E-L6563TR STMicroelectronics, E-L6563TR Datasheet - Page 19

• Manufacturer Part Number: E-L6563TR
• Description: IC CTRLR PFC TRANSITION 14-SOIC
• Manufacturer: STMicroelectronics

Specifications of E-L6563TR

• Mode: Discontinuous (Transition)
• Current - Startup: 50µA
• Voltage - Supply: 10.3 V ~ 22 V
• Operating Temperature: -25°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 14-SOIC (3.9mm Width), 14-SOL
• Maximum Operating Temperature: + 150 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 25 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Frequency - Switching: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

L6563 - L6563A
Figure 35. Voltage feedforward: squarer-divider (1/V
In this way a change of the line voltage will cause an inversely proportional change of the
half sine amplitude at the output of the multiplier (if the line voltage doubles the amplitude of
the multiplier output will be halved and vice versa) so that the current reference is adapted to
the new operating conditions with (ideally) no need for invoking the slow dynamics of the
error amplifier. Additionally, the loop gain will be constant throughout the input voltage
range, which improves significantly dynamic behavior at low line and simplifies loop design.
Actually, deriving a voltage proportional to the RMS line voltage implies a form of integration,
which has its own time constant. If it is too small the voltage generated will be affected by a
considerable amount of ripple at twice the mains frequency that will cause distortion of the
current reference (resulting in high THD and poor PF); if it is too large there will be a
considerable delay in setting the right amount of feedforward, resulting in excessive
overshoot and undershoot of the pre-regulator's output voltage in response to large line
voltage changes. Clearly a trade-off is required.
The device realizes Voltage Feedforward with a technique that makes use of just two
external parts and that limits the feedforward time constant trade-off issue to only one
direction. A capacitor C
ground, complete an internal peak-holding circuit that provides a DC voltage equal to the
peak of the rectified sine wave applied on pin MULT (pin 3). R
discharge C
sudden line voltage rise, C
internal diode and no appreciable overshoot will be visible at the pre-regulator's output; in
case of line voltage drop C
be in the hundred ms to achieve an acceptably low steady-state ripple and have low current
distortion; consequently the output voltage can experience a considerable undershoot, like
in systems with no feedforward compensation.
reference
L6563A
current
(Vcsx)
L6563
MULTIPLIER
FF
characteristic
E/A output
(V
COMP
1/V
when the line voltage decreases (see
C
FF
VFF
2
)
5
"ideal" diode
FF
R
FF
and a resistor R
FF
FF
+
-
9.5V
will be rapidly charged through the low impedance of the
will be discharged with the time constant R
3
MULT
Rectified mains
R5
R6
FF
, both connected from the VFF (pin 5) pin to
Vcsx
1.5
0.5
2
1
0
0
Figure
0.5
2
) block diagram and transfer
35). In this way, in case of
1
FF
provides a means to
V
FF
Application information
=V
MULT
2
V
FF
COMP
Actual
Ideal
·C
=4V
FF
, which can
3
19/39
4