The main function of power supply is to convert AC to DC; as shown in fig 1, the first stage is to make full wave rectifier to the AC signals by using bridge rectifier, filter the rectified wave by using filtering capacitor and finally select the appropriate voltage regulator to generate pure DC signal.
Current rating for bridge rectifier should be suitable with load current, also; the designer should consider the voltage drop across each diode, which is normally equal to 0.7v. Note that only two diodes are required when usingcenter-tapped transformer.
The following formula is used to calculate the capacitance value for the filtering capacitor:
. . . (1)
C: Capacitor value.
Vp: Peak voltage. (“Bridge output max voltage”)
f: Frequency of the AC supply.
i: Load current.
Note that the above equation for 10% ripple voltage.