The highly integrated SG5841/J 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 the switching frequency at
light-load conditions. This green-mode function enables the power supply to meet
international power conservation requirements. To further reduce power
consumption, SG5841/J is manufactured using the BiCMOS process. This allows a
low start-up current, around 14ľA, and an operating current of only 4mA. As a
result, a large start-up resistance can be used.
The SG5841/J built-in synchronized slope compensation achieves stable
peak-current-mode control. The proprietary internal sawtooth power-limiter
ensures constant output power limit over a wide range of AC input voltages, from
90VAC to 264VAC.
SG5841/J provides many protection functions. In addition to cycle-by-cycle
current limiting, the internal open-loop protection circuit ensures safety
should an open-loop or output-short-circuit failure occur. PWM output is
disabled until VDD drops below the UVLO lower limit, then the
controller starts again. An external NTC thermistor can be applied for
over-temperature protection.
SG5841/J is available in an 8-pin DIP or SOP package.
|
