CN103546038B

CN103546038B - A kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation

Info

Publication number: CN103546038B
Application number: CN201210247494.4A
Authority: CN
Inventors: 陈仲; 史良辰
Original assignee: Nanjing University of Aeronautics and Astronautics
Current assignee: Nanjing University of Aeronautics and Astronautics
Priority date: 2012-07-18
Filing date: 2012-07-18
Publication date: 2016-07-27
Anticipated expiration: 2032-07-18
Also published as: CN103546038A

Abstract

The invention discloses a soft-switching full-bridge DC converter capable of suppressing voltage oscillation on the secondary side, which includes a DC power supply V _in , a first inverter bridge arm and a second inverter bridge arm, an auxiliary inductor, an auxiliary transformer, an auxiliary capacitor, an isolation Transformer and rectifier filter circuit. The present invention adopts the phase-shifting control method. Since the auxiliary network composed of auxiliary inductance, auxiliary transformer and auxiliary capacitor is added, the primary side current of the converter is reversed in advance under the action of the voltage source provided by the auxiliary transformer, and the secondary rectified output voltage oscillates. It is well suppressed, and the zero-voltage switching of the primary switch tube is realized in a wide load range, there is no loss of the duty cycle of the secondary side, the ripple of the filter inductor current is small, and the output noise is reduced.

Description

A Soft Switching Full-Bridge DC Converter with Suppressed Secondary Voltage Oscillation

技术领域 technical field

本发明涉及一种抑制副边电压振荡的软开关全桥直流变换器。The invention relates to a soft-switching full-bridge DC converter capable of suppressing secondary side voltage oscillation.

背景技术 Background technique

移相控制软开关全桥变换器由于综合了PWM开关和谐振型开关的优点，在开关过程中，利用谐振技术实现零电压/零电流开关，开关过程结束后又回到普通的PWM状态，它同时具备了开关损耗小，通态损耗低及PWM调压等优点，因此在中大功率的直流变换场合受到广泛的青睐。The phase-shift control soft-switching full-bridge converter integrates the advantages of the PWM switch and the resonant switch. During the switching process, the resonant technology is used to realize zero-voltage/zero-current switching. After the switching process, it returns to the normal PWM state. At the same time, it has the advantages of low switching loss, low on-state loss and PWM voltage regulation, so it is widely favored in medium and high-power DC conversion occasions.

而传统的移相控制零电压开关全桥变换器因副边整流二极管存在反向恢复问题，原边漏感与整流二极管寄生电容的谐振使得副边整流输出电压存在严重的尖峰电压及振荡，因而显著提高了整流管的电压应力及输出电压噪声。为了解决上述问题，国内外学者做了大量研究工作。副边采用RCD吸收电路，如附图1所示，其抑制尖峰电压和振荡的效果较好，但吸收电路功率耗散问题严重，降低了变换器的整机效率。副边采用有源或无损耗无源箝位的方式抑制副边电压振荡，抑制效果明显，并很好地解决了功率耗散问题，但此类方法均需要较大的箝位电容，易引起一次侧的电流尖峰，另外有源箝位的方式需要引入额外的开关，这就需增加额外的控制电路及驱动电路，增加了系统的成本及复杂度。原边串饱和电感的方法可以明显增加滞后臂的软开关范围，占空比丢失小，且原边换流结束后主功率传输路径的等效串联电感值小可有效地抑制副边的电压尖峰和振荡，但是饱和电感工作于双象限，其磁芯体积大，发热严重，不利于变换器的集成。RichardRedl等人在原边加入两个箝位二极管和一个较大的谐振电感，如附图2所示，拓宽了软开关范围，并大大抑制了整流二极管的电压尖峰和振荡，但较大的谐振电感的加入导致的占空比丢失严重，且并不能消除变压器漏感引起的电压振荡，而箝位二极管的工作条件往往较差，降低了变换器工作可靠性及其效率。However, in the traditional phase-shift control zero-voltage switching full-bridge converter, due to the reverse recovery problem of the rectifier diode on the secondary side, the resonance of the leakage inductance of the primary side and the parasitic capacitance of the rectifier diode causes serious peak voltage and oscillation in the rectified output voltage of the secondary side. Significantly improves the voltage stress and output voltage noise of the rectifier. In order to solve the above problems, domestic and foreign scholars have done a lot of research work. The secondary side uses an RCD snubber circuit, as shown in Figure 1, which has a good effect in suppressing peak voltage and oscillation, but the problem of power dissipation in the snubber circuit is serious, which reduces the overall efficiency of the converter. The secondary side adopts active or lossless passive clamping method to suppress the voltage oscillation of the secondary side, the suppression effect is obvious, and the power dissipation problem is well solved, but these methods require a large clamping capacitor, which is easy to cause The current peak on the primary side, and the active clamping method needs to introduce additional switches, which requires additional control circuits and drive circuits, which increases the cost and complexity of the system. The method of primary side series saturated inductance can significantly increase the soft switching range of the lagging arm, the duty cycle loss is small, and the equivalent series inductance value of the main power transmission path after the primary side commutation is small can effectively suppress the voltage spike of the secondary side And oscillation, but the saturated inductance works in two quadrants, its magnetic core is bulky and generates serious heat, which is not conducive to the integration of the converter. Richard Redl et al. added two clamping diodes and a larger resonant inductance to the primary side, as shown in Figure 2, which widened the soft switching range and greatly suppressed the voltage spike and oscillation of the rectifier diode, but the larger resonant inductance The duty cycle loss caused by the addition of the transformer is serious, and the voltage oscillation caused by the leakage inductance of the transformer cannot be eliminated, and the working conditions of the clamping diode are often poor, which reduces the reliability and efficiency of the converter.

发明内容 Contents of the invention

本发明的目的在于针对上述变换器所存在的技术缺陷提供一种抑制副边电压振荡的软开关全桥直流变换器，基于原边超前换流思想，由辅助变压器引入换流电压源，辅助耦合电感提供实现原边开关管软开关的能量，大大拓宽了变换器软开关范围，副边整流输出电压振荡得到了很好的抑制，且副边不存在占空比的丢失，同时滤波电感电流纹波减小，降低了导通损耗和输出噪声。The purpose of the present invention is to provide a soft-switching full-bridge DC converter that suppresses the secondary side voltage oscillation against the technical defects of the above-mentioned converter. The inductance provides the energy to realize the soft switching of the primary switching tube, which greatly broadens the soft switching range of the converter. The secondary side rectified output voltage oscillation is well suppressed, and there is no loss of duty cycle in the secondary side. At the same time, the inductor current ripple is filtered waves are reduced, reducing conduction loss and output noise.

本发明为实现上述目的，采用如下技术方案：In order to achieve the above object, the present invention adopts the following technical solutions:

本发明的一种抑制副边电压振荡的软开关全桥直流变换器，包括直流电源、结构相同的第一逆变桥臂和第二逆变桥臂、隔离变压器以及整流滤波电路；其中每个逆变桥臂都包括二个开关管、二个体二极管和二个寄生电容，第一开关管的漏极分别与第一体二极管阴极、第一寄生电容的一端连接构成逆变桥臂的正输入端，第一开关管的源极分别与第一体二极管阳极、第一寄生电容的另一端、第二开关管的漏极、第二体二极管阴极、第二寄生电容的一端连接构成逆变桥臂的输出端，第二开关管的源极分别与第二体二极管阳极、第二寄生电容的另一端连接构成逆变桥臂的负输入端，直流电源的正极分别接第一逆变桥臂和第二逆变桥臂的正输入端，直流电源的负极分别接第一逆变桥臂和第二逆变桥臂的负输入端，隔离变压器副边绕组的输出端接整流滤波电路的输入端，其特征在于：A soft-switching full-bridge DC converter for suppressing secondary side voltage oscillation of the present invention includes a DC power supply, a first inverter bridge arm and a second inverter bridge arm with the same structure, an isolation transformer, and a rectification and filtering circuit; each The inverter bridge arm includes two switch tubes, two body diodes and two parasitic capacitors, the drain of the first switch tube is respectively connected to the cathode of the first body diode and one end of the first parasitic capacitor to form the positive input of the inverter bridge arm terminal, the source of the first switching tube is connected to the anode of the first body diode, the other end of the first parasitic capacitor, the drain of the second switching tube, the cathode of the second body diode, and one end of the second parasitic capacitor to form an inverter bridge The output end of the arm, the source of the second switching tube are respectively connected with the anode of the second body diode and the other end of the second parasitic capacitor to form the negative input end of the inverter bridge arm, and the positive pole of the DC power supply is respectively connected to the first inverter bridge arm and the positive input terminal of the second inverter bridge arm, the negative pole of the DC power supply is respectively connected to the negative input terminals of the first inverter bridge arm and the second inverter bridge arm, and the output terminal of the secondary winding of the isolation transformer is connected to the input of the rectification filter circuit end, characterized by:

还包括由辅助电感、辅助变压器和辅助电容构成的辅助网络；其中辅助电感为耦合电感，原边绕组的一端接第一桥臂的输出端，原边绕组的另一端接耦合电感副边绕组与之异名的一端构成耦合电感的中点，副边绕组的另一端接第二逆变桥臂的输出端。辅助变压器原边绕组的一端接辅助耦合电感的中点，另一端接辅助电容的一端，辅助电容的另一端接直流电源的负极，辅助变压器副边绕组中与辅助变压器原边绕组接辅助电容的一端是同名端的一端接第一逆变桥臂的输出端，辅助变压器副边绕组的另一端接隔离变压器原边绕组的一端，隔离变压器原边绕组的另一端接第二逆变桥臂的输出端。It also includes an auxiliary network composed of auxiliary inductors, auxiliary transformers and auxiliary capacitors; wherein the auxiliary inductor is a coupled inductor, one end of the primary winding is connected to the output end of the first bridge arm, and the other end of the primary winding is connected to the secondary winding of the coupled inductor and One end of the different name constitutes the midpoint of the coupled inductor, and the other end of the secondary winding is connected to the output end of the second inverter bridge arm. One end of the primary winding of the auxiliary transformer is connected to the midpoint of the auxiliary coupling inductor, the other end is connected to one end of the auxiliary capacitor, the other end of the auxiliary capacitor is connected to the negative pole of the DC power supply, and the secondary winding of the auxiliary transformer is connected to the primary winding of the auxiliary transformer. One end is the end of the same name, one end is connected to the output end of the first inverter bridge arm, the other end of the secondary winding of the auxiliary transformer is connected to one end of the primary winding of the isolation transformer, and the other end of the primary winding of the isolation transformer is connected to the output of the second inverter bridge arm end.

本发明披露了一种抑制副边电压振荡的软开关全桥直流变换器，其可以有效抑制副边整流电压存在的尖峰及振荡，并在宽负载范围实现开关管的零电压开关。与原有技术相比其主要技术特点是，基于原边超前换流思想，利用所述辅助变压器的副边绕组电压作为换流电压源，原边电流在环流阶段即实现换向，副边不存在占空比的丢失，存储于所述辅助耦合电感的能量可以在宽范围内实现原边开关管的零电压开关。由于辅助变压器的引入，使得隔离变压器在传统的零状态阶段由辅助电容向副边提供能量，滤波电感电流纹波小，降低了滤波电路的导通损耗及输出噪声，变换器的性能得到提高。The invention discloses a soft-switching full-bridge DC converter capable of suppressing secondary side voltage oscillation, which can effectively suppress the peak and oscillation of secondary rectified voltage, and realize zero-voltage switching of switching tubes in a wide load range. Compared with the original technology, its main technical feature is that, based on the idea of primary-side advanced commutation, the secondary winding voltage of the auxiliary transformer is used as the commutation voltage source, and the primary-side current realizes commutation during the circulating current stage, and the secondary side does not There is a loss of the duty cycle, and the energy stored in the auxiliary coupling inductor can realize the zero-voltage switching of the primary switching tube in a wide range. Due to the introduction of the auxiliary transformer, the isolation transformer provides energy from the auxiliary capacitor to the secondary side in the traditional zero-state stage, the filter inductor current ripple is small, the conduction loss and output noise of the filter circuit are reduced, and the performance of the converter is improved.

附图说明 Description of drawings

附图1是副边加RCD吸收电路的移相全桥变换器电路结构示意图。Accompanying drawing 1 is the schematic diagram of the circuit structure of the phase-shifted full-bridge converter with an RCD absorbing circuit on the secondary side.

附图2是原边加箝位二极管的移相全桥变换器电路结构示意图。Accompanying drawing 2 is the schematic diagram of the circuit structure of the phase-shifting full-bridge converter with clamping diodes on the primary side.

附图3是本发明的一种抑制副边电压振荡的软开关全桥直流变换器电路结构示意图。Accompanying drawing 3 is a schematic diagram of the circuit structure of a soft-switching full-bridge DC converter suppressing secondary side voltage oscillation in the present invention.

附图4是本发明的一种抑制副边电压振荡的软开关全桥直流变换器中辅助耦合电感等效后的电路结构示意图。Accompanying drawing 4 is a schematic diagram of the circuit structure after equivalent auxiliary coupling inductance in a soft-switching full-bridge DC converter suppressing secondary side voltage oscillation of the present invention.

附图5是本发明的一种抑制副边电压振荡的软开关全桥直流变换器主要工作波形示意图。Figure 5 is a schematic diagram of the main working waveforms of a soft-switching full-bridge DC converter suppressing secondary voltage oscillation in the present invention.

附图6～附图11是本发明的一种抑制副边电压振荡的软开关全桥直流变换器在半个工作周期内的各开关模态示意图。Accompanying drawings 6 to 11 are schematic diagrams of each switch mode in a half working cycle of a soft-switching full-bridge DC converter suppressing secondary side voltage oscillation of the present invention.

附图12是本发明的一种抑制副边电压振荡的软开关全桥直流变换器与传统全桥变换器副边整流输出电压v_rect和输出电压V_o简化波形示意图。Fig. 12 is a schematic diagram of simplified waveforms of a soft-switching full-bridge DC converter suppressing secondary voltage oscillation of the present invention and a traditional full-bridge converter secondary rectified output voltage v _rect and output voltage V _o .

上述附图中的主要符号名称：V_in、电源电压。Q₁～Q₄、功率开关管。C₁～C₄、寄生电容。D₁～D₄、体二极管。T_ra、辅助变压器。C_a、辅助电容。L_a、辅助耦合电感。T_r、隔离变压器。L_k、隔离变压器漏感。L_r、串联谐振电感。L_m、激磁电感。D_R1、D_R2、输出整流二极管。C_DR1、C_DR2、输出整流二极管结电容。D_c、C_c、R_c、分别为RCD吸收电路中的二极管、吸收电容、吸收电阻。D_a1、D_a2、箝位二极管。v_rect、整流输出电压。L_f、滤波电感。C_f、滤波电容。R_Ld、负载。V_a、输出电压。v_AB、A与B两点间电压。v_OP、辅助变压器原边绕组O与P两点间电压。v_AC、辅助变压器副边绕组A与C两点间电压。Names of main symbols in the above drawings: _Vin , power supply voltage. Q ₁ -Q ₄ , power switch tubes. C ₁ ~C ₄ , parasitic capacitance. D ₁ -D ₄ , body diodes. T _ra , auxiliary transformer. C _a , auxiliary capacitor. L _a , auxiliary coupling inductance. T _r , isolation transformer. L _k , isolation transformer leakage inductance. L _r , series resonant inductance. L _m , exciting inductance. D _R1 , D _R2 , output rectifier diode. C _DR1 , C _DR2 , output rectifier diode junction capacitance. D _c , C _c , and R _c are the diode, the absorbing capacitor, and the absorbing resistor in the RCD absorbing circuit, respectively. D _a1 , D _a2 , clamping diodes. v _rect , rectified output voltage. L _f , filter inductance. C _f , filter capacitor. R _Ld , load. V _a , output voltage. v _AB , the voltage between A and B. v _OP , the voltage between the primary winding O and P of the auxiliary transformer. v _AC , voltage between two points of auxiliary transformer secondary winding A and C.

具体实施方式 detailed description

下面结合附图对发明的技术方案进行详细说明：Below in conjunction with accompanying drawing, the technical scheme of invention is described in detail:

附图3所示的是一种抑制副边电压振荡的软开关全桥直流变换器电路结构示意图。由直流电源1、两个逆变桥臂2和3、隔离变压器4、辅助耦合电感5、辅助变压器6、辅助电容7及整流滤波电路8组成。Q₁～Q₄是四只功率开关管，D₁～D₄分别是开关管Q₁～Q₄的体二极管，C₁～C₄分别是开关管Q₁～Q₄的寄生电容，T_ra是辅助变压器，L_a是辅助耦合电感，C_a是辅助电容，T_r是隔离变压器，L_k是隔离变压器的漏感，D_R1、D_R2是输出整流二极管，C_DR1、C_DR2分别是整流二极管D_R1、D_R2的结电容，L_f是输出滤波电感，C_f是输出滤波电容，R_Ld为负载。其中L_a为匝比n_La＝1的耦合电感，而耦合电感类似于一个具有特定激磁电感的理想变压器，为了便于分析，可将附图3等效为附图4所示的电路。本变换器采用移相控制，开关管Q₄和Q₂分别滞后于开关管Q₁和Q₃一个相位，称开关管Q₁和Q₃组成的第一逆变桥臂为超前桥臂，开关管Q₂和Q₄组成的第二逆变桥臂则为滞后桥臂。辅助电容C_a的电压为输入电压V_in的一半，即v_Ca＝V_in/2，可视为一电压源。Figure 3 is a schematic structural diagram of a soft-switching full-bridge DC converter circuit that suppresses secondary side voltage oscillation. It consists of a DC power supply 1, two inverter bridge arms 2 and 3, an isolation transformer 4, an auxiliary coupling inductor 5, an auxiliary transformer 6, an auxiliary capacitor 7 and a rectification and filtering circuit 8. Q ₁ ~ Q ₄ are four power switching tubes, D ₁ ~ D ₄ are the body diodes of switching tubes Q ₁ ~ Q ₄ respectively, C ₁ ~ C ₄ are the parasitic capacitances of switching tubes Q ₁ ~ Q ₄ respectively, T _ra is the auxiliary transformer, L _a is the auxiliary coupling inductance, C _a is the auxiliary capacitor, T _r is the isolation transformer, L _k is the leakage inductance of the isolation transformer, D _R1 and D _R2 are the output rectifier diodes, C _DR1 and C _DR2 are the rectifier The junction capacitance of diodes D _R1 and D _R2 , L _f is the output filter inductance, C _f is the output filter capacitor, R _Ld is the load. Wherein L _a is a coupled inductance with a turn ratio n _La =1, and the coupled inductance is similar to an ideal transformer with a specific magnetizing inductance. For the convenience of analysis, the accompanying drawing 3 can be equivalent to the circuit shown in drawing 4. The converter adopts phase-shift control, and the switching tubes _Q4 and _Q2 lag behind the switching tubes Q1 and _Q3 by _one phase respectively. The _first inverter bridge arm composed of the switching tubes Q1 and _Q3 is called the leading bridge arm. The second inverter bridge arm composed of tubes _Q2 and _Q4 is a lagging bridge arm. The voltage of the auxiliary capacitor C _a is half of the input voltage _Vin , that is, v _Ca =V _in /2, which can be regarded as a voltage source.

为了分析方便，下面以附图4所示的等效后的主电路结构，结合附图6～附图11叙述本发明的具体工作原理。由附图5可知整个变换器一个开关周期有12种开关模态，分别是[t₀-t₁]、[t₁-t₂]、[t₂-t₃]、[t₃-t₄]、[t₄-t₅]、[t₅-t₆]、[t₆-t₇]、[t₇-t₈]、[t₈-t₉]、[t₉-t₁₀]、[t₁₀-t₁₁]、[t₁₁-t₁₂]，其中，[t₀-t₆]为前半周期，[t₆-t₁₂]为后半周期。下面对各开关模态的工作情况进行具体分析。For the convenience of analysis, the specific working principle of the present invention will be described below with the equivalent main circuit structure shown in Fig. 4 in conjunction with Fig. 6 to Fig. 11 . It can be seen from Figure 5 that there are 12 switching modes in one switching period of the entire converter, which are [t ₀ -t ₁ ], [t ₁ -t ₂ ], [t ₂ -t ₃ ], [t ₃ -t ₄ ], [t ₄ -t ₅ ], [t ₅ -t ₆ ], [t ₆ -t ₇ ], [t ₇ -t ₈ ], [t ₈ -t ₉ ], [t ₉ -t ₁₀ ], [t ₁₀ -t ₁₁ ], [t ₁₁ -t ₁₂ ], where [t ₀ -t ₆ ] is the first half period, and [t ₆ -t ₁₂ ] is the second half period. The working conditions of each switch mode are analyzed in detail below.

在分析之前，先作如下假设：①所有开关管和二极管均为理想器件；②滤波电感足够大，因此隔离变压器副边输出可等效为恒流源，辅助电容足够大，可视为恒压源，且电压为V_in/2，所有电感、电容均为理想元件；③C₁＝C₃＝C_lead，C₂＝C₄＝C_lag。1.开关模态1[t₀-t₁][对应于附图6]Before the analysis, make the following assumptions: ①All switches and diodes are ideal devices; ②The filter inductance is large enough, so the output of the secondary side of the isolation transformer can be equivalent to a constant current source, and the auxiliary capacitor is large enough, which can be regarded as a constant voltage source, and the voltage is V _in /2, all inductors and capacitors are ideal components; ③C ₁ ＝C ₃ ＝C _lead , C ₂ ＝C ₄ ＝C _lag . 1. Switch mode 1[t ₀ -t ₁ ][corresponding to accompanying drawing 6]

Q₁和Q₄导通，Q₂和Q₃截止，原边电流近似不变，i_p＝I_o/n(其中n为隔离变压器原副边匝比)，v_AB＝V_in，上整流二极管D_R1流过全部负载电流，D_R2截止，原边给负载供电。由于辅助电容电压稳定在V_in/2，辅助变压器原副边绕组电压均为零。辅助耦合电感等效励磁电感L_in两端电压为V_in，励磁电流i_m线性上升，同时超前臂辅助电流i₁和滞后臂辅助电流i₂也线性上升。i_m(t)、i₁(t)、i₂(t)及i_a(t)可表示为Q ₁ and Q ₄ are turned on, Q ₂ and Q ₃ are turned off, the primary current is approximately constant, i _p =I _o /n (where n is the primary and secondary turns ratio of the isolation transformer), v _AB =V _in , up rectification Diode D _R1 flows through all the load current, D _R2 is cut off, and the primary side supplies power to the load. Since the voltage of the auxiliary capacitor is stable at V _in /2, the voltage of the primary and secondary windings of the auxiliary transformer is zero. The voltage across the equivalent excitation inductance L _in of the auxiliary coupled inductor is V _in , the excitation current im rises linearly, and the auxiliary current _i ₁ of the advanced forearm and the auxiliary current i ₂ of the lagging arm also increase linearly. i _m (t), i ₁ (t), i ₂ (t) and i _a (t) can be expressed as

${i i}_{m m} ((t t)) = = \frac{{V V}_{in in}}{{L L : :}_{m m}} ((t t - - {t t}_{00})) - - {i i}_{m m} (({t t}_{00})) - - - - - - ((11))$

${i i}_{11} ((t t)) = = {i i}_{m m} ((t t)) + + \frac{{i i}_{a a}}{22} - - - - - - ((22))$

${i i}_{22} ((t t)) = = {i i}_{m m} ((t t)) - - \frac{{i i}_{a a}}{22} - - - - - - ((33))$

i_a(t)＝i_p(t)(4)i _a (t) = i _p (t) (4)

其中，L_m为辅助耦合电感的等效励磁电感，i_m(t₀)为辅助耦合电感励磁电流在t₀时刻的值。Among them, L _m is the equivalent excitation inductance of the auxiliary coupling inductor, and i _m (t ₀ ) is the value of the excitation current of the auxiliary coupling inductor at time t ₀ .

而由式(1)可知，在整个工作周期内耦合电感励磁电流幅值可近似表示为It can be seen from formula (1) that the amplitude of the excitation current of the coupled inductor in the entire working cycle can be approximately expressed as

${I I}_{m m} = = \frac{11}{22} \frac{{V V}_{in in}}{{L L}_{m m}} D D. \frac{{T T}_{s the s}}{22} - - - - - - ((55))$

存储于辅助耦合电感中的能量可表示为The energy stored in the auxiliary coupled inductor can be expressed as

${E E.}_{m m} = = \frac{11}{22} {L L}_{m m} {I I}_{m m}^{22} = = \frac{11}{3232} \frac{{V V}_{m m}^{22} {T T}_{s the s}^{22}}{{L L}_{m m}} {D D.}^{22} - - - - - - ((66))$

2.开关模态2[t₁-t₂][对应于附图7]2. Switch mode 2[t ₁ -t ₂ ][corresponding to accompanying drawing 7]

t₁时刻关断Q₁，电流(i_p+i₁)从Q₁中转移到C₁和C₃支路中。在这个时段里，i_p和i₁同时给C₁充电，给C₃放电，v_AB由V_in逐渐下降，v_rect也相应下降。由于辅助耦合电感与滤波电感均较大，(i_p+i₁)可视为恒流源，因而v_AB、v_rect均呈线性变化。直到t₂时刻，v_rect首先下降到零，副边两整流二极管同时导通，隔离变压器原副边绕组电压被箝位在零。此阶段v_AB与v_rect关系可表示为：At moment t ₁ , Q ₁ is turned off, and the current (ip +i ₁ ) is transferred from _Q ₁ to C ₁ and C ₃ branches. During this period, i _p and i ₁ charge C ₁ and discharge C ₃ at the same time, v _AB gradually decreases from V _in , and v _rect also decreases accordingly. Since the auxiliary coupling inductance and filter inductance are large, ( _ip +i ₁ ) can be regarded as a constant current source, so v _AB and v _rect both change linearly. Until _t2 , v _rect first drops to zero, the two rectifier diodes on the secondary side are turned on at the same time, and the voltage of the primary and secondary windings of the isolation transformer is clamped at zero. The relationship between v _AB and v _rect at this stage can be expressed as:

v_AB＝v_AC+n_vrect(7)v _AB = v _AC + n _vrect (7)

其中v_AC为辅助变压器副边绕组两端的电压。Where v _AC is the voltage across the secondary winding of the auxiliary transformer.

可以看出由于辅助变压器的影响，v_AB并不会与v_rect同时下降到零。而v_AC又可以表示为：It can be seen that due to the influence of the auxiliary transformer, v _AB will not drop to zero at the same time as v _rect . And v _AC can be expressed as:

${v v}_{AC AC} = = {v v}_{OP OP} = = {v v}_{Ca Ca} - - \frac{{v v}_{AB AB}}{22} - - - - - - ((88))$

由式(7)(8)可推出，当v_rect降到零时，即t₂时刻，v_AC(t₂)＝V_in/3。It can be deduced from formulas (7) (8) that when v _rect drops to zero, that is, at time t ₂ , v _AC (t ₂ )=V _in /3.

3.开关模态3[t₂-t₃][对应于附图8]3. Switch mode 3 [t ₂ -t ₃ ] [corresponding to accompanying drawing 8]

漏感L_k开始承受负向电压，原边电流i_p开始减小。C₃在i_p及超前臂辅助电流i₁的作用下继续放电，v_AB继续下降，v_OP继续增加。在t₃时刻，C₃的电压下降到零，Q₃的反并联二极管D₃自然导通。The leakage inductance L _k begins to bear the negative voltage, and the primary current i _p begins to decrease. C ₃ continues to discharge under the action of i _p and super forearm auxiliary current i ₁ , v _AB continues to drop, and v _OP continues to increase. At time _t3 , the voltage of C3 drops to zero, and the antiparallel diode _D3 _of _Q3 is naturally turned on.

4.开关模态4[t₃-t₄][对应于附图9]4. Switch mode 4[t ₃ -t ₄ ][corresponding to accompanying drawing 9]

D₃导通后，可开通Q₃，此时Q₃为零电压开通。Q₁和Q₃驱动信号之间的死区时间t_d(lead)＞t₁₃。A点电位下降为零，所以v_AB＝0，辅助耦合电感原副边绕组电压均为零，v_Op稳定在V_in/2。辅助变压器副边绕组耦合的电压(即v_AC)反向加在漏感L_k两端，原边电流继续下降并反向。由于强制原边换流的电压V_in/2较大，原边换流时间十分短暂。并且与传统全桥变换器相比，此变换器原边电流换向的时刻提前。After D ₃ is turned on, Q ₃ can be turned on, and at this time, Q ₃ is turned on with zero voltage. The dead time t _d(lead) >t ₁₃ between the driving signals of Q ₁ and Q ₃ . The potential of point A drops to zero, so v _AB = 0, the voltage of the primary and secondary windings of the auxiliary coupled inductor is zero, and v _Op is stable at V _in /2. The voltage coupled by the secondary winding of the auxiliary transformer (ie v _AC ) is reversely applied to both ends of the leakage inductance L _k , and the primary current continues to drop and reverse. Since the voltage V _in /2 of the forced primary side commutation is relatively large, the primary side commutation time is very short. And compared with the traditional full-bridge converter, the commutation time of the primary side current of this converter is earlier.

5.开关模态5[t₄-t₅][对应于附图10]5. Switch mode 5[t ₄ -t ₅ ][corresponding to accompanying drawing 10]

在t₄时刻原边电流反向上升到-I_o/n，原边换流成功，D_R1关断，D_R2流过全部负载电流。此时由于v_AB仍为零，辅助变压器副边绕组电压仍为V_in/2。漏感L_k与整流管结电容C_DR1构成谐振回路，副边整流输出电压v_rect(t)可表示为 _At time t4, the current of the primary side rises reversely to -I _o /n, the commutation of the primary side is successful, _DR1 is turned off, and _DR2 flows through the full load current. At this time, because v _AB is still zero, the secondary winding voltage of the auxiliary transformer is still V _in /2. The leakage inductance L _k and the rectifier junction capacitance C _DR1 form a resonant circuit, and the rectified output voltage v _rect (t) of the secondary side can be expressed as

${v v}_{rect rect} ((t t)) = = \frac{11}{n no} {v v}_{Ct CT} ((t t)) = = \frac{11}{n no} [[\frac{{V V}_{in in}}{22} - - \frac{{V V}_{in in}}{22} cos cos (({ω ω}_{00} ((t t - - {t t}_{44}))))]] - - - - - - ((99))$

其中：C_t为结电容C_DR1折算至原边的等效电容。in: C _t is the equivalent capacitance converted from the junction capacitance C _DR1 to the primary side.

由上式可以看出，整流二极管上存在V_in/n的峰值电压，但这并没有提高整流二极管的电压应力。此阶段原边仍向副边传递能量，传递的功率为正常有源状态下的1/2。此时原边传递的能量并不是由直流电源提供，而是由辅助电容C_a释能维持。It can be seen from the above formula that there is a peak voltage of V _in /n on the rectifier diode, but this does not increase the voltage stress of the rectifier diode. At this stage, the primary side still transmits energy to the secondary side, and the transmitted power is 1/2 of the normal active state. At this time, the energy delivered by the primary side is not provided by the DC power supply, but maintained by the release energy of the auxiliary capacitor C _a .

6.开关模态6[t₅-t₆][对应于附图11]6. Switch mode 6[t ₅ -t ₆ ][corresponding to accompanying drawing 11]

t₅时刻，Q₄关断，由于此时原边电流已反向，滞后臂辅助电流i₂一方面要补偿原边电流，一方面要提供C₂和C₄的充放电电流。同样地，i₂可近似看成恒流源，从而C₄两端电压近似线性上升，C_DR1也在滞后臂辅助电流i₂的作用下继续充电，v_rect继续上升。忽略漏感的影响，v_Q4(t)、v_rect(t)及v_AC(t)可表示为 _At time t5, Q ₄ is turned off. Since the primary current has reversed at this time, the auxiliary current i ₂ of the lagging arm must compensate the primary current on the one hand and provide the charge and discharge current of C ₂ and C ₄ on the other hand. Similarly, i ₂ can be approximately regarded as a constant current source, so that the voltage across C ₄ rises approximately linearly, C _DR1 also continues to charge under the action of the auxiliary current i ₂ of the lagging arm, and v _rect continues to rise. Neglecting the effect of leakage inductance, v _Q4 (t), v _rect (t) and v _AC (t) can be expressed as

${v v}_{Q Q 44} ((t t)) = = \frac{{i i}_{p p} (({t t}_{55})) + + {i i}_{22} (({t t}_{55}))}{22 {C C}_{oss oss} + + {C C}_{t t}} ((t t - - {t t}_{55})) - - - - - - ((1010))$

${v v}_{rect rect} ((t t)) = = \frac{{v v}_{Q Q 44} ((t t)) + + {v v}_{AC AC} ((t t))}{n no} - - - - - - ((1111))$

${v v}_{AC AC} ((t t)) = = {v v}_{OP OP} ((t t)) = = {v v}_{Ca Ca} - - \frac{{v v}_{Q Q 44} ((t t))}{22} - - - - - - ((1212))$

由上式看出v_rect近似线性上升，没有振荡。直到t₆时刻，B点电位上升到输入电压V_in，D₂自然导通，此时开通Q₂可实现其零电压开关。v_rect上升到V_in/n，原边向副边传递能量，电路进入下半个工作周期[t₆-t₁₂]，其工作情况类似于上述的半个周期[t₀-t₆]，这里不再赘述。It can be seen from the above formula that v _rect rises approximately linearly without oscillation. Until the moment t6, the potential of point B rises to the input voltage V _in , D2 is naturally turned _on , at this time, turning _on _Q2 can realize its zero-voltage switching. v _rect rises to V _in /n, the primary side transfers energy to the secondary side, and the circuit enters the second half working cycle [t ₆ -t ₁₂ ], and its working condition is similar to the above half cycle [t ₀ -t ₆ ], I won't go into details here.

为了说明本发明中输出滤波电感电流纹波小于传统的移相全桥变换器，附图12给出了本发明与传统全桥变换器中整流输出电压v_rect和输出电压V_o的简化波形图。In order to illustrate that the current ripple of the output filter inductor in the present invention is smaller than that of the traditional phase-shifted full-bridge converter, accompanying drawing 12 provides simplified waveform diagrams of the rectified output voltage v _rect and the output voltage V _o in the present invention and the traditional full-bridge converter .

假定传统全桥变换器与本发明提出的全桥变换器具有相同的输入输出指标，且两者主变压器匝比相同。从而有：It is assumed that the traditional full-bridge converter and the full-bridge converter proposed by the present invention have the same input and output indicators, and the turn ratio of the main transformers is the same. Thus there are:

${V V}_{o o} = = \frac{{V V}_{in in}}{n no} {D D.}_{11} = = \frac{{V V}_{in in}}{n no} {D D.}_{22} + + \frac{{V V}_{in in}}{22 n no} ((11 - - {D D.}_{22})) - - - - - - ((1313))$

传统全桥变换器中滤波电感电流纹波ΔI_o1与本发明中变换器滤波电感电流纹波ΔI_o2可表示如下：The filter inductor current ripple ΔI _o1 in the traditional full-bridge converter and the converter filter inductor current ripple ΔI _o2 in the present invention can be expressed as follows:

$Δ Δ {I I}_{o o 11} = = \frac{\frac{{V V}_{in in}}{n no} - - {V V}_{o o}}{{L L}_{f f}} {D D.}_{11} \frac{{T T}_{s the s}}{22} - - - - - - ((1414))$

$Δ Δ {I I}_{o o 22} = = \frac{\frac{{V V}_{in in}}{n no} - - {V V}_{o o}}{{L L}_{f f}} {D D.}_{22} \frac{{T T}_{s the s}}{22} - - - - - - ((1515))$

结合(13)(14)(15)，可推出：Combining (13)(14)(15), it can be introduced:

$\frac{Δ Δ {I I}_{o o 22}}{Δ Δ {I I}_{o o 11}} = = 22 - - \frac{11}{{D D.}_{11}} - - - - - - ((1616))$

忽略传统全桥变换器中副边占空比的丢失，假设在输入电压最低时副边整流输出电压满占空比工作，即D₁＝1，两种变换器滤波电感电流纹波相等。但随着输入电压的增加D₁相应地减小，输入电压最大时D₁最小，ΔI_o2/ΔI_o1最小，此时本发明中变换器滤波电感电流纹波减小的优势也最明显。Ignoring the loss of the secondary duty cycle in the traditional full-bridge converter, assuming that the secondary rectified output voltage works at a full duty cycle when the input voltage is the lowest, that is, D ₁ =1, the filter inductor current ripple of the two converters is equal. However, as the input voltage increases, D ₁ decreases correspondingly. When the input voltage is the largest, D ₁ is the smallest, and ΔI _o2 /ΔI _o1 is the smallest. At this time, the advantage of reducing the current ripple of the filter inductor of the converter in the present invention is also the most obvious.

从以上的描述可以得知，本发明提出的一种抑制副边电压振荡的软开关全桥直流变换器具有以下几方面的优点：It can be known from the above description that a soft-switching full-bridge DC converter proposed by the present invention that suppresses secondary voltage oscillation has the following advantages:

1)利用辅助变压器上的电压实现原边超前换流，换流后副边整流电压尖峰得到了很好的抑制，降低输出整流二极管的电压应力及其导通损耗，同时解决了占空比丢失的问题。1) The voltage on the auxiliary transformer is used to realize the commutation of the primary side in advance. After the commutation, the rectification voltage peak of the secondary side is well suppressed, which reduces the voltage stress and conduction loss of the output rectifier diode, and at the same time solves the loss of duty cycle The problem.

2)辅助耦合电感存储的能量拓宽了原边开关管的软开关范围。2) The energy stored in the auxiliary coupling inductor broadens the soft switching range of the primary switching tube.

3)减小了输出滤波电感电流纹波，降低了导通损耗及输出噪声，提高系统的可靠性，减轻EMI。3) The current ripple of the output filter inductor is reduced, the conduction loss and output noise are reduced, the reliability of the system is improved, and EMI is reduced.

Claims

1. suppress a soft switching full-bridge direct-current converter for secondary-side voltage oscillation, first inverter bridge leg (2) identical including DC source (1), structure and the second inverter bridge leg (3), isolating transformer (4) and current rectifying and wave filtering circuit (8)；nullWherein each inverter bridge leg includes two switching tubes、Two individual diodes and two parasitic capacitances，The drain electrode of the first switching tube respectively with the first body diode negative electrode、One end of first parasitic capacitance connects and composes the positive input terminal of inverter bridge leg，The source electrode of the first switching tube respectively with the first body diode anode、The other end of the first parasitic capacitance、The drain electrode of second switch pipe、Second body diode negative electrode、One end of second parasitic capacitance connects and composes the outfan of inverter bridge leg，The source electrode of second switch pipe respectively with the second body diode anode、The other end of the second parasitic capacitance connects and composes the negative input end of inverter bridge leg，The positive pole of DC source (1) connects the first inverter bridge leg (2) and the positive input terminal of the second inverter bridge leg (3) respectively，The negative pole of DC source (1) connects the first inverter bridge leg (2) and the negative input end of the second inverter bridge leg (3) respectively，The input of output termination current rectifying and wave filtering circuit (8) of isolating transformer (4) vice-side winding，It is characterized in that:

Also include the auxiliary network being made up of auxiliary induction (5), auxiliary transformer (6) and auxiliary capacitor (7)；Wherein auxiliary induction is coupling inductance, the outfan of one termination the first inverter bridge leg of primary side winding, one end of another termination auxiliary induction vice-side winding different name with it of primary side winding constitutes the midpoint of auxiliary induction, another of vice-side winding terminates the outfan of the second inverter bridge leg, the midpoint of one termination auxiliary induction of auxiliary transformer (6) primary side winding, one end of another termination auxiliary capacitor, the negative pole of another termination DC source (1) of auxiliary capacitor, the one end connecing auxiliary capacitor in auxiliary transformer vice-side winding with auxiliary transformer primary side winding is the outfan that the one of Same Name of Ends terminates the first inverter bridge leg, one end of another termination isolating transformer primary side winding of auxiliary transformer vice-side winding, another of isolating transformer primary side winding terminates the outfan of the second inverter bridge leg.

2. a kind of soft switching full-bridge direct-current converter suppressing secondary-side voltage oscillation as claimed in claim 1, it is characterised in that the former vice-side winding turn ratio of described auxiliary transformer is 1: 1, the former vice-side winding turn ratio of described auxiliary induction is 1: 1.