请教PI工程师:关于基于STACKFET拓扑,用TNY274G制作的700mW反激电源

PI工程师你好,现本人制作了一多路输出的反激电源,是基于STACKFET拓扑结构,芯片为TNY274G.
输入电压为300-600VDC
5路输出分别为:
1 17V/6mA   25T  isolated
2 17V/6mA   25T  isolated
3 17V/6mA   25T  isolated
4 17V/2mA   25T  same GND with 5V
5 5V/70mA   8T
变压器:
Primary:   150T 1.1mH  air gap:0.45mm
E16/5 14PIN BOBBIN,ISOLATION:800V
Test voltage:2.5kV
现在对电源已经作了一周的测试,但是效率始终不能够提高,只有45%-50%本人用5V作为反馈回路,同时由于此电源应用于solar inveter, 所以optocouple 在此项目中禁止用.因此采用的是偏置线圈的反馈,在此想请教PI的工程师,对于如此高压输入,小功率输出的电源怎样才能提高效率呢?本人期望的效率是70%,但是觉得很难,功率太小了.请PI的工程师多多赐教,给与建议.

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liujiehit2000

LV.1

2007-09-04 19:58

No any answer? PI AE: could give me some suggestion on that? what kind of methods would be posibility for realizing the high efficiency aming to the high voltage input and low power output?

liujiehit2000

LV.1

2007-09-05 00:34

Today, I made some improvements on the flyback converter. Untill now the efficiency is up to 54,66% at 380VDC input. In order to make the further step on efficiency, Could PI expert bring some suggestions on that. Thx.

liujiehit2000

LV.1

2007-09-07 09:16

PI的工程师不在吗?怎么没有回复呢?自己顶一下,坛子里的电源高手给个建议,看看有没有什么办法解决效率问题,明天我会将原理图以及PCB的图放上来,请高手赐教!

powerint_lp

LV.4

2007-09-07 09:46

@liujiehit2000

建议你做以下实验:
1.260vac输入条件下,该电源的效率,
2.260vac输入条件下,不用stack的mosfet,效率能到多少.
通常在条件2下,用274做5v输出为主的设计或者多路输出,效率也只能在70%左右,输入电压提高会使变压器及开关管的结电容损耗增加(这个你可以看380v跟600v输入时效率有无差别),另外附加的mosfet会有额外损耗,在输出功率很小的情况下,一点点多的损耗都会对效率有很大影响.
最后,建议检查一下功率计读数是否准确.

liujiehit2000

LV.1

2007-09-20 22:59

PI engineer, I have made the same experiment without stackfet topology. Then the efficiency is the same with before result. Thereby I think maybe the issue is not the IC. Until now I make some other improvment on that, and the efficiency is about 68,55%. It is little more highter than before. Now I will attachment the schematic, and please help me improve that. I hope that efficiency can reach over 70% at 750mW output power. and input voltage is from 300-600V
output power is about 750mW. 132311190300361.pdf