Product Specification
Highly-Integrated Green-Mode PWM Controller
SG6846
the switching frequency under light-load conditions.
Under zero-load conditions, the power supply enters
burst-mode. This completely shuts off PWM output. The
output restarts just before the supply voltage drops below
the UVLO lower limit. This green-mode function enables
power supplies to easily meet international power
conservation requirements.
The SG6846 is especially designed for SMPS with
surge-current output. It is incorporated with a two-level
OCP function. Besides the cycle-by-cycle current limiting,
if the switching current is higher than 2/3 of the
peak-current threshold for a delay time, over-current
protection will be activated such that the SG6846 will be
totally shutdown. Other protection functions include: AC
input brownout protection with hysteresis, and VDD
over-voltage protection. For over-temperature protection,
an external NTC thermistor can be applied to sense the
ambient temperature. When OCP, VDD OVP, or OTP are
activated, an internal latch circuit is used to latch-off the
controller. The latch will reset when the VDD supply is
removed.
Other features of this controller include: Built-in
synchronized slope compensation, proprietary internal
compensation for constant output power limit over
universal AC input range. Also, the gate output is clamped
at 18V to protect the external MOSFET from over-voltage
damage.
The SG6846 series controllers are available in both
8-pin DIP and SO packages.
FEATURES
Two-level OCP with 96mS delay time
Peak-current-mode operation with cycle-by-cycle
current limiting
PWM frequency continuously decreasing w/ burst
mode at light loads
Low start-up current (8uA)
Low operating current (3.7mA)
VDD over-voltage protection (OVP)
AC input brownout protection with hysteresis
Programmable over-temperature protection (OTP)
Constant power limit over universal AC input range
Internal latch circuit for OTP, OVP, OCP
Very few external components
APPLICATIONS
General-purpose switch mode power supplies and
flyback power converters, including:
Power adapters
Open-frame SMPS
Specifically fit for SMPS with surge-current output,
such as for printers, scanners, motor drivers, etc.
DESCRIPTION
The highly integrated SG6846 series of PWM
controllers provides several features to enhance the
performance of flyback converters. To minimize standby
power consumption, a proprietary green-mode function
provides off-time modulation to continuously decrease
TYPICAL APPLICATION
© System General Corp.
Version 1.0(IAO33.0008.B0)
-1-
www.sg.com.tw
Sep. 30, 2004
ETC [ ETC ]
