FSEZ1016A Fairchild Semiconductor, FSEZ1016A Datasheet - Page 11

• Manufacturer Part Number: FSEZ1016A
• Description: This highly integrated PWM controller provides several features to enhance the performance of low-power flyback converters
• Manufacturer: Fairchild Semiconductor

© 2009 Fairchild Semiconductor Corporation
FSEZ1016A • Rev. 1.0.2
Temperature Compensation
Built-in temperature compensation provides constant
voltage regulation over a wide range of temperature
variation.
compensates the forward-voltage drop variation of the
secondary-side rectifier diode.
Green-Mode Operation
The FSEZ1016A uses voltage regulation error amplifier
output (V
modulates the PWM frequency, as shown in Figure 26,
such that the switching frequency decreases as load
decreases. In heavy-load conditions, the switching
frequency is fixed at 43KHz. Once V
below 2.8V, the PWM frequency starts to linearly
decrease from 43KHz to 550Hz to reduce the switching
losses. As V
frequency is fixed at 550Hz and FSEZ1016A enters
“deep green” mode, where the operating current drops
to 1mA, reducing the standby power consumption.
Leading-Edge Blanking (LEB)
At the instant the MOSFET is turned on, there is a high-
current spike through the MOSFET, caused by primary-
side capacitance and secondary-side rectifier reverse
recovery. Excessive voltage across the R
lead to premature turn-off of the MOSFET. FSEZ1016A
employs an internal leading-edge blanking (LEB) circuit
to inhibit the PWM comparator for a short time after the
MOSFET is turned on. External RC filtering is not required.
Frequency Hopping
EMI reduction is accomplished by frequency hopping,
which spreads the energy over a wider frequency range
than the bandwidth measured by the EMI test
equipment. FSEZ1016A has an internal frequency-
hopping circuit that changes the switching frequency
between 40.4kHz and 45.6kHz with a period of 3ms, as
shown in Figure 27.
43kHz
550H z
Figure 26. Switching Frequency in Green Mode
Swi tc hing Frequen cy
G r een
COMV
Mode
Dee p
This
COMV
) as an indicator of the output load and
0 . 8 V
decreases below 0.8V, the switching
internal
Green Mod e
compensation
2 . 8V
COMV
Normal Mod e
CS
resistor can
decreases
current
V
COMV
11
Startup
Figure 28 shows the typical startup circuit and
transformer
application. Before FSEZ1016A begins switching, it
consumes only startup current (typically 10μA) and the
current supplied through the startup resistor charges the
V
of 16V (V
current consumed increases to 3.5mA. Then, the power
required
transformer auxiliary winding. The large hysteresis of
V
small capacitor for V
DD
DD
43
45.6kHz
40
.
capacitor (C
.
provides more hold-up time, which allows using a
0kHz
4kHz
AC line
1
2
3
4
FSEZ1016A
CS
COMI
COMV
DD-ON
GND
Gate Drive Signal
f
for
s
Figure 27. Frequency Hopping
auxiliary
Figure 28. Startup Circuit
), FSEZ1016A begins switching, and the
t
t
t
C
DRAIN
FSEZ1016A
DD
s
s
s
DL
VDD
VS
). When V
DD
8
6
5
V
.
+
-
DL
winding
DD
3ms
is
C
R
reaches turn-on voltage
DD
START
D
DD
for
supplied
a
FSEZ1016A
www.fairchildsemi.com
from
N
R
R
Np
A
S1
S2
t
the