An apparatus for reducing the power consumption of a PFC-PWM power converter
is
described. The apparatus includes a control terminal used to detect a line-input
voltage and to control a PFC signal and a PWM signal. The apparatus further includes
a PFC power-manager and a PWM power-manager. The PFC power-manager of the PFC controller
determines a PFC-reference voltage for an error amplifier of the PFC controller.
The PFC-reference voltage is generated in response to the voltage at the control
terminal. The PFC power-manager will disable the PFC signal whenever the voltage
at the control terminal drops below a low-voltage threshold voltage. The PWM power-manager
will disable the PWM signal whenever the voltage at the control terminal drops
below a programmable threshold voltage. Furthermore, the PWM power-manager will
pull the voltage at the control terminal low to disable the PFC circuitry during
light-load and zero-load conditions.