UBA2025T NXP [NXP Semiconductors], UBA2025T Datasheet - Page 5

• Manufacturer Part Number: UBA2025T
• Description: CFL power IC
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
UBA2025_1
Product data sheet
7.5 Ignition state
7.6 Failure to ignite
7.7 Transition to the burn state
capacitor connected to pin CI. The frequency during preheating will be approximately
90 kHz. This frequency is well above the resonant frequency of the load, which means
that the lamp is off. The load consists of L2, C5 and the electrode resistance only
(see
The circuit can be locked in the preheat state by connecting pin CPAV to ground. During
preheating the circuit monitors the load current by measuring the voltage drop over
external resistor R
frequency is decreased as long as V
V
The RS current monitoring function changes from V
protection at the end of the preheat time. Normally this results in a further frequency
decrease down to the bottom frequency f
change per ms is lowered with respect to the frequency change in the preheat mode.
During the downward frequency sweep the circuit sweeps through the resonant frequency
of the load. A high voltage will then appear across the lamp. This voltage will normally
ignite the lamp.
Excessive current levels may occur when the lamp fails to ignite. The IC does not limit
these currents in any manner.
Assuming that the lamp has ignited during the downward frequency sweep, the frequency
normally decreases to the bottom frequency. The IC can transit to the burn state in two
ways:
The bottom frequency is determined by resistor R
Fig 4.
RS
•
•
In the event that the bottom frequency is not reached, the transition is made after
reaching the ignition time t
As soon as the bottom frequency is reached.
< V
Figure
shunt
Operation in preheat mode
6). The preheat time is determined by the capacitor connected to pin CPAV.
.
SHUNT
Rev. 01 — 16 October 2009
f
start
f
btm
at the end of conduction of T2 with decision level V
ign
preheat state
.
RS
> V
btm
shunt
(approximately 43 kHz). The frequency
. The frequency is increased for
ignition
state
IREF
shunt
and capacitor CF.
regulation to capacitive mode
time
burn state
mgs992
UBA2025
© NXP B.V. 2009. All rights reserved.
CFL power IC
shunt
. The
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