Simulating is a big part of design verification, so this post will deal with creating a model of an open loop synchronous buck converter using MATLAB and Simulink, which can be used to perform transient analysis. The equations governing the operation of a synchronous buck converter shown in fig. 1 are:
Modelling such a converter using Simulink is quite simple. As shown in fig. 2, the input to model are:
Whereas the outputs of the system are:
Voltage across the load,
Click my_syncbuck_ol to download the simulink model file, then change the file extension from .pdf to .mdl. From the top level view shown in fig. 3, you can change the values of input voltage, duty cycle, and load resistance according to your system parameters.
Double clicking on the “Buck converter – open loop” block opens up another window with two more subsystem blocks. Clicking on any of these subsystems will allow you to change their respective parameters. In order to access the underlying lower levels, right click on the block and select “Look under mask” from the menu.
- PWM Subsystem:Allows you to change the switching frequency as well as the amplitude of the PWM ramp signal.
- Buck converter Subsystem: Allows you to change the values for inductance and capacitance, along with their parasitic resistances. This is the block where we implement the system equations described earlier.
Once you have all the parameters setup, you can run the simulation. Fig. 7 shows a screenshot of the simulation result, which can be accessed from the scope block located in the top level view.