JULY 2000
ML4831*
Electronic Ballast Controller
GENERAL DESCRIPTION
The ML4831 is a complete solution for a dimmable, high
power factor, high efficiency electronic ballast. Contained
in the ML4831 are 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 over-voltage
protection. This system produces power factors of better
than 0.99 with low input current THD at > 95%
efficiency. Special care has been taken in the design of the
ML4831 to increase system noise immunity by using a
high amplitude oscillator, and a current fed multiplier. An
over-voltage 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 either frequency modulation using lamp current
feedback.
The ML4831 is designed using Micro Linear‘s Semi-
Standard tile array technology. Customized versions of this
IC, optimized to specific ballast architectures can be made
available. Contact Micro Linear or an authorized
representative for more information.
FEATURES
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Complete Power Factor Correction and Dimming
Ballast Control on 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 Over-Voltage comparator eliminates output
“runaway” due to load removal
Large oscillator amplitude and gain modulator
improves noise immunity
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* This product is End Of Life as of July 1, 2000
BLOCK DIAGRAM
7
8
R(SET)
R(T)/C(T)
OSCILLATOR
INTERRUPT
LAMP F.B.
LFB OUT
9
5
6
OUTPUT
DRIVERS
R(X)/C(X)
PRE-HEAT
AND INTERRUPT
TIMERS
OUT A
CONTROL
&
GATING LOGIC
OUT B
14
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
VCC
V
REF
GND
15
12
16
17
11
1
MICRO-LINEAR [ MICRO LINEAR CORPORATION ]
