關(guān)于反激電源的輸出濾波容的選取有公式:(5Ts)/(8K%R),其中
Ts為開關(guān)周期,K為Uopp/Uo,R為負(fù)載.
但是實際選取的總是要大很多,甚至是10倍.而且也有按輸出功率選的.
請問高手們平時是怎么選的?
謝謝!!!!!!!
關(guān)于輸出濾波容的選取,斑竹請進(jìn)
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@sunxj_007
ESR*Co=常數(shù),Co=常數(shù)*0.2*Io/Vor
你這個公式有經(jīng)驗的成分在里面.所謂的0.2×Io其實應(yīng)該是反激電源輸出整流二極管上的電流峰值.很明顯他是與輸出電流,占空比等有關(guān)的,并不是一個簡單的0.2可以代替的.
同時電壓紋波不僅表現(xiàn)為等效串聯(lián)電阻上,同時也表現(xiàn)在電容上,因為電容上的電壓是流過電流的一個積分.考慮最壞的情況是把他們相加.
如果不考慮電流有效值的問題,其實算出來的電容值再乘以一個2就差不多了,因該沒有必要放大那么多倍數(shù)吧?
以上是我個人的一些淺見,還請大家砸磚.
同時電壓紋波不僅表現(xiàn)為等效串聯(lián)電阻上,同時也表現(xiàn)在電容上,因為電容上的電壓是流過電流的一個積分.考慮最壞的情況是把他們相加.
如果不考慮電流有效值的問題,其實算出來的電容值再乘以一個2就差不多了,因該沒有必要放大那么多倍數(shù)吧?
以上是我個人的一些淺見,還請大家砸磚.
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@紅心閃閃
你這個公式有經(jīng)驗的成分在里面.所謂的0.2×Io其實應(yīng)該是反激電源輸出整流二極管上的電流峰值.很明顯他是與輸出電流,占空比等有關(guān)的,并不是一個簡單的0.2可以代替的.同時電壓紋波不僅表現(xiàn)為等效串聯(lián)電阻上,同時也表現(xiàn)在電容上,因為電容上的電壓是流過電流的一個積分.考慮最壞的情況是把他們相加.如果不考慮電流有效值的問題,其實算出來的電容值再乘以一個2就差不多了,因該沒有必要放大那么多倍數(shù)吧?以上是我個人的一些淺見,還請大家砸磚.
確實有經(jīng)驗成分在里面,單從控制紋波來講,你說的計算出來的值*2確實夠了.但是溫度呢?反激式的續(xù)流是靠濾波電容,如此高頻的反復(fù)充放電,溫度肯定不低.呵呵,因為我也是新手,所以只能到這種地步.
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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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