This example shows an ideal AC transformer plus full-wave bridge rectifier. It converts 120 volts AC to 12 volts DC. The transformer has a turns ratio of 14, stepping the supply down to 8.6 volts rms, i.e. 8.6*sqrt(2) = 12 volts pk-pk. The full-wave bridge rectifier plus capacitor combination then converts this to DC. The resistor represents a typical load.
The model can be used to size the capacitor required for a specified load. For a given size of capacitor, as the load resistance is increased, the ripple in the DC voltage increases. The model can also be used to drive an application circuit in order to assess the effect of the ripple.
Plot "Bridge Rectifier Voltages and Currents" shows how AC voltage is converted to DC Voltage. The dark blue line is the AC voltage on the source side of the bridge. There are two paths for current flow through the diode bridge. The alternating peaks through diodes 1&4 and diodes 2&3 show that current flow reaching the capacitor is flowing in the same direction even though the polarity of the voltage is changing. The ripple in the load voltage corresponds to the charging and discharging of the capacitor.