Author Topic: Simple discrete two transistor boost converter.  (Read 37538 times)

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Offline technix

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Re: Simple discrete two transistor boost converter.
« Reply #25 on: March 05, 2017, 05:08:09 am »
Those STC15W401AS's look pretty nice at that price point.

Can you recommend a basic dev kit for these at all?

Sadly STC themselves does not offer kits. You can buy DIP variants of the chips though for easier breadboarding.

And you can spin for a few of their highest end IAP15W4K61S4 in DIP-40. That chip is largely code compatible with STC15W401AS but it offers on-chip debugging (Only their IAP15F2K61S2, IAP15L2K61S2, IAP15W4K58S4, IAP15W4K61S4 and STC8 series support on-chip debug.)
 

Offline dchauran

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Re: Simple discrete two transistor boost converter.
« Reply #26 on: June 04, 2020, 05:43:20 pm »
Just registered to say thinks for sharing this! I needed a small, low power boost converter, and didn't have the ICs to use with a conventional design, plus a very low part count. This is great because it works with common parts that everyone probably has laying around.

I used a 4n20 fet, because it's what I had. I also only had a 68k resistor, so I used that in place of the 70k, and finally I didn't have a 100u ceramic cap, so I used a 100u electrolytic, since I assume the only purpose was for output filtering. I also added a 1k resistor and led to verify the output. I am using this to boost 4.5v to 7.5v to drive a small LNA for a software defined radio, and the circuit is small enough that it fits in the footprint of the lna board. Took me a while to figure out the right layout - I am a novice, and have no experience with layout software, so I had to lay it out in my head and build it on protoboard.
 

Offline stevetob67

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Re: Simple discrete two transistor boost converter.
« Reply #27 on: June 06, 2020, 02:39:05 am »
Reading stuff like this from you guys makes me realise just how much a noob I really am  :-DD
 

Offline RefrigeratorTopic starter

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Re: Simple discrete two transistor boost converter.
« Reply #28 on: June 13, 2020, 12:40:23 pm »
....and finally I didn't have a 100u ceramic cap, so I used a 100u electrolytic, since I assume the only purpose was for output filtering.
Almost any type of capacitor works on the output, also don't forget a capacitor on the input (~47µF) this helps increase the efficiency of the converter.
Low ESR caps are best for this stuff, you can often tell them apart by their golden lettering.
Get LTspice if you don't have it already, it's free and super fun to play around with. You can simulate most of these circuits before building them.
Also old motherboards are great for switching MOSFETs and inductors for DIY DC-DC converters.  :-+
Old DELL motherboards for the pentium 4 processors tend to have through hole versions of SMD MOSFETs that can be used in breadboards and are also easier to desolder than their SMD counterparts.
I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
An expert of making MOSFETs explode.
 

Offline RefrigeratorTopic starter

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Re: Simple discrete two transistor boost converter.
« Reply #29 on: June 13, 2020, 12:45:06 pm »
Reading stuff like this from you guys makes me realise just how much a noob I really am  :-DD

Reminds me of that time i was a noob as well  ;D
I have a blog at http://brimmingideas.blogspot.com/ . Now less empty than ever before !
An expert of making MOSFETs explode.
 

Offline Abdul Haseeb

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Re: Simple discrete two transistor boost converter.
« Reply #30 on: July 11, 2021, 08:35:33 am »
Is there anyone who can help me in understanding the circuit operations. I need help like how BJT works in here and how it is empowering MOSFET's gate terminal and how they are charging the inductor.
Any help would be highly appreciated.
 


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