UCC3818D UNITRODE, UCC3818D Datasheet - Page 11

• Manufacturer Part Number: UCC3818D
• Description: POWER FACTOR CNTRLR, 3818, SOIC16
• Manufacturer: UNITRODE

Specifications of UCC3818D

• 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

multiplier (continued)
voltage loop
I
In this example V
roughly 3.91 kΩ.
The second major source of harmonic distortion is the ripple on the output capacitor at the second harmonic
of the line frequency. This ripple is fed back through the error amplifier and appears as a 3rd harmonic ripple
at the input to the multiplier. The voltage loop must be compensated not just for stability but also to attenuate
the contribution of this ripple to the total harmonic distortion of the system. (refer to Figure 2).
The gain of the voltage amplifier, G
the output capacitor. The peak value of the second harmonic voltage is given by the equation:
In this example V
the voltage loop to the total harmonic distortion budget we set the gain equal to:
where ∆V
needed to realize this filter is comprised of an input resistor, R
value of R
back to the voltage amplifier for output voltage regulation. In this case the value was chosen to be 1 MΩ. This
high value was chosen to reduce power dissipation in the resistor. In practice, the resistor value would be
realized by the use of two 500-kΩ resistors in series because of the voltage rating constraints of most standard
1/4-W resistors. The value of C
MOUT(max)
V
G
R
OPK
VA
MOUT
+
VAOUT
+
IN
+
DV
for this design is approximately 315 µA. The R
is already determined because of its function as one half of a resistor divider from V
2 p
I
VAOUT
MOUT(max)
2
V
OPK
RSENSE
is the effective output voltage range of the error amplifier (5 V for the UCC3817). The network
RSENSE
f
V
R
is equal to 3.91 V. Assuming an allowable contribution of 0.75% (1.5% peak to peak) from
OPK
( 0.015 )
P
C
was selected to give a dynamic operating range of 1.25 V, which gives an R
IN
OUT
Figure 2. Voltage Amplifier Configuration
f
is determined by the equation:
APPLICATION INFORMATION
VA
V
OUT
, can be determined by first calculating the amount of ripple present on
V OUT
R IN
R D
www.ti.com
V REF
R f
−
+
C f
C Z
MOUT
IN
, and feedback components C
resistor can then be determined by:
SLUS395J - FEBRUARY 2000 - REVISED MARCH 2009
f
, C
Z
, and R
OUT
MOUT
feeding
f
. The
of
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