APPLICATION NOTE
3
Figure 3: Simple two winding Transformer
Important: You will also notice that a 1G ohm resistance R4 is added in the circuit. This resistance is required in
a simulation environment to provide reference and DC path to all nodes. In absence of this resistance, PSpice will
give a floating point error. This high value resistance effectively keeps the secondary inductance floating and
provides a DC path and a ground reference for the simulation.
Example 2: Modeling dot convention of a transformer
The bottom-right circuit in Figure 1 simulates with the exact same transformer but with reverse dot convention
from the one shown in Figure 2. In Figure 4, you will see that the output voltage of top-right circuit secondary's
winding and bottom-right circuit's secondary winding are out of phase with each other for exact same input.
Figure 4: Transformer with different dot convention
Example 3: Centre-tapped Full Wave Rectifier Transformer
In Figure 1, the bottom-left circuit is a Center-tapped Full Wave Rectifier. It is an example of various multi-winding
transformers with desired coupling.
Figure 5 shows the input and output voltage waveform of the Center-tapped Full Wave Rectifier circuit generated
using a PSpice simulation.
