DC boost converter max power ?

[bianchi77]

Re: DC boost converter max power ?

I'm thinking if I increase the frequency, it will reduce the inductor size but from my experiment if I increase the frequency, it will reduce the voltage output. but I'll make another experiment to make sure

[bianchi77]

Re: DC boost converter max power ?

According to
http://www.daycounter.com/LabBook/Bo...quations.phtml

L equation at the end, I need 34.8 mH inductor
Vout =220 V Vin = 12V VD = 1V D = 0.99 iLoad = 20mA f = 3KHz

[bianchi77]

Re: DC boost converter max power ?

I used 120uH 2A toroid inductor taken from broken TV PSU...hmm...increase the inductance ? how much percent do you reckon ?
I got 230V for the start then drop to 205V in about 60 seconds and RL is hot...
Thanks again for the link and equation, so far I used the equation attached...

[budm]

Re: DC boost converter max power ?

wrong post, never mind.

[budm]

Re: DC boost converter max power ?

http://www.daycounter.com/LabBook/Bo...quations.phtml
http://www.daycounter.com/Calculator...lculator.phtml

You may be able to contact the person.
Excert:
So it is clear that the output voltage is related directly to the duty cycle of the pulses.
The main question when designing a converter is what sort of inductor should be used. In most designs the input voltage, output voltage and load current are all dictated by the requirements of the design, whereas, the Inductance and ripple current are the only free parameters. It can be seen form Equation 1, that the inductance is inversely proportional to the ripple current. In other words, if you want to reduce the ripple, then use a larger inductor. Thus, in practice a ripple current is decided upon which will give a reasonable inductance.

There are tradeoffs with low and high ripple current. Large ripple current means that the peak current is ipk greater, and the greater likelihood of saturation of the inductor, and more stress on the transistor.

So when choosing an inductor make sure that the saturation current of the inductor is greater than ipk. Likewise, the transistor should be able to handle peak current greater than ipk. The inductor should also be chosen such that the it can handle the appropriate rms current.

It should be noted that when there is a light load the circuit can slip into discontinuous mode, where the inductor becomes fully discharged of it's current each cycle. When a load is reapplied the inductor needs to recharge, and so the transistor's duty cycle increases pulling the inductor towards ground, and because of the increased duty cycle Vout decreases when we really want it to increase. This causes an instability, which is well known for boost converters, and not a problem with buck converters.

One way to combat this instability is to choose a large enough inductor so that the ripple current is greater than twice the minimum load current. When this condition is met then the inductor is always in continuous mode.

[bianchi77]

Re: DC boost converter max power ?

Yes I have read the link, thanks for that,
now I got 218V with RL = 10K, nearly 5W ...it's doing the job but not stable...the voltage is dropping to 205V...I have no idea why, yet...trying to find out why ?
Duty cycle 99.8%...

[budm]

Re: DC boost converter max power ?

Read the link yet? See Figure 5:
https://www.maximintegrated.com/en/a...ex.mvp/id/2031
To do simple experiment, replace the switch with MOSFET and drive it with signal generator, then you can play with frequency, inductor value, etc. Look at the wave form with scope, etc.. you need to collect the data and see if it jives with the calculation.

[bianchi77]

Re: DC boost converter max power ?

Continuing experiment now it's 308V at RL 47K...it matters of duty cycle of my PWM...
that's the factor I've been playing now to get the right power, are you playing (doing experiment) with switching power supply as well ?
for 10 Watt, it will be RL = 4840 ohms or 4K7 1/10 of my current RL....that's ok I like learning and experiment the basic ===>
Battery ==> inductor ==> switch

[bianchi77]

Re: DC boost converter max power ?

Probably will be too much to learn and a waste time to understand basic principle.
https://www.maximintegrated.com/en/a...ex.mvp/id/2031
https://www.maximintegrated.com/en/a...ex.mvp/id/1897
Beside the circuit, the parts lay out is also VERY IMPORTANT! You can have the most wonderful circuit on the piece paper but if the layout is bad then it is worthless.

An experiment 124V with RL 47K ..it's running and when I touch the resistor , I felt the heat on it...it's 2.6 mA on 124V..
Thanks for the tutorial, I'm using figure 2 topology..

[budm]

Re: DC boost converter max power ?

Probably will be too much to learn and a waste time to understand basic principle.
https://www.maximintegrated.com/en/a...ex.mvp/id/2031
https://www.maximintegrated.com/en/a...ex.mvp/id/1897
Beside the circuit, the parts lay out is also VERY IMPORTANT! You can have the most wonderful circuit on the piece paper but if the layout is bad then it is worthless.

[budm]

Re: DC boost converter max power ?

I got 40V on RL = 4K7, and the input is 12V 60VA, how can I increase the output voltage ? so I = 8.5 mA
Does my oscilatting frequency matter ? I used 3Khz now...
Cheers

What do you mean 12V 60VA? 12V and how many the circuit is drawing from the 12V? So it drops from over 200VDC no load down to 40V with only 8.5mA of current draw, it is not working, that is all I can tell you.
60VA?
VA:
https://en.wikipedia.org/wiki/Volt-ampere.
Well since you do not want to do any calculation and using formula to find out if your inductor will work with that 3KHz then you are just making guessing game. 3KHz, really?

[bianchi77]

Re: DC boost converter max power ?

I got 40V on RL = 4K7, and the input is 12V 60VA, how can I increase the output voltage ? so I = 8.5 mA
Does my oscilatting frequency matter ? I used 3Khz now...
Cheers

[bianchi77]

Re: DC boost converter max power ?

So you are saying that you can now get 220VDC at 1A and ran it for 12 Hours?
Can we see the pictures of the prototype? input current = ??? Regulation = ???%, Input Voltage range?
Did the inductor go into saturation? etc.
https://cdn.badcaps-static.com/pdfs/...6c9f827c6c.pdf

I'm talking about the SATA PATA PSU, it had been fixed and tested for 12 hours with load..
Nope I haven't got 220VDC at 1A but I will..

[budm]

Re: DC boost converter max power ?

It's a simple astable multivibrator and FET with inductor and resistor voltage divider...I'm not running here but I'm learning here.I don't use any advance PWM chip.I want to know how it works.
on SATA and PATA, the dual transistor is the PWM, that's a cheap and smart idea to make it into production and they are all fixed and running now....made abit modification and tested for 12 hours run non stop, all good....learning and learning...
The price of 2 transistors and 1 power FET will be cheaper than 1 advance PWM chip, profitable for production...

So you are saying that you can now get 220VDC at 1A and ran it for 12 Hours?
Can we see the pictures of the prototype? input current = ??? Regulation = ???%, Input Voltage range?
Did the inductor go into saturation? etc.
https://cdn.badcaps-static.com/pdfs/...6c9f827c6c.pdf

[bianchi77]

Re: DC boost converter max power ?

This chip UC3842CP

[bianchi77]

Re: DC boost converter max power ?

Chips like the UC384x series, or MC34063, not to mention the zillions of knockoffs, despite calling them "advanced", simplify the matter of designing these simple DC-DC converters SO much, and they can be had for dirt cheap.

One could argue that designing a discrete version would actually be that much more difficult, due to the interactions between all the circuit elements (not to mention the tolerances).

In the case of the chips i've mentioned, you have all the equations in the datasheets (or worst case, in some application notes). All you'd need to do, to make it (even) easier, would be to plug all the needed formulas into a spreadsheet, and mess around with the component values for the passives needed around those chips (a few resistors & caps).

While technically cheaper, going discrete for a design like this is just making things harder than needed for yourself (not to mention people who are trying to help you). True, the component cost is less, but if you're talking about "profitable for production", you'd also need to factor in the man-hours (and associated cost) for the DESIGN of the thing

All that is if we disregard the fact that, especially in the case of boost converters, you very much DO want overvoltage protection, at the very least, which is a whole different headache if you insist on not using specialised PWM controllers.

Just a quick browse on fleabay:

http://www.ebay.com/itm/10Pcs-Dip-8-...MAAOSwHMJYI0rM
That's TEN pieces for 1.11$AU...

384x ones are a bit more, 5pcs for around the same price:
http://www.ebay.com/itm/5PCS-IC-UC38...sAAOSwg3FUbbBt

Mouser prices are, as you'd expect, a bit higher, but it's a 100% legit source (ie. there shouldn't be any risk of fakes, plus you'd have proof of sourcing the components, for RohS qualifications and whatnot).

34063's start from about 0.46$AU/pc @1pcs, and 384x's (in 8-pin packages) from around 0.79$AU/pc @10pcs, it would seem.

That's the cost argument right out the window. Next?

Ok, I've read about that UC384X chip as well.It's on my altium now but
I'm just wondering if I can play with transistor or 555 which I have some on my box and it's multipurpose for doing oscillator job, I know there are some factors I must consider, that's why I learn and learn, anyway I like playing,experimenting and learning, do you ?
Those transistors and 555s are my toy for a long time already
yup ...labour cost is expensive...

What do you suggest for overvoltage and overcurrent protection ?
What I have experience is the power transistor and oscillator are death by the time there is short on the output....

The simplest I can think of is put fuse on the output...

[Khron]

Re: DC boost converter max power ?

Chips like the UC384x series, or MC34063, not to mention the zillions of knockoffs, despite calling them "advanced", simplify the matter of designing these simple DC-DC converters SO much, and they can be had for dirt cheap.

One could argue that designing a discrete version would actually be that much more difficult, due to the interactions between all the circuit elements (not to mention the tolerances).

In the case of the chips i've mentioned, you have all the equations in the datasheets (or worst case, in some application notes). All you'd need to do, to make it (even) easier, would be to plug all the needed formulas into a spreadsheet, and mess around with the component values for the passives needed around those chips (a few resistors & caps).

While technically cheaper, going discrete for a design like this is just making things harder than needed for yourself (not to mention people who are trying to help you). True, the component cost is less, but if you're talking about "profitable for production", you'd also need to factor in the man-hours (and associated cost) for the DESIGN of the thing

All that is if we disregard the fact that, especially in the case of boost converters, you very much DO want overvoltage protection, at the very least, which is a whole different headache if you insist on not using specialised PWM controllers.

Just a quick browse on fleabay:

http://www.ebay.com/itm/10Pcs-Dip-8-...MAAOSwHMJYI0rM
That's TEN pieces for 1.11$AU...

384x ones are a bit more, 5pcs for around the same price:
http://www.ebay.com/itm/5PCS-IC-UC38...sAAOSwg3FUbbBt

Mouser prices are, as you'd expect, a bit higher, but it's a 100% legit source (ie. there shouldn't be any risk of fakes, plus you'd have proof of sourcing the components, for RohS qualifications and whatnot).

34063's start from about 0.46$AU/pc @1pcs, and 384x's (in 8-pin packages) from around 0.79$AU/pc @10pcs, it would seem.

That's the cost argument right out the window. Next?

[bianchi77]

Re: DC boost converter max power ?

It's a simple astable multivibrator and FET with inductor and resistor voltage divider...I'm not running here but I'm learning here.I don't use any advance PWM chip.I want to know how it works.
on SATA and PATA, the dual transistor is the PWM, that's a cheap and smart idea to make it into production and they are all fixed and running now....made abit modification and tested for 12 hours run non stop, all good....learning and learning...
The price of 2 transistors and 1 power FET will be cheaper than 1 advance PWM chip, profitable for production...

[bianchi77]

Re: DC boost converter max power ?

I know, and i can't blame you...

Nothing wrong with aiming high, but there's that whole thing with "you gotta learn to walk, before you learn to run". Cutting corners in this field isn't much of an option (unless one doesn't mind risking life and limb in the process)

I'm not cutting corner here...learning and learning...Do I run now ? it's learning to walk now..

[bianchi77]

Re: DC boost converter max power ?

Here's the circuit, what do I need to make it powerfull ? I follow the principle of inductor doing its job. Don't say 1A...0.1A of 220V is good for my experiment.
Yup I'm learning ohm law, but something practical is more interested to me..doing all math calculation without my hand working on the PCB making me bored.
I keep learning no matter other people call me, it doesn't matter..

Learning is steep and deep but I enjoy it