Control method and control device of resonant converter, medium, processor and switching power supply

Abstract

The invention discloses a control method and a control device of a resonant converter, a medium, a processor and a switching power supply, the resonant converter comprises a primary side bridge circuit, a resonant cavity, a transformer and a secondary side rectifying circuit, the resonant cavity comprises a resonant capacitor and a resonant inductor, the control method comprises the following steps: the resonant converter has a plurality of resonance stages in a working period, and when the working state of the resonant converter is switched between a first state and a second state, the time of one of the plurality of resonance stages is prolonged, therefore, the working state switching of the resonant converter is realized. The state switching performance of the resonant converter can be improved.

Description

Technical Field

[0001] The present invention relates to a resonant converter, and in particular to a control method, a control device, a medium, a processor and a switching power supply of a resonant converter. Background Art

[0002] In the early days, there were few studies on the dynamics of switching power supplies. At the same time, the loop control of classic structures such as buck circuits and boost circuits all used pulse width modulation (PWM), and the control loop was relatively simple. At the same time, due to the low operating frequency of the switching power supply, generally only one or two hundred kHz, its corresponding dynamic effect was not very important. However, under the current development trend of high frequency, high efficiency, and high power density of switching power supplies, dynamic load switching and dynamic effects have become the focus of attention. LLC resonant converter, as a typical isolated soft-switching high-efficiency DC-DC converter that achieves electrical isolation through a transformer, is quite popular in industrial electronic applications. At present, LLC resonant converter is the main topology converter that meets the development trend of switching power supplies, and its dynamic load switching and dynamic optimization need further analysis and research.

[0003] However, the control method adopted by the LLC resonant converter during the dynamic load switching process is pulse frequency modulation (PFM). In the early days, a simple voltage control loop was mostly used to realize the control of the entire LLC resonant converter. With the improvement of the loop control indicators of the LLC resonant converter, especially the strict requirements on dynamic aspects, more and more research has been conducted on the dynamic load switching and dynamic performance of the LLC resonant converter, and more and more corresponding dynamic optimization technologies have been conducted.

[0004] In 2013, the Korea Academy of Sciences proposed the average current method based on the current control method. It mainly collects the resonant current in the resonant cavity to form a current loop, and forms a dual-loop control with the external voltage loop. This method improves the LLC dynamic effect to a certain extent, but its experiments are limited to the situation below 150kHz. Its dynamic effect is not much improved compared with the average current method. The adjustment time of full load to half load and half load to full load is about 180μs. At the same time, its optimization scheme is still an analog scheme, which has many disadvantages. The following year, Canadian researchers proposed the charge control method, which uses the charge of the resonant capacitor in the resonant cavity to estimate the current, and forms a dual-loop control with the peripheral voltage loop. This method increases the control frequency (experimentally up to 300kHz) and is simpler in structure than the average current method, but this method is still an analog scheme, and many additional devices need to be added.

[0005] The above methods only focus on the effect of LLC output directly, without considering the diversity of LLC intermediate operating states, resulting in poor final dynamic switching effect.

[0006] It should be noted that the above information disclosed in the background technology section is only intended to deepen the understanding of the overall background technology of this application, and should not be regarded as admitting or suggesting in any form that the information constitutes prior art already known to those skilled in the art. Summary of the invention

[0007] In view of this, the technical problem to be solved by the present invention is to provide a control method, a control device, a medium, a processor and a switching power supply of a resonant converter, which can at least solve the deficiencies of the above-mentioned technical problems to a certain extent.

[0008] As a first aspect of the present invention, the technical solution of an embodiment of a control method for a resonant converter is provided as follows:

[0009] A control method for a resonant converter, the resonant converter comprising a primary bridge circuit, a resonant cavity, a transformer and a secondary rectifier circuit, the resonant cavity comprising a resonant capacitor and a resonant inductor, wherein the control method comprises: the resonant converter has a plurality of resonant stages within a working cycle, when the working state of the resonant converter is switched between a first state and a second state, extending the time of one of the plurality of resonant stages, thereby realizing the working state switching of the resonant converter.

[0010] Furthermore, before the working state of the resonant converter is switched, an electrical parameter of the resonant converter is detected, and the extension time of one of the several resonant stages is determined according to the electrical parameter.

[0011] Preferably, the electrical parameters are the voltage across the resonant capacitor, the current in the resonant inductor, the input voltage source voltage of the resonant converter, the load terminal voltage of the resonant converter, or the load terminal current of the resonant converter; according to the electrical parameters, combined with the first operating frequency, the first internal phase shift angle, the second operating frequency and the second internal phase shift angle of the resonant converter, the extension time of one of the several resonant stages of the resonant converter is calculated; wherein, the first operating frequency is the operating frequency before the state of the resonant converter is switched, the first internal phase shift angle is the internal phase shift angle before the state of the resonant converter is switched, the second operating frequency is the operating frequency after the state of the resonant converter is switched, and the second internal phase shift angle is the internal phase shift angle after the state of the resonant converter is switched.

[0012] Further, the first state is a light-load working state, and the second state is a heavy-load working state. When the resonant converter switches from the light-load working state to the heavy-load working state, the time of one of the several resonant stages is extended to a first time. When the resonant converter switches from the heavy-load working state to the light-load working state, the time of one of the several resonant stages is extended to a second time. The first time and the second time are not equal.

[0013] Further, the plurality of resonance stages include at least one of the following nine stages:

[0014] When the input voltage of the resonant cavity is positive and the primary voltage of the transformer is positive, the resonant capacitor and the resonant inductor in the resonant cavity resonate;

[0015] When the input voltage of the resonant cavity is positive and the primary voltage of the transformer is negative, the resonant capacitor and the resonant inductor in the resonant cavity resonate;

[0016] When the input voltage of the resonant cavity is negative and the primary voltage of the transformer is positive, the resonant capacitor and the resonant inductor in the resonant cavity resonate;

[0017] When the input voltage of the resonant cavity is negative and the primary voltage of the transformer is negative, the resonant capacitor and the resonant inductor in the resonant cavity resonate;

[0018] When the input voltage of the resonant cavity is zero and the primary voltage of the transformer is positive, the resonant capacitor and the resonant inductor in the resonant cavity resonate;

[0019] When the input voltage of the resonant cavity is zero and the primary voltage of the transformer is negative, the resonant capacitor and the resonant inductor in the resonant cavity resonate;

[0020] The input voltage of the resonant cavity is positive, and the resonant capacitor, the resonant inductor and the excitation inductor resonate together;

[0021] The input voltage of the resonant cavity is negative, and the resonant capacitor, the resonant inductor and the excitation inductor resonate together at an order;

[0022] The input voltage of the resonant cavity is zero, and the resonant capacitor, the resonant inductor and the excitation inductor resonate together.

[0023] As a second aspect of the present invention, the technical solution of an embodiment of a control device for a resonant converter is provided as follows:

[0024] A control device for a resonant converter, the resonant converter comprising a primary bridge circuit, a resonant cavity, a transformer and a secondary rectifier circuit, the resonant cavity comprising a resonant capacitor and a resonant inductor, wherein the control device for the resonant converter comprises the following modules:

[0025] A judging module, used for judging whether the working state of the resonant converter is switched between the first state and the second state;

[0026] The processing module is used to control the resonant converter to have a plurality of resonant states within a working cycle, and when the working state of the resonant converter is switched between a first state and a second state, prolong the time of one of the plurality of resonant stages, thereby realizing the working state switching of the resonant converter.

[0027] As a third aspect of the present invention, an embodiment of a computer-readable storage medium is provided as follows:

[0028] A computer-readable storage medium, comprising a stored program, wherein the program executes the control method described in any one of the first aspects above.

[0029] As a fourth aspect of the present invention, an embodiment of a processor is provided as follows:

[0030] A processor is used to run a program, wherein the program executes any one of the control methods described in the first aspect when running.

[0031] As a fifth aspect of the present invention, an embodiment of a switching power supply is provided as follows:

[0032] A switching power supply comprises a resonant converter, wherein the resonant converter is controlled by the control device of the resonant converter according to the second aspect.

[0033] When the working state of the resonant converter is switched between the first state and the second state, the present invention prolongs the time of one of the resonance stages among the plurality of resonance stages, thereby realizing the switching of the working state of the resonant converter, which has the following beneficial and excellent effects compared with the prior art:

[0034] (1) The present invention controls the resonant converter to extend the time of one of the multiple resonant stages within one cycle, thereby realizing the switching of the working state of the resonant converter, thereby eliminating the influence of load switching on the bandwidth, and thus significantly reducing the transition time of the dynamic process of the resonant converter;

[0035] (2) When the present invention is implemented, the state switching of the resonant converter can be realized by calculating the time of one of the multiple resonant stages in one cycle through the model. Therefore, the control difficulty of the primary switch tube can be reduced during the state switching process, which can significantly simplify the state switching process.

[0036] (3) Since the switching process of the present invention only depends on the extension time of one of the resonance stages among the plurality of resonance stages, it is irrelevant to whether the control of the resonant converter is linear or whether the electrical parameters of the resonant converter are coupled, and thus the dynamic load switching regulation capability of the resonant converter can be improved;

[0037] (4) When the present invention is implemented, the model can be used for accurate calculation, which can reduce the adjustment error and the overshoot and undershoot of the resonant inductor current and the resonant capacitor voltage. Therefore, the oscillation of the resonant voltage and current on the primary side of the transformer can be reduced, and the smooth switching of dynamic loads can be achieved under fixed gain. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The schematic diagram of the resonant converter to which the control method of the present invention is applicable;

[0039] Figure 2 The trajectory of the resonant converter control method switching from light load to heavy load in the first embodiment of the present invention;

[0040] Figure 3 The trajectory of the resonant converter control method switching from heavy load to light load in the first embodiment of the present invention;

[0041] Figure 4 It is a schematic diagram of the control method of the first embodiment of the present invention when the frequency modulation phase shift gain control strategy is adopted;

[0042] Figure 5 The load switching waveform and the working waveform of the primary switch tube of the control method of the first embodiment of the present invention;

[0043] Figure 6 The waveform comparison between the load switching process under the conventional phase shift control and the control method of the first embodiment;

[0044] Figure 7 FIG. 4 is a schematic diagram of a control device for a resonant converter according to a second embodiment of the present invention. DETAILED DESCRIPTION

[0045] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0046] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0047] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequential order. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present application are described here. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, the process, method, system, product or equipment comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or equipment.

[0048] It should be understood that, in the specification, claims and drawings, when a step is described as being connected to another step, the step may be directly connected to the other step, or be connected to the other step through a third step; when an element / unit is described as being "connected" to another element / unit, the element / unit may be "directly connected" to the other element / unit, or be "connected" to the other element / unit through a third element / unit.

[0049] In addition, the drawings of the present disclosure are only schematic diagrams of the present disclosure and are not necessarily drawn to scale. The same symbols in the drawings represent the same or similar parts, and thus repeated descriptions thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented using software, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontrollers.

[0050] In order to ensure that the technical solution of the present invention is clearer, the technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0051] The control method and control device of the present invention are applicable to the resonant converter principle diagram as shown in Figure 1 As shown, the resonant converter includes a primary inverter switch circuit (i.e. Figure 1 II), resonant cavity (i.e. Figure 1 III), transformer (i.e. Figure 1IV in the secondary rectifier circuit (i.e. Figure 1 V) and filter output circuit (i.e. Figure 1 VI). Figure 1 Where Vin is the input power of the resonant converter (i.e. Figure 1 In Ⅰ), Ro is the output load of the resonant converter.

[0052] The primary inverter switch circuit includes a bridge inverter circuit composed of switch tubes Q1, Q2, Q3 and Q4; the resonant cavity includes an LLC resonant cavity composed of a resonant capacitor Cr, a resonant inductor Lr and an excitation inductor Lm; the transformer T includes a transformer composed of a primary winding Np, and secondary windings Ns1 and Ns2; the secondary rectifier circuit is a full-wave rectifier circuit composed of two diodes; and the filter output circuit includes an output filter capacitor Co.

[0053] It should be noted that Figure 1 This is only a typical example of a resonant converter to which the control method and control device of the resonant converter of the present invention are applicable. The resonant converter to which the control method of the resonant converter of the present invention is applicable is not limited to Figure 1 The circuit also includes some other topological structures, such as a half-bridge inverter circuit on the primary side and a passive half-wave rectifier circuit, a passive full-bridge rectifier circuit, an active half-wave rectifier circuit, an active full-wave rectifier circuit and an active full-bridge rectifier circuit on the secondary side.

[0054] Depending on the application scenario, the resonant converter will operate in different operating states (i.e. different loads correspond to different gains). Different operating states will cause large differences in the switching of the resonant converter between dynamic loads. The present invention solves the technical problem of poor dynamic performance of the resonant converter caused by this.

[0055] The above gain refers to the normalized gain of the resonant converter. When the resonant converter is a half-bridge resonant converter, the normalized gain of the resonant converter is When the resonant converter is a full-bridge resonant converter, the normalized gain of the resonant converter is Where n is the transformation ratio of the transformer, Vo is the nominal output voltage of the resonant converter, and Vin is the nominal input voltage of the resonant converter.

[0056] against Figure 1The conventional control method for realizing gain regulation of the resonant converter is as follows: it includes two control variables, the switching frequency f and the inner phase shift angle θ, wherein the inner phase shift angle is the phase shift angle for phase shift control of the switch tube Q1 and the switch tube Q4, or the phase shift angle for phase shift control of the switch tube Q2 and the switch tube Q3, and the specific control timing is as follows: the duty ratio of the driving pulse of the switch tube Q1 and the switch tube Q4 is 50% (ignoring the dead time); the duty ratio of the driving pulse of the switch tube Q2 and the switch tube Q3 is 50% (ignoring the dead time); the driving pulse of the switch tube Q1 is complementary to the driving pulse of the switch tube Q2, and the driving pulse of the switch tube Q3 is complementary to the driving pulse of the switch tube Q4.

[0057] It should be noted that the above control method for achieving gain adjustment is only an example and does not limit the protection scope of the present invention. Those skilled in the art can select the control variables as needed.

[0058] First embodiment

[0059] The present embodiment provides a control method for a resonant converter, wherein the applicable primary side of the resonant converter includes a resonant cavity, the resonant cavity includes a resonant capacitor, a resonant inductor and an excitation inductance of the primary winding of the resonant converter transformer, wherein the control method of the resonant converter of the present embodiment includes: a primary side bridge circuit, a resonant cavity, a transformer and a secondary side rectifier circuit, the resonant cavity includes a resonant capacitor and a resonant inductor, wherein the control method of the present embodiment includes: the resonant converter has several resonant stages within one working cycle, and when the working state of the resonant converter is switched between a first state and a second state, the time of one of the several resonant stages is extended, thereby realizing the working state switching of the resonant converter.

[0060] The resonant converter has several resonant stages in one working cycle. Due to the diversity and complexity of its working stages, the actual dynamic effect in high-frequency dynamic conditions is not outstanding. In some specific occasions, its adjustment speed cannot meet the requirements. Conventional voltage control can no longer meet the performance requirements during load switching. From a control perspective, its bandwidth needs to be improved. The mainstream method is to use the resonant current of the resonant cavity to form a current loop and voltage control to improve its bandwidth. However, when switching is performed when the load difference is large, its performance cannot meet the requirements. The inventor of the present application has found through research that the control method of extending the time of one of the resonant stages in several resonant stages can be used to control load switching, which can eliminate the influence of load switching on bandwidth. Therefore, the control problem of load switching is solved directly from the operating state of the converter, so that load switching is not affected by the bandwidth limitation of the resonant converter.

[0061] Furthermore, before the working state of the resonant converter is switched, an electrical parameter of the resonant converter is detected, and the extension time of one of the plurality of resonant stages is determined according to the electrical parameter.

[0062] Further, the electrical parameters are the voltage across the resonant capacitor, the current in the resonant inductor, the input voltage source voltage of the resonant converter, the load terminal voltage of the resonant converter, or the load terminal current of the resonant converter; according to the electrical parameters, the extension time of one of the resonant stages of the resonant converter is calculated in combination with the first operating frequency, the first internal phase shift angle, the second operating frequency, and the second internal phase shift angle of the resonant converter; wherein the first operating frequency is the operating frequency f before the resonant converter state is switched. s1 , the first internal phase shift angle is the internal phase shift angle θ before the resonant converter state is switched 1 The second operating frequency is the operating frequency f after the resonant converter state is switched. s2 The second inner phase shift angle is the inner phase shift angle θ after the resonant converter state is switched. 2 The reason why the operating frequency and the internal phase-shift angle of the resonant converter are involved in calculating the time of one of the several resonant stages is that when the control variables of the control method for implementing gain regulation of the resonant converter include the operating frequency and the internal phase-shift angle of the resonant converter, the operating frequency and the internal phase-shift angle of the resonant converter will affect the calculation of the operating trajectory of the resonant converter, thereby affecting the calculation of the extended time of one of the several resonant stages.

[0063] Further, the first state is a light-load working state, and the second state is a heavy-load working state. When the resonant converter switches from the light-load working state to the heavy-load working state, the time of one of the several resonant stages is extended to the first time. When the resonant converter switches from the heavy-load working state to the light-load working state, the time of one of the several resonant stages is extended to the second time. The first time and the second time are not equal. The reason why the first time and the second time are not equal is that the trajectories of the light-load state and the heavy-load state are different.

[0064] Preferably, the plurality of resonance stages include at least one of the following nine stages, and the nine stages are respectively: ① when the input voltage of the resonance cavity is positive and the primary voltage of the transformer is positive, the stage in which the resonance capacitor and the resonance inductor in the resonance cavity resonate; ② when the input voltage of the resonance cavity is positive and the primary voltage of the transformer is negative, the stage in which the resonance capacitor and the resonance inductor in the resonance cavity resonate; ③ when the input voltage of the resonance cavity is negative and the primary voltage of the transformer is positive, the stage in which the resonance capacitor and the resonance inductor in the resonance cavity resonate; ④ when the input voltage of the resonance cavity is negative and the primary voltage of the transformer is negative, the resonance capacitor and the resonance inductor in the resonance cavity resonate. ⑤ When the input voltage of the resonant cavity is zero and the primary voltage of the transformer is positive, the resonant capacitor and the resonant inductor in the resonant cavity resonate; ⑥ When the input voltage of the resonant cavity is zero and the primary voltage of the transformer is negative, the resonant capacitor and the resonant inductor in the resonant cavity resonate; ⑦ When the input voltage of the resonant cavity is positive, the resonant capacitor, the resonant inductor and the excitation inductor resonate together; ⑧ When the input voltage of the resonant cavity is negative, the resonant capacitor, the resonant inductor and the excitation inductor resonate together; ⑨ When the input voltage of the resonant cavity is zero, the resonant capacitor, the resonant inductor and the excitation inductor resonate together.

[0065] Since the resonant converter has several resonant stages in one working cycle, in order to reduce the regulation error, reduce the overshoot and undershoot of the resonant inductor current and the resonant capacitor voltage, and achieve smooth switching of dynamic loads under fixed gain, it is necessary to calculate and extend the time of one of the several resonant stages. In the specific implementation, in order to make the switching process faster and the oscillation smaller, the traditional PID control (proportional-integral-derivative control) is abandoned and the OTC control (Optimal Trajectory Control) is preferred.

[0066] The key point of the control method of the resonant converter in this embodiment is to find the switching operation path according to the mathematical model. Figure 2 The trajectory of the resonant converter control method switching from light load to heavy load in the first embodiment of the present invention; Figure 3 1 is the trajectory of the resonant converter control method switching from heavy load to light load in the first embodiment of the present invention; wherein the abscissa is the per-unit value of the current in the resonant inductor, and the ordinate is the per-unit value of the voltage across the resonant capacitor. The per-unit value refers to a numerical notation method commonly used in engineering calculations, which indicates the relative values ​​of various physical quantities and parameters. When performing engineering calculations in power system calculations, the actual values ​​of various physical quantities are often not used, but the ratio of the actual value to a selected reference value with the same unit (i.e., the per-unit value) is used for calculation; Figure 2 Take this as an example to briefly explain how to find out the specific process of the switched running path:

[0067] (1) Based on the mathematical model (the calculation and proof process of the mathematical model under one of the conditions will be described in detail below), the voltage across the resonant capacitor and the current in the resonant inductor at points A, D, B, and E in the resonant stage are calculated.

[0068] (2) determining the resonance stage AD and the resonance stage BE according to the values ​​calculated in (1);

[0069] (3) Based on the resonant stage AD and the resonant stage BE calculated in (2), the voltage across the resonant capacitor and the current in the resonant inductor at the intersection C of the two resonant stages are further calculated.

[0070] (4) Based on the voltage across the resonant capacitor and the current in the resonant inductor at point C obtained in (3), the time of the AD resonance stage is extended to point C. Figure 2 The specific process of finding out the switching operation path can be summarized as follows: the resonance stage where AD is located belongs to one of the resonance stages among several resonance stages, and the resonance stage time of AD is extended to point C, where the CD segment is the extended resonance time.

[0071] It should be noted that the specific process of finding the switching operation path is universal and does not limit the resonant converter to adopt Figure 1 The topology and the frequency modulation phase shift control strategy adjust the gain, and do not limit which of the above nine situations one of the resonance stages is extended.

[0072] Figure 4 This is a schematic diagram of a frequency modulation and phase shift control strategy adopted in the control method of the first embodiment of the present invention. Figure 5 : is the load switching waveform and the working waveform of the primary switch tube of the control method of the first embodiment of the present invention, wherein Vcr is the voltage across the resonant capacitor; V gs1 is the driving pulse of switch tube Q1, V gs2 is the driving pulse of switch tube Q2, V gs3 is the driving pulse of switch tube Q3, V gs4 is the driving pulse of switch tube Q4; V AB It represents the voltage between the midpoints of the two bridge arms of the primary side and is a three-level square wave. Lr Represents the current flowing through the resonant inductor L r The current, i Lm Indicates the current flowing through the magnetizing inductance L m The current, i Load Indicates the load current. See Figure 4 and Figure 5 , before load switching, assuming the operating frequency of the resonant converter is f s1 , the internal phase shift angle is θ 1When the load current iload changes during the normal operation of the resonant converter, the load switches from light load to heavy load, and the switch tube Q4 needs to be turned off with a delay, that is, during the load switching process, the duty cycle of the drive pulse of the switch tube Q4 is greater than 50%. The time of extending one of the resonant stages in several resonant stages can be calculated according to the working state of the resonant converter and used to control the switching process (which can be calculated according to the mathematical model introduced below); after the load switching, the resonant converter is in another steady state. At this time, assuming that the operating frequency of the resonant converter is f s2 , the internal phase shift angle is θ 2 , according to the operating frequency f s1 、Internal phase shift angle θ 1 , operating frequency f s2 、Internal phase shift angle θ 2 The time for extending one of the resonance stages among the plurality of resonance stages can be calculated based on the loads before and after the switching (which can be calculated according to the mathematical model introduced below).

[0073] The control method of this embodiment is specifically implemented in the process of dynamic load switching by finding the switching operation path through the above-mentioned graphical method (establishing a trajectory diagram), and controlling the resonant converter to operate along the switching path, which can achieve a smooth transition of dynamic load switching under a fixed gain, reduce the voltage and current impact of the switching process, and reduce the output ripple loss, thereby improving the efficiency of the whole machine. Compared with the traditional primary side internal phase shift control method, since the time of one of the resonance stages in several resonance stages is extended, there is no error adjustment, and there is no overshoot or undershoot problem. The control method of this embodiment can significantly reduce the primary side voltage and current oscillation; compared with the traditional frequency modulation control method, since the dynamic load switching is completed within one cycle, the control method of this embodiment can effectively reduce the transition process of dynamic load switching.

[0074] The following will introduce the calculation and proof process of the above mathematical model under one of the conditions, one of which refers to the resonant converter using Figure 1 The control variables of the circuit for realizing the gain adjustment control method include the operating frequency and the internal phase shift angle of the resonant converter, and one of the resonant stages among the several resonant stages is extended to the above-mentioned case 9:

[0075] To simplify the analysis, the following assumptions are made:

[0076] (1) All switches are ideal switches, the switching process can be ignored, and there is no switching loss;

[0077] (2) The dead time of the switch can be ignored;

[0078] (3) The transformer is an ideal transformer;

[0079] (4) Ignore the stray resistance of the converter.

[0080] Using segmented analysis Figure 1 The resonant converter is mathematically modeled and set:

[0081] θ 0 =ω r ·t 0 ,θ 1 =ω r ·t 1 ,θ 2 =ω r ·t 2 ,θ 3 =ω r ·t 3 ,ω r =2·π·fr;

[0082]

[0083]

[0084] V B =V in ,

[0085]

[0086] Among them, ω r is the resonant angular frequency of the resonant converter, t0 is Figure 4 The first working moment, t1, marked on the horizontal axis is Figure 4 The second working time, t2, marked on the horizontal axis is Figure 4 The third working time 2, t3 marked on the horizontal axis is Figure 4 The fourth working moment marked on the horizontal axis, θ 0 ,θ 1 ,θ 2 , and θ 3 are the per-unit values ​​of the operating frequency of the resonant converter at the corresponding moment; fr is the resonant frequency of the resonant cavity, fs is the operating frequency of the resonant converter; n is the transformer ratio, Vo is the nominal output voltage of the resonant converter, Vin is the nominal input voltage of the resonant converter, M is the normalized gain of the resonant converter; RL is the impedance of the load, Io is the output current; Lm is the inductance of the excitation inductor, Lr is the inductance of the resonant inductor, λ is the inductance ratio; Zr is the characteristic impedance of the converter, Rac is the equivalent resistance of the transformer secondary side after conversion; Cr is the capacitance of the resonant capacitor; V B is the voltage reference; I B is the current reference; P Bis the transmission power reference; iLr is the current value in the resonant inductor; vCr is the voltage value across the resonant capacitor; iLrn is the per-unit value of the current in the resonant inductor; vCrn is the per-unit value of the voltage across the resonant capacitor.

[0087] According to the above settings, the calculus equation of the resonant converter is constructed and simplified to obtain Figure 1 Resonant converter Figure 4 The mathematical model of state switching control when the gain is adjusted using the frequency modulation phase shift control strategy is:

[0088]

[0089]

[0090]

[0091]

[0092] The parameters in the above mathematical model include θ1, θ2, θ3, iLr0n, Vcr0n, M, Q, and λ. Among them, the inductance ratio λ is related to the parameters of the resonant converter and is a known quantity, and Q can be set according to the load conditions. The mathematical model is a set of equations of dependent variables θ1, θ2, θ3, iLr0n, and Vcr0n with respect to the independent variable M. With the help of mathematical analysis tools, the relevant variables can be solved.

[0093] It should be noted that although the above mathematical model is established based on one of the above conditions, the mathematical model does not limit the protection scope of the control method of this embodiment. When the specific circuit of the resonant converter or the control strategy for adjusting the gain is different, and when one of the resonant stages among several resonant stages is extended to a situation other than the above-mentioned case 9, the mathematical model established by the state switching control will be different. The calculation and proof process are similar. Those skilled in the art can analyze it by themselves, and examples will not be given one by one here.

[0094] Figure 6 The waveform comparison between the load switching process under the traditional phase shift control and the control method of the first embodiment is shown in FIG. Figure 6 Where Vgs1 is the drive waveform of the switch tube Q1, and the other switch tube drive waveforms can be obtained according to the complementary principle and the phase shift principle. Vo1 is the output voltage waveform of the resonant converter, Io is the load current waveform of the resonant converter, ICC is the current waveform of the secondary side after half-wave rectification, iLr is the resonant inductor current waveform, and iLm is the excitation inductor current waveform. Figure 6It can be seen that, compared with the traditional PID closed-loop switching, the control method of this embodiment can significantly reduce the output voltage overshoot and undershoot, and at the same time greatly suppress the oscillation of the resonant voltage and current, and is not affected by the system bandwidth limitation, so as to achieve a fast transition of the resonant converter to the steady state after switching under fixed gain.

[0095] Second embodiment

[0096] This embodiment provides a control device for a resonant converter, wherein the resonant converter includes a primary full-bridge circuit, a resonant cavity, a transformer, and a secondary rectifier circuit, wherein the resonant cavity includes a resonant capacitor and a resonant inductor, wherein the control device for the resonant converter is shown in FIG. Figure 7 As shown, it includes the following modules:

[0097] A judging module, used for judging whether the working state of the resonant converter is switched between the first state and the second state;

[0098] The processing module is used to control the resonant converter to have several resonant states within one working cycle, and when the working state of the resonant converter is switched between a first state and a second state, the time of one of the several resonant stages is extended, thereby realizing the working state switching of the resonant converter.

[0099] Third embodiment

[0100] If the unit integrated in the control device in the above-mentioned second embodiment is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, in essence, or the part that contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product, and the computer software product is stored in a storage medium, including a number of instructions for a computer device (which can be a personal computer, a server or a network device, etc.) to perform all or part of the steps of the above-mentioned methods of each embodiment of the present invention. The aforementioned storage medium includes: U disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), mobile hard disk, magnetic disk or optical disk and other media that can store program codes.

[0101] Therefore, the third embodiment of the present invention provides a computer-readable storage medium, which includes a stored program, and the program executes the control method of any specific implementation method of the first embodiment.

[0102] Fourth embodiment

[0103] A fourth embodiment of the present invention provides a processor for running a program, wherein the program executes the control method of any specific implementation method of the first embodiment when running.

[0104] Fifth embodiment

[0105] A fifth embodiment of the present invention provides a switching power supply, including a resonant converter, wherein the resonant converter is controlled by the control device of the resonant converter in the second embodiment.

[0106] The embodiments described above are merely examples of the technical solutions and contents of the present invention. It should be noted that the above embodiments should not be regarded as limiting the present invention. For those skilled in the art, several improvements and modifications can be made without departing from the spirit and scope of the present invention, but they will not deviate from the spirit of the present invention or exceed the scope defined by the attached claims, and should also be regarded as the protection scope of the present invention.

Claims

1. A control method for a resonant converter, wherein the resonant converter comprises a primary bridge circuit, a resonant cavity, a transformer and a secondary rectifier circuit, wherein the resonant cavity comprises a resonant capacitor and a resonant inductor, characterized in that: The control method includes: the resonant converter has several resonant stages within one working cycle, and when the working state of the resonant converter is switched between a first state and a second state, the time of one of the several resonant stages is extended, thereby realizing the working state switching of the resonant converter.

2. The control method of the resonant converter according to claim 1, characterized in that: Before the working state of the resonant converter is switched, an electrical parameter of the resonant converter is detected, and an extension time of one of the plurality of resonant stages is determined according to the electrical parameter.

3. The control method of the resonant converter according to claim 2, characterized in that: The electrical parameters are the voltage across the resonant capacitor, the current in the resonant inductor, the input voltage source voltage of the resonant converter, the load terminal voltage of the resonant converter, or the load terminal current of the resonant converter; based on the electrical parameters, combined with the first operating frequency, the first internal phase shift angle, the second operating frequency and the second internal phase shift angle of the resonant converter, the extension time of one of the several resonant stages of the resonant converter is calculated; wherein, the first operating frequency is the operating frequency before the state of the resonant converter is switched, the first internal phase shift angle is the internal phase shift angle before the state of the resonant converter is switched, the second operating frequency is the operating frequency after the state of the resonant converter is switched, and the second internal phase shift angle is the internal phase shift angle after the state of the resonant converter is switched.

4. The control method of the resonant converter according to claim 1, characterized in that: The first state is a light-load working state, and the second state is a heavy-load working state. When the resonant converter switches from the light-load working state to the heavy-load working state, the time of one of the several resonant stages is extended to a first time. When the resonant converter switches from the heavy-load working state to the light-load working state, the time of one of the several resonant stages is extended to a second time. The first time and the second time are not equal.

5. The control method of the resonant converter according to claim 1, characterized in that: The plurality of resonance stages include at least one of the following nine stages: When the input voltage of the resonant cavity is positive and the primary voltage of the transformer is positive, the resonant capacitor and the resonant inductor in the resonant cavity resonate; When the input voltage of the resonant cavity is positive and the primary voltage of the transformer is negative, the resonant capacitor and the resonant inductor in the resonant cavity resonate; When the input voltage of the resonant cavity is negative and the primary voltage of the transformer is positive, the resonant capacitor and the resonant inductor in the resonant cavity resonate; When the input voltage of the resonant cavity is negative and the primary voltage of the transformer is negative, the resonant capacitor and the resonant inductor in the resonant cavity resonate; When the input voltage of the resonant cavity is zero and the primary voltage of the transformer is positive, the resonant capacitor and the resonant inductor in the resonant cavity resonate; When the input voltage of the resonant cavity is zero and the primary voltage of the transformer is negative, the resonant capacitor and the resonant inductor in the resonant cavity resonate; The input voltage of the resonant cavity is positive, and the resonant capacitor, the resonant inductor and the excitation inductor resonate together; The input voltage of the resonant cavity is negative, and the resonant capacitor, the resonant inductor and the excitation inductor resonate together at an order; The input voltage of the resonant cavity is zero, and the resonant capacitor, the resonant inductor and the excitation inductor resonate together.

6. A control device for a resonant converter, the resonant converter comprising a primary bridge circuit, a resonant cavity, a transformer and a secondary rectifier circuit, the resonant cavity comprising a resonant capacitor and a resonant inductor, characterized in that: The control device of the resonant converter comprises the following modules: A judging module, used for judging whether the working state of the resonant converter is switched between the first state and the second state; The processing module is used to control the resonant converter to have a plurality of resonant states within a working cycle, and when the working state of the resonant converter is switched between a first state and a second state, prolong the time of one of the plurality of resonant stages, thereby realizing the working state switching of the resonant converter.

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium includes a stored program, wherein the program executes the control method according to any one of claims 1 to 5.

8. A processor, characterized in that: The processor is used to run a program, wherein the program executes the control method described in any one of claims 1 to 5 when running.

9. A switching power supply, characterized in that: It comprises a resonant converter, and the resonant converter is controlled by the control device of the resonant converter according to claim 6.

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