UCC28740: 占空比

cks Chen

Part Number: UCC28740
Other Parts Discussed in Thread: PMP41009

Hello, respected experts. I have encountered a problem. I designed a wide - input - range flyback converter using the UCC28740 chip and the same two - transistor cascaded flyback topology as that of the PMP41009 design. During the testing process, I found that the duty cycle of the MOSFET controlled by the control chip is very small. Moreover, under heavy load conditions, the output voltage is only about half of the designed rated output voltage. I have tried changing the parameter values of many components, but there has been no improvement. May I ask where the problem lies? The first figure shows the driving waveform of the MOSFET under no - load conditions, and the second figure shows the driving waveform of the MOSFET under heavy load conditions.

5 天前

0 Lydia 5 天前

TI__Mastermind 37555 points

Hello, we have received your case and the investigation will take some time. Thank you for your patience.

0 Daniel 4 天前

TI__Mastermind 42555 points

您好

UCC28740: UCC28740:PMP41009

请您参考这部分说明。

0 cks Chen 4 天前回复 Daniel

Prodigy 90 points

Hello, do you mean that I should rebuild the transformer according to the design parameters you provided?I followed your parameters for the design calculation, but I still found that the ton value is less than the required 280 ns.By the way, does D1 refer to the duty cycle? Is the value of 0.048189 too small?

0 Daniel 4 天前回复 cks Chen

TI__Mastermind 42555 points

您好

根据您的说明跟这个帖子相似问题，您可以参考一下。

0 cks Chen 4 天前回复 Daniel

Prodigy 90 points

I know—this post was also mine. My issue is that when I designed and calculated based on the parameters you provided, the Ton value is still less than the required 280 ns. Also, does D1 refer to the duty cycle? Is the value 0.048189 a bit too small?

0 cks Chen 4 天前回复 Daniel

Prodigy 90 points

Hello, my design still requires an auxiliary winding. Could you please provide the auxiliary winding-related parameters, such as the turns ratio between the primary winding and the auxiliary winding? I'm worried my calculation might be incorrect because I'm not confident in my ability to work it out properly.

0 cks Chen 18 小时前回复 Daniel

Prodigy 90 points

Hello, I have redesigned the transformer using the parameters you provided, but there has been no improvement at all — the duty cycle is still extremely small. In your opinion, what other aspects could be the cause of this problem?

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UCC28740: 占空比