VSENSE

EAOUT

VINS

ISENSE

TZE

GND

GDRV

VDD

VAC Input

(

)

OUT

IN min

1.7 V

R21

P

2

2 1.2

V

@

´ ´

´

h ´

(2)

(

)

(

)

(

)

(

)

(

)

(

)

2

OUT min

IN min

IN min

S

OUT

OUT min

V

2

V

V

L2

2 f

V

P

-

´

´ h ´

@

´

´

´

(3)

UCC28810

UCC28811

Figure 25. Boost Follower Circuit

The voltage error amplifier compensation network is R10, C4 and C7 connected from EAOUT to GND. The goal

is to provide a loop crossover frequency at 1/10 input line frequency (10 Hz) with 45° phase margin.

The current sense resistor (R21) is determined by the following equation which is based on peak inductor current

at low line, 1.7 V ISENSE threshold, and 20% margin.

The boost inductor value can be determined based on the desired minimum operating frequency which occurs at

the peak of low line input voltage.

.

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