Pic 877A and boost converter

[williB]

Has anyone ever built a boost converter ( dc to dc )
just curious as the power output of anyones boost.

i think i got about 49Watts at most , at a resonable efficiency , dont remember off hand.

anyone ever boosted 100 Watts , or more?
if so what was the efficiency
i did mine with a 16F877A's PWM

 

[williB]

no ones built a boost converter?

 

[justDIY]

i'm sure lots of folks here have built step-up or boost converters ... I guess no one felt like replying to your query.

I've built many small boost converters, probably the largest is taking 3.3v and boosting it up to 5v, only around 5 watts however. most of mine aim for a higher voltage at a rather low current, like 30v at 15mA for a big string of LEDs.

I tried once using a PIC as the brains of a 'digital smps', and it was fun, but my programming skills aren't that great. I leave the smps controlling to dedicated chips and regulators. One of my favs is TI's TPS61040. It has a tiny SOT23-5 package and contains it hefty 400ma switch (iirc), all you add is a diode, a few small caps and the feedback circuit (voltage divider or current sense resistor).

 

[Papabravo]

As you are no doubt aware a high power boost converter poses some interesting challenges. As I see it the magnetics are everything, and they are probably the least understood component in the designers bag. I'm with justDIY, and I prefer the dedicated controller chips since the guys who make them know one helluva lot more about SMPS then I ever will.

 

[Hero999]

What frequency did you use?

What topology?

Have you thought about building a qusi-resonant converter?

I've read a lot about them and they seem the best topology to use for higher power converters

 

[williB]

sorry that i did not respond earlier , was busy building an ultracap engine starter.
Why ?
Because i wanted to see if i could start a car with caps.. and i can say that it does work.
I took out the battery out of a portable Powerpack, its something that 'triple A' would use to jumpstart your car.
and then i put in place of the battery , 12 Ultra caps ( rated at 2.5V each and 350 Farads ) , i made two strings of six each for a total of 116 Farads at 15 Volts.
wanna see some pix?

 

[kchriste]

Has anyone ever built a boost converter ( dc to dc )
just curious as the power output of anyones boost.

I built a voltage booster to eliminate the voltage drop between my truck and camper. This ensured that the camper batteries would reach full charge in a minimum amount of travel time. I used the PWM from a PIC16F684 running at 20Mhz thus giving me a 78.2Khz period with 8bit resolution. The PIC also doubles as a 3 stage charging controller for when the camper is plugged into AC. I was able to boost 12.0Vdc to 14.2Vdc at 15amps output at around 90% efficiency.

 

[donniedj]

Boost converter.. sure but at voltages far beyoNd your applicatiOns. The power level is not based on what controls the logic of course buT is based On the main comPonents, inductOr, switch, diode. What do you plan on using as the voltage source? With a targe voltage of 15v I aM wonder why even aMplIfy any sourcE and use 15+v directly.

Joules = .5xFxV^2 = 13,050 Joules! A 1000 Watt chager will take 13 seconds to charge your cap bank. A 100 Watt charger will take 130 seconds. This is too slow for my purposes but is not unreasonable for car starting applications.

Site:
http://www.anothercoilgunsite.com/nf-barriers.htm "Charging"

Forum Link:
**broken link removed**

Assembly:
http://www.anothercoilgunsite.com/vid79-acgrifle-injector1.wmv
http://www.anothercoilgunsite.com/vid80-acgrifle-injector2.wmv

 

[williB]

i just spent 1.5 hours replying to everyone who posted a reply , all wiped out when i went to look up a word ,

 

[donniedj]

Always, always, always, copy the text box and paste to a local file. And always save the local file with each new sentence added. So does this mean you should recopy the whole posting text box after each sentence? Yes, Yes, and Yes.

Why? Because theres nothing worst then to have to retype it all over again.

 

[williB]

this is the finished power pack .

 

[Nigel Goodwin]

this is the finished power pack .

Man!, it's really small

 

[Mike - K8LH]

Is that the 115 farad battery pack Willi?

 

[williB]

Nigel its really light too the whole unit weighs 2.77kg or 6.1 lbs
that includes the #4 gauge cables and the battery clamps.

Mike yes thats it
there are twelve 350F (2.5V) caps , two strings of six each,
350/6 *2 = 116.6 F at 15 V max

 

[donniedj]

Have you tried a load test yet? I ask because the internal impedance of the caps, super caps to me, may to very high, which in turn limit the discharge current. You will need hundreds of amps for a car starter.

 

[williB]

186 Amps to be exact , to start my car ,thats initially of course
i've allready done it..
it started up great
the ESR of the caps is 3.2 milli Ohms each
with over 500,000 duty cycles till they start to degrade
i figure that i have 499,975 to go. lol