【正文】 When using more transformers with primary windings in series and secondary windings in parallel the leakage inductance asymmetry can be pensated by appropriate secondary windings connection. 副邊漏電感可以造成采用高變壓器匝數(shù)比的應(yīng)用中諧振電感出現(xiàn)顯著的不平衡性。這樣的結(jié)構(gòu)有望可以通過(guò)對(duì)副邊繞組的恰當(dāng)連接，對(duì)變壓器漏電特性的不平衡性形成補(bǔ)償。 Calculate needed ESR value that will assure that the output ripple will be lower than maximum specification 3. 選擇恰當(dāng)?shù)碾娙萜鳎▊儯?yīng)該能承受計(jì)算出的 rms電流，而 ESR應(yīng)當(dāng)與計(jì)算值一致或更低。 The k=Lm/Ls ratio dictates how much energy is stored in the Lm. 更高的 k值將造成磁化電流和變換器增益的降低 Higher k will result in the lower magizing current and gain of the converter. K因數(shù)更高，則所需的調(diào)節(jié)頻率范圍也越大 Needed regulation frequency range is higher for larger k factor. +04 +05 +06 頻率 [Hz] Gain [] k=2 k=4 k=6 k=8 k=10 Gmax Gmin Needed gains band for full load regulation D fk=6 D fk=2 n=8, C s =33nF, L s =100uH, L m =parameter, Rload= W 滿(mǎn)載時(shí)的 Q和 k因數(shù)優(yōu)化 Full Load Q and k Factors Optimization 26 在實(shí)踐中， Ls （集成化的變壓器解決方案中的漏電感）只能在有限的范圍內(nèi)取值，而且由變壓器的構(gòu)造（以滿(mǎn)足所需的功率水平）和匝數(shù)比所決定。于是， LLC諧振回路的諧振頻率在 Fs 和Fmin之間變化。 半橋 LLC諧振轉(zhuǎn)換器的設(shè)計(jì)考慮 Design Considerations for a HalfBridge LLC Resonant Converter 2 議程 Agenda ? 為何采用 HB LLC 變換器 Why an HB LLC converter ? HB LLC變換器和諧振回路的構(gòu)形 Configurations of the HB LLC converter and a resonant tank ? HB LLC的工作狀態(tài) Operating states of the HB LLC ? HB LLC變換器建模和增益特性 HB LLC converter modeling and gain characteristics ? 原邊電流和諧振電容的參數(shù)確定 Primary currents and resonant cap dimensioning ? 副邊整流設(shè)計(jì)和輸出電容參數(shù)的確定 Secondary rectification design and output cap dimensioning ? 諧振電感的平衡性 Resonant inductance balance ? 變壓器繞組參數(shù)的確定和變壓器的制作 Transformer winding dimensioning and transformer construction 3 LCD和等離子體 TV市場(chǎng)逐年增長(zhǎng)。 Z1, Z2 are frequency dependent = LLC converter behaves like frequency dependent divider. The higher load, the Lm gets to be more clamped by Rac. Resonant frequency of LLC resonant tank thus changes between Fs and Fmin. LLC變換器可以通過(guò)一階基波近似來(lái)描述。 Practically, the Ls (. leakage inductance of the integrated transformer version) has only limited range of values and is given by the transformer construction (for needed power level) and turns ratio. Q因數(shù)的計(jì)算由所需要的標(biāo)稱(chēng)工作頻率 fs所給出。 Select appropriate capacitor(s) to handle the calculated rms current and having calculated ESR or lower 4. 考慮價(jià)格、物理尺寸和瞬態(tài)響應(yīng)等因素。 For high power app. it is attractive to connect primary windings in series and secondary windings in parallel. There is possibility to pensate transformer leakage imbalance by appropriate connection of the secondary windings: ?Llk_total = 2* ?Llk ?Llk_total = 0 諧振電感的平衡性 Resonant Inductance Balance 48 副邊漏感被反射到原邊，從而提高了總的諧振電感值。在這種情況下， LLC諧振變換器的副邊的布線就有著關(guān)鍵性影響。 For the transformer with integrated resonant inductance, it has to be checked how the transformer manufacturer specifies the leakage inductance. Specification for all secondary windings shorted is irrelevant. The particular leakage inductance values can differ. 將更多的變壓器組合使用，將其原邊繞組串連起來(lái)并將其副邊繞組并聯(lián)，則通過(guò)恰當(dāng)?shù)母边吚@組連接可以補(bǔ)償漏電感的不對(duì)稱(chēng)性。 Converter works below series resonant frequency Fs for the one half of the switching cycle and in the Fs for the second half of the switching cycle. Iprimary 47 對(duì)于大功率應(yīng)用而言，將原邊繞組串連起來(lái)，并將副邊繞組并聯(lián)起來(lái)，是一種有吸引力分方法。 Calculate peak and rms rectifier and capacitor currents based on Io and Vout 2. 計(jì)算出所需要的 ESR值，該值應(yīng)確保輸出紋波低于最大的性能指標(biāo)。 LLC gain characteristics are degraded to the SRC for very low Q values. +04 +05 +06 頻率 [Hz] Gain [] Q=2 Q=3 Q=4 n=8 , L s /L m =6, Q=parameter, Rload= W Gmin Gmax D fQ=4 D fQ=3 Needed gains band 實(shí)現(xiàn)滿(mǎn)負(fù)載穩(wěn)壓時(shí)所需的增益分布帶 for full load regulation 滿(mǎn)載時(shí)的 Q和 k因數(shù)優(yōu)化 Full Load Q and k Factors Optimization 25 k=Lm/Ls比決定了 Lm 中存儲(chǔ)多少能量。負(fù)載越高，Lm所受到的、由 Rac所產(chǎn)生的嵌位作用就越大。這些市場(chǎng)和其他市場(chǎng)都需要一種具有如下功能特色的 SMPS產(chǎn)品： The LCD and PLASMA TV market is growing each year. These and also other markets call for an SMPS unit that can provide these features: 輸出功率范圍： 150 W～ 600 W Output power from 150 W up to 600 W 寬范圍交流輸入 Universal mains 有源和無(wú)源 PFC（由所需的功率所決定） Active or passive PFC (given by needed power) 寬度和空間有限，無(wú)風(fēng)扇：通風(fēng)條件有限 Limited width and space, no fan: limited air flow 低待機(jī)能耗 Low standby power consumption 消費(fèi)類(lèi)電子市場(chǎng)：殘酷的競(jìng)爭(zhēng) Consumer Electronics market: fierce petition 上述要求能夠通過(guò)一個(gè) SMPS來(lái)實(shí)現(xiàn)，該電路可以提供 ： The above requirements can be fulfilled with an SMPS that provides: → 高功率密度 High power density → 平滑的 EMI特征 Smooth EMI signature → 元件數(shù)量少、成本經(jīng)濟(jì)性好的解決方案 Cost effective solution with minimum ponent count 為何采用 LLC串連諧振變換器？ Why an LLC Series Resonant Converter ? 4 LLC串連諧振變換器的優(yōu)點(diǎn) Benefits of an LLC Series Resonant Converter ? 串連諧振式變換器的類(lèi)型。僅僅是近似 ——精度極為有限！在 Fs處達(dá)到最高精度 LLC converter can be described using firs fundamental approximation. Only approximation – accuracy is limited!! Best accuracy is reached around Fs. 17 在使用基頻近似時(shí)，實(shí)際的負(fù)載電阻必須被修改，因?yàn)閷?shí)際的諧振回路是由電壓方波驅(qū)動(dòng)的 Real load resistance has to be modified when using fundamental approximation because the real resonant tank is driven by square wave voltage. I pI oV oI pV oI a c ( r m s )OR M SacII 22_ ??OR M Sac VV ?22_ ?考慮方波的基頻分量，在RMS電壓是： Considering the fundamental ponent of the square wave, the RMS voltage is: 在全波橋電路中， RMS電流為： In a fullwave bridge circuit the RMS current is: LOOR M SacR M Sacac RIEIVR22__ 88?? ???AC電阻 Rac 可以表示為： The AC resistance Rac can be expressed as: LLC變換器建模 ——等效電路 LLC Converter Modeling – Equivalent Circuit 18 02ZRnQ L??ssCLZ ?0smLLk ?諧振回路方程 Resonant Tank Equations sss LCF ???? ?21)(21m i nmss LLCF??????品質(zhì)因數(shù) Quality factor: 特性阻抗 Characteristic impedance: Lm/Ls 比： Lm/Ls ratio: 最小諧振頻率： Minimum resonant frequency: 串連諧振頻率： Series r