**Full Wave Rectifier DC Power Supply:**

Like half-wave rectifiers, full-wave rectifiers require filter circuits to convert the output waveform to direct voltage. Figure 3-13 shows a Full Wave Rectifier DC Power Supply with a reservior capacitor and a surge limiting resistor. These components operate exactly as explained for the half-wave rectifier circuit, with a few important exceptions.

The capacitor-smoothed full-wave rectifier waveforms are shown in detail in Fig. 3-14. Equation 3-7, derived for the half-wave rectifier circuit, still applies for determining the angle θ_{1}.

Also, θ_{2} can be determined from Eq.3-8,

and Eq. 3-9 can be used for time t_{2}

**Eq. 3-9**

Comparing Fig. 3-14 and Fig. 3-8, it is seen that the capacitor discharge time (t_{1}) for the half-wave circuit is approximately equal to the waveform time period (T), whereas for the full-wave circuit t_{1} approximately equals T/2. More precisely,

Using the correct value of t_{1}, Eq. 3-11 can be used for calculating the reservior capacitance for a full-wave rectifier circuit.

**Eq. 3-11,**

Similarly, (using the correct value of t_{1} in Fig. 3-14), the repetitive current (I_{FRM}) can be determined from Eq. 3-15,

**Eq. 3-15,**

The average forward current passed by the bridge rectifier circuit is equal to the load current. But, each pair of diodes supplies current for no more than a half cycle of the input wave. The other pair conducts during the other half cycle. So, as illustrated in Fig. 3-15, the diode average forward current is half of the load current.

Another difference between the half-wave and full-wave rectifier power supply circuits concerns the reverse voltage applied to the diodes. Consider Fig. 3-16. When the instantaneous input voltage is +V_{p}, as illustrated, V_{p} is applied across forward-biased diode D_{1} in series with reverse-biased diode D_{3}. Therefore, the reverse voltage across D_{3} is,

Examination of the circuit shows that Eq. 3-18 applies to each diode when reverse biased.

As in the case of the half-wave circuit, the capacitor calculation can be simplified by assuming that time t_{2} is very much smaller than t_{1}. This gives the approximation that the capacitor discharge time is equal to half the input waveform time period.