Interleaving and voltage ripple

[gkkrish52]

Hi. I am trying to design a 2:1 step down converter. Now i am using a 2 phase clock for switching. How much interleaving we can have in the design. Kindly explain the relation between interleaving and the ripple voltage and explain why interleaving reduces voltage ripple. We can have ripples, but at what cost? what is the trade off between interleaving and efficiency. Thanks in advance

 

[KlausST]

Hi,

you are talking about polyphase power converters?

Imagine:
You have tow instead of one converter, therefore the (ripple) current is divided by two.
And the ripple frequency is multiplied by two - the phase shift usually is 180°

All in all this gives about 1/4 of the ripple voltage at the same capacitor size.

I don´t think there is a relationship between interleaving and efficiency.
If you use the same devices, then the switching loss may be about doubled, but the conduction loss may be about the half.
But you may use more optimized devices for half of the current.

Klaus

 

[gkkrish52]

Hi,

you are talking about polyphase power converters?

Imagine:
You have tow instead of one converter, therefore the (ripple) current is divided by two.
And the ripple frequency is multiplied by two - the phase shift usually is 180°

All in all this gives about 1/4 of the ripple voltage at the same capacitor size.

I don´t think there is a relationship between interleaving and efficiency.
If you use the same devices, then the switching loss may be about doubled, but the conduction loss may be about the half.
But you may use more optimized devices for half of the current.

Klaus

Hi Klaus,

The simplest converter is using 2 phase clock. If we do interleaving, lets say interleaving by 4, which means we divide the converter into 4 unit cells. How much interleaving we can have? What is the maximum limit? i see few have gone to 32 phase interleaving.

I agree that switching losses are doubled as we have more switches compared to the simple converter due to interleaving. What is the trade off between interleaving and switching and conduction loss.? I have to optimize the width of switches with respect to power loss.

Gopal

 

[KlausST]

Hi,

What is the trade off between interleaving and switching and conduction loss.?

* Calculate the loss of a single phase unit.
* Calaculate the loss of a single interleaving unit (as a function of load current) and multiply it with the number of units.

Compare them. No one else can do this for you, because only you have the information for the calculations.

How much interleaved units?
I don´t think there is a technical limit.
It´s more a question of cost, effort and benefit.

I assume you need to find it on your own.

Klaus

 

[gkkrish52]

Hi,



* Calculate the loss of a single phase unit.
* Calaculate the loss of a single interleaving unit (as a function of load current) and multiply it with the number of units.

Compare them. No one else can do this for you, because only you have the information for the calculations.

How much interleaved units?
I don´t think there is a technical limit.
It´s more a question of cost, effort and benefit.

I assume you need to find it on your own.

Klaus

Hi Klaus,

Sure. I will try to calculate the loss of a single phase unit. Thanks for your help.

Best Regards,
Gopal