Tài liệu Circuits & Electronics P24 pptx

6.002 Fall 2000 Lecture
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6.002
CIRCUITS
AND
ELECTRONICS
Power Conversion Circuits
and Diodes
6.002 Fall 2000 Lecture
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Power Conversion Circuits (PCC)
Power efficiency of converter important,
so use lots of devices:
MOSFET switches, clock circuits,
inductors, capacitors, op amps, diodes
Reading: Chapter 16 and 4.4 of A & L.
PCC
110V
60Hz
+
–
5V DC
solar cells,
battery
PCC
+
–
5V DC
3V

DC
DC-to-DC UP converter
R
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First, let’s look at the diode
Can use this exponential model with
analysis methods learned earlier

analytical

graphical

incremental
(Our fake expodweeb was modeled after this device!)
D
v
D
i
D
v
D
i
S
I−
mV
V
D
v

+
–
D
i
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
−= 1eIi
T
D
V
v
SD
A10I
12
S
−
=
V025.0V
T
=
q
Tk
V
T

=
Boltzmann’s constant
temperature in Kelvins
charge of an electron
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Another analysis method:
piecewise–linear analysis
P–L diode models:
D
v
D
i
0
Ideal diode model
Æ
i
D
= 0
“open”
or
off
v
D
< 0
Æ
v
D
= 0

“short”
or
on
i
D
≥ 0
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D
v
D
i
V6.0
0v
D
=
0i
D
=
“Practical” diode model
ideal with offset
V6.0
+
–
Another analysis method:
piecewise–linear analysis
Open segment
Short segment
6.002 Fall 2000 Lecture

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Another analysis method:
piecewise–linear analysis

Replace nonlinear characteristic with
linear segments.

Perform linear analysis within each
segment.
Piecewise–linear analysis method
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(We will build up towards an AC-to-DC converter)
R
O
v
+
–
+
–
I
v
V6.0
+
–
Example
Consider
v

I
is a sine wave
6.002 Fall 2000 Lecture
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0v
O
=
0i
D
=
“Open segment”:
R
+
–
I
v
+
–
+
–
V6.0
6.0v
I
<
R
O
v
+
–

+
–
I
v
()
R/6.0vi
ID
−=
6.0vv
IO
−=
“Short segment”:
R
+
–
+
–
+
–
V6.0
6.0v
I
≥
I
v
Example
V6.0
+
–
Equivalent

circuit