buck boost converter

[Angelodiaz]

can somebody help me design a buck boost converter with a 42% gain from the input voltage. there is no parameter to be used, i just need it for simulation. can somebody suggest an easy component that will be available for me to build in an actual circuit. thank you so much.

 

[Diver300]

I think that you will need a bit more explanation, even if it just for a simulation.

What do you mean by 42% gain? If you want the output voltage to be 42% more than the input voltage, you need a boost converter, which is much simpler than a buck / boost converter. If you want the output voltage to be 42% of the input voltage, you need a buck converter, which is also much simpler than the buck/boost converter.

Have you got ranges for the input and output voltages?

 

[Angelodiaz]

what i mean about it is that it can give you 42% higher output voltage compared to the input voltage as well as give you a 42% lower output voltage compare to the input voltage. the easy explanation for that is a circuit which can step up or step down the input voltage by 42%. thank you for the response. the range is from 0v to maybe 60v.

 

[ronsimpson]

the range is from 0v to maybe 60v.

Range of what? Input or Output? It is hard to make a power supply with a output of near "0V".

Input voltage Min._________, Max________
Output voltage Min._______, Max_________

 

[Angelodiaz]

input voltage is minimum of 9v and maximum of 60v. im really sorry.

 

[ronsimpson]

What SPICE are you using for simulation?

 

[Diver300]

If the voltage is going to have to be increased and decreased, you will need a buck / boost converter.

What controls the output voltage? How is it set to -42% or to +42%, or presumably anywhere in between.

Your question implies that if the input voltage changes, then the output voltage changes. Is that correct?

 

[Angelodiaz]

diver yes if the input voltage changes the output voltage also changes but the 42% will be retain.

 

[Angelodiaz]

ron im only using electronic workbench because thats the only simulation allowed by our professor.

 

[ronsimpson]

our professor

Your request is strange. "42% of input". Please, can you post the exact words the Professor used. Is it written in a book?

 

[Angelodiaz]

its not written in a book. my professor wants us to build a buck boost converter circuit that can step up or step down the input voltage by 42% on the load.

 

[ronsimpson]

Sorry for all the questions.
When Vin = 10V what is the output range? Vout min=4.2V, Vout max=? (is it 14.2v?)

 

[Angelodiaz]

yup. thats exactly what im talking about. and im sorry if my instructions arent clear.

 

[Diver300]

What controls the output voltage, for a fixed input voltage? If the input voltage is 10 V, what makes it 5.8 V (-42%) or 14.2 V (+42%)

 

[ronsimpson]

Almost all PWM ICs have a "feed back" pin and a internal "reference voltage".
It is common for the refence voltage to be 2.5V or 1.25V or 5V. That can not be changed.
The IC will compare the out voltage (a division of the output voltage) to the Vref.
If the output is 5V then use two resistors to divide down to 2.5V and that goes to the FeedBack pin and is compared to the 2.5V Vref. That is how the IC knows to increase or decrease the duty cycle.

In your project there can not be a Vref but you must Vin as a reference. This is much harder because I can only think of two ICs that allow you to work this way.
In your SPICE do you have a part "TL494" or a "78S40"?

 

[Angelodiaz]

there is no tl494 and 78s40. ive been reading other forums here and i tried the other circuit shown but its hard to control the output voltage. maybe you can give me other components to be used.

 

[ronsimpson]

TL494 Note the two error amplifiers have the + and - inputs free.

78S40 Note the "Comp" has both pins brought out. This is not typically done.

This is the little brother to the 78S40. Note that the "Comp +" pin is connected to the reference voltage and can not be changed. 99.9% of the ICs are like this. I have look before and can not find a part that works well.

 

[Angelodiaz]

thank you so much for this great help. ill try to use this.

 

[Angelodiaz]

ron im sorry but this ic is still not available on my simulator.
the only available is the 555

 

[ronsimpson]

We need to find a way to set the output voltage based on Vin not Vref.
Example: Vin =10V Vout=5.8 to 14.2 With simple resistors I can not make a reference like that. But I can make a reference at 1/2 of that.
Using two resistors and a POT I think we can make a POT that will produce 2.9 to 7.1V and that is 1/2 of what we want the output to be.
The two 10k resistors makes 50% of Vout.
These two voltage can be fed to a amplifier to determine of the duty cycle needs to be changed.

only available is the 555

LOL How can you build anything with only one IC?