uba20271 NXP Semiconductors, uba20271 Datasheet - Page 14

• Manufacturer Part Number: uba20271
• Description: 350 V And 600 V Power Ics For Dimmable Compact Fluorescent Lamps
• Manufacturer: NXP Semiconductors

NXP Semiconductors
UBA20271_UBA20272
Product data sheet
7.4.1 Coil saturation protection
7.4 Protection and power-down
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 R
generated when this voltage exceeds the V
fixed current I
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 C
ignition time-out detection in the ignition state.
Coil saturation protection is triggered when the voltage on the SLS pin exceeds V
The voltage V
external resistor R
Fig 10. CSI voltage as a function of DCI voltage
V
[V
i(CSI)
RMS
(1) V
midcurve
]
MDL
1.2
1.0
0.8
0.6
0.4
0.2
i(CSI)
voltage
0
(V)
0
SLS
= V
o(sat)CF
V
All information provided in this document is subject to legal disclaimers.
V
350 V and 600 V Power ICs for dimmable compact fluorescent lamps
clamp(CSI)
T(hec1)DCI
LD
on the SLS pin is also used to set the preheat current. The value of
SLS
= f(V
0.2
Rev. 2 — 8 September 2011
determines this voltage. With an internal reference source current
is injected into the C
V
th(hys)DCI
i(DCI)
V
th(start)DCI
)
0.4
V
T(hec2)DCI
0.6
CF
(1)
th(sat)SLS
capacitor to shorten the switching cycle of
0.8
0.9
level. When saturation is detected, a
V
LD
1.0
CI
100 %
1.2
is discharged to enable an
UBA20271/2
V
SLS
T(hec3)DCI
resistor. A trigger is
1.4
© NXP B.V. 2011. All rights reserved.
V
internal
clamp
i(DCI)
001aam671
(V)
1.6
th(sat)SLS
voltage
14 of 33
(V)
.