UCC28600_15 Datasheet, PDF (21/44 Pages) Texas Instruments – UCC28600 8-Pin Quasi-Resonant Flyback Green-Mode Controller

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8 Application and Implementation
UCC28600
SLUS646K – NOVEMBER 2005 – REVISED AUGUST 2015
NOTE
Information in the following Applications section is not part of the TI component
specification, and TI does not warrant its accuracy or completeness. TI’s customers
are responsible for determining suitability of components for their purposes.
Customers should validate and test their design implementation to confirm system
functionality.
8.1 Application Information
The UCC28600 device is a flyback controller that operates in a mode that is determined by the FB voltage. Line
and load conditions set the FB voltage and the controller will operate in Green Mode (GM) under light-load
conditions, Frequency Foldback Mode (FFM) when operating at loads approximately between 10% and 30% full
rated load, and Quasi-Resonant (QR) or Discontinuous Mode (DCM) at higher loads. Valley switching under all
modes, except green mode, reduces switching losses and improves efficiency. Valley skipping also helps reduce
EMI. A dedicated STATUS pin is used in higher power applications that use a power factor corrected (PFC) front
end. Under light-load conditions, the STATUS signal can be used to disconnect the bias power to the PFC
controller, reducing light-load power consumption.
8.2 Typical Application
A typical application for the UCC28600 is an off-line flyback controller from 65 W to 120 W, using a PFC output
voltage as its input, as shown in Figure 13. The PFC stage is assumed to operate from a universal AC input and
can be controlled by a device such as the UCC28051. The auxiliary winding provides the bias to the controllers
and provides over voltage protection and valley switching information, as well as bias to the UCC28600 and
UCC28051. The UCC28600 will disable the PFC controller during green mode operation, improving light-load
system efficiency. The series resistor connected between the current sense pin and the current sense resistor
programs the power limit of the converter. Low valley voltage switching and multi-mode operation will keep the
efficiency curve high over the entire operation range. Typical applications include bias supplies for LCD monitors,
LCD and PDP televisions, set top boxes, AC-DC adaptors, and energy efficient power supplies up to 200 W.
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