ML4833 Datasheet, PDF (1/13 Pages) Micro Linear Corporation – Electronic Dimming Ballast Controller

July 2000
PRELIMINARY
ML4833*
Electronic Dimming Ballast Controller
GENERAL DESCRIPTION
The ML4833 is a complete solution for a dimmable or a
non-dimmable, high power factor, high efficiency
electronic ballast. The BiCMOS ML4833 contains
controllers for “boost” type power factor correction as
well as for a dimming ballast. The ML4833 was designed
to minimize the number of external components required
to build an electronic ballast.
The PFC circuit uses a new, simple PFC topology which
requires only one loop for compensation. This system
produces a power factor of better than 0.99 with low
input current THD. An overvoltage protection comparator
inhibits the PFC section in the event of a lamp out or lamp
failure condition.
The ballast controller section provides for programmable
starting sequence with individually adjustable preheat and
lamp out-of-socket interrupt times. The IC controls lamp
output power through feedback. The ML4833 provides a
power down input which reduces power to the lamp, for
GFI, end of life, etc.
BLOCK DIAGRAM
FEATURES
s Complete power factor correction and dimming
ballast control in one IC
s Low distortion, high efficiency continuous boost,
peak 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 Internal over-temperature shutdown replaces
external heat sensor
s PFC overvoltage comparator eliminates output
“runaway” due to load removal
s Low start-up current <0.5mA
s Power reduction pin for end of life and GFI detectors
(* Indicates part is End Of Life as of July 1, 2000)
RSET
6
RT /CT
7
VARIABLE FREQUENCY
OSCILLATOR
RX/CX
9
PDWN
3
PRE-HEAT
AND INTERRUPT
TIMERS
CRAMP
10
PIFB
2
PEAO
1
PVFB/OVP
18
POWER
FACTOR
CONTROLLER
CONTROL
&
GATING LOGIC
OUTPUT
DRIVERS
INTERRUPT
8
LAMP FB
4
LFB OUT
5
OUT A
14
OUT B
13
PFC OUT
15
UNDER-VOLTAGE
AND THERMAL
SHUTDOWN
PGND
12
VCC
16
VREF
17
GND
11
1