ML4831

5

PARAMETER

CONDITIONS

MIN

TYP

MAX

UNITS

OVP Comparator (Pin 18)

OVP Threshold

2.6

2.7

2.8

V

Hysteresis

0.25

V

Propagation Delay

500

ns

Outputs

Output Voltage Low

0.4

0.8

V

2.1

3.0

V

Output Voltage High

V

V

Output Voltage Low in UVLO

0.8

1.5

V

Output Rise/Fall Time

50

ns

Under-Voltage Lockout and Bias Circuits

12.8

13.5

14.2

V

150

300

mV

Load, Temp

12.4

14.6

V

Start-up Current

1.3

1.7

mA

Operating Current

15

19

mA

Start-up Threshold

V

Shutdown Threshold

V

120

°C

30

°C

FUNCTIONAL DESCRIPTION

OVERVIEW

The ML4831 consists of an Average Current controlled

continuous boost Power Factor front end section with a

flexible ballast control section. Start-up and lamp-out retry

timing are controlled by the selection of external timing

components, allowing for control of a wide variety of

different lamp types. The ballast section controls the lamp

power using frequency modulation (FM) with additional

programmability provided to adjust the VCO frequency

range. This allows for the IC to be used with a variety of

different output networks.

POWER FACTOR SECTION

The ML4831 Power Factor section is an average current

sensing boost mode PFC control circuit which is

architecturally similar to that found in the ML4821. For

detailed information on this control architecture, please

refer to Application Note 16 and the ML4821 data sheet.

GAIN MODULATOR

The ML4831 gain modulator provides high immunity to

the disturbances caused by high power switching. The

rectified line input sine wave is converted to a current via

a dropping resistor. In this way, small amounts of ground

noise produce an insignificant effect on the reference to

the PWM comparator.

The output of the gain modulator appears on the positive

terminal of the IA amplifier to form the reference for the

current error amplifier. Please refer to Figure 1.

V

I SINE

VEA

V

mA

×−

[]

() (

.

)

.

11

417

(1)

where: I(SINE) is the current in the dropping resistor,

V(EA) is the output of the error amplifier (Pin 1).

The output of the gain modulator is limited to 1.0V.