UC2872DW Datasheet, PDF (1/11 Pages) Texas Instruments – Resonant Lamp Ballast Controller

Resonant Lamp Ballast Controller
application
INFO
available
UC1872
UC2872
UC3872
FEATURES
• Controls Different Types of Lamps:
Cold Cathode Fluorescent, Neon, and
Gas Discharge
• Zero Voltage Switching (ZVS) of
Push-Pull Drivers
• Accurate Control of Lamp Current
• Variable Lamp Intensity Control
• 1µA Disable Current
• 4.5V to 24V Operation
• Open Lamp Detection Circuitry
DESCRIPTION
The UC3872 is a resonant lamp ballast controller optimized for driving
cold cathode fluorescent, neon, and other gas discharge lamps. The res-
onant power stage develops a sinusoidal lamp drive voltage, and mini-
mizes switching loss and EMI generation. Lamp intensity adjustment is
accomplished with a buck regulator, which is synchronized to the external
power stage’s resonant frequency. Suitable for automotive and battery
powered applications, the UC3872 draws only 1µA when disabled.
Soft start and open lamp detect circuitry have been incorporated to mini-
mize component stresses. Open lamp detection is enabled at the comple-
tion of a soft start cycle. The chip is optimized for smooth duty cycle
control to 100%.
Other features include a precision 1.2% reference, undervoltage lockout,
and accurate minimum and maximum frequency control.
BLOCK DIAGRAM
VCC 10
UVLO
3.0V
REF
REF 9
ENBL 11
(HIGH=ENABLE)
COMP 4
0.1V +
–
INV ⁶
SS 5
–
20µA
EA
+
1.5V
200µA
OPEN
LAMP
DETECT
––
PWM
1
+
CT 7
OSCILLATOR
SENSE
ZERO DETECT
OUT
ZD 8
–
SYNC
0.5V +
0.2V
14
GND
Note: Pin numbers shown are for DIP package.
07/99
TOGGLE
T
PUSH PULL
OUTPUTS
N-CHANNEL
R
S
BUCK DRIVE
P-CHANNEL
3 VC
2 AOUT
50k
1 BOUT
50k
50k
12 COUT
13 PGND
UDG-99112