UBA2016A_15_15A All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved.
Product data sheet Rev. 3 — 16 November 2011 12 of 42
NXP Semiconductors
UBA2016A/15/15A
600 V fluorescent lamp driver
7.4.1 Reset
When voltage on pin VDD is below the reset voltage V
rst(VDD)
, both gates of the half-bridge
driver are LOW. All internal latches are reset. When voltage on pin VDD rises above
V
rst(VDD)
, the IC will enter STANDBY state.
7.4.2 Standby
In STANDBY state the low-side gate driver is on (GLHB is HIGH).The floating supply
capacitor C
FSHB
is then charged. When the VDD voltage rises above V
startup(VDD)
, the
Preheat state is entered.
7.4.3 Oscillating states (Preheat, Ignition and Burn)
The highest and lowest oscillation frequency can be set with capacitor C
CF
connected to
the CF pin. The oscillator is implemented in such a way that the lowest frequency f
sw(low)
is
the most accurate. In any oscillating state (Preheat, Ignition or Burn), when VDD voltage
drops below V
stop(VDD)
or overtemperature is detected, the half-bridge stops oscillation
when GLHB is HIGH and enters the STANDBY state.
7.4.4 Preheat
The oscillating frequency starts at f
sw(high)
(see Figure 10 “Resonance curve application
with UBA2015A” or Figure 11 “Resonance curve application with UBA2016A” point A) and
remains at that frequency until the PFC output is sufficient (the voltage at pin FBPFC rises
above the PFC voltage OK threshold voltage on pin FBPFC, V
th(VPFCok)FBPFC
) and the
voltages at pins CPT and VFB settle above their pin short protection levels
(V
VFB
> V
th(osp)(VFB)
and V
CPT
> V
th(scp)(CPT)
). The half-bridge current is regulated when in
the Preheat state; see Figure 10 “
Resonance curve application with UBA2015A” or Figure
11 “Resonance curve application with UBA2016A” point B. Pin CIFB supplies a current
I
ch(CIFB)
to the externally connected compensation network on this pin and its voltage will
rise. This will cause the switching frequency to decrease (pin CIFB is the input for the
voltage controlled oscillator). This will cause an increase in half-bridge current (assuming
the switching frequency is higher than the load resonance frequency). This current is
measured via pin SLHB using a resistor connected between the source of the low-side
switch and ground. When the voltage on pin SLHB rises above the preheat current control
voltage V
crtl(ph)SLHB
, discharge current I
dch(CIFB)
to pin CIFB and the frequency is
increased. When the voltage drops below V
th(ocp)SLHB
, current I
ch(CIFB)
from pin CIFB
causes the frequency to decrease.
