July 2000
PRELIMINARY
ML4835*
Compact Fluorescent Electronic Dimming
Ballast Controller
GENERAL DESCRIPTION
The ML4835 is a complete solution for a dimmable or a
non-dimmable, high power factor, high efficiency
electronic ballast especially tailored for a compact
fluorescent lamp (CFL). The Bi-CMOS ML4835 contains
controllers for “boost” type power factor correction as
well as for a dimming ballast with end-of-lamp life
detection.
The PFC circuits uses a new , simple PFC topology which
requires only one loop for compensation. In addition,
this PFC can be used with either peak- or average-current
mode. This system produces a power factor of better than
0.99 with low input current THD.
The ballast controller section provides for programmable
starting sequence with individual adjustable preheat and
lamp out-of-socket interrupt times. The ML4835 provides
a shut down for both PFC and ballast controllers in the
event of end-of-life for the CFL.
FEATURES
s
s
s
s
s
s
s
s
s
s
Power detect for end-of-lamp-life detection
Low distortion , high efficiency continuous boost, peak
or average current sensing PFC section
Leading- and trailing-edge synchronization between
PFC and ballast
One to one frequency operation between PFC and
ballast
Programmable start scenario for rapid/instant start lamps
Triple frequency control network for dimming or
starting to handle various lamp sizes
Programmable restart for lamp out condition to reduce
ballast heating.
Internal over-temperature shutdown
PFC over-voltage comparator eliminates output
“runaway” due to load removal
Low start-up current; < 0.55mA
(* Indicates Part is End Of Life as of July 1, 2000)
BLOCK DIAGRAM
13
4
3
2
PVFB/OVP
1
RSET
RT/CT
RT2
CRAMP
PIFBO
PIFB
PEAO
POWER
FACTOR
CONTROLLER
ANTI-FLASH
COMPENSATION
AND
POWER DIMMING LEVEL
INTERFACE
CONTROL
AND
GATING
LOGIC
INTERRUPT
10
LAMP FB
5
LEAO
6
OUT A
VARIABLE FREQUENCY
OSCILLATOR
THREE-FREQUENCY
CONTROL SEQUENCER
VCO
PRE-HEAT AND
INTERRUPT TIMERS
END-OF-LAMP DETECT
AND
POWER SHUTOFF
UNDER-VOLTAGE
AND
THERMAL SHUTDOWN
AGND
REF
14
20
VCC
19
LAMP OUT DETECT
AND
AUTOMATIC LAMP
RESTART
RX/CX
11
OUTPUT
DRIVERS
17
OUT B
16
PFC OUT
18
PGND
15
7
9
8
PWDET
12
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
