Second Stage Joule Thief Circuits

[guruji]

Hi Jeanna thanks for response. Yes I did a bunch of JT now ;small and 1" too but it would be a good idea to try on a bigger one with those transistors as you said.
Thanks

[resonanceman]

@resonanceman,

Yes I agree.

If you look at page 39 in this thread then you will see that is what I have designed.

Groundloop.

I read page 39   and I just read it again

I see 2 schematics  but no general explanation  of  what  the circuit does .

From what  you said on  page 39 it does not  look to me like   we are talking about doing the same thing .

If we use the +5 volt generated from the IC then it is just
enough to control a hexfet gate.

If  the  chip  will  run on 1.4 V  and   you will have 2.5 V in the cap  before  you need  to  switch caps  why do you need to control  a transistor  with  the 5V that the chip can make ?

Why not let  the switching circuit sleep  until  there is a preset voltage in  the cap .......then it can wake up   switch caps and go back to sleep .
A small  super cap could be charged on the each cycle to power  the  gates  of the  switching transistors


gary

[Groundloop]

@resonanceman,

The circuit will do the following:

The MAX856 is designed to run from a single 1,5 volt battery. This IC has a built
in detector that can detect a preset voltage level in the battery. The preset point
is set by using external resistors. This IC can also make a +5 (or 3,3) volt from
the input voltage. The low voltage detector output is a pull down transistor.
(Open collector output). This transistor can not handle great currents.

So what we do is running a pic mcu that can be triggered from this output. The pic
mcu also have an built in analog to digital converter. We use this converter to monitor
the voltage over the bcap. We need a voltage reference that is higher than the 1,5 volt
from the input battery since the bcap can reach a higher voltage than the input AA cell.

We use two powerful transistors to switch both the voltage feed back to the AA battery and
to the external load. The current through those transistors will be restricted by using pulse
width modulation. These hexfet transistor need +5 volt at the gate to trigger on.

The pic mcu will run slow on an internal oscillator. The mcu will also sleep between
operations and will wake up on interrupts from the low voltage detector and from the
a/d converter. This will ensure that the mcu uses minimum current from the AA battery.

Groundloop.

[resonanceman]

@resonanceman,

The circuit will do the following:

The MAX856 is designed to run from a single 1,5 volt battery. This IC has a built
in detector that can detect a preset voltage level in the battery. The preset point
is set by using external resistors. This IC can also make a +5 (or 3,3) volt from
the input voltage. The low voltage detector output is a pull down transistor.
(Open collector output). This transistor can not handle great currents.

So what we do is running a pic mcu that can be triggered from this output. The pic
mcu also have an built in analog to digital converter. We use this converter to monitor
the voltage over the bcap. We need a voltage reference that is higher than the 1,5 volt
from the input battery since the bcap can reach a higher voltage than the input AA cell.

We use two powerful transistors to switch both the voltage feed back to the AA battery and
to the external load. The current through those transistors will be restricted by using pulse
width modulation. These hexfet transistor need +5 volt at the gate to trigger on.

The pic mcu will run slow on an internal oscillator. The mcu will also sleep between
operations and will wake up on interrupts from the low voltage detector and from the
a/d converter. This will ensure that the mcu uses minimum current from the AA battery.

Groundloop.

Groundloop

Thank   you for the excellent explanation  of what  your circuit  does  .


gary   

 

[resonanceman]

Has anyone  bought  some 0W48740TC toroids ?

I have heard that a few people have got samples already .

I was going to order some today .

It turns out that Magnetics  has a minumum  of $25000.
They  do have  distributers  that sell  small quantities .
They  have a place on their  website that  searches  for  a part  in their  distributor inventories .
The largest  W core  I  have found  so far is 85.7 mm  OD 

The free samples  are great .......but they are kind of a dead end  if you want to make more than 1 or 2


gary