uba20271 NXP Semiconductors, uba20271 Datasheet - Page 6

• Manufacturer Part Number: uba20271
• Description: 350 V And 600 V Power Ics For Dimmable Compact Fluorescent Lamps
• Manufacturer: NXP Semiconductors

NXP Semiconductors
UBA20271_UBA20272
Product data sheet
7.1.1 Reset state
7.1.2 Start-up state
7.1.3 Preheat state
7.1 Lamp start-up cycle
The UBA20271/2 are in a reset state while the supply voltage on the V
the V
counters and timers are undefined. In addition, the hold state latch is reset and both the
high and low-side transistor are non-conductive. During power-up, the low voltage supply
capacitor on the V
the V
enters the reset state when the supply voltage on the V
Start-up is achieved by charging the low voltage supply capacitor on the V
external start-up resistor. At start-up the High-Side (HS) transistor is non-conductive and
the Low-Side (LS) is conductive to enable charging of the bootstrap capacitor. This
capacitor supplies the HS driver and level shifter circuit connected between the FS and
HBO pin. A DC reset circuit is incorporated in the ICs HS driver. This circuit ensures that
lower than the lockout voltage on the FS pin the output voltage (V
As the start-up state is entered, the circuit only starts oscillating when the low voltage
supply (V
oscillating at f
The circuit enters the preheat state as soon as the capacitor on the CP pin is charged to a
voltage level higher than V
higher than V
voltage level on the DCI pin must be higher than V
An UnderVoltage LockOut (UVLO) is implemented on the DCI pin to create a guaranteed
turn-off for multiple lamps when the lamps are at low dim levels. The UVLO also
guarantees that there is a preheat phase when the dim level is turned up again.
The typical turn-on level on the DCI pin is set to lower than V
would increase the turn-on hysteresis of the lamp. This level enables the UBA20271/2 to
perform a stable ignition of the lamp when there is already sufficient power from the
dimmer at lower dim levels.
During the start-up state, the voltage on the CF pin is at zero and the CB pin is close to
zero. The voltage on the CP pin rises to higher than V
state. See
Starting at f
current circuit controlled by the preheat current sensor circuit. This state continues until
the momentary value of the voltage across sense resistor R
fixed preheat voltage level (SLS pin). At this level, the current of the preheat current
sensor reaches a charge and discharge balanced state on capacitor C
frequency.
DD(rst)
DD
pin is higher than the V
DD
Figure
level. In the reset state, a part of the internal supply is turned off, all registers,
bridge(max)
) reaches the value of V
DD(stop)
bridge(max)
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350 V and 600 V Power ICs for dimmable compact fluorescent lamps
9.
DD
, the frequency decreases by charging capacitor C
and lower than the upper limit V
pin is charged via an external start-up resistor. When the voltage on
Rev. 2 — 8 September 2011
.
th(CP)max
DD(rst)
. To remain oscillating, the V
DD(start)
level, the start-up state is entered. The UBA20271/2
AND V
i(DCI)
th(start)DCI
DD(clamp)
th(CP)max
DD
> V
pin drops lower than V
th(start)DCI
SLS
 V
th(start)DCI
. In addition, the typical
level during the start-up
DD
th(hys)DCI
UBA20271/2
reaches the internally
GHS
voltage must remain
. The circuit starts
DD
 V
= 0.36 V, else it
CI
© NXP B.V. 2011. All rights reserved.
CI
= 0.24 V.
to set the
pin is lower than
HBO
via an output
DD
pin via an
) is zero.
DD(rst)
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.