UBA2021 NXP Semiconductors, UBA2021 Datasheet - Page 5

• Manufacturer Part Number: UBA2021
• Description: 630 V Driver Ic For Cfl And Tl Lamps
• Manufacturer: NXP Semiconductors

Philips Semiconductors
FUNCTIONAL DESCRIPTION
Introduction
The UBA2021 is an integrated circuit for electronically
ballasted compact fluorescent lamps and their derivatives
operating with mains voltages up to 240 V (RMS). It
provides all the necessary functions for preheat, ignition
and on-state operation of the lamp. In addition to the
control function, the IC provides level shift and drive
functions for the two discrete power MOSFETs, T1 and T2
(see Fig.7).
Initial start-up
Initial start-up is achieved by charging capacitor CS9 with
the current applied to pin RHV. At start-up, MOSFET T2
conducts and T1 is non-conducting, ensuring C
becomes charged. This start-up state is reached for a
supply voltage V
at which the circuit will be reset to the initial state) and
maintained until the low voltage supply (V
value of V
Oscillation
When the low voltage supply (V
of V
The internal oscillator is a current-controlled circuit which
generates a sawtooth waveform. The frequency of the
sawtooth is determined by the capacitor C
current out of pin CF (mainly set by R
frequency is twice the frequency of the signal across the
load. The IC brings MOSFETs T1 and T2 alternately into
conduction with a duty factor of approximately 50%.
Figure 4 represents the timing of the IC. The circuit block
'non-overlap' generates a non-overlap time t
ensures conduction periods of exclusively T1 or T2. Time
t
2002 Aug 02
no
630 V driver IC for CFL and TL lamps
is dependent on the reference current I
VS(start)
VS(start)
the circuit starts oscillating in the preheat state.
VS(reset)
. The circuit is reset in the start-up state.
(this is the voltage level at pin VS
VS
) has reached the value
RREF
VS
). The sawtooth
CF
RREF
) reaches a
no
and the
that
.
boot
5
Operation in the preheat mode
The circuit starts oscillating at approximately 2.5
(108 kHz). The frequency gradually decreases until a
defined value of current I
slope of the decrease in frequency is determined by
capacitor C
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. The preheat time is determined by
capacitor C
state by connecting pin CP to ground. During preheating,
the circuit monitors the load current by measuring the
voltage drop over external resistor R
conduction of T2 with decision level V
frequency is decreased as long as V
frequency is increased for V
handbook, halfpage
V (G1-S1)
internal
V (G2)
clock
V CF
0
0
0
0
CI
CP
. The frequency during preheating is
. The circuit can be locked in the preheat
start-up
Fig.4 Oscillator timing.
shunt
t no
RS
is reached (see Fig.5). The
< V
RS(ctrl)
shunt
RS
Product specification
RS(ctrl)
> V
.
UBA2021
at the end of
t no
RS(ctrl)
. The
time
MGS991
. The
f
B