Three phase AC input to 5V/500mA transformerless

[vindhyachal]

A) Input is 3 phase ac

B) Output required is 5Vdc/500mA

C) Should be trasnformless, inductor can be used

I checked VIPER318HD, ( https://eds.st.com/console/#/app/acdc/ic_acdc_catalogs/filter/%5B%22buck%22%5D/selected/viper318hd:buck ) & designed using ST edsign suite, but max voltage it support is 300Vac with single phase

Another link i found here: https://www.st.com/resource/en/application_note/cd00074286-threephase-smps-for-low-power-applications-with-viper12a-stmicroelectronics.pdf

it makes three phase to single dc output, but still uses transformer.

Any workable solution any one know

[Peter BENSCH]

You could e.g. use the VIPer26 or VIPer26K for this, there is also some proposal for an non-galvanic isolated buck in the datasheet of the VIPer26K.

Good luck!

/Peter

[vindhyachal]

Hi Peter,

Page 8 of this app note: ( https://www.st.com/resource/en/application_note/cd00074286-threephase-smps-for-low-power-applications-with-viper12a-stmicroelectronics.pdf )

has this image.

The red box i understand, can make AC-to-DC till here.

After that have to convert this pulsating dc to 5V/0.470A without transformer.

I think VIPER267K can work here ( https://eds.st.com/console/#/app/acdc/ic_acdc_catalogs/filter/%5B%22buck%22%5D/selected/viper267k:buck ), as it has 1050V rugged, but edesign suite does not have option for three phase input or I am not able to find. Can you suggest , because edesign suite automatically suggests rated compoennts also.

Or if there any other better solution then let me know.

[Peter BENSCH]

Yes, the VIPer267K is a variant of the VIPer26K with a drain current limitation of 700 mA.

One limiting factor of a non-galvanically isolated converter is this current limitation. The maximum output current is therefore lower than the peak current, whereby its minimum value (here 0.66 A) must also be taken into account, which leads to the 470mA you already mentioned.

Currently the eDesignSuite does not support 3-phase rectifiers as the vast majority of users wants to get max output power and/or galvanic isolated systems.

Regards

/Peter

[vindhyachal]

Hi peter,

This is how i plan to convert three phase(with neutral) to dc . Simulated only yet, to be tested

After that I used e-dessign suite with:

1 Vin: 85V-600Vac

2.Out: 5Vdc/0.47A

it makes this circuit, but some of its compnents are very non standard, is there option to select standard parts?

Also output will be 5V/0,47A , how much tolerance in current and voltage we have to expect here?

[vindhyachal]

Hi,

A) I have put these specs in e-desgin suite:

Vin: 85V-600Vac

Vout: 5V/470mA

It geneartes below diagram: But I have below queries

B) The arrow sign marked in red, how is digital low power ground connected here? How will i et 5V at the output then?

C) Also do high power ground and low power ground need to be shorted (marked by green box) . Datasheet of VIPER26K says it should.?

[Peter BENSCH]

Let me first answer your last question: the red arrow points to a triangle, which is some kind of a GND seen by the VIPer267K only (!). It is not the GND for your 5V output voltage!

Please connect the load parallel to Cout, i.e. at Vout (5V) and the neutral line N (your left green box)

The VIPer26K in this mode works floating. Maybe it gets more clear with the same schematics shown in fig. 29 of the datasheet.

To your questions before:

Which of the components you'd like to modify?

Tolerance: It is difficult to specify a value for such a buck controller, as it also depends on the behavior of the load. Usually behind this is a linear regulator with a suitable PSRR value at the specified switching frequency in order to smooth the output voltage.

Regards

/Peter

[vindhyachal]

Hi Peter,

Thanks for info . I made the out changes, and attached is new schemtaic. After this Cout will connect a LDO regular for 5V/470mA.

The component selection I took from here: https://www.st.com/en/evaluation-tools/steval-vp26k01b.html

Please suggest.

[Peter BENSCH]

That looks OK so far.

You might consider the LD39100PUR as an LDO because of its good power supply rejection ratio. Please consider the additional voltage drop of the LDO and set the output of the VIPer at about 5.2...5.3V.

Good luck!

/Peter