uba20261 NXP Semiconductors, uba20261 Datasheet - Page 14

• Manufacturer Part Number: uba20261
• Description: 600 V And 350 V Power Ic For Step Dimmable Cfls
• Manufacturer: NXP Semiconductors

NXP Semiconductors
UBA20261_UBA20262
Preliminary data sheet
7.4.1 Coil saturation protection
7.4 Protection functions and Power-down mode
As the internal step reference voltages are independent from the mains voltage, the lamp
current output is kept constant. Making the lamp current output not susceptible to line
voltage fluctuations. The MDL level sets the minimum lamp current level and is adjusted
using the MDL pin. An accurate minimum dimming voltage level is set using an internal
reference current and an external resistor R
from the internal band gap reference circuit and resistor R
dimming levels are set at a fixed voltage offset referenced to the adjusted MDL level. This
means that these levels shift by the same voltage as the MDL shifts. When the MDL level
is at the default level, the light output in DIM_2, DIM_3 and MDL modes is approximately
66 %, 33 % and 5 % from nominal.
CSP is integrated into the IC to allow the use of small CFL lamps and use of small coils.
Saturation of these coils is detected and excessive overcurrent due to saturation is
prevented. CSP is only enabled during the ignition state. A cycle-by-cycle control
mechanism is used to limit voltages and currents in the resonant circuit when there is no
or delayed ignition. It prevents coil saturation, limits high peak currents and the dissipation
in the half-bridge power transistors.
Coil saturation is detected by monitoring the voltage across the R
generated when this voltage exceeds the V
fixed current I
Fig 11. Voltage on the CSI pin as function of dim step
V
i(CSI)
o(sat)CF
All information provided in this document is subject to legal disclaimers.
= V
MDL
Rev. 1 — 9 September 2011
1.2
1.0
0.8
0.6
0.4
0.2
is injected into the C
0
V
V
i(CSI)
RMS
(1) = V
V
Internal clamp
clamp(CSI)
∆V
DD
dim2(CSI)
∆V
off-on toggle
dim3(CSI)
600 V and 350 V power IC for step dimmable CFLs
V
DD
CF
th(sat)SLS
MDL
off-on toggle
capacitor to shorten the half-bridge
. The internal reference current is derived
DIM_1
DIM_2
DIM_3
100 %
level. When saturation is detected, a
MDL
(1)
ext(RREF)
(1)
UBA20261/2
V
001aam770
DD
SLS
. The other two step
off-on toggle
resistor. A trigger is
© NXP B.V. 2011. All rights reserved.
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