Resonant converter and control method thereof

Abstract

The invention provides a resonant converter and a control method thereof, and relates to the technical field of power electronics. The resonant converter comprises an inversion switch unit with a plurality of power switch tubes, a resonant tank, a transformer, a rectification circuit with a first rectification tube and a second rectification tube, a sampling circuit and a controller. The sampling circuit collects an electric signal output by the rectifying circuit and outputs a feedback signal; the controller receives the feedback signal and enables the resonant converter to enter a frequency modulation and width modulation continuous control mode according to the feedback signal; in the frequency modulation and width modulation continuous control mode, the controller controls the first rectifier tube to be in a turn-off state, and adjusts the frequencies and pulse widths of the plurality of primary side control signals and the second secondary side control signals according to the feedback signal. The resonant converter enters the frequency modulation and width modulation control mode at the soft start starting stage or under the light load working condition, so that the loss can be reduced, and the output voltage ripple can be reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of power electronics, and in particular to a resonant converter and a control method thereof. Background Art

[0002] The LLC resonant converter is a high-efficiency power electronic converter based on a resonant network. It is widely used in PC power supplies (Personal Computer Power Supply), server power supplies, electric vehicle chargers, etc. due to its advantages such as high efficiency, high frequency and good electromagnetic compatibility (EMC).

[0003] In practical applications, the operating frequency of the LLC resonant converter is limited by the device, and it is difficult to achieve a wide gain adjustment. When the LLC resonant converter is working at the beginning of soft start or under light load conditions, the loop gain cannot be effectively reduced by simply increasing the operating frequency. Due to the influence of the parasitic parameters in the LLC resonant converter, the resonant cavity gain in the LLC resonant converter will become non-monotonic as the operating frequency increases, that is, when the operating frequency reaches a certain value, the gain curve will rise, causing the loop to lose its adjustment ability, and the switching loss will also increase with the increase of frequency.

[0004] At present, there are four control schemes for LLC resonant converters working in the soft start stage or light load conditions: the first adopts intermittent control mode. When the output voltage rises to the upper limit of the loop, the drive signal will be turned off and the intermittent lock time will be entered, causing the converter to stop working. When the output voltage drops to the lower limit of the loop, the drive signal will be turned on again and the intermittent opening time will be entered, causing the converter to resume working. Intermittent control switching will cause large output voltage ripple and may also affect the efficiency of the converter. The second is to set a dummy load so that the load will not be extremely light. By setting a dummy load, switching losses caused by excessive switching frequency can be avoided, but The efficiency of the whole machine will be sacrificed; the third control mode uses pulse width modulation. In this control mode, the switching frequency remains unchanged and the duty cycle is reduced. When the duty cycle is reduced to a small value, it is not easy to achieve zero voltage turn-on of the switch tube, which increases the switching loss and reduces the efficiency of the whole machine; the fourth control mode uses pulse frequency modulation. In this control mode, the output voltage gain is reduced by increasing the switching frequency. However, when the switching frequency increases to a certain extent, the influence of parasitic capacitance on the LLC resonant converter cannot be ignored. At this time, increasing the operating frequency of the resonant converter will not only not reduce the output voltage, but will increase or even lose control. In addition, as the switching frequency increases, the switching loss will also increase. When the LLC resonant converter works in the soft start stage or under light load conditions, the above four control schemes all have more or less problems such as unstable output voltage, large output voltage ripple, large loss and low efficiency.

[0005] In order to meet the requirements of stable output voltage, small output ripple, small loss and high efficiency when the resonant converter operates in the soft start stage or under light load conditions, the industry urgently needs to develop a resonant converter and its control method. Summary of the invention

[0006] As mentioned above, when the resonant converter operates in the initial stage of soft start or under light load conditions, there are problems such as unstable output voltage, large output voltage ripple, large loss and low efficiency.

[0007] The present application proposes a resonant converter, comprising:

[0008] The inverter switch unit includes a plurality of power switch tubes and is used to invert the DC input voltage at its input end into high-frequency AC power;

[0009] A resonant tank connected between two output ends of the inverter switch unit;

[0010] A transformer, comprising a primary winding, a first secondary winding and a second secondary winding, wherein the primary winding is connected in parallel with the resonant tank;

[0011] A rectifier circuit, comprising a first rectifier tube and a second rectifier tube, wherein the first end of the first rectifier tube is respectively connected to the first end of the second rectifier tube and the first output end of the rectifier circuit, the second end of the first rectifier tube is connected to the first end of the first secondary winding, the second end of the first secondary winding is respectively connected to the first end of the second secondary winding and the second output end of the rectifier circuit, the second end of the second secondary winding is connected to the second end of the second rectifier tube, and a load is connected between the first output end and the second output end of the rectifier bridge;

[0012] a sampling circuit, used for collecting the electrical signal from the rectifier circuit and outputting a feedback signal, wherein the feedback signal reflects the load condition of the load;

[0013] A controller, configured to receive the feedback signal and enable the resonant converter to enter a frequency and width modulation continuous control mode according to the feedback signal;

[0014] Among them, in the frequency and width modulation continuous control mode, the controller is used to control the first rectifier tube to be in the off state, and adjust the frequency and pulse width of multiple primary control signals and the second secondary control signal according to the feedback signal to respectively control the opening or closing of the multiple power switch tubes and the second rectifier tube.

[0015] Optionally, in the frequency and width modulation continuous control mode, as the load decreases, the controller is used to reduce the frequency of the multiple primary control signals and the frequency of the second secondary control signal according to the feedback signal, and shorten the pulse width of the multiple primary control signals and the pulse width of the second secondary control signal.

[0016] Optionally, the frequencies of the multiple primary control signals and the frequency of the second secondary control signal decrease linearly, and the pulse widths of the multiple primary control signals and the pulse width of the second secondary control signal decrease linearly.

[0017] Optionally, when the resonant converter is in a normal working state, the resonant converter enters a frequency modulation control mode;

[0018] Among them, in the frequency modulation control mode, the controller is used to adjust the frequencies of the multiple primary control signals, the first secondary control signal and the second secondary control signal according to the feedback signal to respectively control the opening or closing of the multiple power switch tubes, the first rectifier tube and the second rectifier tube.

[0019] Optionally, in the frequency and width modulation continuous control mode, in each switching cycle, there is a dead time between the multiple primary control signals, and the dead time is fixed.

[0020] Optionally, the controller includes a regulator, which generates a regulation signal according to the feedback signal, and enables the resonant converter to enter a frequency and width modulation continuous control mode when the regulation signal reaches a preset value;

[0021] Among them, in the frequency and width modulation continuous control mode, as the load decreases, the controller is used to linearly reduce the frequency of the multiple primary control signals and the frequency of the second secondary control signal according to the adjustment signal, and linearly shorten the pulse width of the multiple primary control signals and the pulse width of the second secondary control signal.

[0022] Optionally, when the feedback signal represents the output voltage of the rectifier circuit, as the output voltage increases, the regulator increases the regulation signal; or,

[0023] When the feedback signal represents the output current of the rectifier circuit, in the frequency and width modulation continuous control mode, as the load decreases, the regulator reduces the regulation signal.

[0024] Optionally, in the frequency and width modulation continuous control mode, as the load decreases, the controller is used to linearly increase the period of the carrier signal according to the adjustment signal to achieve a linear reduction in the frequencies of the multiple primary control signals and the second secondary control signal; or,

[0025] In the frequency and width modulation continuous control mode, as the load decreases, the controller is used to output the multiple primary control signals and the second secondary control signal according to the primary control signal with a preset number of switching cycles intervals of the adjustment signal to achieve a linear reduction in the frequency of the multiple primary control signals and the frequency of the second secondary control signal.

[0026] Optionally, the plurality of power switch tubes include a first power switch tube and a second power switch tube;

[0027] The first power switch tube and the second power switch tube are connected in series to form a bridge arm, and the bridge arm is connected to the input end of the inverter switch unit;

[0028] The multiple primary control signals include a first primary control signal and a second primary control signal; the first primary control signal is used to control the on or off of the first power switch tube, and the second primary control signal is used to control the on or off of the second power switch tube;

[0029] Wherein, in the frequency and width modulation continuous control mode, in each switching cycle, there is a dead time between the first primary control signal and the second primary control signal, and the dead time is fixed.

[0030] Optionally, in the frequency and width modulation continuous control mode, as the load decreases, the controller is used to delay the rising edge of the first primary control signal according to the adjustment signal to achieve a linear shortening of the pulse width of the first primary control signal, advance the falling edge of the second primary control signal to achieve a linear shortening of the pulse width of the second primary control signal, and advance the falling edge of the second secondary control signal to achieve a linear shortening of the pulse width of the second secondary control signal.

[0031] The present application also proposes a control method for a resonant converter, wherein the resonant converter comprises: an inverter switch unit having a plurality of power switch tubes, a resonant tank, a transformer, and a rectifier circuit having a first rectifier tube and a second rectifier tube, wherein two output ends of the rectifier circuit are used to connect a load; the control method comprises:

[0032] collecting an electrical signal from the rectifier circuit and outputting a feedback signal, wherein the feedback signal reflects a load condition of the load;

[0033] receiving the feedback signal, and causing the resonant converter to enter a frequency and width modulation continuous control mode according to the feedback signal;

[0034] Among them, in the frequency and width modulation continuous control mode, the controller is used to control the first rectifier tube to be in the off state, and adjust the frequency and pulse width of multiple primary control signals and the second secondary control signal according to the feedback signal to respectively control the opening or closing of the multiple power switch tubes and the second rectifier tube.

[0035] Optionally, in the frequency and width modulation continuous control mode, as the load decreases, the frequencies of the multiple primary control signals and the second secondary control signal are reduced according to the feedback signal, and the pulse widths of the multiple primary control signals and the second secondary control signal are shortened.

[0036] Optionally, the frequencies of the multiple primary control signals and the frequency of the second secondary control signal decrease linearly, and the pulse widths of the multiple primary control signals and the pulse width of the second secondary control signal decrease linearly.

[0037] Optionally, when the resonant converter is in a normal working state, the resonant converter enters a frequency modulation control mode; wherein, in the frequency modulation control mode, the frequencies of the multiple primary control signals, the first secondary control signal and the second secondary control signal are adjusted according to the feedback signal to respectively control the opening or closing of the multiple power switch tubes, the first rectifier tube and the second rectifier tube.

[0038] Optionally, a regulating signal is generated according to the feedback signal, and when the regulating signal reaches a preset value, the resonant converter enters a frequency and width modulation continuous control mode;

[0039] Among them, in the frequency and width modulation continuous control mode, as the load decreases, the frequencies of the multiple primary control signals and the frequency of the second secondary control signal are linearly reduced according to the adjustment signal, and the pulse widths of the multiple primary control signals and the pulse widths of the second secondary control signal are linearly shortened.

[0040] Optionally, in the frequency and width modulation continuous control mode, as the load decreases, the period of the carrier signal is linearly increased according to the adjustment signal to achieve a linear decrease in the frequencies of the multiple primary control signals and the second secondary control signal; or,

[0041] In the frequency and width modulation continuous control mode, as the load decreases, the multiple primary control signals and the second secondary control signal are output according to the primary control signal with a preset number of switching cycles interval according to the adjustment signal to achieve a linear reduction in the frequency of the multiple primary control signals and the frequency of the second secondary control signal.

[0042] Optionally, the plurality of power switch tubes include a first power switch tube and a second power switch tube; the first power switch tube and the second power switch tube are connected in series to form a bridge arm, and the bridge arm is connected to the input end of the inverter switch unit;

[0043] The multiple primary control signals include a first primary control signal and a second primary control signal; the first primary control signal is used to control the on or off of the first power switch tube, and the second primary control signal is used to control the on or off of the second power switch tube;

[0044] Wherein, in the frequency and width modulation continuous control mode, in each switching cycle, there is a dead time between the first primary control signal and the second primary control signal, and the dead time is fixed.

[0045] Optionally, in the frequency and width modulation continuous control mode, as the load decreases, the rising edge of the first primary control signal is delayed according to the adjustment signal to achieve a linear shortening of the pulse width of the first primary control signal, the falling edge of the second primary control signal is advanced to achieve a linear shortening of the pulse width of the second primary control signal, and the falling edge of the second secondary control signal is advanced to achieve a linear shortening of the pulse width of the second secondary control signal.

[0046] The beneficial effects of this application include at least:

[0047] The resonant converter of this embodiment includes an inverter switch unit having multiple power switch tubes, a resonant tank, a transformer, a rectifier circuit having a first rectifier tube and a second rectifier tube, a sampling circuit and a controller. The sampling circuit collects the electrical signal from the rectifier circuit and outputs a feedback signal, and the feedback signal reflects the load condition. The controller receives the feedback signal, and according to the feedback signal, the resonant converter enters a frequency modulation and width modulation continuous control mode, wherein in the frequency modulation and width modulation continuous control mode, the controller is used to control the first rectifier tube to be in an off state, and according to the feedback signal, adjusts the frequency and pulse width of multiple primary control signals and the second secondary control signal to control the opening or closing of the multiple power switch tubes and the second rectifier tube respectively, so as to achieve the purpose of optimizing efficiency, obtain a smaller controllable voltage gain, and the gain curve has good monotonicity.

[0048] There is a dead time between the multiple primary control signals, and the dead time is fixed, which can ensure zero voltage switching and reduce switching loss.

[0049] The above is a fairly broad overview of the features and technical advantages of the present application, so that the following detailed description of the present application can be better understood. The additional features and advantages of the present application will be described below, and they form the subject matter of the claims of the present application. It will be appreciated by those skilled in the art that the disclosed concepts and specific embodiments can be easily utilized as the basis for modifying or designing other structures or processes for realizing the same purpose of the present application. It will also be appreciated by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the present application as set forth in the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] In order to more fully understand the present application and its advantages, reference is now made to the following description in conjunction with the accompanying drawings, in which:

[0051] Figure 1 A schematic diagram of the structure of a resonant converter according to an embodiment of the present application is shown;

[0052] Figure 2 A schematic diagram of the structure of another resonant converter according to an embodiment of the present application is shown;

[0053] Figure 3 A timing diagram of a primary side control signal and a secondary side control signal of an embodiment of the present application is shown;

[0054] Figure 4 The timing diagram of the carrier signal, the first primary control signal, the second primary control signal, the first secondary control signal and the second secondary control signal in the frequency modulation and width modulation continuous control mode of the embodiment of the present application is shown;

[0055] Figure 5A timing diagram of a carrier signal, a first primary control signal, a second primary control signal, a first secondary control signal, and a second secondary control signal in a frequency modulation and width modulation continuous control mode according to another embodiment of the present application is shown;

[0056] Figure 6 A timing diagram of a carrier signal, a first primary control signal, a second primary control signal, a first secondary control signal, and a second secondary control signal in a frequency modulation and width modulation continuous control mode in an embodiment of the present application is shown;

[0057] Figure 7 A timing diagram of a carrier signal, a first primary control signal, a second primary control signal, a first secondary control signal, and a second secondary control signal in a frequency modulation control mode in an embodiment of the present application is shown;

[0058] Figure 8 A flow chart of a control method for a resonant converter according to an embodiment of the present application is shown.

[0059] Corresponding numerals and symbols in the different figures generally refer to corresponding parts unless otherwise indicated.The figures are drawn to clearly illustrate the relevant aspects of the various embodiments and are not necessarily drawn to scale. DETAILED DESCRIPTION

[0060] Various exemplary embodiments, features and aspects of the present invention will be described in detail below with reference to the accompanying drawings. The same reference numerals in the accompanying drawings represent elements with the same or similar functions. Although various aspects of the embodiments are shown in the accompanying drawings, the drawings are not necessarily drawn to scale unless otherwise specified.

[0061] The word "exemplary" is used herein to mean "serving as an example, embodiment or illustration". Any embodiment described herein as "exemplary" is not necessarily to be construed as being superior or better than other embodiments. The terms "first", "second", "third", etc. (if any) in the specification and claims of the present invention and the drawings are used to distinguish similar objects and are not necessarily used to describe a particular order or sequence.

[0062] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "coupled", "connected", and "connected" should be understood in a broad sense. For example, it can be an electrical connection or mutual communication, it can be a direct connection, it can also be an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0063] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can also be implemented without certain specific details. In some examples, methods, means, components and circuits well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0064] Figure 1 FIG. 1 shows a schematic diagram of the structure of a resonant converter according to an embodiment of the present application. Figure 1 As shown, the present application provides a resonant converter including an inverter switch unit 11, a resonant tank 12, a transformer, a rectifier circuit 13, a sampling circuit 14, and a control circuit 15. The inverter switch unit 11, the resonant tank 12, the transformer, and the rectifier circuit 13 constitute the topology of the resonant converter, which can be an LLC resonant converter topology or other types of resonant converter topologies, which are not listed here one by one.

[0065] The inverter switch unit 11 includes a plurality of power switch tubes, which are used to invert the DC input voltage at its input end into high-frequency AC power. The input end of the inverter switch unit 11 is connected to an input capacitor C, wherein the input capacitor C is connected to a front-stage converter to provide the DC input voltage. In other embodiments, the DC input voltage can also be provided by a DC power supply. In this embodiment, the power switch tube can be a semiconductor controllable switch such as MOS, IGBT, etc.

[0066] The resonant tank 12 includes a resonant inductor Lr, an excitation inductor Lm and a resonant capacitor Cr, and the resonant inductor Lr, the excitation inductor Lm and the resonant capacitor Cr are connected in series between the first output terminal and the second output terminal of the inverter switch unit 11. The present application does not limit the setting position and specific connection relationship of the resonant inductor Lr, the excitation inductor Lm and the resonant capacitor Cr in the resonant tank 12.

[0067] The transformer comprises a primary winding Lp, a first secondary winding Ls1 and a second secondary winding Ls2, wherein the primary winding Lp is connected in parallel with the excitation inductor Lm. In this embodiment, the excitation inductor Lm and the primary winding Lp of the transformer may be two windings or an integrated winding.

[0068] The rectifier circuit 13 includes a first rectifier tube S1 and a second rectifier tube S2, wherein the first end of the first rectifier tube S1 is connected to the first end of the second rectifier tube S2 and the first output end of the rectifier circuit 13, respectively, the second end of the first rectifier tube S1 is connected to the first end of the first secondary winding Ls1, the second end of the first secondary winding Ls1 is connected to the first end of the second secondary winding Ls2 and the second output end of the rectifier circuit 13, respectively, and the second end of the second secondary winding Ls2 is connected to the second end of the second rectifier tube S2. The rectifier circuit 13 may also include an output capacitor Co, wherein the first end of the output capacitor Co is connected to the first output end of the rectifier circuit 13, and the second end of the output capacitor Co is connected to the second output end of the rectifier circuit 13. In an embodiment, the first output end of the rectifier circuit 13 is connected to the first end of the load RL, and the second output end of the rectifier circuit 13 is connected to the second end of the load RL. In this embodiment, the first rectifier tube S1 and the second rectifier tube S2 may be synchronous rectifiers, such as semiconductor controllable switches such as MOS.

[0069] The sampling circuit 14 is used to collect the electrical signal from the rectifier circuit 13 and generate a feedback signal, wherein the feedback signal reflects the load condition of the load RL. The sampling circuit 14 is connected to the output end of the rectifier circuit 13, and can collect electrical signals such as the output voltage or output current of the rectifier circuit 13, and output a corresponding feedback signal. Specifically, when the sampling circuit 14 collects the output voltage of the rectifier circuit 13, the feedback signal represents the output voltage, and the output voltage can reflect the load condition of the load RL. For example, if the load RL decreases, the output voltage will increase, and vice versa; when the sampling circuit 14 collects the output current of the rectifier circuit 13, the feedback signal represents the output current, and the output current can reflect the load condition of the load RL. For example, if the load RL decreases, the output current will decrease, and vice versa.

[0070] The controller 15 is used to receive the feedback signal, and according to the feedback signal, the resonant converter enters the frequency-width modulation continuous control mode; wherein, in the frequency-width modulation continuous control mode, the controller 15 is used to control the first rectifier tube S1 to be in the off state, and adjust the frequency and pulse width of the multiple primary control signals and the second secondary control signal CS2 according to the feedback signal to control the opening or closing of the multiple power switch tubes and the second rectifier tube S2 respectively. In this embodiment, the controller 15 can turn off the first secondary control signal to achieve the purpose of turning off the first rectifier tube S1. In this embodiment, when the feedback signal reflects that the resonant converter is operating in the soft start start stage, light load condition or dynamic condition, the controller 15 controls the resonant converter to enter the frequency-width modulation continuous control mode.

[0071] In some embodiments, the controller 15 can determine whether the feedback signal reaches a threshold value. If the feedback signal reaches the threshold value, the controller 15 controls the resonant converter to enter a frequency-width modulation continuous control mode. Specifically, when the feedback signal represents the output voltage, the controller 15 controls the resonant converter to enter a frequency-width modulation continuous control mode when the output voltage reaches the voltage threshold. When the feedback signal represents the output current, the controller 15 controls the resonant converter to enter a frequency-width modulation continuous control mode when the output current reaches the current threshold.

[0072] The resonant converter of this embodiment can accurately control the frequency and pulse width of the multiple primary control signals and the frequency and pulse width of the second secondary control signal in the frequency and width modulation continuous control mode, thereby ensuring the stability of the switching cycle, reducing the output voltage ripple, and reducing the loss. In the frequency and width modulation continuous control mode, the controller 15 turns off the first secondary control signal to put the first rectifier tube in the off state, and the second secondary control signal operates normally, thereby achieving the purpose of optimizing efficiency.

[0073] Furthermore, in the frequency-width modulation continuous control mode, as the load decreases, the controller 15 is used to reduce the frequency of the multiple primary control signals and the frequency of the second secondary control signal CS2 and shorten the pulse width of the multiple primary control signals and the pulse width of the second secondary control signal CS2 according to the feedback signal, so as to achieve a smaller gain adjustment, and the gain curve has good monotonicity, thereby overcoming the problem that the frequency modulation control mode is easily affected by parasitic parameters in the resonant converter in the high frequency band, resulting in a non-monotonic gain curve, making it difficult to achieve a smaller gain adjustment, and increasing the switching loss, thereby reducing transformer losses and improving overall efficiency.

[0074] Furthermore, the frequencies of the multiple primary control signals and the frequency of the second secondary control signal CS2 are linearly reduced, and the pulse widths of the multiple primary control signals and the pulse widths of the second secondary control signal CS2 are linearly shortened, thereby reducing the output voltage ripple and achieving the purpose of optimizing efficiency.

[0075] Further, when the resonant converter is in a normal working state, the resonant converter enters a frequency modulation control mode; wherein, in the frequency modulation control mode, the controller 15 is used to adjust the frequencies of the multiple primary control signals, the first secondary control signal CS1, and the second secondary control signal CS2 according to the feedback signal to control the on or off of the multiple power switch tubes, the first rectifier tube S1, and the second rectifier tube S2 respectively. The multiple primary control signals can operate at a duty cycle of 50%, wherein the on time and off time of the primary control signal constitute a switching period, and the duty cycle is the ratio of the on time to the switching period.

[0076] Furthermore, under heavy load conditions, the resonant converter can also operate in a frequency modulation control mode. As the load decreases, the frequencies of the multiple primary control signals, the first secondary control signal, and the second secondary control signal gradually increase.

[0077] Furthermore, under extremely light load or no-load conditions, the resonant converter operates in a discontinuous control mode.

[0078] Furthermore, in the frequency and width modulation continuous control mode, in each switching cycle, there is a dead time between the multiple primary control signals, and the dead time is fixed, which can ensure that the corresponding power switch tube is turned on with zero voltage and reduce the turn-on loss.

[0079] Further, the controller 15 includes a regulator (not shown in the figure), which generates the adjustment signal according to the feedback signal, and when the adjustment signal reaches a preset value, the resonant converter enters the frequency and width modulation continuous control mode. The regulator can be a PID regulator, a PI regulator, etc., but is not limited thereto. In this embodiment, the regulator can be a digital regulator.

[0080] Specifically, in the frequency modulation and width modulation continuous control mode, the regulator in the controller 15 generates a regulation signal according to the feedback signal. As the load decreases, the regulation signal reaches a preset value, so that the resonant converter enters the frequency modulation and width modulation continuous control mode. At this time, the frequency of the primary side control signal and the second secondary side control signal CS2 is greater than the first frequency setting value f pfm_max In the frequency and width modulation continuous control mode, as the load RL decreases, the controller 15 linearly reduces the frequency of the plurality of primary control signals and the frequency of the second secondary control signal CS2 according to the adjustment signal, for example, the frequency is reduced from the second set value f burst_max Down to the third setting value f burst_min , and linearly shortening the pulse widths of the plurality of primary control signals and the pulse width of the second secondary control signal, for example, by reducing the pulse width from the first pulse width W to the second pulse width W. burst_max Shorten to the second pulse width W burst_min By linearly reducing the frequencies of the multiple primary control signals and the frequencies of the second secondary control signal CS2 and shortening the pulse widths of the multiple primary control signals and the pulse widths of the second secondary control signal CS2, a smaller gain adjustment is achieved, and the gain curve has good monotonicity, which reduces transformer losses and improves overall efficiency. In addition, in the frequency-width modulation continuous control mode, as the load RL increases, the controller 15 linearly increases the frequencies of the multiple primary control signals and the frequencies of the second secondary control signal CS2 according to the adjustment signal, for example, by increasing the frequency from the third set value f burst_min Increase to the second set value f burst_max, and linearly extending the pulse widths of the plurality of primary control signals and the pulse width of the second secondary control signal CS2, for example, by increasing the pulse width from the second pulse width W burst_min Extend to the first pulse width W burst_max .

[0081] In this embodiment, in the frequency and width modulation continuous control mode, as the load RL continues to increase, the controller 15 continues to linearly increase the frequencies of the multiple primary control signals and the frequency of the second secondary control signal CS2 according to the adjustment signal, when the frequencies of the multiple primary control signals and the frequency of the second secondary control signal CS2 are greater than the second set value f burst_max , the resonant converter enters the normal operating mode, that is, it exits the frequency and width modulation continuous control mode and enters the frequency modulation control mode.

[0082] Further, when the feedback signal represents the output voltage of the rectifier circuit, as the output voltage increases, the regulator increases the regulation signal; or,

[0083] When the feedback signal represents the output current of the rectifier circuit, in the frequency and width modulation continuous control mode, as the load decreases, the regulator reduces the regulation signal.

[0084] Furthermore, the controller 15 further includes a period calculation unit and a duty cycle calculation unit. The period calculation unit is used to linearly adjust the frequency of the plurality of primary control signals and the frequency of the second secondary control signal CS2 according to the adjustment signal. The duty cycle calculation unit is used to adjust the pulse width of the plurality of primary control signals and the pulse width of the second secondary control signal according to the adjustment signal.

[0085] In the frequency modulation and width modulation continuous control mode, the controller 15 is used to linearly adjust the period of the carrier signal according to the adjustment signal to achieve linear adjustment of the frequencies of the multiple primary control signals and the second secondary control signal. Specifically, in the frequency modulation and width modulation continuous control mode, as the load RL decreases, the controller 15 linearly increases the period T of the carrier signal according to the adjustment signal. burst , the carrier signal is used to linearly reduce the frequencies of the multiple primary control signals and the frequency of the second secondary control signal CS2; as the load RL increases, the controller 15 linearly reduces the period T of the carrier signal according to the adjustment signal burst, the carrier signal is used to linearly increase the frequencies of the multiple primary control signals and the frequency of the second secondary control signal CS2. The resonant converter of this embodiment can adjust the frequencies and pulse widths of the multiple primary control signals and the frequencies and pulse widths of the second secondary control signal CS2 in the frequency modulation and width modulation continuous control mode, and can obtain a smaller controllable voltage gain, with a gain curve having good monotonicity, reducing output voltage ripple, reducing losses, and improving overall efficiency.

[0086] Further, the controller 15 is used to output the multiple primary control signals and the second secondary control signal CS2 according to the primary control signal of the adjustment signal at intervals of a preset number of switching cycles to achieve linear adjustment of the frequencies of the multiple primary control signals and the second secondary control signal CS2, wherein the preset number of switching cycles can be one or more switching cycles. Specifically, in the frequency-width modulation continuous control mode, as the load RL decreases, the controller 15 outputs the multiple primary control signals and the second secondary control signal CS2 according to the primary control signal of the adjustment signal at intervals of 1 switching cycle, 2 switching cycles, and up to the preset number of switching cycles, so that the frequencies of the multiple primary control signals and the second secondary control signal are linearly reduced. In this process, the controller 15 does not adjust the period T of the carrier signal. burst , that is, the period T of the carrier signal burst unchanged; as the load RL increases, the controller 15 outputs the multiple primary control signals and the second secondary control signal CS2 according to the primary control signal of the adjustment signal at intervals of a preset number of switching cycles until 2 switching cycles and 1 switching cycle, so that the frequency of the multiple primary control signals and the frequency of the second secondary control signal increase linearly. The resonant converter of this embodiment adjusts the frequency and pulse width of the multiple primary control signals and the frequency and pulse width of the second secondary control signal CS2 in the frequency and width modulation continuous control mode, and can obtain a smaller controllable voltage gain, with a gain curve having good monotonicity, reducing output voltage ripple, reducing losses, and improving overall efficiency.

[0087] Continue to refer to Figure 1 The inverter switch unit 11 includes a plurality of power switch tubes including a first power switch tube Q1 and a second power switch tube Q2. The first power switch tube Q1 and the second power switch tube Q2 are connected in series to form a bridge arm, and the bridge arm is connected to the input end of the inverter switch unit 11. Specifically, one end of the first power switch tube Q1 is connected to the first input end of the inverter switch unit, the other end of the first power switch tube Q1 and one end of the second power switch tube Q2 are connected to the first output end of the inverter switch unit, and the other end of the second power switch tube Q2 is respectively connected to the second input end and the second output end of the inverter switch unit.

[0088] The sampling circuit 14 collects the output voltage of the rectifier circuit and generates a feedback signal representing the output voltage.

[0089] In the frequency modulation and width modulation continuous control mode, the controller 15 receives the feedback signal, and turns off the first primary control signal CQ1 according to the feedback signal, and outputs the second primary control signal CQ2, the first secondary control signal CS1 and the second secondary control signal CS2 according to the feedback signal. Specifically, the controller 15 can output the first primary control signal CQ1, the second primary control signal CQ2, the second secondary control signal CS2, and turn off the first secondary control signal CS1 to control the opening or closing of the first power switch tube Q1, the second power switch tube Q2 and the second rectifier tube S2 respectively.

[0090] Further, in the frequency and width modulation continuous control mode, as the load RL decreases, the controller 15 is used to linearly reduce the frequency of the first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal CS2 according to the feedback signal, and linearly shorten the pulse width of the first primary control signal CQ1, the pulse width of the second primary control signal CQ2 and the pulse width of the second secondary control signal CS2.

[0091] Figure 3 The timing diagram of the primary side control signal and the secondary side control signal of the embodiment of the present application is shown. Figure 1 and Figure 3 In the frequency and width modulation continuous control mode, in each switching cycle, the controller 15 turns off the first secondary control signal CS1 to control the first rectifying tube S1 to be in the off state, and outputs the first primary control signal CQ1 to control the first power switch tube Q1 to turn on. After the first power switch tube Q1 is turned off, the second primary control signal CQ2 and the second secondary control signal CS2 are output to control the second power switch tube Q2 to turn on and the second rectifier tube S2 to turn on. In each switching cycle, there is a dead time between the first primary control signal CQ1 and the second primary control signal CQ2, and the dead time is fixed, that is, there is a dead time Tdt between the falling edge of the first primary control signal CQ1 and the rising edge of the second primary control signal CQ2. The dead time Tdt remains unchanged, which can ensure that the second power switch tube Q2 is turned on with zero voltage and reduce the turn-on loss.

[0092] In the frequency and width modulation continuous control mode, the controller 15 turns off the first secondary control signal CS1 to control the first rectifier tube S1 to be in the off state, and outputs the first primary control signal CQ1 to control the first power switch tube Q1 to turn on, so that the input voltage charges the resonance tank 11 through the first power switch tube Q1, avoiding the phenomenon of energy backflow on the secondary side of the transformer, and improving efficiency; and after the controller 15 controls the first power switch tube Q1 to turn off, it outputs the second primary control signal CQ2 and the second secondary control signal CS2 to control the second power switch tube Q2 to turn on and the second rectifier tube S2 to turn on, respectively, wherein the rising edge time of the second primary control signal CQ2 and the rising edge time of the second secondary control signal CS2 can be the same, and the energy stored in the resonance tank 11 is transferred to the rectifier circuit through the second secondary winding Ls2, that is, the energy is output at the output end of the rectifier circuit 13 through the second secondary winding Ls2 and the second rectifier tube S2, so as to achieve the purpose of optimizing efficiency.

[0093] Figure 4 The timing diagram of the carrier signal, the first primary control signal, the second primary control signal, the first secondary control signal and the second secondary control signal in the frequency modulation and width modulation continuous control mode of the embodiment of the present application is shown. Figure 1 and Figure 4 The controller 15 is used to linearly adjust the period T of the carrier signal according to the adjustment signal. burst To achieve linear regulation of the frequencies of the first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal CS2. Specifically, in the frequency modulation and width modulation continuous control mode, as the load RL decreases, the controller 15 linearly increases the period T of the carrier signal according to the regulation signal. burst , that is, the PRD value, and the carrier signal is used to linearly reduce the frequencies of the first primary control signal CQ1 and the second primary control signal CQ2 and the frequency of the second secondary control signal CS2. By linearly reducing the frequencies of the first primary control signal CQ1 and the second primary control signal CQ2 and the frequency of the second secondary control signal CS2, a smaller gain adjustment is achieved, and the gain curve has good monotonicity, which reduces transformer loss and improves overall efficiency.

[0094] In some embodiments, in the frequency modulation and width modulation continuous control mode, the controller 15 can calculate the duty cycle of the first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal according to the carrier signal. Specifically, in the frequency modulation and width modulation continuous control mode, as the load RL decreases, the controller 15 linearly increases the period T of the carrier signal according to the adjustment signal. burstThe carrier signal is used to shorten the pulse width of the first primary control signal CQ1, the pulse width of the second primary control signal CQ2, and the pulse width of the second secondary control signal CS2, thereby achieving a smaller gain adjustment, and the gain curve has good monotonicity, reducing transformer losses and improving overall efficiency.

[0095] In this embodiment, the controller can also calculate the duty cycle of the first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal according to the adjustment signal. Specifically, in the frequency-width modulation continuous control mode, as the load RL decreases, the controller 15 shortens the pulse width of the first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal CS2 according to the adjustment signal, and shortens the pulse width of the first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal CS2 to achieve a smaller gain adjustment, and the gain curve has good monotonicity, which reduces transformer loss and improves overall efficiency.

[0096] The resonant converter of this embodiment linearly reduces the frequency of the first primary control signal CQ1 and the second primary control signal CQ2 and the frequency of the second secondary control signal CS2 and linearly shortens the pulse width of the first primary control signal CQ1 and the second primary control signal CQ2 and the pulse width of the second secondary control signal CS2 in the frequency and width modulation continuous control mode, so as to obtain a smaller controllable voltage gain, have a gain curve with good monotonicity, reduce output voltage ripple, reduce losses, and improve overall efficiency.

[0097] Figure 6 The timing diagram of the carrier signal, the first primary control signal, the second primary control signal, the first secondary control signal and the second secondary control signal in the frequency modulation and width modulation continuous control mode of the embodiment of the present application is shown. Figure 1 and Figure 6 In the frequency and width modulation continuous control mode, as the load RL decreases, the controller 15 can delay the rising edge of the first primary control signal CQ1 according to the adjustment signal to achieve a linear shortening of the pulse width of the first primary control signal CQ1, advance the falling edge of the second primary control signal CQ2 to achieve a linear shortening of the pulse width of the second primary control signal CQ2, and advance the falling edge of the second secondary control signal CS2 to achieve a linear shortening of the pulse width of the second secondary control signal CS2, and at the same time turn off the first secondary control signal CS1 to optimize efficiency.

[0098] Figure 7The timing diagram of the carrier signal, the first primary control signal, the second primary control signal, the first secondary control signal and the second secondary control signal in the frequency modulation control mode of the embodiment of the present application is shown. Figure 1 and Figure 7 When the resonant converter is in a normal working state, the resonant converter enters the frequency modulation control mode. In the frequency modulation control mode, the first primary control signal CQ1 and the second primary control signal CQ2 can operate at a 50% duty cycle, and the controller 15 adjusts the frequency of the first primary control signal CQ1 and the second primary control signal CQ2 and the frequency of the second primary control signal CQ2 according to the feedback signal.

[0099] Furthermore, the controller 15 controls the second power switch tube Q2 to be turned off and leaves enough dead time to ensure that the current damping oscillation of the resonant slot 11 decays to close to 0A when the first primary control signal CQ1 is output in the next switching cycle, so that the stress of turning on the first power switch tube Q1 is less, the switching cycle is stabilized, and sudden increase or decrease of energy is avoided, which is beneficial to the balance relationship between the output current and the output voltage, making the output voltage more stable.

[0100] Figure 5 The timing diagram of the carrier signal, the first primary control signal, the second primary control signal, the first secondary control signal and the second secondary control signal in the frequency modulation and width modulation continuous control mode of another embodiment of the present application is shown. Figure 1 and Figure 5 , in the frequency modulation and width modulation continuous control mode, the controller 15 is used to output the first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal CS2 according to the primary control signal of the adjustment signal at intervals of a preset number of switching cycles to achieve linear adjustment of the frequencies of the first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal CS2. Specifically, in the frequency modulation and width modulation continuous control mode, as the load RL decreases, the controller 15 sequentially intervals 1 switching cycle, 2 switching cycles until a preset number of switching cycles according to the adjustment signal, so that the frequencies of the first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal CS2 are linearly reduced, wherein the controller 15 does not adjust the period T of the carrier signal according to the adjustment signal. burst , that is, the period T of the carrier signal burst The first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal CS2 are output by the primary control signal at intervals of a preset number of switching cycles, so as to achieve a smaller gain adjustment, and the gain curve has good monotonicity, thereby reducing transformer loss and improving overall efficiency.

[0101] Combination Figure 1 and Figure 5 The controller 15 adjusts the pulse widths of the first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal CS2 according to the adjustment signal. As the load RL decreases, the controller 15 linearly shortens the pulse widths of the first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal CS2 according to the adjustment signal.

[0102] The resonant converter of this embodiment can obtain a smaller controllable voltage gain, has a gain curve with good monotonicity, reduces output voltage ripple, reduces losses, and improves overall efficiency.

[0103] Figure 2 FIG. 2 shows a schematic diagram of the structure of another resonant converter according to an embodiment of the present application. Figure 2 As shown, the multiple power switch tubes of the inverter switch unit 21 include a third power switch tube Q21, a fourth power switch tube Q22, a fifth power switch tube Q23 and a sixth power switch tube Q24.

[0104] One end of the third power switch tube Q21 is respectively connected to one end of the sixth power switch tube Q24 and the first input end of the inverter switch unit, the other end of the third power switch tube Q21 is respectively connected to one end of the fourth power switch tube Q22 at the first output end of the inverter switch unit, the other end of the sixth power switch tube Q24 is respectively connected to one end of the fifth power switch tube Q23 at the second output end of the inverter switch unit, and the other end of the fourth power switch tube Q22 is respectively connected to the other end of the fifth power switch tube Q23 and the second input end of the inverter switch unit.

[0105] The sampling circuit 24 collects the output current of the rectifier circuit and generates a feedback signal representing the output current.

[0106] The controller 25 receives the feedback signal, and according to the feedback signal, causes the resonant converter to enter the frequency and width modulation continuous control mode. In the frequency and width modulation continuous control mode, the controller 25 outputs the third primary control signal CQ21, the fourth primary control signal CQ22, the fifth primary control signal CQ23, the sixth primary control signal CQ24, and the second secondary control signal CS2, and turns off the first secondary control signal CS1 to control the first rectifier tube S1 to be in the off state; the third primary control signal CQ21 is used to control the opening or closing of the third power switch tube Q21, the fourth primary control signal CQ22 is used to control the opening or closing of the fourth power switch tube Q22, the fifth primary control signal CQ23 is used to control the opening or closing of the fifth power switch tube Q23, and the sixth primary control signal CQ24 is used to control the opening or closing of the sixth power switch tube Q24; the second secondary control signal CS2 is used to control the opening or closing of the second rectifier tube S2.

[0107] In the frequency and width modulation continuous control mode, in each switching cycle, the controller 25 can first output the same third primary control signal CQ21 and the fifth primary control signal CQ23 to simultaneously turn on the third power switch tube Q21 and the fifth power switch tube Q23, and turn off the first secondary control signal CS1 to control the first rectifier tube S1 to be in the off state, and then output the same fourth primary control signal CQ22 and the sixth primary control signal CQ24 to control the fourth power switch tube Q22 and the sixth power switch tube Q24 to turn on after the controller 25 controls the third power switch tube Q21 and the fifth power switch tube Q23 to turn off, and output the second secondary control signal CS2 to control the second rectifier tube S2 to turn on. There is a dead time between the third primary control signal CQ21 and the fourth primary control signal CQ22, and the dead time is fixed, which can ensure that the fourth power switch tube Q22 and the sixth power switch tube Q24 are turned on at zero voltage, thereby reducing the turn-on loss.

[0108] In this embodiment, the waveforms of the third primary control signal CQ21, the fourth primary control signal CQ22, the fifth primary control signal CQ23 and the sixth primary control signal CQ24 as well as the first secondary control signal CS1 and the second secondary control signal CS2 can be Figures 3 to 6, wherein the waveforms of the third primary control signal CQ21 and the fifth primary control signal CQ23 can refer to the waveform of the first primary control signal CQ1, and the waveforms of the fourth primary control signal CQ22 and the sixth primary control signal CQ24 can refer to the waveform of the second primary control signal CQ2. In the frequency modulation and width modulation continuous control mode, as the load changes, the feedback signal changes, which in turn causes the adjustment signal to change. The controller 25 provides the third primary control signal CQ21, the fourth primary control signal CQ22, the fifth primary control signal CQ23 and the sixth primary control signal CQ24 as well as the first secondary control signal CS1 and the second secondary control signal CS2 according to the adjustment signal. The manner in which the controller 25 provides the third primary control signal CQ21, the fourth primary control signal CQ22, the fifth primary control signal CQ23 and the sixth primary control signal CQ24 as well as the first secondary control signal CS1 and the second secondary control signal CS2 according to the adjustment signal can refer to Figure 1 and Figures 3 to 6 The description will not be repeated here.

[0109] The resonant converter of this embodiment can effectively solve the problems of large output voltage ripple, low efficiency and large loss in the initial stage of soft start, light load conditions or dynamic conditions, and can enter the frequency and width modulation continuous control mode in the initial stage of soft start, light load conditions or dynamic conditions, and can achieve smaller gain adjustment. The gain curve has good monotonicity, reduces output voltage ripple, reduces transformer loss, switching loss, improves efficiency, and has wide application value.

[0110] Figure 8 FIG. 1 is a flow chart showing a control method of a resonant converter according to an embodiment of the present application. Figure 8 As shown, the control method of the resonant converter of the present application is an effective method to solve the problems of large output voltage ripple, low efficiency and large loss when the resonant converter operates in the initial stage of soft start, light load conditions or dynamic conditions. It does not require additional circuits and costs, can reduce losses, and can greatly reduce output ripple, and has wide application value.

[0111] Combination Figure 1 and Figure 8 The resonant converter includes an inverter switch unit 11 having multiple power switch tubes, a resonant tank 12, a transformer, and a rectifier circuit 13 having a first rectifier tube S1 and a second rectifier tube S2. The two output ends of the rectifier circuit 13 are used to connect to the load RL. The circuit structure and connection method of the resonant converter can refer to the aforementioned Figure 1 The description will not be repeated here.

[0112] The control method comprises:

[0113] Step S81: collecting an electrical signal from the rectifier circuit and outputting a feedback signal, wherein the feedback signal reflects the load condition of the load.

[0114] Specifically, if Figure 1As shown, the sampling circuit 14 is used to collect the electrical signal from the rectifier circuit 13 and generate a feedback signal, wherein the feedback signal reflects the load condition of the load RL. The sampling circuit 14 is connected to the output end of the rectifier circuit 13, and can collect electrical signals such as the output voltage or output current of the rectifier circuit 13, and output a corresponding feedback signal.

[0115] Step S82: Receive the feedback signal, and enable the resonant converter to enter a frequency-width modulation continuous control mode according to the feedback signal; wherein, in the frequency-width modulation continuous control mode, the controller is used to control the first rectifier tube to be in an off state, and simultaneously adjust the frequency and pulse width of multiple primary control signals and the second secondary control signal according to the feedback signal to respectively control the opening or closing of the multiple power switch tubes and the second rectifier tube.

[0116] Specifically, Figure 1 As shown, the controller 15 is used to receive the feedback signal, and according to the feedback signal, the resonant converter enters the frequency-width modulation continuous control mode; wherein, in the frequency-width modulation continuous control mode, the controller 15 is used to control the first rectifier tube S1 to be in the off state, and adjust the frequency and pulse width of the plurality of primary control signals and the second secondary control signal CS2 according to the feedback signal to control the opening or closing of the plurality of power switch tubes and the second rectifier tube S2 respectively. In this embodiment, the controller 15 can turn off the first secondary control signal to achieve the purpose of turning off the first rectifier tube S1.

[0117] The control method of the resonant converter of this embodiment can accurately control the frequency and pulse width of the multiple primary control signals and the frequency and pulse width of the second secondary control signal in the frequency and width modulation continuous control mode, thereby ensuring the stability of the switching cycle, reducing the output voltage ripple, and reducing the loss. In the frequency and width modulation continuous control mode, the first secondary control signal is stopped from being output, and the second secondary control signal is normal, thereby achieving the purpose of optimizing efficiency.

[0118] Further, in the frequency and width modulation continuous control mode, as the load decreases, the frequencies of the multiple primary control signals and the second secondary control signal are reduced according to the feedback signal, and the pulse widths of the multiple primary control signals and the second secondary control signal are shortened.

[0119] Specifically, Figure 4 and 5As shown, in the frequency and width modulation continuous control mode, as the load decreases, the controller 15 is used to reduce the frequency of the multiple primary control signals and the frequency of the second secondary control signal CS2 according to the feedback signal, and shorten the pulse width of the multiple primary control signals and the pulse width of the second secondary control signal CS2, so as to achieve a smaller gain adjustment, and the gain curve has good monotonicity, thereby reducing transformer losses and improving overall efficiency.

[0120] Furthermore, the frequencies of the multiple primary control signals and the frequency of the second secondary control signal CS2 are linearly reduced, and the pulse widths of the multiple primary control signals and the pulse widths of the second secondary control signal CS2 are linearly shortened, thereby reducing the output voltage ripple and achieving the purpose of optimizing efficiency.

[0121] Further, when the resonant converter is in a normal working state, the resonant converter enters a frequency modulation control mode; wherein, in the frequency modulation control mode, the frequencies of the multiple primary control signals, the first secondary control signal, and the second secondary control signal are adjusted according to the feedback signal to respectively control the opening or closing of the multiple power switch tubes, the first rectifier tube, and the second rectifier tube.

[0122] Specifically, Figure 7 As shown, in the frequency modulation control mode, the controller 15 is used to adjust the frequencies of the multiple primary control signals, the first secondary control signal CS1 and the second secondary control signal CS2 according to the feedback signal to control the on or off of the multiple power switch tubes, the first rectifier tube S1 and the second rectifier tube S2 respectively. The multiple primary control signals can operate at a duty cycle of 50%, wherein the on time and off time of the primary control signal constitute a switching period, and the duty cycle is the ratio of the on time to the switching period.

[0123] Further, an adjustment signal is generated according to the feedback signal, and when the adjustment signal reaches a preset value, the resonant converter enters a frequency and width modulation continuous control mode;

[0124] Among them, in the frequency and width modulation continuous control mode, as the load decreases, the frequencies of the multiple primary control signals and the frequency of the second secondary control signal are linearly reduced according to the adjustment signal, and the pulse widths of the multiple primary control signals and the pulse widths of the second secondary control signal are linearly shortened.

[0125] Specifically, in the frequency modulation and width modulation continuous control mode, the regulator in the controller 15 generates a regulation signal according to the feedback signal. As the load decreases, the regulation signal reaches a preset value, so that the resonant converter enters the frequency modulation and width modulation continuous control mode. At this time, the frequency of the primary control signal and the second secondary control signal CS2 is greater than the first set value fpfm_max In the frequency and width modulation continuous control mode, as the load RL decreases, the controller 15 linearly reduces the frequency of the plurality of primary control signals and the frequency of the second secondary control signal CS2 according to the adjustment signal, for example, the frequency is reduced from the second set value f burst_max Down to the third setting value f burst_min , and linearly shortening the pulse widths of the plurality of primary control signals and the pulse width of the second secondary control signal, for example, by reducing the pulse width from the first pulse width W to the second pulse width W. burst_max Shorten to the second pulse width W burst_min By linearly reducing the frequencies of the multiple primary control signals and the frequency of the second secondary control signal CS2 and shortening the pulse widths of the multiple primary control signals and the pulse width of the second secondary control signal CS2, a smaller gain adjustment is achieved, and the gain curve has good monotonicity, which reduces transformer losses and improves overall efficiency.

[0126] Further, in the frequency and width modulation continuous control mode, as the load decreases, the period of the carrier signal is linearly increased according to the adjustment signal to achieve a linear decrease in the frequencies of the multiple primary control signals and the second secondary control signal; or,

[0127] In the frequency and width modulation continuous control mode, as the load decreases, the multiple primary control signals and the second secondary control signal are output according to the primary control signal with a preset number of switching cycles interval according to the adjustment signal to achieve a linear reduction in the frequency of the multiple primary control signals and the frequency of the second secondary control signal.

[0128] Specifically, combined Figure 1 and Figure 4 In the frequency and width modulation continuous control mode, as the load RL decreases, the controller 15 linearly increases the period T of the carrier signal according to the adjustment signal. burst , that is, the PRD value, and the carrier signal is used to linearly reduce the frequencies of the first primary control signal CQ1 and the second primary control signal CQ2 and the frequency of the second secondary control signal CS2. By linearly reducing the frequencies of the first primary control signal CQ1 and the second primary control signal CQ2 and the frequency of the second secondary control signal CS2, a smaller gain adjustment is achieved, and the gain curve has good monotonicity, which reduces transformer loss and improves overall efficiency.

[0129] Combination Figure 1 and Figure 5In the frequency modulation and width modulation continuous control mode, as the load RL decreases, the controller 15 sequentially intervals 1 switching cycle, 2 switching cycles, and up to a preset number of switching cycles according to the adjustment signal, so that the frequencies of the first primary control signal CQ1, the second primary control signal CQ2, and the second secondary control signal CS2 are linearly reduced, wherein the controller 15 does not adjust the period T of the carrier signal according to the adjustment signal. burst , that is, the period T of the carrier signal burst The first primary control signal CQ1, the second primary control signal CQ2 and the second secondary control signal CS2 are output by the primary control signal at intervals of a preset number of switching cycles, so as to achieve a smaller gain adjustment, and the gain curve has good monotonicity, thereby reducing transformer loss and improving overall efficiency.

[0130] Further, the plurality of power switch tubes include a first power switch tube and a second power switch tube; the first power switch tube and the second power switch tube are connected in series to form a bridge arm, and the bridge arm is connected to the input end of the inverter switch unit;

[0131] The multiple primary control signals include a first primary control signal and a second primary control signal; the first primary control signal is used to control the on or off of the first power switch tube, and the second primary control signal is used to control the on or off of the second power switch tube;

[0132] Wherein, in the frequency and width modulation continuous control mode, in each switching cycle, there is a dead time between the first primary control signal and the second primary control signal, and the dead time is fixed.

[0133] Specifically, Figure 1 and Figure 3 As shown, the inverter switch unit 11 includes a plurality of power switch tubes including a first power switch tube Q1 and a second power switch tube Q2. The first power switch tube Q1 and the second power switch tube Q2 are connected in series to form a bridge arm, and the bridge arm is connected to the input end of the inverter switch unit. Specifically, one end of the first power switch tube Q1 is connected to the first input end of the inverter switch unit, the other end of the first power switch tube Q1 and one end of the second power switch tube Q2 are connected to the first output end of the inverter switch unit, and the other end of the second power switch tube Q2 is respectively connected to the second input end and the second output end of the inverter switch unit.

[0134] In the frequency and width modulation continuous control mode, the controller 15 receives the feedback signal, turns off the first primary control signal CQ1 according to the feedback signal, and outputs the second primary control signal CQ2, the first secondary control signal CS1 and the second secondary control signal CS2 according to the feedback signal to respectively control the opening or closing of the first power switch tube Q1, the second power switch tube Q2 and the second rectifier tube S2.

[0135] In the frequency and width modulation continuous control mode, in each switching cycle, the controller 15 turns off the first secondary control signal CS1 to control the first rectifying tube S1 to be in the off state, and outputs the first primary control signal CQ1 to control the first power switch tube Q1 to turn on. After the first power switch tube Q1 is turned off, the second primary control signal CQ2 and the second secondary control signal CS2 are output to respectively control the second power switch tube Q2 to turn on and the second rectifier tube S2 to turn on, wherein the rising edge time of the second primary control signal CQ2 and the rising edge time of the second secondary control signal CS2 can be the same. In each switching cycle, there is a dead time between the first primary control signal CQ1 and the second primary control signal CQ2, and the dead time is fixed, that is, there is a dead time Tdt between the falling edge of the first primary control signal CQ1 and the rising edge of the second primary control signal CQ2, and the dead time Tdt remains unchanged, which can ensure that the second power switch tube Q2 is turned on with zero voltage, thereby reducing the turn-on loss. If the dead time between the first primary control signal CQ1 and the second primary control signal CQ2 is too large, when the current drops after the first power switch tube Q1 is turned off, the current will reverse and flow through the body diode of the first power switch tube Q1 again. At this time, turning on the second power switch tube Q2 will cause switching loss caused by the reverse recovery of the body diode of the first power switch tube Q1.

[0136] Further, combined with Figure 1 and Figure 6 In the frequency and width modulation continuous control mode, as the load RL decreases, the controller 15 can delay the rising edge of the first primary control signal CQ1 according to the adjustment signal to achieve a linear shortening of the pulse width of the first primary control signal CQ1, advance the falling edge of the second primary control signal CQ2 to achieve a linear shortening of the pulse width of the second primary control signal CQ2, and advance the falling edge of the second secondary control signal CS2 to achieve a linear shortening of the pulse width of the second secondary control signal CS2, and at the same time turn off the first secondary control signal CS1 to optimize efficiency.

[0137] The control method of the resonant converter of this embodiment has low dependence on hardware, no need to add additional lines and costs, and multiple primary control signals and second secondary control signals are easy to adjust, with wide applicability and high operability. The frequency and pulse width are both precisely controlled by the closed loop, ensuring the stability of the switching cycle, reducing output voltage ripple, reducing transformer loss, switching loss, and improving efficiency, and has wide application value.

[0138] Although the embodiments of the present application and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the application as defined by the appended claims.

[0139] In addition, the scope of the present application is not limited to the specific embodiments of the processes, machines, manufactures, material compositions, modes, methods, and steps described in this specification. Those skilled in the art will readily understand from the disclosure of the present application that, according to the present application, currently existing or later to be developed processes, machines, manufactures, material compositions, modes, methods, or steps that perform substantially the same functions or achieve substantially the same results as the corresponding embodiments described herein may be utilized. Therefore, it is intended that the appended claims include such processes, machines, manufactures, material compositions, modes, methods, or steps within their scope.

Claims

1. A resonant converter, characterized in that: include: The inverter switch unit includes a plurality of power switch tubes and is used to invert the DC input voltage at its input end into high-frequency AC power; A resonant tank connected between two output ends of the inverter switch unit; A transformer, comprising a primary winding, a first secondary winding and a second secondary winding, wherein the primary winding is connected in parallel with the resonant tank; A rectifier circuit, comprising a first rectifier tube and a second rectifier tube, wherein the first end of the first rectifier tube is respectively connected to the first end of the second rectifier tube and the first output end of the rectifier circuit, the second end of the first rectifier tube is connected to the first end of the first secondary winding, the second end of the first secondary winding is respectively connected to the first end of the second secondary winding and the second output end of the rectifier circuit, the second end of the second secondary winding is connected to the second end of the second rectifier tube, and a load is connected between the first output end and the second output end of the rectifier bridge; a sampling circuit, used for collecting the electrical signal from the rectifier circuit and outputting a feedback signal, wherein the feedback signal reflects the load condition of the load; A controller, configured to receive the feedback signal and enable the resonant converter to enter a frequency and width modulation continuous control mode according to the feedback signal; Among them, in the frequency and width modulation continuous control mode, the controller is used to control the first rectifier tube to be in the off state, and adjust the frequency and pulse width of multiple primary control signals and the second secondary control signal according to the feedback signal to respectively control the opening or closing of the multiple power switch tubes and the second rectifier tube.

2. The resonant converter according to claim 1, characterized in that: In the frequency and width modulation continuous control mode, as the load decreases, the controller is used to reduce the frequency of the multiple primary control signals and the frequency of the second secondary control signal according to the feedback signal, and shorten the pulse width of the multiple primary control signals and the pulse width of the second secondary control signal.

3. The resonant converter according to claim 2, characterized in that: The frequencies of the plurality of primary control signals and the frequency of the second secondary control signal are linearly reduced, and the pulse widths of the plurality of primary control signals and the pulse width of the second secondary control signal are linearly shortened.

4. The resonant converter according to claim 1, characterized in that: When the resonant converter is in a normal working state, the resonant converter enters a frequency modulation control mode; Among them, in the frequency modulation control mode, the controller is used to adjust the frequencies of the multiple primary control signals, the first secondary control signal and the second secondary control signal according to the feedback signal to respectively control the opening or closing of the multiple power switch tubes, the first rectifier tube and the second rectifier tube.

5. The resonant converter according to claim 1, characterized in that: In the frequency and width modulation continuous control mode, in each switching cycle, there is a dead time between the multiple primary side control signals, and the dead time is fixed.

6. The resonant converter according to claim 1, characterized in that: The controller includes a regulator, which generates a regulation signal according to the feedback signal, and when the regulation signal reaches a preset value, causes the resonant converter to enter a frequency and width modulation continuous control mode; Among them, in the frequency and width modulation continuous control mode, as the load decreases, the controller is used to linearly reduce the frequency of the multiple primary control signals and the frequency of the second secondary control signal according to the adjustment signal, and linearly shorten the pulse width of the multiple primary control signals and the pulse width of the second secondary control signal.

7. The resonant converter according to claim 6, characterized in that: When the feedback signal represents the output voltage of the rectifier circuit, as the output voltage increases, the regulator increases the regulation signal; or, When the feedback signal represents the output current of the rectifier circuit, in the frequency and width modulation continuous control mode, as the load decreases, the regulator reduces the regulation signal.

8. The resonant converter according to claim 6, characterized in that: In the frequency and width modulation continuous control mode, as the load decreases, the controller is used to linearly increase the period of the carrier signal according to the adjustment signal to achieve a linear decrease in the frequencies of the multiple primary control signals and the second secondary control signal; or, In the frequency and width modulation continuous control mode, as the load decreases, the controller is used to output the multiple primary control signals and the second secondary control signal according to the primary control signal with a preset number of switching cycles intervals of the adjustment signal to achieve a linear reduction in the frequency of the multiple primary control signals and the frequency of the second secondary control signal.

9. The resonant converter according to claim 6, characterized in that: The multiple power switch tubes include a first power switch tube and a second power switch tube; The first power switch tube and the second power switch tube are connected in series to form a bridge arm, and the bridge arm is connected to the input end of the inverter switch unit; The multiple primary control signals include a first primary control signal and a second primary control signal; the first primary control signal is used to control the on or off of the first power switch tube, and the second primary control signal is used to control the on or off of the second power switch tube; Wherein, in the frequency and width modulation continuous control mode, in each switching cycle, there is a dead time between the first primary control signal and the second primary control signal, and the dead time is fixed.

10. The resonant converter according to claim 9, characterized in that: In the frequency and width modulation continuous control mode, as the load decreases, the controller is used to delay the rising edge of the first primary control signal according to the adjustment signal to achieve a linear shortening of the pulse width of the first primary control signal, advance the falling edge of the second primary control signal to achieve a linear shortening of the pulse width of the second primary control signal, and advance the falling edge of the second secondary control signal to achieve a linear shortening of the pulse width of the second secondary control signal.

11. A control method for a resonant converter, characterized in that: The resonant converter comprises: an inverter switch unit having a plurality of power switch tubes, a resonant tank, a transformer, and a rectifier circuit having a first rectifier tube and a second rectifier tube, wherein two output ends of the rectifier circuit are used to connect a load; the control method comprises: collecting an electrical signal from the rectifier circuit and outputting a feedback signal, wherein the feedback signal reflects a load condition of the load; receiving the feedback signal, and causing the resonant converter to enter a frequency and width modulation continuous control mode according to the feedback signal; Among them, in the frequency and width modulation continuous control mode, the controller is used to control the first rectifier tube to be in the off state, and adjust the frequency and pulse width of multiple primary control signals and the second secondary control signal according to the feedback signal to respectively control the opening or closing of the multiple power switch tubes and the second rectifier tube.

12. The control method of the resonant converter according to claim 11, characterized in that: In the frequency and width modulation continuous control mode, as the load decreases, the frequencies of the multiple primary control signals and the second secondary control signal are reduced according to the feedback signal, and the pulse widths of the multiple primary control signals and the second secondary control signal are shortened.

13. The control method of the resonant converter according to claim 12, characterized in that: The frequencies of the plurality of primary control signals and the frequency of the second secondary control signal are linearly reduced, and the pulse widths of the plurality of primary control signals and the pulse width of the second secondary control signal are linearly shortened.

14. The control method of the resonant converter according to claim 11, characterized in that: When the resonant converter is in a normal working state, the resonant converter enters a frequency modulation control mode; wherein, in the frequency modulation control mode, the frequencies of the multiple primary control signals, the first secondary control signal, and the second secondary control signal are adjusted according to the feedback signal to respectively control the opening or closing of the multiple power switch tubes, the first rectifier tube, and the second rectifier tube.

15. The control method of the resonant converter according to claim 11, characterized in that: Generate a regulation signal according to the feedback signal, and when the regulation signal reaches a preset value, enable the resonant converter to enter a frequency and width modulation continuous control mode; Among them, in the frequency and width modulation continuous control mode, as the load decreases, the frequencies of the multiple primary control signals and the frequency of the second secondary control signal are linearly reduced according to the adjustment signal, and the pulse widths of the multiple primary control signals and the pulse widths of the second secondary control signal are linearly shortened.

16. The control method of the resonant converter according to claim 15, characterized in that: In the frequency and width modulation continuous control mode, as the load decreases, the period of the carrier signal is linearly increased according to the adjustment signal to achieve a linear decrease in the frequencies of the multiple primary control signals and the second secondary control signal; or, In the frequency and width modulation continuous control mode, as the load decreases, the multiple primary control signals and the second secondary control signal are output according to the primary control signal with a preset number of switching cycles interval according to the adjustment signal to achieve a linear reduction in the frequency of the multiple primary control signals and the frequency of the second secondary control signal.

17. The control method of the resonant converter according to claim 15, characterized in that: The plurality of power switch tubes include a first power switch tube and a second power switch tube; the first power switch tube and the second power switch tube are connected in series to form a bridge arm, and the bridge arm is connected to the input end of the inverter switch unit; The multiple primary control signals include a first primary control signal and a second primary control signal; the first primary control signal is used to control the on or off of the first power switch tube, and the second primary control signal is used to control the on or off of the second power switch tube; Wherein, in the frequency and width modulation continuous control mode, in each switching cycle, there is a dead time between the first primary control signal and the second primary control signal, and the dead time is fixed.

18. The control method of the resonant converter according to claim 17, characterized in that: In the frequency and width modulation continuous control mode, as the load decreases, the rising edge of the first primary control signal is delayed according to the adjustment signal to achieve a linear shortening of the pulse width of the first primary control signal, the falling edge of the second primary control signal is advanced to achieve a linear shortening of the pulse width of the second primary control signal, and the falling edge of the second secondary control signal is advanced to achieve a linear shortening of the pulse width of the second secondary control signal.

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