PWM Current-Mode Controller for Low-Power Universal Off-Line Supplies
Controller for Low-Power
Universal Off-Line Supplies
Housed in SOIC−8 or PDIP−8 package, the NCP1200 represents a
major leap toward ultra−compact Switchmode Power Supplies. Due to
a novel concept, the circuit allows the implementation of a complete
offline battery charger or a standby SMPS with few external
components. Furthermore, an integrated output short−circuit
protection lets the designer build an extremely low−cost AC−DC wall
adapter associated with a simplified feedback scheme.
With an internal structure operating at a fixed 40 kHz, 60 kHz or
100 kHz, the controller drives low gate−charge switching devices like
an IGBT or a MOSFET thus requiring a very small operating power.
Due to current−mode control, the NCP1200 drastically simplifies the
design of reliable and cheap offline converters with extremely low
acoustic generation and inherent pulse−by−pulse control.
When the current setpoint falls below a given value, e.g. the output
power demand diminishes, the IC automatically enters the skip cycle
mode and provides excellent efficiency at light loads. Because this
occurs at low peak current, no acoustic noise takes place.
Finally, the IC is self−supplied from the DC rail, eliminating the
need of an auxiliary winding. This feature ensures operation in …