UBA2025 NXP Semiconductors, UBA2025 Datasheet - Page 6

• Manufacturer Part Number: UBA2025
• Description: Cfl Power Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
UBA2025_1
Product data sheet
7.10 IC supply
7.11 Minimum gate source voltage of T1 and T2
7.8 Feed forward frequency
7.9 Capacitive mode
Above a defined voltage level at pin VDC the oscillation frequency also depends on the
supply voltage of the half bridge (see
oscillator is in this feed forward range and is derived from the current through R
similar to pin RHV current). The feed forward frequency is proportional to the average
value of the current (within its operating range) through R
is clamped for currents beyond the operating range (i.e. between 1.0 mA and 1.6 mA). In
order to prevent feed forward of the ripple on the input voltage on pin VDC, the ripple is
filtered out. The capacitor connected to pin CPAV is used for this purpose. This pin is also
used in the preheat state and the ignition state for timing (t
When the preheat mode is completed, the IC will protect the power circuit against losing
the zero voltage switching condition and getting too close to the capacitive mode of
operation. This is detected by monitoring the voltage across R
pin RS is below V
of T2, then capacitive mode operation is assumed. Consequently, the frequency will be
increased as long as the capacitive mode is detected. The frequency decreases down to
the feed forward frequency if no capacitive mode is detected. Frequency modulation is
achieved via pin CI.
Initially, the IC is supplied from the bus voltage VDC by the current through R
current charges the supply capacitor CS9 via an internal diode. As soon as VS exceeds
V
connected to an internal resistor (R
pin VS. The voltage level at pin RHV thus drops from (VS + V
RHV pin current
capacitor CS7. Excess charge is drained by an internal clamp that turns on at the clamp
voltage (V
The high side driver is supplied via capacitor C
switch during the on-periods of T2. The IC stops oscillating at a voltage level V
a maximum charge consumption on the gate of T1 (G1) of 1 nC/V, this safeguards the
minimum drive voltages V
Fig 5.
startup
, the circuit starts oscillating. After the preheat phase is finished, pin RHV is
Feed forward frequency
clamp
) on pin VS.
th(capm)
R
RHV
Rev. 01 — 16 October 2009
(kHz)
. The capacitor CS9 at pin VS will now be charged via the snubber
the capacitive mode threshold voltage at the time of turn-on
f
(G1-S1)
frequency
bottom
for the high side driver; see
RHV
Figure
); prior to this the pin is internally connected to
5). The current for the current controlled
BOOT
. C
BOOT
feed-forward
I
HV
RHV
ph
range
. The feed forward frequency
is charged via the bootstrap
Table
(mA)
and t
mgs993
d
SHUNT
) to a voltage equal to the
ign
3.
. If the voltage at
).
UBA2025
© NXP B.V. 2009. All rights reserved.
CFL power IC
HV
stop
HV
. This
. Given
(this is
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