你先說說看.
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拋磚
我是剛剛接觸開關(guān)電源,關(guān)于PFC技術(shù),想向各位大蝦學(xué)一兩手,雪大俠叫我先說幾句,我就班門弄斧侃幾句,不過我?guī)е摽鴣淼?各位有板磚只管砸.
AC/DC電路對(duì)電網(wǎng)的危害及提高功率因數(shù)的意義很多書上都有,我就不多說了.
說幾點(diǎn)我的思路
從根本上說PFC是要開關(guān)電源的輸入電流與輸入電壓同頻同相.可否這樣:
1．釜底抽薪
對(duì)整流電路而言,是要得到一個(gè)較為平直的直流電壓供后級(jí)開關(guān)電路用.也正因?yàn)槿绱瞬旁斐闪藢?duì)電網(wǎng)的污染,去掉濾波電容,也就沒污染的問題.設(shè)計(jì)應(yīng)用脈動(dòng)直流的開關(guān)電路,從根本上解決問題.
2．隨波逐流
   逐流技術(shù)在電子鎮(zhèn)流器上應(yīng)用很多.可否改進(jìn)后應(yīng)用于開關(guān)電源電路.
3．李代桃僵
   有源功率因數(shù)校正技術(shù)具有輸入電壓寬,輸出電壓恒定,干脆解決隔離問題就用有源功率因數(shù)校正電路做降壓電路.
4．以一當(dāng)十
   單級(jí)PFC技術(shù)對(duì)泵電源電路進(jìn)行深入研究

請(qǐng)教一個(gè)問題
請(qǐng)教一個(gè)問題
我在做一款pfc時(shí),低壓PF值0.98左右.高壓時(shí)PF值就掉了很多,0.7,0.8左右.
電流模式為臨界連續(xù)模式,pfc IC L6561.請(qǐng)問該從哪些地方入手?

高壓會(huì)下降我也遇到過這中情況
只是我們?cè)跍y(cè)試時(shí),是在額定的電壓下測(cè)試的

PFC
What bulk voltage you set? I didn\'t meet your question, just now, I design a 240W power used L6561, and what is the feedback compensation value?

two stage
pfc+flyback(100W)
two indepdent control ic.
bulk voltage is about 400Volts.
when load 2.5A, the value of PF is 0.98(110Vac)
but load at 4A,pf drops to 0.88.
can you explain it?

PFC problem
Did you check the bulk voltage and the waveform current sense? I thought the current waveform maybe be distorted, and you need to checvk the input cap of EMI filter after bridge diode (mylar cap), if it is too smaller, will cause this problem, it should be enough. and you need to check Multiplier Characteristics, you can get these information from the application note.

EMI Filter cause PF drops
At high line input, the reactive current through EMI filter will be relatively higher than low line input. So, the PF drops at high line.

CONDUCTION ANGEL and slope compensation
這兩個(gè)概念是怎么回事?請(qǐng)大牛解釋下

An other reason
If u use the capacitor in parallel with the PFC rectifier, or the Trr is very large, will also cause the same problem.

檢查Isence電阻是否太小,對(duì)高壓時(shí)電流信號(hào)不足
檢查Isence電阻是否太小,對(duì)高壓時(shí)電流信號(hào)不足

264V輸入PF到0.7X就不正常了
我一般在264V時(shí)候都由0.91以上,低電壓時(shí)都是1~

你看看前面的派形濾波電容是不是太大了

要不就是你本身PFC電路的問題了

幾點(diǎn)看法
另外,L6561 誤差放大器反饋網(wǎng)絡(luò)是否有足夠的帶寬,在寬范圍電壓輸入的時(shí)候,更確切的說在HIGH LINE的時(shí)候誤差放大器是否工作的線性范圍內(nèi).

PFC的MOS RDSON是否太大,整流二極管導(dǎo)通壓降是否太大,以至于在LINE電壓過0時(shí)PFC德儲(chǔ)能電感沒有足夠的能量,使得此時(shí)PF值下降.

反饋
你調(diào)整一下1,2腳之間反饋補(bǔ)償電容的值,稍微調(diào)大一些.另外zcd反饋繞組給ic的信號(hào)串有一個(gè)電阻,試著調(diào)整一下這個(gè)阻值也會(huì)有幫助.

我覺得逐流法用在反擊電路里應(yīng)該是個(gè)好方法.不知為什么沒人用
.

逐流電路的本質(zhì)是串聯(lián)輸入并聯(lián)輸出
在改變輸入電流波形的同時(shí),輸出電壓變化很大,對(duì)功率較大電路可能不適合,反激電路常用電荷泵式PFC

是的,我也正調(diào)此電路,電壓89----200V之間,HP為0.999,電壓升到208時(shí)HP變?yōu)?.68,但總功率沒有多大變化,不知調(diào)何處???請(qǐng)樓主回復(fù)一下吧!!!