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(elec351)[2009](s)mid~PPSpider^_10326.pdf
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Name: ID No.


Chinese Name:

1
10


2
6


3
18


4
6


Total
40





The following equations may be useful:
I-V relation of C and L: ic(t) = C
v.(t) = L

VS balance: m1t1 = m2t2
Quadratic equation: ax2 + bx + c = 0 x1,2 =



(1) For (1a) and (1b), consider the following DC circuit in the steady state. 10 marks









(1a) What is the power dissipated by the resistor R? 2 marks









(1b) What is the energy stored in the capacitor C? 2 marks







For (1c) and (1d), consider the following AC circuit in the steady state.









(1c) What is the average power dissipated by the resistor R? 2 marks












(1d) What is the energy stored in the capacitor C at t = 10ms and t = 20ms? 4 marks

























(2) Converter topology 6 marks

(2a) Consider a converter that is obtained by connecting two buck 3 marks
converters, both working in continuous conduction mode (CCM), in
parallel as shown below. Derive the output voltage as a function of D
and Vg. Numerically, L1 = L2, C1 = C2. Both switches and diodes are ideal.






















(2b) For the following converter, employ volt-second balance and compute 3 marks
the output voltage as a function of D and Vg.



















(3) Consider the following current mode hysterertic buck converter that 18 marks
is designed to operate in discontinuous conduction mode. The
switch (S1) and the diode (S2) are ideal.



















(3a) Label the parameters missing in the 6 boxes above (in dotted lines). 4 marks






(3b) Briefly discuss how this converter works and regulates. 4 marks

















(3c) Sketch the inductor current i.(t) and the output voltage vo(t) along with 4 marks
the duty cycle D.















(3d) Assume that the switching period is dominated by the duration when 6 marks
both the switch (S1) and the diode (S2) are OFF, estimate the output
voltage ripple Vo and the switching frequency fs.





























(4a) Given z1 = 4 + j3 and z2 = 5 C 10j, compute z3 = z1 + z2 and express z3 2 marks
in polar form.








(4b) Given the following RL circuit. Draw the phasor equivalent circuit and 2 marks
Derive the output phasor Vo in terms of the input phasor Vs.



















(4c) For = 106 rad/s, compute the output phasor Vo in terms of its 2 marks
magnitude |Vo| and its phase
.