WO2022016835A1 - 一种llc谐振变换器的电流检测方法及装置 - Google Patents

一种llc谐振变换器的电流检测方法及装置 Download PDF

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WO2022016835A1
WO2022016835A1 PCT/CN2021/072339 CN2021072339W WO2022016835A1 WO 2022016835 A1 WO2022016835 A1 WO 2022016835A1 CN 2021072339 W CN2021072339 W CN 2021072339W WO 2022016835 A1 WO2022016835 A1 WO 2022016835A1
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current
resonant
resonant converter
llc resonant
llc
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PCT/CN2021/072339
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English (en)
French (fr)
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刘洋
王伟康
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华中科技大学
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Priority to EP21845927.9A priority Critical patent/EP4012911A4/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
    • H02M3/33573—Full-bridge at primary side of an isolation transformer
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R19/00—Arrangements for measuring currents or voltages or for indicating presence or sign thereof
    • G01R19/0092—Arrangements for measuring currents or voltages or for indicating presence or sign thereof measuring current only
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/0003—Details of control, feedback or regulation circuits
    • H02M1/0009—Devices or circuits for detecting current in a converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/01—Resonant DC/DC converters

Definitions

  • the invention belongs to the technical field of switching power supplies of power electronics, and more particularly, relates to a current detection method and device of an LLC resonant converter.
  • the ultra-high switching frequency and the characteristics of the LLC itself make it difficult for ordinary current detection methods to obtain accurate real-time output current information of the LLC resonant converter, that is, the instantaneous load of the LLC resonant converter is difficult to know.
  • the precise control of converters and the current sharing control of interleaved parallel LLC resonant converters pose challenges.
  • the switching frequency of LLC resonant converters was generally low. Estimate the current waveform of each cycle; in the case where the real-time current information is not required, the low-pass filter sampling of the high-frequency half-wave current through the low-pass filter circuit can also be performed, and the actual waveform can be estimated by the sampled low-pass current value.
  • the obvious problem with this method is that the dynamic characteristics are poor, and the sampling of the current has a hysteresis, which will have a negative impact on the algorithm with high dynamic characteristics, especially when the converter is unstable.
  • the present invention provides a current detection method and device for an LLC resonant converter, aiming to solve the problem that the current detection method of a high-frequency LLC resonant converter cannot accurately acquire the LLC resonant converter in real time. technical issues of current information.
  • a current detection method for an LLC resonant converter comprising:
  • the LLC resonant converter After the resonant current i r LLC resonant converter is decomposed into sine and cosine components in the form of superposition, the LLC resonant converter output current to the resonant current i D finishing LLC resonant converter and the expression r i m of the excitation current i formula i d (t);
  • the present invention decomposes the resonant current ir of the LLC resonant converter into the form of superposition of sine components and cosine components, so that the expression of the resonant current ir only contains two unknowns, the amplitude of the sine component and the amplitude of the cosine component; finishing the current i d is the LLC resonant converter resonant current i r i m of the excitation current and the expression d (t) i, since the excitation current i m and structure parameters and the output voltage of the LLC resonant converter only these known parameters related, so the expression i d (t) only the same two unknowns; time since the start of a half cycle of resonance, and resonant current i R & lt presence of excitation current i m equal relationship, the output current i D only once sampling, can obtain the relationship between the resonant current i R & lt magnetizing current i m and at another time, the simultaneous expression of
  • the LLC resonant converter output current i D organized into LLC resonant converter resonant current i r and expression after the excitation current i m d (t) i, the expression i d (t) is:
  • i d (t) N
  • N represents the turns ratio of the primary side to the secondary side of the transformer in the LLC resonant converter
  • t represents the time variable
  • the half resonant period of the output current i d is sampled for the first half resonant period within one switching cycle.
  • the expression of the resonant current ir is:
  • I r1 and I r2 represent the amplitudes of the sine and cosine components of the decomposed resonant current, respectively, t r represents the resonant period of the LLC resonant converter, and t represents the time variable.
  • excitation current i m of LLC resonant converter is expressed as:
  • N represents the turns ratio of the primary side to the secondary side of the transformer in the LLC resonant converter
  • V o represents the output voltage of the LLC resonant converter
  • t r represents the resonant period of the LLC resonant converter
  • L m represents the LLC resonant converter where the transformer magnetizing inductance
  • t represents the time variable.
  • the output current i d to be half the resonant period of the sampling, the second half resonant period within one switching cycle.
  • the expression of the resonant current ir is:
  • I r1 and I r2 represent the amplitudes of the sine and cosine components of the decomposed resonant current, respectively, t r represents the resonant period of the LLC resonant converter, and t represents the time variable.
  • excitation current i m of LLC resonant converter is expressed as:
  • N represents the turns ratio of the primary side to the secondary side of the transformer in the LLC resonant converter
  • V o represents the output voltage of the LLC resonant converter
  • t r represents the resonant period of the LLC resonant converter
  • L m represents the LLC resonant converter where the transformer magnetizing inductance
  • t represents the time variable.
  • the current detection method of the LLC resonant converter provided by the present invention also includes:
  • Output current d i LLC resonant converter waveform expression in a half cycle of the resonant period belongs switching calculates an output current I d corresponding to the peak in the switching period and / or effective value.
  • a current detection device for an LLC resonant converter comprising: a sampling unit and a calculation unit;
  • the resonant current i r LLC resonant converter for decomposing the sine and cosine components in the form of superposition, the LLC resonant converter output current i d finishing resonant current i r LLC resonant converter and excitation expression current i m i d (t);
  • Sampling means for during operation of the LLC resonant converter, optionally in a half cycle of a resonance time t 'the output current i d of one sample, to give sampled current value i d (t'), whereby at time t ', the relationship between the resonant current i r and the excitation current i m;
  • the present invention can real-time calculate the real-time output current of each switching cycle of the LLC converter under high-frequency operation through a single acquisition of instantaneous current and theoretical analysis, improve the dynamic characteristics and response speed of the LLC converter control algorithm, and have It is beneficial to the precise control of LLC resonant converter under high frequency working condition.
  • the present invention only needs a current sampling chip whose sampling speed matches the LLC switching frequency to realize the sampling of a single instantaneous current and complete the current detection, without adding a complex sampling circuit, with low hardware requirements and low cost.
  • Fig. 1 is the structural representation of the existing LLC resonant converter
  • FIG 2 is a conventional LLC resonant converter switching signal, the resonant current i r, a schematic diagram of an output current waveform of the excitation current i d and i m terminal of the rectifier circuit;
  • (A) is a schematic diagram of the switching signal waveform LLC resonant converter
  • (b) is the LLC resonant converter resonant current i r and the waveform diagram of the excitation current i m
  • FIG. 3 is a schematic diagram of a current detection method for an LLC resonant converter provided by an embodiment of the present invention.
  • the structure of the LLC resonant converter is shown in Figure 1.
  • the circuit structure of the LLC resonant converter includes: an input filter capacitor C i , an inverter bridge composed of four switch tubes (Q 1 Q 2 Q 3 Q 4 ), and a resonant inductor L r , resonant capacitor C r , transformer T, rectifier circuit composed of four diodes (D 1 D 2 D 3 D 4 ), and output filter capacitor C o ; point S) is the LLC resonant converter output current i d.
  • the working range of ; among them, the calculation formula of the resonance period t r is specifically
  • the LLC resonant converter After injection of the driving current to the LLC resonant converter shown in FIG. 1, the LLC resonant converter is running, during operation, the switching signal, the resonant current i r, i d output current waveform of the exciting current i m terminal of the rectifier circuit and The schematic diagram is shown in Figure 2.
  • the transformer magnetizing inductance L m is much larger than the resonant inductor L r,
  • the three resonant angular velocity ⁇ r t 0 -t 1 is much smaller than the angular velocity of the resonance period, so in this case the resonant current i r i m exciting current approximately constant.
  • the present invention provides A current detection method and device for an LLC resonant converter is presented.
  • the overall idea is that, based on the working principle of the LLC resonant converter, the output current expression of the LLC resonant converter is transformed by theoretical derivation, so that only one Current sampling can be combined with the known conditions in the LLC resonant converter to solve the current waveform of the output current of the LLC resonant converter in each switching period.
  • the present invention makes the following derivation based on the working principle of the LLC resonant converter:
  • the voltages of the resonant capacitor C r and the resonant inductor L r are represented by u C and u L respectively, and the initial values of the resonant current ir and the voltage u C at time t 0 are represented by I 1,ini and V 1,ini, namely,
  • V i represents the input voltage of the LLC resonant converter
  • V o represents the output voltage of the LLC resonant converter
  • N represents the turns ratio between the primary side and the secondary side of the transformer T;
  • time period t 3 -t 4 (i.e., the second half resonant period), in the same direction opposite to the exciting current i m (t) and the resonant current i r (t) and the waveform change time period t 0 -t 1 size, such as in FIG.
  • a current detection method for an LLC resonant converter includes:
  • the LLC resonant converter After the resonant current i r LLC resonant converter is decomposed into sine and cosine components in the form of superposition, the LLC resonant converter output current to the resonant current i D finishing LLC resonant converter and the expression r i m of the excitation current i formula i d (t);
  • the half resonant period for sampling the output current is the first half resonant period in a switching period, that is, the time period t 0 -t 1 shown in FIG. 2
  • the current sampling point is the LLC resonant converter
  • this embodiment further includes:
  • this embodiment can calculate the real-time output current of each switching cycle of the LLC converter under high frequency operation through a single acquisition of instantaneous current and theoretical analysis, which improves the dynamic characteristics and response speed of the LLC converter control algorithm. , which is beneficial to the precise control of the LLC resonant converter under high frequency operation.
  • Embodiment 2 is a diagrammatic representation of Embodiment 1:
  • a current detection method for an LLC resonant converter is similar to the above-mentioned first embodiment, the difference lies in that, in this embodiment, the half resonant period in which the output current is sampled is the second half of a switching period Resonance period, that is, the time period t 3 -t 4 shown in Figure 2;
  • the instantaneous load of the LLC resonant converter in this period can be deduced.
  • a current detection device for an LLC resonant converter comprising: a sampling unit and a calculation unit;
  • the calculation unit is used to decompose the resonant current i r of the LLC resonant converter into the form of superposition of sine components and cosine components, and organize the output current i d of the LLC resonant converter into the resonant current i r of the LLC resonant converter and the excitation expression current i m i d (t);
  • Sampling means for during operation of the LLC resonant converter, optionally in a half cycle of a resonance time t 'the output current i d of one sample, to give sampled current value i d (t'), whereby at time t ', the relationship between the resonant current and the excitation current i r i m; a sampling unit sampling chip may match the current switching frequency sampling rate;

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  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • General Physics & Mathematics (AREA)
  • Dc-Dc Converters (AREA)

Abstract

一种LLC谐振变换器的电流检测方法及装置，属于电力电子的开关电源技术领域，包括：将LLC谐振变换器的谐振电流（i r）分解为正弦分量和余弦分量叠加的形式后，将LLC谐振变换器的输出电流（i d）整理为LLC谐振变换器的谐振电流（i r）和励磁电流（i m）的表达式i d(t)；在LLC谐振变换器运行的过程中，在半个谐振周期内任选一个时刻t'对输出电流（i d）进行一次采样，得到在时刻t'谐振电流（i r）和励磁电流（i m）的关系，联立该关系，以及在半个谐振周期的开始时刻，谐振电流（i r）和励磁电流（i m）相等的关系，求解得到谐振电流（i r）两个分量的幅值，代入表达式i d(t)，得到LLC谐振变换器的输出电流（i d）在一个开关周期内的波形表达式。能够实现对LLC谐振变换器电流的实时、准确检测，提高后续控制算法的动态性能。

Description

一种LLC谐振变换器的电流检测方法及装置 【技术领域】
本发明属于电力电子的开关电源技术领域，更具体地，涉及一种LLC谐振变换器的电流检测方法及装置。
【背景技术】
为了顺应开关电源的小型化趋势，功率半导体器件选择了高频化的发展方向，因为对于开关电源来说，减小尺寸、提高功率密度最有效的方法就是提高开关频率。近年来，第三代宽禁带半导体因为其优异的高开关频率和低驱动损耗等特性，可以极大地提升电源装置的性能，而在开关电源领域得到了广泛的应用。由于LLC谐振变换器可以在全负载范围实现软开关减小开关损耗，结构简单而高效，和第三代半导体的特性非常契合，因此使用第三代半导体的LLC谐振变换器成为了研究的热点。
不论是单相LLC谐振变换器的精确闭环控制还是多相LLC谐振变换器的精确均流控制，都需要准确快速的电流反馈信息。随着第三代半导体的应用和推广，LLC谐振变换器的开关频率提高到数百kHz甚至MHz级，而且LLC谐振变换器工作时变压器次级侧的整流电路输出电流波形为2倍开关频率的半波波形，电流纹波幅度非常大。超高的开关频率和LLC本身的特性导致普通的电流检测方法很难获得LLC谐振变换器的准确实时输出电流信息，即LLC谐振变换器的瞬时负载难以获知，给高频工作下的LLC谐振变换器的精确控制和交错并联LLC谐振变换器的均流控制带来了挑战。
在第三代半导体推广应用前，LLC谐振变换器的开关频率普遍偏低，为了得到变换器运行时的电流信息，通常会对变换器进行每周期5-10次的高频电流采样，以此估算每周期的电流波形；在对电流信息实时性要求不 高的场合，也可以对通过低通滤波电路对高频半波电流进行低通滤波采样，通过采样的低通电流值估算实际波形，但这种方法存在很明显的问题是动态特性差，对电流的采样存在滞后性，会对动态特性要求较高的算法产生负面影响，在变换器工作情况不稳定时影响尤为明显。
【发明内容】
针对现有技术的缺陷和改进需求，本发明提供了一种LLC谐振变换器的电流检测方法及装置，旨在解决现有的高频LLC谐振变换器电流检测方法无法准确实时获取LLC谐振变换器的电流信息的技术问题。
为实现上述目的，按照本发明的一个方面，提供了一种LLC谐振变换器的电流检测方法，包括：
将LLC谐振变换器的谐振电流i r分解为正弦分量和余弦分量叠加的形式后，将LLC谐振变换器的输出电流i d整理为LLC谐振变换器的谐振电流i r和励磁电流i m的表达式i d(t)；
在LLC谐振变换器运行的过程中，在半个谐振周期内任选一个时刻t′对输出电流i d进行一次采样，得到采样电流值i d(t′)，由此得到在时刻t′，谐振电流i r和励磁电流i m的关系；
联立在半个谐振周期的开始时刻，谐振电流i r和励磁电流i m相等的关系，以及在时刻t′，谐振电流i r和励磁电流i m的关系，求解得到谐振电流i r的正弦分量和余弦分量的幅值，代入表达式i d(t)，由此得到LLC谐振变换器的输出电流i d在半个谐振周期所属开关周期内的波形表达式。
本发明将LLC谐振变换器的谐振电流i r分解为正弦分量和余弦分量叠加的形式，使得谐振电流i r的表达式中仅包含正弦分量幅值和余弦分量幅值这两个未知数；将输出电流i d整理为LLC谐振变换器的谐振电流i r和励磁电流i m的表达式i d(t)后，由于励磁电流i m仅与LLC谐振变换器的结构参数和输出电压这些已知参数相关，因此表达式i d(t)中同样只有两个未知数； 由于在半个谐振周期的开始时刻，谐振电流i r和励磁电流i m存在相等的关系，仅需对输出电流i d进行一次采样，便可得到谐振电流i r和励磁电流i m间的在另一个时刻的关系，联立两个关系表达式，即可求出输出电压表达式中的两个未知数，进而得到输出电流i d(t)在相应开关周期内的波形表达式；本发明检测LLC谐振变换器的电流过程无需多次采样，也无需复杂的拟合过程，能够实现对电流的实时、准确检测，提高后续控制算法的动态性能。
进一步地，将LLC谐振变换器的输出电流i d整理为LLC谐振变换器的谐振电流i r和励磁电流i m的表达式i d(t)后，表达式i d(t)为：
i d(t)＝N|i r(t)-i m(t)|
其中，N表示LLC谐振变换器中变压器的初级侧与次级侧的匝数比，t表示时间变量。
在一些可选的实施例中，对输出电流i d进行采样的半个谐振周期，为一个开关周期内的前半个谐振周期。
进一步地，将LLC谐振变换器的谐振电流i r分解为正弦分量和余弦分量叠加的形式后，谐振电流i r的表达式为：
Figure PCTCN2021072339-appb-000001
其中，I r1和I r2分别表示分解后谐振电流的正弦分量和余弦分量的幅值，t r表示LLC谐振变换器的谐振周期，t表示时间变量。
进一步地，LLC谐振变换器的励磁电流i m的表达式为：
Figure PCTCN2021072339-appb-000002
其中，N表示LLC谐振变换器中变压器的初级侧与次级侧的匝数比，V o表示LLC谐振变换器的输出电压，t r表示LLC谐振变换器的谐振周期，L m表示LLC谐振变换其中的变压器励磁电感，t表示时间变量。
在一些可选的实施例中，对输出电流i d进行采样的半个谐振周期，为一 个开关周期内的后半个谐振周期。
进一步地，将LLC谐振变换器的谐振电流i r分解为正弦分量和余弦分量叠加的形式后，谐振电流i r的表达式为：
Figure PCTCN2021072339-appb-000003
其中，I r1和I r2分别表示分解后谐振电流的正弦分量和余弦分量的幅值，t r表示LLC谐振变换器的谐振周期，t表示时间变量。
进一步地，LLC谐振变换器的励磁电流i m的表达式为：
Figure PCTCN2021072339-appb-000004
其中，N表示LLC谐振变换器中变压器的初级侧与次级侧的匝数比，V o表示LLC谐振变换器的输出电压，t r表示LLC谐振变换器的谐振周期，L m表示LLC谐振变换其中的变压器励磁电感，t表示时间变量。
进一步地，本发明提供的LLC谐振变换器的电流检测方法，还包括：
LLC谐振变换器的输出电流i d在半个谐振周期所属开关周期内的波形表达式，计算输出电流i d在对应开关周期内的峰值和/或有效值。
按照本发明的另一个方面，提供了一种LLC谐振变换器的电流检测装置，包括：采样单元和计算单元；
计算单元，用于将LLC谐振变换器的谐振电流i r分解为正弦分量和余弦分量叠加的形式后，将LLC谐振变换器的输出电流i d整理为LLC谐振变换器的谐振电流i r和励磁电流i m的表达式i d(t)；
采样单元，用于在LLC谐振变换器运行的过程中，在半个谐振周期内任选一个时刻t′对输出电流i d进行一次采样，得到采样电流值i d(t′)，由此得到在时刻t′，谐振电流i r和励磁电流i m的关系；
计算单元，还用于联立在半个谐振周期的开始时刻，谐振电流i r和励磁电流i m相等的关系，以及在时刻t′，谐振电流i r和励磁电流i m的关系，求解 得到谐振电流i r的正弦分量和余弦分量的幅值，代入表达式i d(t)，由此得到LLC谐振变换器的输出电流i d在半个谐振周期所属开关周期内的波形表达式。
总体而言，通过本发明所构思的以上技术方案，能够取得以下有益效果：
(1)本发明通过单次采集瞬时电流以及理论分析，能够实时计算LLC变换器高频工作下每个开关周期的实时输出电流情况，提高了LLC变换器控制算法的动态特性和响应速度，有利于LLC谐振变换器在高频工作状态下的精确控制。
(2)本发明仅需要采样速度匹配LLC开关频率的电流采样芯片即可实现对单次瞬时电流的采样并完成电流检测，无需添加复杂采样电路，硬件要求较低，成本低廉。
【附图说明】
图1为现有的LLC谐振变换器的结构示意图；
图2为现有的LLC谐振变换器的开关信号、谐振电流i r、励磁电流i m以及整流电路末端的输出电流i d波形示意图；其中，(a)为LLC谐振变换器的开关信号波形示意图，(b)为LLC谐振变换器的谐振电流i r和励磁电流i m的波形示意图，(c)为LLC谐振变换器的整流电路末端的输出电流i d波形示意图；
图3为本发明实施例提供的LLC谐振变换器的电流检测方法示意图。
【具体实施方式】
为了使本发明的目的、技术方案及优点更加清楚明白，以下结合附图及实施例，对本发明进行进一步详细说明。应当理解，此处所描述的具体实施例仅仅用以解释本发明，并不用于限定本发明。此外，下面所描述的 本发明各个实施方式中所涉及到的技术特征只要彼此之间未构成冲突就可以相互组合。
在本发明中，本发明及附图中的术语“第一”、“第二”等(如果存在)是用于区别类似的对象，而不必用于描述特定的顺序或先后次序。
在详细解释本发明的技术方案之前，先对LLC谐振变换器的结构及其工作原理作如下简要介绍。
LLC谐振变换器的结构如图1所示，LLC谐振变换器的电路结构包括：输入滤波电容C i、由四个开关管(Q 1Q 2Q 3Q 4)组成的逆变桥、谐振电感L r、谐振电容C r、变压器T、由四个二极管(D 1D 2D 3D 4)组成的整流电路以及输出滤波电容C o；在整流电路的末端(例如图1中所示的采样点S)即为LLC谐振变换器的输出电流i d。
LLC谐振变换器的一个开关周期的持续时间为t s＝2t 2，LLC谐振变换器的谐振周期为t r＝2t 1，在以下实施例中，LLC谐振变换器均工作在t s>t r的工作区间；其中，谐振周期t r的计算公式具体为
Figure PCTCN2021072339-appb-000005
向图1所示的LLC谐振变换器中注入驱动电流后，该LLC谐振变换器开始运行，运行过程中，开关信号、谐振电流i r、励磁电流i m以及整流电路末端的输出电流i d波形示意图如图2所示。
如图2中的(a)所示，在t 0时刻，即一个开关周期的开始时刻(前半个谐振周期的开始时刻)，开关管Q 1、Q 4开通，由于开通前的谐振电流i r小于0，Q 1、Q 4处于反向导通续流状态，因此Q 1、Q 4两端电压处于箝位状态，使Q 1、Q 4在t 0时刻可以零电压开通(zero-voltage-switching，ZVS)，谐振电流i r流经Q 1、Q 4，L r和C r开始谐振，变压器由于被次级侧箝位，励磁电流i m近似线性上升，变压器次级侧电压方向为上正下负，电流流经整流二极管D 1、D 4为负载供能。
如图2中的(b)所示，t 1时刻，即前半个谐振周期末，谐振电流i r与 励磁电流i m大小相等，因此变压器初级侧和次级侧的能量交换断开，次级侧电流迅速下降为0，然后整流二极管D 1、D 4实现零电流关断，次级侧电流i o＝0。由于整流电路的关断，对变压器原边的箝位消除，此时变压器励磁电感L m与谐振电感L r一起和谐振电容C r产生谐振，由于变压器励磁电感L m远大于谐振电感L r，因此这三者谐振的角速度ω r远小于t 0-t 1时间段的谐振角速度，因此此时的谐振电流i r与励磁电流i m近似不变。
针对现有的LLC谐振变换器电流检测方法因需要多次采样并基于采样结果估算各开关周期的电流波形，而无法实现对高频LLC谐振变换器电流的准确、实时检测的问题，本发明提供了一种LLC谐振变换器的电流检测方法及装置，其整体思路在于，基于LLC谐振变换器的工作原理，通过理论推导的方式对LLC谐振变换器的输出电流表达式进行变换，使得仅需一次电流采样，便可结合LLC谐振变换器中的已知条件求解出LLC谐振变换器的输出电流在各开关周期的电流波形。
基于上述思路，本发明基于LLC谐振变换器的工作原理作出如下推导：
以u C和u L分别表示谐振电容C r和谐振电感L r的电压，以I 1,ini和V 1,ini表示t 0时刻的谐振电流i r和电压u C的初始值，即
Figure PCTCN2021072339-appb-000006
因为
Figure PCTCN2021072339-appb-000007
得出
Figure PCTCN2021072339-appb-000008
励磁电流
Figure PCTCN2021072339-appb-000009
其中，V i表示LLC谐振变换器的输入电压，V o表示LLC谐振变换器的输出电压，N表示变压器T的初级侧与次级侧的匝数比；
由于在t 0-t 1时间段内，谐振电流i r与励磁电流i m近似不变，由此可知在t 0-t 1时间段内i m(t)＝i r(t)＝i m(t 1)＝i r(t 1)，而如图2中的(b)所示，t 3-t 4时间段内(即后半个谐振周期内)各波形变化与t 0-t 1时间段大小相同方向相反，即i m(t 3)＝i r(t 3)＝i m(t 0)＝i r(t 0)＝-I 1,ini，即
Figure PCTCN2021072339-appb-000010
基于以上分析，可以计算得到，在t 0-t 1时间段内，励磁电流
Figure PCTCN2021072339-appb-000011
根据该表达式可知，在t 0-t 1的时间段内，励磁电流仅与LLC谐振变换器的结构参数和输出电压这些已知参数相关；
设
Figure PCTCN2021072339-appb-000012
LLC谐振变换器的输出电流为i d(t)＝N|i r(t)-i m(t)|，由于t 0时刻谐振电流等于励磁电流，所以i r(t 0)＝i m(t 0)；在t 0-t 1时间段内任意时刻t′对输出电流i d(t)进行采样，得到t′时刻采样电流值i d(t′)＝N|i r(t′)-i m(t′)|；
两式联立得计算出
Figure PCTCN2021072339-appb-000013
中两个变量I r1和I r2，由此可以计算出i d(t)在这个开关周期的波形表达式，推导出LLC谐振变换器在这个周期的瞬时负载。
t 3-t 4时间段内(即后半个谐振周期内)，励磁电流i m(t)和谐振电流i r(t)的波形变化与t 0-t 1时间段大小相同方向相反，如图2中的(c)所示，t 3-t 4时间段内，输出电流i d(t)的波形变化与t 0-t 1时间段相同，因此，在t 3-t 4时间段内
Figure PCTCN2021072339-appb-000014
i d(t)＝N|i r(t)-i m(t)|；同样地，在t 3时刻，i r(t 3)＝i m(t 3)，在t 3-t 4时间段内任意时刻t′对输出电流i d(t)进行采样，得到t′时刻采样电流值i d(t′)＝N|i r(t′)-i m(t′)|；两式联立，可计算出两个变量I r1和I r2，由此可以计算出i d(t)在这个开关周期的波形表达式。
以下为实施例。
实施例一：
一种LLC谐振变换器的电流检测方法，如图3所示，包括：
将LLC谐振变换器的谐振电流i r分解为正弦分量和余弦分量叠加的形式后，将LLC谐振变换器的输出电流i d整理为LLC谐振变换器的谐振电流i r和励磁电流i m的表达式i d(t)；
在LLC谐振变换器运行的过程中，在半个谐振周期内任选一个时刻t′对输出电流i d进行一次采样，得到采样电流值i d(t′)，由此得到在时刻t′，谐振电流i r和励磁电流i m的关系；
联立在半个谐振周期的开始时刻，谐振电流i r和励磁电流i m相等的关系，以及在时刻t′，谐振电流i r和励磁电流i m的关系，求解得到谐振电流i r的正弦分量和余弦分量的幅值，代入表达式i d(t)，由此得到LLC谐振变换器中整流电路末端的输出电流i d在半个谐振周期所属开关周期内的波形表达式；
在本实施例中，对输出电流进行采样的半个谐振周期为一个开关周期内的前半个谐振周期，即图2中所示的t 0-t 1时间段，电流采样点为LLC谐振变换器的整流电路末端，即图1中的电流采样点S；
本实施例中，
Figure PCTCN2021072339-appb-000015
联立
Figure PCTCN2021072339-appb-000016
求解得到谐振电流i r的正弦分量和余弦分量的幅值I r1和I r2，代入表达式i d(t)，得到LLC谐振变换器的输出电流在一个开关周期内的波形表达式 为
Figure PCTCN2021072339-appb-000017
基于LLC谐振变换器的输出电流在一个开关周期内的波形表达式，可推导出LLC谐振变换器在这个周期的瞬时负载；
作为一种可选的实施方式，本实施例进一步包括：
根据LLC谐振变换器中整流电路末端的输出电流i d在半个谐振周期所属开关周期内的波形表达式，计算输出电流i d在对应开关周期内的峰值和/或有效值。
总体而言，本实施例通过单次采集瞬时电流以及理论分析，能够实时计算LLC变换器高频工作下每个开关周期的实时输出电流情况，提高了LLC变换器控制算法的动态特性和响应速度，有利于LLC谐振变换器在高频工作状态下的精确控制。
实施例二：
一种LLC谐振变换器的电流检测方法，本实施例与上述实施例一类似，不同之处在于，本实施例中，对输出电流进行采样的半个谐振周期为一个开关周期内的后半个谐振周期，即图2中所示的t 3-t 4时间段；
本实施例中，
Figure PCTCN2021072339-appb-000018
联立
Figure PCTCN2021072339-appb-000019
求解得到谐振电流i r的正弦分量和余弦分量的幅值I r1和I r2，代入表达 式i d(t)，得到LLC谐振变换器的输出电流在一个开关周期内的波形表达式为
Figure PCTCN2021072339-appb-000020
基于LLC谐振变换器的输出电流在一个开关周期内的波形表达式，可推导出LLC谐振变换器在这个周期的瞬时负载。
实施例三：
一种LLC谐振变换器的电流检测装置，包括：采样单元和计算单元；
计算单元，用于将LLC谐振变换器的谐振电流i r分解为正弦分量和余弦分量叠加的形式后，将LLC谐振变换器的输出电流i d整理为LLC谐振变换器的谐振电流i r和励磁电流i m的表达式i d(t)；
采样单元，用于在LLC谐振变换器运行的过程中，在半个谐振周期内任选一个时刻t′对输出电流i d进行一次采样，得到采样电流值i d(t′)，由此得到在时刻t′，谐振电流i r和励磁电流i m的关系；采样单元可为采样速度匹配开关频率的电流采样芯片；
计算单元，还用于联立在半个谐振周期的开始时刻，谐振电流i r和励磁电流i m相等的关系，以及在时刻t′，谐振电流i r和励磁电流i m的关系，求解得到谐振电流i r的正弦分量和余弦分量的幅值，代入表达式i d(t)，由此得到LLC谐振变换器中整流电路末端的输出电流i d在半个谐振周期所属开关周期内的波形表达式；
本实施例中，各模块的具体实施方式，请参考上述方法实施例中的描述，在此将不作复述。
本领域的技术人员容易理解，以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内所作的任何修改、等同替换和改进等，均应包含在本发明的保护范围之内。

Claims (10)

  1. 一种LLC谐振变换器的电流检测方法，其特征在于，包括：
    将所述LLC谐振变换器的谐振电流i r分解为正弦分量和余弦分量叠加的形式后，将所述LLC谐振变换器的输出电流i d整理为所述LLC谐振变换器的谐振电流i r和励磁电流i m的表达式i d(t)；在所述LLC谐振变换器运行的过程中，在半个谐振周期内任选一个时刻t′对所述输出电流i d进行一次采样，得到采样电流值i d(t′)，由此得到在所述时刻t′，所述谐振电流i r和所述励磁电流i m的关系；
    联立在所述半个谐振周期的开始时刻，所述谐振电流i r和所述励磁电流i m相等的关系，以及在所述时刻t′，所述谐振电流i r和所述励磁电流i m的关系，求解得到所述谐振电流i r的正弦分量和余弦分量的幅值，代入所述表达式i d(t)，由此得到所述LLC谐振变换器的输出电流i d在所述半个谐振周期所属开关周期内的波形表达式。
  2. 如权利要求1所述的LLC谐振变换器的电流检测方法，其特征在于，将所述LLC谐振变换器的输出电流i d整理为所述LLC谐振变换器的谐振电流i r和励磁电流i m的表达式i d(t)后，所述表达式i d(t)为：
    i d(t)＝N|i r(t)-i m(t)|
    其中，N表示所述LLC谐振变换器中变压器的初级侧与次级侧的匝数比，t表示时间变量。
  3. 如权利要求1或2所述的LLC谐振变换器的电流检测方法，其特征在于，对所述输出电流i d进行采样的半个谐振周期，为一个开关周期内的前半个谐振周期。
  4. 如权利要求3所述的LLC谐振变换器的电流检测方法，其特征在于，将所述LLC谐振变换器的谐振电流i r分解为正弦分量和余弦分量叠加的形式后，所述谐振电流i r的表达式为：
    Figure PCTCN2021072339-appb-100001
    其中，I r1和I r2分别表示分解后所述谐振电流的正弦分量和余弦分量的幅值，t r表示所述LLC谐振变换器的谐振周期，t表示时间变量。
  5. 如权利要求3所述的LLC谐振变换器的电流检测方法，其特征在于，所述LLC谐振变换器的励磁电流i m的表达式为：
    Figure PCTCN2021072339-appb-100002
    其中，N表示所述LLC谐振变换器中变压器的初级侧与次级侧的匝数比，V o表示所述LLC谐振变换器的输出电压，t r表示所述LLC谐振变换器的谐振周期，L m表示所述LLC谐振变换其中的变压器励磁电感，t表示时间变量。
  6. 如权利要求1或2所述的LLC谐振变换器的电流检测方法，其特征在于，对所述输出电流i d进行采样的半个谐振周期，为一个开关周期内的后半个谐振周期。
  7. 如权利要求6所述的LLC谐振变换器的电流检测方法，其特征在于，将所述LLC谐振变换器的谐振电流i r分解为正弦分量和余弦分量叠加的形式后，所述谐振电流i r的表达式为：
    Figure PCTCN2021072339-appb-100003
    其中，I r1和I r2分别表示分解后所述谐振电流的正弦分量和余弦分量的幅值，t r表示所述LLC谐振变换器的谐振周期，t表示时间变量。
  8. 如权利要求6所述的LLC谐振变换器的电流检测方法，其特征在于，所述LLC谐振变换器的励磁电流i m的表达式为：
    Figure PCTCN2021072339-appb-100004
    其中，N表示所述LLC谐振变换器中变压器的初级侧与次级侧的匝数 比，V o表示所述LLC谐振变换器的输出电压，t r表示所述LLC谐振变换器的谐振周期，L m表示所述LLC谐振变换其中的变压器励磁电感，t表示时间变量。
  9. 如权利要求1或2所述的LLC谐振变换器的电流检测方法，其特征在于，还包括：
    所述LLC谐振变换器的输出电流i d在所述半个谐振周期所属开关周期内的波形表达式，计算所述输出电流i d在对应开关周期内的峰值和/或有效值。
  10. 一种LLC谐振变换器的电流检测装置，其特征在于，包括：采样单元和计算单元；
    所述计算单元，用于将所述LLC谐振变换器的谐振电流i r分解为正弦分量和余弦分量叠加的形式后，将所述LLC谐振变换器的输出电流i d整理为所述LLC谐振变换器的谐振电流i r和励磁电流i m的表达式i d(t)；
    所述采样单元，用于在所述LLC谐振变换器运行的过程中，在半个谐振周期内任选一个时刻t′对所述输出电流i d进行一次采样，得到采样电流值i d(t′)，由此得到在所述时刻t′，所述谐振电流i r和所述励磁电流i m的关系；
    所述计算单元，还用于联立在所述半个谐振周期的开始时刻，所述谐振电流i r和所述励磁电流i m相等的关系，以及在所述时刻t′，所述谐振电流i r和所述励磁电流i m的关系，求解得到所述谐振电流i r的正弦分量和余弦分量的幅值，代入所述表达式i d(t)，由此得到所述LLC谐振变换器的输出电流i d在所述半个谐振周期所属开关周期内的波形表达式。
PCT/CN2021/072339 2020-07-20 2021-01-16 一种llc谐振变换器的电流检测方法及装置 WO2022016835A1 (zh)

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