Question

you will analyse circuits using the circuit simulation software QUCS (Quite Universal Circuit Simulator, you can download QUCS from http://qucs.sourceforge.net/index.html).

In QUCS you build your circuit by creating a schematic of the circuit through a graphical user interface. In the same graphical user interface you also define what simulations to be performed and in the lab you will use DC, Transient and ac simulations. After the simulation is finished you can display the simulation results in the same graphical interface.

Task 2: Perform Transient simulation of a rectifying circuit using a diode and a capacitor. The circuit has a sinusoidal (AC) input voltage that the circuit should convert into a constant voltage i.e. a DC voltage. Analyse and show how well the circuit delivers a constant voltage and what the constant voltage is.

Task 2: Analysis of a rectifying diode circuit Perform a transient simulation from t=0 s to t=20 ms of the circuit containing a diode below. The circuit has a sinusoidal AC voltage source with an amplitude of 5 V and a frequency of 220 Hz. The diode is 1N4148 and can be find in the Libraries/Diodes in QUCS. The circuit is designed to convert a varying (AC) sinusoidal voltage into a constant positive voltage (DC) over a load. The resistor Ru=1 k represents the load. + Ri=1 k92 D5 VAC ~ > (A) Analyse how well the circuit converts the AC sinusoidal voltage into a positive DC constant voltage over load resistor RL. The conversion from AC to DC can be improved by adding a capacitor in parallel with the load as depicted in the schematic below. 4 + - (D 5 VAC - CE R=1 k2 < (B) Analyse how well the circuit converts the AC sinusoidal voltage into a DC constant voltage over load resistor R, when C=10 uF. Vary C and Rį and describe how the AC to DC conversion is affected.

Answer 1

Simulation 1:

- Qucs 0.0.19 Eile Edit Positioning Insert Project Tools Simulation View Help EE99 of ex ea ..R 13 Main Dock x q.sch & q.dpl X 17 / temam diagrams Projects Cartesian Polar . . . . . . . . . Content . . . . D 1 . . ... Vj=0.7. V. .. .. .. . Tabular Smith Chart Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Admittance... Polar-Smith... . + 1 1 . U5 V T-. . . . . . R=1000 Ohm ..Pr . . . . . . . . . . . . . . . . . . . Libraries Smith-Polar... 3D-Cartesian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lu. . . Locus Curve Timing Diag... transient simulation . . • • • • • • • • • • • • • • • • • • • • • • • • . • • • • • • • • • • . . . ... 910 Truth Table . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . • .. TR1 . • T R 1 . . Type=lin . . Start=0 . : . . : . . : . . : . : . : . : . : . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ston=20 m s . . . . . . . . . . Search Components Clear no warnings 112: 214 7:36 AM ) 519/2020 ^

Result:

- Qucs 0.0.19 Eile Edit Positioning Insert Project Tools Simulation View Help EE99 of ex ea ..R 13 Main Dock 8x q.schq .dpl 17 / temam diagrams Projects 4.5+ Cartesian Polar Content Tabular Smith Chart Components Admittance... Polar-Smith... Pr1. Vt Libraries Smith-Polar... 3D-Cartesian Locus Curve Timing Diag... ook -0.07 0.002 0.004 0.006 0.008 0.01 time 0.012 0.014 0.016 0.018 0.62 Truth Table Search Components Clear no warnings 79:373 7:36 AM ^ '- 74 5/9/2020 W

Simulation 2:

- Qucs 0.0.19 Eile Edit Positioning Insert Project Tools Simulation View Help EE99 of ex ea ..R 13 Main Dock x q.sch & q.dpl X 17 / temam diagrams Projects Cartesian Polar : . .: . . . . D 1. Content . ... Vj=0.7. V. .. .. .. . Tabular Smith Chart Components . . . . . . . . . . . . . . 111 . . . . . . . . . 12 ..Pr . Admittance... Polar-Smith... . U5 V 1-. . 1 . LR1 : : : : C=10 uF R=1000 Ohm . . . . . . . . . . . . . . . . . . . . . . . . Libraries . . . . . . . . Smith-Polar... 3D-Cartesian . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . lu. . . Locus Curve Timing Diag... transient simulation . . . . . . . . . . . : : : : : : : : : : : : : . : : : : : : : : : : 910 Truth Table . : : : : TR1 .::· Type=lin . . . . Start=0 .. . . ......... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ston=20 m s . . . . . . . . . . Search Components Clear no warnings 463 : 253 7:37 AM - 9 4) 519/2020 ^

Result:

- Qucs 0.0.19 Eile Edit Positioning Insert Project Tools Simulation View Help EE99 of ex ea ..R 13 Main Dock 8x q.schq .dpl 17 / temam diagrams Projects 4.5+ Cartesian Polar Content Tabular Smith Chart Components Admittance... Polar-Smith... Pr1. Vt Libraries Smith-Polar... 3D-Cartesian Locus Curve Timing Diag... ook -0.57 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0018 time 0.02 Truth Table Search Components Clear no warnings 272: 118 2 1 519/2020 ♡ ^ 4

Increasing Capacitance to 50 uF:

- Help Qucs 0.0.19 Eile Edit Positioning Insert Project Tools Simulation View E9J3 of texta.. Main Dock 8x q.schq .dpl ) 14 ore at OM diagrams Projects 4.5+ Cartesian Polar Content Tabular Smith Chart Components Admittance... Polar-Smith... Pr1. Vt Libraries Smith-Polar... 3D-Cartesian Locus Curve Timing Diag... 910 Truth Table -0.57 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0018 time 0.02 Search Components Clear no warnings 530 : 253 7:37 AM A = ? )) 5/9/2020

Increasing Capacitance to 100 uF:

- Help Qucs 0.0.19 Eile Edit Positioning Insert Project Tools Simulation View E9J3 of texta.. Main Dock 8x q.schq .dpl ) 14 ore at OM diagrams Projects Cartesian Polar Content Tabular Smith Chart Components Admittance... Polar-Smith... Pr1. Vt Libraries Smith-Polar... 3D-Cartesian Locus Curve Timing Diag... ook -0.57 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0018 time 0.02 Truth Table Search Components Clear no warnings 718 : 336 7:37 AM A 39 4) 5/9/2020

Increasing Capacitance to 1 mF:

- Help Qucs 0.0.19 Eile Edit Positioning Insert Project Tools Simulation View E9J3 of texta.. Main Dock 8x q.schq .dpl ) 14 ore at OM diagrams Projects 4.5 + Cartesian Polar Content Tabular Smith Chart Components Admittance... Polar-Smith... Pr1. Vt Libraries Smith-Polar... 3D-Cartesian Locus Curve Timing Diag... ook -0.07 0.002 0.004 0.006 0.008 0.01 time 0.012 0.014 0.016 0.018 0.62 Truth Table Search Components Clear no warnings 705 : 215 7:38 AM 4) 519/2020 ^°

From all the simulation results you can clearly see that as we increase the amount of capacitance of the capacitor, the amount of the ripple about the dc rectified output is decreasing, which means AC to DC conversion is improved.