ML4832 Datasheet, PDF (1/15 Pages) Micro Linear Corporation – Electronic Dimming Ballast Controller

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
s
Complete power factor correction and dimming
ballast control in one IC
s
Low distortion, high efficiency continuous boost,
average current sensing PFC section
s
Programmable start scenario for rapid or instant
start lamps
s
Lamp current feedback for dimming control
s
Variable frequency dimming and starting
s
Programmable restart for lamp out condition to
reduce ballast heating
s
Over-temperature shutdown replaces external
heat sensor for safety
s
PFC overvoltage comparator eliminates output
“runaway” due to load removal
s
Large oscillator amplitude and gain modulator
improves noise immunity
s
Low start-up current <0.5mA
(* Indicates part is End Of Life as of July 1, 2000)
BLOCK DIAGRAM
RSET
7
RT/CT
8
VARIABLE FREQUENCY
OSCILLATOR
RX/CX
10
PRE-HEAT
AND INTERRUPT
TIMERS
IA OUT
2
IA+
4
ISINE
3
EA OUT
1
EA–/OVP
18
POWER
FACTOR
CONTROLLER
CONTROL
&
GATING LOGIC
UNDER-VOLTAGE
AND THERMAL
SHUTDOWN
OUTPUT
DRIVERS
INTERRUPT
9
LAMP FB
5
LFB OUT
6
OUT A
14
OUT B
13
PFC OUT
15
PGND
12
VCC
16
VREF
17
GND
11
1