UBA20272T データシートの表示（PDF） - NXP Semiconductors.
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UBA20272T Datasheet PDF : 33 Pages
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NXP Semiconductors
UBA20271/2
350 V and 600 V Power ICs for dimmable compact fluorescent lamps
voltage
(V)
1.2
Vi(CSI)
[VRMS]
1.0
Vclamp(CSI)
(1)
internal
clamp
100 %
0.8
0.6
VLD
0.4
midcurve
0.2
MDL
0
0
Vth(hys)DCI
0.2
0.4
0.6
0.8
1.0
VT(hec1)DCI
VT(hec2)DCI
0.9
Vth(start)DCI
(1) Vi(CSI) = VLD = f(Vi(DCI))
Fig 10. CSI voltage as a function of DCI voltage
voltage
(V)
1.2
1.4
1.6
Vi(DCI) (V)
VT(hec3)DCI
001aam671
7.4 Protection and power-down
7.4.1 Coil saturation protection
Coil saturation protection is integrated into the IC to allow for 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. Coil saturation protection is only enabled during the ignition
state. To limit voltages and currents in the resonant circuit when there is no ignition or
delayed ignition, a cycle-by-cycle control mechanism is used to prevent coil saturation.
This control also limits the high peak current and dissipation in the half-bridge power
transistors.
Coil saturation is detected by monitoring the voltage across the RSLS resistor. A trigger is
generated when this voltage exceeds the Vth(sat)SLS level. When saturation is detected, a
fixed current Io(sat)CF is injected into the CCF capacitor to shorten the switching cycle of
the half-bridge. The injected current is maintained until the end of the switching cycle. This
action immediately increases the half-bridge switching frequency. Furthermore, in each
successive cycle that coil saturation is detected, capacitor CCI is discharged to enable an
ignition time-out detection in the ignition state.
Coil saturation protection is triggered when the voltage on the SLS pin exceeds Vth(sat)SLS.
The voltage VSLS on the SLS pin is also used to set the preheat current. The value of
external resistor RSLS determines this voltage. With an internal reference source current
UBA20271_UBA20272
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2.1 — 12 October 2011
© NXP B.V. 2011. All rights reserved.
14 of 33
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