UCC28950: Dutycycle

Venish S

Prodigy 10 points

Part Number: UCC28950

Hi im venish,

We used that part for dc to dc converter 1000W, i want duty cycle calculation for output regulation,

over 1 year ago

0 Mike O' over 1 year ago

TI__Guru* 86266 points

Hello,

I am reviewing your inquiry and will get back to you shortly.

Regards,

0 Mike O' over 1 year ago in reply to Mike O'

TI__Guru* 86266 points

Hello,

The following link will bring you to an application note that goes through the step by step design process of the UCC28950 in a PSFB converter.

I believe that you will find this application note helpful in your design process.

https://www.ti.com/lit/an/slua560d/slua560d.pdf

In the application note equation 6 give an equation for duty cycle.

Regards,

0 Venish S over 1 year ago in reply to Mike O'

Prodigy 10 points

Thanks you mike for supporting

0 Mike O' over 1 year ago in reply to Venish S

TI__Guru* 86266 points

Hello,

I was glad that I could help.

Regards,

0 Venish S over 1 year ago in reply to Mike O'

Prodigy 10 points

hello,
i have one doubt EA+ how working in duty cycle ?, can you explain that function .

0 Mike O' over 1 year ago in reply to Venish S

TI__Guru* 86266 points

Hello,

I am reviewing your inquiry and will get back to you shortly.

Regards,

0 Mike O' over 1 year ago in reply to Mike O'

TI__Guru* 86266 points

Hello,

The EA + is the non inverting input to the error amplifier. The output of the error amplifier controls duty cycle.

If EA + is greater than EA - the output of the amplifier will go high demanding more duty cycle. If EA - is greater than EA + the output of the error amplifier will go low demanding less duty cycle.

Regards,

0 Venish S over 1 year ago in reply to Mike O'

Prodigy 10 points

hello mike o, thanks for knowlege sharing but i have one more doubt, like this EA+ Greater than EA- the output of the amplifier will go high demanding more duty cycle that is ok, but my doubt is how controlling constant current & constant voltage the output DC

0 Mike O' over 1 year ago in reply to Venish S

TI__Guru* 86266 points

Hello,

I am reviewing your inquiry and will get back to you shortly.

Regards,

0 Mike O' over 1 year ago in reply to Mike O'

TI__Guru* 86266 points

Hello,

The UCC28950 can be directly setup for peak current mode control of peak voltage mode control. The device does not come with all the circuitry necessary for constant current/constant voltage mode control.

If your require constant current/constant voltage mode control more than likely you are designing a battery charger.

The following link will bring you to 2 kW phase shifted full bridge battery charger reference design using constant current/constant voltage mode control.

https://www.ti.com/tool/PMP8740

The following link will bring you to an application brief written by the engineer that did the 2 kW design. I believe you will find the reference design and application note helpful in your design process.

https://www.ti.com/seclit/ml/slup348/slup348.pd

Regards,

0 Venish S over 1 year ago in reply to Mike O'

Prodigy 10 points

helo mike o,
thanks for sharing

0 Venish S over 1 year ago in reply to Venish S

Prodigy 10 points

hi mike o, i tried to calculate but Fet Rdson voltage drop value i can't understand, can you share calculation .

0 Mike O' over 1 year ago in reply to Venish S

TI__Guru* 86266 points

Hello,

I am reviewing your inquiry and will get back to you shortly.

Regards,

0 Mike O' over 1 year ago in reply to Mike O'

TI__Guru* 86266 points

Hello,

The voltage while the switch is on (Vrdson), will be the drain to source current times the FETs on resistance (Rdson).

Vrdson = Irdson*Rdson

Regards,

0 Venish S over 1 year ago in reply to Mike O'

Prodigy 10 points

hello mike o , thanks for sharing , but i dont know about Irdson can you expalin it?

0 Mike O' over 1 year ago in reply to Venish S

TI__Guru* 86266 points

Hello,

I am looking into your inquiry and will get back to you shortly.

Regards,

0 Mike O' over 1 year ago in reply to Mike O'

TI__Guru* 86266 points

Hello,

Irdson is the drain to source current through the FET when, when the FET is On.

Regards,

0 Venish S over 1 year ago in reply to Mike O'

Prodigy 10 points

Hello mike o, i seemed your msg that is continues current or actual current based on circuit?

0 Mike O' over 1 year ago in reply to Venish S

TI__Guru* 86266 points

Hello,

I am reviewing your inquiry and will get back to you shortly.

Regards,

0 Mike O' over 1 year ago in reply to Mike O'

TI__Guru* 86266 points

Hello,

It is actaully the peak current going through the FET drain to source.

Regards,

0 Venish S over 1 year ago in reply to Mike O'

Prodigy 10 points

thanks mike o for sharing information

0 Mike O' over 1 year ago in reply to Venish S

TI__Guru* 86266 points

Hello,

I was glad that I could help.

Regards,

0 Venish S over 1 year ago in reply to Mike O'

Prodigy 10 points

Hi mike,

Ucc28950 EA+ feeding voltage 1v but dutycycle increase 50%, we measured different dutycycle that times works but now not working properly, what's the problem in controller?

0 Mike O' over 1 year ago in reply to Venish S

TI__Guru* 86266 points

Hello,

I am reviewing your inquiry and will get back to you shortly.

Regards,

0 Mike O' over 1 year ago in reply to Mike O'

TI__Guru* 86266 points

Hello,

The EA + is typically used to set the DC control voltage as shown below. The internal voltage amplifier will raise or lower the comp pin until the correct output voltage and duty cycle is achieved. If EA - is < EA +, COMP will increase to increase duty cycle and the voltage at EA -. If EA - is > EA +, COMP will decrease to decrease the duty cycle and the voltage at EA -.

So if your duty cycle is increasing that would indicate that VOUT is low and the controller is trying to achieve the desired output voltage.

Is this what you are observing?

Regards,

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UCC28950: Dutycycle