Use of NU2B "Class E" calculator

Welcome and feel free to ask questions about class E, mosfet's, and AM.
You must be registered to post.

Use of NU2B "Class E" calculator

Postby Brian K1LI » Mon May 18, 2015 8:51 pm

I have a question about the results from this program.

Using an ideal voltage-controlled switch in LTSpice, I simulated Bobby's example of a 75m KW http://classeradio.com/tools/nu2b/PushPull_KW.doc unit on the Design Tools page http://classeradio.com/tools/nu2b/nu2b_download.html of ClassERadio.com. Everything looks good, except that the full output power seems to be drawn twice - once from each DC supply - which cuts the efficiency roughly in half.

Am I looking at this the wrong way?
Brian K1LI
Member
 
Posts: 15
Joined: Fri Nov 22, 2013 5:14 am

Re: Use of NU2B "Class E" calculator

Postby Brian K1LI » Mon May 25, 2015 7:47 am

As usual, the fault lies with the operator. I didn't properly understand how to model a transformer in SPICE. For others who may want to try this, one "links" a pair of inductors - whose turns ratio is the desired impedance ratio - using the "K" SPICE directive.

For example, to achieve a factor of four (4) step up in impedance, draw two inductors with L1=1 and L2=4 (yes, that's not a misprint: no "nH" or "uH"!) and insert a SPICE directive stating "K L1 L2 1" for 100% mutual coupling. You'll notice on the schematic that phasing dots appear on each inductor to signify the "sense"; either inductor can be rotated to change the sense, as required.

This can be done with any number of inductors, not only with two.

I have not tried lower mutual coupling ratios to see how SPICE deals with leakage inductance. It's also worth noting that LTSpice adds a default 1milliohm resistance to all inductors to improve simulation efficiency.
Brian K1LI
Member
 
Posts: 15
Joined: Fri Nov 22, 2013 5:14 am


Return to Class E Discussion

Who is online

Users browsing this forum: No registered users and 1 guest

cron