Re: Coupling vs secondary voltage chart

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:
> Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>
> Hi Antonio,
> The problem I ran into was knowing "NewVin" in the case of a primary 
> current controlled DRSSTC.  In order to know NewVin, I would have to know 
> NewIprimary ( Xo[4}(t+dt) ) which I will not have until the simulation 
> cycle ends.  The NewVin is controlled by the primary current 
> NewIpri.  When the cycle starts, I don't know what NewIpri will be.
> So I set the NewVin equal to the LastVin.  This will cause Vin to actually 
> switch one cycle later.  But that really is the case in a real DRSSTC 
> since the electronics take time to switch.

The problem is not in the calculation of Vin based on the last
calculated current. I agree that this is a reasonable approach.
The problem is that by always using Vin+Vin, at each transition
a sum that should be zero goes to a full sum.
Consider what this means, in a transition from -Vin to +Vin at t0+dt:
Vin(t0)+Vin(t0+dt) should be 0. You are using 2*Vin, what is
equivalent to say that Vin(t0+dt)=2*Vin.
Continuing, Vin(t0+dt)+Vin(t0+2*dt)=2*Vin means that Vin(t0+2*dt)=0
Continuing, Vin(t0+2*dt)+Vin(t0+3*dt)=2*Vin means that Vin(t0+3*dt)=2*Vin.
The input voltage is then oscillating between 0 and 2*Vin at each step.
The oscillation gets worse at each transition. This has little effect
in the simulation, however, as the high-frequency component is rejected
by the relatively narrowband circuit (and by the simulation method).

Antonio Carlos M. de Queiroz