A boost stage can be added to the output of the 3-phase, 3-switch buck to allow the output dc voltage to remain constant over a large input voltage range. In this example the input voltage range is 120Vrms to 280Vrms and the required output voltage is 400Vdc. From the graph it can be seen that at a 120Vrms input the buck system has a duty cycle of 1 and the boost converter also has a duty cycle of 0.45. As the input voltage increases the boost duty cycle decreases. At an input voltage of 230Vrms the boost converter turns off and the duty cycle of the buck converter starts to decrease. Changing of the operating point on the graph is achieved by clicking on the ‘red’ input peak voltage value and altering its value.

This applet additional calculates the current stresses and power losses of each semiconductor and the overall efficiency excluding the passive component losses. The on-state (conduction resistance and on voltage) and switching energy for the switches and diodes can be specified by clicking on the ‘red’ components.

• Change the input voltage by clicking on the ‘red’ uNR voltage value and typing a new value in the applet window that appears.
• Change the require output power level and/or output voltage.
• Change the semiconductor device parameters and observe the change in device losses and efficiency.