AN10907
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© NXP B.V. 2010. All rights reserved.
Application note
Rev. 1 — 28 December 2010
43 of 82
NXP Semiconductors
AN10907
TEA1613T resonant power supply control IC
frequency restores safe switching operation. Once the voltage at pin SSHBC/EN has
reached 3.2 V, the control input of the oscillator is connected to the pin again and the
normal soft-start sweep follows.
shows the soft-start reset and the two-speed
frequency downward sweep.
The soft-start reset is also used to ensure a safe start-up at maximum frequency when the
HBC is enabled by SSHBC/EN or after a restart. The soft-start reset is not used when the
operation is stopped for burst mode.
8.7 Overcurrent protection and regulation HBC
Measurement of the primary resonant current indicates the level of output power that is
being generated by the converter. In case of a fault or output overload condition, this
current often increases considerably. By monitoring this current and then taking the
appropriate action, the converter can remain operational.
The resonant controller of the TEA1613T has two functions when in an over-current
condition:
•
OverCurrent Regulation (OCR) slowly increases the frequency and the protection
timer is started
•
OverCurrent Protection (OCP) steps immediately to maximum frequency
A boost voltage compensation function is included to reduce the variation in the preset
protection level of the resonant current.
Fig 29. Soft-start reset and two-speed soft-start
Protection
0
3.2 V
typ
V
SSHBC/EN
8 V
typ
0
f
min
f
HB
f
max
t
off
on
f
max
forced
fast
sweep
slow sweep
regulation
regulation
5.6 V
typ
001aal453
