uba20270 NXP Semiconductors, uba20270 Datasheet - Page 15

• Manufacturer Part Number: uba20270
• Description: 600 V Driver Ic For Dimmable Compact Fluorescent Lamps
• Manufacturer: NXP Semiconductors

NXP Semiconductors
UBA20270
Product data sheet
7.4.2 OverCurrent Protection (OCP)
7.4.3 OverPower Protection (OPP)
7.4.4 Capacitive Mode Protection (CMP)
Coil saturation protection is triggered when the voltage on the SLS pin exceeds V
The voltage V
external resistor R
OCP is active in the burn and boost states (not during boost transition). When the peak
absolute value of the voltage across the current sense resistor on the SLS pin exceeds
the OCP reference level V
from the capacitor connected to the CP pin for the next full cycle. If the overcurrent is
absent at the end of this cycle, the current is disabled. Instead a current, also equal to
I
cycles, there is a net discharging of the capacitor connected to the CP pin. When the
voltage, on the CP pin is lower than V
continuous overcurrent condition, the overcurrent time-out of t
The IC then enters the power-down mode. The V
V
OPP is active in boost and burn state. The lamp current is limited and regulated to its
nominal designed lamp current in case overvoltage situations on the mains supply occur.
The overpower comes into action when the DCI voltage, that regulates the lamp current is
exceeding the maximum DCI input range. Internally the DCI voltage is clamped to the
maximum input voltage level V
independent of any supply voltage fluctuations.
CMP is active in the ignition, burn and boost states and during boost transition. The signal
across resistor R
half-bridge. When conditions are normal, the current flows from the source of the LS
transistor to the half-bridge when the LS transistor is switched on. This results in a
negative voltage on the SLS pin. As the circuit yields to capacitive mode, the voltage
decreases and eventually reverses polarity. The protection prevents this condition from
happening by checking if the voltage on the SLS pin is higher than V
If the voltage across resistor R
transistor is switched on, the circuit assumes that it is in capacitive mode. When
capacitive mode is detected, the currents from the OTA are disabled and the capacitive
mode sink current, I
circuitry on the CI pin and as a result gradually increase the half-bridge frequency.
Discharge continues for the remainder of the current switching cycle, so the total current
on CI is equal to the sink current. If capacitive mode persists, the action is repeated until
capacitive mode is not detected. If the capacitive mode is no longer detected, the OTA
starts regulating again.
If the conditions causing the capacitive mode persist, the OTA regulates the system back
towards capacitive mode with the protection system taking control. The system operates
on the edge of capacitive mode. During boost and burn state, if the load on the half-bridge
continues to be capacitive at higher frequencies, CMP eventually drives the half-bridge to
the maximum frequency f
o(CP)
th(sat)SLS
, is sourced to the CP pin. If the overcurrent occurs in more than half the number of
level during the ignition state.
SLS
All information provided in this document is subject to legal disclaimers.
SLS
on the SLS pin is also used to set the preheat current. The value of
SLS
o(sink)CI
also provides information about the switching behavior of the
Rev. 2 — 8 September 2011
determines this voltage.
bridge(max)
th(ocp)SLS
, is enabled. This sink current discharges the capacitor/resistor
600 V Driver IC for dimmable compact fluorescent lamps
SLS
T(hec3)DCI
is above the V
. From this point, the IC enters power-down mode.
, overcurrent is detected. A current I
th(CP)min
, see
Figure
the IC enters power-down mode. In a
th(capm)SLS
th(ocp)SLS
10. The DCI clamp level is
level corresponds with the
threshold when the LS
fault(oc)
UBA20270
th(capm)SLS
takes about
o(CP)
© NXP B.V. 2011. All rights reserved.
is then sunk
.
th(sat)SLS
1
⁄
10
15 of 32
t
ph.
.