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boost 3v to 12v @ 1A Design help

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jb123

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Hello,
I need to boost 3vdc to 12vdc at 1amp or greater.
I was using a product to boost 3v to 8v, but now I need to increase that to 12v...
That product is called 'micropuck' from ledsupply.com

but the 'micropuck' only puts out 8v @ 500ma... i need 12v @ 1amp.
I really like the simplicity of that 'micropuck', 2 wires in & 2 wires out... doesnt get any easier

So I have done a little research and found a few IC's that look like they may do the job... but I would really like some help from knowledgeable people :)

Here is what I have been considering:
part numbers for digikey.com:
LT1072CT#PBF-ND
LM2577T-12-ND
MAX1771CPA+-ND

Can someone help with a schematic so I can get this built asap?
I sincerely appreciate any help :)
J
 

franciscorc

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keith1200rs

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WebBench on National Semiconductor's site will do the design for you (and suggest suitable devices).

Keith
 

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jb123

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That webbench looks pretty neat, but seems impossible to use.
I have tried everthing but cannot get it to work.
I type in max vIN = 2.5v and immediately tells me this solution is not webbench enabled.
I look at the available parts and there are plenty that will do the job, but I cannot get it to take.

For example the LM2621 specs are exactly what I am looking for, but why will it not let me.

Here is what I type in:
Vin min = 2.5v
Vin max = 5v
Vout = 12v
Iout = 1
Amb Temp = 30
and I get "your solution is not yet webbench enabled"

I tried typing in exactly the specs of the LM2621 and get the same answer.
 

IanP

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The average switching current while converting from 3V to 12V@1A (assuming 80% efficiency) will be around 5A, so the only realistic option is an IC with an external power switch ..
Taking into account the above the good candidate for this job seems to be the MAX1771 with an external power MOSFET ..
In its data sheet you will find schematic diagram of a non-bootstrapped converter that produces 12V output, and from the table 4a select an appropriate current sensing resistor ..

IanP
:-D
 
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jb123

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I did purchase a LT1072CT and LM2577T... I almost purchase a max1771 but though these would do the job better since the 1771 was listed with a max current of 727ma.
Any way I can use one of those 2?

---------- Post added at 05:05 AM ---------- Previous post was at 03:59 AM ----------

Also, 9vdc instead of 12vdc would work for my needs too.
Would that be easier?
 

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nico_2010

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did you try with MC34063? It is simple to use, require few components and can deliver 1,5A.
 

mira2830

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I don't think that MC34063 can deliver such current without external transistor :???:
 

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nico_2010

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It is necessary indeed, but he didn't say the minimum number of components!
Anyway, one BD 249/TIP41 transistor it's enough and cover specifications
 

Minte

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It is necessary indeed, but he didn't say the minimum number of components!
Anyway, one BD 249/TIP41 transistor it's enough and cover specifications

Can you explain where the transistor goes on the MC34063 to achieve this? and do I have to add any other components along with the transistor?
 

DBPhillips

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The MAX1771 is a controller and can do whatever current or voltage you want. But as the peak current limit set by the current sense resistor is set higher for the design, it becomes increasingly tricky to keep switching EMI off the FB pin and ground bounce from the AGND and PGND pins, and good board layout becomes challenging. If the MAX1771 doesn't like the layout, it is likely to burst and have high output voltage ripple. But I've successfully used it for designs with current limits up to 10A.

The best reference for understanding and designing with the MAX1771 is the MAX863 data sheet. The parts are similar but the timing specs are different. And, if my memory is correct, there is a MAX608 which operates down to lower input voltages.
 

tpetar

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Like Franciscorc suggest in post #2 maybe this MAX668 can do the job, but min input is 3,3V :

Using MAX668 integrated circuit you can build a very simple and high efficiency power supply . With Max668 you can design various power supply circuits using few external components . This power supply circuit based on the MAX668 integrated circuit is a high efficiency step up converter that will provide an fixed output regulated voltage around 12 volts at a maximum output current of 2.3 amperes . This step up converter circuit will provide a 12 volts output voltage from a 3.3 to 5.5 input voltage .

As you can see in the table bellow you can see how the output voltage vary in concordance with the input voltage .
R1 from this circuit senses the inductor current for current mode controller and with some internal comparators provide a current limit. R5 in conjunction with C9 filters the switching noise on the sense resistor to prevent false triggering of the current limit. The MAX668's internal current-limit threshold is fixed; changing the resistor, R1, adjusts the current-limit setting. The resistor, R2, sets the operating frequency.
The external components of the MAX668 can have high-voltage ratings that provide greater flexibility for high-power applications.

**broken link removed**

https://www.electroniq.net/power-supply/3v-5v-12v-step-dc-converter-circuit.html
 
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DBPhillips

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With a PWM controller, like the MAX668, one gets the advantage of constant-frequency operation which is good for EMI control in noise sensitive audio and RF applications. But the advantage is achieved at the price of less flexibility in inductor value and vulnerability to a right-hand plane zero that moves into the control bandwidth and contributes to instability at high boost ratios. When designing with the MAX668, the inductor value is limited by requirements for proper slope compensation to reduce risk of instability from subharmonic oscillation. And the right-hand plane zero is an issue when the inductor value allows operation in continuous conduction mode. "Continuous conduction mode" is simply geek jargon that means that the inductor current doesn't ramp to zero during each switching cycle.

With a minimum off-time PFM controller, like the MAX1771, MAX863 or MAX608, one gets the advantages of fast transient response, great flexibility in inductor selection for cost-performance trade-offs and invulnerability to the right-hand plane zero at the cost of variable frequency EMI and sensitivity to board layout.

If you're designing an audio or RF project, and not boosting too much, the MAX668 is a first option to consider. For general use or when you're doing something wild, like boo

- - - Updated - - -

... like boosting to 500V, then the MAX1771 is a better option.
 

DeepOne

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Yes, but output voltage is assigned by divisor on five pin of mc34063 - 300/100 >> 5V, 860/100 >>12.
 

RAJAT AGGARWAAL

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once my cousin was trying same thing,, then he came to know that the source battery was not able to deliver such amps--- even after a big cap on it..
 

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