LM5180：LM5180开关频率异常！

Hello, 

Thank you for posting. Could you share your schematic, transformer datasheet, and the operating conditions like Vin, Vout, Iout?

Best Regards,

Youhao

我目前在设计验证这个电路，但是发现开关频率异常！

想知道是器件开关控制异常，还是变压器设计问题！

期待您的回答，谢谢！

Hi, 

There may be different reasons but I do not yet have enough info to tell at this moment.  I saw your scope picture above.  Could you also zoom in the the SW signal so I can see it over smaller time scale, like 1us/div,  50us/div, and 500us/div?  Could you also add VIN, SS and 5Vout signals on the same scope picture?  I also need to know  your transformer datasheet. 

Best Regards,

Youhao

下图中，1为SS，2为Vin，3为SW！

其中1，SS是做悬空处理；2，输入24V；3，SW开关异常，导致没有输出！

变压器设计采用PC95ER9.5/5-Z磁芯；匝比按照12：3：10设计！

关于开关异常这点！期待您的解惑，谢谢！

Hi,

I worry if you have an error in the transformer polarity.  Could you share your own schematic and also your transformer datasheet?

Thanks,

Youhao

该设计是平面变压器，应当没有极性这一说法吧！

谢谢！

Then, lets debug this way:  can you remove D25, and see if you have output voltage at the +5V rail?   Then install D25 but remove D26, and check the 17V output rail?  When doing this, please capture SW and the secondary winding voltage. 

Thanks,

Youhao