The PLC810PG is a combined PFC and LLC off-line controller
with integrated high voltage half-bridge drivers. Figure 1 shows
a simplifi ed schematic of a PLC810PG based power supply
where the LLC resonant inductor is integrated into the
Figure 1. Typical Application Circuit – LCD TV Power Supply.
transformer. The PFC section of the PLC810PG is a universal
input continuous current mode (CCM) design that does not
require a sinusoidal input reference, thereby reducing system
cost and external components.
The DC-DC controller drives an LLC resonant topology. This
variable frequency controller provides high effi ciency by
switching the power MOSFETs at zero voltage, eliminating most
switching losses. The LLC controller is built around a current
controlled oscillator with a control range selected to support
the traditional frequency of operation found in televisions.
To ensure zero voltage switching, the dead time of the LLC
switching in the PLC810PG is tightly toleranced and can be
adjusted with an external resistor. The highside/lowside duty
cycle is also closely matched to provide balanced output
currents reducing output diode cost.
A typical PLC810PG LLC design operates at 100 kHz (under
normal conditions). Depending on the LLC circuit design, the
switching swit frequency can vary from half to three times the
nominal operating frequency as a result of line and load changes.