UCC3817D UNITRODE, UCC3817D Datasheet - Page 12

• Manufacturer Part Number: UCC3817D
• Description: POWER FACTOR CNTRLR, 3817, SOIC16
• Manufacturer: UNITRODE

Specifications of UCC3817D

• Primary Input Voltage: 15V
• No. Of Outputs: 1
• Output Voltage: 5.5V
• Voltage Regulator Case Style: SOIC
• No. Of Pins: 16
• Operating Temperature Range: 0°C To +70°C
• Operating Temperature Max: 70°C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

12
SLUS395J - FEBRUARY 2000 - REVISED MARCH 2009
voltage loop (continued)
current loop
In this example C
frequency of the pole of the error amplifier. The location of the pole can be found by setting the gain of the loop
equation to one and solving for the crossover frequency. The frequency, expressed in terms of input power, can
be calculated by the equation:
f
Seminar SEM1000, Topic 1, [A 250-kHz, 500-W Power Factor Correction Circuit Employing Zero Voltage
Transitions].
Solving for R
or R
Due to the low output impedance of the voltage amplifier, capacitor C
loading on the voltage divider. To ensure the voltage loop crossed over at f
at a 10th of f
calculate C
The gain of the power stage is:
R
current limit point. In this example, a current limit of 4 A and a reasonable differential voltage to the current amp
of 1 V gives a R
the UCC3817. Setting the crossover frequency of the system to 1/10th of the switching frequency, or 10 kHz,
requires a power stage gain at that frequency of 0.383. In order for the system to have a gain of 1 at the crossover
frequency, the current amplifier needs to have a gain of 1/G
is then:
VI
SENSE
C
R
C
G
G
f
for this converter is 10 Hz. A derivation of this equation can be found in the Unitrode Power Supply Design
VI
f
f
f
Z
ID
EA
equals 100 kΩ.
+
+
2
+
(s) +
+
+ 1
has been chosen to give the desired differential voltage for the current sense amplifier at the desired
2
2 p
2 p
Z
G
( 2 p )
.
VI
f
ID
becomes:
p
s
. For this design a 2.2-µF capacitor was chosen for C
V
SENSE
+
f
f
OUT
1
R
VI
2
f
1
f
L
equals 150 nF. Resistor R
10
0.383
VI
BOOST
1
1
DV
G
C
value of 0.25 Ω. V
VA
f
R
VAOUT
R
+ 2.611
SENSE
f
R
V
IN
P
APPLICATION INFORMATION
V
P
OUT
IN
P
in this equation is the voltage swing of the oscillator ramp, 4 V for
f
R
www.ti.com
sets the dc gain of the error amplifier and thus determines the
IN
C
OUT
ID
at that frequency. G
C
f
Z
Z
. The following equation can be used to
was added in series with R
VI
, C
Z
EA
was selected to add a zero
, the current amplifier gain
F
to reduce