EECE 310 Homework 4, Fall 2011

American University of Beirut DEPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING EECE 310 – Electronics Fall 2011 – 2012 Due Wednesday October 26, 2011 at 9:00 am Homework 4 1. [50 points] Design a Zener voltage regulator to provide a regulated voltage of around 9 V. The available 9 V, 0.5 W Zener is specified to have a drop of 9 V at a test current of 10 mA. At this value of current rZ is specified to be 25 . The value of IZK for the diode is 2 mA. The unregulated supply varies between 10.5 V and 14 V. The regulator is required to supply a load that draws a current of 5 to 20 mA. a. [5 points] Find VZ0 for the Zener diode. b. [5 points] Find IZmax. [5 points] Find the Zener voltage when the Zener current is at IZmax. c. [5 points] Calculate the range of values for the resistor R in the circuit. d. Using a value of R that is close, to the nearest [5 points] standard 5% tolerance resistor value, to the upper range: i. [5 points] Find the change in load voltage that corresponds to the 10.5-to-14 V variation in the unregulated supply voltage. Assume that the load current is constant. ii. [5 points] Find the change in load voltage that corresponds to the full change in load current. Assume that the supply voltage is fixed. iii. [5 points] What is the maximum current that the Zener diode should be able to conduct? [5 points] What is the Zener power dissipation under this condition? [5 points] What is the worst- case power dissipation in the resistor R? 2. [25 points] Consider the waveform shown in Figure 1. Figure 1 Assume that T = 1/50 sec. This voltage is the input to a half-wave rectifier with a capacitor filter. The diode drops 0.75 V when conducting, and the load draws a constant current of 15 mA. a. [5 points] Calculate the value of the capacitor if the ripple voltage is at most 0.5 V. b. [5 points] For what fraction of the cycle does the diode conduct? c. [5 points] Find the average diode current. d. [5 points] Find the peak diode current. e. [5 points] Find the PIV for the diode. 3. [25 points] Repeat Problem 2 for the case in which the rectifier is a full-wave rectifier using a 4-diode bridge.