AN10881
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Application note
Rev. 2 — 26 September 2011
47 of 102
NXP Semiconductors
AN10881
TEA1713 resonant power supply control IC with PFC
The adaptive non-overlap system of the TEA1713 always waits until the slope at the
half-bridge node starts. It guarantees safe/best switching of the MOSFETs in all
circumstances. In Capacitive mode, it can take half the resonance period before the
resonant current changes back to the correct polarity and starts charging the half-bridge
node. The oscillator remains in its slow charging current mode until the half-bridge slope
starts to allow this relatively long waiting time (see also
and
The MOSFET is forced to switch on when the half-bridge slope does not start at all and
the slowed-down oscillator reaches the high level.
The Capacitive Mode Regulation (CMR) function increases the oscillation frequency to
bring the converter from Capacitive mode to Inductive mode operation again.
8.3.3 Capacitive Mode Regulation (CMR)
The adaptive non-overlap function prevents the harmful switching in Capacitive mode.
However, an extra action is executed, which results in the CMR to end the Capacitive
mode operation and return to Inductive mode operation.
Capacitive mode is detected when the HB slope does not start shortly (690 ns) after the
MOSFET is switched-off. At detection of Capacitive mode, the switching frequency is
increased quickly. This is realized by discharging SSHBC/EN with a high current
(1800
A) from the moment t
no-slope
= 690 ns has passed before the half-bridge slope
starts. The resulting frequency increase regulates the HBC back to the border between
Capacitive mode and Inductive mode.
Fig 24. Capacitive mode HBC switching
0
t
001aal034
delayed
oscillator
delayed switch-on
during capacitive mode
no HB slope
wrong polarity
GateHs
GateLs
0
V
Boost
Hb
0
0
0
I
TrHbc
Cfmin
