I want a voltage booster circuit with low current loss i have tried many diffrent circuit but all of them draining my current ,i want 3.7v to 5.12v kindly help me

 

What kind of efficiency do you hope to obtain? (Higher efficiency usually means higher cost)

How much output current?
How much ripple can be tolerated? (Or to what will it provide power?)
Are there any particular restrictions on the kinds of parts you can use?

 

What kind of efficiency do you hope to obtain? (Higher efficiency usually means higher cost)

How much output current?
How much ripple can be tolerated? (Or to what will it provide power?)
Are there any particular restrictions on the kinds of parts you can use?

ya I want 1A output current with 5W power kindly help me to design with ic555 or cd4047

 

i have tried many diffrent circuit but all of them draining my current

What do you mean by that?
Draining what current?

 

What do you mean by that?
Draining what current?

for example i use 500mah but input current loss is 750mah ,250mah is going out without usage

 

for example i use 500mah but input current loss is 750mah ,250mah is going out without usage

If the output current were equal to the input current, that would break the law of conservation of energy, which requires that the power in has to be at least as great as power out.

Thus for 500mA @ 5V out (not mah which is battery capacity) generating 2.5W, the input current must be at least 2.5W/3.7V = 676mA for the same power.
So 750mA is quite reasonable, since that represents about a 90% efficiency, which about as high as you are likely to get with a practical circuit.

 

I have designed the voltage bosster and the input is 3 to 3.7v and i got the output as 6 and above but when i connect to the load that is my mobile its lagging and not getting charged kindly help me to fix here i have enclosed my circuit below

 

For starters, what is the resistance of your 100 uh inductor and what is its current rating?

You are going to have to reduce those resistors in the oscillator so you can get more output current to the base of your output transistor and you will need to change the base drive duty cycle to about 70%.

The 2N3904 needs to be replaced with a transistor with a lower saturation voltage at its peak current.

Select a new output transistor and new values for the oscillator circuit can be calculated.

You should have a buffe between the oscillator and the output transistor to make the operation of both stages more prefictable.

What can you get in the way of a fast, low saturation voltage transistor?

 

For starters, what is the resistance of your 100 uh inductor and what is its current rating?

You are going to have to reduce those resistors in the oscillator so you can get more output current to the base of your output transistor and you will need to change the base drive duty cycle to about 70%.

The 2N3904 needs to be replaced with a transistor with a lower saturation voltage at its peak current.

Select a new output transistor and new values for the oscillator circuit can be calculated.

You should have a buffe between the oscillator and the output transistor to make the operation of both stages more prefictable.

What can you get in the way of a fast, low saturation voltage transistor?

Can i replace 2N3904 with 2N2222

 

Not if you want 5V at 500 ma on the output.

I am not at my desk right now, but thinking about it for a minute, the peak collector current is going to be a little more than two amps.

That being the case you probably need a transistor that can handle 3 amps with ease while keeping the collector-to-emitter voltage very low. The lower the better, remember that the input will only be 3 volts.

If you can obtain a MOSFET with a low on resistance (.05 ohms or less) when driven by 2.5 volts that would be better.

The chances are that you will want to heatsink the transistor.

Do you have any interest in using an integrated curcuit for this project? It would speed up the project and greatly improve your chance of success.

 

After a few minutes with LTSPICE I can recommend the 2SCR542P as an example of a transistor that would be suitable for your circuit.

www.mouser.com/ds/2/348/2scr542p-774188.pdf

Can you get something with similar or better specifications?

 

Not if you want 5V at 500 ma on the output.

I am not at my desk right now, but thinking about it for a minute, the peak collector current is going to be a little more than two amps.

That being the case you probably need a transistor that can handle 3 amps with ease while keeping the collector-to-emitter voltage very low. The lower the better, remember that the input will only be 3 volts.

If you can obtain a MOSFET with a low on resistance (.05 ohms or less) when driven by 2.5 volts that would be better.

The chances are that you will want to heatsink the transistor.

Do you have any interest in using an integrated curcuit for this project? It would speed up the project and greatly improve your chance of success.

ya i am having intrest to use ic but can we use 555 or cd4047 for multivibrator but my doubt is my input is 3 to 3.7v but for 555 timer the operating voltage is 4.5v or suggest me some ic

 

You would do well to use an integrated switching regulator IC. The NE555 and CD4047 can make pulses but it is a good idea to have some regulation because your battery voltage can vary over a ±10% range. Current limiting is nice and the ability to drive the output transistor would be very for keeping the parts count (and the chances for failure and errors) down.

As far as I could tell the new chips that would be perfect for your charger are surface mount, and many of them are in leadless packages. I made the assumption that you don't want to design and etch a circuit board upon you could mount those tiny packages.

My recommendation is the MC34063 or its direct replacements such as the KA34063 in combination with an external transistor in the configuration shown below.

The MC34063 is available in an 8 pin plastic DIP package and is very common. How does this look to you?


A practical approach, but maybe not as fun approach is to buy a module pre-made on eBay.
eBay item number: 252560645903
Input voltage: 1V-5V
Output voltage: 5V
Output Current: 500mA


Less than US$1.00 including delivery.

This link might work. If not you can search using the eBay item number listed somewhere above.
http://www.ebay.com/itm/DC-DC-Adjus...645903?hash=item3acdc99f0f:g:RjsAAOSw8w1X66ot

 

You would do well to use an integrated switching regulator IC. The NE555 and CD4047 can make pulses but it is a good idea to have some regulation because your battery voltage can vary over a ±10% range. Current limiting is nice and the ability to drive the output transistor would be very for keeping the parts count (and the chances for failure and errors) down.

As far as I could tell the new chips that would be perfect for your charger are surface mount, and many of them are in leadless packages. I made the assumption that you don't want to design and etch a circuit board upon you could mount those tiny packages.

My recommendation is the MC34063 or its direct replacements such as the KA34063 in combination with an external transistor in the configuration shown below.

The MC34063 is available in an 8 pin plastic DIP package and is very common. How does this look to you?
View attachment 127599

A practical approach, but maybe not as fun approach is to buy a module pre-made on eBay.
eBay item number: 252560645903
Input voltage: 1V-5V
Output voltage: 5V
Output Current: 500mA
View attachment 127600

Less than US$1.00 including delivery.

This link might work. If not you can search using the eBay item number listed somewhere above.
http://www.ebay.com/itm/DC-DC-Adjus...645903?hash=item3acdc99f0f:g:RjsAAOSw8w1X66ot

Ya its working perfectly but cant we design this without using ic.I had tried several methods with out ic but my voltage is not boosting kindly help me to design without ic

 

ok. Can you get a switching transistor like the 2SCR542P?

Another approach is to put several 2N2222 resistor in parallel In this case you would need four of them, each with its own base resistor.

 

ok. Can you get a switching transistor like the 2SCR542P?

Another approach is to put several 2N2222 resistor in parallel In this case you would need four of them, each with its own base resistor.

No i am having transistors like 2n2222,2n3904,bc547,bd139,tip122

can u detaily explain that another approch

 

It is ugly but is can be done.

This is the basic idea: All of the emitters are connected together, the collectors are connected together, and there is a small resistor in series with each base and the other end of the resistors are connected together.

The image below should give you an idea.

 

It is ugly but is can be done.

This is the basic idea: All of the emitters are connected together, the collectors are connected together, and there is a small resistor in series with each base and the other end of the resistors are connected together.

The image below should give you an idea.

View attachment 127601

How can i use this circuit in my dc to dc converter

 

Maybe with an NE555 rather than the multivibrator. The rest of the circuit would be like your original except instead of that one 2N3904 for the output you would use 4 ea 2N2222 transistors in parallel.

Still working on the details.

What is the resistance and current rating of your 100 uH inductor?

 

What will your minimum load be?