3V to 9V converter

[Ziddik]

ppl,
i need a 3V to 9v converter circuit for my new project, so i want know and learn about them, can anyone post a schematic that is easy to build? I got a 3.7V battery with 750mA current and want 9v or 12V out of it

 

[bountyhunter]

ppl,
i need a 3V to 9v converter circuit for my new project, so i want know and learn about them, can anyone post a schematic that is easy to build? I got a 3.7V battery with 750mA current and want 9v or 12V out of it

Look at the datasheet for the LM2731.

https://www.electro-tech-online.com/custompdfs/2011/12/lm2731.pdf

 

[crutschow]

You do realize that the output current will be reduced by the ratio (ideally) of the input voltage to the output voltage. It practice the current will be even less due to converter inefficiencies.

 

[Ziddik]

No problem mate, and i got a schematics from collin's site here, does it work? And how much current will be reduced from 750mA while it outputs 9V?

 

[colin55]

The inverter circuit shown above is only good for 20mA ouput.
For every 10mA output, the current from the battery will be about 40mA.
How much output current do you want?

See also Roman Black's circuit:
simple +5v to +13v Converter
https://www.romanblack.com/smps/conv.htm

 

[Ziddik]

collin@ i want power your fm transmitter circuit. And i don't know how much current it draws, is it possible?

 

[colin55]

We have perfectly-good FM transmitters that work on 3-4v.

 

[audioguru]

We have perfectly-good FM transmitters that work on 3-4v.

But they have fairly short range because when the voltage is low then the RF power is also low.

 

[Ziddik]

audioguru is right, so how much current the transmitter draws which i posted in the other thread?pls click here for the schematic https://electro-tech-online.com/att...3764092-tunable-rf-coils-question-2w56lmx.gif if the circuit is ok with current, then i need a boost converter for this circuit

 

[audioguru]

You modified that circuit. But the schematic you keep posting is the wrong original circuit with 3 transistors so you are confusing everybody.
I posted a circuit with a single transistor that I guessed is the circuit you used. Please post your accurate schematic.

 

[colin55]

What you are both failing to realise is the fact that these circuits use only a fraction of the supply voltage to produce the output amplitudes. Secondly, the maximum allowable RF energy is only about 10mW to 30mW. These transmitters will reach over 1km on this output power. Anything over 100mW produces lots of technical problems. There is absolutley no need to increase the supply to 9v.

 

[Dr.james]

good circuit

 

[Ziddik]

my bad. as guru stated, i modified the circuit using s8050 transistor and got over 2Km of range, but i have to supply 9V for the 2Km goal and that's why i need a boost converter, @guru,

i changed the 2nd transistor with s8050 and removed the final amp transistor, and replaced the v.cap with a fixed "15pf" cap, finally the emitter resistor of 2nd transistor replaced with 100ohm, that is all i modified, @collin, you still didn't mention that the boost conv. Is possible to use with the TX or not.

 

[audioguru]

What you are both failing to realise is the fact that these circuits use only a fraction of the supply voltage to produce the output amplitudes.

A fraction of the supply voltage?
I simulated my FM transmitter RF section:
1) With a 3V supply the output is 3.2V p-p and the power into a 75 ohm whip antenna is 17mW.
2) With a 9V supply the output is 11V p-p and the power into a 75 ohm whip antenna is 12 times more at 203mW.

I used my FM transmitter for only an hour to test its range so the RF cops did not catch me.
I don't think there are any RF cops in Z!dd!k's country.

 

[Dr.james]

u made no sense

 

[Ziddik]

lol no, i haven't seen any "RF COPS"(Radio cops) here in south india yet. you Wish u were in such a place guru? (just kidding)

 

[Ziddik]

collin, so is the boost conv. Is possible to use with the TX?

 

[colin55]

You can use a much simpler circuit to convert 3v to 9v.

 

[bountyhunter]

You can use a much simpler circuit to convert 3v to 9v.

The LM2731 was designed to do this with microscopic sized components. The whole design is about 1/3 the size of a postage stamp.

 

[ronv]

Can you measure the current draw? Or, maybe since he has modeled it AG could give it to us so you would know how much the converter needs to supply.