some observations about this circuit SO FAR:-
(plugging in example measurements displayed for itsu's preliminary practice run)

a) the current between the supply and the circuit is bi-directional
     (confirmed using scope probe on CSR in supply lead)

b) the CSR can be considered to be resistive
     test example:  10 Ohm non-reactive, negligible phase-shift component

c) the 'supply' current is the average of the RMS current values for the 2 half-cycles
     test example: 10mA

d) Input voltage is a DC voltage, essentially constant, negligible phase shift
     test example: 3.88V DC

e) the Power In (per cycle) is the product of the static supply voltage and the RMS 'supply' current
    = 3.88 × 10 = 38.8mW

f) the positive half-cycle RMS current enters the circuit into the transistor branch
    test example: 16.08 mA

g) the total dissipative load across supply rails (per cycle) is the product of the static supply voltage, as above, and the positve half-cycle RMS 'supply' current
     = 3.88 × 16.08 = 62.4 mW

h)  the Efficiency n, for driving this load is    dissipative load / power in
      = 62.4 / 38.8  =  1.6   (or 160%)


(additional energy is dissipated in the feedback LED which, when included in the results, increases the efficiency of the circuit

Hi Itsu. Nice test. I would guess your LED power consumption measurements/calculations
are reasonably close to actual since your Tectronix scope RMS readings are probably
reasonably close, and since the current and voltage spikes across the LEDs
appear to be reasonably in phase.

However, your transistor power calculation looks quite suspect to me.
Ignoring the base current, the power consumption for the transistor should roughly be the
RMS collector to emitter voltage times the RMS collector current (assuming they are
reasonably in phase), when the transistor is conducting. The collector to emitter voltage should be quite low
when the transistor is conducting. When the transistor is not conducting, power consumption should be near 0.
Maybe you already explained it in your video, I can't watch it right now, but where are you getting that
3.912 V from? That doesn't look right to me at all.
All the best.

Thanks NP, Void,

for Void, yes i was wondering the same about that measurement, but its how NP measured it, so i did the same, but i too don't think it is the correct way.
The 3.912V i mention at the transistor is the voltage across the whole 'main led branch', so including the load led voltage etc.


In my below new setup i have changed that to as what i think is correct (voltage across E / C).



New setup using 2x 10mm white leds.
Also the 10 Ohm csr is removed.

The frequency had to be adjusted again to 130Khz by adjusting the 50K pot, its now set at 3.8K.

All measurements are done by the scope to be able to compare (backed up by the DMM's).

Current probe and voltage probes are deskewed as much as possible to rule out unwanted phase shift (important in AC like signals), but i am left with a 8ns delay (phase shift) between current and voltage probes.
This has no significant influence as shown by comparing with the 10 Ohm csr.

Below the circuit with some measurements.

The combined power users (leds and transistor) make up for a total of 21 + 1.4 + 2.3 = 24.7mW .
The input power is 28.4mW, so i think we have accounted for most of all the power into the circuit.

There are severall current measurements done, and with some i have a problem, like in the 'main led branch'.
The 9.2mA at the transistor comes short for supplying the follow on current through the load led (7.2mA) and to the feedback link to the elco (5.4mA)

Anyway, these are the results up till now:



Regards Itsu

Quote from: itsu on December 06, 2018, 01:34:42 PM
for Void, yes i was wondering the same about that measurement, but its how NP measured it, so i did the same, but i too don't think it is the correct way.
The 3.912V i mention at the transistor is the voltage across the whole 'main led branch', so including the load led voltage etc.

Hi Itsu. I see. Thanks for the clarification.
Yes, the transistor power dissipation should be relatively small, but I think it will be tricky
to measure it accurately with those pulse waveforms. 
How did you arrive at the 1.5V and 2.3 mW for the transistor?

Hi Void,

nice to have you take a look at this.

I let my scope do the hard work, by calculating the power from the voltage across the C/E and the current through this transistor.

In the above diagram, i have my yellow probe ground lead on the Emitter and the probe tip on the Collector (channel inverted on).

The current probe is at the arrow above the Emitter (also channel inverted on as my current probe is pointing the wrong way (up)).
 
The values and the math trace (yellow x green) is in the screenshot below.

Itsu