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Frequency Calculation for Boost Converter

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Yaser43082

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Hello Everyone,

I am trying to build a Step-Up Converter and have a few questions. I basically have a 3v supply voltage and want to step up to 5 volts @800mA

1) Can the PWM be substituted with a momentary switch?
2) How does one calculate Ripple Voltage?
3) How do u calculate the frequency?
4) What should be the Voltage breakdown be of the Diode?

Thank you in advance
 

Omar El Kelany

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Hello Everyone,

I am trying to build a Step-Up Converter and have a few questions. I basically have a 3v supply voltage and want to step up to 5 volts @800mA

1) Can the PWM be substituted with a momentary switch?
2) How does one calculate Ripple Voltage?
3) How do u calculate the frequency?
4) What should be the Voltage breakdown be of the Diode?

Thank you in advance
i think this will help

http://www.daycounter.com/LabBook/BoostConverter/Boost-Converter-Equations.phtml
 

Tahmid

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Hello Everyone,

I am trying to build a Step-Up Converter and have a few questions. I basically have a 3v supply voltage and want to step up to 5 volts @800mA

1) Can the PWM be substituted with a momentary switch?
2) How does one calculate Ripple Voltage?
3) How do u calculate the frequency?
4) What should be the Voltage breakdown be of the Diode?

Thank you in advance
1) I'm not clear about what you're asking. The switch you see in diagrams (between inductor and ground) is to be replaced with a transistor, MOSFET, IGBT or other such switch, not a physical switch.

2) You calculate the ripple voltage from the used capacitance. Or you calculate capacitance from a determined/desired ripple voltage.

3) You should a frequency where the benefits such as smaller inductance and capacitance outweigh the losses such as switching losses. Usually frequencies are estimated and adjusted, often by trial and error.

4) It should be greater than the output voltage. Use a safety margin.

You might want to go through this: http://www.ti.com/lit/an/slva372b/slva372b.pdf

Hope this helps.
Tahmid.
 

Tahmid

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Which controller are you using? Usually a frequency between 30kHz and 100kHz is used. You can just start with 50kHz.

You may want to experiment with a few selected frequencies and see the effects. Try 30kHz, 50kHz, 75kHz and 100kHz.
 

Omar El Kelany

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u put the frequency u want..as frequency increases capacitance and inductance values decreas ...also decreasing the ripples..but u ave to try just like Tahmid said to get the best
i hope this help
 

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