UBA2015 PHILIPS [NXP Semiconductors], UBA2015 Datasheet - Page 19

• Manufacturer Part Number: UBA2015
• Description: 600 V fluorescent lamp driver with PFC, linear dimming and boost function
• Manufacturer: PHILIPS [NXP Semiconductors]

NXP Semiconductors
UBA2016A_15_15A
Product data sheet
7.6.2 End-of-life overvoltage detection
7.6.3 Capacitive mode detection
A programmable end-of-life window is achieved by the internal bias current sink I
The effective relative size of the EOL window will decrease in line with the increasing
series resistance connected to pin EOL.
The end-of-life lamp rectifying detection is only active during the Burn state.
This protection is intended to protect against symmetrical lamp aging. When in Burn state
the voltage on pin VFB exceeds the overvoltage end-of-life threshold voltage V
by more then 50 % of each switching cycle the fault timer will start. V
to the regulation voltage on pin IFB V
DIM (see
V
Parameters a and b can be calculated from the V
The end-of-life overvoltage protection is only active during Burn state and (for UBA2015A
and UBA2016A) if the voltage at pin DIM is above the overvoltage end-of-life enable
voltage V
Under all normal operating conditions the half-bridge switching frequency should be
higher than the load resonance frequency. The load then shows an inductive behavior in
that the load current I
the phase difference are large enough, the load current will charge any capacitance on pin
SHHB during the non-overlap time t
time t
turn on. This is called zero voltage switching; see
switching provides the highest switching efficiency and the least Electromagnetic
Emission (EME).
Capacitive mode switching can occur when, due to any abnormal condition, the switching
frequency is below the load resonance frequency. This can happen when the lamp is
removed. The load current will then keep the backgate diode of the switch that is switched
off conducting during the non-overlap time, and if the other switch is turned on, a sudden
step of the half-bridge voltage to the other supply rail takes place (which causes huge
current spikes). Also cross conduction between the switches can occur during the reverse
recovery of the backgate diode. These effects put huge stress on the power switches,
most of which can only handle capacitive mode switching a few times before they break
down.
To protect against capacitive mode switching the IC monitors pin SHHB during the
non-overlap time t
the high-side switch. If a rise of V
detected then the IC will conclude that capacitive mode switching is occurring during the
next full cycle. If capacitive mode is detected longer than the fault activation delay time
t
Capacitive mode detection is active in all oscillating states for all ICs except in the Ignition
state of the UBA2016A if zero voltage switching has been observed. In that case the
UBA2016A switches to hard switching regulation, see
regulation
det(fault)
th(oveol)(VFB)
no(HL)
then the IC will enter Stop state.
en(oveol)(DIM)
Section 7.4.7.1 “Lamp current control and
(UBA2016A)”.
. As a result the voltage across the switches is almost zero at the moment they
= a  b  V
All information provided in this document is subject to legal disclaimers.
no(LH)
.
load
Rev. 3 — 16 November 2011
between switching off of the low-side switch and switching on of
reg(IFB)
lags behind the half-bridge voltage V
SHHB
no(LH)
reg(IFB)
(dV
, and discharge it during the other non-overlap
SHHB
that itself is dependent on the voltage on pin
/dt > V
th(oveol)(VFB)
Figure 14
UBA2016A/15/15A
dimming”) according to the formula:
th(cm)(SHHB)
Section 7.6.4 “Hard switching
600 V fluorescent lamp driver
“Switching”. Zero voltage
values given in
SHHB
) during t
. If the amplitude and
th(oveol)(VFB)
© NXP B.V. 2011. All rights reserved.
no(LH)
Table
th(oveol)(VFB)
is not
is related
bias(EOL)
6.
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