UCC2819A: About operation of zero power comparator

Hello Masazumi Ishii,

The error amplifier output voltage (VAOUT) varies with load. At high load and low line it is a maximum and at light load and high line it is a minimum.

The lower the value of EAOUT means the lower the duty cycle required by the pfc controller. The UCC2819A monitors the value of EAOUT.

When this voltage falls below a nominal 0.33V the gate drive output  signal (DRVOUT) is disabled. When EAOUT rises above the zero power comparator threshold then DRVOUT is re-enabled.

So instead of using a series of very narrow pulses to control the output, the UCC2819A uses a burst type of mode at low power.

That is the function of the zero power comparator.

The threshold listed on the parametric section of the data sheet for the zero power comparator

is measured at ATE before the part is acceptable.

Regards

John