Exam text content

 

 

7 Tampere University of Technology —DEE-34106 Converter dynamics and EMC 19.5. 2015
Electrical Engineering

Teuvo Suntio

Ouestion 1.

Ouestion 2.

Ouestion 3.

Ouestion 4.

Fig. 1.

Fig. 2.

Programmable calculator allowed 5 guestions/ & 6 pts

Explain shortly the following concepts related to the dynamics of a switched-mode converter
(Note: Repeating the English words does not suffice): a) SSA method, b) two-port model, c)
state space, d) PI, e) PCM-control, and f) DDR-control. (ä 1pt)

Fig. 1 shows an electrical eguivalent circuit representing the dynamies of a certain class of
switched-mode converters. Define symbolieally based on Fig. 1 a) Z,,,b) Z:n,» and €) 77,
(Each subguestion gives 2 pts).

 

A control-block diagram representing a generalized closed-loop input dynamics of an input-
side-controlled converter is given in Fig. 2. a) Define the eguation for the feedback-loop gain
(L) using the symbols of Fig. 2, b) Define symbolically the closed-loop Jin / Vn» ANd €)

Define symbolically j., /%., . (Bach subguestion gives 2 pts)

 

 

 

 

 

 

 

 

 

 

 

  

 

 

 

 

Closed loop

 

The freguency responses of the control-to-output-voltage transfer function (G,,,) and the

output-voltage-feedback loop gain (L, ) of a buck converter are shown in Fig. 3a, and Fig.
3b, respectively.

a) Compute the approximate value of the output capacitor of the converter when its output
inductor is 400 uH? (2pts)

b) Evaluate the feasibility of the control design based on Fig. 3b: Why it is /Why it is not?
(2pts) :

c) What is the type of the used controller? 1, P, PI, PID? Justify your answer! (2pts).

E)
 

Tampere University of Technology — DEE-34106 Converter dynamics and EMC 19.5. 2015
Electrical Engineering

 

   

Teuvo Suntio Programmable calculator allowed 5 guestions/ ä 6 pts
Open-Loop Bode
EZ o
o
D
2
E -50
=> TEI
3 |snn
Stable loop
100

 

Phase (deg)
8

 

  
 
      

 

 

 

 

    

-180 - 4 :
10" 10? 10? 101 10? 10
Freguency (Hz)
Fig. 3a.
Closed-Loop Bode
100. —; r a
3 50
S
5 0
se
oD :
E 505 6:16888
Frea: 1.138+003 Hz
Stable loop ii
-100 sidni a
45 -T
5 90
v
= 35
ä
E 4180
E -
-225 i mnt Tiidik m mä ankkaa] än kääk
10" 10? 10? 10! 10 10
Freguency (H2)
Fig. 3b.

Ouestion 5. — The measured open-lo0p (Zin) closed-loop (Z.) and short-circuit (Zio) NPUt
impedances of the output-voltage-feedback-controlled converter as well as the output
impedance (Z,) of the input EMI filter are given in Fig. 4. Analyze the effect of the input
filter on a) the stability of the converter, b) load-transient responses, and c) voltage-loop
gain. Without the input filter, the converter is stable and the transient performance is
excellent. Justify your thoughts based on Fig. 4 and the underlying formulas. The value of
each sub-guestion is 2 points.

23)
 

 

Tampere University of Technology — DEE-34106 Converter dynamics and EMC 19.5.2015

Electrical Engineering
Teuvo Suntio Programmable calculator allowed 5 guestions/ & 6 pts
1+2.1/7, 1+Z,/Z k L
s = 1+ 253) Fino s = 1+ 45! Finso 7 nej my

 

mA =.  C=C0———0<sc

 

>
ö

 
 
  
  

w
o o

 

W
o

Magnitude (dB2)

 

 

 

Phase (deg)

 

Freguency (Hz)

Fig. 4

3(3)