電源做到現在一直沒徹底搞明白連續和斷續的定義和區別,有時候常張冠李戴.汗~!
先開個話題請大家賜教,我去找幾張圖來看看我的理解對不對.
討論開關電源的“連續”、“斷續”工作模式的區別
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@bxgpu
我理解是次級線圈的電勢有否持續一點時間為0,為0就是不連續的工作模式.
DCM:discontinuous current mode,電流斷續模式
CCM:continuous current mode,電流連續模式
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同樣功率,CCM的峰值電流小,變壓器體積小,EMI小.
對不?
CCM:continuous current mode,電流連續模式
500) {this.resized=true; this.width=500; this.alt='這是一張縮略圖，點擊可放大。\n按住CTRL，滾動鼠標滾輪可自由縮放';this.style.cursor='hand'}" onclick="if(!this.resized) {return true;} else {window.open('http://u.dianyuan.com/bbs/u/40/1146378377.gif');}" onmousewheel="return imgzoom(this);">
同樣功率,CCM的峰值電流小,變壓器體積小,EMI小.
對不?
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@fimo
DCM:discontinuouscurrentmode,電流斷續模式CCM:continuouscurrentmode,電流連續模式[圖片]500){this.resized=true;this.width=500;this.alt='這是一張縮略圖，點擊可放大。\n按住CTRL，滾動鼠標滾輪可自由縮放';this.style.cursor='hand'}"onclick="if(!this.resized){returntrue;}else{window.open('http://u.dianyuan.com/bbs/u/40/1146378377.gif');}"onmousewheel="returnimgzoom(this);">同樣功率,CCM的峰值電流小,變壓器體積小,EMI小.對不?
能從開關電壓波形分別出DCM,CCM么?
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@小力神杯
當然可以,自己去測波形.很多時候要根據波形來優化變壓器地.
請問電流波形對應的電壓波形對么?
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@fimo
請問電流波形對應的電壓波形對么?[圖片]500){this.resized=true;this.width=500;this.alt='這是一張縮略圖，點擊可放大。\n按住CTRL，滾動鼠標滾輪可自由縮放';this.style.cursor='hand'}"onclick="if(!this.resized){returntrue;}else{window.open('http://u.dianyuan.com/bbs/u/40/1146384350.gif');}"onmousewheel="returnimgzoom(this);">
沒人么,頂下.
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@fimo
請問電流波形對應的電壓波形對么?[圖片]500){this.resized=true;this.width=500;this.alt='這是一張縮略圖，點擊可放大。\n按住CTRL，滾動鼠標滾輪可自由縮放';this.style.cursor='hand'}"onclick="if(!this.resized){returntrue;}else{window.open('http://u.dianyuan.com/bbs/u/40/1146384350.gif');}"onmousewheel="returnimgzoom(this);">
這個電流波形指的是初級還是次級?
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@fimo
DCM:discontinuouscurrentmode,電流斷續模式CCM:continuouscurrentmode,電流連續模式[圖片]500){this.resized=true;this.width=500;this.alt='這是一張縮略圖，點擊可放大。\n按住CTRL，滾動鼠標滾輪可自由縮放';this.style.cursor='hand'}"onclick="if(!this.resized){returntrue;}else{window.open('http://u.dianyuan.com/bbs/u/40/1146378377.gif');}"onmousewheel="returnimgzoom(this);">同樣功率,CCM的峰值電流小,變壓器體積小,EMI小.對不?
同樣功率CCM的變壓器體積比DCM的大,因為CCM要儲能!
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@斯文敗類
這句話我怎么看都是有點怪怪的,是不是講反了?還是我理解有誤?P=1/2*L*I平方*T在流過L的電流相同的情況下,連續與非連續應該只取決于L值的大小吧.在FLYBACK變壓器設計中,根據N1/N2*(Vo/Vin)=D/(1-D)如果Vo、Vin、Dmax都確定,則匝比N=N2/N1也就確定了.則在輸出功率相同的情況下,一次側的最大電流I1max也就確定了.則,DCMorCCM則由一次側電感來決定.所以,這句話應該反過來講
則在輸出功率相同的情況下,一次側的最大電流I1max也就確定了.這句話有問題,公式里的電流是瞬態值不是平均值!
從能量傳遞的角度來看
DCM=Pout,CCM=Pout+儲存的能量.你說哪一個變壓器會大一些?
從能量傳遞的角度來看
DCM=Pout,CCM=Pout+儲存的能量.你說哪一個變壓器會大一些?
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@rhett
則在輸出功率相同的情況下,一次側的最大電流I1max也就確定了.這句話有問題,公式里的電流是瞬態值不是平均值!從能量傳遞的角度來看DCM=Pout,CCM=Pout+儲存的能量.你說哪一個變壓器會大一些?
本來我記得是ccm變壓器體積大,最近看了SG6848的application note,里面有這么一段,大哥s看看.
There are many advantages to operating the converter in CCM. With the same output power, a converter in CCM exhibits smaller peak inductor currents than one in DCM. Therefore, a small-sized transformer and a low-rated MOSFET can be applied. On the secondary side of the transformer, the rms output current of DCM can be up to twice
that of CCM. Larger wire gauge and output capacitors with larger ripple current ratings are required. DCM operation also results in higher output voltage spikes. A large LC filter must also be added. Therefore, a flyback converter in CCM achieves better performance with lower component cost.
There are many advantages to operating the converter in CCM. With the same output power, a converter in CCM exhibits smaller peak inductor currents than one in DCM. Therefore, a small-sized transformer and a low-rated MOSFET can be applied. On the secondary side of the transformer, the rms output current of DCM can be up to twice
that of CCM. Larger wire gauge and output capacitors with larger ripple current ratings are required. DCM operation also results in higher output voltage spikes. A large LC filter must also be added. Therefore, a flyback converter in CCM achieves better performance with lower component cost.
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@fimo
本來我記得是ccm變壓器體積大,最近看了SG6848的applicationnote,里面有這么一段,大哥s看看.TherearemanyadvantagestooperatingtheconverterinCCM.Withthesameoutputpower,aconverterinCCMexhibitssmallerpeakinductorcurrentsthanoneinDCM.Therefore,asmall-sizedtransformerandalow-ratedMOSFETcanbeapplied.Onthesecondarysideofthetransformer,thermsoutputcurrentofDCMcanbeuptotwicethatofCCM.Largerwiregaugeandoutputcapacitorswithlargerripplecurrentratingsarerequired.DCMoperationalsoresultsinhigheroutputvoltagespikes.AlargeLCfiltermustalsobeadded.Therefore,aflybackconverterinCCMachievesbetterperformancewithlowercomponentcost.
兄弟,這里面的觀點我不太認同,你自己可以分析一下,Ipeak小就能推出變壓器小嗎?
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