开关电源中的功率因数校正ON Semiconductor

简介：

问：功率因素能否对半波整流进行修正？效果是否减半？
答： It is not feasible.

问：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： 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.

问：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： 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.

问：PFC对整机效率有提高吗？
答： 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 t

问：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： 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 h

问：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： You can try MC33368, please visit our website for details.

问：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： There are many different way to reduce output ripple.
Different case should use different approach.  Since
the application is not specified, followings are some
common methods to reduce ripple.  See which one can solve your

问：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： 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

问：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： Most PFC regulation specify 3rd harmonic requirement.   Yes, our PFC devices give good PFC performance and can meet 3rd harmonic regulation.

问：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： Normally, PFC citcuit down increase power supplies" output
ripple.  Unless PFC stage switching noise go into output
circuit.

Suggest to reduce the noise generated by PFC stage first.
That will improve overall EMI also.