C

³

OUT

=

»

m

147 F

V

(V

)

-

OUT

OUT_MIN

2

2

2

P

OUT

h

1

f

LINE

(390V)

(240V)

-

2

2

2

300W

0.92

1

47Hz

C

=200 F

m

OUT

2

1

2

300

14

4

0 92

390

4

47

200

h

p

p

m

´

´

=

=

»

´

´

´

´

´

´

´

OUT

RIPPLE

OUT

LINE

OUT

P

W

V

V

V

f

C

.

V

Hz

F

I

=

COUT_100Hz

=

=0.591A

P

OUT

V

´ h

Ö

OUT

´

2

300W

390V

0.92

´

´ Ö

2

I

=

COUT_HF

-

(I

)

COUT_100 Hz

2

P

2

OUT

Ö

2

2 ´

´

h

V

IN_MIN

4

V

Ö

IN_MIN

2

9 V

p

OUT

2

I

=

COUT_HF

-

(0.591A)

2

300W

2

´

Ö

2

2 ´

´

0.92

85V

4

85V

Ö ´

2

9

390V

p ´

2

»

0.966A

UCC28061-Q1

SLUSB01 – MARCH 2012

www.ti.com

Output Capacitor Selection

The output capacitor (COUT) is selected based on holdup requirements as shown in Equation 19.

(19)

Two 100-

μF capacitors were used in parallel for the output capacitor:

(20)

For this size capacitor, the output voltage ripple (VRIPPLE) is approximately 11 V, as shown in Equation 21:

(21)

In addition to hold-up requirements, a capacitor must be selected so that it can withstand the low-frequency RMS

current (ICOUT_100 Hz) and the high-frequency RMS current (ICOUT_HF); see Equation 22 to Equation 24. High-

voltage electrolytic capacitors generally have both a low- and a high-frequency RMS current rating on the product

data sheets.

(22)

(23)

(24)

26

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