ML4836

9

F

tt

OSC

CHG

DIS

=

+

1

(3)

and

tR C In

VI

R

V

VII

R

V

CHG

T

T

REF

CHG

T

TL

REF

CHG

T

TH

=

+´

-

+´

-









(4)

where:

F

RC

MIN

TT

≅

×

1

054

.

(5)

The oscillator's start frequency can be expressed by:

F

RR

C

START

TT

T

=

××

1

054

2

.

27

(5a)

frequency occurs. The charging current varies according to

two control inputs to the oscillator:

1. The output of the preheat timer

2. The voltage at LFB OUT (lamp feedback amplifier

output)

In preheat condition, charging current is fixed at

I

R

CHG PREHEAT

SET

()

.

=

25

(6)

In running mode, charging current decreases as the

The charging current behavior can be expressed as:

I

V

R

LEAO

k

CHG

SET

=

-

±

5

8

25%

(7)

which is attained when voltage at LFB OUT is at 0V:

I

R

CHG

SET

()

0

5

=

(8)

Highest lamp power, and lowest output frequency are

attained when voltage at LFB OUT is at its maximum

the Rectified AC Line and Bootstrapped from an Auxiliary Winding.

VCCZ

V(ON)

V(OFF)

5.5mA

0.34mA

t

t