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AN10881
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© NXP B.V. 2011. All rights reserved.
Application note
Rev. 2 — 26 September 2011
46 of 102
NXP Semiconductors
AN10881
TEA1713 resonant power supply control IC with PFC
The non-overlap time depends on the HB slope, but has an upper and lower time limit. An
integrated minimum non-overlap time (160 ns
max
) prevents accidental cross conduction in
all conditions. The maximum non-overlap time is limited to the charging time of the
oscillator. If the HB slope takes more time than the charging of the oscillator (25 % of HB
switching period) the MOSFET is forced to switch on. In this case the MOSFET is not
soft-switching. This limitation of the maximum non-overlap time ensures that at high
switching frequency the on-time of the MOSFET is at least 25 % of the HB switching
period.
8.3.2 Capacitive mode
During error conditions (e.g. output short circuit, load pulse too high) or special start-up
conditions, the switching frequency can become lower than the resonance frequency. The
resonant tank then has a capacitive impedance. In Capacitive mode the HB slope does
not start after the MOSFET has switched off. It is not preferred to just switch on the other
MOSFET. The lack of soft-switching increases dissipation in the MOSFETs. The
conducting body diode in the MOSFET at the switching moment can damage or even
destroy the device quickly.
Fig 23. Adaptive non-overlap switching during normal operating conditions
fast HB slope
V
Boost
Hb
GateLs
GateHs
0
slow HB slope
incomplete HB slope
t
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