A resonant converter and control method

Abstract

The application provides a resonant converter and a control method, the resonant converter comprises a primary circuit, a resonant circuit, a transformer, a secondary circuit and a control circuit, the primary circuit comprises at least one group of primary switches, the resonant circuit is electrically connected to the primary circuit and a primary winding of the transformer, the secondary circuit comprises at least one group of secondary rectifying elements, the rectifying elements are rectifying switches and / or rectifying diodes, and the secondary circuit is electrically connected to a secondary winding of the transformer. The resonant converter and the control method provided by the application can simplify the design of the control circuit, reduce the cost, improve the stability, effectively control the turn-off delay time of the switch, increase the power density while improving the conversion efficiency, are relatively simple, easy to implement, and can reduce the cost and enhance the stability without increasing the secondary control.

Description

Technical Field

[0001] This invention relates to the field of power electronic conversion technology, and in particular to a resonant converter and its control method. Background Technology

[0002] Resonant converters use resonant energy storage circuits to shape the waveforms of switching voltages and / or currents. They typically operate with variable switching frequency control. When the resonant frequency is above f0, the resonant converter operates at high frequency with minimal switching losses under zero voltage switching (ZVS) conditions on the primary side, while ensuring high conversion efficiency. It is widely used in power supply designs that improve power density and efficiency conversion.

[0003] However, in applications with wide input and / or wide output voltage ranges, the input and / or output voltages are range values ​​rather than stable values. Therefore, the switching control frequency also becomes a range value. As the input and / or output voltage range increases, the control frequency range also increases, further increasing the losses of the drive and magnetic components, thus reducing conversion efficiency. Furthermore, in some applications, resonant converters are limited to a relatively finite frequency range to avoid interfering with other parts of the system.

[0004] Existing technologies disclose several resonant converters and corresponding control methods. These methods combine primary-side frequency conversion feedback control and secondary-side open-loop delay time control to control the output voltage, thereby reducing the switching frequency range of the resonant converter and improving its performance over a wide input and / or output voltage range. Furthermore, they disclose variable frequency control for controlling the primary-side switching of an isolated resonant converter and delay time control for controlling the secondary-side rectifier switching. Such resonant circuits and control methods, by reducing the switching frequency range, can increase the overall operating frequency, thereby reducing the size of passive components and increasing power density without sacrificing performance.

[0005] However, existing delay time control technologies typically use rectifier switches instead of diode rectifiers on the secondary side for switching control. This is generally achieved by sensing the secondary current and / or primary current and by delaying the corresponding secondary switch off relative to the zero crossover of the secondary or primary current. The control method that combines primary-side frequency modulation control with secondary-side delay time control is relatively complex. For manufacturers whose secondary side is already well-designed and do not require complex control, the overall design cost and stability are still difficult to meet their needs. Summary of the Invention

[0006] In view of the deficiencies of the prior art described above, the purpose of this invention is to provide a resonant converter and control method, which improves the performance of the resonant converter under a wide input and / or wide output voltage range by controlling the delay time by short-circuiting the primary winding of the transformer. At the same time, it simplifies the design of the control circuit, reduces the complexity and cost of the control system, and improves the overall stability.

[0007] To achieve the above and other related objectives, the present invention provides a resonant converter for providing an output voltage to a load, the resonant converter comprising:

[0008] A primary-side circuit, comprising at least one set of primary-side switches, the primary-side circuit being used to receive an input voltage;

[0009] A resonant circuit, electrically coupled to the primary circuit, is used to receive energy from the input voltage.

[0010] A transformer has a primary winding and a secondary winding, wherein the primary winding is electrically coupled to the resonant circuit;

[0011] The secondary circuit includes at least one set of secondary rectifier elements, wherein the rectifier elements are rectifier diodes and / or rectifier switches, and the secondary circuit is electrically coupled to the secondary winding of the transformer for rectifying and transmitting the energy of the secondary winding of the transformer to the output terminal.

[0012] The control circuit controls the switching state of the primary-side switch based on at least one of the input voltage, output voltage, and resonant current of the resonant circuit, as well as a delay time when the resonant current of the resonant circuit crosses zero, so that the primary winding of the transformer is short-circuited or open-circuited.

[0013] Optionally, the primary circuit is a composite bridge circuit, which converts DC voltage into square wave voltage and controls the connection state of the primary winding of the transformer, so that the resonant current of the resonant circuit does not pass through the primary winding of the transformer.

[0014] Optionally, the resonant circuit includes at least one resonant capacitor and at least one resonant inductor, wherein the resonant capacitor and the resonant inductor are connected in series and then connected in series with one end of the primary winding of the transformer.

[0015] Optionally, the composite bridge circuit includes:

[0016] A first bridge arm includes a first switch and a second switch connected in series, the series node of the first switch and the second switch being electrically coupled to one end of the resonant circuit;

[0017] A second bridge arm is connected in parallel with the first bridge arm. The second bridge arm includes a third switch and a fourth switch connected in series. The series node of the third switch and the fourth switch is electrically coupled to one end of the primary winding of the transformer.

[0018] A third bridge arm is connected in parallel with the first and second bridge arms. The third bridge arm includes a fifth switch and a sixth switch connected in series. One end of the fifth switch is electrically coupled to one end of the first switch and one end of the fourth switch. One end of the sixth switch is electrically coupled to one end of the second switch and one end of the third switch. The series connection of the fifth switch and the sixth switch is electrically coupled to the series connection of the resonant circuit and the primary winding of the transformer.

[0019] Furthermore, during the first time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the first switch, the third switch, and the sixth switch to be in the on state, while controlling the second switch, the fourth switch, and the fifth switch to be in the off state, thereby short-circuiting the primary winding.

[0020] During the second time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the second switch, the fourth switch, and the fifth switch to be in the on state, while controlling the first switch, the third switch, and the sixth switch to be in the off state, thereby short-circuiting the primary winding.

[0021] Optionally, the composite bridge circuit includes:

[0022] A first bridge arm includes a first switch and a second switch connected in series, the series node of the first switch and the second switch being electrically coupled to one end of the resonant circuit;

[0023] A second bridge arm is connected in parallel with the first bridge arm. The second bridge arm includes a fifth switch and a sixth switch connected in series. One end of the fifth switch is electrically coupled to one end of the first switch, and one end of the sixth switch is electrically coupled to one end of the second switch. The series node of the fifth switch and the sixth switch is electrically coupled to the series node of the resonant circuit and the primary winding of the transformer. The other end of the primary winding of the transformer is electrically coupled to one end of the non-series node of the fifth switch or the sixth switch.

[0024] Furthermore, during the first time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls both the first switch and the sixth switch to be in the on state, while simultaneously controlling both the second switch and the fifth switch to be in the off state, thereby short-circuiting the primary winding.

[0025] During the second time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls both the second switch and the fifth switch to be in the on state, while simultaneously controlling both the first switch and the sixth switch to be in the off state, thereby short-circuiting the primary winding.

[0026] Optionally, the composite bridge circuit includes:

[0027] A first bridge arm includes a first switch and a second switch connected in series, the series node of the first switch and the second switch being electrically coupled to one end of the resonant circuit;

[0028] A second bridge arm is connected in parallel with the first bridge arm. The second bridge arm includes a third switch and a fourth switch connected in series. One end of the third switch is electrically coupled to one end of the first switch, and one end of the fourth switch is electrically coupled to one end of the second switch. The series node of the third switch and the fourth switch is electrically coupled to one end of the primary winding of the transformer.

[0029] An independent switch group, the independent switch group including at least a fifth switch, one end of the fifth switch being electrically coupled to the series node of the resonant circuit and the primary winding of the transformer, and the other end of the fifth switch being electrically coupled to the series node of the third switch and the fourth switch.

[0030] Furthermore, during the first time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the first switch, the third switch, and the fifth switch to be in the on state, while controlling the second switch and the fourth switch to be in the off state, thereby short-circuiting the primary winding.

[0031] During the second time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the second switch, the fourth switch, and the fifth switch to be in the on state, while controlling the first switch and the third switch to be in the off state, thereby short-circuiting the primary winding.

[0032] Optionally, the composite bridge circuit includes:

[0033] A first bridge arm includes a first switch and a second switch connected in series. The series node of the first switch and the second switch is electrically coupled to one end of the resonant circuit, and one end of the non-series node of the first switch and the second switch is electrically coupled to one end of the primary winding of the transformer.

[0034] An independent switch group, the independent switch group including at least a fifth switch, one end of the fifth switch being electrically coupled to the series node of the resonant circuit and the primary winding of the transformer, and the other end of the fifth switch being electrically coupled to the end of the primary winding of the transformer that is electrically coupled to the first bridge arm.

[0035] Furthermore, during the first time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls both the first switch and the fifth switch to be in the on state, while simultaneously controlling both the second switch to be in the off state, thereby short-circuiting the primary winding.

[0036] During the second time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls both the second switch and the fifth switch to be in the on state, while simultaneously controlling both first switches to be in the off state, thereby short-circuiting the primary winding.

[0037] Optionally, the resonant circuit includes at least one resonant inductor, one end of which is connected in series with one end of the primary winding of the transformer.

[0038] Optionally, the composite bridge circuit includes:

[0039] A first bridge arm includes a first capacitor and a second capacitor connected in series, the series node of the first capacitor and the second capacitor being electrically coupled to the other end of the resonant inductor in the resonant circuit;

[0040] A second bridge arm is connected in parallel with the first bridge arm. The second bridge arm includes a third switch and a fourth switch connected in series. The series node of the third switch and the fourth switch is electrically coupled to the other end of the primary winding of the transformer.

[0041] A third bridge arm is connected in parallel with the first and second bridge arms. The third bridge arm includes a fifth switch and a sixth switch connected in series. One end of the fifth switch is electrically coupled to one end of the first capacitor and one end of the fourth switch. One end of the sixth switch is electrically coupled to one end of the second capacitor and one end of the third switch. The series connection of the fifth and sixth switches is electrically coupled to the series connection of the resonant inductor and the primary winding of the transformer in the resonant circuit.

[0042] Furthermore, during the first time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the third switch and the sixth switch to be in the on state, while controlling the fourth switch and the fifth switch to be in the off state, so that the primary winding is short-circuited.

[0043] During the second time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the fourth and fifth switches to be in the on state, while controlling the third and sixth switches to be in the off state, thereby short-circuiting the primary winding.

[0044] Optionally, the composite bridge circuit includes:

[0045] A first bridge arm includes a first capacitor and a second capacitor connected in series, the series node of the first capacitor and the second capacitor being electrically coupled to the other end of the resonant inductor in the resonant circuit;

[0046] A second bridge arm is connected in parallel with the first bridge arm. The second bridge arm includes a third switch and a fourth switch connected in series. One end of the third switch is electrically coupled to one end of the first capacitor, and one end of the fourth switch is electrically coupled to one end of the second capacitor. The series node of the third switch and the fourth switch is electrically coupled to one end of the primary winding of the transformer.

[0047] An independent switch group, the independent switch group including at least a fifth switch, one end of the fifth switch being electrically coupled to the series node of the resonant circuit and the primary winding of the transformer, and the other end of the fifth switch being electrically coupled to the series node of the third switch and the fourth switch.

[0048] Furthermore, during the first time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls both the third switch and the fifth switch to be in the on state, while simultaneously controlling both the fourth switch to be in the off state, thereby short-circuiting the primary winding.

[0049] During the second time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the fourth and fifth switches to be in the on state, while controlling the third switch to be in the off state, thereby short-circuiting the primary winding.

[0050] Optionally, the secondary circuit is a full-bridge rectifier circuit or a full-wave rectifier circuit.

[0051] Optionally, the full-bridge rectifier circuit or the full-wave rectifier circuit includes at least one rectifier diode.

[0052] Optionally, the resonant converter further includes a filter capacitor electrically coupled to the primary circuit and / or the secondary circuit.

[0053] Optionally, the control circuit includes a primary-side driving circuit, which sends a control signal to control the switching state of the primary-side switch based on at least one of the input voltage, output voltage, and resonant current of the resonant circuit, as well as a delay time when the resonant current of the resonant circuit crosses zero.

[0054] Optionally, the delay time can be adjusted based on the input voltage, output voltage, resonant current, or switching frequency.

[0055] Optionally, the primary-side switch is turned on at zero voltage.

[0056] This invention also provides a control method for a resonant converter, the resonant converter including a primary circuit, a resonant circuit, a transformer, a secondary circuit, and a control circuit. The primary circuit includes at least one set of primary switches. The resonant circuit is electrically coupled to the primary circuit and the primary winding of the transformer. The secondary circuit includes at least one set of secondary rectifier elements, the rectifier elements being rectifier switches and / or rectifier diodes. The secondary circuit is electrically coupled to the secondary winding of the transformer. The control method includes:

[0057] The control circuit detects an input voltage received via the primary-side circuit;

[0058] The control circuit detects an output voltage generated via the secondary circuit.

[0059] The control circuit detects a resonant current generated via the resonant circuit.

[0060] The control circuit calculates a delay time when the resonant current crosses zero.

[0061] The control circuit controls the switching state of the primary-side switch based on at least one of the input voltage, output voltage, and resonant current of the resonant circuit, as well as a delay time when the resonant current of the resonant circuit crosses zero, so that the primary winding of the transformer is short-circuited or open-circuited.

[0062] Optionally, the delay time can be adjusted based on the input voltage, output voltage, resonant current, or switching frequency.

[0063] Optionally, the control method further includes controlling the primary-side switch to turn on when there is zero voltage, as controlled by the control circuit.

[0064] The resonant converter and control method provided by this invention have the following advantages:

[0065] (1) Improve the conversion efficiency of the resonant converter: Primary-side frequency modulation control enables the resonant converter to operate at the optimal operating point under different input and / or output voltages, and can achieve efficient (ZVS) switching frequency control over a wide input and / or wide output voltage range, thereby improving conversion efficiency and reducing losses; at the same time, delay time control on the primary side can reduce the switching frequency range and increase the overall operating frequency, which can reduce the losses of drive and magnetic components, thereby improving power density and conversion efficiency.

[0066] (2) Reduce the overall cost of the resonant converter and simplify the control system: Since there is no need to design additional control circuits to realize the delay time control of the secondary side, the complexity and cost of the entire converter system can be reduced, and the economy and practicality of the entire converter system can be improved; by realizing the delay time control on the primary side, the design of the control circuit can be simplified, and the delay time control of the primary side can be directly used in conjunction with the existing secondary rectifier circuit, without the need for complex control of the secondary rectifier, thereby improving the stability of the system. Attached Figure Description

[0067] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0068] Figure 1 The diagram shown is a schematic representation of the overall structure of the resonant converter of the present invention.

[0069] Figure 2 The diagram shown is a circuit diagram of a resonant converter according to the present invention.

[0070] Figure 3 Displayed as Figure 2 The signal timing diagram of the resonant converter is shown.

[0071] Figure 4a Displayed as Figure 2 The diagram shows the operating mode diagram of the resonant converter at time [T0-T1].

[0072] Figure 4b Displayed as Figure 2 The diagram shows the operating mode diagram of the resonant converter at time [T1-T2].

[0073] Figure 4c Displayed as Figure 2 The diagram shows the operating mode diagram of the resonant converter at time [T2-T3].

[0074] Figure 4d Displayed as Figure 2 The diagram shows the operating mode diagram of the resonant converter at time [T3-T4].

[0075] Figure 4e Displayed as Figure 2 The diagram shows the operating mode diagram of the resonant converter at time [T4-T5].

[0076] Figure 4f Displayed as Figure 2 The diagram shows the operating mode diagram of the resonant converter at time [T5-T6].

[0077] Figure 5 The diagram shown is a circuit diagram of yet another resonant converter of the present invention.

[0078] Figure 6 Displayed as Figure 5 The signal timing diagram of the resonant converter is shown.

[0079] Figure 7 The diagram shown is a circuit diagram of yet another resonant converter of the present invention.

[0080] Figure 8 Displayed as Figure 7 The signal timing diagram of the resonant converter is shown.

[0081] Figure 9 The diagram shown is a circuit diagram of yet another resonant converter of the present invention.

[0082] Figure 10 Displayed as Figure 9 The signal timing diagram of the resonant converter is shown.

[0083] Figure 11 The diagram shown is a circuit diagram of yet another resonant converter of the present invention.

[0084] Figure 12 Displayed as Figure 11 The signal timing diagram of the resonant converter is shown.

[0085] Figure 13 The diagram shown is a circuit diagram of yet another resonant converter of the present invention.

[0086] Figure 14 Displayed as Figure 13 The signal timing diagram of the resonant converter is shown.

[0087] Figure 15 The flowchart shown is a control method for the resonant converter of the present invention.

[0088] Label Explanation:

[0089] 110 - Primary circuit; 120 - Resonant circuit; 130 - Transformer; 140 - Secondary circuit; 150 - Control circuit; CR1 -First capacitor; C R2 -Second capacitor; S P1 - First switch; S P2 -Second switch; S P3 -Third switch; S P4 -Fourth switch; S P5 - Fifth switch; S P6 -Sixth switch; C R -Resonant capacitor; L R - Resonant inductor; N1 - Primary winding; N2 - Secondary winding; D S1 - First rectifier diode; D S2 - Second rectifier diode; D S3 - Third rectifier diode; D S4 - Fourth rectifier diode; Co- Filter capacitor; V IN - Input voltage; V O - Output voltage; I LR - Resonant current. Detailed Implementation

[0090] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the technical solutions of this invention are described in detail below with reference to some embodiments and related drawings. Obviously, the described embodiments are only a part of this invention, not all embodiments. Based on the embodiments provided in this invention, those skilled in the art can easily understand other advantages and effects of this invention from the content disclosed in this specification. This invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this invention. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0091] It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show components related to the present invention and are not drawn according to the actual number, shape, and size of the components in the actual implementation. In the actual implementation, the form, quantity, and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex. To keep the illustrations as concise as possible, not all structures are shown in the figures.

[0092] Figure 1 The diagram shown is a schematic representation of the overall structure of the resonant converter of this invention. Figure 1 As shown, a resonant converter of the present invention is used to convert an input voltage V IN Converted into an output voltage V OProvided to the load, the resonant converter includes: a primary circuit 110, a resonant circuit 120, a transformer 130, a secondary circuit 140, and a control circuit 150.

[0093] Specifically, the primary-side circuit 110 includes at least one set of primary-side switches, and the primary-side circuit 110 is used to receive an input voltage V. IN In a preferred embodiment, the primary-side circuit 110 is a composite bridge circuit. This composite bridge circuit can convert DC voltage into a square wave voltage and control the connection state of the primary winding N1 of the transformer 130, thereby increasing the resonant current I of the resonant circuit. LR It does not pass through the primary winding of the transformer.

[0094] The resonant circuit 120 is electrically coupled to the primary circuit 110 and is used to receive the input voltage V. IN The energy; by utilizing the resonant circuit 120 to periodically cross the zero point when the current or voltage periodically crosses the zero point, the primary-side switch can be turned on or off under zero voltage or zero current conditions, thereby achieving soft switching and reducing switching losses.

[0095] The transformer 130 has a primary winding N1 and a secondary winding N2, and the primary winding N1 is electrically coupled to the resonant circuit 120.

[0096] The secondary circuit 140 includes at least one set of secondary rectifier elements, which are rectifier diodes and / or rectifier switches. The secondary circuit 140 is electrically coupled to the secondary winding N2 of the transformer 130 and is used to rectify and transmit the energy of the secondary winding N2 of the transformer 130 to the output terminal. The secondary circuit 140 is a full-bridge rectifier circuit or a full-wave rectifier circuit. It should be noted that the form of the secondary circuit 140 is not specifically limited in this invention, as long as the secondary circuit 140 can rectify the current transmitted from the secondary winding N2 of the transformer 130. When applying the resonant converter provided by this invention, the type of the secondary circuit 140 can be selected according to the actual application and design requirements, but this is all included within the scope of protection of this invention.

[0097] The control circuit 150 can adjust according to the input voltage V IN Output voltage V O and the resonant current I of the resonant circuit 120 LR At least one signal detection quantity in the resonant circuit 120, and the resonant current I of the resonant circuit 120. LRA delay time at the zero-crossing point controls the switching state of the primary-side switch, which can cause the primary winding N1 of the transformer 130 to be short-circuited or open-circuited; furthermore, the corresponding delay time can be based on the resonant current I of the resonant circuit 120. LR Adjustments can be made; furthermore, the corresponding delay time can also be combined with the input voltage V. IN Output voltage V O Adjustments may be made to the switching frequency, etc. It should be noted that this disclosure does not impose specific limitations on this.

[0098] For example, please refer to Figures 2-10 The resonant circuit 120 includes at least one resonant capacitor C. R and at least one resonant inductor L R The resonant capacitor C R With the resonant inductor L R After being connected in series, it is connected in series with one end of the primary winding N1 of the transformer 130.

[0099] In a preferred embodiment, such as Figure 2 The circuit diagram of the resonant converter shown includes the composite bridge circuit of the primary-side circuit 110, which comprises:

[0100] A first bridge arm, comprising a first switch S connected in series. P1 With the second switch S P2 The first switch S P1 and the second switch S P2 The series nodes are electrically coupled to one end of the resonant circuit 120;

[0101] A second bridge arm, connected in parallel with the first bridge arm, includes a third switch S connected in series. P3 With the fourth switch S P4 The third switch S P3 and the fourth switch S P4 The series node is electrically coupled to one end of the primary winding N1 of the transformer 130;

[0102] A third bridge arm, connected in parallel with the first and second bridge arms, the third bridge arm including a fifth switch S connected in series. P5 With the sixth switch S P6 The fifth switch S P5 One end is connected to the first switch S P1 The fourth switch S P4 One end is electrically coupled, the sixth switch S P6 One end is connected to the second switch S P2 The third switch S P3 One end of the fifth switch S is electrically coupled.P5 and the sixth switch S P6 The series node is electrically coupled to the series node of the resonant circuit 120 and the primary winding N1 of the transformer 130.

[0103] The following section describes the operating state of a resonant converter in detail, using its signal timing diagram and operating mode diagram. Please refer to the provided text. Figures 2-4f .in, Figure 2 The diagram shown is a circuit diagram of a resonant converter according to the present invention. Figure 3 Displayed as Figure 2 The signal timing diagram of the resonant converter shown is as follows. Figure 4a Displayed as Figure 2 The diagram shows the operating mode diagram of the resonant converter at time [T0-T1]. Figure 4b Displayed as Figure 2 The diagram shows the operating mode diagram of the resonant converter at time [T1-T2]. Figure 4c Displayed as Figure 2 The diagram shows the operating mode diagram of the resonant converter at time [T2-T3]. Figure 4d Displayed as Figure 2 The diagram shows the operating mode diagram of the resonant converter at time [T3-T4]. Figure 4e Displayed as Figure 2 The diagram shows the operating mode diagram of the resonant converter at time [T4-T5]. Figure 4f Displayed as Figure 2 The diagram shows the operating mode diagram of the resonant converter at time [T5-T6].

[0104] like Figure 2 , Figure 3 and Figure 4a As shown, at time [T0-T1], the first switch S in the primary circuit 110 P1 Third switch S P3 and the sixth switch S P6 Simultaneously, the second switch S is activated. P2 Fourth switch S P4 and the fifth switch S P5 Simultaneously shut down, at which point the primary side of the transformer 130 is in a short-circuited state, and the input voltage V... IN The energy is directly applied to the resonant circuit 120 for resonance, and no energy is transferred from the resonant circuit 120 to the output terminal.

[0105] like Figure 2 , Figure 3 and Figure 4b As shown, at time [T1-T2], the first switch S in the primary circuit 110 P1 and the third switch S P3 Simultaneously, the second switch S is activated.P2 Fourth switch S P4 Fifth switch S P5 and the sixth switch S P6 Simultaneously shut down, at which point the voltage excitation on the resonant circuit 120 is V. IN -nV O Energy is transferred from the resonant circuit 120 to the output terminal. It can be seen that this mode is consistent with the working mode of a traditional resonant converter.

[0106] like Figure 2 , Figure 3 and Figure 4c As shown, at time [T2-T3], the second switch S in the primary circuit 110 P2 and the fourth switch S P4 Simultaneously, the first switch S is activated. P1 Third switch S P3 Fifth switch S P5 and the sixth switch S P6 Simultaneously shut down, at which point the voltage excitation on the resonant circuit 120 is V. IN -nV O Energy is transferred from the resonant circuit 120 to the output terminal. It can be seen that the mode is still consistent with the working mode of the traditional resonant converter.

[0107] like Figure 2 , Figure 3 and Figure 4d As shown, at time [T3-T4], the second switch S in the primary circuit 110 P2 Fourth switch S P4 and the fifth switch S P5 Simultaneously, the first switch S is activated. P1 Third switch S P3 and the sixth switch S P6 Simultaneously shut down, at which point the primary side of the transformer 130 is in a short-circuited state, and the input voltage V... IN The energy is directly applied to the resonant circuit 120 for resonance, and no energy is transferred from the resonant circuit 120 to the output terminal.

[0108] like Figure 2 , Figure 3 and Figure 4e As shown, at time [T4-T5], the second switch S in the primary circuit 110 P2 and the fourth switch S P4 Simultaneously, the first switch S is activated. P1 Third switch S P3 Fifth switch S P5 and the sixth switch S P6Simultaneously shut down, at which point the voltage excitation on the resonant circuit 120 is -(V IN -V O Energy is transferred from the resonant circuit 120 to the output terminal. It can be seen that this mode is consistent with the working mode of a traditional resonant converter.

[0109] like Figure 2 , Figure 3 and Figure 4f As shown, at time [T5-T6], the first switch S in the primary circuit 110 P1 and the third switch S P3 Simultaneously, the second switch S is activated. P2 Fourth switch S P4 Fifth switch S P5 and the sixth switch S P6 Simultaneously shut down, at which point the voltage excitation on the resonant circuit 120 is -(V IN -V O Energy is transferred from the resonant circuit 120 to the output terminal. It can be seen that this mode is consistent with the working mode of a traditional resonant converter.

[0110] In this embodiment, the secondary circuit 140 includes a first rectifier diode D. S1 Second rectifier diode D S2 Third rectifier diode D S3 and the fourth rectifier diode D S4 The rectifier diode D S1 -D S4 A full-wave rectifier circuit, also known as a full-wave rectifier bridge, is constructed to rectify the current transmitted from the secondary winding N2 of transformer 130. The control circuit 150 can be implemented using analog or digital technology or a combination thereof. It is worth noting that in this embodiment, the form of the control circuit 150 is not specifically limited, as long as it can effectively control the primary circuit 110 and / or the secondary circuit 140. In one feasible design, based on a microcontroller or D... SP The control circuit 150 can adjust according to the input voltage V. IN Output voltage V O and the resonant current I of the resonant circuit 120 LR At least one signal detection quantity in the resonant circuit 120, and the resonant current I of the resonant circuit 120. LR A delay time T at the zero point D That is, during the time periods [T0-T1] and [T3-T4], the primary-side switch S is controlled. P1 -S P6 The switching state, wherein the control circuit 150 is based on the input voltage V INOutput voltage V O Resonant current I LR Or the switching frequency determines the delay time D T The delay time D T The starting point is from the resonant current I LR Starting from the zero-crossing point (which can be obtained through a zero-crossing detection circuit), the primary winding N1 of the transformer 130 can be short-circuited through the above control to increase the primary resonant current I. LR Furthermore, by obtaining the negative current required for the primary-side switch ZVS, a larger voltage is applied to the resonant circuit 120, resulting in a greater amount of energy stored in the resonant circuit 120. Therefore, compared to conventional frequency control, at the same input voltage and switching frequency, the delay time control of the primary-side circuit 110 provides a higher output voltage. This boost characteristic allows for optimization of the resonant converter's circuit performance by selecting a higher turns ratio in the transformer 130 to reduce switching losses in the primary-side circuit 110 and selecting a larger magnetizing inductor to reduce circulating current losses. Due to its boost characteristic, the resonant converter of the present invention performs best in low input voltage ranges or high output voltage ranges.

[0111] In another preferred embodiment, such as Figure 5 The circuit diagram of the resonant converter shown includes the composite bridge circuit of the primary-side circuit 110, which comprises:

[0112] A first bridge arm, comprising a first switch S connected in series. P1 With the second switch S P2 The first switch SP1 and the second switch S P2 The series nodes are electrically coupled to one end of the resonant circuit 120;

[0113] A second bridge arm, connected in parallel with the first bridge arm, includes a fifth switch S connected in series. P5 With the sixth switch S P6 The fifth switch S P5 One end is connected to the first switch S P1 One end is electrically coupled, the sixth switch S P6 One end is connected to the second switch S P2 One end of the fifth switch S is electrically coupled. P5 and the sixth switch S P6 The series node is electrically coupled to the series node of the resonant circuit 120 and the primary winding N1 of the transformer 130, and the other end of the primary winding N1 of the transformer 130 is electrically coupled to the fifth switch S. P5 Or the sixth switch S P6 One end of a non-serial node.

[0114] Figure 6 Displayed as Figure 5 The signal timing diagram of the resonant converter shown indicates that during the first time period, i.e., the time interval [T0-T3], the resonant current I in the resonant circuit 120 is... LR A delay time T at the zero point D Within the time period [T0-T1], the control circuit 150 can control the first switch S P1 and the sixth switch S P6 Both are in the ON state, and the second switch S can be controlled simultaneously. P2 and the fifth switch S P5 Both are in the off state, which can cause the primary winding N1 to be short-circuited;

[0115] During the second time period, i.e., the time interval [T3-T6], the resonant current I in the resonant circuit 120 LR A delay time T at the zero point D Within the time period [T3-T4], the control circuit 150 can control the second switch S. P2 and the fifth switch S P5 Both are in the ON state, and the first switch S can be controlled simultaneously. P1 and the sixth switch S P6 Both are in the off state, which can cause the primary winding N1 to be short-circuited.

[0116] In another preferred embodiment, such as Figure 7 The circuit diagram of the resonant converter shown includes the composite bridge circuit of the primary-side circuit 110, which comprises:

[0117] A first bridge arm, comprising a first switch S connected in series. P1 With the second switch S P2 The first switch S P1 and the second switch S P2 The series nodes are electrically coupled to one end of the resonant circuit 120;

[0118] A second bridge arm, connected in parallel with the first bridge arm, includes a third switch S connected in series. P3 With the fourth switch S P4 The third switch S P3 One end is connected to the first switch S P1 One end of the fourth switch S is electrically coupled. P4 One end is connected to the second switch S P2 One end is electrically coupled, the third switch S P3 and the fourth switch S P4The series node is electrically coupled to one end of the primary winding N1 of the transformer 130;

[0119] An independent switch group, wherein the independent switch group includes at least a fifth switch S P5 The fifth switch S P5 One end is electrically coupled to the series node of the resonant circuit 120 and the primary winding N1 of the transformer 130, and the fifth switch S P5 The other end is electrically coupled to the third switch S P3 and the fourth switch S P4 Serial nodes.

[0120] Figure 8 Displayed as Figure 7 The signal timing diagram of the resonant converter shown indicates that during the first time period, i.e., the time interval [T0-T3], the resonant current I in the resonant circuit 120 is... LR A delay time T at the zero point D Within the time period [T0-T1], the control circuit 150 controls the first switch S P1 The third switch S P3 and the fifth switch S P5 Both are in the ON state, and the second switch S can be controlled simultaneously. P2 and the fourth switch S P4 Both are in the off state, which can cause the primary winding N1 to be short-circuited;

[0121] During the second time period, i.e., the time interval [T3-T6], the resonant current I in the resonant circuit 120 LR A delay time T at the zero point D Within the time period [T3-T4], the control circuit 150 can control the second switch S. P2 The fourth switch S P4 and the fifth switch S P5 Both are in the ON state, and the first switch S can be controlled simultaneously. P1 and the third switch S P3 Both are in the off state, which can cause the primary winding N1 to be short-circuited.

[0122] In another preferred embodiment, such as Figure 9 The circuit diagram of the resonant converter shown includes the composite bridge circuit of the primary-side circuit 110, which comprises:

[0123] A first bridge arm, comprising a first switch S connected in series. P1 With the second switch S P2 The first switch S P1 and the second switch S P2The series node is electrically coupled to one end of the resonant circuit 120, and the first switch S P1 and the second switch S P2 One end of the non-series node is electrically coupled to one end of the primary winding N1 of the transformer 130;

[0124] An independent switch group, wherein the independent switch group includes at least a fifth switch S P5 The fifth switch S P5 One end is electrically coupled to the series node of the resonant circuit 120 and the primary winding N1 of the transformer 130, and the fifth switch S P5 The other end is electrically coupled to the end of the primary winding N1 of the transformer 130 that is electrically coupled to the first bridge arm.

[0125] Figure 10 Displayed as Figure 9 The signal timing diagram of the resonant converter shown indicates that during the first time period, i.e., the time interval [T0-T3], the resonant current I in the resonant circuit 120 is... LR A delay time T at the zero point D Within the time period [T0-T1], the control circuit 150 can control the first switch S P1 and the fifth switch S P5 Both are in the ON state, and the second switch S can be controlled simultaneously. P2 Both are in the off state, which can cause the primary winding N1 to be short-circuited;

[0126] During the second time period, i.e., the time interval [T3-T6], the resonant current I in the resonant circuit 120 LR A delay time T at the zero point D Within the time period [T3-T4], the control circuit 150 can control the second switch SP2 and the fifth switch S. P5 Both are in the ON state, and the first switch S can be controlled simultaneously. P1 Both are in the off state, which can cause the primary winding N1 to be short-circuited.

[0127] For example, please refer to Figures 11-14 The resonant circuit 120 may also include at least one resonant inductor L. R The resonant inductor L R One end is connected in series with one end of the primary winding N1 of the transformer 130.

[0128] In a preferred embodiment, such as Figure 11 The circuit diagram of the resonant converter shown includes the composite bridge circuit of the primary-side circuit 110, which comprises:

[0129] A first bridge arm, comprising a first capacitor C connected in series. R1 With the second capacitor C R2 The first capacitor C R1 and the second capacitor C R2 The series nodes are electrically coupled to the resonant inductor L in the resonant circuit 120. R The other end;

[0130] A second bridge arm, connected in parallel with the first bridge arm, includes a third switch S connected in series. P3 With the fourth switch S P4 The third switch S P3 and the fourth switch S P4 The series node is electrically coupled to the other end of the primary winding N1 of the transformer 130;

[0131] A third bridge arm, connected in parallel with the first and second bridge arms, the third bridge arm including a fifth switch S connected in series. P5 With the sixth switch S P6 The fifth switch S P5 One end is connected to the first capacitor C R1 The fourth switch S P4 One end is electrically coupled, the sixth switch S P6 One end is connected to the second capacitor C R2 The third switch S P3 One end of the fifth switch S is electrically coupled. P5 and the sixth switch S P6 The series nodes are electrically coupled to the resonant inductor L in the resonant circuit 120. R The series node with the primary winding N1 of the transformer 130.

[0132] Figure 12 Displayed as Figure 11 The signal timing diagram of the resonant converter shown indicates that during the first time period, i.e., the time interval [T0-T3], the resonant current I in the resonant circuit 120 is... LR A delay time T at the zero point D Within the time period [T0-T1], the control circuit 150 can control the third switch S. P3 and the sixth switch S P6 Both are in the ON state, and can simultaneously control the fourth switch S. P4 and the fifth switch S P5 Both are in the off state, which can cause the primary winding N1 to be short-circuited;

[0133] During the second time period, i.e., the time interval [T3-T6], the resonant current I in the resonant circuit 120LR A delay time T at the zero point D Within the time period [T3-T4], the control circuit 150 can control the fourth switch S. P4 and the fifth switch S P5 Both are in the ON state, and the third switch S can be controlled simultaneously. P3 and the sixth switch S P6 Both are in the off state, which can cause the primary winding N1 to be short-circuited.

[0134] In another preferred embodiment, such as Figure 13 The circuit diagram of the resonant converter shown includes the composite bridge circuit of the primary-side circuit 110, which comprises:

[0135] A first bridge arm, comprising a first capacitor C connected in series. R1 With the second capacitor C R2 The first capacitor C R1 and the second capacitor C R2 The series nodes are electrically coupled to the resonant inductor L in the resonant circuit 120. R The other end;

[0136] A second bridge arm, connected in parallel with the first bridge arm, includes a third switch S connected in series. P3 With the fourth switch S P4 The third switch S P3 One end is connected to the first capacitor C R1 One end of the fourth switch S is electrically coupled. P4 One end is connected to the second capacitor C R2 One end is electrically coupled, the third switch S P3 and the fourth switch S P4 The series node is electrically coupled to one end of the primary winding N1 of the transformer 130;

[0137] An independent switch group, wherein the independent switch group includes at least a fifth switch S P5 The fifth switch S P5 One end is electrically coupled to the series node of the resonant circuit 120 and the primary winding N1 of the transformer 130, and the fifth switch S P5 The other end is electrically coupled to the third switch S P3 and the fourth switch S P4 Serial nodes.

[0138] Figure 14 Displayed as Figure 13 The signal timing diagram of the resonant converter shown indicates that during the first time period, i.e., the time interval [T0-T3], the resonant current I in the resonant circuit 120 is...LR A delay time T at the zero point D Within the time period [T0-T1], the control circuit 150 can control the third switch S. P3 and the fifth switch S P5 Both are in the ON state, and can simultaneously control the fourth switch S. P4 Both are in the off state, which can cause the primary winding N1 to be short-circuited;

[0139] During the second time period, i.e., the time interval [T3-T6], the resonant current I in the resonant circuit 120 LR A delay time T at the zero point D Within the time period [T3-T4], the control circuit 150 can control the fourth switch S. P4 and the fifth switch S P5 Both are in the ON state, and the third switch S can be controlled simultaneously. P3 Both are in the off state, which can cause the primary winding N1 to be short-circuited.

[0140] Based on the above embodiments, the full-bridge rectifier circuit or full-wave rectifier circuit includes at least one rectifier diode; the resonant converter further includes a filter capacitor C. o The filter capacitor C o Electrically coupled to the primary circuit 110 and / or the secondary circuit 140, the output DC voltage is filtered, thereby stabilizing the output voltage of the secondary circuit 140. The control circuit 150 may include a primary-side drive circuit, which drives the input voltage V according to the input voltage V. IN Output voltage V O and the resonant current I of the resonant circuit 120 LR At least one signal detection quantity in the resonant circuit 120, and the resonant current I of the resonant circuit 120. LR A delay time T at the zero point D The control signal is sent to control the switching state of the primary-side switch.

[0141] The delay time T in the other embodiments described above D All based on the input voltage V IN Output voltage V O Resonant current I LR The switching frequency may be adjusted, and the primary-side switch is turned on at zero voltage.

[0142] Figure 15 The flowchart shown is a control method for the resonant converter of the present invention. (Reference) Figure 1 and Figure 15As shown, the present invention provides a control method for a resonant converter. The resonant converter includes a primary circuit 110, a resonant circuit 120, a transformer 130, a secondary circuit 140, and a control circuit 150. The primary circuit 110 includes at least one set of primary switches. The resonant circuit 120 is electrically coupled to the primary circuit 110 and the primary winding N1 of the transformer 130. The secondary circuit 140 includes at least one set of secondary rectifier elements, which are rectifier switches and / or rectifier diodes. The secondary circuit 140 is electrically coupled to the secondary winding N2 of the transformer 130. The control method includes:

[0143] The control circuit 150 detects an input voltage V received via the primary-side circuit 110. IN ;

[0144] The control circuit 150 detects an output voltage V generated via the secondary circuit 140. O ;

[0145] The control circuit 150 detects a resonant current I generated by the resonant circuit 120. LR ;

[0146] The resonant current I is calculated by the control circuit 150. LR A delay time T at the zero point D ;

[0147] The control circuit 150 determines the input voltage V based on the input voltage V. IN Output voltage V O and the resonant current I of the resonant circuit 120 LR At least one signal detection quantity in the resonant circuit 120, and the resonant current I of the resonant circuit 120. LR A delay time T at the zero point D The switching state of the primary-side switch is controlled so that the primary winding N1 of the transformer 130 is short-circuited or open-circuited.

[0148] Furthermore, the delay time is based on the input voltage V. IN Output voltage V O Resonant current I LR Alternatively, the switching frequency can be adjusted.

[0149] The control method further includes controlling the primary-side switch to turn on when there is zero voltage by the control circuit 150.

[0150] In summary, this invention provides a resonant converter and its control method. The resonant converter includes a primary-side circuit, a resonant circuit, a transformer, a secondary-side circuit, and a control circuit. The primary-side circuit includes at least one set of primary-side switches. The resonant circuit is electrically coupled to the primary-side circuit and the primary winding of the transformer. The secondary-side circuit includes at least one set of secondary-side rectifier elements, which are rectifier switches and / or rectifier diodes. The secondary-side circuit is electrically coupled to the secondary winding of the transformer. The resonant converter and control method provided by this invention, by implementing delay time control on the primary side, simplifies control circuit design, reduces costs, and improves stability. It also effectively controls the turn-off delay time of the switches. Primary-side frequency modulation control can maintain the lowest switching losses across the entire input and / or output voltage range, thereby improving conversion efficiency and increasing power density. Furthermore, this resonant converter and control method are relatively simple, easy to implement, and can reduce costs and enhance stability without adding secondary-side control. These technical effects enable the present invention to have better operating performance over a wide input and / or wide output voltage range, and can reduce the cost and complexity of the entire converter system. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0151] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A resonant converter for providing an output voltage to a load, characterized in that, The resonant converter includes: a primary-side circuit comprising at least one set of primary-side switches, the primary-side circuit being used to receive an input voltage; A resonant circuit, electrically coupled to the primary circuit, is used to receive energy from the input voltage. A transformer has a primary winding and a secondary winding, wherein the primary winding is electrically coupled to the resonant circuit; The secondary circuit includes at least one set of secondary rectifier elements, wherein the rectifier elements are rectifier diodes and / or rectifier switches, and the secondary circuit is electrically coupled to the secondary winding of the transformer for rectifying and transmitting the energy of the secondary winding of the transformer to the output terminal. The control circuit controls the switching state of the primary-side switch based on at least one of the input voltage, output voltage, and resonant current of the resonant circuit, as well as a delay time when the resonant current of the resonant circuit crosses zero, so that the primary winding of the transformer is short-circuited or open-circuited.

2. The resonant converter according to claim 1, characterized in that, The primary circuit is a composite bridge circuit, which converts DC voltage into square wave voltage and controls the connection state of the primary winding of the transformer, so that the resonant current of the resonant circuit does not pass through the primary winding of the transformer.

3. The resonant converter according to claim 2, characterized in that, The resonant circuit includes at least one resonant capacitor and at least one resonant inductor, and the resonant capacitor and the resonant inductor are connected in series and then connected in series with one end of the primary winding of the transformer.

4. The resonant converter according to claim 3, characterized in that, The composite bridge circuit includes: A first bridge arm includes a first switch and a second switch connected in series, the series node of the first switch and the second switch being electrically coupled to one end of the resonant circuit; A second bridge arm is connected in parallel with the first bridge arm. The second bridge arm includes a third switch and a fourth switch connected in series. The series node of the third switch and the fourth switch is electrically coupled to one end of the primary winding of the transformer. A third bridge arm is connected in parallel with the first and second bridge arms. The third bridge arm includes a fifth switch and a sixth switch connected in series. One end of the fifth switch is electrically coupled to one end of the first switch and one end of the fourth switch. One end of the sixth switch is electrically coupled to one end of the second switch and one end of the third switch. The series connection of the fifth switch and the sixth switch is electrically coupled to the series connection of the resonant circuit and the primary winding of the transformer.

5. The resonant converter according to claim 4, characterized in that, During the first time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the first switch, the third switch, and the sixth switch to be in the conducting state, while controlling the second switch, the fourth switch, and the fifth switch to be in the off state, so that the primary winding is short-circuited; During the second time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the second switch, the fourth switch, and the fifth switch to be in the on state, while controlling the first switch, the third switch, and the sixth switch to be in the off state, thereby short-circuiting the primary winding.

6. The resonant converter according to claim 3, characterized in that, The composite bridge circuit includes: A first bridge arm includes a first switch and a second switch connected in series, the series node of the first switch and the second switch being electrically coupled to one end of the resonant circuit; A second bridge arm is connected in parallel with the first bridge arm. The second bridge arm includes a fifth switch and a sixth switch connected in series. One end of the fifth switch is electrically coupled to one end of the first switch, and one end of the sixth switch is electrically coupled to one end of the second switch. The series node of the fifth switch and the sixth switch is electrically coupled to the series node of the resonant circuit and the primary winding of the transformer. The other end of the primary winding of the transformer is electrically coupled to one end of the non-series node of the fifth switch or the sixth switch.

7. The resonant converter according to claim 6, characterized in that, During the first time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the first switch and the sixth switch to be in the on state, and at the same time controls the second switch and the fifth switch to be in the off state, so that the primary winding is short-circuited. During the second time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls both the second switch and the fifth switch to be in the on state, while simultaneously controlling both the first switch and the sixth switch to be in the off state, thereby short-circuiting the primary winding.

8. The resonant converter according to claim 3, characterized in that, The composite bridge circuit includes: A first bridge arm includes a first switch and a second switch connected in series, the series node of the first switch and the second switch being electrically coupled to one end of the resonant circuit; A second bridge arm is connected in parallel with the first bridge arm. The second bridge arm includes a third switch and a fourth switch connected in series. One end of the third switch is electrically coupled to one end of the first switch, and one end of the fourth switch is electrically coupled to one end of the second switch. The series node of the third switch and the fourth switch is electrically coupled to one end of the primary winding of the transformer. An independent switch group, the independent switch group including at least a fifth switch, one end of the fifth switch being electrically coupled to the series node of the resonant circuit and the primary winding of the transformer, and the other end of the fifth switch being electrically coupled to the series node of the third switch and the fourth switch.

9. The resonant converter according to claim 8, characterized in that, During the first time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the first switch, the third switch, and the fifth switch to be in the on state, while controlling the second switch and the fourth switch to be in the off state, so that the primary winding is short-circuited. During the second time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the second switch, the fourth switch, and the fifth switch to be in the on state, while controlling the first switch and the third switch to be in the off state, thereby short-circuiting the primary winding.

10. The resonant converter according to claim 3, characterized in that, The composite bridge circuit includes: A first bridge arm includes a first switch and a second switch connected in series. The series node of the first switch and the second switch is electrically coupled to one end of the resonant circuit, and one end of the non-series node of the first switch and the second switch is electrically coupled to one end of the primary winding of the transformer. An independent switch group, the independent switch group including at least a fifth switch, one end of the fifth switch being electrically coupled to the series node of the resonant circuit and the primary winding of the transformer, and the other end of the fifth switch being electrically coupled to the end of the primary winding of the transformer that is electrically coupled to the first bridge arm.

11. The resonant converter according to claim 10, characterized in that, During the first time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the first switch and the fifth switch to be in the on state, and at the same time controls the second switch to be in the off state, so that the primary winding is short-circuited. During the second time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls both the second switch and the fifth switch to be in the on state, while simultaneously controlling both first switches to be in the off state, thereby short-circuiting the primary winding.

12. The resonant converter according to claim 2, characterized in that, The resonant circuit includes at least one resonant inductor, one end of which is connected in series with one end of the primary winding of the transformer.

13. The resonant converter according to claim 12, characterized in that, The composite bridge circuit includes: A first bridge arm includes a first capacitor and a second capacitor connected in series, the series node of the first capacitor and the second capacitor being electrically coupled to the other end of the resonant inductor in the resonant circuit; A second bridge arm is connected in parallel with the first bridge arm. The second bridge arm includes a third switch and a fourth switch connected in series. The series node of the third switch and the fourth switch is electrically coupled to the other end of the primary winding of the transformer. A third bridge arm is connected in parallel with the first and second bridge arms. The third bridge arm includes a fifth switch and a sixth switch connected in series. One end of the fifth switch is electrically coupled to one end of the first capacitor and one end of the fourth switch. One end of the sixth switch is electrically coupled to one end of the second capacitor and one end of the third switch. The series connection of the fifth and sixth switches is electrically coupled to the series connection of the resonant inductor and the primary winding of the transformer in the resonant circuit.

14. The resonant converter according to claim 13, characterized in that, During the first time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the third switch and the sixth switch to be in the conducting state, and at the same time controls the fourth switch and the fifth switch to be in the off state, so that the primary winding is short-circuited. During the second time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the fourth and fifth switches to be in the on state, while controlling the third and sixth switches to be in the off state, thereby short-circuiting the primary winding.

15. The resonant converter according to claim 12, characterized in that, The composite bridge circuit includes: A first bridge arm includes a first capacitor and a second capacitor connected in series, the series node of the first capacitor and the second capacitor being electrically coupled to the other end of the resonant inductor in the resonant circuit; A second bridge arm is connected in parallel with the first bridge arm. The second bridge arm includes a third switch and a fourth switch connected in series. One end of the third switch is electrically coupled to one end of the first capacitor, and one end of the fourth switch is electrically coupled to one end of the second capacitor. The series node of the third switch and the fourth switch is electrically coupled to one end of the primary winding of the transformer. An independent switch group, the independent switch group including at least a fifth switch, one end of the fifth switch being electrically coupled to the series node of the resonant circuit and the primary winding of the transformer, and the other end of the fifth switch being electrically coupled to the series node of the third switch and the fourth switch.

16. The resonant converter according to claim 15, characterized in that, During the first time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the third switch and the fifth switch to be in the conducting state, and at the same time controls the fourth switch to be in the off state, so that the primary winding is short-circuited. During the second time period, within a delay time when the resonant current in the resonant circuit crosses zero, the control circuit controls the fourth and fifth switches to be in the on state, while controlling the third switch to be in the off state, thereby short-circuiting the primary winding.

17. The resonant converter according to claim 1, characterized in that, The secondary circuit is a full-bridge rectifier circuit or a full-wave rectifier circuit.

18. The resonant converter according to claim 17, characterized in that, The full-bridge rectifier circuit or full-wave rectifier circuit includes at least one rectifier diode.

19. The resonant converter according to claim 1, characterized in that, The resonant converter also includes a filter capacitor, which is electrically coupled to the primary circuit and / or the secondary circuit.

20. The resonant converter according to claim 1, characterized in that, The control circuit includes a primary-side drive circuit, which sends a control signal to control the switching state of the primary-side switch based on at least one of the input voltage, output voltage, and resonant current of the resonant circuit, as well as a delay time when the resonant current of the resonant circuit crosses zero.

21. The resonant converter according to claim 1, characterized in that, The delay time is adjusted according to the input voltage, output voltage, resonant current, or switching frequency.

22. The resonant converter according to claim 1, characterized in that, The primary-side switch is turned on when there is zero voltage.

23. A control method for a resonant converter, the resonant converter comprising a primary circuit, a resonant circuit, a transformer, a secondary circuit, and a control circuit, wherein the primary circuit includes at least one set of primary-side switches, the resonant circuit is electrically coupled to the primary circuit and the primary winding of the transformer, the secondary circuit includes at least one set of secondary-side rectifier elements, the rectifier elements being rectifier switches and / or rectifier diodes, and the secondary circuit is electrically coupled to the secondary winding of the transformer, characterized in that... The control method includes: The control circuit detects an input voltage received via the primary-side circuit; The control circuit detects an output voltage generated via the secondary circuit. The control circuit detects a resonant current generated via the resonant circuit. The control circuit calculates a delay time when the resonant current crosses zero. The control circuit controls the switching state of the primary-side switch based on at least one of the input voltage, output voltage, and resonant current of the resonant circuit, as well as a delay time when the resonant current of the resonant circuit crosses zero, so that the primary winding of the transformer is short-circuited or open-circuited.

24. The control method according to claim 23, characterized in that, The delay time is adjusted according to the input voltage, output voltage, resonant current, or switching frequency.

25. The control method according to claim 23, characterized in that, The control method further includes controlling the primary-side switch to turn on when there is zero voltage, as controlled by the control circuit.

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