Power Supply for Jim Williams Pulse Generator

[Bryan]

Hello:

Would someone mind looking over the schematic for the power supply for the Jim Williams Pulse Generator. I am wondering what size of inductor is needed?. Was thinking of using a single 1.5v cell.   Cheers

http://www.kerrywong.com/2013/05/18/avalanche-pulse-generator-build-using-2n3904/

[Warhawk]

Hi, on the picture below the schematic diagram there is TV1415-B inductor used.
It should be 22uH 2.5 inductor.

It is a strange coding explained here: http://electronics.stackexchange.com/questions/50582/help-reading-inductor-label

Cheers
Jiri

[Bryan]

Thanks, I wonder if the inductor value is dependent on the input voltage. The author used a 4.5v supply where I wanted to use 1.5v. Maybe it doesn't matter?.

[Warhawk]

Thanks, I wonder if the inductor value is dependent on the input voltage. The author used a 4.5v supply where I wanted to use 1.5v. Maybe it doesn't matter?.

Let's have a look at it. It is a step-up converter with boosted output. In general, the energy calculation for one period is:
(Energy-in) / (efficiency) = Energy-out
Energy-in is stored to the inductor only during t_on phase.

E_in=1/2*L*I_peak^2

and also I_peak = V_in*t_on/L

Combining those two formulas gives me

Ein=V_in²*t_on²/2*L

Long story short, low input voltage must be compensated by longer t_on or smaller inductor to keep output energy (power) constant. The IC chip by himself can work from 1.1V.
If I were you I would start with the specified inductor.

I Better wondering why author took feedback from the first stage and not from the output like Jim previously did.

[Bryan]

He explains in the blog as to the reasons why.

 Note that in Jim’s original HV circuit with LT1073, the feedback resistor was located at the HV output of the voltage multiplier, whereas in my circuit I left the feedback point at the primary output and leaving the multiplier voltage unregulated. The reason for this decision is that should R2 become unconnected the voltage input to the feedback pin will remain be within tolerance, avoiding any possible damage to the chip. Also, since the current requirement for the avalanche pulse generator is very low, regulating the HV output is not strictly necessary.

[Warhawk]

I should have read it first
Thanks