Resonant converter based on digital power inductor and working method thereof

Abstract

The invention relates to a resonant converter based on a digital power inductor and a working method thereof. The resonant converter comprises a rectification inversion module and a resonant cavity module. Wherein the rectification inversion module comprises primary side full-bridge loop switch tubes S1, S2, S3 and S4, secondary side full-bridge loop switch tubes S5, S6, S7 and S8, and filter capacitors Cin and Co; the resonant cavity module comprises a primary side resonant inductor Lrp, a primary side resonant capacitor Crp, a secondary side resonant inductor Lrs, a secondary side resonant capacitor Crs and a high-frequency transformer T. The primary side resonant inductor Lrp and the secondary side resonant inductor Lrs are both digital power inductors. According to the resonant converter, the inductance value of the digital power inductor is adjusted under different output voltage requirements, so that the ratio of the resonant inductor to the excitation inductor is adjusted, the loss of the resonant cavity is reduced, and the CLLC resonant converter can maintain relatively high conversion efficiency in a full-load range.

Description

Technical Field

[0001] The invention belongs to the field of electronics, and in particular relates to a resonant converter based on a digital power inductor and a working method thereof. Background Art

[0002] With the continuous development of new energy technology and electric vehicle charging technology, bidirectional DC / DC converters with low loss, high power density and high reliability have become a hot topic of research. CLLC resonant converters stand out among many bidirectional DC / DC converters due to their characteristics of easy soft switching, wide voltage gain range, relatively simple control method and high power density, and are widely used in electric vehicles, renewable energy and power electronic transformers. The traditional CLLC resonant converter has a limited range of change in its conversion voltage gain curve due to the fixed parameters of the resonant cavity. This fixity makes it difficult for the converter to achieve dynamic adjustment under different load conditions and cannot effectively respond to the needs of load changes in actual applications. Therefore, the adaptability of the converter in diversified application scenarios is restricted. In the design of traditional CLLC resonant converters, in order to meet the maximum gain under harsh working conditions and obtain a wider voltage gain range, the ratio between the resonant inductance and the excitation inductance is usually increased to achieve this, which will increase the loss of the resonant cavity. In addition, in actual operation, the converter usually operates near the rated voltage, and rarely works under harsh working conditions. Therefore, in order to meet the design requirements, part of the converter's conversion efficiency at light load is sacrificed. Summary of the invention

[0003] In order to overcome the deficiencies in the prior art, the present invention proposes a CLLC resonant converter based on a digital power inductor and a working method thereof. In the operation of the CLLC converter, due to the use of a digital power inductor, the converter voltage gain curve is no longer single, and the gain range can be changed by changing the inductance value, thereby overcoming the design limitations of the resonant cavity of the existing CLLC converter. At the same time, the present invention can adjust the inductance of the digital power inductor under different output voltage requirements, thereby adjusting the ratio of the resonant inductance to the excitation inductance, reducing the resonant cavity loss, and enabling the CLLC resonant converter to maintain a higher conversion efficiency under the full load range.

[0004] To achieve the above object, the technical solution of the present invention is: a CLLC resonant converter based on a digital power inductor, characterized in that it includes a rectifier inverter module and a resonant cavity module; the rectifier inverter module and the resonant cavity module are connected, wherein:

[0005] The rectifier and inverter module can realize the converter power input terminal V in and output terminal V o The bidirectional rectification and inversion function;

[0006] The resonant cavity module adopts a digital power inductor with adjustable inductance, which can increase or decrease the resonant frequency of the converter circuit, and can realize the voltage regulation function of controlling the increase and decrease of the output voltage, and the converter circuit is in the magnetic core during operation.

[0007] In a preferred embodiment, the rectifier inverter module includes a first primary full-bridge loop switch tube S1, a second primary full-bridge loop switch tube S2, a third primary full-bridge loop switch tube S3, a fourth primary full-bridge loop switch tube S4, a first secondary full-bridge loop switch tube S5, a second secondary full-bridge loop switch tube S6, a third secondary full-bridge loop switch tube S7, a fourth secondary full-bridge loop switch tube S8, and a filter capacitor C in and C o ; The resonant cavity module includes the primary resonant inductor L rp , primary resonant capacitor C rp , secondary side resonant inductor L rs , secondary side resonant capacitor C rs , high frequency transformer T, where the primary resonant inductor L rp and the secondary resonant inductor L rs Both are digital power inductors.

[0008] The rectifier inverter module also includes:

[0009] Power supply V in One end of the input end is connected to the drain of the first primary full-bridge loop switch tube S1 and the third primary full-bridge loop switch tube S3, and the other end is connected to the source of the second primary full-bridge loop switch tube S2 and the fourth primary full-bridge loop switch tube S4. The source of the first primary full-bridge loop switch tube S1 is connected to the drain of the second primary full-bridge loop switch tube S2 as the primary full-bridge output end a, the source of the third primary full-bridge loop switch tube S3 is connected to the drain of the fourth primary full-bridge loop switch tube S4 as the primary full-bridge output end b, and the first The drain of the second secondary full-bridge loop switch tube S6 of the secondary full-bridge loop switch tube S5 is connected to the secondary full-bridge input terminal c, and the source of the third secondary full-bridge loop switch tube S7 and the drain of the fourth secondary full-bridge loop switch tube S8 are connected to the secondary full-bridge input terminal d; the drains of the first secondary full-bridge loop switch tube S5 and the third secondary full-bridge loop switch tube S7 are connected to the positive electrode of the load, and the sources of the second secondary full-bridge loop switch tube S6 and the fourth secondary full-bridge loop switch tube S8 are connected to the negative electrode of the load.

[0010] The resonant cavity module further includes:

[0011] The primary digital power inductor L in the resonant cavity rp One end is connected to the inverter bridge output terminal a, and the other end is connected to the same end of the primary winding of the high-frequency transformer T. The primary resonant capacitor C rpOne end is connected to the inverter bridge output terminal b, and the other end is connected to the non-same-name end of the primary winding of the high-frequency transformer T; the secondary digital power inductor L in the resonant cavity rs One end is connected to the input terminal c of the rectifier bridge, and the other end is connected to the same end of the secondary winding of the high-frequency transformer T. The secondary resonant capacitor C rs One end is connected to the input terminal d of the rectifier bridge, and the other end is connected to the non-same-name end of the secondary winding of the high-frequency transformer T;

[0012] Among them, the resonant frequency of the resonant inductor and the resonant capacitor in the resonant cavity is the resonant frequency of the converter circuit;

[0013] Among them, the resonant cavity adopts a symmetrical structure, and the relationship between the primary inductor and the secondary inductor is L rp =n 2 L rs , the relationship between the primary capacitance and the secondary capacitance is C rp =C rs / n 2 ; Among them, n is the transformation ratio of the primary side to the secondary side of the high-frequency transformer T, n = the number of turns of the primary coil of the transformer / the number of turns of the secondary coil of the transformer.

[0014] The rectifier inverter module has a forward working mode, and its working mode characteristics include:

[0015] When working in the forward direction, the primary full bridge works in the inverter mode, and the secondary full bridge works in the rectification mode; the driving signals of the first primary full bridge loop switch tube S1 and the fourth primary full bridge loop switch tube S4 are the same, the driving signals of the second primary full bridge loop switch tube S2 and the third primary full bridge loop switch tube S3 are the same, the driving signals of the first primary full bridge loop switch tube S1 and the second primary full bridge loop switch tube S2 are complementary, and the driving signals of the third primary full bridge loop switch tube S3 and the fourth primary full bridge loop switch tube S4 are complementary; the first secondary full bridge loop switch tube S5, the second secondary full bridge loop switch tube S6, the third secondary full bridge loop switch tube S7, and the fourth secondary full bridge loop switch tube S8 of the switch tube are synchronously driven according to the secondary current direction, with i s The direction of the arrow is positive. In the forward direction, the first secondary full-bridge loop switch tube S5 and the fourth secondary full-bridge loop switch tube S8 are turned on, and the second secondary full-bridge loop switch tube S6 and the third secondary full-bridge loop switch tube S7 are turned off. In the reverse direction, the second secondary full-bridge loop switch tube S6 and the third secondary full-bridge loop switch tube S7 are turned on, and the first secondary full-bridge loop switch tube S5 and the fourth secondary full-bridge loop switch tube S8 are turned off.

[0016] The rectifier inverter module also has a reverse working mode, and its working mode features include:

[0017] When working in reverse, the primary full bridge works in rectification mode, and the secondary full bridge works in inverter mode; the driving signals of the first secondary full bridge loop switch tube S5 and the fourth secondary full bridge loop switch tube S8 are the same, the driving signals of the second secondary full bridge loop switch tube S6 and the third secondary full bridge loop switch tube S7 are the same, the driving signals of the first secondary full bridge loop switch tube S5 and the second secondary full bridge loop switch tube S6 are complementary, and the driving signals of the third secondary full bridge loop switch tube S7 and the fourth secondary full bridge loop switch tube S8 are complementary; the first primary full bridge loop switch tube S1, the second primary full bridge loop switch tube S2, the third primary full bridge loop switch tube S3, and the fourth primary full bridge loop switch tube S4 of the switch tube are synchronously driven according to the secondary current direction, with i p The direction of the arrow is negative. In the positive direction, the first primary full-bridge loop switch tube S1 and the fourth primary full-bridge loop switch tube S4 are turned on, and the second primary full-bridge loop switch tube S2 and the third primary full-bridge loop switch tube S3 are turned off. In the reverse direction, the second primary full-bridge loop switch tube S2 and the third primary full-bridge loop switch tube S3 are turned on, and the first primary full-bridge loop switch tube S1 and the fourth primary full-bridge loop switch tube S4 are turned off.

[0018] The resonant cavity includes a primary resonant inductor L rp , primary resonant capacitor C rp , secondary side resonant inductor L rs , secondary side resonant capacitor C rs , high frequency transformer T, where the primary resonant inductor L rp and the secondary resonant inductor L rs All of them are digital power inductors; the characteristics of digital power inductors are as follows:

[0019] The internal structure of the digital power inductor includes a built-in control port and a magnetic column with an adjustable equivalent cross-sectional area; the inductance of the port is controlled by the control port, and the magnetic column controls the signal terminal S of the switch. ctrl Used to drive the signal MOSFET to control the winding L ctrl When the control winding is short-circuited, the magnetic block corresponding to the inductor is disconnected; therefore, through different magnetic column equivalent cross-sectional areas A e The design can realize the increase or decrease of the inductance of the digital power inductor; at the same time, because the magnetic core column only works in the on and off states, the digital power inductor works in an unsaturated state;

[0020] Among them, the control port of the digital power inductor can be controlled by an external information signal via a driving circuit, without the need for an additional external power supply and sampling circuit.

[0021] The resonant cavity includes a primary resonant inductor L rp , primary resonant capacitor C rp, secondary side resonant inductor L rs , secondary side resonant capacitor C rs , high frequency transformer T, where the characteristics of the resonant frequency are as follows:

[0022] The resonant frequency of the resonant inductor and the resonant capacitor in the resonant cavity is the resonant frequency of the CLLC converter. According to the characteristics of the electronic devices in the resonant cavity, the resonant frequency of the CLLC converter is obtained by the fundamental wave analysis method.

[0023]

[0024] where f r is the resonant frequency, L r is the equivalent inductance of the resonant cavity, C r is the equivalent capacitance of the resonant cavity;

[0025] According to the characteristics of the electronic devices of the resonant cavity, the equivalent circuit of the resonant cavity is obtained through the principle of conservation of electromagnetic energy between the primary and secondary sides; the connection relationship of each device is: L P is the primary equivalent resonant inductance, L s is the secondary side equivalent resonant inductance, L m is the equivalent magnetizing inductance, C P is the primary equivalent capacitance, C s is the secondary side equivalent capacitance, U1 is the primary side equivalent circuit input voltage, U2 is the secondary side equivalent circuit output voltage,

[0026] The current inflow is positive, L P The positive terminal of is connected to the positive terminal of U1, L P The negative terminal and L s The positive terminal and L m The positive terminals of the three are connected at one point, L m The negative terminal of C P One end and C s The three ends are connected at one point, L s The negative terminal of C is connected to the positive terminal of U2. P The other end is connected to the negative terminal of U1, C s One end of is connected to the negative terminal of U2;

[0027] When the converter operates at the resonant frequency, the resonant cavity current is a sine wave, the resonant cavity equivalent complex impedance is zero, and the reactive loss is minimal;

[0028] Further, the voltage gain expression of the CLLC converter is obtained by the fundamental wave analysis method:

[0029]

[0030]

[0031] Among them, M is the resonant cavity voltage gain, U1 is the primary equivalent circuit input voltage, U2 is the secondary equivalent circuit output voltage, X p is the primary equivalent reactance, X s is the secondary side equivalent reactance, X m is the equivalent excitation reactance, R eq is the output load equivalent resistance;

[0032] Voltage gain expression M(f n ,Q,k), f n is the converter resonant frequency, and the inductance ratio k is L p Primary side equivalent inductance and L m Ratio of magnetizing inductance to characteristic impedance Quality factor Q = Z / R eq .

[0033] In summary, a CLLC resonant converter based on a digital power inductor has three operating modes, including the following:

[0034] The CLLC resonant converter has three operating modes: under-resonance, quasi-resonance and over-resonance. The operating frequency is divided by the resonant frequency. When the operating frequency is at the resonant frequency, it is the quasi-resonance mode; when the operating frequency is less than the resonant frequency, it is the under-resonance mode; when the operating frequency is greater than the resonant frequency, it is the over-resonance mode.

[0035] In addition, the converter has two control methods to achieve output voltage control, the contents of the control methods are as follows:

[0036] When the converter works in the following method, the converter will adjust the inductance of the digital power inductor according to the output voltage required in real time, and finally adjust the external output voltage and frequency of the converter; wherein:

[0037] 1) When the output voltage gain needs to be increased, the inductance of the primary resonant inductor and the secondary resonant inductor is increased according to the preset value, and the operating frequency is adjusted according to the specific output voltage;

[0038] 2) When the output voltage gain needs to be reduced, the inductance of the primary resonant inductor and the secondary resonant inductor is reduced according to the preset value, and the operating frequency is adjusted according to the specific output voltage;

[0039] When the converter works under method 2, the converter will change the resonant frequency by changing the resonant inductance value, and output a voltage value of the working point that meets the rated resonant frequency; wherein:

[0040] (1) When the output voltage is greater than the target voltage, the inductance of the primary resonant inductor and the secondary resonant inductor is increased, the resonant frequency of the resonant converter is reduced, the converter operates in the over-resonance region, and the output voltage of the converter is reduced;

[0041] (2) When the output voltage is lower than the target voltage, the inductance of the primary resonant inductor and the secondary resonant inductor is reduced, the resonant frequency of the resonant converter is increased, the converter operates in the under-resonance region, and the output voltage of the converter is increased.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] 1. The present invention adopts digital power inductor, so the voltage gain curve of the converter is not single, and the gain range can be changed by changing the inductance value, thereby overcoming the limitations of the resonant cavity design of the existing CLLC converter.

[0044] 2. This patent can adjust the inductance of the digital power inductor under different output voltage requirements. By adding multiple magnetic columns to the inductor to form a control port, a wider range of inductance adjustment can be achieved, the resonant cavity loss can be reduced, and the CLLC resonant converter can maintain a higher conversion efficiency under the full load range.

[0045] 3. Since the magnetic core of the digital power inductor only works in the on and off states, and not in the saturation state, it overcomes the problem of excessive loss in traditional saturated inductors.

[0046] 4. In the digital power inductor control process adopted by the present invention, no additional external power supply and sampling circuit are required.

[0047] 5. In addition to being applicable to CLLC resonant converters, this patent is also applicable to combination topologies of other resonant converters. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a CLLC resonant converter topology based on a digital power inductor of the present invention.

[0049] Figure 2 It is a structural diagram of the array power inductor of the present invention.

[0050] Figure 3 This is the equivalent magnetic circuit diagram of the digital power inductor of the present invention.

[0051] Figure 4 This is a schematic diagram of the magnetic column control switch of the present invention.

[0052] Figure 5 It is the equivalent circuit diagram of the resonant cavity of the CLLC resonant converter of the present invention.

[0053] Figure 6 This is a diagram showing the effect of the change in resonant inductance on the resonant frequency of the present invention.

[0054] Figure 7This is a diagram showing the effect of the change in resonant inductance on the gain curve of the present invention.

[0055] Figure 8 This is a waveform diagram of the under-resonance working mode of the present invention.

[0056] Fig. 9 This is a topology diagram of the parallel CLLC resonant converter of the present invention. DETAILED DESCRIPTION

[0057] The technical solution of the present invention is described in detail below in conjunction with the accompanying drawings.

[0058] like Figure 1 The CLLC resonant converter based on the digital power inductor is characterized in that the rectifier inverter module includes a first primary full-bridge loop switch tube S1, a second primary full-bridge loop switch tube S2, a third primary full-bridge loop switch tube S3, a fourth primary full-bridge loop switch tube S4, a first secondary full-bridge loop switch tube S5, a second secondary full-bridge loop switch tube S6, a third secondary full-bridge loop switch tube S7, a fourth secondary full-bridge loop switch tube S8, and a filter capacitor C in and C o ; The resonant cavity module includes the primary resonant inductor L rp , primary resonant capacitor C rp , secondary side resonant inductor L rs , secondary side resonant capacitor C rs , high frequency transformer T, where the primary resonant inductor L rp and the secondary resonant inductor L rs Both are digital power inductors.

[0059] The relationship between the rectifier inverter module and external devices includes:

[0060] Power supply V inOne end of the input end is connected to the drain of the first primary full-bridge loop switch tube S1 and the third primary full-bridge loop switch tube S3, and the other end is connected to the source of the second primary full-bridge loop switch tube S2 and the fourth primary full-bridge loop switch tube S4. The source of the first primary full-bridge loop switch tube S1 is connected to the drain of the second primary full-bridge loop switch tube S2 as the primary full-bridge output end a, the source of the third primary full-bridge loop switch tube S3 is connected to the drain of the fourth primary full-bridge loop switch tube S4 as the primary full-bridge output end b, and the first The drain of the second secondary full-bridge loop switch tube S6 of the secondary full-bridge loop switch tube S5 is connected to the secondary full-bridge input terminal c, and the source of the third secondary full-bridge loop switch tube S7 is connected to the drain of the fourth secondary full-bridge loop switch tube S8 as the secondary full-bridge input terminal d; the drains of the first secondary full-bridge loop switch tube S5 and the third secondary full-bridge loop switch tube S7 are connected to the positive electrode of the load, and the sources of the second secondary full-bridge loop switch tube S6 and the fourth secondary full-bridge loop switch tube S8 are connected to the negative electrode of the load. The relationship between the resonant cavity module and the external devices includes:

[0061] The primary digital power inductor L in the resonant cavity rp One end is connected to the inverter bridge output terminal a, and the other end is connected to the same end of the primary winding of the high-frequency transformer T. The primary resonant capacitor C rp One end is connected to the inverter bridge output terminal b, and the other end is connected to the non-same-name end of the primary winding of the high-frequency transformer T; the secondary digital power inductor L in the resonant cavity rs One end is connected to the input terminal c of the rectifier bridge, and the other end is connected to the same end of the secondary winding of the high-frequency transformer T. The secondary resonant capacitor C rs One end is connected to the input terminal d of the rectifier bridge, and the other end is connected to the non-same-name end of the secondary winding of the high-frequency transformer T;

[0062] Among them, the resonant frequency of the resonant inductor and the resonant capacitor in the resonant cavity is the resonant frequency of the converter circuit;

[0063] Among them, the resonant cavity adopts a symmetrical structure, and the relationship between the primary inductor and the secondary inductor is L rp =n 2 L r , the relationship between the primary capacitance and the secondary capacitance is C rp =C rs / n 2 ; Where n is the transformation ratio of the primary to the secondary side of the transformer, n = number of turns of the primary coil of the transformer / number of turns of the secondary coil of the transformer.

[0064] The rectifier inverter module has a forward working mode, and its working mode characteristics include:

[0065] When working in the forward direction, the primary full bridge works in the inverter mode, and the secondary full bridge works in the rectification mode; the driving signals of the first primary full bridge loop switch tube S1 and the fourth primary full bridge loop switch tube S4 are the same, the driving signals of the second primary full bridge loop switch tube S2 and the third primary full bridge loop switch tube S3 are the same, the driving signals of the first primary full bridge loop switch tube S1 and the second primary full bridge loop switch tube S2 are complementary, and the driving signals of the third primary full bridge loop switch tube S3 and the fourth primary full bridge loop switch tube S4 are complementary; the first secondary full bridge loop switch tube S5, the second secondary full bridge loop switch tube S6, the third secondary full bridge loop switch tube S7, and the fourth secondary full bridge loop switch tube S8 of the switch tube are synchronously driven according to the secondary current direction, with i s The direction of the arrow is positive. In the forward direction, the first secondary full-bridge loop switch tube S5 and the fourth secondary full-bridge loop switch tube S8 are turned on, and the second secondary full-bridge loop switch tube S6 and the third secondary full-bridge loop switch tube S7 are turned off. In the reverse direction, the second secondary full-bridge loop switch tube S6 and the third secondary full-bridge loop switch tube S7 are turned on, and the first secondary full-bridge loop switch tube S5 and the fourth secondary full-bridge loop switch tube S8 are turned off.

[0066] The rectifier inverter module also has a reverse working mode, and its working mode features include:

[0067] When working in reverse, the primary full bridge works in rectification mode, and the secondary full bridge works in inverter mode; the driving signals of the first secondary full bridge loop switch tube S5 and the fourth secondary full bridge loop switch tube S8 are the same, the driving signals of the second secondary full bridge loop switch tube S6 and the third secondary full bridge loop switch tube S7 are the same, the driving signals of the first secondary full bridge loop switch tube S5 and the second secondary full bridge loop switch tube S6 are complementary, and the driving signals of the third secondary full bridge loop switch tube S7 and the fourth secondary full bridge loop switch tube S8 are complementary; the first primary full bridge loop switch tube S1, the second primary full bridge loop switch tube S2, the third primary full bridge loop switch tube S3, and the fourth primary full bridge loop switch tube S4 of the switch tube are synchronously driven according to the primary current direction, with i p The direction of the arrow is negative. In the positive direction, the first primary full-bridge loop switch tube S1 and the fourth primary full-bridge loop switch tube S4 are turned on, and the second primary full-bridge loop switch tube S2 and the third primary full-bridge loop switch tube S3 are turned off. In the reverse direction, the second primary full-bridge loop switch tube S2 and the third primary full-bridge loop switch tube S3 are turned on, and the first primary full-bridge loop switch tube S1 and the fourth primary full-bridge loop switch tube S4 are turned off.

[0068] like Figure 2 , Figure 3 and Figure 4As shown, the working characteristics of the digital power inductor are as follows: the inductance of the power inductor port is controlled by the control port, and the signal terminal S of the magnetic column control switch ctrl Used to drive the signal MOSFET to control the winding L ctrl When the control winding is short-circuited, the magnetic block corresponding to the inductor is opened.

[0069] Therefore, through different magnetic column equivalent cross-sectional area A e The design can realize digital adjustable power inductance. Since the magnetic core works in the on and off states instead of the saturation state, the problem of excessive loss of traditional saturation reactors is overcome. Through the above digital power inductor, the resonant cavity can achieve a wide range of low-loss resonant inductance adjustment.

[0070] like Figure 5 The equivalent circuit of the CLLC converter resonant cavity shown in the figure shows that the resonant frequency of the CLLC converter is:

[0071]

[0072] where f r is the resonant frequency, L r is the equivalent inductance of the resonant cavity, C r is the equivalent capacitance of the resonant cavity;

[0073] According to the characteristics of the electronic devices of the resonant cavity, the equivalent circuit of the resonant cavity is obtained through the principle of conservation of electromagnetic energy between the primary and secondary sides; the connection relationship of each device is: L P is the primary equivalent resonant inductance, L s is the secondary side equivalent resonant inductance, L m is the equivalent magnetizing inductance, C P is the primary equivalent capacitance, C s is the secondary side equivalent capacitance, U1 is the primary side equivalent circuit input voltage, U2 is the secondary side equivalent circuit output voltage,

[0074] The current inflow is positive, L P The positive terminal of is connected to the positive terminal of U1, L P The negative terminal and L s The positive terminal and L m The positive terminals of the three are connected at one point, L m The negative terminal of C P One end and C s The three ends are connected at one point, L s The negative terminal of C is connected to the positive terminal of U2. P The other end is connected to the negative terminal of U1, C s One end of is connected to the negative terminal of U2;

[0075] When the converter operates at the resonant frequency, the resonant cavity current is a sine wave, the resonant cavity equivalent complex impedance is zero, and the reactive loss is minimal;

[0076] Further, the voltage gain expression of the CLLC converter is obtained by the fundamental wave analysis method:

[0077]

[0078]

[0079] Among them, M is the resonant cavity voltage gain, U1 is the primary equivalent circuit input voltage, U2 is the secondary equivalent circuit output voltage, X p is the primary equivalent reactance, X s is the secondary side equivalent reactance, X m is the equivalent excitation reactance, R eq is the output load equivalent resistance;

[0080] Voltage gain expression M(f n ,Q,k), f n is the converter resonant frequency, and the inductance ratio k is L p Primary side equivalent inductance and L m Ratio of magnetizing inductance to characteristic impedance Quality factor Q = Z / R eq .

[0081] By changing the inductance of the digital power inductor, the inductance ratio can be adjusted, and by changing the inductance of the resonant inductor, the resonant frequency can also be adjusted, bringing more possibilities for output voltage control methods. The present invention realizes voltage regulation through the following two technical solutions.

[0082] Experimental demonstration

[0083] In summary, a CLLC resonant converter based on a digital power inductor is characterized in that the converter has three working modes, including the following:

[0084] The CLLC resonant converter has three operating modes: under-resonance, quasi-resonance and over-resonance. The operating frequency is divided by the resonant frequency. When the operating frequency is at the resonant frequency, it is the quasi-resonance mode; when the operating frequency is less than the resonant frequency, it is the under-resonance mode; when the operating frequency is greater than the resonant frequency, it is the over-resonance mode.

[0085] In addition, the converter has two control methods to achieve output voltage control, the contents of the control methods are as follows:

[0086] When the converter works in the method 1, the converter will adjust the inductance of the digital power inductor according to the output voltage required in real time, and finally adjust the external output voltage and frequency of the converter; the details of the method 1 are as follows:

[0087] Method 1:

[0088] Step 1: According to the CLLC converter component parameters, i.e., circuit resonant inductance, resonant capacitance, and load resistance, determine the maximum output voltage gain M of the preset under-resonance mode. max and the minimum value M min , the interval M min ≤M≤M max The voltage gain in the inner part is divided into [M1=M min ,M2),[M2,M3),[M3,M4)……[M N-1 ,M N ),[M N ,M N+1＝ M max ], N voltage gain intervals (N = 2^bits can be set according to the number of bits of the digital power inductor).

[0089] Step 2: Determine the inductance of the digital power inductor based on the preset output voltage requirement. The specific solution is: N ~M N+1 When within the range, the inductance output L N . The inductance output is determined by the state of the digital power inductor switch. When the switch is closed, it is 1, and the magnetic resistance of the control winding where the switch is located is disconnected; when the switch is open, it is 0, and the magnetic resistance of the control winding where the switch is located is connected. In one embodiment of the present invention, the output inductance is determined by the switches Q1-Q4 of the digital power inductor control port, and the inductance of the digital power inductor is adjusted by changing the switch state (0000, 0001, ..., 1110, 1111). For example, when the output voltage gain is within [M3, M4), the output inductance is L3. At this time, the switch tube state is 0011, and the inductance formula is L N =N L 2 / R mN , where N L is the number of coil turns, R m is the magnetic resistance of the magnetic circuit. Figure 3 According to the switch state, the magnetic resistance R m3 =R0 / / (R e / 8) / / (R e / 4), at this time L3=N L 2 / R m3A wider range of inductance adjustment can be achieved by adding multiple magnetic columns to the inductor to form a control port.

[0090] Step 3: Adjust the inductance of the digital power inductor according to the output voltage required in real time, as follows:

[0091] 1) When the output voltage gain needs to be increased, the inductance of the primary resonant inductor and the secondary resonant inductor is increased according to the preset value, and the operating frequency is adjusted according to the specific output voltage.

[0092] 2) When the output voltage gain needs to be reduced, the inductance of the primary resonant inductor and the secondary resonant inductor is reduced according to the preset value, and the operating frequency is adjusted according to the specific output voltage.

[0093] like Figure 6 and Figure 7 , according to the output voltage range, the resonant inductor size is adjusted to achieve the change of the voltage gain curve. Considering the reduction of the resonant cavity loss, the CLLC resonant converter can maintain a higher conversion efficiency under the full load range.

[0094] The embodiment of method 1 only takes the under-resonance mode as an example to analyze the working principle of the CLLC converter. Since the waveform of the first half cycle and the second half cycle in a switching cycle of the under-resonance mode is symmetrical, this embodiment only analyzes the working principle of the CLLC converter. Figure 8 The first half cycle of the sub-resonant mode is analyzed during the time period t0-t4.

[0095] like Figure 8 As shown, at time t0, the switch tubes S1 and S4 are turned on, and the voltage across the primary full-bridge output a and b is the input voltage V in , the resonant current i flowing through the primary inductor p Increases according to the sine law, the equivalent excitation inductance L m The current i m The secondary switch tubes S5 and S8 are turned on for rectification. At this time, the voltage across the secondary full-bridge input c and d is clamped to the output voltage V o At time t1, the primary resonant current i p It drops to 0 and then changes direction until the moment t2, when the primary resonant current i p Equal to the excitation current i m During the time t0-t2, only the primary resonant inductance L rp , primary resonant capacitor C rp , secondary side resonant inductor L rs , secondary side resonant capacitor C rs Participate in the resonance process.

[0096] During t2-t3, the primary resonant current i p Equal to the excitation current i m, making the secondary resonant current zero and all the secondary switch tubes turned off. Therefore, during the t2-t3 process, only the primary resonant inductor L rp , primary resonant capacitor C rp and equivalent excitation inductance L m At time t3, S1 and S4 are turned off, and at this time, all the switch tubes in the CLLC converter are in the off state, which is the dead time.

[0097] During t3-t4, all switches are in the off state, and the primary resonant current i p Start charging the parasitic capacitance of S1 and S4, and discharge the parasitic capacitance of S2 and S3. At t4, the parasitic capacitance charging process of S1 and S4 is completed, and the drain-source voltage is equal to V in ; The parasitic capacitance discharge process of S2 and S3 is completed, and the primary resonant current i p Through the body diodes of S2 and S3, the drain-source voltage is zero, so zero voltage turn-on can be achieved at this stage. At this time, the voltage at the output terminals a and b of the primary bridge is -V in , the voltage at the secondary bridge input terminals c and d is -V o , entering the second half of the cycle.

[0098] The details of method 2 are as follows:

[0099] Method 2:

[0100] The CLLC resonant converter operates at a resonant frequency as the rated operating point, and the output voltage is adjusted at this operating point by changing the resonant inductance value.

[0101] (1) When the output voltage is greater than the target voltage, the inductance of the primary resonant inductor and the secondary resonant inductor is increased, the resonant frequency of the resonant converter is reduced, the converter operates in the over-resonance region, and the output voltage of the converter is reduced.

[0102] (2) When the output voltage is lower than the target voltage, the inductance of the primary resonant inductor and the secondary resonant inductor is reduced, the resonant frequency of the resonant converter is increased, the converter operates in the under-resonance region, and the output voltage of the converter is increased.

[0103] Method 2 is suitable for adjustment near the resonance point, and wide voltage range adjustment can be used in combination with scheme 1. It is worth noting that the adjustable inductance of the digital power inductor in the CLLC resonant converter of the present invention is not unique. That is, multiple magnetic columns can be included in the inductor to form a control port, which can achieve a wider range of inductance adjustment.

[0104] In the embodiment of method 2, Fig. 9The parallel connection of two CLLC resonant networks can reduce the output ripple of a single CLLC resonant converter and increase the upper limit of power capacity. However, there are certain parameter errors in the actual inductance and capacitance, and the power passing through each network is inevitably unbalanced.

[0105] In the embodiment of method 2, both networks use full-bridge topology, and both resonant inductors use digital power inductors. By adjusting the inductance of the resonant inductors of the two networks, the output voltage and current balance of the two networks can be achieved.

[0106] In the embodiment of method 2, the control circuit compares the output current of the two networks in real time, and changes the inductance of the resonant inductor and the operating frequency of the network switch according to the above two adjustment schemes to achieve current sharing control when multiple networks are connected in parallel. According to different operating requirements, the number of CLLC resonant converter networks and their connection methods, as well as the number and parameters of the magnetic columns of the control port of the resonant digital power inductor may be different, but still within the scope of the present invention. In addition, the circuit using the resonant digital power inductor and its working method involved in the present invention for non-CLLC resonant converter topology structure also falls within the scope of the present invention.

[0107] The present invention has the following advantages:

[0108] 1. The present invention adopts digital power inductor, so the voltage gain curve of the converter is not single, and the gain range can be changed by changing the inductance value, thereby overcoming the limitations of the resonant cavity design of the existing CLLC converter.

[0109] 2. This patent can adjust the inductance of the digital power inductor under different output voltage requirements. By adding multiple magnetic columns to the inductor to form a control port, a wider range of inductance adjustment can be achieved, the resonant cavity loss can be reduced, and the CLLC resonant converter can maintain a higher conversion efficiency under the full load range.

[0110] 3. Since the magnetic core of the digital power inductor only works in the on and off states, and not in the saturation state, it overcomes the problem of excessive loss in traditional saturated inductors.

[0111] 4. In the digital power inductor control process adopted by the present invention, no additional external power supply and sampling circuit are required.

[0112] 5. In addition to being applicable to CLLC resonant converters, this patent is also applicable to combination topologies of other resonant converters.

[0113] The above are preferred embodiments of the present invention. Any changes made according to the technical solution of the present invention, as long as the resulting functions do not exceed the scope of the technical solution of the present invention, belong to the protection scope of the present invention.

Claims

1. A resonant converter based on a digital power inductor, characterized in that: It includes a rectifier inverter module and a resonant cavity module; the rectifier inverter module and the resonant cavity module are connected, wherein: The rectifier and inverter module can realize the converter power input terminal V in and output terminal V o The bidirectional rectification and inversion function; The resonant cavity module adopts a digital power inductor with adjustable inductance, which can increase or decrease the resonant frequency of the converter circuit and realize the voltage regulation function of controlling the increase and decrease of the output voltage. When working, the digital power inductor is in an unsaturated magnetic circuit state.

2. A resonant converter based on a digital power inductor according to claim 1, characterized in that: The rectifier inverter module includes a first primary full-bridge loop switch tube S1, a second primary full-bridge loop switch tube S2, a third primary full-bridge loop switch tube S3, a fourth primary full-bridge loop switch tube S4, a first secondary full-bridge loop switch tube S5, a second secondary full-bridge loop switch tube S6, a third secondary full-bridge loop switch tube S7, a fourth secondary full-bridge loop switch tube S8, and a filter capacitor C in and C o ; The resonant cavity module includes the primary resonant inductor L rp , primary resonant capacitor C rp , secondary side resonant inductor L rs , secondary side resonant capacitor C rs , high frequency transformer T, where the primary resonant inductor L rp and the secondary resonant inductor L rs Both are digital power inductors.

3. A resonant converter based on a digital power inductor according to claim 2, characterized in that: The rectifier inverter module includes: Power supply V in One end of the input end is connected to the drain of the first primary full-bridge loop switch tube S1 and the third primary full-bridge loop switch tube S3, and the other end is connected to the source of the second primary full-bridge loop switch tube S2 and the fourth primary full-bridge loop switch tube S4. The source of the first primary full-bridge loop switch tube S1 is connected to the drain of the second primary full-bridge loop switch tube S2 as the primary full-bridge output end a, the source of the third primary full-bridge loop switch tube S3 is connected to the drain of the fourth primary full-bridge loop switch tube S4 as the primary full-bridge output end b, and the first The drain of the second secondary full-bridge loop switch tube S6 of the secondary full-bridge loop switch tube S5 is connected to the secondary full-bridge input terminal c, and the source of the third secondary full-bridge loop switch tube S7 and the drain of the fourth secondary full-bridge loop switch tube S8 are connected to the secondary full-bridge input terminal d; the drains of the first secondary full-bridge loop switch tube S5 and the third secondary full-bridge loop switch tube S7 are connected to the positive electrode of the load, and the sources of the second secondary full-bridge loop switch tube S6 and the fourth secondary full-bridge loop switch tube S8 are connected to the negative electrode of the load.

4. The resonant converter based on a digital power inductor according to claim 2, characterized in that: The resonant cavity module includes: The primary digital power inductor L in the resonant cavity rp One end is connected to the inverter bridge output terminal a, and the other end is connected to the same end of the primary winding of the high-frequency transformer T. The primary resonant capacitor C rp One end is connected to the inverter bridge output terminal b, and the other end is connected to the non-same-name end of the primary winding of the high-frequency transformer T; the secondary digital power inductor L in the resonant cavity rs One end is connected to the input terminal c of the rectifier bridge, and the other end is connected to the same end of the secondary winding of the high-frequency transformer T. The secondary resonant capacitor C rs One end is connected to the input terminal d of the rectifier bridge, and the other end is connected to the non-same-name end of the secondary winding of the high-frequency transformer T; Among them, the resonant frequency of the resonant inductor and the resonant capacitor in the resonant cavity is the resonant frequency of the converter circuit; Among them, the resonant cavity adopts a symmetrical structure, and the relationship between the primary inductor and the secondary inductor is L rp =n 2 L rs , the relationship between the primary capacitance and the secondary capacitance is C rp =C rs / n 2 ; Among them, n is the transformation ratio of the primary side to the secondary side of the high-frequency transformer T, n = the number of turns of the primary coil of the transformer / the number of turns of the secondary coil of the transformer.

5. The resonant converter based on digital power inductor according to claim 3, characterized in that: The rectifier inverter module has a forward working mode, and its working mode characteristics include: When working in the forward direction, the primary full bridge works in the inverter mode, and the secondary full bridge works in the rectification mode; the driving signals of the first primary full bridge loop switch tube S1 and the fourth primary full bridge loop switch tube S4 are the same, the driving signals of the second primary full bridge loop switch tube S2 and the third primary full bridge loop switch tube S3 are the same, the driving signals of the first primary full bridge loop switch tube S1 and the second primary full bridge loop switch tube S2 are complementary, and the driving signals of the third primary full bridge loop switch tube S3 and the fourth primary full bridge loop switch tube S4 are complementary; the first secondary full bridge loop switch tube S5, the second secondary full bridge loop switch tube S6, the third secondary full bridge loop switch tube S7, and the fourth secondary full bridge loop switch tube S8 of the switch tube are synchronously driven according to the secondary current direction, with i s The direction of the arrow is positive. In the forward direction, the first secondary full-bridge loop switch tube S5 and the fourth secondary full-bridge loop switch tube S8 are turned on, and the second secondary full-bridge loop switch tube S6 and the third secondary full-bridge loop switch tube S7 are turned off. In the reverse direction, the second secondary full-bridge loop switch tube S6 and the third secondary full-bridge loop switch tube S7 are turned on, and the first secondary full-bridge loop switch tube S5 and the fourth secondary full-bridge loop switch tube S8 are turned off.

6. The resonant converter based on digital power inductor according to claim 3, characterized in that: The rectifier inverter module also has a reverse working mode, and its working mode features include: When working in reverse, the primary full bridge works in rectification mode, and the secondary full bridge works in inverter mode; the driving signals of the first secondary full bridge loop switch tube S5 and the fourth secondary full bridge loop switch tube S8 are the same, the driving signals of the second secondary full bridge loop switch tube S6 and the third secondary full bridge loop switch tube S7 are the same, the driving signals of the first secondary full bridge loop switch tube S5 and the second secondary full bridge loop switch tube S6 are complementary, and the driving signals of the third secondary full bridge loop switch tube S7 and the fourth secondary full bridge loop switch tube S8 are complementary; the first primary full bridge loop switch tube S1, the second primary full bridge loop switch tube S2, the third primary full bridge loop switch tube S3, and the fourth primary full bridge loop switch tube S4 of the switch tube are synchronously driven according to the primary current direction, with i p The direction of the arrow is negative. In the positive direction, the first primary full-bridge loop switch tube S1 and the fourth primary full-bridge loop switch tube S4 are turned on, and the second primary full-bridge loop switch tube S2 and the third primary full-bridge loop switch tube S3 are turned off. In the reverse direction, the second primary full-bridge loop switch tube S2 and the third primary full-bridge loop switch tube S3 are turned on, and the first primary full-bridge loop switch tube S1 and the fourth primary full-bridge loop switch tube S4 are turned off.

7. The resonant converter based on digital power inductor according to claim 4, characterized in that: The resonant cavity includes the primary resonant inductor L rp , primary resonant capacitor C rp , secondary side resonant inductor L rs , secondary side resonant capacitor C rs , high frequency transformer T, where the primary resonant inductor L rp and the secondary resonant inductor L rs All of them are digital power inductors; the characteristics of digital power inductors are as follows: The internal structure of the digital power inductor includes a built-in control port and a magnetic column with an adjustable equivalent cross-sectional area; the inductance of the port is controlled by the control port, and the magnetic column controls the signal terminal S of the switch. ctrl Used to drive the signal MOSFET to control the winding L ctrl When the control winding is short-circuited, the magnetic block corresponding to the inductor is disconnected; therefore, through different magnetic column equivalent cross-sectional areas A e The design can realize the increase or decrease of the inductance of the digital power inductor; at the same time, because the magnetic core column only works in the on and off states, the digital power inductor works in an unsaturated state; Among them, the control port of the digital power inductor can be controlled by an external information signal via a driving circuit, without the need for an additional external power supply and sampling circuit.

8. The resonant converter based on digital power inductor according to claim 4, characterized in that: The resonant cavity includes the primary resonant inductor L rp , primary resonant capacitor C rp , secondary side resonant inductor L rs , secondary side resonant capacitor C rs , high frequency transformer T, where the characteristics of the resonant frequency are as follows: The resonant frequency of the resonant inductor and the resonant capacitor in the resonant cavity is the resonant frequency of the converter. According to the characteristics of the electronic devices in the resonant cavity, the resonant frequency of the converter is obtained by the fundamental wave analysis method: where f r is the resonant frequency, L r is the equivalent inductance of the resonant cavity, C r is the equivalent capacitance of the resonant cavity; According to the characteristics of the electronic devices of the resonant cavity, the equivalent circuit of the resonant cavity is obtained through the principle of conservation of electromagnetic energy between the primary and secondary sides; where L P is the primary equivalent resonant inductance, L s is the secondary side equivalent resonant inductance, L m is the equivalent magnetizing inductance, C P is the primary equivalent capacitance, C s is the secondary side equivalent capacitance, U1 is the primary side equivalent circuit input voltage, and U2 is the secondary side equivalent circuit output voltage; The current inflow is positive, L P The positive terminal of is connected to the positive terminal of U1, L P The negative terminal and L s The positive terminal and L m The positive terminals of the three are connected at one point, L m The negative terminal of C P One end and C s The three ends are connected at one point, L s The negative terminal of C is connected to the positive terminal of U2. P The other end is connected to the negative terminal of U1, C s One end of is connected to the negative terminal of U2; When the converter operates at the resonant frequency, the resonant cavity current is a sine wave, the resonant cavity equivalent complex impedance is zero, and the reactive loss is minimal; Further, the voltage gain expression of the CLLC converter is obtained by the fundamental wave analysis method: Among them, M is the resonant cavity voltage gain, U1 is the primary equivalent circuit input voltage, U2 is the secondary equivalent circuit output voltage, X p is the primary equivalent reactance, X s is the secondary side equivalent reactance, X m is the equivalent excitation reactance, R eq is the output load equivalent resistance; Voltage gain expression M(f n ,Q,k), f n is the converter resonant frequency, and the inductance ratio k is L p Primary side equivalent inductance and L m Ratio of magnetizing inductance to characteristic impedance Quality factor Q = Z / R eq .

9. A working method of a resonant converter based on a digital power inductor, obtained by using the resonant converter described in any one of claims 1 to 8; characterized in that: The converter has three operating modes, including the following: The CLLC resonant converter has three operating modes: under-resonance, quasi-resonance and over-resonance. The operating frequency is divided by the resonant frequency. When the operating frequency is at the resonant frequency, it is the quasi-resonance mode; when the operating frequency is less than the resonant frequency, it is the under-resonance mode; when the operating frequency is greater than the resonant frequency, it is the over-resonance mode.

10. The working method of a resonant converter based on a digital power inductor according to claim 9, characterized in that: The converter has two control methods to achieve output voltage control. The control methods are as follows: When the converter works in the following method, the converter will adjust the inductance of the digital power inductor according to the output voltage required in real time, and finally adjust the external output voltage and frequency of the converter; wherein: 1) When the output voltage gain needs to be increased, increase the inductance of the primary resonant inductor and the secondary resonant inductor, and at the same time adjust the output voltage and the operating frequency; 2) When the output voltage gain needs to be reduced, the inductance of the primary resonant inductor and the secondary resonant inductor is reduced, and at the same time, the specific output voltage is adjusted and the operating frequency is adjusted; When the converter works under method 2, the converter will change the resonant frequency by changing the resonant inductance value, and output a voltage value of the working point that meets the rated resonant frequency; wherein: (1) When the output voltage is greater than the target voltage, the inductance of the primary resonant inductor and the secondary resonant inductor is increased, the resonant frequency of the resonant converter is reduced, the converter operates in the over-resonance region, and the output voltage of the converter is reduced; (2) When the output voltage is lower than the target voltage, the inductance of the primary resonant inductor and the secondary resonant inductor is reduced, the resonant frequency of the resonant converter is increased, the converter operates in the under-resonance region, and the output voltage of the converter is increased.

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