UCC3817D UNITRODE, UCC3817D Datasheet - Page 13

• 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

current loop (continued)
R
is R
crossover frequency and a pole at half the switching frequency completes the current loop compensation.
The UCC3817 current amplifier has the input from the multiplier applied to the inverting input. This change in
architecture from previous Texas Instruments PFC controllers improves noise immunity in the current amplifier.
It also adds a phase inversion into the control loop. The UCC3817 takes advantage of this phase inversion to
implement leading-edge duty cycle modulation. Synchronizing a boost PFC controller to a downstream dc-to-dc
controller reduces the ripple current seen by the bulk capacitor between stages, reducing capacitor size and
cost and reducing EMI. This is explained in greater detail in a following section. The UCC3817 current amplifier
configuration is shown in Figure 4.
I
is the R
C
C
f
/R
Z
P
I
+
+
, so multiplying R
2
2
MOUT
p
p
resistor, previously calculated to be 3.9 kΩ. (refer to Figure 3). The gain of the current amplifier
1
1
R
R
MULT
f
f
Figure 4. UCC3817 Current Amplifier Configuration
I
f
f s
2
C
by G
−
EA
Figure 3. Current Loop Compensation
R I
gives the value of R
R SENSE
APPLICATION INFORMATION
L BOOST
−
+
R f
+
Z f
−
+
CA
www.ti.com
C
P
f
, in this case approximately 12 kΩ. Setting a zero at the
C
Z
COMPARATOR
Q BOOST
PWM
−
+
SLUS395J - FEBRUARY 2000 - REVISED MARCH 2009
CAOUT
V OUT
13