短路功率偏高有什么好方法解決
用3842作電源時常碰到一個問題,短路功率偏高,加大初級電流偵測電阻,常導(dǎo)致line線性不好,加大供電繞組的限流電阻又經(jīng)常不能啟動,跟變壓器供電繞組也有關(guān)系,諸位大蝦有什么高招.
下面是我從實踐中總結(jié)的一些方法,不知道對不對,只想想拋磚引玉的作用,敬請各位同仁批評指正
1.初級供電繞組的限流電阻可調(diào)大,但要保証空載啟動正常
2.初級供電繞組的整流二極管上可加一個磁珠
3.如果用超快的二極管(如uf1002~uf1007),可改成PR1507
或1N4007,即開關(guān)速度慢一點,但要注意空載功耗會大一些
4.繞變壓時初級供電繞組可放在最外層
5.PIN3上拉一電阻到供電高壓線,在高電壓輸入短路不保護有特效.
6.如果次級整流管上有加有磁珠,不妨取消試試,因加有磁珠后電流的上升斜率會變小;但要注意會不會導(dǎo)致輻射裕量不足,噪聲會不會增加
7.增大mosfet下的電流偵測電阻,但要注意滿載的啟動問題
8.初級供電繞組的整流二極管后不用限流電阻,改幾十uH的色碼電感,可并一個電阻降低Q值,不致于會振盪
9其實在保證滿載能開機的前提下,減小PIN3接到地的電容也能降低短路輸入功率(YGX)
10.對于RCC電路,如果短路電流偏大,實在無計可施時,可增大啟動電阻,你只有保証在正常交流電壓輸入時空載啟動正常就行了.道理很簡單喲
短路功率偏高有什么好方法解決
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@小林
我認為短路時與電流上長斜率有關(guān)大蝦們有何高見,請多多指教
Reduce the hiccup frequency
Increase the current sense resistor can reduce the peak current; increase the start up resistor and the VCC filter capacitor,this method can lower the hiccup frequency,than the RMS current had been reduce.
The voltage feedforward can also help you to compensate the wide range input line voltage, you can sampling the signal from bulk capacitor,use the resistor to divide the bulk voltage to PIN3,then the OPP will balance on high line and low line.
Increase the current sense resistor can reduce the peak current; increase the start up resistor and the VCC filter capacitor,this method can lower the hiccup frequency,than the RMS current had been reduce.
The voltage feedforward can also help you to compensate the wide range input line voltage, you can sampling the signal from bulk capacitor,use the resistor to divide the bulk voltage to PIN3,then the OPP will balance on high line and low line.
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@水乖牛牛
ReducethehiccupfrequencyIncreasethecurrentsenseresistorcanreducethepeakcurrent;increasethestartupresistorandtheVCCfiltercapacitor,thismethodcanlowerthehiccupfrequency,thantheRMScurrenthadbeenreduce. Thevoltagefeedforwardcanalsohelpyoutocompensatethewiderangeinputlinevoltage,youcansamplingthesignalfrombulkcapacitor,usetheresistortodividethebulkvoltagetoPIN3,thentheOPPwillbalanceonhighlineandlowline.
thanks for your information
add a resistor to pin3 from high voltage line, perhaps this will help me .long ago ,i know this resistor will limit OPP power.
but increasing current sense resisor cannot reduce the peak current,the account of peak current comes from the value of x\'f inductance
add a resistor to pin3 from high voltage line, perhaps this will help me .long ago ,i know this resistor will limit OPP power.
but increasing current sense resisor cannot reduce the peak current,the account of peak current comes from the value of x\'f inductance
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@小林
thanksforyourinformationaddaresistortopin3fromhighvoltageline,perhapsthiswillhelpme.longago,iknowthisresistorwilllimitOPPpower.butincreasingcurrentsenseresisorcannotreducethepeakcurrent,theaccountofpeakcurrentcomesfromthevalueofx\'finductance
OPP with the primary inductance
Sure the primary inductance can effect the total power, but it will also effect on the efficiency,the limit on pin3 is about 1V,so increase the sense resistor or lower the primary inductance will have the same effect on this voltage, do you think so?
The another mothod to limit the OPP is add the minus slope compensation.
Any way, the voltage on pin3 higher, the OPP lower.
Sure the primary inductance can effect the total power, but it will also effect on the efficiency,the limit on pin3 is about 1V,so increase the sense resistor or lower the primary inductance will have the same effect on this voltage, do you think so?
The another mothod to limit the OPP is add the minus slope compensation.
Any way, the voltage on pin3 higher, the OPP lower.
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方法如下(如有其它方法可行,將會更新,與大家一起進步,下列方法有時只需一個即可)
1.初級供電繞組的限流電阻可調(diào)大,但要保証空載啟動正常
2.初級供電繞組的整流二極管上可加一個磁珠
3.如果用超快的二極管(如uf1002~uf1007),可改成PR1507
或1N4007,即開關(guān)速度慢一點,但要注意空載功耗會大一些
4.繞變壓時初級供電繞組可放在最外層
5.PIN3上拉一電阻到供電高壓線,在高電壓輸入短路不保護有特效.
6.如果次級整流管上有加有磁珠,不妨取消試試,因加有磁珠后電流的上升斜率會變小;但要注意會不會導(dǎo)致輻射裕量不足,噪聲會不會增加
7.增大mosfet下的電流偵測電阻,但要注意滿載的啟動問題
1.初級供電繞組的限流電阻可調(diào)大,但要保証空載啟動正常
2.初級供電繞組的整流二極管上可加一個磁珠
3.如果用超快的二極管(如uf1002~uf1007),可改成PR1507
或1N4007,即開關(guān)速度慢一點,但要注意空載功耗會大一些
4.繞變壓時初級供電繞組可放在最外層
5.PIN3上拉一電阻到供電高壓線,在高電壓輸入短路不保護有特效.
6.如果次級整流管上有加有磁珠,不妨取消試試,因加有磁珠后電流的上升斜率會變小;但要注意會不會導(dǎo)致輻射裕量不足,噪聲會不會增加
7.增大mosfet下的電流偵測電阻,但要注意滿載的啟動問題
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@小林
方法如下(如有其它方法可行,將會更新,與大家一起進步,下列方法有時只需一個即可)1.初級供電繞組的限流電阻可調(diào)大,但要保証空載啟動正常2.初級供電繞組的整流二極管上可加一個磁珠3.如果用超快的二極管(如uf1002~uf1007),可改成PR1507 或1N4007,即開關(guān)速度慢一點,但要注意空載功耗會大一些4.繞變壓時初級供電繞組可放在最外層5.PIN3上拉一電阻到供電高壓線,在高電壓輸入短路不保護有特效.6.如果次級整流管上有加有磁珠,不妨取消試試,因加有磁珠后電流的上升斜率會變小;但要注意會不會導(dǎo)致輻射裕量不足,噪聲會不會增加7.增大mosfet下的電流偵測電阻,但要注意滿載的啟動問題
都不對
!!!!!!!!!
!!!!!!!!!
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@水乖牛牛
OPPwiththeprimaryinductanceSuretheprimaryinductancecaneffectthetotalpower,butitwillalsoeffectontheefficiency,thelimitonpin3isabout1V,soincreasethesenseresistororlowertheprimaryinductancewillhavethesameeffectonthisvoltage,doyouthinkso?TheanothermothodtolimittheOPPisaddtheminusslopecompensation.Anyway,thevoltageonpin3higher,theOPPlower.
i agree to your idea.
!
!
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@小林
thanksforyourinformationaddaresistortopin3fromhighvoltageline,perhapsthiswillhelpme.longago,iknowthisresistorwilllimitOPPpower.butincreasingcurrentsenseresisorcannotreducethepeakcurrent,theaccountofpeakcurrentcomesfromthevalueofx\'finductance
The short circuit is protected by total power
The short circuit is protected by total power,the total power is decision not only by the primary inductance but also the sense,voltage feedforward compensation,and the minus slope compensation and so on.if the voltage at pin3 reach its turn off voltage, the PWM will turn off,so all this method can limit the peak current of short.do you think so?
The short circuit is protected by total power,the total power is decision not only by the primary inductance but also the sense,voltage feedforward compensation,and the minus slope compensation and so on.if the voltage at pin3 reach its turn off voltage, the PWM will turn off,so all this method can limit the peak current of short.do you think so?
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