Self-resonance driving isolation low-stress bidirectional Class E2High frequency power converter

文档序号：1864360 发布日期：2021-11-19 浏览：7次中文

阅读说明：本技术 一种自谐振驱动隔离低应力型双向Class E2高频功率变换器 (Self-resonance driving isolation low-stress bidirectional Class E2High frequency power converter ) 是由胡西红黄春蓉秦东东于 2020-05-14 设计创作，主要内容包括：本发明涉及一种自谐振驱动隔离低应力型双向Class E～(2)高频功率变换器,属于开关电源技术领域,解决了现有变换器存在的开关管电压应力高、系统体积大且能量无法双向流动的问题。变换器包括：第一Class E谐振单元、隔离型匹配网络、第二Class E谐振单元；所述第一Class E谐振单元的第二端口与所述隔离型匹配网络的第一端口相连,所述隔离型匹配网络的第二端口与所述第二Class E谐振单元的第一端口相连；当所述变换器的能量正向流动时,所述第一Class E谐振单元的第一端口与电源相连,所述第二Class E谐振单元的第二端口与负载相连；当所述变换器的能量反向流动时,所述第一Class E谐振单元的第一端口与负载相连,所述第二Class E谐振单元的第二端口与电源相连。(The invention relates to a self-resonance drive isolation low-stress bidirectional Class E 2 A high-frequency power converter belongs to the technical field of switching power supplies and solves the problems that the existing converter has high voltage stress of a switching tube, a system is large in size and energy cannot flow bidirectionally. The converter includes: the device comprises a first Class E resonance unit, an isolated matching network and a second Class E resonance unit; the second port of the first Class E resonance unit is connected with the first port of the isolation type matching network, and the second port of the isolation type matching network is connected with the first port of the second Class E resonance unit; when the energy of the converter flows in the forward direction, a first port of the first Class E resonance unit is connected with a power supply, and a second port of the second Class E resonance unit is connected with a load; when the energy of the converter flows reversely, the first port of the first Class E resonance unit is connected with a load, and the second port of the second Class E resonance unit is connected with a power supply.)

1. Self-resonance driving isolation low-stress bidirectional Class E²A high frequency power converter, characterized in that the converter comprises: the device comprises a first Class E resonance unit, an isolated matching network and a second Class E resonance unit;

the second port of the first Class E resonance unit is connected with the first port of the isolation type matching network, and the second port of the isolation type matching network is connected with the first port of the second Class E resonance unit;

when the energy of the converter flows in the forward direction, a first port of the first Class E resonance unit is connected with a power supply, and a second port of the second Class E resonance unit is connected with a load;

when the energy of the converter flows reversely, the first port of the first Class E resonance unit is connected with a load, and the second port of the second Class E resonance unit is connected with a power supply.

2. The self-resonant driven isolated low stress type bidirectional Class E of claim 1²A high-frequency power converter, characterized in that,

the first Class E resonance unit includes: capacitor C₁Resonant capacitor C_FResonant inductance L_FInductor L_G1N-type switch tube S_FDC bias power supply V_b1；

Resonant inductor L_FOne end of (A) is connected with an electric connectionContainer C₁One terminal of (1), resonant inductor L_FThe other end of the N-shaped switch tube S is connected with the N-shaped switch tube S_FDrain electrode of (1), and resonant capacitor C_FOne end of (a);

the other end of the capacitor C1 is connected with a DC bias power supply V_b1Negative electrode of (1), N-type switch tube S_FSource electrode and resonant capacitor C_FThe other end of (a); DC bias power supply V_b1Positive electrode series inductance L_G1Back connected to N-type switch tube S_FA gate electrode of (1);

the resonance inductor L_FOne end of the first Class E resonant unit is used as a first positive port of the first Class E resonant unit and is used for connecting a power supply positive electrode or a load positive electrode;

the other end of the capacitor C1 is used as a first negative port of the first Class E resonance unit and is used for connecting a power supply negative electrode or a load negative electrode;

the resonant capacitor C_FOne end of the first Class E resonant unit is used as a second positive port of the first Class E resonant unit and is used for connecting a first positive port of the isolation type matching network;

resonant capacitor C_FThe other end of the first Class E resonant unit is used as a second negative port of the first Class E resonant unit and is used for being connected with a first negative port of the isolation type matching network.

3. The self-resonant driven isolated low stress type bidirectional Class E of claim 2²A high-frequency power converter, characterized in that,

the second Class E resonance unit comprises a resonance capacitor C_dCapacitor C₂Resonant inductance L_dInductor L_G2N-type switch tube S_dDC bias power supply V_b2；

Resonant capacitor C_dOne end of which is connected with a resonance inductor L_dOne end of (1), N-type switch tube S_dA drain electrode of (1); resonant inductor L_dThe other end of the capacitor C is connected with a capacitor C₂One end of (a);

resonant capacitor C_dThe other end of the DC bias power supply V is connected with a DC bias power supply V_b2Negative electrode of (1), N-type switch tube S_dSource electrode and capacitor C₂The other end of (a); DC bias power supply V_b2Positive electrode of (2)Via a series inductance L_G2Back connected to N-type switch tube S_dA gate electrode of (1);

the resonant capacitor C_dOne end of the first Class E resonant unit is used as a first positive port of the second Class E resonant unit and is used for connecting a second positive port of the isolation type matching network;

the resonant capacitor C_dThe other end of the first Class E resonant unit is used as a first negative port of the second Class E resonant unit and is used for being connected with a second negative port of the isolation type matching network;

the capacitor C₂One end of the first Class E resonant unit is used as a second positive port of the second Class E resonant unit and is used for a power supply positive electrode or a load positive electrode;

the capacitor C₂The other end of the second Class E resonant unit is used as a second positive port of the second Class E resonant unit and is used for connecting a negative electrode of a power supply or a negative electrode of a load.

4. The self-resonant driven isolated low stress type bidirectional Class E of claim 3²A high frequency power converter, wherein the isolated matching network comprises: capacitor C_BCapacitor C_recAnd a transformer T_r；

Capacitor C_BOne end of which is connected with a transformer T_rPositive input end of, a transformer T_rThe positive output end of the capacitor is connected with a capacitor C_recOne terminal of (C), a capacitor_BThe other end of the first positive port is used as a first positive port of the isolated matching network; transformer T_rThe negative input end of the capacitor C is used as a first negative port of the isolated matching network_recThe other end of the first and second terminals of the isolated matching network is used as a second positive port of the isolated matching network, and a transformer T_rAnd the negative output end of the first impedance matching network is used as a second negative port of the isolation type matching network.

5. The self-resonant driven isolated low stress type bidirectional Class E of claim 4²High-frequency power converter, characterized by a transformer T_rIncluding an ideal transformer T and a primary side leakage inductance L_rAnd an excitation inductor L_mAnd secondary leakage inductance L_rec(ii) a Primary side leakage inductance L_rOne end of the transformer is simultaneously connected with the same name end of the primary coil of the ideal transformer T and the exciting currentFeeling L_mOne end of (1), excitation inductance L_mThe other end of the transformer is connected with a primary coil synonym end of an ideal transformer T, and a secondary coil synonym end of the ideal transformer T is connected with a secondary side leakage inductance L_recPrimary side leakage inductance L_rThe other end of which is used as a transformer T_rPositive input terminal of (1), excitation inductance L_mThe other end of which is used as a transformer T_rNegative input terminal of (1), secondary side leakage inductance L_recThe other end of which is used as a transformer T_rThe secondary coil of the ideal transformer T is used as the transformer T_rTo the negative output terminal of (1).

6. The self-resonant driven isolated low stress type bidirectional Class E of claim 5²High frequency power converter, characterized in that L is determined according to the following formula_dAnd C_dThe parameter values of (2):

where ω is 2 pi f, T is 1/f, and f is the operating frequency of the converter; p_oIs the output power of the converter, V_oIs the output voltage of the converter; t is_on＝D_dT，T_off＝(1-D_d)T，D_dIs an N-type switching tube S in the second Class E resonance unit_dDuty cycle of (d); is I_inThe initial phase angle of (a).

7. The self-resonant driven isolated low stress type bidirectional Class E of claim 6²High frequency power converter, characterized in that L is determined according to the following formula_F、C_F、C_rec、L_rAnd the parameter value of the ideal turn ratio n of the ideal transformer is as follows:

wherein m is₁And m₂Respectively an N-type switch tube S in the first Class E resonance unit_FThe pole coefficients of the fundamental wave and the third harmonic of the voltage stress, and k is the coupling coefficient of the transformer; r_inv＝(1.5V_in)²/(2P_o)，V_inIs the input voltage of the converter; r_rec＝V_o ²/P_o，X_rec＝R_rec/2。

8. The self-resonant driven isolated low stress type bidirectional Class E of claim 7²High-frequency power converter, characterized in that the inductance L is determined according to the following formula_G1The inductance value of (2):

wherein s is the Lappas operator, C_GD1、C_GS1Respectively being the N-type switch tube S_FThe parasitic capacitance of Miller and the parasitic capacitance of gate source, R_G1Is the N-type switch tube S_FThe gate parasitic resistance of (1); v_{DS_SF}Is the N-type switch tube S_FThe drain-source voltage fundamental amplitude of (1); v_{GS_SF}Is the N-type switch tube S_FThe fundamental amplitude of the gate-source drive voltage.

9. The self-resonant driven isolated low stress type bidirectional Class E of claim 8²High frequency power converter, characterized in that L is determined according to the following formula_G2The value of (A) is as follows:

wherein, C_GD2、C_GS2Respectively being the N-type switch tube S_dThe parasitic capacitance of Miller and the parasitic capacitance of gate source, R_G2Is the N-type switch tube S_dThe gate parasitic resistance of (1); v_{DS_Sd}Is the N-type switch tube S_dThe drain-source voltage fundamental amplitude of (1); v_{GS_Sd}Is the N-type switch tube S_dThe fundamental amplitude of the gate-source drive voltage.

10. The self-resonant driven isolated low stress type bidirectional Class E of claim 9²A high-frequency power converter, characterized in that,

calculating L_G1When, V_{DS_SF}The value is 1.5 times of the forward input voltage;

calculating L_G2When, V_{DS_Sd}The value is 1.5 times of the forward output voltage.

Technical Field

The invention relates to the technical field of switching power supplies, in particular to a self-resonant driving isolation low-stress bidirectional Class E²A high frequency power converter.

Background

In the field of industrial electronics and consumer electronics, a large number of switching power supplies are required to have high stability, high efficiency, high power density, small size and light weight to ensure continuous safe and reliable operation of the system and to effectively reduce the size and weight thereof. Owing to the rapid development of third-generation wide bandgap semiconductor technologies represented by SiC and GaN, particularly, large-scale production and application of GaN switching devices, which are excellent in high-frequency characteristics, an effective method for increasing the operating frequency of a system is provided, and the switching power supply can be easily reduced in size and weight. When the working frequency of the system is increased to dozens of megahertz, the parameter values of passive elements in the system are greatly reduced, and the method has great significance for improving the integration level of the system and reducing the volume of the system.

However, as the switching frequency increases, the system will be in a full resonance state, which will cause the voltage and current stresses in the system to be too high, and this will adversely affect the safe and stable operation of the system and the improvement of the working efficiency. In order to reduce the voltage stress of the switching tube in the system, the LC resonant branches are usually connected in parallel at two ends of the switching tube, so as to adjust the voltage harmonic characteristics of the system, thereby achieving the goal of reducing the stress. However, this method of introducing an additional branch increases the volume of the system and prevents the efficiency of the system from being increased.

In order to improve the safety of system operation, the power converter is usually required to be electrically isolated, and for the problem, the existing design method at present adopts a high-frequency magnetic core wound transformer, but the leakage inductance of the transformer can influence the resonance working state of the system, and the use of the magnetic core transformer is not beneficial to the miniaturization and high efficiency of the system.

In addition, with the progress of technology, the bidirectional DC/DC power converter, as an interface for bidirectional flow of energy, shows great technical advantages and application potentials in the fields of photovoltaic power generation, micro-grid systems, electric vehicles, and the like. The circuit topology of the traditional bidirectional power converter mainly adopts non-isolated topologies such as Buck/Boost type, Buck-Boost type, Cuk type and Zata/SEPIC type, etc., and isolated topologies such as full bridge type and half bridge type, etc., and the switching tubes of the topologies usually adopt the working mode of hard switching, so that the device heating is high and the system efficiency is low.

In the technical field of high-frequency driving, a high-frequency crystal oscillator is generally adopted to generate independent square wave signals, and then the driving capability of the high-frequency square wave signals is improved through a post-stage circuit, so that the driving requirement of a switching tube is met. However, the square wave drive has large capacitive switching loss under a high-frequency condition, and for this problem, a resonant inductor is usually connected in series on the basis of the square wave drive, so as to form a resonant drive, and drive energy is transmitted and converted between a gate electrode parasitic capacitor and the resonant inductor of a switching tube, so as to reduce drive loss.

Disclosure of Invention

In view of the above analysis, the present invention aims to provide a self-resonant driving isolation low-stress bidirectional Class E²A high frequency power converter is provided to overcome the above-mentioned disadvantages of the prior art.

The purpose of the invention is mainly realized by the following technical scheme:

self-resonance driving isolation low-stress bidirectional Class E²A high frequency power converter, the converter comprising: the device comprises a first Class E resonance unit, an isolated matching network and a second Class E resonance unit;

On the basis of the scheme, the following improvements are made:

further, the first Class E resonance unit includes: capacitor C₁Resonant capacitor C_FResonant inductance L_FInductor L_G1N-type switch tube S_FDC bias power supply V_b1；

Resonant inductor L_FOne end of which is connected with a capacitor C₁One terminal of (1), resonant inductor L_FThe other end of the N-shaped switch tube S is connected with the N-shaped switch tube S_FDrain electrode of (1), and resonant capacitor C_FOne end of (a);

the other end of the capacitor C1 is used as a first negative port of the first Class E resonance unit and is used for connecting a power supply negative electrode or a load negative electrode;

Further, the second Class E resonance unit comprises a resonance capacitor C_dCapacitor C₂Resonant inductance L_dInductor L_G2N-type switch tube S_dDC bias power supply V_b2；

resonant capacitor C_dThe other end of the DC bias power supply V is connected with a DC bias power supply V_b2Negative electrode of (1), N-type switch tube S_dSource electrode and capacitor C₂The other end of (a); DC bias power supply V_b2Positive pole of the capacitor is connected with an inductor L in series_G2Back connected to N-type switch tube S_dA gate electrode of (1);

Further, the isolated matching network includes: capacitor C_BCapacitor C_recAnd a transformer T_r；

Further, a transformer T_rIncluding an ideal transformer T and a primary side leakage inductance L_rAnd an excitation inductor L_mAnd secondary leakage inductance L_rec(ii) a Primary side leakage inductance L_rOne end of the transformer is simultaneously connected with the homonymous end of the primary coil of the ideal transformer T and the excitation inductor L_mOne end of (1), excitation inductance L_mThe other end of the transformer is connected with a primary coil synonym end of an ideal transformer T, and a secondary coil synonym end of the ideal transformer T is connected with a secondary side leakage inductance L_recPrimary side leakage inductance L_rThe other end of which is used as a transformer T_rPositive input terminal of (1), excitation inductance L_mThe other end of which is used as a transformer T_rNegative input terminal of (1), secondary side leakage inductance L_recThe other end of which is used as a transformer T_rThe secondary coil of the ideal transformer T is used as the transformer T_rTo the negative output terminal of (1).

Further, L is determined according to the following formula_dAnd C_dThe parameter values of (2):

Further, L is determined according to the following formula_F、C_F、C_rec、L_rAnd the parameter value of the ideal turn ratio n of the ideal transformer is as follows:

further, L is determined according to the following formula_G1The value of (A) is as follows:

Further, L is determined according to the following formula_G2The value of (A) is as follows:

Further, calculate L_G1When, V_{DS_SF}The value is 1.5 times of the forward input voltage; calculating L_G2When, V_{GS_Sd}The value is 1.5 times of the forward output voltage.

The invention has the following beneficial effects:

the self-resonant driving isolation low-stress bidirectional Class E provided by the embodiment²The high-frequency power converter has the advantages of low voltage stress of a switching tube, small system volume and bidirectional energy flow. The high-frequency air-core transformer is adopted to provide electrical isolation, and the voltage stress of the switching tube is effectively reduced under the condition that an LC branch is not introduced. Meanwhile, a driving circuit of the switching tube and a power circuit of the system are integrated together, and a self-resonant driving mode is adopted, so that the volume of the system is reduced, and the working efficiency of the system is improved. In addition, the inversion and rectification links of the system adopt a symmetrical resonance type Class E structure, which is beneficial to realizing the bidirectional flow of system energy, and the switching tubes of the inversion and rectification links work in a zero voltage conduction (ZVS) mode no matter the system works in a forward flow mode or a reverse flow mode, so that the safety and the working efficiency of the system are improved.

In the invention, the technical schemes can be combined with each other to realize more preferable combination schemes. Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The drawings are only for purposes of illustrating particular embodiments and are not to be construed as limiting the invention, wherein like reference numerals are used to designate like parts throughout.

Fig. 1 is a schematic circuit diagram of a conventional Boost-type high-frequency power converter;

FIG. 2 is a schematic circuit diagram of a conventional high-frequency DC/DC system based on a winding transformer with a magnetic core;

FIG. 3 is a schematic diagram of a conventional dual full-bridge bidirectional DC/DC converter circuit;

FIG. 4 shows the self-resonant driving isolation low-stress bidirectional Class E of example 1²A high frequency power converter circuit schematic;

FIG. 5 is an equivalent impedance network of the switching impedances ZDS;

FIG. 6 is a schematic diagram of a self-resonant circuit;

FIG. 7 shows S in the forward flow mode_FAnd S_dA drain-source voltage waveform diagram of (a);

FIG. 8 shows S in reverse flow mode_FAnd S_dA drain-source voltage waveform diagram of (a).

Detailed Description

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate preferred embodiments of the invention and together with the description, serve to explain the principles of the invention and not to limit the scope of the invention.

A circuit topology of a Boost type high frequency power converter is shown in fig. 1. The high-frequency DC/DC topology has L connected in parallel at two ends of the switch tube S_2FAnd C_2FThrough L_F、C_F、L_2FAnd C_2FThe resonance of the switch tube can lead the drain-source impedance of the switch tube to present low resistance characteristic to the second harmonic wave and high resistance characteristic to the third harmonic wave, thereby eliminating the second harmonic wave at two ends of the switch tube, amplifying the third harmonic wave and greatly reducing the voltage stress of the switch tube. However, this topology does not achieve electrical isolation, and L_2FAnd C_2FThe introduction of (b) may reduce the efficiency and power density of the system.

Another prior art topology for high frequency DC/DC power converters is shown in fig. 2. The circuit also adopts a method of introducing an LC branch circuit to reduce the voltage stress of the switching tube S. In addition, in order to realize electrical isolation, the circuit adopts a magnetic core type winding transformer structure, but the transformer is in a winding type structure and has a larger magnetic core, so that the volume and the weight of the system are obviously increased, the original purpose of high frequency of the switching power supply is seriously deviated, and the miniaturization and the light weight of the switching power supply are adversely affected. Meanwhile, the loss of the magnetic core under the high-frequency condition is very large, and the leakage inductance of the transformer causes obstacles to the precise design of system parameters, which seriously damages the improvement of the system performance.

Existing double full-bridge type bidirectional DC/DC converterThe way is shown in fig. 3. The energy of the circuit can be from the high-voltage side V_HTo the low-pressure side V_LAnd can be from the low-voltage side V_LTo the high-pressure side V_HAnd bidirectional energy flow is realized. However, the converter uses more switching tubes, and the switching tubes are in a hard switching operation mode, so that the switching loss of the system is more. Meanwhile, in order to realize electrical isolation and voltage grade conversion, the system adopts a magnetic core type transformer, so that the power loss and the volume of the system are further increased.

Aiming at the defects of the existing circuit, the invention aims to provide an isolated Class E with lower voltage stress of a switching tube, smaller system volume and bidirectional energy flow²High frequency power converter topologies. See example 1 for details.

Example 1

The embodiment discloses a self-resonant drive isolation low-stress bidirectional Class E²A high frequency power converter, the circuit diagram of which is shown in fig. 4, said converter comprising: the device comprises a first Class E resonance unit, an isolated matching network and a second Class E resonance unit; the second port of the first Class E resonance unit is connected with the first port of the isolation type matching network, and the second port of the isolation type matching network is connected with the first port of the second Class E resonance unit; when the energy of the converter flows in the forward direction, a first port of the first Class E resonance unit is connected with a power supply, and a second port of the second Class E resonance unit is connected with a load; when the energy of the converter flows reversely, the first port of the first Class E resonance unit is connected with a load, and the second port of the second Class E resonance unit is connected with a power supply.

Preferably, the first Class E resonance unit includes: capacitor C₁Resonant capacitor C_FResonant inductance L_FInductor L_G1N-type switch tube S_FDC bias power supply V_b1(ii) a Wherein, the resonant inductor L_FOne end of which is connected with a capacitor C₁One terminal of (1), resonant inductor L_FThe other end of the N-shaped switch tube S is connected with the N-shaped switch tube S_FDrain electrode of (1), and resonant capacitor C_FOne end of (a); the other end of the capacitor C1 is connected with a DC bias power supply V_b1Negative electrode of (1), N-type switch tube S_FSource electrode and resonant capacitor C_FThe other end of (a); DC bias power supply V_b1Positive electrode series inductance L_G1Back connected to N-type switch tube S_FA gate electrode of (1); the resonance inductor L_FOne end of the first Class E resonant unit is used as a first positive port of the first Class E resonant unit and is used for connecting a power supply positive electrode or a load positive electrode; the other end of the capacitor C1 is used as a first negative port of the first Class E resonance unit and is used for being connected with a power supply negative electrode or a load negative electrode. The resonant capacitor C_FOne end of the first Class E resonant unit is used as a second positive port of the first Class E resonant unit and is used for connecting a first positive port of the isolation type matching network; resonant capacitor C_FThe other end of the first Class E resonant unit is used as a second negative port of the first Class E resonant unit and is used for being connected with a first negative port of the isolation type matching network. In the first Class E resonant unit, a dc bias power supply V_b1For driving N-type switching tube S_FThe grid electrode works according to an N-type switch tube S_FThe turn-on voltage of the grid electrode is selected to be V corresponding to the turn-on voltage_b1The voltage value of (2).

Preferably, the second Class E resonance unit comprises a resonance capacitor C_dCapacitor C₂Resonant inductance L_dInductor L_G2N-type switch tube S_dDC bias power supply V_b2(ii) a Resonant capacitor C_dOne end of which is connected with a resonance inductor L_dOne end of (1), N-type switch tube S_dA drain electrode of (1); resonant inductor L_dThe other end of the capacitor C is connected with a capacitor C₂One end of (a); resonant capacitor C_dThe other end of the DC bias power supply V is connected with a DC bias power supply V_b2Negative electrode of (1), N-type switch tube S_dSource electrode and capacitor C₂The other end of (a); DC bias power supply V_b2Positive pole of the capacitor is connected with an inductor L in series_G2Back connected to N-type switch tube S_dA gate electrode of (1); the resonant capacitor C_dOne end of the first Class E resonant unit is used as a first positive port of the second Class E resonant unit and is used for connecting a second positive port of the isolation type matching network; the resonant capacitor C_dThe other end of the first Class E resonance unit is used as the second Class of the second Class E resonance unitThe negative port is used for connecting a second negative port of the isolation type matching network; the capacitor C₂One end of the first Class E resonant unit is used as a second positive port of the second Class E resonant unit and is used for a power supply positive electrode or a load positive electrode; the capacitor C₂The other end of the second Class E resonant unit is used as a second positive port of the second Class E resonant unit and is used for connecting a negative electrode of a power supply or a negative electrode of a load. In the second Class E resonant unit, a dc bias power supply V_b2For driving N-type switching tube S_dThe grid electrode works according to an N-type switch tube S_dThe turn-on voltage of the grid electrode is selected to be V corresponding to the turn-on voltage_b2The voltage value of (2).

Preferably, the isolated matching network includes: capacitor C_BCapacitor C_recAnd a transformer T_r(ii) a Capacitor C_BOne end of which is connected with a transformer T_rPositive input end of, a transformer T_rThe positive output end of the capacitor is connected with a capacitor C_recOne terminal of (C), a capacitor_BThe other end of the first positive port is used as a first positive port of the isolated matching network; transformer T_rThe negative input end of the capacitor C is used as a first negative port of the isolated matching network_recThe other end of the first and second terminals of the isolated matching network is used as a second positive port of the isolated matching network, and a transformer T_rAnd the negative output end of the first impedance matching network is used as a second negative port of the isolation type matching network.

Preferably, a transformer T_rIncluding an ideal transformer T and a primary side leakage inductance L_rAnd an excitation inductor L_mAnd secondary leakage inductance L_rec(ii) a Primary side leakage inductance L_rOne end of the transformer is simultaneously connected with the homonymous end of the primary coil of the ideal transformer T and the excitation inductor L_mOne end of (1), excitation inductance L_mThe other end of the transformer is connected with a primary coil synonym end of an ideal transformer T, and a secondary coil synonym end of the ideal transformer T is connected with a secondary side leakage inductance L_recPrimary side leakage inductance L_rThe other end of which is used as a transformer T_rPositive input terminal of (1), excitation inductance L_mThe other end of which is used as a transformer T_rNegative input terminal of (1), secondary side leakage inductance L_recThe other end of which is used as a transformer T_rThe secondary coil of the ideal transformer T is used as the transformer T_rTo the negative output terminal of (1).

Lower-face self-resonant drive isolation low-stress bidirectional Class E²The operation of the high frequency power converter is explained as follows:

(1) when the energy of the converter flows in the forward direction, a first port of the first Class E resonance unit is connected with a power supply, and a second port of the second Class E resonance unit is connected with a load; the working process of the converter at this time is as follows:

switching tube S in first Class E resonance unit_FIn the high-frequency switching state_FAnd C_FResonance occurs, the direct current voltage of the first port of the unit is inverted into high-frequency alternating current, and meanwhile LF, CF and the leakage inductance L of the transformer_rTransformer excitation inductance L_mAnd C_recResonates, will S_FAnd passing the voltage through a transformer T_rIs transmitted to the first port of the second Class E resonance unit and then passes through the switch tube S_dHigh frequency on-off and L_dAnd C_dThe second Class E resonant unit rectifies the dc voltage to a second port of the second Class E resonant unit.

(2) When the energy of the converter flows reversely, the first port of the first Class E resonance unit is connected with a load, and the second port of the second Class E resonance unit is connected with a power supply. The working process of the converter at this time is as follows:

switching tube S in second Class E resonance unit_dIn the high-frequency switching state_dAnd C_dThe resonance occurs, the DC voltage at the second port of the unit is inverted into high-frequency AC current, and the high-frequency AC current is output from the first port of the unit and then passes through the transformer T_rTransmitted to the second port of the first Class E resonance unit and finally passes through a switch tube S_FHigh frequency on-off and L_FAnd C_FThe first Class E resonant unit rectifies the dc voltage to a first port of the first Class E resonant unit.

By analyzing the working process of the converter, when the energy of the converter flows in the forward direction, the first Class E resonance unit is used as an inverter, and the second Class E resonance unit is used as a rectifier; when the energy of the converter flows reversely, the functions of the two are opposite.

Meanwhile, because the working frequency of the system and the load resistance are kept unchanged when the energy flows in the forward direction and the reverse direction, the conversion ratio of the system between the fundamental wave and each harmonic impedance is kept unchanged from the input end to the output end no matter which direction the energy flows in the resonance state, and therefore, the converter realizes the voltage reduction process no matter the energy flows in the forward direction or the reverse direction.

In addition, since the circuit configuration of the converter and the circuit functions of the respective units are symmetrical to each other in the state where the energy flows in the forward direction and the reverse direction, designing the circuit from any one flow direction can satisfy not only the design specification of the flow direction but also the circuit specification in the state opposite to the flow direction, and therefore, the energy flow direction in the converter does not affect the design of the system parameters, and therefore, the present embodiment selects the operating state in the case where the energy flows in the forward direction for parameter design.

It will be appreciated that the design of the parameter values for each element in the converter is dependent on the design criteria of the converter. For example, the design index in the present embodiment may be as shown in table 1.

TABLE 1 design criteria of the converter

Flow of energy to	Frequency of operation	Input voltage	Output voltage	System power	Load resistance
						Forward direction	20MHz	48V	24V	120W	4.8Ω
Reverse direction	20MHz	24V	12V	30W	4.8Ω

The following describes the parameter design process with the forward flow of energy of the transformer as an example:

a. the parameters of the Class E rectifier (second Class E resonant unit) of the latter stage are designed as follows:

first assume C_dTwo ends of the alternating current source are connected in parallel, the frequency of the alternating current source is consistent with the switching frequency of the system, and the amplitude value is I_inFor outputting currentMultiple, and S_dDuty ratio D of_d0.5, then the equation set (1) can be obtained according to the principle of the correlation circuit, and then the correlation index in table 1 is substituted into (1), i.e. L can be calculated_dAnd C_dThe parameter (c) of (c).

Where ω is 2 pi f, T is 1/f, and f is the operating frequency of the converter; p_oIs the output power of the converter, V_oIs the output voltage of the converter; t is_on＝D_dT，T_off＝(1-D_d)T，D_dIs an N-type switching tube S in the second Class E resonance unit_dDuty cycle of (d); is I_inAs an intermediate variable, the initial phase angle of (a) can be determined by equation (1).

b. The parameters of the front-stage Class E inverter (first Class E resonance unit) and the isolation type matching network are designed as follows:

because the input voltage is high, it is necessary to reduce the switching tube S by introducing higher harmonic voltage through network resonance_FVoltage stress of (d). In actual operation, L_F、C_FAnd L_r、L_rec、L_mThe resonant circuit and the resonant circuit jointly participate in resonance, and the voltage harmonic characteristics of the switching tube are adjusted, so that the voltage stress of the switching tube can be effectively reduced without introducing an extra LC branch circuit. The use of the air-core transformer can improve the electrical safety of the system, and the loss and the volume are lower, thereby being beneficial to improving the efficiency and the integration level of the system.

After high harmonics above the third harmonic in the system are ignored, the switch tube S_FThe expression of the drain-source voltage (v) is shown in (2):

wherein, V_DS1、V_DS2、V_DS3Respectively the fundamental wave amplitude, the second harmonic amplitude and the third harmonic amplitude of the drain-source voltage,the phase angle of the fundamental wave, the phase angle of the second harmonic wave and the phase angle of the third harmonic wave of the drain-source voltage are respectively. Derived mathematically, in order to make v_DSMinimum and thus maximum reduction of voltage stress, v, of the switching tube_DSShould satisfy: the fundamental wave amplitude is 6 times of the third harmonic amplitude, the second harmonic amplitude is zero, and the third harmonic phase angle is 3 times of the fundamental wave phase angle, and the frequency characteristics that the corresponding switch impedance needs to satisfy are as follows:

in this side Z_DS1、Z_DS2、Z_DS3The fundamental impedance, the second harmonic impedance and the third harmonic impedance of the switch impedance, respectively.Andthe fundamental phase angle and the third harmonic phase angle of the switch impedance, respectively.

The equivalent model of the system switch impedance is shown in FIG. 5, and the expression is shown in (4)

Wherein Zrec ═ Rrec + jXrec,xrec is Rrec/2. And (3) adopting a pole-zero configuration method to enable the switch impedance to meet the condition of the expression (2), thereby reducing the voltage stress of the switch tube and realizing the solution of the relevant parameters in the figure 5. First configuration Z_DSIs 2 omega, thereby ensuring v_DSIs zero. Then configuration Z_DSPole m₁ω and m₂ω, by pair of m₁And m₂To ensure that the fundamental amplitude is 6 times the third harmonic amplitude and the third harmonic phase angle is 3 times the fundamental phase angle, the scan results in m₁＝1.0367，m₂3.0945. At this time, m is₁And m₂The value of (3) is substituted into an expression (5) and a transformer expression (6) which are obtained by combining the expression (3) and the expression (4), and then the parameter values of the inversion link and the matching link can be calculated.

Wherein m is₁And m₂Respectively an N-type switch tube S in the first Class E resonance unit_FThe pole coefficients of the fundamental wave and the third harmonic of the voltage stress, and k is the coupling coefficient of the transformer; the value satisfiesAnd (4) finishing. R_inv＝(1.5V_in)²/(2P_o)，V_inIs the input voltage of the converter; r_rec＝V_o ²/P_o，X_rec＝R_rec/2。

c. Design of self-resonant drive parameters

The self-resonance driving working mode is adopted to drive the switching tubes in the front and rear two-stage Class E resonance links, the driving mode has the advantages that the system integration level and the working efficiency can be increased, and meanwhile, the self-resonance driving mode can automatically realize the correspondence of the phase relation of the driving signals of the front and rear two-stage switching tubes. The self-resonant circuit is shown in FIG. 6, and its operation principle is that a resonant inductor L is connected in series with the gate of the switching tube_GThrough L_GAnd a parasitic parameter C inside the switch tube_GD、C_GS、R_GWill switch the drain-source voltage v of the transistor_DSResonating to the gate-source of the switching tube to produce a fundamental component of the drive voltage, which is related to the DC bias voltage V_bThe superposition constitutes the driving voltage of the switching tube.

According to the relevant circuit principle, the relation between the grid voltage and the drain-source voltage of the switch tube can be obtained through mathematical derivation, and the relations are shown in formulas (7) and (8).

Specifically, L is determined according to the following formula_G1The value of (A) is as follows:

L is also determined according to the following formula_G2The value of (A) is as follows:

wherein s is the Lappas operator, C_GD2、C_GS2Respectively being the N-type switch tube S_dThe parasitic capacitance of Miller and the parasitic capacitance of gate source, R_G2Is the N-type switch tube S_dThe gate parasitic resistance of (1); v_{DS_Sd}Is the N-type switch tube S_dThe drain-source voltage fundamental amplitude of (1); v_{GS_Sd}Is the N-type switch tube S_dThe fundamental amplitude of the gate-source drive voltage.

Since the parasitic parameters in the switch tube are known, the self-resonance parameters L of the front and the rear two stages can be solved by only selecting proper driving voltage fundamental wave amplitude and then substituting expressions (7) and (8)_G1And L_G2And finishing the design of the driving link. V_{GS_SF}、V_{GS_Sd}Usually, about 5V is selected; calculating L_G1When, V_{DS_SF}The value is 1.5 times of the forward input voltage; calculating L_G2When the temperature of the water is higher than the set temperature,V_{DS_Sd}the value is 1.5 times of the forward output voltage.

According to the method, the parameter design of the circuit topology is completed, and simulation verification is performed in the circuit simulation software PSpice, and the simulation result is shown in FIG. 7 and FIG. 8.

It can be seen from the figure that the switch tube S is switched whether the system energy flows in the positive direction or the negative direction_FAnd S_dZero voltage conduction is realized, so that the working efficiency is effectively improved. And the system is in forward flow, S_FThe voltage stress of the transformer is about 125V, which is about 2.6 times of the forward input voltage, the voltage stress is lower, and the working safety of the system is ensured.

The self-resonant driving isolation low-stress bidirectional Class E provided by the embodiment²The high-frequency power converter has the advantages of low voltage stress of a switching tube, small system volume and bidirectional energy flow. The high-frequency air-core transformer is adopted to provide electrical isolation, and the voltage stress of the switching tube is effectively reduced under the condition that an LC branch is not introduced. Meanwhile, a driving circuit of the switching tube and a power circuit of the system are integrated together, and a self-resonant driving mode is adopted, so that the volume of the system is reduced, and the working efficiency of the system is improved. In addition, the inversion and rectification links of the system adopt a symmetrical resonance type Class E structure, which is beneficial to realizing the bidirectional flow of system energy, and the switching tubes of the inversion and rectification links work in a zero voltage conduction (ZVS) mode no matter the system works in a forward flow mode or a reverse flow mode, so that the safety and the working efficiency of the system are improved.

The converter may be used to charge a battery and then transfer power from the battery to a load when not being charged. For example, in a photovoltaic street light system, the battery is charged by the photovoltaic panel during the day, while power is supplied to the LED street light at night. With the development of the technology, the power converter can be integrated inside a chip in the future, and the system can have two different transmission ratios by adjusting the relevant parameters, so that the production cost of the converter is reduced.

Those skilled in the art will appreciate that all or part of the flow of the method implementing the above embodiments may be implemented by a computer program, which is stored in a computer readable storage medium, to instruct related hardware. The computer readable storage medium is a magnetic disk, an optical disk, a read-only memory or a random access memory.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention.

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