AN3032

Ballast design

Doc ID 16165 Rev 2

9/26

Figure 7.

EOL circuit for first lamp

The same design procedure can be used for the EOL circuit of the second series

lamp.

●

Pin7 CTR is a multi-function pin (PFC overvoltage, feedback disconnection, reference

for EOL in case of tracking reads), connected through a resistive divider to the PFC

output bus. By establishing a maximum PFC overvoltage (PFC output overshoot, for

1.82 M

Ω and R

●

which is reached at the maximum mains voltage, should be 3 V (linearity limit) or nearly

so in wide-range mains and less in case of single mains. The PFC sense resistor

that the maximum slope of the multiplier (maxslope) is 0.75, it is possible to calculate

the maximum peak value occurring at the maximum mains voltage and the multiplier

divider

ε.

Equation 7

Supposing there is a 150 µA current flowing into the divider, the value of the lower resistor

Equation 8

97

.

1

V

V

slope

max

R

PF

V

P

2

2

V

V

slope

max

R

I

V

min

AC

max

AC

22

min

in

out

min

AC

max

AC

22

Lpk

max

MULT

=

⋅

⋅

⋅

⋅

η

⋅

⋅

=

⋅

⋅

=

()

3

max

AC

max

MULT

9

5

17

17

10

28

.

5

265

2

97

.

1

V

2

V

R

R

R

R

−

⋅

=

⋅

=

⋅

=

+

+

=

ε

Ω

=

+

⇒

Ω

=

⋅

ε

ε

−

=

+

Ω

=

μ

=

M

2

R

R

M

44

.

2

R

1

R

R

k

13

A

150

V

R

9

5

17

9

5

max

MULT

17