UBA2028T NXP [NXP Semiconductors], UBA2028T Datasheet - Page 6

• Manufacturer Part Number: UBA2028T
• Description: 600 V dimmable power IC for compact fluorescent lamps
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
UBA2028_1
Product data sheet
8.8.1 During ignition state
8.8.2 During burn state
8.5 Preheat state
8.6 Ignition state
8.7 Burn state
8.8 Lamp failure mode
After starting at f
across sense resistor R21 (see
preheat voltage level (pin PCS). Detection of the pre-heat voltage occurs during the end of
the ‘on-time’ of the low side switch TR2 when the internal pre-heat fixed voltage reference
level is exceeded. Once detection has occurred the output current of the Preheat Current
Sensor (PCS) circuit discharges the capacitor C
internal pre-heat control is reset during each “on-time’ of the high side switch TR1, thus
C
detection occurs. The preheat time begins at the moment that the circuit starts oscillating.
During the preheat time the Average Current Sensor (ACS) circuit is disabled. An internal
filter of 30 ns is included at pin PCS to increase the noise immunity.
After the preheat time the ignition state is entered and the frequency will sweep down due
to charging of the capacitor at pin CSW with an internally fixed current; see
During this continuous decrease in frequency, the circuit approaches the resonant
frequency of the load. This will cause a high voltage across the load, which normally
ignites the lamp. The ignition voltage of a lamp is designed above the V
lamp voltage exceeds the V
If the lamp voltage does not exceed the V
continue to increase until the clamp level at pin CSW is reached; see
consequence the frequency will decrease until the minimum frequency is reached.
When the frequency reaches its minimum level it is assumed that the lamp has ignited and
the circuit will enter the burn state. The Average Current Sensor (ACS) circuit will be
enabled. As soon as the averaged voltage across sense resistor R21 (see
(Figure
current sensor circuit will take over the control of the lamp current. The average current
through R21 or R5 is transferred to a voltage at the voltage controlled oscillator and
regulates the frequency and, as a result, the lamp current.
If the lamp does not ignite, the voltage level increases. When the lamp voltage exceeds
the V
When the V
pin LVS is above the V
oscillating and is forced into the Power-down mode. The circuit will be reset only when the
supply voltage is powered down.
If the lamp fails during normal operation, the voltage across the lamp will increase and the
lamp voltage will exceed the V
is started. If the lamp voltage increases further it will reach the V
the circuit to re-enter the ignition state and results in an attempt to re-ignite the lamp. If
CSW
lamp(max)
is charged, and the frequency decreases. It remains in this condition when no
9), measured at pin CSN, reaches the reference level at pin CSP, the average
lamp(fail)
level, the voltage will be regulated at the V
max
level is crossed the ignition timer has already started. If the voltage at
, the frequency decreases until the momentary value of the voltage
Rev. 01 — 9 October 2009
lamp(fail)
lamp(fail)
600 V dimmable power IC for compact fluorescent lamps
lamp(fail)
level at the end of the ignition time the circuit stops
Figure
level the ignition timer is started.
level; see
8) or R5
lamp(max)
Figure
(Figure
CSW
level the voltage at pin CSW will
, thus raising the frequency. The
6. At that moment the ignition timer
9) reaches the internally fixed
lamp(max)
lamp(max)
level; see
Figure
UBA2028
lamp(fail)
© NXP B.V. 2009. All rights reserved.
level. This forces
Figure
Figure
Figure
4. As a
level. If the
8) or R5
5.
4.
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