How to design a boost converter from 5v to 24v

[adila]

hello..im final year student..i have some problem that i doesn't know how the first step to design the boost converter circuit which is step up the voltage from 5v reach at 24 volt..anybody can help me..

 

[berkeman]

hello..im final year student..i have some problem that i doesn't know how the first step to design the boost converter circuit which is step up the voltage from 5v reach at 24 volt..anybody can help me..

Welcome to the PF. We don't do your projects for you, but can offer help if you have something specific that you don't understand. What learning resources have you used so far? Have you read the pages at wikipedia.org and at the PS IC manufacturers pages? (Maxim, Linear Technology, National Semiconductor)

What specific questions do you have about boost converters? Link to a web page with a schematic, and tell us what you find confusing...

 

[adila]

i already read the passage at wikipedia but I am still have no idea to start design the circuit..am i wrong if i used the LT1170 component to step up the voltage until 24v?This information i get from Linear Technologies data sheet.

 

[Bob S]

There are circuits around that use the ubiquitous NE555 for boost converters. The 555 is a lot easier to find and a lot cheaper than the LT1170. You can find some 555 boost converter circuits on the web. The NE555 is a very versatile chip, and has been around since the early 1970's. Learn to use the 555. It will solve a lot of your circuit problems.

 

[berkeman]

There are circuits around that use the ubiquitous NE555 for boost converters. The 555 is a lot easier to find and a lot cheaper than the LT1170. You can find some 555 boost converter circuits on the web. The NE555 is a very versatile chip, and has been around since the early 1970's. Learn to use the 555. It will solve a lot of your circuit problems.

I haven't seen that before, Bob. Is the feedback bang-bang? The OP probably should be looking at more traditional feedback loops, I would think...?

 

[berkeman]

i already read the passage at wikipedia but I am still have no idea to start design the circuit..am i wrong if i used the LT1170 component to step up the voltage until 24v?This information i get from Linear Technologies data sheet.

Yeah, the 1170 is a good candidate. What would you look into to make the output voltage 24V instead of the 12V example on the first page of the datasheet? What form of feedback does the 1170 use?

 

[adila]

yes..the data sheet only shown how to increase the output voltage to 12V..i just give the example to know whether LT1170 can be used or not instead to step the voltage into 24V..I'm so confusing right now..please help me..thanks everybody..

 

[berkeman]

yes..the data sheet only shown how to increase the output voltage to 12V..i just give the example to know whether LT1170 can be used or not instead to step the voltage into 24V..I'm so confusing right now..please help me..thanks everybody..

What learning resources do you have? Please do not consider us a design resource for your school projects. That's not what the PF is about.

I googled boost converter tutorial, and got lots of good hits. Read through some of those, and post a specific question here with a link if you still are having trouble.

http://www.google.com/search?source...4GGLL_enUS301US302&q=boost+converter+tutorial

.

 

[Bob S]

From Bob S
There are circuits around that use the ubiquitous NE555 for boost converters. The 555 is a lot easier to find and a lot cheaper than the LT1170. You can find some 555 boost converter circuits on the web. The NE555 is a very versatile chip, and has been around since the early 1970's. Learn to use the 555. It will solve a lot of your circuit problems.

I haven't seen that before, Bob. Is the feedback bang-bang? The OP probably should be looking at more traditional feedback loops, I would think...?

I modeled one in SPICE, and it worked OK, but there were some very disturbing overvoltage surges at turn-on. So, back to the LT1170 for now.
Bob S

 

[berkeman]

I modeled one in SPICE, and it worked OK, but there were some very disturbing overvoltage surges at turn-on. So, back to the LT1170 for now.
Bob S

Bang-bang feedback is okay in many applications. I've used it in Buck topologies before, but I don't know if there are special considerations in Boost topologies.

In any case, the OP should learn all about the traditional topologies and short-cuts to them, and the trade-offs. And report back here!

 

[Bob S]

I found a LT1170 5-volt-to-12-volt boost circuit in the LTSpice IV folder and tried to get 24 volts out of it by changing the feedback resistors and the inductance, but it would go only to 18 volts. I think the OP should review transformer-coupled flyback designs also. Look in the jigs folder in the examples folder in the LTC program folder for the 1170 boost circuit.

 

[berkeman]

Maybe give National Semiconductor's Webench power design tool a try...

http://www.national.com/analog/webench/power

.

 

[mheslep]

There are circuits around that use the ubiquitous NE555 for boost converters. The 555 is a lot easier to find and a lot cheaper than the LT1170. You can find some 555 boost converter circuits on the web. The NE555 is a very versatile chip, and has been around since the early 1970's. Learn to use the 555. It will solve a lot of your circuit problems.

Perhaps but I doubt this OP is a professional engineer planning to ship quantity 1000 of more units, so the cost of the parts of is trivial, and likely the value of his/her time is not. The LT1170 takes care of everything except the magnetics, caps, and power diode. More importantly, a very common first mistake in designing switchers is to underestimate parasitics when wiring or laying out the components, especially between the power switch and an external controller, so combining the two reduces the chance for a problem there.

 

[mheslep]

Flyback rules, boost and buck drools.

 

[berkeman]

Flyback rules, boost and buck drools.

But when it comes to minimum cost for non-isolated converters...

 

[mheslep]

I highly recommend the applications notes at Linear Tech, especially those by Jim Williams - they're sublime. Spend some time with these very well written and affable texts and you'll be a happy engineer.
http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1154,C1002,C1223,P1209,D4120
http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1042,C1031,C1061,P1268,D4122
http://www.linear.com/pc/downloadDocument.do?navId=H0,C1,C1003,C1042,C1031,C1061,P1266,D4176

 

[mheslep]

But when it comes to minimum cost for non-isolated converters...

Yep, minimum cost, most flexibility, least hassle.