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.

* This product is End Of Life as of July 1, 2000

FEATURES

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Complete Power Factor Correction and Dimming

Ballast Control on one IC

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Low Distortion, High Efficiency Continuous Boost,

Average Current sensing PFC section

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Programmable Start Scenario for Rapid or Instant Start

Lamps

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Lamp Current feedback for Dimming Control

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Variable Frequency dimming and starting

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Programmable Restart for lamp out condition to

reduce ballast heating

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Over-Temperature Shutdown replaces external heat

sensor for safety

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PFC Over-Voltage comparator eliminates output

“runaway” due to load removal

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Large oscillator amplitude and gain modulator

improves noise immunity

BLOCK DIAGRAM

JULY 2000

ML4831

*

Electronic Ballast Controller

1

7

R(SET)

OSCILLATOR

8

R(T)/C(T)

10

R(X)/C(X)

PRE-HEAT

AND INTERRUPT

TIMERS

CONTROL

&

GATING LOGIC

2

IA OUT

4

IA+

POWER

FACTOR

CONTROLLER

UNDER-VOLTAGE

AND THERMAL

SHUTDOWN

OUTPUT

DRIVERS

3

I(SINE)

1

EA OUT

18

EA–/OVP

17

PFC OUT

15

GND

11

VCC

16

PGND

12

OUT B

13

OUT A

14

LFB OUT

6

LAMP F.B.

5

INTERRUPT

9