UBA2024 NXP Semiconductors, UBA2024 Datasheet - Page 4

• Manufacturer Part Number: UBA2024
• Description: Half-bridge Power Ic For Cfl Lamps
• Manufacturer: NXP Semiconductors

Philips Semiconductors
When entering the sweep mode, the oscillator starts at
2.5 times the nominal bridge frequency and sweeps down
to the nominal bridge frequency f
continuously decreasing of the frequency, the circuit
approaches the resonance frequency of the load. This
causes a high voltage across the load, which normally
ignites the lamp.
The sweep time t
I
resonance time should be much larger than the settling
time of the supply voltage on pin HV to guarantee that the
full high-voltage is present at the moment of ignition.
The amplitude of the RC oscillator is equal to the minimum
value of V
During the sweep time a current is flowing through the
lamp electrodes for pre-heating the filaments.
2004 Feb 03
handbook, halfpage
ch(sw)
Half-bridge power IC for CFL lamps
V OUT
bridge
drive
drive
V RC
half
and the external capacitor C
HS
LS
Fig.3 Oscillator, drivers and output signals.
0
0
0
0
RC(h)
and V
sweep
SW
is determined by the charge current
+ 0.4
nom
V
RC(h)
SW
; see Fig.4. During this
. The sweep to
.
MDB031
time
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4
Glow time control
The drawback of cold-started CFL lamps is its inherent
glow time which reduces the switching lifetime of the
electrodes (lamp). To make this glow phase as short as
possible, the maximum power is given to the lamp during
the glow time via a special control; see Fig.4.
Non-overlap time
The non-overlap time is defined as the time that both
MOSFETs are not conducting. The non-overlap time is
internally fixed.
handbook, halfpage
V DD(start)
0.8V RC(h)
2.5f nom
V lamp
V glow
V nom
V SW
f nom
V DD
V DD
V HV
V ign
f osc
0
0
0
0
Fig.4 Start-up frequency behaviour.
minimum glow time control
t sweep
Product specification
UBA2024
MDB032
time
time
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