CS1600

DS904A5

11

5. FLUORESCENT BALLAST APPLICATION EXAMPLE

The following section gives an example for a front-end PFC stage design for an electronic ballast application. The equations that

follow may be used as guidelines for any other requirements using the CS1600.

5.1

Component Selection Guidelines

The following design example is for a wide-input-voltage

fluorescent ballast application using 2 T5 lamps in series for a

total nominal power of 108W.The target specifications for the

PFC portion of the design, assuming a 94% efficient second

stage, are as follows:

5.1.1

sense resistors, whose values are estimated based on the

equations below:

where

voltage

voltage

1% or lower tolerance resistors are recommended to

maximize the tightly toleranced system behavior provided by

the unique digital controller in the CS1600. Resistors may be

separated into two or more series elements if voltage

breakdown and/or regulatory compliance is of concern.

5.1.2

PFC Input Filter Capacitor

For a typical 115 W PFC output stage required to power up a

108 W fluorescent ballast, an input filter capacitance of

0.33

μF is recommended. Capacitor tolerances and the value

of the EMI filter capacitor need to be considered when

selecting the value of the capacitor to be used in this

application.

D6

C1

D5

C2

BR1

BR1

BR1

BR1

AC

Mains

+12V

L1

Q1

R3

CS1600

IAC

NC

FB

STBY

VDD

GND

NC

GD

2

3

1

7

8

6

4

5

R1a

R1b

R2b

R2a

C3a

C3b

R2c

R1c

Figure 17. CS1600 Basic Application Circuit

108 VAC

305 VAC

460 V

115 W

η

95%

R

FB

V

link

V

dd

–

I

ref

----------------------------

=

R

FB

460

12

–

130

10

6

–

×

----------------------------

=

R

FB

3.45M

Ω

=

[Eq.4]

R

AC

R

FB

=

R

AC

3.45M

Ω

=

[Eq.5]