Study with the several resources on Docsity
Earn points by helping other students or get them with a premium plan
Prepare for your exams
Study with the several resources on Docsity
Earn points to download
Earn points by helping other students or get them with a premium plan
Material Type: Notes; Professor: Erickson; Class: Renewable & Power Electronics Laboratory; Subject: Electrical & Computer Engineering; University: University of Colorado - Boulder; Term: Unknown 1989;
Typology: Study notes
1 / 19
This page cannot be seen from the preview
Don't miss anything!
1
Experiment 4 part 2:
flyback feedback loop
12 VDC
HVDC: 120 - 200 VDC
AC load120 Vrms60 Hz
Battery
DC-ACinverterH-bridge
DC-DCconverterIsolatedflyback
-^ + d(t) Feedbackcontroller
Vref^
d(t) Digitalcontroller
2
Right now:Prelab assignment for Exp. 4 Part 1 (one from every student)Due within
five minutes of beginning of lecture This week in lab (Feb. 26-28):De
finitely
finish Exp. 3, and begin Exp. 4 Next week in lecture (Mar. 4):Prelab assignment for Exp. 4 Part 2 (one from every student)Next week in lab (Mar. 4-6):Exp. 3
final report due
ECEN 4517
4
Introduction: the need for feedback
Output voltage of aswitching converterdepends on duty cycle d , input voltage
v^ , and g load current
i^ .load^
+–
v(t)g
Switching converter
Load
Pulse-widthmodulator
v(t)c Transistorgate driver δ(t)
i(t)load
δ(t)
T^ dT t^ ss
v(t)
v(t)g i^ (t)load d(t)
Switching converter^ v(t)^ = Disturbances^ } Control input}
5
Negative feedback:a switching regulator system
7
Bode plot: control-to-output transfer functionbuck-boost or
flyback converter example
f
0 ˚ –90˚ –180˚ –270˚
||^ G^ ||vd^ G = 187 Vd^0 ⇒^ 45.5 dBV ||^ G^ ||^ vd^
∠^ Gvd
80 dBV60 dBV40 dBV20 dBV^ 0 dBV –20 dBV–40 dBV
Q^ =^4 ⇒
12 dB fz 2.6 kHzRHP
∠^ G^ vd
-1/2Q^10 f (^0) 1/2Q^10 f^0 0 ˚^
300 Hz 533 Hz
–20 dB/decade
–40 dB/decade
–270˚
f^ /10z^ 260 Hz
10 f^ z 26 kHz
1 MHz
10 Hz^
100 Hz^
1 kHz^
10 kHz^
100 kHz
f^0 400 Hz
8
+–
vg
Switching converter Powerinput^
Load –+ Compensator
vref Referenceinput
Hv
Pulse-widthmodulator
vc
Transistorgate driver
δ^
G^ (s)c
H(s) Errorsignal^ ve
Sensorgain iload
M
= pk-pk amplitude of PWM sawtooth
10
Example: a loop gain leading toa stable closed-loop system^ T(j
f^ )^ = – 112 c^
= 180 m^
Crossoverfrequency^ fc
60 dB 40 dB 20 dB^ 0 dB –20 dB–40 dB
f fp^1
fz
||^ T^ ||
0 ˚ –90˚ –180˚ –270˚
ϕm
∠^ T
∠^ T
||^ T^ ||
1 Hz^
10 Hz^
100 Hz^
1 kHz^
10 kHz^
100 kHz
11
Example: a loop gain leading toan unstable closed-loop system^ T(j
f^ )^ = – 230 c^
= 180 m^
Crossoverfrequency^ fc ˚
60 dB 40 dB 20 dB^ 0 dB –20 dB–40 dB
f fp^1 f
p^2 ||^ T^ ||
0 ˚ –90˚ –180˚ –270˚
∠^ T
∠^ T
||^ T^ ||
ϕ(< 0)m^
1 Hz^
10 Hz^
100 Hz^
1 kHz^
10 kHz^
100 kHz
13
0 °^ 10 °^
20 °^
30 °^
40 °^
50 °^
60 °^
70 °^
80 °^
90 °
ϕm
Q
Q^ =^1 ⇒
0 dB^ Q^ = ϕ= 52˚m^ 0.5^ ⇒^ –6 dB
ϕ= 76m^
˚
20 dB15 dB10 dB5 dB 0 dB –5 dB–10 dB–15 dB –20 dB
14
+12V– + –12V^
3.9 V
Converter
vout
Vref
to pin 2of UC352510 kΩ
Integral controllerNext prelab:Select compensator element values (ECEN 4517)Design feedback loop (ECEN 5517) possibly with more complexcompensator
ECEN 4517
16
L^ M
Vg
Q^1 1:n^ D^1 C Transformer modeli ig
R
Ll + v–l^
-^ Leakage inductance
imperfect coupling of primary andsecondary windings• Leakage inductance is effectively inseries with transistor
-^ When MOSFET switches off, itinterrupts the current in
-^ Linduces a voltage spike acrossl^
t V+^ v/ng^
v(t)T
iRon
Voltage spikecaused byleakageinductance^ v =^ L^ l^ l
di l^ dt
17
using a voltage-clamp snubber +–
Vg
Q^1
D^1 1:n
C Flyback transformer ig
R
-^ Snubber provides a placefor current in leakageinductance to
flow after
s
-^ v>s^
-^ Energy stored in leakageinductance (plus more) istransferred to capacitor^ C, then dissipated ins
Usually,
Decreasing
snubber power lossSee supplementary
flyback notes for an example of estimating
19
+–
L^ M
Vg
Q^1
D^1 1:n
C
Transformer modeli ig
R
Ll^1 + v–l^1
Ll^2
Diode snubber
-^ v+l^2
^ lower peak voltage,
larger snubber loss
