# Circuit Analysis problem

Discussion in 'Homework Help' started by thelad, Nov 14, 2013.

Nov 14, 2013
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Hello everyone

Please i am preparing for my exams that is on in few days and i got stalk on this question, i attached the schematic for the question.

I will appreciate every little help on this.

Thanks

circuit parameters

VS = 24 V V0 = 15 V Vref = 2.5 V

L = 45 µH C = 47 µF R = 5 Ω

rC = 50mΩ PWM freq = 90 kHz VP = 3 V

Use standard values for all resistors and capacitors

1) Calculate the steady state duty cycle ratio, D

2) Check that inductor current is continuous and over what range of D will it be so?

3) With reference to the PWM output waveform, draw and correctly label the
voltage and current waveforms for L, C, D and the switch (neglect rC for this
section). using manual calculations to plot the waveforms.

4) Choose suitable values for Ra and Rb

5) Calculate the transfer (TF) for the Filter & Load (combined)

6) Derive the TF for the combined PWM + Switch + Filter & Load. Called the Power Converter TF (PCTF)

7) Plot, using a suitable CAD package, the frequency response (dB gain and phase) for the PCTF

8) Design a suitable compensator (compensating error amplifier) to give an overall phase margin (PM) = 45°

9) Plot and label

a) Open-loop frequency response for the compensator

b) Open-loop frequency response for the compensator + power converter (overall system)

c) Closed-loop frequency response for the overall system

d) Closed-loop step response i.e. step change in Vref .

• ###### Circuit.jpg
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Last edited: Nov 14, 2013

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