So this is what I am trying to do.

I have a 0.3 V input which I need to step up to about 3 V. As I already mentioned, the power requirements are being met even after stepping up the input for LEDs require about 0.5mW to light up but at 3 V. I have tried using many other options before I came across this. The input is DC. Can you please help me with any other option. Kind of desperate about making this project, you know

That is why I asked the question, your original statement was not clear.

So the output power is 0.5 mWatts at 3 VDC which is a current of 166 μA. I don't think you will see any light from any LED at this current level.
An 80% efficient process would require 0.5 mW / 0.8 = 0.625 mW of input power
0.625 mW of input power at 0.3 VDC is ≈ 2 mA

Do I have it correct now?

 

thanks for the answer. Since you have made it, can you kindly guide me with the dimensions of the transformer used in your circuit

Read the article

The transformer is model 952.431 made by Adastra.

Go to the website, find the datasheet, read the dimensions.

EDIT:Looks like it is no longer available, and the company website has no information. Sorry about that.

 

That is why I asked the question, your original statement was not clear.

So the output power is 0.5 mWatts at 3 VDC which is a current of 166 μA. I don't think you will see any light from any LED at this current level.
An 80% efficient process would require 0.5 mW / 0.8 = 0.625 mW of input power
0.625 mW of input power at 0.3 VDC is ≈ 2 mA

Do I have it correct now?

slightly wrong over there. The output power ( the power I can supply) is more than 100 mW at 0.3 V dc. The leds require 3 V. Standard leds would require about 3-4mW

 

Read the article

The transformer is model 952.431 made by Adastra.

Go to the website, find the datasheet, read the dimensions.

EDIT:Looks like it is no longer available, and the company website has no information. Sorry about that.

I guess, the input has to be ac for this transformer. Is it not? I have dc input

 

slightly wrong over there. The output power ( the power I can supply) is more than 100 mW at 0.3 V dc. The leds require 3 V. Standard leds would require about 3-4mW

I give up. You have explained how you're going to get from 0.3VDC to some AC voltage. What you have not explained is how you're going to get from some AC voltage to 3VDC. What I'm trying to understand is if your requirements for output power and input power are reasonable. But no matter what way I take the numbers you are feeding me it comes out wrong. So tell me, for input and output we know what the voltages are, but what amount of power and what currents did you have in mind. That's all, can you do that?

 

I give up. You have explained how you're going to get from 0.3VDC to some AC voltage. What you have not explained is how you're going to get from some AC voltage to 3VDC. What I'm trying to understand is if your requirements for output power and input power are reasonable. But no matter what way I take the numbers you are feeding me it comes out wrong. So tell me, for input and output we know what the voltages are, but what amount of power and what currents did you have in mind. That's all, can you do that?[/QUOTE
lets keep it simple . I am trying to light an led (miniature ones)
I need about 3-4 mW to light the leds
I have more then 100 mW. So power's not a problem . As far as current is concerned, you can do the calculations.
All I require is to boost my 0.3 V dc signal to 3 V dc signal (the miniature leds are rated at 3 V).
Now, you get it?

 

Like I said 0.3V DC is the confusing part

 

Like I said 0.3V DC is the confusing part

It is one thing to get a low voltage and low current oscillator working. It is altogether something else to convert that low voltage low current source into a higher voltage higher current source without an external power supply. The three laws are:

1. You can't win
2. You can't break even
3. You can't get out of the game

So I'm from Missouri and you're just going to have to show me.

 

I wanna see this too.

 

I

It is one thing to get a low voltage and low current oscillator working. It is altogether something else to convert that low voltage low current source into a higher voltage higher current source without an external power supply. The three laws are:

1. You can't win
2. You can't break even
3. You can't get out of the game

So I'm from Missouri and you're just going to have to show me.

sorry man........ I guess you don't get it even after having laid down the facts immaculately. Perhaps I could explain you in some other language. Anyways, I have found what I was looking for. You too wanna know, then here's the link.
http://www.linear.com/parametric/en...td_!2200_Thermoelectric!1032_<=0.2!1033_<=0.5

 

A "standard" white LED is about 3.3V and 20mA. This is 66mW, not 0.5mW.

Bob

 

A "standard" white LED is about 3.3V and 20mA. This is 66mW, not 0.5mW.

Bob[/QUOT

yeah, you are correct, i got that wrong initially.

 

Explaining it and doing it are obviously two different things. If you have a method, then you don't need our help.

 

RISHI HAZRA,'s comments in post #12 did display properly because of a formatting error. his text is repeated here.

The FET if J110. I do not have ferrite cores as of now. Since I haven't finalized my core dimensions yet. The circuit diagram can be found in the link posted above.

The frequency of oscillation is determined by the speed of the feedback loop. For this particular oscillator, the speed of the feedback is determined primarly by the inductance of the transformer T1 primary 15, the gate to source capacitance C3 of the field effect transistor Q1, and to a lesser extent the drain to source capacitance C2 of the field effect transistor Q1.

Yeah I am gonna pass the ouptput voltage of the secondary through a rectifier in order to light the leds

I suggest that you choose a frequency near 50 kHz as a comfortable tradeoff between core size and overall efficiency.

Since you only need an output of 100 milliwatts or less, you can use as small a core as you are comfortable handling.

As an example, I use a flashlight daily that uses a single 3 mm ferrite bead to boost 1.5V to 4V for a white LED.

 

thanks for the answer. Since you have made it, can you kindly guide me with the dimensions of the transformer used in your circuit

I don't have it to hand - it was literally a case of I found it hard to believe that an oscillator would work at 10s of mV, so I grabbed a FET and a toroid, wound a few turns and hooked it up. In 10mins I could see that it worked, made a few measurements and have never seen it again.

I could possibly rummage through my junk to find it, but I think it would be a very poor way to start your design. Making a reasonable job of powering an LED from 300mV from scratch would test many seasoned operators with expertise in DC-DC converters (of which I'm not), but getting it to work well probably requires some understanding of the operation of the circuit, at least to the level of being able to specify the main characteristics of the transformer.

Alternatively, you could look at what the experts have done:

If I read it correctly the LTC3108 can produce nearly 2mA at 4.5V from 300mV http://www.linear.com/product/LTC3108
This would have met your 0.5mW requirement, but I see from later posts that you now want more power.

Freescale promised something here that looks impressive, but I can't see it in their product lineup, but you may have more time to search:
www.freescale.com/files/training_pdf/VFTF09_AZ149.pdf

 

I don't have it to hand - it was literally a case of I found it hard to believe that an oscillator would work at 10s of mV, so I grabbed a FET and a toroid, wound a few turns and hooked it up. In 10mins I could see that it worked, made a few measurements and have never seen it again.

I could possibly rummage through my junk to find it, but I think it would be a very poor way to start your design. Making a reasonable job of powering an LED from 300mV from scratch would test many seasoned operators with expertise in DC-DC converters (of which I'm not), but getting it to work well probably requires some understanding of the operation of the circuit, at least to the level of being able to specify the main characteristics of the transformer.

Alternatively, you could look at what the experts have done:

If I read it correctly the LTC3108 can produce nearly 2mA at 4.5V from 300mV http://www.linear.com/product/LTC3108
This would have met your 0.5mW requirement, but I see from later posts that you now want more power.

Freescale promised something here that looks impressive, but I can't see it in their product lineup, but you may have more time to search:
www.freescale.com/files/training_pdf/VFTF09_AZ149.pdf

thanks a lot............. will try both of them.