Viper12, AC-DC non isolated Buck converter 5V 60mA

[MGökhan]

Hello,

I'm considering using Viper12 to 3Phase AC/DC non isolated buck converter 5V 60mA Vout. I found some application notes like AN1357. But is it reliable? Or will it cause problems in long-term operation? Has anyone experienced it before?

Thanks,

Gökhan

[Peter BENSCH]

Welcome @MGökhan, to the community!

First, a note: the AN1357 is already obsolete and has long been unavailable online (at least on our website).

Although you did not specify the value of your 3-phase voltage, assuming a voltage of 380V, you will not be able to use a controller with buck technology. The reason for this is that with your low output power of 0.3W, the controller would have to have extremely short switch-on times in order to regulate effectively, which such controllers are not designed for. In addition, in this voltage class, a regulator with a maximum reverse voltage of 1050V, such as VIPER265K, would have to be selected, but this is also not suitable for your application.

In your case, a flyback regulator will work most reliably. On the one hand, it requires a transformer, but on the other hand, it can work without any problems with regulators such as the above-mentioned VIPER265K.

Hope that helps?

Regards
/Peter

[MGökhan]

Hi Peter,

Thanks for your answer! You can find the AN1357 attached and the file says that it can work with additional components. 

[Peter BENSCH]

You still haven't mentioned what the effective value of your input voltage is or what the maximum value of the rectified 3-phase voltage is. Without this information, I'm assuming 380Vac or 540Vdc.

The outdated AN1357 you uploaded refers to a buck converter with a single-phase mains voltage of max. 265Vac and a larger load. In this configuration, such a non-galvanically isolated design can certainly work. The eDesignSuite from STMicroelectronics can also simulate such single-phase designs – but only for reasonable voltage and load ranges.

If your 3-phase voltage is 380Vac, such a buck converter is not feasible for your very low output voltage of 5V, as I explained earlier.

Regards
/Peter