電源做到現(xiàn)在一直沒徹底搞明白連續(xù)和斷續(xù)的定義和區(qū)別,有時(shí)候常張冠李戴.汗~!
先開個(gè)話題請(qǐng)大家賜教,我去找?guī)讖垐D來看看我的理解對(duì)不對(duì).
討論開關(guān)電源的“連續(xù)”、“斷續(xù)”工作模式的區(qū)別
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@bxgpu
我理解是次級(jí)線圈的電勢(shì)有否持續(xù)一點(diǎn)時(shí)間為0,為0就是不連續(xù)的工作模式.
DCM:discontinuous current mode,電流斷續(xù)模式
CCM:continuous current mode,電流連續(xù)模式
500) {this.resized=true; this.width=500; this.alt='這是一張縮略圖，點(diǎn)擊可放大。\n按住CTRL，滾動(dòng)鼠標(biāo)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(duì)不?
CCM:continuous current mode,電流連續(xù)模式
500) {this.resized=true; this.width=500; this.alt='這是一張縮略圖，點(diǎn)擊可放大。\n按住CTRL，滾動(dòng)鼠標(biāo)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(duì)不?
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@fimo
DCM:discontinuouscurrentmode,電流斷續(xù)模式CCM:continuouscurrentmode,電流連續(xù)模式[圖片]500){this.resized=true;this.width=500;this.alt='這是一張縮略圖，點(diǎn)擊可放大。\n按住CTRL，滾動(dòng)鼠標(biāo)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(duì)不?
能從開關(guān)電壓波形分別出DCM,CCM么?
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@小力神杯
當(dāng)然可以,自己去測(cè)波形.很多時(shí)候要根據(jù)波形來優(yōu)化變壓器地.
請(qǐng)問電流波形對(duì)應(yīng)的電壓波形對(duì)么?
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500) {this.resized=true; this.width=500; this.alt='這是一張縮略圖，點(diǎn)擊可放大。\n按住CTRL，滾動(dòng)鼠標(biāo)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/40/1146384350.gif');}" onmousewheel="return imgzoom(this);"> 0
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@fimo
請(qǐng)問電流波形對(duì)應(yīng)的電壓波形對(duì)么?[圖片]500){this.resized=true;this.width=500;this.alt='這是一張縮略圖，點(diǎn)擊可放大。\n按住CTRL，滾動(dòng)鼠標(biāo)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(qǐng)問電流波形對(duì)應(yīng)的電壓波形對(duì)么?[圖片]500){this.resized=true;this.width=500;this.alt='這是一張縮略圖，點(diǎn)擊可放大。\n按住CTRL，滾動(dòng)鼠標(biāo)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(gè)電流波形指的是初級(jí)還是次級(jí)?
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@fimo
DCM:discontinuouscurrentmode,電流斷續(xù)模式CCM:continuouscurrentmode,電流連續(xù)模式[圖片]500){this.resized=true;this.width=500;this.alt='這是一張縮略圖，點(diǎn)擊可放大。\n按住CTRL，滾動(dòng)鼠標(biāo)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(duì)不?
同樣功率CCM的變壓器體積比DCM的大,因?yàn)镃CM要儲(chǔ)能!
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@rhett
同樣功率CCM的變壓器體積比DCM的大,因?yàn)镃CM要儲(chǔ)能!
這句話我怎么看都是有點(diǎn)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(xù)與非連續(xù)應(yīng)該只取決于L值的大小吧.
在FLYBACK變壓器設(shè)計(jì)中,
根據(jù)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(cè)的最大電流I1max也就確定了.
則,DCM or CCM 則由一次側(cè)電感來決定.
所以,這句話應(yīng)該反過來講
P=1/2*L*I平方*T
在流過L的電流相同的情況下,連續(xù)與非連續(xù)應(yīng)該只取決于L值的大小吧.
在FLYBACK變壓器設(shè)計(jì)中,
根據(jù)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(cè)的最大電流I1max也就確定了.
則,DCM or CCM 則由一次側(cè)電感來決定.
所以,這句話應(yīng)該反過來講
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@斯文敗類
這句話我怎么看都是有點(diǎn)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(xù)與非連續(xù)應(yīng)該只取決于L值的大小吧.在FLYBACK變壓器設(shè)計(jì)中,根據(jù)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(cè)的最大電流I1max也就確定了.則,DCMorCCM則由一次側(cè)電感來決定.所以,這句話應(yīng)該反過來講
則在輸出功率相同的情況下,一次側(cè)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(tài)值不是平均值!
從能量傳遞的角度來看
DCM=Pout,CCM=Pout+儲(chǔ)存的能量.你說哪一個(gè)變壓器會(huì)大一些?
從能量傳遞的角度來看
DCM=Pout,CCM=Pout+儲(chǔ)存的能量.你說哪一個(gè)變壓器會(huì)大一些?
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@rhett
則在輸出功率相同的情況下,一次側(cè)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(tài)值不是平均值!從能量傳遞的角度來看DCM=Pout,CCM=Pout+儲(chǔ)存的能量.你說哪一個(gè)變壓器會(huì)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(diǎn)我不太認(rèn)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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