This forward converter developed by ON Semiconductor is based on the NCP1028 controller, available in the Multisim database. NCP1028 is a high-voltage switching regulator for medium power offline switched-mode power supplies (SMPSs). This circuit provides 12 V output up to 2 A peak output current over the entire universal input range (90 to 265 VAC). This performance makes it suitable for almost any application that involves power supply design.
You can learn more about the technical design details in ON Semiconductor application note AND8489/D.
The following models of power components in Multisim were used in the design:
Figure 3 is a snippet of the design.
Figure 3. 12 V AC to DC Forward Converter Schematic
An alternative way of learning about the transient response of this circuit is by running an interactive simulation. This allows you to vary the value of different interactive components (for example potentiometers etc…) on the schematic and viewing how the response is affected while the simulation is running. Different response types could be evaluated using different instruments such as the oscilloscope, the bode plotter, or the DMM.
Figure 4. Measured Transient Response on the Built-In Virtual Oscilloscope Instrument of Multisim
As the above oscilloscope measurement shows, an AC input voltage of 180 V peak amplitude is regulated to a DC level of 12 V. The setting time of this regulator circuit is less than 10 ms. You can perform further advanced analyses to evaluate the ripple level of the DC output, the efficiency of the circuit, and the sensitivity of the circuit to parametric variations. The non-ideal RLC and the configurable transformers help to accurately model all of the parasitic effects while the SPICE model of the switching control provided by ON Semiconductor almost guarantees the alignment of this simulation with a fabricated physical prototype.