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The PLC810PG is a combined PFC and LLC off-line controllerwith integrated high voltage half-bridge drivers. Figure 1 showsa simplifi ed schemaTIc of a PLC810PG based power supplywhere the LLC resonant inductor is integrated into theFigure 1. Typical ApplicaTIon Circuit – LCD TV Power Supply.transformer. The PFC secTIon of the PLC810PG is a universalinput conTInuous current mode (CCM) design that does notrequire a sinusoidal input reference, thereby reducing systemcost and external components.The DC-DC controller drives an LLC resonant topology. Thisvariable frequency controller provides high effi ciency byswitching the power MOSFETs at zero voltage, eliminating mostswitching losses. The LLC controller is built around a currentcontrolled oscillator with a control range selected to supportthe traditional frequency of operation found in televisions.To ensure zero voltage switching, the dead time of the LLCswitching in the PLC810PG is tightly toleranced and can beadjusted with an external resistor. The highside/lowside dutycycle is also closely matched to provide balanced outputcurrents reducing output diode cost.A typical PLC810PG LLC design operates at 100 kHz (undernormal conditions). Depending on the LLC circuit design, theswitching swit frequency can vary from half to three times thenominal operating frequency as a result of line and load changes.
