In this applet the operation of a full-bridge DC/DC converter with transformer can be observed. In addition the bi-directional magnetisation of transformer is also shown and the influence that un-symmetric switch pulses has on the transformer’s operation. If there is a un-symmetry in the voltage applied to the transformer then this causes a DC bias. If this is not removed then the transformer will go into saturation. To avoid this, a series capacitor is placed in series with the transformer. A DC voltage then appears on the series capacitor. This problem of DC bias can be safely observed using this applet by removing the series capacitor from the circuit.

• Move the red time line to observe the various current paths during the switching cycle of the full bridge converter.
• Adjust the number of transformer primary and secondary turns to change the output voltage and currents.
• Adjust the duty cycle of switches s11 and s22 to change the duty cycle of the converter.
• Adjust the symmetry of switches on time by adjusting moving the red dot on the switch waveforms s12 and s21. Observe what happens to the voltage on the series primary capacitor.
• Click on the series capacitor to remove it from the circuit. Observe what happens for un-symmetric switching waveforms as this effectively causes a DC bias on the transformer.