The highly integrated SG6905 is specially designed for power supplies
consisting of boost PFC and flyback PWM. It requires very few external
components to achieve green-mode operation and versatile protections. It is
available in 20-pin SOP package.
The proprietary interleave-switching feature synchronizes the PFC and PWM
stages and reduces switching noise. At light loads, the switching frequency is
continuously decreased to reduce power consumption.
For PFC stage, the proprietary multi-vector control scheme provides a fast
transient response in a low-bandwidth PFC loop, in which the overshoot and
undershoot of the PFC voltage are clamped. If the feedback loop is broken, the
SG6905 shuts off PFC to prevent extra-high voltage on output.
For the flyback PWM, the synchronized slope compensation ensures the
stability of the current loop under continuous-conduction-mode operation.
Built-in line-voltage compensation maintains constant output-power limit. Hiccup
operation during output overloading is also guaranteed.
During startup, the RDY (ready) is pulled low until the PFC output voltage
reaches the setting level. This signal can be used to control the second power
stage for proper power-on sequence.
In addition, SG6905 provides complete protection functions, such as brownout
protection and RI pin open/short.
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