FSFR1700HS Fairchild Semiconductor, FSFR1700HS Datasheet - Page 10

• Manufacturer Part Number: FSFR1700HS
• Description: The FSFR-HS is a highly integrated power switch designed for high-efficiency half-bridge resonant converters
• Manufacturer: Fairchild Semiconductor

© 2011 Fairchild Semiconductor Corporation
FSFR1800 / FSFR1700-HS • Rev.1.0.0
The initial maximum frequency can be set up to 600kHz,
which is given by:
The soft-start time, t
4. Self Auto-Restart: The FSFR-HS series can restart
automatically even though any built-in protections are
triggered in case external supply voltage is applied. As
shown in Figure 22 and Figure 23; once a protection is
triggered, the power MOSFET immediately stops. The
counter starts to operate and 1008-clocks are counted,
then the V-I converter is disabled. C
naturally discharged with the series impedance of R
and R
all protections are reset and the V-I converter resumes.
The FSFR-HS starts switching again with soft-start.
The counter operating time for 1008-clocks after
protection activation is set by the current out of the RT
pin until V
FSFR-HS can be estimated, without considering the
counter operation time, as:
t
t
f
SS
STOP
ss


3

min
792
Figure 22. Internal Block for Auto-Restart

3
Figure 23. Self Auto-Restart Operation
R
C
until V
SS
p
RT
SS



C
drops to V

R
R
SS
RT
min
SS
[
drops to V

1
||
] s
R
SS
R
min
SS
, can be calculated by:

RT,RESET

[
. 0
] s
54
RT,RESET

. Finally, the stop time of
[
Hz
, typically 0.1V. Then,
]
SS
starts to be
(3)
(4)
(5)
SS
10
5. Protection Circuits: The FSFR-HS series has several
self-protective functions; such as Over-Current Protection
(OCP), Abnormal Over-Current Protection (AOCP), Over-
Voltage Protection (OVP), Thermal Shutdown (TSD), and
Line Under-Voltage Lockout (LUVLO or Brownout).
These protections are Auto-Restart Mode protections, as
shown in Figure 24.
Once a fault condition is detected, switching is instantly
terminated and the MOSFETs remain off. When LV
to the LV
V
resumes normal operation when LV
voltage of 12.5V.
6. Line Under-Voltage Lockout (UVLO): FSFR-HS
includes
programmable hysteresis voltage. This function can start
or restart the IC when V
the DC-link by the sensing resistors, R1 and R2, is higher
than V
vice versa. A hysteresis voltage between the start and
stop voltage of the IC is programmable by I
operation, the comparator’s output is HIGH and I
deactivated so that a voltage on LS pin, V
obtained as a divided voltage by R1 and R2. On the
contrary, I
is LOW. V
current through R1 and I
RT,RESET
5.1 Over-Current Protection (OCP): When the
sensing pin voltage drops below -0.58V and its duration
becomes more than OCP blanking time of 1.5µs, OCP
is triggered and the MOSFETs remain off.
5.2 Abnormal Over-Current Protection (AOCP):
If the secondary rectifier diodes are shorted, large
current with extremely high di/dt can flow through the
MOSFET before OCP is triggered. AOCP is triggered
without shutdown delay if the sensing pin voltage drops
below -0.9V.
5.3 Over-Voltage Protection (OVP): When the LV
reaches 23V, OVP is triggered. This protection is used
when auxiliary winding of the transformer supplies V
to the FPS™.
5.4 Thermal Shutdown (TSD): The MOSFETs and
the control IC in one package make it easier for the
control IC to detect the abnormal over-temperature of
the
approximately 130C, thermal shutdown triggers.
LINE
MOSFETs.
of 0.1V, the protection is reset. The FSFR-HS
CC
LINE
LS
precise
of 2.5V as the DC-link voltage increases and
stop voltage of 10V and V
is generated by the difference between the
Figure 24. Protection Blocks
is activated when the comparator’s output
line
If
LINE
LS
UVLO
the
for the scale-down voltage of
.
temperature
(or
CC
reaches the start
brownout)
RT
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LINE
is lower than
LS,
. In normal
exceeds
can be
CC
LINE
with
falls
CC
CC
is