电源做到现在一直没彻底搞明白连续和断续的定义和区别,有时候常张冠李戴.汗~!
先开个话题请大家赐教,我去找几张图来看看我的理解对不对.
讨论开关电源的“连续”、“断续”工作模式的区别
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@bxgpu
我理解是次级线圈的电势有否持续一点时间为0,为0就是不连续的工作模式.
DCM:discontinuous current mode,电流断续模式
CCM:continuous current mode,电流连续模式
500) {this.resized=true; this.width=500; this.alt='这是一张缩略图，点击可放大。\n按住CTRL，滚动鼠标滚轮可自由缩放';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);">
同样功率,CCM的峰值电流小,变压器体积小,EMI小.
对不?
CCM:continuous current mode,电流连续模式
500) {this.resized=true; this.width=500; this.alt='这是一张缩略图，点击可放大。\n按住CTRL，滚动鼠标滚轮可自由缩放';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);">
同样功率,CCM的峰值电流小,变压器体积小,EMI小.
对不?
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@fimo
DCM:discontinuouscurrentmode,电流断续模式CCM:continuouscurrentmode,电流连续模式[图片]500){this.resized=true;this.width=500;this.alt='这是一张缩略图，点击可放大。\n按住CTRL，滚动鼠标滚轮可自由缩放';this.style.cursor='hand'}"onclick="if(!this.resized){returntrue;}else{window.open('http://u.dianyuan.com/bbs/u/40/1146378377.gif');}"onmousewheel="returnimgzoom(this);">同样功率,CCM的峰值电流小,变压器体积小,EMI小.对不?
能从开关电压波形分别出DCM,CCM么?
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@小力神杯
当然可以,自己去测波形.很多时候要根据波形来优化变压器地.
请问电流波形对应的电压波形对么?
500) {this.resized=true; this.width=500; this.alt='这是一张缩略图，点击可放大。\n按住CTRL，滚动鼠标滚轮可自由缩放';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);">
500) {this.resized=true; this.width=500; this.alt='这是一张缩略图，点击可放大。\n按住CTRL，滚动鼠标滚轮可自由缩放';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
请问电流波形对应的电压波形对么?[图片]500){this.resized=true;this.width=500;this.alt='这是一张缩略图，点击可放大。\n按住CTRL，滚动鼠标滚轮可自由缩放';this.style.cursor='hand'}"onclick="if(!this.resized){returntrue;}else{window.open('http://u.dianyuan.com/bbs/u/40/1146384350.gif');}"onmousewheel="returnimgzoom(this);">
没人么,顶下.
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@fimo
请问电流波形对应的电压波形对么?[图片]500){this.resized=true;this.width=500;this.alt='这是一张缩略图，点击可放大。\n按住CTRL，滚动鼠标滚轮可自由缩放';this.style.cursor='hand'}"onclick="if(!this.resized){returntrue;}else{window.open('http://u.dianyuan.com/bbs/u/40/1146384350.gif');}"onmousewheel="returnimgzoom(this);">
这个电流波形指的是初级还是次级?
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@fimo
DCM:discontinuouscurrentmode,电流断续模式CCM:continuouscurrentmode,电流连续模式[图片]500){this.resized=true;this.width=500;this.alt='这是一张缩略图，点击可放大。\n按住CTRL，滚动鼠标滚轮可自由缩放';this.style.cursor='hand'}"onclick="if(!this.resized){returntrue;}else{window.open('http://u.dianyuan.com/bbs/u/40/1146378377.gif');}"onmousewheel="returnimgzoom(this);">同样功率,CCM的峰值电流小,变压器体积小,EMI小.对不?
同样功率CCM的变压器体积比DCM的大,因为CCM要储能!
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@斯文败类
这句话我怎么看都是有点怪怪的,是不是讲反了?还是我理解有误?P=1/2*L*I平方*T在流过L的电流相同的情况下,连续与非连续应该只取决于L值的大小吧.在FLYBACK变压器设计中,根据N1/N2*(Vo/Vin)=D/(1-D)如果Vo、Vin、Dmax都确定,则匝比N=N2/N1也就确定了.则在输出功率相同的情况下,一次侧的最大电流I1max也就确定了.则,DCMorCCM则由一次侧电感来决定.所以,这句话应该反过来讲
则在输出功率相同的情况下,一次侧的最大电流I1max也就确定了.这句话有问题,公式里的电流是瞬态值不是平均值!
从能量传递的角度来看
DCM=Pout,CCM=Pout+储存的能量.你说哪一个变压器会大一些?
从能量传递的角度来看
DCM=Pout,CCM=Pout+储存的能量.你说哪一个变压器会大一些?
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@rhett
则在输出功率相同的情况下,一次侧的最大电流I1max也就确定了.这句话有问题,公式里的电流是瞬态值不是平均值!从能量传递的角度来看DCM=Pout,CCM=Pout+储存的能量.你说哪一个变压器会大一些?
本来我记得是ccm变压器体积大,最近看了SG6848的application note,里面有这么一段,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
本来我记得是ccm变压器体积大,最近看了SG6848的applicationnote,里面有这么一段,大哥s看看.TherearemanyadvantagestooperatingtheconverterinCCM.Withthesameoutputpower,aconverterinCCMexhibitssmallerpeakinductorcurrentsthanoneinDCM.Therefore,asmall-sizedtransformerandalow-ratedMOSFETcanbeapplied.Onthesecondarysideofthetransformer,thermsoutputcurrentofDCMcanbeuptotwicethatofCCM.Largerwiregaugeandoutputcapacitorswithlargerripplecurrentratingsarerequired.DCMoperationalsoresultsinhigheroutputvoltagespikes.AlargeLCfiltermustalsobeadded.Therefore,aflybackconverterinCCMachievesbetterperformancewithlowercomponentcost.
兄弟,这里面的观点我不太认同,你自己可以分析一下,Ipeak小就能推出变压器小吗?
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