BL8305A

BL8305A

BL8305A

BALLAST CONTROL IC

BALLAST CONTROL IC

BALLAST CONTROL IC

http://www.belling.com.cn

- 5 -

8/28/2006

Total 8 Pages

2

1

2

7

*

249

.

0

10

203

.

0

p

p

p

p

preheat

R

R

R

C

T

+

−

×

×

=

sec。Preheat frequency is set by the

voltage(VRpre)

at

pin3,

the

preheat

frequency

is:

run

Rpre

pre

f

V

f

×

=

6

.

1

，

35

.

6

2

1

2

Pr

×

+

=

pre

pre

pre

e

R

R

R

R

V

. The run mode oscillating frequency is determined by the

timing resistor RT and timing capacitor Ct,

t

t

run

C

R

f

×

=

374

.

0

。

Drive BHF or MHF

Drive BHF or MHF

Drive BHF or MHF

Drive BHF or MHF

When driving BHF, a transformer with two secondary magnifies the output current

of BL8305A and the half-bridge is drive by the magnified current. The output voltage

of half-bridge is divided by the resistor RHV and an internal resistor about 40Kohm

in the PIN HV and the BL8305A senses this waveform, and automatically adjusts the

BCI. The BCI Auto-Adj is enabled at about 1 sec after the ignition. As showing in

the figure, if BCI is appropriate, the output of BL8305A will be remain as the black

line; if BCI is low, the output of BL8305A will be increase as the dashed line;

if BCI is over driving, the output of BL8305A will be decrease as the dashdotted

line.