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Buck-Boost Converter with Fixed Output Voltage

v1.5

Member
Hello there
I'm looking for some kind of buck / boost converter circuit for my next circuit board. I have done my research on the internet for a while and I have been able to find the TPS55288 integrated circuit that can do this job. That's why I want to get information from you about other solutions.
I must first specify the qualities I am looking for. I plan to make some kind of driver circuit and control circuit connected to it. This circuit will include igbt s and drivers. As you know, IGBT trigger voltages at 15V is the desired value in many datasheets. but it's really hard to find 15V from an external source. For this reason, I would like to make a converter with a buck boost converter ic that produces a fixed 15V voltage, raises or lowers the output according to the value of the input voltage. According to the input voltage values between min 5V and max 24V, the output voltage should be 15V. In this way, I plan to provide convenience to the user. I think min 1A will be sufficient for the output current.
What are the circuits or methods you know that can do this task? Should I use ic like TPS55288 for this job or are there easier and cheaper solutions? Thank you.
 

ronsimpson

Well-Known Member
Most Helpful Member
This thing is a big monster. 16A

I think you want 1A. Try this. You might want LTC3115 for more current. You should set "under voltage lockout" to 4.5V because it is hard to boost low voltage up to 15V and this part will try to work at 2.2V and should be told to not start working unless the voltage is 4.5 or 5V
1604163367960.png
--edited--
I am playing with the above. It is hard to boost from 5V to [email protected] It takes 3A at 5v to get 15v at 1A and this part does not like 3A. So the ltc3115 is better.
 
Last edited:

v1.5

Member
This thing is a big monster. 16A

I think you want 1A. Try this. You might want LTC3115 for more current. You should set "under voltage lockout" to 4.5V because it is hard to boost low voltage up to 15V and this part will try to work at 2.2V and should be told to not start working unless the voltage is 4.5 or 5V
View attachment 127749
--edited--
I am playing with the above. It is hard to boost from 5V to [email protected] It takes 3A at 5v to get 15v at 1A and this part does not like 3A. So the ltc3115 is better.
Thank you. I will try that at this evening.
 

eTech

Active Member
hi

This is sort of a contradictory statement:
"For this reason, I would like to make a converter with a buck boost converter ic that produces a fixed 15V voltage, raises or lowers the output according to the value of the input voltage. According to the input voltage values between min 5V and max 24V, the output voltage should be 15V."

how can the input raise or lower the output, but the output be fixed? o_O
 

v1.5

Member
hi

This is sort of a contradictory statement:
"For this reason, I would like to make a converter with a buck boost converter ic that produces a fixed 15V voltage, raises or lowers the output according to the value of the input voltage. According to the input voltage values between min 5V and max 24V, the output voltage should be 15V."

how can the input raise or lower the output, but the output be fixed? o_O
Its because of my bad English xd
 

rjenkinsgb

Well-Known Member
Most Helpful Member
I suspect the OP means boost/raise the voltage when it is lower than 15V and buck/lower when it's higher than 15V.

That fits with all the other parameters.
 

v1.5

Member
I suspect the OP means boost/raise the voltage when it is lower than 15V and buck/lower when it's higher than 15V.

That fits with all the other parameters.
Yeah. That is exectly what i wanted to say
 

ChrisP58

Well-Known Member
Why do you want to use IGBTs?

IGBTs have the advantage for high voltage applications >400Volts, but mosfets are much better for low voltage applications.
 

v1.5

Member
This thing is a big monster. 16A

I think you want 1A. Try this. You might want LTC3115 for more current. You should set "under voltage lockout" to 4.5V because it is hard to boost low voltage up to 15V and this part will try to work at 2.2V and should be told to not start working unless the voltage is 4.5 or 5V
View attachment 127749
--edited--
I am playing with the above. It is hard to boost from 5V to [email protected] It takes 3A at 5v to get 15v at 1A and this part does not like 3A. So the ltc3115 is better.
sorry I couldn't deal with the circuit for a while.
The simulation result of the circuit is excellent, but the price is very high! Really very expensive. Do you know a cheaper solution?
 

rjenkinsgb

Well-Known Member
Most Helpful Member
You can buy ready made modules that do exactly what you want, quite cheaply - eg. input 5 to 32V in, with a variable output that can be set to 15V:

Or 5 to 15V in:
 

v1.5

Member
Why do you want to use IGBTs?

IGBTs have the advantage for high voltage applications >400Volts, but mosfets are much better for low voltage applications.
system will work with single phase rectification
 

v1.5

Member
You can buy ready made modules that do exactly what you want, quite cheaply - eg. input 5 to 32V in, with a variable output that can be set to 15V:

Or 5 to 15V in:
yes, I thought about them too, but actually I am looking for a circuit that detects the input voltage and can work in buck or boost modes to keep the output stable.
maybe some unnecessary effort but I don't want the user to interfere with the circuit.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
yes, I thought about them too, but actually I am looking for a circuit that detects the input voltage and can work in buck or boost modes to keep the output stable.
maybe some unnecessary effort but I don't want the user to interfere with the circuit.
You mean exactly like that module?.

If you don't want the pots, replace them with fixed resistors.
 

v1.5

Member
You mean exactly like that module?.

If you don't want the pots, replace them with fixed resistors.
Yeah. I want an automatic buck / boost converter. output voltage is constant 15V. but I don't want the pot just like you said. As soon as the user energizes the circuit, the dc / dc converter circuit should detect and give a constant 15V output. Can I do this with fixed resistors? How is this possible? For example, the user can apply an input voltage between 5V and 24V, it is completely up to the user. The user will not tell me the voltage value to be connected to the circuit. Only the circuit that will apply energy with sufficient power and the circuit will stabilize the output according to this voltage.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Yeah. I want an automatic buck / boost converter. output voltage is constant 15V. but I don't want the pot just like you said. As soon as the user energizes the circuit, the dc / dc converter circuit should detect and give a constant 15V output. Can I do this with fixed resistors? How is this possible? For example, the user can apply an input voltage between 5V and 24V, it is completely up to the user. The user will not tell me the voltage value to be connected to the circuit. Only the circuit that will apply energy with sufficient power and the circuit will stabilize the output according to this voltage.
You simply adjust the pots for the voltage and current you want, then remove the pots and replace with fixed value resistors of the same values.

This is exactly what you would do if you built the circuit from scratch yourself - or calculate the resistor values instead, then tweak the values if need be.

If you download the schematic for the module (it will be available somewhere), you could copy it and build your own - but it would be considerably more expensive.
 

ronsimpson

Well-Known Member
Most Helpful Member
then remove the pots and replace with fixed value resistors of the same values.
We put glue on the pots so they can not be adjucted.
If you download the schematic for the module
The schematic is not published. But you might find it in the data sheets.
One of the links above does not use a "boost/buck IC" but uses a boost power supply much like this: (R1+R2=pot)
1604323581961.png
Then follows it with a buck supply like this: (add pot to pin 4 and use the LM2596-adj)
1604323676361.png
I do not think it boosts well. (certainly not to 3A)
1604323857415.png
 
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Nigel Goodwin

Super Moderator
Most Helpful Member
We put glue on the pots so they can not be adjucted.

The schematic is not published. But you might find it in the data sheets.
While the makers don't publish it, you can often find it on-line where someone has reverse engineered it.

Here's an example of a design similar to the XL6009 ones:


 

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