UBA2017P/1,112 NXP Semiconductors, UBA2017P/1,112 Datasheet - Page 14

• Manufacturer Part Number: UBA2017P/1,112
• Description: Display Drivers & Controllers SMPS CTRLR 12.4V
• Manufacturer: NXP Semiconductors

Specifications of UBA2017P/1,112

• Rohs: yes
• Operating Supply Voltage: 12.4 V
• Mounting Style: Through Hole
• Package / Case: DIP-16
• Maximum Output Current: 105 mA
• Product: Fluorescent Lamp Driver
• Factory Pack Quantity: 25
• Supply Current: 2.2 mA

NXP Semiconductors
UBA2017
Product data sheet
7.5.3 Capacitive mode detection
7.5.4 Hard switching protection
The end-of-life overvoltage protection is only active during the Burn state and (for
UBA2017A) 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.
To protect against capacitive mode switching, the IC monitors pin SHHB during the
non-overlap time t
high-side switch. If a rise of V
detected, 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
then the IC will enter the Stop state.
Capacitive mode detection is active in all oscillating states.
During ignition, a situation may occur where the amplitude of the load current is high and
the half-bridge is at the boundary of capacitive mode switching; see
The load current crosses zero during the non-overlap time. If the amplitude of the load
current is large enough, the IC might not detect capacitive mode because V
before going down again. The backgate diode of one switch is conducting again when the
other switch switches on. Since this can only happen if the load current crosses zero
during the non-overlap time, the momentary value of the load current at the end of the
non-overlap time will be not so significant, and is not likely to damage the switches.
Depending on the topology used, the DC blocking capacitor might be charged via the
lamp(s) at the moment the lamp(s) ignite. This will cause a temporary DC current addition
to the load current that might be interpreted by the IC as capacitive mode switching. If this
happens, the DC blocking capacitor must be reduced or pre-charged.
The hard switching level V
level is determined by measuring the voltage step on pin SHHB on the rising edge of pin
GHHB; see
threshold voltage on pin SHHB (V
en(oveol)(DIM)
no(HL)
. As a result, the voltage across the switches is almost zero at the moment they
Figure 9
.
All information provided in this document is subject to legal disclaimers.
no(LH)
“Switching”. When V
load
between switching off the low-side switch and switching on of the
Rev. 2 — 15 May 2012
lags behind the half-bridge voltage V
step(SHHB)
600 V fluorescent lamp driver with linear dimming function
SHHB
th(hswp)SHHB
(dV
no(LH)
step is measured via pin SHHB. The hard switching
SHHB
, and discharge it during the other non-overlap
step(SHHB)
/dt > V
), the fault timer is activated.
UBA2017/UBA2017A
th(cm)(SHHB)
Figure 9
is above the hard switching protection
“Switching”. Zero voltage
) during t
SHHB
. If the amplitude and
Figure 9
no(LH)
© NXP B.V. 2012. All rights reserved.
is not
SHHB
“Switching”.
did rise
det(fault)
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