FSBH0270NY_F116 Fairchild Semiconductor, FSBH0270NY_F116 Datasheet - Page 13

• Manufacturer Part Number: FSBH0270NY_F116
• Description: The highly integrated FSBH-series consists of an integrated current-mode Pulse Width Modulator (PWM) and an avalanche-rugged 700V SenseFET
• Manufacturer: Fairchild Semiconductor

© 2010 Fairchild Semiconductor Corporation
FSBH0F70A_F116, FSBH0170/0270/0370_F116 • Rev. 1.0.1
Brown-In Function of FSBH0F70A
The VIN pin functions are disabled in FSBH0F70A, but
FSBH0F70A has brown-in protection in the VDD pin.
There is a discharge current internal from V
during startup. The HV source current must be larger
than I
brown-in level can be determined by R
the equation:
Green-Mode Operation
The FSBH-series uses feedback voltage (V
indicator of the output load and modulates the PWM
frequency, as shown in Figure 30, such that the
switching frequency decreases as load decreases. In
heavy-load conditions, the switching frequency is
100kHz. Once V
PWM frequency starts to linearly decrease from 100kHz
to 18kHz to reduce switching losses. As V
below V
18kHz and the FSBH-series enters “deep” green mode to
reduce the standby power consumption.
As V
series enters burst-mode operation. When V
below V
output voltage starts to drop, which causes the feedback
voltage to rise. Once V
resumes. Burst mode alternately enables and disables
switching, thereby reducing switching loss to improve
power saving, as shown in Figure 31.
R
HV
FB
DD-ST

Figure 31.
FB-G
FB-ZDC
decreases below V
2
Figure 30.
I
to charge the capacitor of V
V
DD ST
AC
(2.0V), the switching frequency is fixed at

, FSBH-series stops switching and the

12
FB
decreases below V
Burst-Mode Operation
FB
PWM Frequency
rises above V
FB-ZDC
(1.6V), the FSBH-
DD
FB-ZDC
HV
FB-N
. Therefore, the
FB
according to
DD
(2.5V), the
, switching
decreases
FB
to ground
FB
) as an
drops
(4)
13
H/L Line Over-Power Compensation
To limit the output power of the converter constantly,
high/low line over-power compensation is included.
Sensing the converter input voltage through the VIN pin,
the high/low line compensation function generates a
relative peak-current-limit threshold voltage for constant
power control, as shown in Figure 32.
Protections
The FSBH-series provides full protection functions to
prevent the power supply and the load from being
damaged. The protection features include:
Latch/Auto-Recovery Function
Besides the brownout protection and high/low line over-
power
additional protections via the VIN pin, such as pull-HIGH
latch and pull-LOW auto-recovery that depends on the
application. As shown in Figure 33, when V
higher than 4.7V, FSBH-series is latched until the V
discharged. FSBH-series is auto-recovery when the V
level is lower than 0.3V.
Open-Loop / Overload Protection (OLP)
When the upper branch of the voltage divider for the
shunt regulator (KA431 shown) is broken, as shown in
Figure 34, or over current or output short occurs, there
is no current flowing through the opto-coupler transistor,
which pulls the feedback voltage up to 6V.
When feedback voltage is above 4.6V for longer than
56ms, OLP is triggered. This protection is also triggered
when the SMPS output drops below the nominal value
longer than 56ms due to the overload condition.
Figure 32.
compensation,
Figure 33.
Constant Power Control
VIN Pin Function
the
FSBH0X70_F116
www.fairchildsemi.com
IN
level is
DD
has
is
IN