5 to 12 was bad enough. Now it is 1 to 12?

A valuable lesson to learn for a designer is to know what a circuit can do. Anyone designing for 3V output from 1 to 12V input would immediately reject a shunt regulator because it cannot do that.

 

The IC in a Solar Garden Light boosts the 0.9V to 1.5V from a rechargeable Ni-MH battery cell to 3.5V for a colored LED.
You might be able to copy the circuit in the cheap IC with many transistors.

Anything without ics?? Use inductors transistors capcitors etc etc

 

To boost converter be effective at 1V Vin you need a Bjt with very low Vce_sat. Even 100mV Vce drop causes 10% waist. I usually parallel more bjt-s so every of them carry portion of overall current only.
To design a boost with simple feedback just 2 bjt are needed, one for switching and one as comparator.

 

To boost converter be effective at 1V Vin you need a Bjt with very low Vce_sat. Even 100mV Vce drop causes 10% waist. I usually parallel more bjt-s so every of them carry portion of overall current only.
To design a boost with simple feedback just 2 bjt are needed, one for switching and one as comparator.

Can you give circuit of what your saying? I never seen that

 

Similar to this, but can be done much better. The 3055 is one of worst bjt for this. An auxiliary winding on inductor is used for driving the bjt.

 

Similar to this, but can be done much better. The 3055 is one of worst bjt for this. An auxiliary winding on inductor is used for driving the bjt.

Won't work with 2N7000.
The TS wants a 1V-12V input supply.

 

Won't work with 2N7000.
The TS wants a 1V-12V input supply.

What parameter of 2n7000 is not sufficient?
It’s not my schematic, I just wonder.

 

Similar to this, but can be done much better. The 3055 is one of worst bjt for this. An auxiliary winding on inductor is used for driving the bjt.

Can you go in detail and explain your circuit how it works, all values of component how they are calculated, what is 1:1 equipment, what is arrow pointing to 100k ohms resistor, why are all the equipment needed and shown? Please also incoming voltage i have baries from 1vdc to 15vdc. You dont have 1vdc to 15vdc you just have 1.5vdc.

thanks

 

What parameter of 2n7000 is not sufficient?
It’s not my schematic, I just wonder.

VGS(th) can be as high as 3V.
1v won’t turn it on.

 

This circuit naturally starts oscillate due to positive feedback between coil windings.
When the voltage across coil (right winding) is positive the voltage on auxiliary winding (left winding) is positive also in way it pushes current to base.
Once the coil cannot be charged anymore because of bjt Beta the both voltages changes orientation so right winding supplies the cap+load and left winding holds base Off and bjt Off also. This repeates forewer.

And how the 1.5V input is boosted to example 6V? Principally, When you rapidly disconnect a charged coil the voltage across coil changes orientation and huge voltage spike (even 100V is possible) is developed across coil. This huge voltage spike is catch to output cap thru diode.

Note: The mosfet ensures a regulation feedback to maintain Vout constant and for basic functionality (without regulation) is no needed.

 

VGS(th) can be as high as 3V.
1v won’t turn it on.

The gate of 2n7000 senses output voltage that should be constant 3V if I understand hhsting correctly. Or even more and use linear stabilisation after. So 2n7000 should work I think. But anyway, I would rather make a better comparator than just Vgs of mosfet.

 

The gate of 2n7000 senses output voltage that should be about 3V if I understand hhsting correctly. So 2n7000 should work I think. But anyway, I would rather make a better comparator than just Vgs of mosfet.

Lowest input should be 1v not 1.5v

 

This circuit naturally starts oscillate due to positive feedback between coil windings.
When the voltage across coil (right winding) is positive the voltage on auxiliary winding (left winding) is positive also in way it pushes current to base.
Once the coil cannot be charged anymore because of bjt Beta the both voltages changes orientation so right winding supplies the cap+load and left winding holds base Off and bjt Off also. This repeates forewer.

And how the 1.5V input is boosted to example 6V? Principally, When you rapidly disconnect a charged coil the voltage across coil changes orientation and huge voltage spike (even 100V is possible) is developed across coil. This huge voltage spike is catch to output cap thru diode.

Note: The mosfet ensures a regulation feedback to maintain Vout constant and for basic functionality (without regulation) is no needed.

I still dont understand. How did you get capacitor, resistor values? Can you actually show examples of how 3vdc is produced from 1.5vdc? What is the purpose of diode, all resistors, capciators? How is voltage turned on and off??? You show 1:1 is that inductor or transformer? If inductor then what is the size?

 

I still dont understand. How did you get capacitor, resistor values? Can you actually show examples of how 3vdc is produced from 1.5vdc? What is the purpose of diode, all resistors, capciators? How is voltage turned on and off??? You show 1:1 is that inductor or transformer? If inductor then what is the size?

Try study a boost converter first:
https://en.m.wikipedia.org/wiki/Boost_converter


Then self-oscillated joule thief:

https://en.m.wikipedia.org/wiki/Joule_thief

 

Try study a boost converter first:
https://en.m.wikipedia.org/wiki/Boost_converter
View attachment 323327

Then self-oscillated joule thief:

https://en.m.wikipedia.org/wiki/Joule_thief

Read it. Went back to your circuit but its hard to tell which side is positive and which one is negative, which transistors are on or of in cut off or saturation exactly. Is it possible you can go thru and explain it? Please

 

Forget about mosfet for now. You can even remove it. All switching do a 2n3055 bjt.
If dot of right winding is positive the dot of left winding is positive also.

 

Look the datasheet of tl431 how a bandgap refference can be performed with transistors. But be ready for very hard study and matching transistors, another words you probably don’t get it.

Building a precise reference is a big topic. Once I reached 1% at 3V output (not a bangap type) and it was true challenge.

Most easy is supply a zener with constant current. You should reach about 2% accuracy at varying Vin voltage (5-12V), but not a temperature compensation:

I dont get how voltage across 100 ohms is 0.6v?

i get 5v-0.6-0.6+0.6+vr =o

vr = 5-0.6???

 

Look Kirchhoff voltage law for this circuit:

 

Look Kirchhoff voltage law for this circuit:

View attachment 323453

Ahh yes the +5vdc is not in that loop

 

Copy the highlighted text.
Paste it as a command on your schematic.

Excuse me - but to what "highlighted text" are you referring??