the first control mode with phase offset.

[0022] Figure 10C and Figure 10D Examples are in Figure 10AWhen in different intervals, Figure 1A The equivalent circuit diagram of the resonant converter.

[0023] Figure 11A and Figure 11B The example shows the operating waveforms and trajectory diagrams when transitioning from the second control mode with DT-DT control to the first control mode with the first interval feedforward.

[0024] Figure 12A and Figure 12B The example shows the waveform and trajectory when transitioning directly from the second control mode with SR-DT control to the first control mode.

[0025] Figure 13A and Figure 13B The example illustrates the operating waveforms and trajectory diagrams when transitioning from the second control mode with SR-DT control to the first control mode with phase offset.

[0026] Figure 14A and Figure 14B The example shows the operating waveforms and trajectory diagrams when transitioning from the second control mode with SR-DT control to the first control mode with first interval feedforward.

[0027] Figure 15 The transition process of the entire hold time between the first control mode and the second control mode that applies DT-DT control is illustrated.

[0028] Figure 16 The transition process of the entire hold time between the first control mode and the second control mode that applies SR-DT control is illustrated.

[0029] The reference numerals in the attached figures are explained as follows:

[0030] 1: Resonant converter

[0031] 2: Primary Circuit

[0032] 3: Secondary circuit

[0033] 10: Control Module

[0034] 11: First Controller

[0035] 12: First Driver

[0036] 13: Second controller

[0037] 14: Second Driver

[0038] 15: Calculator

[0039] 16: Compensator

[0040] 17: Zero-crossing detection circuit

[0041] C r Resonant capacitor

[0042] i Lr Resonant inductor current

[0043] I m Magnetizing current

[0044] I p Primary current

[0045] I s Secondary current

[0046] L r Resonant inductor

[0047] L m Magnetized inductor

[0048] NV o Equivalent output voltage

[0049] P1~P14: Period

[0050] Q1, Q2, Q3, Q4: Primary switches

[0051] S1, S2, S3, S4: Secondary switches

[0052] TR: Transformer

[0053] t d Secondary drive signal

[0054] t0~t14, t21~t23, t31~t33: Time

[0055] v Cr : Resonant capacitor voltage

[0056] V in Input voltage

[0057] V o Output voltage

[0058] V ref Reference voltage Detailed Implementation

[0059] Some typical embodiments that embody the features and advantages of this invention will be described in detail in the following description. It should be understood that this invention can have various variations in different forms, all of which do not depart from the scope of this invention, and the descriptions and drawings therein are for illustrative purposes only and not for limiting this invention.

[0060] As mentioned above, the switching frequency of time-delay control is higher than the resonant frequency, while the switching frequency of variable frequency control is typically lower than the resonant frequency when the input voltage drops to a lower value. To utilize time-delay control during the hold-up time, this invention provides a control method for achieving a smooth transition between variable frequency control and time-delay control. Simultaneously, transformer saturation can be avoided during the transition.

[0061] Please see Figure 1A . Figure 1A This is a schematic circuit diagram of a resonant converter according to an embodiment of this invention. Figure 1A As shown, the resonant converter 1 includes a primary circuit 2, a transformer TR, a secondary circuit 3, and a control module 10, with the transformer TR coupled between the primary circuit 2 and the secondary circuit 3. The primary circuit 2 receives the input voltage V. in It includes primary switches Q1, Q2, Q3, and Q4. Primary switches Q1 and Q2 are connected in series to form a first switch arm, and primary switches Q3 and Q4 are connected in series to form a second switch arm. The first and second switch arms are connected in parallel. Furthermore, the primary circuit 2 includes a resonant slot located between the connection node between primary switches Q1 and Q2 and the first end of the primary winding of the transformer TR. In this embodiment, the resonant slot includes a resonant capacitor C connected in series. r and resonant inductor L r Additionally, the second terminal of the primary winding of transformer TR is coupled to the connection node between primary switches Q3 and Q4. The secondary winding includes secondary switches S1, S2, S3, and S4, and provides the output voltage V. o Secondary switches S1 and S2 are connected in series to form a third switch arm, and secondary switches S3 and S4 are connected in series to form a fourth switch arm. The third and fourth switch arms are connected in parallel. Furthermore, the two ends of the secondary winding of the transformer TR are electrically connected to the connection nodes between secondary switches S1 and S2 and between secondary switches S3 and S4, respectively. In one embodiment, the secondary circuit 3 further includes an output capacitor, which is connected in parallel with the third and fourth switch arms.

[0062] In this embodiment, the primary circuit 2 and the secondary circuit 3 adopt a full-bridge architecture, but this is not a limitation. In another embodiment, the primary circuit 2 and / or the secondary circuit 3 may include a half-bridge architecture. In yet another embodiment, the secondary circuit 3 may include a center-tapped architecture.

[0063] In one embodiment, the control module 10 is configured to control the operation of the resonant converter 1 by controlling primary switches Q1, Q2, Q3, and Q4 and secondary switches S1, S2, S3, and S4. It should be noted that the drive signals of the primary and / or secondary switches within the same switch arm can have reasonable dead times and be complementary to each other. In one embodiment, the drive signals of the primary switches within the same switch arm are complementary to each other and have reasonable dead times, while the drive signals of the secondary switches within the same switch arm are complementary to each other and have reasonable dead times. The control module 10 is adapted to operate according to the input voltage V. in It operates in either the first control mode or the second control mode. Specifically, when the input voltage V... in When within the preset range, this means the input voltage V in For normal and resonant converter 1 to operate normally, control module 10 operates in the first control mode. For example, when the input voltage V... in If the input voltage V is a DC voltage, then... in If the input voltage is higher than the threshold voltage, then the input voltage V in Within a preset range. In the first control mode, the control module 10 controls the primary switches Q1, Q2, Q3, and Q4 and the secondary switches S1, S2, S3, and S4 at the same switching frequency, and the switching frequency can be fixed or variable. In the first control mode, the secondary switches S1, S2, S3, and S4 can operate as synchronous rectifier switches or remain in the off state. When the input voltage V... in When the voltage changes from within the preset range to outside the preset range, this means that the input voltage V is provided. in The power source may fail or be temporarily interrupted. In this case, the control module 10 transitions from the first control mode to the second control mode to maintain the output voltage V of the resonant converter 1. o Within the predetermined range. This maintains the output voltage V. o The period within a predetermined range is also called the hold time. For example, when the input voltage V... in If the input voltage V is a DC voltage, then... in When the input voltage drops below the threshold voltage, the input voltage V inThe range changes from within a preset range to outside the preset range. In the second control mode, primary switches Q1, Q2, Q3, and Q4 are controlled to operate ahead of secondary switches S1, S2, S3, and S4 by a certain advance time. Furthermore, in the second control mode, DT-DT (delay time-delay time) control or SR-DT (synchronous rectification-delay time) control can be used. In DT-DT control, the phases of secondary switches S1, S2, S3, and S4 are fixed, and the drive signals of secondary switches S1, S2, S3, and S4 are delayed relative to the drive signals of primary switches Q1, Q2, Q3, and Q4 by the advance time. In SR-DT control, the two secondary switches S1 and S2 operate as synchronous rectifier switches, while the other two secondary switches S3 and S4 have fixed phases, and their drive signals are delayed relative to the drive signals of the primary switches Q1, Q2, Q3, and Q4. Furthermore, DT-DT control can be applied to full-bridge or half-bridge architectures, while SR-DT control can be applied to full-bridge architectures. Additionally, when the input voltage V... in When the voltage changes from outside the preset range to within the preset range, this means that the input voltage V is provided. in The power source may have been restored, at which point the control module 10 transitions from the second control mode to the first control mode.

[0064] Therefore, the resonant inductance L r Located on the primary side, the transformer TR directly senses the voltage-second generated on the secondary side, and the phases of secondary switches S1, S2, S3, and S4 are fixed. Therefore, the voltage-second of the transformer TR is almost fixed and symmetrical, and the delay or advance time on the primary side has no significant effect on the voltage-second of the transformer TR. This reduces the transient magnetizing current of the transformer TR and avoids saturation of the transformer TR.

[0065] In another embodiment, such as Figure 1A As shown, the control module 10 includes a first controller 11, a first driver 12, a second controller 13, and a second driver 14. The first controller 11 is configured to operate based on the input voltage V. in and output voltage V o A primary control signal is generated, and the first driver 12 is configured to provide primary drive signals to primary switches Q1, Q2, Q3, and Q4 based on the primary control signal generated by the first controller 11. Similarly, the second controller 13 is configured to provide primary drive signals to primary switches Q1, Q2, Q3, and Q4 based on the input voltage V. in and output voltage V oThe second driver 14 generates a secondary control signal and provides the aforementioned secondary drive signal to the secondary switches S1, S2, S3, and S4 based on the secondary control signal generated by the second controller 13. In one embodiment, the control module 10 further includes a calculator 15 and a compensator 16. The calculator 15 is configured to calculate the output voltage V. o With input reference voltage V ref The difference between the values ​​is calculated by the calculator 15, and the compensator 16 is configured to generate a compensation signal based on the difference calculated by the calculator 15. The first controller 11 receives the compensation signal from the compensator 16 and considers the compensation signal during the generation of the primary control signal.

[0066] In one embodiment, such as Figure 1B As shown, the control module 10 includes a zero-crossing detection circuit 17, which is used to detect the zero-crossing point of the current flowing through the primary winding of the transformer TR. In one embodiment, in the second control mode, DT-DT control or SR-DT control is applied based on whether the control module 10 has the function of detecting zero crossing points. In particular, if the control module 10 does not have the function of detecting zero crossing points (e.g., ...), ... Figure 1A (as shown), then DT-DT control is applied in the second control mode. Alternatively, if the control module 10 has the function of detecting zero crossings (e.g., ...), Figure 1B As shown, the control module 10 with zero-crossing detection circuit 17 applies SR-DT control in the second control mode.

[0067] Figure 2 The illustration shows magnetizing current waveforms when primary advance time control and secondary delay time control are applied during the transition period of a sudden change in switching frequency and phase offset between the primary and secondary switches. Primary advance time control means that the primary switch operates with a controlled advance time relative to the secondary switch, and secondary delay time control means that the secondary switch operates with a controlled delay time relative to the primary switch. Figure 2 The trend of the magnetizing current peaks and troughs under primary advance time control is depicted by dashed lines, while the trend of the magnetizing current peaks and troughs under secondary delay time control is depicted by solid lines. According to... Figure 2 It can be observed that primary advance time control has better performance than secondary delay time control. Therefore, although the phase offset between the primary and secondary switches is the same under primary advance time control as under secondary delay time control, primary advance time control is mainly used in this case to achieve better performance. However, it should be noted that the transition method between different control methods described later in this case is also applicable to applications using secondary delay time control.

[0068] The following will describe various scenarios of transition between the first control mode and the second control mode.

[0069] Figure 3A and Figure 3B The example illustrates the waveform and trajectory when transitioning directly from the first control mode to the second control mode using DT-DT control. Figure 3A and Figure 3B In the diagram, Q1 represents the primary drive signal of the primary switch Q1, S1 represents the secondary drive signal of the secondary switch S1, and i Lr For the flow through the resonant inductor L r The resonant inductor current, and v Cr For the resonant capacitor C r The resonant capacitor voltage. For example... Figure 3A and Figure 3B As shown, during the direct transition, the switching frequency shifts directly from a low frequency in the first control mode to above the resonant frequency of the DT-DT control in the second control mode. The resonant inductor current i Lr and resonant capacitor voltage v Cr There are some fluctuations. In this embodiment, the resonant groove needs to be carefully designed to prevent the resonant inductance L from... r Saturation and resonant capacitance C r Overvoltage.

[0070] Figure 4A and Figure 4B This example illustrates the waveforms and trajectory diagrams during a seamless transition from a first control mode to a second control mode employing DT-DT control, as shown in one embodiment. Figure 4A middle, I m For the flow through the magnetized inductor L m The magnetizing current, and the resonant inductor current i Lr and magnetizing current I m The same waveform is shown, where the resonant inductor current i Lr The amplitude is greater than the magnetizing current I m The amplitude. Furthermore, during period P1 (i.e., before time t2), control module 10 operates in the first control mode; during period P2 (i.e., between time t2 and time t4), control module 10 transitions from the first control mode to the second control mode, and during period P3 (i.e., after time t4), control module 10 operates in the second control mode. Figure 4B In the diagram, the outermost trajectory represents the trajectory under the first control mode, while the innermost trajectory represents the trajectory under the second control mode (DT-DT control) with the same gain. For example... Figure 4A and Figure 4B As shown, when a transition from the first control mode to the second control mode is required (i.e., during period P2), when the resonant capacitor voltage v Cr When the target resonant voltage is reached under DT-DT control (corresponding to...) Figure 4BAt point A), the primary switch Q1 is turned off. Then, when the resonant inductor current i... Lr When the target resonant current is reached under DT-DT control (corresponding to...) Figure 4B At point B), the secondary switch S1 is turned off. The duration between the turn-off time of the primary switch Q1 and the turn-off time of the secondary switch S1 is the start delay time of the DT-DT control. The resonant capacitor voltage v... Cr and resonant inductor current i Lr It can be sensed by voltage and current sensors, or based on the input voltage V. in Output voltage V o The target resonant voltage and target resonant current are estimated using a lookup table based on the load conditions.

[0071] Figure 4C An equivalent circuit diagram of the resonant converter 1 in one embodiment is shown during time t0 to t1. During this period, the equivalent output voltage on the primary side is NV. o Where N is the primary-to-secondary turns ratio of transformer TR. Furthermore, the resonant capacitor voltage v... Cr Resonant inductor current i Lr and magnetizing current I m It is represented as follows:

[0072] v Cr (t)=(-V in +N·V o )+(v Cr0 +(V in -N·V o ))·cos(ω r t)+i Lr0 ·Z·sin(ω r t) (1)

[0073]

[0074]

[0075] In formulas (1) to (3), v Cr0 The resonant capacitor voltage v Cr At the initial voltage at time t0, i Lr0 For the resonant inductor current i Lr At the initial current at time t0, Z equals And it is the resonant inductance L in the resonant slot. r and resonant capacitor C r The characteristic impedance, and ω equals And it is a resonant inductor L r and resonant capacitor C r angular frequency.

[0076] Secondary current I S The following can be derived:

[0077] I S (t)=N(i Lr (t)-I m (t)) (4) The resonant capacitor voltage v at time t1 Cr Resonant inductor current i Lr and magnetizing current I m Defined as v Cr1 i Lr1 and I m1 .

[0078] v Cr1 =v Cr (t1),i Lr1 =i Lr (t1),I m1 =I m (t1) (5)

[0079] Figure 4D The equivalent circuit diagram of resonant converter 1 during time t1 to t2 is shown. During this period, the resonant capacitor voltage v... Cr Resonant inductor current i Lr and magnetizing current I m It is represented as follows:

[0080] v Cr (t)=-V in +(v Cr1 +V in )·cos(ω r (t-t1))+i Lr1 ·Z·sin(ω r (t-t1)) (6)

[0081]

[0082] The resonant capacitor voltage v at time t2 Cr Resonant inductor current i Lr and magnetizing current I m Defined as v Cr2 i Lr2 and I m2 .

[0083] v Cr2 =v Cr (t2),i Lr2 =i Lr (t2),I m2 =I m(t2) (8)

[0084] During the period from time t0 to t2, the average output current I on the secondary side o The following can be derived:

[0085]

[0086] In formula (9), Ts is the switching period.

[0087] Figure 4E The equivalent circuit diagram of resonant converter 1 during time t2 to t3 is shown. During this period, the resonant capacitor voltage v... Cr Resonant inductor current i Lr and magnetizing current I m It is represented as follows:

[0088] v Cr (t)=(V in -N·V o )+(v Cr2 -(V in -N·V o ))·cos(ω r (t-t2))+i Lr2 ·Z·sin(ω r (t-t2)) (10)

[0089]

[0090] The resonant capacitor voltage v at time t3 Cr Resonant inductor current i Lr and magnetizing current I m Defined as v Cr3 i Lr3 and I m3 .

[0091] v Cr3 =v Cr (t3),i Lr3 =i Lr (t3),I m3 =I m (t3) (13)

[0092] Figure 4F The equivalent circuit of resonant converter 1 during time t3 to t4 is shown. During this period, the resonant capacitor voltage v Cr Resonant inductor current i Lr and magnetizing current I m It is represented as follows:

[0093] v Cr (t)=(-V in-N·V o )+(v Cr3 +(V in +N·V o ))·cos(ω r (t-t3))+i Lr3 ·Z·sin(ω r (t-t3)) (14)

[0094]

[0095] The resonant capacitor voltage v at time t4 Cr Resonant inductor current i Lr and magnetizing current I m Defined as v Cr4 i Lr4 and I m4 .

[0096] v Cr4 =v Cr (t4),i Lr4 =i Lr (t4),I m4 =I m (t4) (17)

[0097] Figure 4G The equivalent circuit of resonant converter 1 during time t4 to t5 is shown. During this period, the resonant capacitor voltage v Cr Resonant inductor current i Lr and magnetizing current I m It is represented as follows:

[0098] v Cr (t)=(-V in +N·V o )+(v Cr4 +(V in -N·V o ))·cos(ω r (t-t4))+i Lr4 ·Z·sin(ω r (t-t4)) (18)

[0099]

[0100] The resonant capacitor voltage v at time t5 Cr Resonant inductor current i Lr and magnetizing current I m Defined as v Cr5 i Lr5 and I m5 .

[0101] vCr5 =v Cr (t5),i Lr5 =i Lr (t5),I m5 =I m (t5) (21)

[0102] Figure 4H The equivalent circuit of resonant converter 1 during time t5 to t6 is shown. During this period, the resonant capacitor voltage v... Cr Resonant inductor current i Lr and magnetizing current I m It is represented as follows:

[0103] v Cr (t)=(V in +N·V o )+(v Cr5 -(V in +N·V o ))·cos(ω r (t-t5))+i Lr5 ·Z·sin(ω r (t-t5)) (22)

[0104]

[0105] The resonant capacitor voltage v at time t6 Cr Resonant inductor current i Lr and magnetizing current I m Defined as v Cr6 i Lr6 , and I m6 .

[0106] v Cr6 =v Cr (t6),i Lr6 =i Lr (t6),I m6 =I m (t6) (25)

[0107] During the period from time t4 to t6, the average output current I on the secondary side o The following can be derived:

[0108]

[0109] Based on the above derivation, we can obtain all the information needed to build the lookup table, thereby achieving a smooth transition from the first control mode to the second control mode using DT-DT control. Specifically, to achieve a smooth transition, we need to match the initial state of the transition phase (i.e., period P2) with the final state of the first control mode (i.e., period P1), and match the final state of the transition phase with the initial state of the second control mode (i.e., period P3). Assuming that the input and output voltages remain constant before and after the transition phase, we also need to match the average output current of the first and second control modes. Alternatively, we can also match the gains of the first and second control modes.

[0110] The first step is to solve the steady-state formula for the first control mode during the period P1, as shown in formula (27). In this embodiment, to solve formula (27), the four variables V in ,、V o T S and I o Any three of them are required. Generally, we know the switching cycle T. S and output voltage V o An additional sensor is needed to obtain the input voltage V. in Or output current I o .

[0111]

[0112] According to formula (27), the initial state of the transition phase during period P2 is obtained, which is v. Cr1 andi Lr1 .

[0113] The second step is to solve the steady-state formula for the second control mode of P3 during this period. This is done after knowing the five variables V... in V o T S Delay time and I o By adding any four of the given conditions, such as those in formula (28), the steady-state formula for the second control mode can be solved. Generally, we know the switching period T... S Output voltage V o and output current I o An additional sensor is needed to obtain the input voltage V. in Or a delay time. For this transition control, we can assume an input voltage V in Keeping it unchanged, we can use the first control mode during which the output voltage V of P1 remains constant. o In this way, the initial state of P3 during the second control mode can be derived, that is, v. Cr4i Lr4 and the delay time (i.e., the length of time between times t5 and t6).

[0114]

[0115] Given the initial state v Cr2 i Lr2 and final state v Cr4 i Lr4 We can obtain time t3 and t3, and use this to design the modulation of the transition state in P2 during this period. For different load conditions or different input and output voltages, we can obtain a lookup table to achieve a smooth transition from the first control mode to the second control mode using DT-DT control.

[0116] Figure 5A and Figure 5B This illustration shows the waveform and trajectory diagram during a delayed transition from a first control mode to a second control mode employing DT-DT control, as shown in one embodiment. Figure 5A In the diagram, S2 represents the secondary drive signal of secondary switch S2, and the secondary drive signals of secondary switches S1 and S2 are shown with the same waveform, wherein the amplitude of the secondary drive signal of secondary switch S1 is greater than the amplitude of the secondary drive signal of magnetized secondary switch S2. For example... Figure 5A and Figure 5B As shown, during period P4, control module 10 operates in the first control mode. When a transition from the first control mode to the second control mode is required, the switching frequencies of primary switches Q1, Q2, Q3, and Q4 change directly in the next cycle, for example, but not limited to, becoming 1.5 to 1.8 times the resonant frequency. For secondary switches S1, S2, S3, and S4, all secondary drive signals are deactivated for one cycle (i.e., during period P5) to release energy within the resonant slot. When the resonant inductor current i Lr When the current drops to 0, the secondary-side diode or body diode can prevent the current from decreasing or increasing further. Starting from the next cycle (i.e., period P6), secondary switches S1, S2, S3, and S4 are turned on, and DT-DT control in the second control mode is enabled. In this embodiment, it can be observed that the energy of the resonant tank is rebuilt in the following few cycles, and in the resonant inductor L... r There is no overcurrent in the resonant capacitor C. r There is no overvoltage. In another embodiment, P5 may include multiple cycles, that is, the secondary switches S1, S2, S3 and S4 may be deactivated for multiple cycles.

[0117] Figure 6 This example illustrates the entire hold-up time process during the transition from a first control mode to a second control mode employing DT-DT control in one embodiment. Figure 6In this context, EN is a signal indicating whether hold time is enabled, and I... P For primary current, I S For secondary current and t d This represents the delay time of the secondary drive signal relative to the primary drive signal. Primary current I P and magnetizing current I m The waveform is shown in the same way, where the primary current I P The amplitude is greater than the magnetizing current I m The amplitude. For example... Figure 6 As shown, in this embodiment, the output voltage V o It is stable, and there is no overcurrent or overvoltage in the resonant tank.

[0118] Figure 7A and Figure 7B The diagram illustrates the waveform and trajectory of a direct transition from a first control mode to a second control mode using SR-DT control, according to one embodiment. S4 represents the secondary drive signal of secondary switch S4. Furthermore, during period P7, control module 10 operates in the first control mode; and during period P8, control module 10 operates in the second control mode using SR-DT control. In this embodiment, control module 10 directly transitions from the first control mode to the second control mode using SR-DT control. Secondary switches S1 and S2 operate as synchronous rectifier switches throughout the process. Secondary switches S3 and S4 act as synchronous rectifier switches before the transition and directly transition to delay time control when the transition occurs. It should be noted that the switches in the same bridge arm have reasonable dead times and are complementary to each other. Primary switches Q1 and Q4 share the same primary drive signal. In this embodiment, by Figure 7A and Figure 7B As can be observed from the waveforms and trajectories shown, no overcurrent or overvoltage occurred in the resonant slot. Furthermore, since the secondary switches S1 and S2 continuously operate as synchronous rectifier switches, the transition process is very smooth.

[0119] Figure 8 This example illustrates the entire hold-up time process during the transition from a first control mode to a second control mode employing SR-DT control in one embodiment. For example... Figure 8 As shown, in this embodiment, the output voltage V o It is stable and does not have much overshoot or undershoot.

[0120] Figure 9This example illustrates the waveform diagram of a direct transition from a second control mode using DT-DT control to a first control mode in one embodiment. In this embodiment, if the secondary drive signals of secondary switches S1 and S2 are shown with the same waveform, the amplitude of the secondary drive signal of secondary switch S2 is smaller than the amplitude of the secondary drive signal of secondary switch S1. Furthermore, in this embodiment, if the resonant inductor current i Lr and magnetizing current I m The same waveform is used to illustrate the magnetizing current I. m The amplitude of the waveform is less than the resonant inductor current i. Lr The amplitude of the waveform. During the transition, the switching frequency changes directly from above the resonant frequency to the frequency in the first control mode, with the same gain. Depending on the load conditions, the frequency in the first control mode may be lower or higher than the resonant frequency. Figure 9 As shown, the output voltage V o Resonant inductor current i Lr and resonant capacitor voltage v Cr There are some fluctuations. Additionally, in this embodiment, the secondary switch remains off in the first control mode. In another embodiment, the secondary switch can operate as a synchronous rectifier switch in the first control mode.

[0121] Figure 10A and Figure 10B The example illustrates the waveform and trajectory diagram of a transition from a second control mode employing DT-DT control to a first control mode with phase shift, according to one embodiment. Figure 10A and Figure 10B As shown, during period P9 (i.e., before time t9), control module 10 operates in the second control mode; during period P10 (i.e., between times t9 and t11), control module 10 transitions from the second control mode to the first control mode, and during period P11 (i.e., after time t11), control module 10 operates in the first control mode. When a transition from the second control mode to the first control mode is required, a phase shift represented by period P10 is introduced to help the resonant tank match the energy required in the first control mode. Figure 10A The time t10 shown corresponds to Figure 10B At point C, control module 10 begins to transition to the first control mode. It should be noted that the phase shift (during P10) and the length of the switching cycle can be based on load conditions and input voltage V. in and output voltage V oThe decision is made based on a lookup table. This method ensures a smooth transition from the second control mode (using DT-DT control) to the first control mode. Furthermore, in this embodiment, the secondary switch remains off in the first control mode. In another embodiment, the secondary switch can operate as a synchronous rectifier switch in the first control mode.

[0122] According to the above... Figures 4A to 4H The description of the embodiment shown illustrates that all information about the first control mode of period P11 for the second control mode in period P9 can be obtained using a similar method, and therefore will not be repeated here. It should be noted that in this embodiment, the formula for the transition phase in period P10 is different.

[0123] Figure 10C The equivalent circuit of a resonant converter 1 according to an embodiment is shown during time t9 to t10. During this period, the resonant capacitor voltage v Cr Resonant inductor current i Lr and magnetizing current I m It is represented as follows:

[0124] v Cr (t)=(-V in +N·V o )+(v Cr9 +(V in -N·V o ))·cos(ω r (t-t9))+i Lr9 ·Z·sin(ω r (t-t9)) (29)

[0125]

[0126] In formulas (29) to (31), v Cr9 i Lr9 andi m9 These are the resonant capacitor voltages v Cr Resonant inductor current i Lr and magnetizing current i m The value at time t9.

[0127] The resonant capacitor voltage v at time t10 Cr Resonant inductor current i Lr and magnetizing current i m Defined as v Cr10 i Lr10 and I m10 .

[0128] v Cr10 =v Cr (t10),iLr10 =i Lr (t10),I m10 =I m (t10) (32)

[0129] Figure 10D An equivalent circuit diagram of a resonant converter 1 according to an embodiment is shown during time t10 to t11. During this period, the resonant capacitor voltage v... Cr Resonant inductor current i Lr and magnetizing current I m It is represented as follows:

[0130] v Cr (t)=-V in +(v Cr10 +V in )·cos(ω r (t-t10))+i Lr10 ·Z·sin(ω r (t-t10)) (33)

[0131]

[0132] The resonant capacitor voltage v at time t11 Cr Resonant inductor current i Lr and magnetizing current I m Defined as v Cr11 i Lr11 and I m11 .

[0133] v Cr11 =v Cr (t11),i Lr11 =i Lr (t11),I m11 =I m (t11) (35)

[0134] Because during period P9, v Cr9 andi Lr9 It is obtained from the second control mode, and during period P11, v Cr11 andi Lr11 The transition times t10 and t11 of P10 during the first control mode are obtained from formulas (33)-(34). For different load conditions or different input and output voltages, we can obtain a lookup table to achieve a smooth transition from the second control mode with DT-DT control to the first control mode.

[0135] Figure 11A and Figure 11BThe illustration shows the waveform and trajectory diagram of the transition from a second control mode using DT-DT control to a first control mode with a first interval feedforward in one embodiment. Figure 11A and Figure 11B As shown, when transitioning from the second control mode to the first control mode, the resonant slot can match a preset energy at the end of the first switching cycle (represented by period P12). The length of the first switching cycle (period P12) can be determined by a given input voltage V. in and output voltage V o The estimation is then based on formulas or lookup tables related to load conditions. Additionally, in this example, the secondary switch remains off in the first control mode. In another embodiment, the secondary switch can operate as a synchronous rectifier switch in the first control mode.

[0136] For the first control mode in this embodiment, in the magnetized inductor L m Resonant inductor L r and resonant capacitor C r During series resonance, due to the magnetizing current I m Typically small, so most of the energy is stored in the resonant capacitance C. r Therefore, by ensuring the resonant capacitance C is within the range at the end of the transition phase (i.e., during period P12), r and resonant inductor L r The total energy is equal to the resonant capacitance C in the steady state of the first control mode. r and resonant inductor L r With the total energy available, we can also achieve a smooth transition from the second control mode, which uses DT-DT control, to the first control mode.

[0137] Figure 12A and Figure 12B The example illustrates the waveform and trajectory diagram when transitioning directly from a second control mode using SR-DT control to a first control mode in one embodiment. Figure 12A and Figure 12B As shown, during the transition period, the switching frequency changes directly from above the resonant frequency to the frequency in the first control mode, while maintaining the same gain. Depending on the load conditions, the frequency in the first control mode can be lower or higher than the resonant frequency. Output voltage V o Resonant inductor current i Lr and resonant capacitor voltage v Cr There are some fluctuations. Additionally, in this example, the secondary switch remains off in the first control mode. In another embodiment, the secondary switch can operate as a synchronous rectifier switch in the first control mode.

[0138] Figure 13A and Figure 13BThe example illustrates the operating waveform and trajectory during the transition from a second control mode employing SR-DT control to a first control mode with phase shift, as shown in this embodiment. Figure 13A and Figure 13B As shown, when transitioning from the second control mode to the first control mode, a phase shift, represented by period P13, is introduced to help the resonant tank match the energy required in the first control mode. During period P13, primary switch Q1 and secondary switches S1 and S2 remain off. Figure 13A The time t14 shown corresponds to Figure 13B At point D, control module 10 begins to transition to the first control mode. Furthermore, Figure 13A The period P14 shown represents the switching cycle. It should be noted that the phase shift (period P13) and the length of the switching cycle (period P14) can be based on load conditions and input voltage V. in and output voltage V o The decision is made based on a lookup table. This method ensures a smooth transition from the second control mode (using SR-DT control) to the first control mode. Furthermore, in this embodiment, the secondary switch remains off in the first control mode. In another embodiment, the secondary switch can operate as a synchronous rectifier switch in the first control mode.

[0139] Figure 14A and Figure 14B This example illustrates the waveform and trajectory diagram during the transition from a second control mode employing SR-DT control to a first control mode with a first interval feedforward, according to one embodiment. The transition in this embodiment... Figure 11A and Figure 11B The similarities are shown below, so they will not be repeated here.

[0140] Figure 15 This example illustrates the entire hold-time transition process between a first control mode and a second control mode employing DT-DT control in one embodiment. For example... Figure 15 As shown, before time t21, the input voltage V in It is normal (i.e., above the threshold voltage), and the first control mode is being implemented. At time t21, the input voltage V in The voltage drops below the threshold voltage, therefore control module 10 transitions from the first control mode to a second control mode applying DT-DT control to maintain the output voltage within a predetermined range. During the period from time t22 to t23, the input voltage V... in As the voltage rises, control module 10 maintains DT-DT control until the input voltage V... inThe voltage rises above a preset threshold. At time t23, control module 10 begins the transition from DT-DT control to the first control mode. After time t23, the first control mode is implemented. In this example, the secondary switch remains off in the first control mode. In another embodiment, the secondary switch can operate as a synchronous rectifier switch in the first control mode.

[0141] Figure 16 This example illustrates the transition process of the entire hold time between a first control mode and a second control mode employing SR-DT control in one embodiment. For example... Figure 16 As shown, before time t31, the input voltage V in It is normal (i.e., above the threshold voltage), and the first control mode is being implemented. At time t31, the input voltage V in The voltage drops below the threshold voltage, therefore control module 10 transitions from the first control mode to a second control mode applying SR-DT control to maintain the output voltage within a predetermined range. During the period from time t32 to t33, the input voltage V... in As the voltage rises, control module 10 maintains SR-DT control until the input voltage V... in The voltage rises above a preset threshold. At time t33, control module 10 begins to transition from SR-DT control to the first control mode. After time t33, the first control mode is implemented. In this example, the secondary switch remains off in the first control mode. In another embodiment, the secondary switch can operate as a synchronous rectifier switch in the first control mode.

[0142] In the above embodiments, the input voltage Vin is exemplified as a DC voltage. However, this invention is not limited to this, and the input voltage V... in In another embodiment, it can be an alternating current voltage. For example, in the input voltage V... in When the voltage is AC, if the input voltage V in If a loss occurs, a transition from the first control mode to the second control mode is implemented. Then, if the input voltage V... in If restored, a transition from the second control mode to the first control mode will be implemented.

[0143] This case may be modified in various ways by those skilled in the art, but all of them shall not deviate from the protection sought by the appended claims.

Claims

1. A control method for controlling a resonant converter, the resonant converter comprising a primary circuit, a transformer, and a secondary circuit, wherein the transformer is coupled between the primary circuit and the secondary circuit, and the control method comprising: In a first control mode, a plurality of primary switches of the primary circuit and a plurality of secondary switches of the secondary circuit are controlled with a variable switching frequency. In a second control mode, a phase offset between the plurality of primary switches and the plurality of secondary switches is controlled; When an input voltage of the resonant converter is within a preset range, the resonant converter is controlled in the first control mode; When the input voltage changes from the preset range to outside the preset range, the system transitions from the first control mode to the second control mode to maintain the output voltage of the resonant converter within a predetermined range. as well as When the input voltage changes from outside the preset range to within the preset range, the system transitions from the second control mode to the first control mode.

2. The control method of claim 1, wherein in the second control mode, the control method includes operating the plurality of primary switches to control the plurality of primary switches to lead the plurality of secondary switches by an advance time.

3. The control method of claim 2, wherein the secondary circuit includes a first switch bridge arm and a second switch bridge arm connected in parallel, and the second control mode includes a first control and a second control, wherein in the first control of the second control mode, the phases of the plurality of secondary switches are fixed, and the plurality of primary switches lead the plurality of secondary switches by the advance time; wherein in the second control of the second control mode, the plurality of secondary switches of the first switch bridge arm are controlled to operate as a synchronous rectifier switch or remain in an off state, the phases of the plurality of secondary switches of the second switch bridge arm are fixed, and the plurality of primary switches lead the plurality of secondary switches of the second switch bridge arm by the advance time.

4. The control method as described in claim 3, comprising: When the input voltage changes from the preset range to outside the preset range, the first control mode directly transitions from the first control mode to the second control mode.

5. The control method as described in claim 3, wherein the primary circuit further includes a resonant inductor and a resonant capacitor, and the control method includes: When the input voltage changes from within a preset range to outside the preset range, the first control transitions from the first control mode to the second control mode; and During the first control process of transitioning from the first control mode to the second control mode, when a voltage of a resonant capacitor reaches a target voltage, one of the plurality of primary switches is turned off, and when a current flowing through the resonant inductor reaches a target current, one of the plurality of secondary switches is turned off, wherein the duration between turning off one of the plurality of primary switches and turning off one of the plurality of secondary switches is an initial value of the advance time.

6. The control method as described in claim 3, comprising: When the input voltage changes from within the preset range to outside the preset range, the first control transitions from the first control mode to the second control mode; and During the first control process of transitioning from the first control mode to the second control mode, the plurality of secondary switches are deactivated for at least one cycle to release energy in a resonant slot of the primary circuit.

7. The control method as described in claim 3, comprising: When the input voltage changes from the preset range to outside the preset range, the second control mode directly transitions from the first control mode to the second control mode.

8. The control method as described in claim 3, comprising: When the input voltage is outside the preset range, the resonant converter is controlled by the first control in the second control mode; and When the input voltage changes from outside the preset range to within the preset range, it directly transitions from the first control mode of the second control mode to the first control mode.

9. The control method as described in claim 3, comprising: When the input voltage is outside the preset range, the resonant converter is controlled by the first control in the second control mode; When the input voltage changes from outside the preset range to within the preset range, the system transitions from the first control mode to the second control mode. as well as During the transition from the first control mode to the second control mode, the plurality of primary switches and the plurality of secondary switches are deactivated for a period of time, and then the first control mode is implemented, wherein in the first control mode, the period and all switching cycles of the plurality of primary switches are determined according to the load condition, the output voltage and the output voltage of the resonant converter.

10. The control method as described in claim 3, comprising: When the input voltage is outside the preset range, the resonant converter is controlled by the first control in the second control mode; and When the input voltage changes from outside the preset range to within the preset range, the system transitions from the first control of the second control mode to the first control mode, and controls a first switching cycle in the first control mode according to the load condition, the output voltage and the output voltage of the resonant converter, so that the energy of a resonant slot of the primary circuit matches the preset energy.

11. The control method as described in claim 3, comprising: When the input voltage is outside the preset range, the resonant converter is controlled by the second control in the second control mode; and When the input voltage changes from outside the preset range to within the preset range, it directly transitions from the second control mode to the first control mode.

12. The control method as described in claim 3, comprising: When the input voltage is outside the preset range, the resonant converter is controlled by the second control of the second control mode; When the input voltage changes from outside the preset range to within the preset range, the second control mode transitions to the first control mode. as well as During the transition from the second control mode to the first control mode, the plurality of primary switches and the plurality of secondary switches are deactivated for a period of time, and then the first control mode is implemented, wherein in the first control mode, the period and all switching cycles of the plurality of primary switches are determined according to the load condition, the output voltage and the output voltage of the resonant converter.

13. The control method as described in claim 3, comprising: When the input voltage is outside the preset range, the resonant converter is controlled by the second control in the second control mode; and When the input voltage changes from outside the preset range to within the preset range, the second control mode transitions to the first control mode, and a first switching cycle in the first control mode is controlled according to the load condition, the output voltage and the output voltage of the resonant converter, so that the energy of a resonant slot of the primary circuit matches the preset energy.

14. The control method as described in claim 3, comprising: Detecting a zero-crossing point of a current flowing through a primary winding of the transformer; and When the input voltage is outside the preset range, the resonant converter is controlled by the second control based on the zero-crossing point and the second control mode.

15. The control method of claim 1, wherein in the second control mode, the control method includes operating the plurality of secondary switches to control the plurality of secondary switches to lag behind the plurality of secondary switches by a delay time.

16. The control method of claim 1, wherein the primary circuit includes a resonant tank, and in the first control mode, all switching frequencies of the plurality of primary switches and the plurality of secondary switches are higher than a resonant frequency of the resonant tank.

17. The control method of claim 1, wherein the primary circuit includes a resonant tank, and in the second control mode, the switching frequency of the plurality of primary switches and the plurality of secondary switches is between 1.5 and 1.8 times a resonant frequency of the resonant tank.

18. A resonant converter, comprising: A primary circuit, comprising multiple primary switches; A primary circuit, comprising multiple secondary switches; A transformer is coupled between the primary circuit and the secondary circuit; and One control module, with the following architecture: In a first control mode, the plurality of primary switches of the primary circuit and the plurality of secondary switches of the secondary circuit are controlled with a variable switching frequency. In a second control mode, a phase offset between the plurality of primary switches and the plurality of secondary switches is controlled; When an input voltage of the resonant converter is within a preset range, the resonant converter is controlled in the first control mode; When the input voltage changes from the preset range to outside the preset range, the system transitions from the first control mode to the second control mode to maintain the output voltage of the resonant converter within a predetermined range. as well as When the input voltage changes from outside the preset range to within the preset range, the system transitions from the second control mode to the first control mode.

19. The resonant converter of claim 18, wherein in the second control mode, the control module is configured to operate the plurality of primary switches to control the plurality of primary switches to lead the plurality of secondary switches by a lead time.

20. The resonant converter of claim 19, wherein the secondary circuit includes a first switch arm and a second switch arm connected in parallel, and the second control mode includes a first control and a second control, wherein in the first control of the second control mode, the control module controls the phases of the plurality of secondary switches to be fixed, and controls the advance time of the plurality of primary switches to lead the plurality of secondary switches; wherein in the second control of the second control mode, the control module controls the plurality of secondary switches of the first switch arm to operate as a synchronous rectifier switch or maintain in an off state, the phases of the plurality of secondary switches of the second switch arm are fixed, and the control module controls the advance time of the plurality of primary switches to lead the plurality of secondary switches of the second switch arm.

21. The resonant converter of claim 20, wherein when the input voltage changes from the preset range to outside the preset range, the control module architecture is the first control that directly transitions from the first control mode to the second control mode.

22. The resonant converter of claim 20, wherein the primary circuit further includes a resonant inductor and a resonant capacitor, and the control module architecture is as follows: When the input voltage changes from within a preset range to outside the preset range, the first control transitions from the first control mode to the second control mode; and During the first control process of transitioning from the first control mode to the second control mode, when a voltage of a resonant capacitor reaches a target voltage, one of the plurality of primary switches is turned off, and when a current flowing through the resonant inductor reaches a target current, one of the plurality of secondary switches is turned off, wherein the duration between turning off one of the plurality of primary switches and turning off one of the plurality of secondary switches is an initial value of the advance time.

23. The resonant converter of claim 20, wherein the control module architecture is as follows: When the input voltage changes from within a preset range to outside the preset range, the first control transitions from the first control mode to the second control mode; and During the first control process of transitioning from the first control mode to the second control mode, the plurality of secondary switches are deactivated for at least one cycle to release energy in a resonant slot of the primary circuit.

24. The resonant converter of claim 20, wherein the control module architecture is as follows: When the input voltage changes from the preset range to outside the preset range, the second control mode directly transitions from the first control mode to the second control mode.

25. The resonant converter of claim 20, wherein the control module architecture is as follows: When the input voltage is outside the preset range, the resonant converter is controlled by the first control in the second control mode; and When the input voltage changes from outside the preset range to within the preset range, it directly transitions from the first control mode of the second control mode to the first control mode.

26. The resonant converter of claim 20, wherein the control module architecture is as follows: When the input voltage is outside the preset range, the resonant converter is controlled by the first control in the second control mode; When the input voltage changes from outside the preset range to within the preset range, the system transitions from the first control mode to the second control mode. as well as During the transition from the first control mode to the second control mode, the plurality of primary switches and the plurality of secondary switches are deactivated for a period of time, and then the first control mode is implemented, wherein in the first control mode, the period and all switching cycles of the plurality of primary switches are determined according to the load condition, the output voltage and the output voltage of the resonant converter.

27. The resonant converter of claim 20, wherein the control module architecture is as follows: When the input voltage is outside the preset range, the resonant converter is controlled by the first control in the second control mode; and When the input voltage changes from outside the preset range to within the preset range, the system transitions from the first control of the second control mode to the first control mode, and controls a first switching cycle in the first control mode according to the load condition, the output voltage and the output voltage of the resonant converter, so that the energy of a resonant slot of the primary circuit matches the preset energy.

28. The resonant converter of claim 20, wherein the control module architecture is as follows: When the input voltage is outside the preset range, the resonant converter is controlled by the second control in the second control mode; and When the input voltage changes from outside the preset range to within the preset range, it directly transitions from the second control mode to the first control mode.

29. The resonant converter of claim 20, wherein the control module architecture is as follows: When the input voltage is outside the preset range, the resonant converter is controlled by the second control of the second control mode; When the input voltage changes from outside the preset range to within the preset range, the second control mode transitions to the first control mode. as well as During the transition from the second control mode to the first control mode, the plurality of primary switches and the plurality of secondary switches are deactivated for a period of time, and then the first control mode is implemented, wherein in the first control mode, the period and all switching cycles of the plurality of primary switches are determined according to the load condition, the output voltage and the output voltage of the resonant converter.

30. The resonant converter of claim 20, wherein the control module architecture is as follows: When the input voltage is outside the preset range, the resonant converter is controlled by the second control in the second control mode; and When the input voltage changes from outside the preset range to within the preset range, the second control mode transitions to the first control mode, and a first switching cycle in the first control mode is controlled according to the load condition, the output voltage and the output voltage of the resonant converter, so that the energy of a resonant slot of the primary circuit matches the preset energy.

31. The resonant converter of claim 20, wherein the control module architecture is as follows: Detect a current flowing through a zero-crossing point of a primary winding of the transformer; and When the input voltage is outside the preset range, the resonant converter is controlled by the second control based on the zero-crossing point and the second control mode.

32. The resonant converter of claim 18, wherein in the second control mode, the control module is configured to operate the plurality of secondary switches to control the plurality of secondary switches to lag behind the plurality of secondary switches by a delay time.

33. The resonant converter of claim 18, wherein the primary circuit includes a resonant tank, and in the first control mode, all switching frequencies of the plurality of primary switches and the plurality of secondary switches are higher than a resonant frequency of the resonant tank.

34. The resonant converter of claim 18, wherein the primary circuit includes a resonant slot, and in the second control mode, the switching frequency of the plurality of primary switches and the plurality of secondary switches is between 1.5 and 1.8 times a resonant frequency of the resonant slot.

35. The resonant converter of claim 18, wherein the control module comprises: A first controller is configured to generate multiple primary control signals based on the input voltage and the output voltage; A first driver is configured to provide multiple primary drive signals to the multiple primary switches based on the multiple primary control signals generated by the first controller; A second controller, configured to generate multiple secondary control signals based on the input voltage and the output voltage; and A second driver is configured to provide multiple secondary drive signals to multiple secondary switches based on the multiple secondary control signals generated by the second controller.

36. The resonant converter of claim 35, wherein the control module further comprises: A calculator, configured to calculate a difference between an output voltage and an input reference voltage; and A compensator is configured to generate a compensation signal based on the difference calculated by the calculator, wherein the first controller receives the compensation signal from the compensator and generates the plurality of primary control signals based on the compensation signal, the input voltage, and the output voltage.

37. The resonant converter of claim 18, wherein the primary circuit comprises a full-bridge architecture or a half-bridge architecture, and the secondary circuit comprises a full-bridge architecture, a half-bridge architecture, or a center-tapped architecture.

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