AN10881
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© NXP B.V. 2011. All rights reserved.
Application note
Rev. 2 — 26 September 2011
50 of 102
NXP Semiconductors
AN10881
TEA1713 resonant power supply control IC with PFC
The similarity between GATELS and GATEHS when switching, is that the oscillator signal
determines the moment of switching off. The HB sensing circuit determines the moment of
switching on.
As the HB sensing (and therefore not fixed) determines the moment of switching on, the
time between switching one MOSFET off and the other one on, is adaptive: adaptive
non-overlap time (or dead time). This non-overlap time has no influence on the oscillator
signal.
The frequency control by oscillator-frequency consists of determining the time between
two moments of switching off (including a small period in which the oscillator current is
only 30
A).
8.4.3 CFMIN and RFMAX
This section explains the method of calculating the values for the capacitor on CFMIN and
the resistor on RFMAX.
8.4.3.1
Minimum frequency setting for CFMIN
(23)
(24)
(25)
(26)
Fig 28. Timing overview of the oscillator and HBC drive
GateLs
GateHs
Hb
30
μ
A-period
I
TrHbc
Cfmin
t
V
Boost
0
0
001aal038
f
oscillator
2
f
HB
=
t
ch
e
arg
t
disch
e
arg
t
oscillator
2
----------------------
V
oscillator
V
high CFMIN
V
low CFMIN
3
V
1
V
2
V
=
–
=
–
=
I
oscillator min
150
A
=