A resonant cavity detection and dynamic adjustment circuit

Abstract

The application discloses a resonant cavity detection and dynamic adjustment circuit, comprising: a power supply; a control circuit electrically connected with the power supply; a resonant circuit comprising a switching module, the switching module comprising a first switching element and a second switching element, the first switching element being electrically connected with the power supply, the control circuit and the second switching element respectively, and the second switching element being electrically connected with the control circuit; a resonant cavity comprising a first resonant element and a second resonant element, the first resonant element being electrically connected with the second switching element and the second resonant element respectively; a transformer electrically connected with the first switching element, the second switching element and the second resonant element respectively; an output circuit comprising a sampling element electrically connected with the transformer; a sampling circuit electrically connected with the control circuit, the second switching element, the first resonant element, the second resonant element, the transformer and the sampling element respectively; the application can collect the voltage of the resonant cavity element and calculate the resonant frequency of the resonant cavity work, so as to adjust the switching frequency of the switching module to be the same as the resonant frequency.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of power transmission, in particular, to a resonant cavity detection and dynamic adjustment circuit. BACKGROUND

[0002] LLC circuit is mainly used to realize power conversion and stable output voltage, through controlling the resonant frequency to realize high efficiency, low noise power transmission, widely used in electronic equipment, communication equipment and other fields, through reasonable design of circuit parameters and control strategy, realize high efficiency conversion and stable output. LLC circuit is mainly composed of four main modules: power switch, resonant cavity, transformer and diode rectifier. The power switch element is usually a MOS tube, which can convert the input DC voltage into a high-frequency square wave; the resonant cavity is composed of inductor and capacitor, which eliminates the harmonics of square wave and outputs the fundamental frequency sine wave; the transformer transmits high-frequency energy and boosts or reduces the voltage according to the application requirement; finally, the diode rectifier converts the sine wave into stable DC output. The working principle of LLC circuit is based on the characteristics of resonant converter, which realizes the stability of output voltage by controlling the frequency of power switch. It can reduce the switching loss and joule heat of MOS tube through resonance, so that it does not need additional heat sink. Unlike traditional PWM (pulse width modulation) converter, LLC circuit realizes constant output voltage through frequency regulation, and enables the MOS tube switch in the primary side to realize zero voltage switching (ZVS) and the rectifier diode in the secondary side to realize zero current switching (ZCS), further improving efficiency and power density.

[0003] However, at the same time, there is a problem that the MOS tube uses zero voltage switching (ZVS) scheme to open, and the LLC circuit works with the connected electrical equipment. After the use of electrical equipment, the output power of the circuit will change, which causes the change of resonant cavity parameters. Therefore, the voltage of the capacitor and inductor of the resonant cavity needs to be sampled to calculate the real-time resonant frequency of the resonant cavity in work, so as to adjust the switching frequency of the MOS tube to be consistent with the resonant frequency.

[0004] The change of resonant cavity parameters is usually caused by the static error of the elements constituting the resonant cavity itself, and the dynamic error of the elements constituting the resonant cavity caused by the change of current and voltage in the process of using LLC circuit. In LLC circuit, there is usually parasitic inductance and distributed capacitance on the connection line of the element, and these parameter values will cause the inaccuracy of the sampling voltage of the capacitor and inductor. The calculated resonant frequency deviates from the actual resonant frequency of the resonant cavity in work, so that the LLC circuit cannot completely enter the resonant state in actual work, and there are more noise interferences in the output fundamental frequency sine wave, and the MOS tube cannot realize ZVS, resulting in increased circuit loss. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a resonant cavity detection and dynamic adjustment circuit,

[0006] The object of the present application is achieved by the following solution:

[0007] A resonant cavity detection and dynamic adjustment circuit comprises:

[0008] a power supply;

[0009] a control circuit electrically connected to the power supply;

[0010] a resonant circuit comprising:

[0011] a switching module comprising a first switching element and a second switching element, the first switching element being electrically connected to the power supply, the control circuit and the second switching element, and the second switching element being electrically connected to the control circuit;

[0012] a resonant cavity comprising a first resonant element and a second resonant element, the first resonant element being electrically connected to the second switching element and the second resonant element;

[0013] a transformer electrically connected to the first switching element and the second resonant element;

[0014] an output circuit comprising a sampling element electrically connected to the transformer; and

[0015] a sampling circuit electrically connected to the control circuit, the second switching element, the first resonant element, the second resonant element, the transformer and the sampling element;

[0016] After the control circuit is initialized, the initial resonant frequency f0 of the resonant cavity is calculated, and the control circuit controls the first switching element and the second switching element to alternately conduct according to the initial resonant frequency f0. When the first switching element is turned on and the second switching element is turned off, the sampling circuit collects the voltages U1 and U2 of the first resonant element and the second resonant element, and transmits the collected voltage values U1 and U2 to the control circuit. The control circuit calculates the resonant frequency f1 of the resonant cavity when it is working according to the voltage U1 of the first resonant element, the voltage U2 of the second resonant element and the transformation ratio of the transformer itself. When the second switching element is turned on and the first switching element is turned off, the sampling circuit collects the voltages U3 and U4 of the first resonant element and the second resonant element, and the control circuit calculates the resonant frequency f2 of the resonant cavity when it is working according to the voltage U3 of the first resonant element, the voltage U4 of the second resonant element and the transformation ratio of the transformer itself. The control circuit calculates the average value F of the resonant frequency of the resonant cavity when it is working according to f1 and f2, and then adjusts the switching frequency of the first switching element and the second switching element to F.

[0017] In one embodiment, the first switch element comprises a MOS tube Q1, the second switch element comprises a MOS tube Q2, the MOS tube Q1 and the MOS tube Q2 each have a drain D, a gate G and a source S, the first resonant element comprises a capacitor C7, the second resonant element comprises an inductor L1, the capacitor C7 and the inductor L1 have a No. 1 terminal and a No. 2 terminal; the drain D of the MOS tube Q1 is electrically connected with a power supply, the gate G of the MOS tube Q1 is electrically connected with a control circuit, the source S of the MOS tube Q1 is respectively electrically connected with a transformer and the drain D of the MOS tube Q2; the drain D of the MOS tube Q2 is electrically connected with the transformer, the gate G of the MOS tube Q2 is electrically connected with the control circuit, the source S of the MOS tube Q2 is respectively electrically connected with a sampling circuit and the No. 1 terminal of the capacitor C7; the No. 2 terminal of the capacitor C7 is electrically connected with the No. 1 terminal of the inductor L1, and the No. 2 terminal of the inductor L1 is electrically connected with the transformer.

[0018] The control circuit reads the initial capacitance value C1 of the capacitor C7 and the initial inductance value L1 of the inductor L1, and calculates the initial resonant frequency of the resonant cavity. The control circuit controls the MOS tube Q1 and the MOS tube Q2 to be alternately turned on according to the initial resonant frequency f0.

[0019] In one embodiment, a voltage sampling point C_B of the capacitor C7 is arranged on the source S of the MOS tube Q2, another voltage sampling point C_A of the capacitor C7 is arranged on the No. 2 terminal of the inductor L1, the sampling point C_B and the sampling point C_A are respectively electrically connected with a sampling circuit; a sampling point L_A of the inductor L1 is arranged on the No. 2 terminal of the capacitor C7, and another sampling point L_B of the inductor L1 is arranged on the transformer, the sampling point L_A and the sampling point L_B are respectively electrically connected with the sampling circuit; when the MOS tube Q1 is turned on, the sampling circuit (4) transmits the voltage U1 of the capacitor C7 and the voltage U2 of the inductor L1 to the control circuit, and the control circuit (2) calculates the dynamic capacitance of the capacitor C7 and the dynamic inductance of the inductor L1 , and then calculates .

[0020] When the MOS tube Q2 is turned on, the sampling circuit transmits the voltage U3 of the capacitor C7 and the voltage U4 of the inductor L1 to the control circuit, and the control circuit calculates the dynamic capacitance of the capacitor C7 and the dynamic inductance of the inductor L1 , and then calculates , wherein i1 is the inverse of the transformer ratio.

[0021] The control circuit calculates the average value F of the resonant frequency of the resonant cavity when working according to f1 and f2, and then adjusts the switching frequency of the MOS tube Q1 and the MOS tube Q2 to F.

[0022] In one embodiment, the sampling element includes a resistor R6, which has a terminal 1 and a terminal 2. Terminal 1 of the resistor R6 is electrically connected to a transformer, and terminal 2 of the resistor R6 outputs a voltage. Terminals 1 and 2 of the resistor R6 are respectively electrically connected to a sampling circuit.

[0023] In one embodiment, the output circuit further includes a reverse protection element, which includes a diode U1. The diode U1 has a terminal 1 and a terminal 2. Terminal 1 of the diode U1 is electrically connected to the transformer. Terminal 2 of the diode U1 outputs a voltage and is electrically connected to the sampling circuit.

[0024] In one embodiment, a sampling point V_A is provided on terminal 2 of diode U1, and sampling point V_A is electrically connected to the sampling circuit; a sampling point V_B is provided on terminal 1 of resistor R6, and a sampling point V- is provided on terminal 2 of resistor R6, and sampling points V_B and V- are respectively electrically connected to the sampling circuit.

[0025] When MOSFET Q1 is turned on, the sampling circuit also collects the voltage U of the output circuit through sampling point V_A. 01 The sampling circuit acquires the voltage value U of resistor R6. R6（1） The data is then transmitted to the control circuit, which calculates the current flowing through resistor R6 at this time. The control circuit then... Calculate the equivalent resistance R of the output circuit. ac1 Simultaneously calculate the gain ;

[0026] When MOSFET Q2 is turned on, the sampling circuit also collects the voltage U of the output circuit through sampling point V_A. 02 The sampling circuit acquires the voltage value U of resistor R6. R6（2） The data is then transmitted to the control circuit, which calculates the current flowing through resistor R6 at this time. The control circuit then... Calculate the equivalent resistance R of the output circuit. ac2 Simultaneously calculate the gain In the above formula, R is the resistance of resistor R6, n is the transformer turns ratio, and the control circuit calculates the average gain Q and the average equivalent resistance R based on Q1 and Q2. ac Adjust the average equivalent resistance R ac This makes the average gain Q=1.

[0027] In one of the embodiments, the control circuit comprises a control chip, an oscillation module, a reset module, a filter module, a current limiting module and a protection module, the control chip has a plurality of ports, the oscillation module is electrically connected with the 5th port and the 6th port of the control chip respectively, the reset module is electrically connected with the 7th port of the control chip, the reset module is also electrically connected with a power supply and grounded to SGND, the filter module is electrically connected with the 9th port and the 30th port of the control chip, and the filter module is grounded to SGND, the current limiting module is electrically connected with the 11th port and the 21st port of the control chip, the current limiting module is also electrically connected with the power supply and grounded to SGND, and the protection module is electrically connected with the 12th port and the 13th port of the control chip, the protection module is also electrically connected with the power supply and grounded to SGND.

[0028] In one of the embodiments, the sampling circuit comprises a capacitor voltage sampling circuit and an inductor voltage sampling circuit, the capacitor voltage sampling circuit is electrically connected with the detection points C_A and C_B respectively, and the inductor voltage sampling circuit is electrically connected with the detection points L_A and L_B respectively, wherein the capacitor voltage sampling circuit is used to collect the voltages U1 and U3 of the capacitor C7 in operation, and the inductor voltage sampling circuit is used to collect the voltages U2 and U4 of the inductor L1 in operation.

[0029] In one of the embodiments, the sampling circuit further comprises an output voltage sampling circuit and a resistor voltage sampling circuit, the output voltage sampling circuit is electrically connected with the 2nd port of the diode U1, and the resistor voltage sampling circuit is electrically connected with the 1st port and the 2nd port of the resistor R6 respectively, wherein the output voltage sampling circuit is used to collect the voltage of the output circuit, and the resistor voltage sampling circuit is used to collect the voltage of the resistor R6.

[0030] Compared with the prior art, the present application has at least the following advantages:

[0031] The present application can collect the voltages U1, U3 and U2, U4 of the first resonant element and the second resonant element when the first switch element and the second switch element are turned on respectively by the sampling circuit, and the control circuit calculates the resonant frequencies f1 and f2 of the resonant cavity when the first switch element and the second switch element are turned on respectively according to U1, U2 and U3, U4, and then adjusts the switching frequency of the first switch element and the second switch element to the average value F of the resonant frequencies of the resonant cavity in operation, so that the first switch element and the second switch element realize ZVS, the circuit loss is reduced, the circuit can enter the resonant state, and the noise interference in the output fundamental frequency sine wave is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0032] The drawings described herein are used to provide further understanding of the present application, and form a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application, and do not constitute improper limitations on the present application. In the drawings:

[0033] Figure 1 Circuit diagram of the control circuit in the present application;

[0034] Figure 2 Circuit diagram of the resonant circuit in the present application;

[0035] Figure 3 Circuit diagram of the control circuit in the present application;

[0036] Figure 4 Circuit diagram of the capacitor voltage sampling circuit;

[0037] Figure 5 Circuit diagram of the inductor voltage sampling circuit;

[0038] Figure 6 Circuit diagram of the output voltage sampling circuit;

[0039] Figure 7 Circuit diagram of the resistor voltage sampling circuit;

[0040] Figure 8 Flow chart of the method for raising the resonant cavity frequency;

[0041] Wherein, the reference signs are, 1. power supply; 2. control circuit; 21. control chip; 22. oscillation module; 23. reset module; 24. filter module; 25. current limiting module; 26. protection module; 3 resonant circuit; 31 switching module; 311. first switching element; 312. second switching element; 32. resonant cavity; 321. first resonant element; 322. second resonant element; 33. transformer; 34. output circuit; 341. sampling element; 4 sampling circuit; 41. capacitor voltage sampling circuit; 42. inductor voltage sampling circuit; 43. output voltage sampling circuit; 44. resistor voltage sampling circuit. DETAILED DESCRIPTION

[0042] The embodiments of the present application will be described herein below with reference to a number of drawings. Numerous specific details will be set forth in the following description in order to provide a thorough understanding of the present application. It will be apparent to those skilled in the art, however, that the present application can be practiced without such specific details. In other instances, well-known structures and functions have not been described in detail in order to avoid obscuring the present application. Also, some of the drawings can be simplified for purposes of simplicity and clarity.

[0043] It should be noted that all directional references (e.g., upper, lower, left, right, front, rear, etc.) are in relation to the exemplary orientation of the device as shown in the drawings and are used only to simplify the description of the application. In addition, terms such as "first" and "second" are only used to differentiate one element from another element, and do not necessarily have an ordinal meaning.

[0044] In addition, the description such as "first", "second" and the like in the present application is only for the purpose of description and does not mean to particularly indicate the order or sequence, nor to limit the present application, which is merely to distinguish the components or operations described by the same technical terms, and cannot be understood as indicating or implying the relative importance of the indicated technical features or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first", "second" can explicitly or implicitly include at least one of the features. In addition, the technical solutions of various embodiments can be combined with each other, but it must be based on the fact that a person skilled in the art can realize it, when the combination of technical solutions appears contradictory or unachievable, it should be considered that the combination of technical solutions does not exist, nor within the protection scope required by the present application.

[0045] In order to further understand the inventive content, characteristics and effects of the present application, the following examples are given, and the details are described as follows with reference to the accompanying drawings:

[0046] As shown in Figures 1 to 8 , Figure 1 the circuit principle of the present application, Figure 2 the resonant circuit circuit diagram in the present application, Figure 3 the control circuit circuit diagram in the present application, Figures 4 to 7 the circuit diagram of each sampling circuit, Figure 8 the circuit working flow chart of the present application. The present embodiment provides a resonant cavity detection and dynamic adjustment circuit, which comprises a power supply 1, a control circuit 2, a resonant circuit 3 and a sampling circuit 4, the power supply 1 is electrically connected with the control circuit 2 and the resonant circuit 3 respectively, the control circuit 2 is electrically connected with the resonant circuit 3 and the sampling circuit 4 respectively; the resonant circuit 3 and the sampling circuit 4 are electrically connected. The power supply can supply power to the control circuit 2 and the resonant circuit 3; the sampling circuit 4 collects the voltage of the internal elements of the resonant circuit 3 and transmits it to the control circuit 2 to calculate the resonant frequency.

[0047] Further, as shown in Figure 2 , the resonant circuit 3 comprises a switching module 31, a resonant cavity 32, a transformer 33 and an output circuit 34, the switching module 31 is electrically connected with the power supply 1, the resonant cavity 32 and the transformer 33 respectively; the resonant cavity 32 is electrically connected with the transformer 33; the transformer 33 is electrically connected with the output circuit 34.

[0048] Specifically, as shown in Figure 2 , the switching module 31 comprises a first switching element 311 and a second switching element 312, the first switching element 311 is electrically connected with the power supply 1, the control circuit 2 and the second switching element 312 respectively, the second switching element 312 is electrically connected with the control circuit 2.

[0049] Specifically, the resonant cavity 32 comprises a first resonant element 321 and a second resonant element 322, the first resonant element 321 is electrically connected with the second switch element 312 and the second resonant element 322 is electrically connected with the first switch element 311. The transformer 33 is electrically connected with the first switch element 311, the second switch element 312 and the second resonant element 322. The output circuit 34 comprises a sampling element 341, which is electrically connected with the transformer 33.

[0050] Specifically, the sampling circuit 4 is electrically connected with the control circuit 2, the second switch element 312, the first resonant element 321, the second resonant element 322, the transformer 33 and the sampling element 341.

[0051] After the control circuit 2 is initialized, the initial resonant frequency f0 of the resonant cavity 32 is calculated, and the control circuit 2 controls the first switch element 311 and the second switch element 312 to alternately conduct according to the initial resonant frequency f0. When the first switch element 311 is turned on and the second switch element 312 is turned off, the sampling circuit 4 collects the voltages U1 and U2 of the first resonant element 321 and the second resonant element 322, and transmits the collected voltage values U1 and U2 to the control circuit 2. The control circuit 2 calculates the resonant frequency f1 of the resonant cavity 32 at this time according to the voltage U1 of the first resonant element 321, the voltage U2 of the second resonant element 322 and the transformation ratio of the transformer 33 itself. When the second switch element 312 is turned on and the first switch element 311 is turned off, the sampling circuit 4 collects the voltages U3 and U4 of the first resonant element 321 and the second resonant element 322, and the control circuit 2 calculates the resonant frequency f2 of the resonant cavity 32 at this time according to the voltage U3 of the first resonant element 321, the voltage U4 of the second resonant element 322 and the transformation ratio of the transformer 33 itself. The control circuit 2 calculates the average value F of the resonant frequency of the resonant cavity 32 at work according to f1 and f2, and then adjusts the switching frequency of the first switch element 311 and the second switch element 312 to F.

[0052] The sampling circuit 4 collects the voltages U1, U3, U2, and U4 of the first resonant element 321 and the second resonant element 322 when the first switching element 311 and the second switching element 312 are respectively turned on. The control circuit 2 can calculate the resonant frequencies f1 and f2 of the resonant cavity 32 when the first switching element 311 and the second switching element 312 are respectively turned on based on U1, U2, U3, and U4. Thus, the control circuit 2 calculates the average value F of the resonant frequency of the resonant cavity 32 when it is working based on f1 and f2, and then adjusts the switching frequencies of the first switching element 311 and the second switching element 312 to F. When the switching frequencies of the first switching element 311 and the second switching element 312 are equal to the average value F of the resonant frequency of the resonant cavity 32 when it is working, the first switching element 311 and the second switching element 312 achieve ZVS, reduce circuit loss, and the circuit can enter the resonant state, reducing the noise interference in the sinusoidal wave of the output fundamental frequency.

[0053] In this embodiment, power supply 1 includes a DC power supply and an AC power supply. The DC power supply is electrically connected to the control circuit 2, and the AC power supply is electrically connected to the resonant circuit 3. The DC power supply is a 3.3V DC regulated power supply, and the AC power supply uses AC mains power.

[0054] Furthermore, such as Figure 2 As shown, the first switching element 311 includes a MOSFET Q1, and the second switching element 312 includes a MOSFET Q2. MOSFETs Q1 and Q2 each have a drain D, a gate G, and a source S. The first resonant element 321 includes a capacitor C7, and the second resonant element includes an inductor L1. Capacitor C7 and inductor L1 each have a terminal 1 and a terminal 2. The drain D of MOSFET Q1 is electrically connected to power supply 1, the gate G of MOSFET Q1 is electrically connected to control circuit 2, and the source S of MOSFET Q1 is electrically connected to transformer 33 and the drain D of MOSFET Q2, respectively. The drain D of MOSFET Q2 is electrically connected to transformer 33, the gate G of MOSFET Q2 is electrically connected to control circuit 2, and the source S of MOSFET Q2 is electrically connected to sampling circuit 4 and terminal 1 of capacitor C7, respectively. Terminal 2 of capacitor C7 is electrically connected to terminal 1 of inductor L1, and terminal 2 of inductor L1 is electrically connected to transformer 33.

[0055] Specifically, control circuit 2 reads the initial capacitance value C1 and inductance value L1 of capacitor C7 and inductance value L1, respectively, and calculates the initial resonant frequency of resonant cavity 32. , the control circuit 2 controls the MOS tube Q1 and the MOS tube Q2 to be alternately conducted according to the initial resonant frequency f0. When the MOS tube Q1 and the MOS tube Q2 are alternately conducted according to f0, the current is caused to flow through the capacitor C7 and the inductor L1, so that the resonant cavity 32 composed of the capacitor C7 and the inductor L1 resonates. Since the switching frequency of the MOS tube Q1 and the MOS tube Q2 alternately conducted is the same as the initial resonant frequency f0, the capacitive reactance of the capacitor C7 is equal to the inductive reactance of the inductor L1, so that the circuit at this time enters the resonant state, thereby eliminating the voltage and current overlap in the conducting process of the MOS tube Q1 and the MOS tube Q2, and realizing the ZVS of the MOS tube Q1 and the MOS tube Q2.

[0056] It should be noted that in this example, the transformer 33 is a step-down transformer, and the transformation ratio of the transformer 33 is 3 / 2. The transformer 33 has 1-4 ends, the source S of the MOS tube Q1 and the drain D of the MOS tube Q2 are respectively electrically connected with the 1 end of the transformer 33, and the 2 end of the inductor L1 is electrically connected with the 2 end of the transformer 33.

[0057] As shown in Figure 2 , the source S of the MOS tube Q2 is provided with a voltage sampling point C_B of the capacitor C7, and the 2 end of the inductor L1 is provided with another sampling point C_A of the capacitor C7, and the sampling point C_B and the sampling point C_A are respectively electrically connected with the sampling circuit 4; the 2 end of the capacitor C7 is provided with a sampling point L_A of the inductor L1, and the transformer 33 is provided with another sampling point L_B of the inductor L1, and the sampling point L_A and the sampling point L_B are respectively electrically connected with the sampling circuit 4. Among them, the voltage sampling point C_B is arranged on the source S of the MOS tube Q2, and the sampling point C_A is arranged on the 2 end of the inductor L1.

[0058] When the current passes through the capacitor C7 and the inductor L1, there is a temperature drift, and there is a parasitic inductance and a distributed capacitance on the connection line of the capacitor C7 and the inductor L1, which will divide the voltage across the capacitor C7 and the inductor L1, resulting in inaccurate voltage collected by the sampling circuit 4 across the capacitor C7 and the inductor L1. By arranging the sampling points C_A and C_B, the voltage on the connection line of the capacitor C7 can be collected at the same time, that is, the voltage on the whole connection line of the capacitor C7 is collected, so as to ensure the accuracy of the voltage collected by the sampling circuit 4 on the capacitor C7. Similarly, the voltage collection principle of the inductor L1 is the same as that of the capacitor C7, which is not described here.

[0059] In the embodiment, when MOS tube Q1 is turned on, MOS tube Q2 is turned off, and a loop is formed by MOS tube Q1, transformer 33, inductor L1 and capacitor C7. Sampling circuit 4 transmits the voltage U1 of capacitor C7 and the voltage U2 of inductor L1 to control circuit 2, and control circuit 2 calculates the dynamic capacitance of capacitor C7 in operation and the dynamic inductance of inductor L1 in operation and calculates the resonance frequency of resonant cavity 32 at this moment as f1.

[0060] When MOS tube Q2 is turned on, MOS tube Q1 is turned off, and a loop is formed by MOS tube Q2, transformer 33, inductor L1 and capacitor C7. Sampling circuit 4 transmits the voltage U3 of capacitor C7 and the voltage U4 of inductor L1 to control circuit 2, and control circuit 2 calculates the dynamic capacitance of capacitor C7 in operation and the dynamic inductance of inductor L1 in operation and calculates In the above formula, i1 is the inverse of the transformation ratio of transformer 33, and j is the imaginary unit. In this embodiment, the transformation ratio of transformer 33 is 3 / 2, and the inverse is 2 / 3.

[0061] Since MOS tube Q1 and MOS tube Q2 are turned on for one operation cycle respectively, sampling circuit 4 needs to detect the voltage U1 and U3 of capacitor C7 and the voltage U2 and U4 of inductor L1 when MOS tube Q1 and MOS tube Q2 are turned on respectively in one cycle in real time, and then transmits them to control circuit 2. Control circuit 2 calculates f1 according to U1 and U2, and calculates f2 according to U3 and U4. Control circuit 2 calculates the average value F of the resonance frequency of resonant cavity 32 in operation in this cycle according to f1 and f2. The average value F of the resonance frequency is closest to the resonance frequency of resonant cavity 32 when MOS tube Q1 and MOS tube Q2 are turned on respectively. Control circuit 2 thus converts the switching frequency of MOS tube Q1 and MOS tube Q2 into F. The closer the switching frequency of MOS tube Q1 and MOS tube Q2 is to the resonance frequency of resonant cavity 32, the better MOS tube Q1 and MOS tube Q2 can realize ZVS.

[0062] Specifically, as shown in Figure 2 , sampling element 341 includes resistor R6, resistor R6 has No. 1 end and No. 2 end, No. 1 end of resistor R6 is electrically connected with transformer 33, wherein No. 1 end of resistor R6 is electrically connected with No. 4 end of transformer 33, No. 2 end of resistor R6 outputs voltage, and No. 1 end and No. 2 end of resistor R6 are respectively electrically connected with sampling circuit 4. Since resistor R6 is connected in series in output circuit 34, and the current passing through resistor R6 can be calculated directly by using Ohm's law, the output current of output circuit 34 can be measured.

[0063] Specifically, as shown in Figure 2 , the output circuit 34 further comprises a reverse protection element 342, which comprises a diode U1 having a No. 1 end and a No. 2 end, the No. 1 end of the diode U1 being electrically connected with the transformer 33; the No. 2 end of the diode U1 outputs a voltage, and the No. 2 end of the diode U1 is electrically connected with the sampling circuit 4. In the embodiment, the diode U1 is a fast recovery diode, which can reduce the power loss of the output circuit 34.

[0064] Further, as shown in Figure 2 , the No. 2 end of the diode U1 is provided with a sampling point V_A, and the sampling point V_A is electrically connected with the sampling circuit 4; the No. 1 end of the resistor R6 is provided with a sampling point V_B, and the No. 2 end of the resistor R6 is provided with a sampling point V-, and the sampling points V_B and V- are respectively electrically connected with the sampling circuit 4.

[0065] When the MOS tube Q1 is turned on, the sampling circuit 4 further collects the voltage U 01 of the output circuit 34 through the sampling point V_A, collects the voltage value U R6（1） of the resistor R6, and transmits to the control circuit 2, and the control circuit 2 calculates the current I of the resistor R6 at this time, and then calculates the equivalent resistance R of the output circuit 34 working according to the formula ac1 , and calculates the gain Q at the same time.

[0066] When the MOS tube Q2 is turned on, the sampling circuit 4 further collects the voltage U O2 of the output circuit 34 through the sampling point V_A, collects the voltage value U R6（2） of the resistor R6, and transmits to the control circuit 2, and the control circuit 2 calculates the current I of the resistor R6 at this time, and then calculates the equivalent resistance R of the output circuit 34 working according to the formula ac2 , and calculates the gain Q at the same time; in the above formula, R is the resistance value of the resistor R6, n is the transformation ratio of the transformer, the control circuit calculates the average gain Q and the average equivalent resistance R ac according to Q1 and Q2, adjusts the average equivalent resistance R ac so that the average gain Q = 1. Wherein, the gain Q can reflect the energy loss of the circuit when working at the resonant frequency. When the gain Q = 1, i.e. the circuit enters the resonant state, the inductive control and the capacitive reactance are equal, at this time the circuit presents resistance, i.e. the energy storage and energy dissipation in the resonant circuit 3 reach the balance state, which is helpful to realize the ZVS of the MOS tube Q1 and the MOS tube Q2.

[0067] It should be noted that Q1 and Q2 are the circuit gains generated by the conduction of MOS Q1 and MOS Q2 in one cycle, and the average value of the gain Q needs to be calculated, which is the same as the above calculation of the average value of the resonance frequency F. Here is not described.

[0068] Specifically, as shown in Figure 3 The control circuit 2 includes a control chip 2, an oscillation module 22, a reset module 23, a filter module 24, a current limiting module 25, and a protection module 26. The control chip 21 has multiple ports, the oscillation module 22 is electrically connected to the 5th port and the 6th port of the control chip 21 respectively; the reset module 23 is electrically connected to the 7th port of the control chip 21, and the reset module 23 is also electrically connected to the power supply 1 and grounded SGND; the filter module 24 is electrically connected to the 9th port and the 30th port of the control chip 21, and the filter module 24 is grounded SGND; the current limiting module 25 is electrically connected to the 11th port and the 21st port of the control chip 21, and the current limiting module 25 is also electrically connected to the power supply 1 and grounded SGND; the protection module 26 is electrically connected to the 12th port and the 13th port of the control chip 21, and the protection module 26 is also electrically connected to the power supply 1 and grounded SGND.

[0069] The control chip 21 is used to process the voltage of the capacitor C7, the inductor L1 and the resistor R6 collected by the sampling circuit 4, and calculate the resonance frequencies f1 and f2 of the resonance cavity 32, and calculate the current i2 of the resistor R6 according to the resistance value of the resistor R6 and the voltage of the resistor R6, while controlling the MOS Q1 and the MOS Q1 to be alternately turned on according to the resonance frequencies f1 and f2; the oscillation module 22 provides a working clock signal, which provides a working time reference for the circuit, so that the circuit can work in order; the reset module 23 initializes the control chip 21, and when the program of the control chip 21 after power-on is not in the initial state, the reset module 23 can make the program of the control chip 21 start from the beginning; the filter module 24 is used to filter the voltage input to the control chip 21, which can be used to remove the noise in the voltage input to the control chip 21 by the power supply 1, to avoid affecting the normal work of the control chip 21; the current limiting module 25 is used to prevent overcurrent of the power supply 1; the protection module 26 plays a role of voltage stabilization for the control chip 21, so that the control chip 21 works more stably. In the embodiment, the control chip 21 adopts STM32F446.

[0070] Specifically, as shown in Figure 4 and Figure 5As shown, the sampling circuit 4 includes a capacitor voltage sampling circuit 41 and an inductor voltage sampling circuit 42, the capacitor voltage sampling circuit 41 is electrically connected with the detection points C_A and C_B respectively; the inductor voltage sampling circuit 42 is electrically connected with the detection points L_A and L_B respectively; wherein, the capacitor voltage sampling circuit 41 is used to collect the voltage U1 and U3 in the working state of the capacitor C7; the inductor voltage sampling circuit 42 is used to collect the voltage U2 and U4 in the working state of the inductor L1. It should be noted that the capacitor voltage sampling circuit 41 and the inductor voltage sampling circuit 42 use the differential sampling mode to have better anti-interference ability, so that the voltage of the capacitor C7 and the voltage of the inductor L1 can be accurately collected.

[0071] Specifically, as shown in Figure 6 and Figure 7 , the sampling circuit further includes an output voltage sampling circuit 43 and a resistance voltage sampling circuit 44, the output voltage sampling circuit 43 is electrically connected with the 2nd end of the diode U1; the resistance voltage sampling circuit 44 is electrically connected with the 1st end and the 2nd end of the resistance R6 respectively; wherein, the output voltage sampling circuit 43 is used to collect the voltage of the output circuit 34, and the resistance voltage sampling circuit 44 is used to collect the voltage of the resistance R6. It should be noted that the output voltage sampling circuit 43 uses a series resistance voltage dividing sampling circuit, and three resistances are connected in series in the embodiment, so that , wherein approximately equals the voltage output by the transformer 33 in the power supply U input resonant circuit; the resistance voltage sampling circuit 44 is consistent with the capacitor voltage sampling circuit 41 and the inductor voltage sampling circuit 42, which will not be described here.

[0072] In summary, the application sets the detection points C_A, C_B and the detection points L_A, L_B on the connection lines of the capacitor C7 and the inductor L1 respectively, so that the capacitor voltage sampling circuit 41 can detect the voltage of the capacitor C7 and the voltage on the connection line of the capacitor C7, and the inductor voltage sampling circuit 42 can detect the voltage of the inductor L1 and the voltage on the connection line of the inductor L1. Thus, the voltage of the capacitor C7 and the inductor L1 in the working state can be accurately collected, so that the control circuit 2 can calculate the resonant frequency of the resonant cavity 32 in the working state. And the switching frequency of the MOS tube Q1 and the MOS tube Q2 is adjusted to be equal to the resonant frequency, so that the MOS tube Q1 and the MOS tube Q2 can realize ZVS conduction, so as to reduce the power loss of the MOS tube Q1 and the MOS tube Q2 in the conduction state.

[0073] At the same time, the circuit enters the resonant state, better eliminates the harmonics existing in the square wave, reduces the noise interference existing in the output fundamental frequency sine wave of the output circuit, further improves the power conversion efficiency of the LLC circuit, and outputs more stable voltage to the power equipment.

[0074] The above merely illustrates the embodiments of the present application, but should not be taken as limitations. The present application can have various modifications and changes for those skilled in the art. Any modification, equivalent replacement, improvement, etc. within the spirit and principle of the present application should be included in the scope of claims of the present application.

Claims

1. A resonant cavity detection and dynamic adjustment circuit, characterized by, The application relates to a resonant circuit, which comprises the following components: a power supply (1); a control circuit (2) electrically connected with the power supply (1); a resonant circuit (3) comprising: a switching module (31) comprising a first switching element (311) and a second switching element (312), wherein the first switching element (311) is electrically connected with the power supply (1), the control circuit (2) and the second switching element (312) respectively, and the second switching element (312) is electrically connected with the control circuit (2); a resonant cavity (32) comprising a first resonant element (321) and a second resonant element (322), wherein the first resonant element (321) is electrically connected with the second switching element (312) and the second resonant element (322) respectively; a transformer (33), wherein the No.1 end of the transformer (33) is electrically connected with the first switching element (311) and the second switching element (312) respectively, and the No.2 end of the transformer (33) is electrically connected with the second resonant element (322); an output circuit (34) comprising a sampling element (341), wherein the sampling element (341) is electrically connected with the No.4 end of the transformer (33); and a sampling circuit (4) electrically connected with the control circuit (2), the second switching element (312), the first resonant element (321), the second resonant element (322), the transformer (33) and the sampling element (341) respectively. After the control circuit (2) is initialized, the initial resonant frequency f0 of the resonant cavity (32) is calculated, the control circuit (2) controls the first switching element (311) and the second switching element (312) to be alternately turned on according to the initial resonant frequency f0, when the first switching element (311) is turned on and the second switching element (312) is turned off, the sampling circuit (4) collects the voltages U1 and U2 of the first resonant element (321) and the second resonant element (322), and transmits the collected voltage values U1 and U2 to the control circuit (2), the control circuit (2) calculates the resonant frequency f1 of the resonant cavity (32) when working according to the voltage U1 of the first resonant element (321), the voltage U2 of the second resonant element (322) and the transformation ratio of the transformer (33) itself; when the second switching element (312) is turned on and the first switching element (311) is turned off, the sampling circuit (4) collects the voltages U3 and U4 of the first resonant element (321) and the second resonant element (322), and the control circuit (2) calculates the resonant frequency f2 of the resonant cavity (32) when working according to the voltage U3 of the first resonant element (321), the voltage U4 of the second resonant element (322) and the transformation ratio of the transformer (33) itself, the control circuit (2) calculates the average value F of the resonant frequency of the resonant cavity (32) when working according to f1 and f2, and then adjusts the switching frequency of the first switching element (311) and the second switching element (312) to be F.

2. The resonator detection and dynamic adjustment circuit according to claim 1, characterized in that The first switch element (311) comprises a MOS tube Q1, the second switch element (312) comprises a MOS tube Q2, the MOS tube Q1 and the MOS tube Q2 have a drain D, a gate G and a source S respectively, the first resonant element (321) comprises a capacitor C7, the second resonant element (322) comprises an inductor L1, the capacitor C7 and the inductor L1 have a No. 1 end and a No. 2 end; the drain D of the MOS tube Q1 is electrically connected with a power supply (1), the gate G of the MOS tube Q1 is electrically connected with a control circuit (2), the source S of the MOS tube Q1 is respectively electrically connected with a No. 1 end of a transformer (33) and a drain D of the MOS tube Q2; the drain D of the MOS tube Q2 is electrically connected with the No. 1 end of the transformer (33), the gate G of the MOS tube Q2 is electrically connected with the control circuit (2), the source S of the MOS tube Q2 is respectively electrically connected with a sampling circuit (4) and the No. 1 end of the capacitor C7; the No. 2 end of the capacitor C7 is electrically connected with the No. 1 end of the inductor L1, the No. 2 end of the inductor L1 is electrically connected with a No. 2 end of the transformer (33); The control circuit (2) reads the initial capacitance value C1 of the capacitor C7 and the inductance value L1 of the inductor L1 respectively, and calculates the initial resonance frequency of the resonance cavity (32) The control circuit (2) controls the MOS tube Q1 and the MOS tube Q2 to be alternately turned on according to the initial resonance frequency f0.

3. The resonator detection and dynamic adjustment circuit according to claim 2, characterized in that A voltage sampling point C_B of the capacitor C7 is arranged on the source S of the MOS tube Q2, another sampling point C_A of the capacitor C7 is arranged on the 1# end of the inductor L1, and the sampling points C_B and C_A are electrically connected with the sampling circuit (4) respectively; a sampling point L_A of the inductor L1 is arranged on the 2# end of the capacitor C7, another sampling point L_B of the inductor L1 is arranged on the 2# end of the transformer (33), and the sampling points L_A and L_B are electrically connected with the sampling circuit (4) respectively; when the MOS tube Q1 is turned on, the sampling circuit (4) transmits the voltage U1 of the capacitor C7 and the voltage U2 of the inductor L1 to the control circuit (2), the control circuit (2) calculates the dynamic capacitance of the capacitor C7 working , the dynamic inductance of the inductor L1 working , and then calculates ; When MOS transistor Q2 is turned on, the sampling circuit (4) transmits the voltage U3 of the capacitor C7 and the voltage U4 of the inductor L1 to the control circuit (2), which calculates the dynamic capacitance of the capacitor C7 and the dynamic inductance of the inductor L1 and calculates in the above formula, i1 is the inverse of the transformer (33) ratio, and j is the imaginary unit. The control circuit (2) calculates an average value F of the resonant frequency of the resonant cavity (32) in operation according to f1 and f2, and then adjusts the switching frequency of the MOS tube Q1 and the MOS tube Q2 to F.

4. The resonator detection and dynamic adjustment circuit according to claim 3, characterized in that The sampling element (341) comprises a resistor R6, the resistor R6 has a No. 1 end and a No. 2 end, the No. 1 end of the resistor R6 is electrically connected with a No. 4 end of the transformer (33), the No. 2 end of the resistor R6 outputs a voltage, and the No. 1 end and the No. 2 end of the resistor R6 are respectively electrically connected with the sampling circuit (4).

5. The resonator detection and dynamic adjustment circuit of claim 4, wherein, The output circuit (34) further comprises a reverse protection element (342), the reverse protection element (342) comprises a diode U1, the diode U1 has a No. 1 end and a No. 2 end, the No. 1 end of the diode U1 is electrically connected with a No. 3 end of the transformer (33), the No. 2 end of the diode U1 outputs a voltage, and the No. 2 end of the diode U1 is electrically connected with the sampling circuit (4).

6. The resonator detection and dynamic adjustment circuit according to claim 5, characterized in that The No. 2 end of the diode U1 is provided with a sampling point V_A, the sampling point V_A is electrically connected with the sampling circuit (4); the No. 1 end of the resistor R6 is provided with a sampling point V_B, the No. 2 end of the resistor R6 is provided with a sampling point V-, and the sampling point V_B and the sampling point V- are respectively electrically connected with the sampling circuit (4); When MOS transistor Q1 is turned on, the sampling circuit (4) also collects the voltage U of the output circuit (34) through the sampling point V_A. 01 The sampling circuit (4) collects the voltage value U of resistor R6. R6（1） The current is transmitted to the control circuit (2), which calculates the current in resistor R6 at this time. The control circuit (2) then according to Calculate the equivalent resistance R of the output circuit (34) during operation. ac1 Simultaneously calculate the gain ; When MOSFET Q2 is turned on, the sampling circuit (4) also collects the voltage U of the output circuit (34) through the sampling point V_A. 02 The sampling circuit (4) collects the voltage value U of resistor R6. R6（2） The current is transmitted to the control circuit (2), which calculates the current in resistor R6 at this time. The control circuit (2) then according to Calculate the equivalent resistance R of the output circuit (34) during operation. ac2 Simultaneously calculate the gain In the above formula, R is the resistance of resistor R6, n is the turns ratio of transformer (33), and the control circuit (2) calculates the average gain Q based on Q1 and Q2, and calculates the average gain Q based on R. ac1 and R ac2 Calculate the average equivalent resistance R ac Then the control circuit (2) adjusts the average equivalent resistance R. ac This makes the average gain Q=1.

7. The resonator detection and dynamic adjustment circuit of claim 1, wherein, The control circuit (2) comprises a control chip (21), an oscillation module (22), a reset module (23), a filter module (24), a current limiting module (25) and a protection module (26), the control chip (21) has a plurality of ports, the oscillation module (22) is electrically connected with the No. 5 port and the No. 6 port of the control chip (21) respectively; the reset module (23) is electrically connected with the No. 7 port of the control chip (21), and the reset module (23) is also electrically connected with the power supply (1) and grounded SGND; the filter module (24) is electrically connected with the No. 9 port and the No. 30 port of the control chip (21), and the filter module (24) is grounded SGND; the current limiting module (25) is electrically connected with the No. 11 port and the No. 21 port of the control chip (21), and the current limiting module (25) is also electrically connected with the power supply (1) and grounded SGND; the protection module (26) is electrically connected with the No. 12 port and the No. 13 port of the control chip (21), and the protection module (26) is also electrically connected with the power supply (1) and grounded SGND.

8. The resonator detection and dynamic adjustment circuit of claim 6, wherein, The sampling circuit (4) comprises a capacitor voltage sampling circuit (41) and an inductor voltage sampling circuit (42), the capacitor voltage sampling circuit (41) is electrically connected with the detection points C_A and C_B respectively; the inductor voltage sampling circuit (42) is electrically connected with the detection points L_A and L_B respectively; wherein the capacitor voltage sampling circuit (41) is used to collect the voltages U1 and U3 in the working of the capacitor C7; the inductor voltage sampling circuit (42) is used to collect the voltages U2 and U4 in the working of the inductor L1.

9. The resonator detection and dynamic adjustment circuit of claim 6, wherein, The sampling circuit (4) further comprises an output voltage sampling circuit (43) and a resistance voltage sampling circuit (44), the output voltage sampling circuit (43) is electrically connected with the No. 2 port of the diode U1; the resistance voltage sampling circuit (44) is electrically connected with the No. 1 port and the No. 2 port of the resistance R6 respectively; wherein the output voltage sampling circuit (43) is used to collect the voltage of the output circuit (34), and the resistance voltage sampling circuit (44) is used to collect the voltage of the resistance R6.

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