开关电源中的功率因数校正- 安森美厂商_在线座谈

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座谈主题：开关电源中的功率因数校正
在线问答
[问：hwang88]	有源PFC电路工作时带来的辐射干扰如何避免？谢谢！
[答：Kelvin]	first to consider the all switching element whether there is high frequency noise, then to consider sufficient differential mode noise filter.	[2003-5-27 10:35:53]
[问：qiaobw]	在PFC电路中开关管的导通电流的包罗线为正弦波吗？整流后的电容应如何选取，其电压波型如何？在输出功率为1/3额定功率或更小时，供电电流是否仍为与电压同相位的正弦波？目前电磁炉、微波炉不具有PFC电路。
[答：Manson]	The current envelope is sinusoidal. The output cap. needs low ESR., and the output voltage is smoothed dc. The input voltage is in phase with current and sinusoidal at 1/3 rated power.	[2003-5-27 10:44:14]
[问：qsj55@ sohu.com]	大功率（10kW以上)功率因数校正技术的发展趋势！功率因数校正的自身损耗!
[答：TKman]	We are not doing much on such high power applications, however personally, I will say resonant type of PFC solution will dominant.	[2003-5-27 10:44:18]
[问：陈五德]	用MC34262做的一个300W PFC,在上电启动时，会听到电感“吱”一声响，很吓人，然后能启动正常。请问能否消除，是不是加软启动电路有用，该怎么加？
[答：Hector]	The sound during startup is normal. At the initial stage, output bulk capacitor is at low voltage level and slowly build up to 400V. Therefore switching frequency increases from low to high. That is why a sound is generated. For 300W PFC, you can consider to use our new device NCP1650. This is a fixed frequency continuous mode device.	[2003-5-27 10:46:42]
[问：9daisy9]	据我所知，目前单相PFC技术（特别是小功率应用方面）已经达到了比较成熟的地步，很多业内人士都转向三相大功率PFC技术的研究。那么您觉得在单相小功率方面PFC技术还有哪些可能的发展方向？
[答：Eddie]	There are still some area the industry can further develope. Like Single stage PFC + PWM, furtherimprove efficiency and smaller size.	[2003-5-27 10:46:46]
[问：wendy1]	请问安森美的开关电源产品在哪种转换上具有优势？有电子镇流器的相关产品吗？
[答：Manson]	ON Semi. has outstanding switching mode controllers. One of the key feature is very low standby power at no load or low load.ON Semi. has PFC and bipolar transistors for ballast applications.	[2003-5-27 10:47:05]
[问：wang chaoyu]	隔离开关电源中的震荡器、偶合器对功率因数有和影响？设计时应注意什么？
[答：Manson]	This is not related directly. Poor power factor is the result of the spike current through the input bridge rectifiers to bulk capacitor. Use ON Semi."s PFC IC"s, such as NCP1650 to solve the problem.	[2003-5-27 10:50:29]
[问：sdhp]	如何在保证功率因数和EMI正常的前提下，减小输入线圈的体积。
[答：TKman]	It"s a good question, we are always facing some give and take decisions. What we are doing is to try out smaller new transformers by putting back to the application and confrim its performance carefully, of-course, Power factor and EMI are the key parameters.	[2003-5-27 10:51:58]
[问： Anoymous]	能否利用开关电源中的功率因数校正电路解决电源谐波问题？？？
[答：Hector]	Most PFC regulation specify 3rd harmonic requirement. Yes, our PFC devices give good PFC performance and can meet 3rd harmonic regulation.	[2003-5-27 10:55:07]
[问： redshoes]	目前开关电源的输出纹波有很多解决方案，但是，究竟哪种方法或者材料可以将其限制在50mV以内呢？
[答：Eddie]	There are many different way to reduce output ripple.Different case should use different approach. Sincethe application is not specified, followings are somecommon methods to reduce ripple. See which one can solve your issue in cheaper cost and simplier way.1. For high output current application, using forward mode will produce less ripple.2. Normal select a lower ESR output capacitor.3. For low power and efficiency not critical applications, designer can try using a linear post regulator.	[2003-5-27 10:55:36]
[问： sanzi666]	PFC控制芯片和主PWM控制在PCBLAYOUT上应注意些什么才能减小相互之间的干扰。
[答：Manson]	It is not a simple question and answer. The general rule is to keep the current path thick and short.	[2003-5-27 10:56:04]
[问：liuhuiwen @yeah.net]	开关电源中脉冲变压器的设计很关键，脉冲变压器的设计关系到输出电压的稳定与否以及输出电压的质量。请问为了减小脉冲变压器引起的脉动和谐波，该采取那些措施？
[答：TKman]	Transformer design is the #1 important task we need to take care in SMPS, following are some of the keys : 1. Core material selection ; 2. Windings calculation ; 3. Winding structure design ; .............. etc......It"s a big story to tell, please contact our local FAE for more support for your applications.	[2003-5-27 11:00:42]
[问： qanmingx]	请问计算机中的开关电源实际功率与标称功率有何差异，还有输入功率与输出功率怎样测量和计算最准确
[答：Hector]	Usually, actual power capability of a power supply is higher than its stated power. It is because product design should have margin to cater for production variation.To accurately measure input and output power, you need a power meter to measure input power. An electronic load to provide constant and well defined output power.	[2003-5-27 11:02:46]
[问：byinge mail@163.net]	PFC对整机效率有提高吗？
[答：TKman]	No, PFC insert another stage before the PWM circuit, so adding a PFC can introduce additional power loss to the system. What we are doing now is trying to make the PFC circuit as high efficiency as possible in order to minize the power loss of the PFC stage.	[2003-5-27 11:05:12]
[问：sanzi666]	PFC，和主线路在PCBLAYOUT上应该注意什么才能减少干扰，
[答：Manson]	It is not a simple question and answer. The general rule is to keep current path thick and short.	[2003-5-27 11:06:13]
[问：大跳侠]	关于空载电流如何设计处理？
[答：Manson]	Please contact kelvin.tsiang@onsemi.com.	[2003-5-27 11:07:34]
[问：tianjiu]	1、常用的PFC集成电路有UC3852、UC3854、UC3855、ML4803等，不知贵公司有没有性能好的PFC集成电路？2、有没有负电压输入、负电压输出的PFC集成电路？3、我看过贵公司推出的NCP1203型PWM电流型控制器的资料，但在市场上买不到，请问何处可以购买到？4、使用NCP1203设计制作开关电源，最大功率可达到多少？
[答：Kenny]	1. MC33262, MC33260, NCP16512. There"s no negative input, but our NCP1651 has negative output.3. You can contact our local distributor like Arrow, Solomon QCE, WPI.4. 150W.	[2003-5-27 11:08:16]
[问：ywm1217]	就贵公司的MC33262来说,它工作在临界导电模式下,解决了二极管的反向恢复问题,但在半个工频周期内,当输入电压较低时,由于开关频率的增大,必然导致主开关管的损耗增大,是否两者存在矛盾的问题.
[答：Hector]	Good question. This problem is solved by MC33260 and MC33368.MC33368 can limit maximum switching frequency externally.MC33260 has minimum off time to limit maximum switching frequency. One can further control the switching frequency by syn input signal.	[2003-5-27 11:10:39]
[问：tianjiu]	6、NCP1650　PFC控制器的最高工作频率可达到多少（输出功率为3kW）？7、NCP1650交互式设计软件哪里有？
[答：Manson]	NCP1650 max. freq. 250kHz. For design tools, please go to,http://www.onsemi.com/site/products/moreDesign/ 0,4516,NCP1650_495,00.html	[2003-5-27 11:11:40]
[问：ghz]	Ncp1650是否可用于2000w以上的开关电源？
[答：Manson]	Yes, it can.	[2003-5-27 11:12:19]
[问：jason_ chang@ampe ror.com.tw]	How to design the inductor of active PFC?
[答：Manson]	Please refer to the design tool below,http://www.onsemi.com/site/products/moreDesign/ 0,4516,NCP1650_495,00.html	[2003-5-27 11:16:59]
[问：ecnan jing_EBY7E]	我要设计一款100W off-line AC-DCconverter out port -48Vdc,请问采用ONS的什么器件，有无参考方案？
[答：Hector]	You can consider NCP1203. Please contact our sales offices or distributors so that we can give you more support.	[2003-5-27 11:17:21]
[问：pan881 68@cnnb.net]	现在多数电源在60W的时候有的产商已经要求加PFC,PFC电路中的功率因数可以达到0.992~0.998之间,甚至更大到1,但是这个中间有一个问题就是他的频率会伴随电压的变化而变,所以在这个里面应该要考虑什么方面的事项呢?当然还要考虑到EMC!
[答：Eddie]	Suggest to look into following area.1. Frequency not too low to generate audible noise or end up too much current passing thru" the MOSFET and inductor and cause heat up.2. Frequency also not too high causing output rectifier to generate too much heat during switching. Further, too high frequency will cause the EMC work more difficult.	[2003-5-27 11:21:54]
[问：tianjiu]	5、公司的产品代理在哪里？6、NCP1650　PFC控制器的最高工作频率可达到多少（输出功率为3kW）？7、NCP1650交互式设计软件哪里有？
[答：Hector]	Please go to below address for help.Distributor List:http://www.onsemi.com/site/locateSalesSupport/ 0,4505,1133,00.htmlMaximum switching frequency of NCP1650 is 250KHz.NCP1650 design spreadsheet:http://www.onsemi.com/site/products/moreDesign/ 0,4516,NCP1650_495,00.html	[2003-5-27 11:23:24]
[问：bridge70]	请问有无ON SEMI 在250~400W电子镇流器应用的产品？
[答：Kelvin]	no..	[2003-5-27 11:25:26]
[问：deyun]	开关电源功率因数校正部分成本约占变换部分（简单的半桥）的比例是多少？
[答：Eddie]	This can vary a lot due to different approach. Normally35% - 45% of the whole power supply cost.	[2003-5-27 11:27:29]
[问： Anoymous]	请问专家对于开关电源产生的干扰有没有好的抑制方法？
[答：TKman]	Interference can be grouped to two classes, 1. emission - it comes from fast transients of voltage and current at switching nodes, carefull design of PCB, careful adjustment of the switching elements can help and also proper shielding of magnetic components is important ;2. conduct - it comes from the switching distrubance and passed to the power line via conduction. Handling this is a complex question, usually proper filters are required in place. For more in-depth support, please contact our local FAE. complex	[2003-5-27 11:29:24]
[问：kptzzy]	2000W PFC 纹波电压太大如何解决？
[答：Eddie]	1. Try to use a continuous mode IC.2. Increase the PFC bulk cap size. Also, ensure the PFC bulk cap is a low ESR cap.3. Check whether switching freq is too low.	[2003-5-27 11:30:30]
[问：tomhny @163.com]	有源PFC的工作环境要求是什么？可以承受恶劣环境的考验吗？
[答：Hector]	I don"t know how you define adverse environment. Please contact our technical staff for further discussion.	[2003-5-27 11:30:47]
[问：oxiong]	1、对于不同的输出功率如900瓦，2000瓦，相应的PFC控制模块可以用同一片吗？是不是只需改变电感器就可以了？2、在研制PFC控制电路时，通过功率变压器在加电压的过程中，有什么要注意的问题？3、现在生产PFC控制器的厂家很多，型号也很多，应怎样选择PFC控制器？
[答：Manson]	1. You can use the same control IC, e.g., NCP1650, for the power range you mentioned. Other than inductor value, you may need to consider MOSFET, rectifier and capacitor ratings too.2. It involes long answer. For application specific issues, please contact our local Field Application Engineers for help.3. Usually, power output is the first consideration. For lower power output, discontinuous current mode PFC suffice, ON Semi solution include MC33260 and MC33262. In higher output applications, continuous current mode solution is preferred, ON"s solution is NCP1650.	[2003-5-27 11:33:38]
[问：nettle]	how to choose between passive pfc and active pfc circuit?
[答：Eddie]	You can choose base on following factors.1. Target cost.2. Target size and weight.3. What power factor value need to achieve.	[2003-5-27 11:35:23]
[问：kyhong]	有没有PFC与电源做在一起的芯片？
[答：Manson]	Not for the while.	[2003-5-27 11:35:48]
[问：ltx]	做过一个240W带PFC的电源，但对EMI影响很严重，请问做PCB时要注意哪些问题呢？
[答：Kelvin]	If using double side PCB, make sure the high voltage (switching path) put on the top and keep small area, also and low voltage on the bottom side. keeping 0V area as big as possible.	[2003-5-27 11:37:58]
[问：xmpaul]	请问PFC中电感的躁声如何消除或降低
[答：TKman]	As PFC is handling low frequency harmonics, audio noise is a common problem to be solved. Techniques to overcome this are :1. Limit the inductor peak current ;2. Use CCM PFC control circuit ;3. More rigid transformer mechanical design.	[2003-5-27 11:38:03]
[问：weiyc8]	请问在有源CCM PFC中整流桥后的电容如何选择？
[答：Hector]	Selection of the filter capacitor is a balance act. The filter capacitor should be small enough to reflect the haversine waveform at AC input pin. On the other hand, if the capacitor is too small, its voltage will be drained to zero at AC zero crossing.Reference value:150W - 1uF300W - 2.2uF	[2003-5-27 11:38:04]
[问：icuser]	请问在一个250W的PC电源中，使用了有源PFC，效率降低幅度大吗？是否会给电路本身带来额外功耗而增加散热的问题
[答：Manson]	PFC stage will involve some power loss (~5%)and it is normal. Of course, extra measures needed to handle heat dissipation.	[2003-5-27 11:40:17]
[问：wcliao]	请问,MC33260和MC33262只是有无乘法器的差别,那么这两种在实际应用当中,它们的功率损耗有多大的差别呢?谢谢
[答：TKman]	MC33262 use standard multipier approach to modulate the line voltage with the bulk capacitor feedback to shape the current waveform follow the line voltage. For MC33260, no multiplier is used. For detail operation for both, please visit our website for in-depth descriptions. WWW.onsemi.com	[2003-5-27 11:41:34]
[问：wcliao]	请问第二个问题:开关电源加入了PFC进行功率方面的校正,但由于元器件的损耗等因素,会不会影响到PFC的作用呢?或者说PFC在元器件损耗方面有没有考虑到呢？谢谢！
[答：Manson]	PFC and loss are not direct related. They should be considered separately.	[2003-5-27 11:42:38]
[问：ljp]	插入PFC电路对转换器的转换效率有何影响？节能王是否也用了这样的技术？
[答：Hector]	Efficiency of PFC circuit is round 92~98%, Adding a PFC cicruit will worsen overall efficiency. If the standby requirement that you have to meet is very stringent, you may need to disable the PFC circuit at light load.	[2003-5-27 11:43:51]
[问：ljp]	有无PFC电路的总失真的变化能否用数字来说明一下？
[答：TKman]	Please refer to EN61000-3-2, IEC1000-3-2 or ICE555-2	[2003-5-27 11:45:56]
[问：bridgeacc]	PFC and PWM turn on and turn off 互相干扰，造成误动作，请问用什么方法解决改善，谢谢！
[答：Kelvin]	put it into synchronised or keep them in different frequency say 15 to 20kHZ difference.	[2003-5-27 11:46:15]
[问：Dale Li]	PFC和PWM的效率哪个更好，价格更好
[答：Manson]	PFC stage efficiency is usually higher than the converter stage. However these are 2 different requirements. PFC is to improve harmonics, converter stage is to provide application output voltages. If you need it, then you should have it regardless of price.	[2003-5-27 11:46:48]
[问：akz]	现在你们的PFC最大功率达到多少？
[答：Manson]	~2kW	[2003-5-27 11:47:18]
[问：lowsonliu]	1:DCM与CCM各有哪些优缺点.各应用在什么样的范畴?.２:两种模式下电感量如何计算?３:磁芯应如何选用?请举例说明具体的几种型号.４:在两种模式下应如何计算ＭＯＳＥＦ和整流二极管的电流平均值,有效值.峰峰值及反相耐压?贮能电容容量怎样计算?５:调试过程应注意一些什么?
[答：Eddie]	1. DCM is normally lower cost. But due to the high MOSFET peak current, it is normally used in lower power application. CCM can handle higher power and have less ripple in the PFC bulk cap. But more switching loss will dissipate to the output rectifier, and more circuit is needed to rectify this.2. For same power output, CCM need higher inductance.3. To meet the requires in performance, cost, size and shape normally designer need to design the inductor instead of getting an off the shelf part. So not partnumber suggested.4. Please refer to the design worksheet ofr that IC.5. First need to check the current and voltage do not exceed the limit of components. Also inductor will not saturate. This will ensure PFC circuit do not blow up during test. Then check the PFC"s performance like load efficiency, working range, PFC factor etc..	[2003-5-27 11:51:05]
[问：bridgeacc]	各位专家好：我在用MC33262时，PFC部分的CHOKE总是发出声音，而且input 110vac时，声音大。
[答：Hector]	Audible noise from the choke can come from different reasons. Please contact our technical staff for help.	[2003-5-27 11:51:09]
[问：07551 @sina.com]	PFC电感有没有特殊的要求？一般采用什么磁性材料？
[答：Kelvin]	depend on what topology you used, discontinous or continous. normally consider low loss material, powder core or ferrite, but ferrite have low saturation.	[2003-5-27 11:51:38]
[问：qianjiafa @163.com]	请问专家：1。我们在用UC3854时，空载容易出现过电压，对于ON的产品，对策是什么？2。PFC应用中，动态与电流响应是互相矛盾的，在ON的产品中，如何兼顾动态与电流响应谢谢
[答：Manson]	1. NCP1650 provides OVP.2. ON Semi. NCP1650 has a Line/load transient compensation block handling this issue.	[2003-5-27 11:52:27]
[问：qin]	功率因素能否对半波整流进行修正？效果是否减半？
[答：Manson]	It is not feasible.	[2003-5-27 11:53:49]
[问：ljp]	PFC中的PWM工作频率对功率修正有何影响？
[答：TKman]	Typically the switching frequency for both PFC and PWM are set at below 75KHz, the reason behind is EMC control impose a limit of 150KHz	[2003-5-27 11:54:41]
[问：kang yong6180]	开关电源中加入功率因数校正电路后，如何减小它对输出电压波纹的影响？
[答：Eddie]	Normally, PFC citcuit down increase power supplies" outputripple. Unless PFC stage switching noise go into outputcircuit.Suggest to reduce the noise generated by PFC stage first.That will improve overall EMI also.	[2003-5-27 11:54:58]
[问：jason_ chang@ampe ror.com.tw]	PWM和PFC在一起的芯片會不會對EMI有影響?
[答：Kelvin]	basically no...	[2003-5-27 11:56:51]
[问：jzh01@ mails.tsing hua.edu.cn]	do you have a simple solution for the inrush currrent in boost PFC not with a relay?
[答：Eddie]	Normal lower cost approach is to use a NTC thermister inthe input circuit to reduce the inrush.	[2003-5-27 11:57:00]
[问：sam jazz]	请问有大功率的PFC的解决方案吗？（如500W、1000W以上）。难度在哪里？因注意哪些地方？Sam
[答：TKman]	You can try MC33368, please visit our website for details.	[2003-5-27 11:58:51]
[问：hwang88]	有源功率因数校正电路用于电视机电源中,引起的对电视机画面的干扰如何解决?谢谢!
[答：Hector]	Slow down the switching rise and fall time. Add shielding.	[2003-5-27 11:59:22]
[问：kennykang]	NCP1650在汽车电子电路方面，有什么应用的例子？
[答：TKman]	The device is not intended for auto-mobile applications.	[2003-5-27 12:00:06]
[问：ywm1217]	当电源的功率较低时(小于200W),采用临界导电模式是否比连续导电模式好?谢谢!
[答：Manson]	Yes, circuit is simpler and less loss in rectifier.	[2003-5-27 12:00:48]
[问：ljp]	插入PFC后DC-DC CONVERTERS的输出纹波是否有所改善？
[答：Kelvin]	the line frequency ripple can be improved.	[2003-5-27 12:04:27]
[问：qin]	电源的PCB部线对电源的效果影响很大，ONS有无设计软件包？
[答：Kelvin]	It is a general usage of layout, we have no such software.	[2003-5-27 12:07:29]
[问：ljp]	NCP1650，MC33260等PFC内部均有PWM，能否直接用其作为DC-DC CONVERTERS的控制器？
[答：Kelvin]	since they have muitiplier, for dc-dc, there is not necessary to use such block. I suggest to use ncp12xx or NCP1560 for dc-dc conversion.	[2003-5-27 12:09:22]
[问：qin]	PFC主要可以提高电压转换效率，但其实后级转换器才真正决定效率，请问专家PFC此时的作用何在？
[答：Eddie]	PFC"s job is mainly increase the SMPS"s power factor sothat it can pass requlations. But not to boost up the efficiency of whole SMPS.Sure improving efficiency of PFC stage will make the PFCstage not dragging the overall efficiency down. But overallgood efficiency still need to have both high efficiency PFCand high efficiency PWM.	[2003-5-27 12:14:27]

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