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Boost Converter Output Voltage Ripple Problem

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mengghee

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boost converter ripple

hiye everybody

i have designed a boost converter and when i was measuring the output voltage ripple. i noticed that the ripple is not like a triangle wave which i am expecting. but instead it is like a square wave. i attached a snap of my scope. can anybody please tell me why this occur. the output voltage is 8v. and the load is around 20 Ohm to 300 Ohm. thank you

regards,
mengghee
 

output voltage ripple for boost converter

Hi mengghee,
It seems it is triangular wave!
but for pretty wave form, i think, you must use oscilloscope probe as close as possible to filter capacitor.
and dont use seperate ground for probe.

Regards,
Davood.
 

    M

    mengghee

    Points: 2
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boost converter switching noise ringing

does it ? look at the one with the lowest resistance. it is awful with so much noise on it. don't even know how to actually measure it. digital oscilloscope cannot look at it at all. and also the probe is directly connected to the capacitor in this one.


regards,
mengghee
 

boost converter ripple voltage calculation

in lowest resistance figure wave form not fixed.
but i see ringing in switching time.
you can attenuate that ringing with use of 0.1 uf /disk capacitor which paralled with output capacitor.
i must to mention that, some of ringing and noise actually not present at output , but oscilloscope show them!
if you change probe type or even wireing, wave form will be changed.

Regards,
Davood.
 

    M

    mengghee

    Points: 2
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ripple control from boost converter

It seems that you have two problems. First your transistor and diode are too slow, they don't acomplish the rule that:
t rise + r fall <= period/10.
the time of conmutation must be less that 0.1 times the total period.

Second it is fundamental that your boost converter acomplish the volt sec equation for the balance of the inductor, that says: the final voltage in one period must be equal to the inicial voltage of the next period. SO you have problems in the inductor.

CHeck Texas Instruments, www.ti.com, Application Note "Understanding the boost converter".

It seems your inductor is too big.
 

    M

    mengghee

    Points: 2
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solving the problem of voltage ripple

Hello , Dear mengghee :
Please tell us what kind of Boost converter you design (PWM or PFM , Voltage mode or current mode) . In your loop , the voltage of 'FB' and 'COMP' is right ?

Best Regards
Mike-Chen
 

voltage rising time of boost converter

i am designing a pwm boost converter. when this result is taken, a control scheme is not present. thank you.



regards,
mengghee
 

voltage output ripple equation boost converter

The output ripple seems to be triangular, as expected, but with impulse noise present.

This noise should be removed because it will cause trouble everywhere in the circuits that are powered by the boost.

This probably comes from the turn-on/turn-off of the transistor, a snubber could be of some use.

Good luck,

cyberblak
 

    M

    mengghee

    Points: 2
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