Boost converter

[odaysaad]

I have design interleaved boost converter with three inductor operates with 3pwm with phase difference 120 degree..iput voltage 12 volt and output voltage 168 volt but with high spike in output voltage can any one help me to reduce the spike in output voltage please

 

[KlausST]

Hi,

How can we help, what is your idea?

From the scope picture we can see the spike, but you don't give us any chance to see where it comes from.
We don't see at which signal you measure, we don't see your scope's GND connection.

* post your schematic
* post your PCB layout
* post photos
...

You are not the first one with spike problems. Thus there are already numerous discussions.
Read through some of them, then you get a clue what to look and care for.

Klaus

 

[dick_freebird]

First you need to determine whether the "spike"
is real, or a 'scope grounding / pickup-loop
artifact.

High-ESR, high-ESL filter cap at the output is a
good way to see leading edge "spikes" as the
cap is not acting as a cap against high dV/dt.
Show your output filter (if any). Show the load.

14:1 is a pretty high boost voltage ratio. You
might be better off with a flyback, so some or
most of the boost can come from turns ratio?

 

[stenzer]

Hi,

First you need to determine whether the "spike"
is real, or a 'scope grounding / pickup-loop
artifact.

this application note [1] might help you to improve your probing, if not already considered.

[1] https://assets.nexperia.com/documents/application-note/AN90004.pdf

BR

 

[BradtheRad]

Notice the inductor has to generate a power pulse much higher than 168V. If it doesn't then it fails to overcome output voltage.

The pulses are narrow. They have to provide all power used during idle periods. It looks as though you're measuring voltage at the node joining inductor, switch, diode.

 

[shomikc]

Try having a look at the inductor and capacitor values and modify your calculations if necessary or if possible. I think lowering the inductor value might help. If the load is inductive you could try placing an appropriate free wheeling (anti-parallel) power diode or a schottky diode for high frequency. If you can simulate your circuit in Orcad PSpice I think you will get a better idea of what is going on.

 

[dick_freebird]

Here's another thought, it appears there's a lot
of ringing but decimated by the'scope timebase.
Maybe the switch device wants a properly tuned
snubber? You don't perhaps need the snappiest
turnoff, mellowing it out ought to reduce any
inductance related (cap ESL, wireball, load
characteristic) overshoots.

 

[cupoftea]

What is your power level?
I think you may need each boost to be a cascaded boost....two boosts controlled by one controller.

[B]dick_freebird[/B] was right 14:1 is high.​

(i dont know why im stuck on bold now sorry)

--- Updated Dec 18, 2021 ---

How much c(out) do you have?
Can you see us the volts across yoru source sense?

 

[asdf44]

Yeah correlate those spikes to events in your circuit. Is it each fet switching or maybe only one phase?


As said figure out if it’s real: attach scope gnd to your circuit then attach the scope probe to its ground. That shows scope pickup.

 

[Easy peasy]

the spikes are mostly artifact getting into your scope, there will be a little bit of overshoot - but not that much ....

for Brad - the boost inductor supplies Vout - Vin, volts, if it has to overcome significant L in the output loop then the boost-L will supply a lot more volts to keep the current flowing - so layout may well be an issue for this ckt - but we don't know as we can't see the layout ...

 

[dick_freebird]

Another possibility (as we still do not know anything about schematic, layout and applied control signals) is that the spike -is- the boost phase, petering out to the VIN-Vf forward push, and then the switch turns on again setting output current to zero; repeat....