ml4832 Microsemi Corporation, ml4832 Datasheet - Page 6

• Manufacturer Part Number: ml4832
• Description: Electronic Dimming Ballast Controller
• Manufacturer: Microsemi Corporation

ML4832
FUNCTIONAL DESCRIPTION
OVERVIEW
The ML4832 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 ML4832 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.
6
10
16
17
11
18
7
2
4
3
1
–1V
R
R
V
V
GND
IA OUT
IA +
I
EA OUT
EA –/OVP
SINE
SET
X
CC
REF
/C
X
2.5V
UNDER-VOLTAGE
–
+
–V
AND THERMAL
SHUTDOWN
MUL
7k
7k
+
MODULATORS
–
+
GAIN
–
+
2.75V
PREHEAT
TIMER
PWM (PFC)
+
–
Figure 1. ML4832 Block Diagram
OVP
–
+
FREQUENCY
VARIABLE
OSC
GAIN MODULATOR
The ML4832 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 series 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.
The output of the gain modulator is limited to 1.0V.
where: I
S
T
Q
Q
Q
R
VEA is the output of the error amplifier (Pin 1).
SINE
is the current in the dropping resistor,
V
MUL
I
SINE
34
.
VEA
mA
+
–
+
–
0 7
.
V
2.5V
V
REF
INTERRUPT
PFC OUT
LFB OUT
LAMP FB
P GND
OUT A
OUT B
R
T
/C
T
15
14
13
12
(1)
6
5
9
8