# PSPICE graphs work separately for subcircuits, wrong when combined?

I'm working on a pulse generation circuit that will be used to drive an ultrasonic transducer. The following circuit is giving an unexpected output.

It might look complicated, but really it can be divided up into smaller parts. Also, despite the wierd names for the GNDs, they are all 0/CAPSYMs. The P-type MOSFET is the pspice model SiHFU9214 provided by Vishay.

1st Part on Right: 220V DC Power Source

Verified Output at 220V DC:

2nd Part: Pulse Controller (100ns pulse at 800sps/1250us)

The Vpulse does have a 40ns PW parameter, but that is simply due to the delays of the rest of the gates.

Verified Output of 100ns pulses at the desired frequency:

Of course, the problems always arise when trying to combine different subcircuits. The probed node (1st pic) should be reading around 220V, instead I simply get this sloped line when running the simulation for 3750us.

When running the simulation for 0.200s, it gets even better.

In my understanding, this entire node should slowly be raised to 220V when the pulse signal is not activated.

But that doesn't seem to be happening. Measuring from these next nodes for current and voltage I get a little bit of information.

I'm wondering if the 60Hz frequency of the DC source, and my pulse frequency of 800Hz might be causing the 10nF capacitor to not charge correctly.

• The simulator is confused with many GNDs! Is load 50 OHM resistor? The amplitude of the power line is not 170, it is $220\sqrt{2}$. Why you don't try on N-channel mosfet? Gate drive for P-channel is better than your circuit. – M KS Nov 25 '18 at 20:35

## 1 Answer

Ok guys. I know you were all sitting on the edge of your seats waiting for a solution to my problem, but I was eventually able to figure it out solely through the power of trial and error.

IT WAS THE TRANSFORMER! I changed it to two coupled inductors like so:

And this was the result!

Oh yes... that sexy sinusoid at the top of my pulses gets me...

Anyways, I gotta go take care of some business guys. Thanks for those of you that attempted to solve it!

( ͡ᵔ ͜ʖ ͡ᵔ )