Buck-boost converter output current limiter

In summary, this buck-boost converter offers roughly the output power I need (80 - 120 Watts) but I need only low to moderate voltages (2.5V to 5.75V) to achieve those power levels.
  • #1
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How can I get around current limiter of this buck-boost converter to achieve a lot higher current output than max rated current output for a very short amount of time ?

Does having high continuous current discharge power source at the input help it in any way ?

This buck-boost converter offers roughly the output power I need (80 - 120 Watts) but I need only low to moderate voltages (2.5V to 5.75V) to achieve those power levels.

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# Manufacturer max rating :-10 Amps, has 15 Amps onboard protection fuse

# Desired output current :- Up to 25 Amps for 5 seconds or less at a time

# For typical output voltage range : 2.5V to 5.75V

# Power input :- Parallel 2 X 3.6 V (nominal) + Parallel 2 X 3.6 V (nominal) in series (7.2V nominal) lithium-ion batteries with max continuous current discharge of 20 Amps per battery.

# Application :- Repurposing for DIY electronic cigarette (e-cig)

The product is listed here.
 

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  • #2
Sid55 said:
Does having high continuous current discharge power source at the input help it in any way ?
No.

Sid55 said:
Power input :- Parallel 2 X 3.6 V (nominal) + Parallel 2 X 3.6 V (nominal) in series (7.2V nominal) lithium-ion batteries with max continuous current discharge of 20 Amps per battery.
You should pick a different (just buck) converter rated for 25A. In theory this converter has an external current sense, so you might be able to modify the limit with replacing the resistor, but 2.5 times higher current is not OK with the inductor, the FETs, the PCB and the connectors. Also, since the dissipation will be at least 2.5 times higher the heatsinks will be definitely very busy.
 
  • #3
Rive said:
You should pick a different (just buck) converter rated for 25A.
Agreed.

And from your previous thread, it looks like you are not real experienced in using electronics and batteries. Do you have a local person who can mentor you on thie project? And what does "repurposing an e-cig lighter" mean?

https://www.physicsforums.com/threads/how-much-current-is-drawn-absolutely-confused.954686/
 
  • #4
berkeman said:
Do you have a local person who can mentor you on thie project?
No, unfortunately I don't.

berkeman said:
And from your previous thread, it looks like you are not real experienced in using electronics and batteries.
I'm not. That's why I'm here.

berkeman said:
And what does "repurposing an e-cig lighter" mean?
No idea what you mean by "e-cig lighter." I never mentioned "e-cig lighter" in my inquiry, if you bother to re-read my previous post.

Seems like you're confusing electronic lighter with electronic cigarette. Electronic lighter is purpose-designed/built to light up traditional cigarettes, the ones with tobacco wrapped with paper, whereas electronic cigarette is purpose-designed/built to heat up cotton soaked with thick liquid to vaporize the liquid. The vaporized liquid may or may not contain nicotine depending on user's customization.

e-smoke.jpg
My more fundamental question, aside from technical questions in my previous post, is how do buck-boost converters inside electronic cigarettes handle such insane levels of current discharge despite being built with no so beefy components while being incredibly tiny in physical size compared to buck-boost converter mentioned in my previous post ?
 

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  • #5
Sid55 said:
No idea what you mean by "e-cig lighter." I never mentioned "e-cig lighter" in my inquiry, if you bother to re-read my previous post.

Seems like you're confusing electronic lighter with electronic cigarette.
Oops, sorry for my brain fade. I don't use either, so I glossed over the details of what you asked. o0)
Sid55 said:
My more fundamental question, aside from technical questions in my previous post, is how do buck-boost converters inside electronic cigarettes handle such insane levels of current discharge despite being built with no so beefy components while being incredibly tiny in physical size compared to buck-boost converter mentioned in my previous post ?
That's a reasonable question. Do you have a schematic of such 25A e-cig circuits? As long as you take care with the safe operating area (SOA) of the semiconductors and size the important things correctly, you can take advantage of the low duty cycle of the 25A requirement.
 
  • #6
Rive said:
You should pick a different (just buck) converter rated for 25A.

I have now come to agree with you.

The one I could find is SZBK07 300W 20A (listed here) buck converter though it does not seem to output high current discharge at low output voltages as demonstrated here -
 
  • #7
berkeman said:
Do you have a schematic of such 25A e-cig circuits?

Texas Instruments has 200W 1V to 10V at 20A to 45A output synchronous 4-switch buck-boost converter design based on the LM5175 controller for e-cigarette applications. Schematic PDF here and test results PDF here. Overview here.Texas Instruments 200 Watts 1V to 10V at 20A to 45A output chipset board PMP20327
200W E-Cigarette Buck Boost.png

Evolv DNA 200 Watts 0.5V - 9V (up to 50A) output chipset board. Evolv DNA 200W datasheet here.
dna200.jpg

Texas Instruments 200 Watts 1V to 10V at 20A to 45A schematic (screenshot from schematic PDF)

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  • #8
Sid55 said:
whereas electronic cigarette is purpose-designed/built to heat up cotton soaked with thick liquid to vaporize the liquid.
So are there voltage and current standards in the industry for getting optimum vapors off of these modules? Are there datasheets available to the public, or are they mostly proprietary to the e-cig industry?
 
  • #9
Sid55 said:
Texas Instruments has 200W 1V to 10V at 20A to 45A output synchronous 4-switch buck-boost converter design based on the LM5175 controller for e-cigarette applications. Schematic PDF here and test results PDF here. Overview PDF here.
Can you just use that?
 
  • #10
berkeman said:
So are there voltage and current standards in the industry for getting optimum vapors off of these modules? Are there datasheets available to the public, or are they mostly proprietary to the e-cig industry?
E-cig chipset makers are limited by what they can get out of 3.6V (nominal) lithium-ion and lithium polymer batteries.

18650 3.6V (nominal) lithium-ion high continuous discharge battery is the most commonly available and the widely used power source. Used in single or dual (series) or triple (series) and quad (parallel-series) connection.

20700 3.6V (nominal) lithium-ion high continuous discharge battery is far less available than 18650 3.6V and is far less used power source.

21700 3.6V (nominal) lithium-ion high continuous discharge battery is just as far less available and is far less used power source as 20700 lithium-ion battery.

26650 3.6V (nominal) lithium-ion battery is almost exclusively used as a single battery power source e-cigs.

Lithium polymer batteries are most commonly used for powering low power (about 70 Watts or less) e-cigs and is rarely used in high power e-cigs due to lithium polymer battery's inherent volatility at very high current discharge and due to other risk factors.

JPH_Maxim.jpg
 

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  • #11
berkeman said:
Can you just use that?

I highly doubt the schematic would be drastically different from other e-cig chipset makers however components used more than likely would be.
 

What is a buck-boost converter output current limiter?

A buck-boost converter output current limiter is a device used in power electronics to regulate the output current of a buck-boost converter. It limits the maximum current that can flow through the converter, ensuring that the output voltage remains stable.

How does a buck-boost converter output current limiter work?

The limiter works by monitoring the output current of the converter and adjusting the duty cycle of the switching element to maintain a constant output current. When the output current reaches the set limit, the limiter reduces the duty cycle to prevent the current from exceeding the limit.

Why is a buck-boost converter output current limiter necessary?

Without a current limiter, the output current of a buck-boost converter can exceed the maximum rated current of the components, leading to overheating and potential damage. The limiter ensures that the converter operates within safe limits, preventing damage and improving its overall reliability.

What are the benefits of using a buck-boost converter output current limiter?

In addition to preventing damage to the converter, a current limiter can also improve the efficiency of the system by reducing power losses. It also allows for more precise control of the output current, which can be useful in applications where a stable and precise current is required.

Are there any limitations to using a buck-boost converter output current limiter?

One potential limitation is that the limiter may introduce additional complexity and cost to the system. It may also affect the response time of the converter, which can be a concern in applications where a fast response is required. Additionally, the limiter may not be able to protect against all types of current surges, so it is important to carefully select and design the limiter for the specific application.

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