Presentation on theme: "TUTORIAL 3 Q1 Draw and label a block diagram the elements of a DC power supply which receives an input from the 240 V; 50 Hz mains and produces an output."— Presentation transcript:
1TUTORIAL 3Q1Draw and label a block diagram the elements of a DC power supply which receives an input from the 240 V; 50 Hz mains and produces an output of regulated 5 V DC. Describe briefly the function of each element. Illustrate your description with suitable figures.
6TUTORIAL 3 SOLUTION (cont’d) Function of each element Smoothing circuit, also known as filter, minimizes the ripples appearing in the voltage waveform at the output of the rectifier. The output of this circuit is as smoothened waveform as in the following figure.
8TUTORIAL 3 SOLUTION (cont’d) Function of each element Regulator maintains a constant output DC voltage (within certain percentage) despite variations, within certain limit, in either the line voltage (VAC), load or both.
9TUTORIAL 3Q2Explain the following terms as applied to a voltage regulator;a) line regulationb) load regulation
10TUTORIAL 3SOLUTIONa) Line regulation as applied to a voltage regulator is a measure of its ability to maintain a constant output voltage despite variation in the input voltage. It is the change of output voltage per unit change in the input voltage and is normally expressed in percentage form, thus;
11TUTORIAL 3 SOLUTION (cont’d) b) Load regulation as applied to a voltage regulator is a measure its ability to maintain a constant output voltage despite variation in the load connected its terminal, and is normally express in percentage form, thus;
12TUTORIAL 3Q3The output voltage of a regulator is 30 V when not connected to any load. The rated maximum output current of the regulator is 1 A. It was found that output voltage at the maximum output current was 29.4 V. Determine the load regulation of the regulator.
14TUTORIAL 3Q4A voltage regulator is rated at a nominal output voltage of 12 V for the corresponding input voltage of 20 V. It is found that its output voltage decreases to V when the input voltage decreases to 16 V. Determine the line regulation of the regulator.
18TUTORIAL 3Q6The regulator in the following figure is to produce a nominal output voltage, Vo = 18.6 V and a maximum load current IL(max) = 1 A. It is known that , the zener diode current IZ shall not drop to less than 15 mA, the current I1 = 1 mA and the input voltage Vi may vary between 22 V to 30 V. Determine the values of R1, R2 and R3.
24TUTORIAL 3 Q7 For the shunt regulator shown in the following figure; a) find Vo;b) if IL and Vo are constant, find the change in IC1 if Vi changes by 1 V;c) if the maximum input voltage Vi = 25 V, find IL if the load resistance, RL is shorted
27TUTORIAL 3 SOLUTION (cont’d) b) If IL and Vo are constant, I3 will also be constant. Hence;
28TUTORIAL 3SOLUTION (cont’d)c)When RL is shorted, Vo = 0. Therefore;
29TUTORIAL 3Q8Describe the operation of the following regulator;
30TUTORIAL 3SOLUTIONIf the load resistance RL suddenly decreases, the output voltage Vo will also decrease. The decrease in Vo will be followed by a decrease in V4. The output of the op-amp VOA decreases because VOA = AO(V4 – VZ) and VZ being constant.
31TUTORIAL 3 SOLUTION (cont’d) The drop in VOA reduces the VBE bias voltage of Q1 and hence reduces IC1. The reduction in IC1 means more of IR1 can flow through RL and thereby increases the output voltage Vo. This increase compensates for the previous drop in Vo.