关于反激电源的输出滤波容的选取有公式:(5Ts)/(8K%R),其中
Ts为开关周期,K为Uopp/Uo,R为负载.
但是实际选取的总是要大很多,甚至是10倍.而且也有按输出功率选的.
请问高手们平时是怎么选的?
谢谢!!!!!!!
关于输出滤波容的选取,斑竹请进
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@红心闪闪
你这个公式有经验的成分在里面.所谓的0.2×Io其实应该是反激电源输出整流二极管上的电流峰值.很明显他是与输出电流,占空比等有关的,并不是一个简单的0.2可以代替的.同时电压纹波不仅表现为等效串联电阻上,同时也表现在电容上,因为电容上的电压是流过电流的一个积分.考虑最坏的情况是把他们相加.如果不考虑电流有效值的问题,其实算出来的电容值再乘以一个2就差不多了,因该没有必要放大那么多倍数吧?以上是我个人的一些浅见,还请大家砸砖.
确实有经验成分在里面,单从控制纹波来讲,你说的计算出来的值*2确实够了.但是温度呢?反激式的续流是靠滤波电容,如此高频的反复充放电,温度肯定不低.呵呵,因为我也是新手,所以只能到这种地步.
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How to choose E-cap?
1. Output voltage should be below 80% of E-cap voltage.
2. Ripple current through the E-cap should be within the E-cap specification. Current ripple can be measured or calculated from the circuit.
3. ESR*ripple current = Ripple voltage.
4. two grade of temperature, 85C or 105C. Choose based on cost, size and temperature on teh e-cap.
5. Life time, at 100% ripple current, can measure the case temperature on the e-cap and then use formula from E-cap company to calcultate the life time of the E-cap. Life time should be > warantee time of the power supply.
Hope this could help
1. Output voltage should be below 80% of E-cap voltage.
2. Ripple current through the E-cap should be within the E-cap specification. Current ripple can be measured or calculated from the circuit.
3. ESR*ripple current = Ripple voltage.
4. two grade of temperature, 85C or 105C. Choose based on cost, size and temperature on teh e-cap.
5. Life time, at 100% ripple current, can measure the case temperature on the e-cap and then use formula from E-cap company to calcultate the life time of the E-cap. Life time should be > warantee time of the power supply.
Hope this could help
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@bud_guy
HowtochooseE-cap?1.Outputvoltageshouldbebelow80%ofE-capvoltage.2.RipplecurrentthroughtheE-capshouldbewithintheE-capspecification. Currentripplecanbemeasuredorcalculatedfromthecircuit.3.ESR*ripplecurrent=Ripplevoltage.4.twogradeoftemperature,85Cor105C. Choosebasedoncost,sizeandtemperatureontehe-cap.5.Lifetime,at100%ripplecurrent,canmeasurethecasetemperatureonthee-capandthenuseformulafromE-capcompanytocalcultatethelifetimeoftheE-cap. Lifetimeshouldbe>waranteetimeofthepowersupply.Hopethiscouldhelp
can you please give me some examples or papers on this.
thanks a lot!!
thanks a lot!!
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@bud_guy
HowtochooseE-cap?1.Outputvoltageshouldbebelow80%ofE-capvoltage.2.RipplecurrentthroughtheE-capshouldbewithintheE-capspecification. Currentripplecanbemeasuredorcalculatedfromthecircuit.3.ESR*ripplecurrent=Ripplevoltage.4.twogradeoftemperature,85Cor105C. Choosebasedoncost,sizeandtemperatureontehe-cap.5.Lifetime,at100%ripplecurrent,canmeasurethecasetemperatureonthee-capandthenuseformulafromE-capcompanytocalcultatethelifetimeoftheE-cap. Lifetimeshouldbe>waranteetimeofthepowersupply.Hopethiscouldhelp
Thank you
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