July 2000
PRELIMINARY
ML4832*
Electronic Dimming Ballast Controller
GENERAL DESCRIPTION
The ML4832 is a complete solution for a dimmable/non-
dimmable, high power factor, high efficiency electronic
ballast. The BiCMOS ML4832 contains controllers for
“boost” type power factor correction as well as for a
dimming ballast.
The power factor circuit uses the average current sensing
method with a gain modulator and overvoltage protection.
This system produces a power factor of better than 0.99
with low input current THD at > 95% efficiency. Special
care has been taken in the design of the ML4832 to
increase system noise immunity by using a high amplitude
oscillator, and a current-fed multiplier. An overvoltage
protection comparator inhibits the PFC section in the
event of a lamp out or lamp failure condition.
The ballast section provides for programmable starting
scenarios with programmable preheat and lamp out-of-
socket interrupt times. The IC controls lamp output through
frequency modulation using lamp current feedback.
FEATURES
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Complete power factor correction and dimming
ballast control in one IC
Low distortion, high efficiency continuous boost,
average current sensing PFC section
Programmable start scenario for rapid or instant
start lamps
Lamp current feedback for dimming control
Variable frequency dimming and starting
Programmable restart for lamp out condition to
reduce ballast heating
Over-temperature shutdown replaces external
heat sensor for safety
PFC overvoltage comparator eliminates output
“runaway” due to load removal
Large oscillator amplitude and gain modulator
improves noise immunity
Low start-up current <0.5mA
(* Indicates part is End Of Life as of July 1, 2000)
BLOCK DIAGRAM
INTERRUPT
7
8
R
SET
R
T
/C
T
VARIABLE FREQUENCY
OSCILLATOR
OUTPUT
DRIVERS
R
X
/C
X
PRE-HEAT
AND INTERRUPT
TIMERS
OUT A
CONTROL
&
GATING LOGIC
OUT B
14
LAMP FB
LFB OUT
9
5
6
10
13
PFC OUT
2
4
3
1
18
IA OUT
IA+
I
SINE
EA OUT
EA–/OVP
POWER
FACTOR
CONTROLLER
UNDER-VOLTAGE
AND THERMAL
SHUTDOWN
PGND
V
CC
V
REF
GND
15
12
16
17
11
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
