Is joule thief circuit gets overunity?

[poynt99]

Lawrence,

The CSR wave form is a varying DC, and it DOES have an average DC value, which is what we want the meter to tell us.

It is telling us that you are using an average of 16mA supplied to the circuit, and that the average input power is 10.56mW.

I'd say that is very much in the ball park.

[ltseung888]

Lawrence,

The CSR wave form is a varying DC, and it DOES have an average DC value, which is what we want the meter to tell us.

It is telling us that you are using an average of 16mA supplied to the circuit, and that the average input power is 10.56mW.

I'd say that is very much in the ball park.

@poynt99:

I expanded the Input waveform diagram for you.  It is clear that the Iin values crossed the zero axis.  Thus it cannot be treated as varying DC.  It is not a perfect AC.  It is the "pulsed wave" with both positive and negative values.  The Vavg is the -8.80mV as indicated on the Scope and NOT the 16mV on the meter.

We have to rely on the formula:

Instantaneous Power = Instantaneous Voltage x Instantaneous Current

and use EXCEl on the sample points to get the correct Pin. 

[gedfire]

Hi All,

I read throught this webpage and found this piece of research eye opening.Notice amp drop and increase in frequency.I would also want to know about the duty cycle too.

http://www.talkingelectronics.com/projects/LEDTorchCircuits/LEDTorchCircuits-P1.html

Ged

[picowatt]

Lawrence,

It would be wise to check the DC offset of your scopes.

A simple test for this would be to connect all probe tips directly to their ground clips and then set all input channels to 20mV per division sensitivity.

Set the scopes to trigger on "line" and see what your scopes' DC measurements are.  All channels should measure zero volts DC.


Also, do you you always use the same scope to measure input and the same scope to measure output?

Have you ever swapped the scopes to confirm your measurements are consitent regardless of which scope measures input or output? 
 
PW

[picowatt]

Lawrence,

Having read back a bit, I see .99 previously asked about your scope offset.

Could you post the raw data of your scope offset tests?   

The raw data for slide 13 shows your LED drawing 12ma when only 80mv is applied to it.  One would expect the LED current draw to be much less than that with 80mv applied.

PW