140 likes | 221 Views
Diode Applications. 1- The Half-Wave Rectifier. This diode application changes ac into dc. The voltage is most often a sinusoidal and diode is ideal. During Positive half-cycle Diode conduct (“ON”) V D =0 V o =V S During Negative half-cycle Diode conduct (“OFF”) V D =V S
E N D
1- The Half-Wave Rectifier • This diode application changes ac into dc. • The voltage is most often a sinusoidal and diode is ideal.
During Positive half-cycle • Diode conduct (“ON”) • VD=0 • Vo=VS During Negative half-cycle • Diode conduct (“OFF”) • VD=VS • Vo=0, iD=0
2- A Typical Battery Charging Circuit In the Figure • VBATTRY represents the battery to be charged
Rtotal includes all resistance (wiring, diode, battery) reflected to the transformer secondary winding. Charging current flows only when Vm sin ωt >VBATTRY. Inertia of meter movement allows indication of average current
3- The Filtered Half-Wave Rectifier • Also called a peak rectifier, a half-wave rectifier with smoothing capacitor, or a half-wave rectifier with a capacitor-input filter. In this figure
In this figure • When Vs> VL, the diode is on, and the voltage source charges the capacitor. • When Vs< VL, the diode is off, and C discharge exponentially through RL. • We define peak to peak ripple voltage Vr, as the total change in VL over one cycle.
Relating Capacitance to Ripple Voltage • Because the diode is off for nearly the entire period, T, the capacitor must supply the “dc” load current during this interval. • The charge taken from the capacitor in this interval is: • The capacitor voltage decreases by Vr in this interval, which requires a decrease in the charge stored in the capacitor
Equating these equations and solving for C gives us a design equation that valid only for small Vr:
4- The Filtered Half-Wave Rectifier • During Positive half-cycle Diode 1 is ON and diode 2 is OFF • During Negative half-cycle • Diode 1 is OFF and Diode 2 is ON
Full wave rectifier The load voltage in this case is represented as: