AN10907
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© NXP B.V. 2010. All rights reserved.
Application note
Rev. 1 — 28 December 2010
16 of 82
NXP Semiconductors
AN10907
TEA1613T resonant power supply control IC
In case of a combined function of SUPIC and SNSOUT/PFCON by an auxiliary winding on
the HBC transformer, some issues need to be addressed to obtain a good representation
of the output voltage for SNSOUT/PFCON measurement.
The advantage of a good coupling/representation of the auxiliary winding with the output
windings is that a stable auxiliary voltage is also obtained for SUPIC. A low SUPIC voltage
value can be designed more easily for lowest power consumption.
6.3.3.2
Auxiliary supply voltage variations by output current
At high (peak) current loads, the voltage drop across the series components of the HBC
output stage (resistance and diodes) is compensated by regulation. This results in a
higher voltage on the windings at higher output currents due to the higher currents
causing a larger voltage drop across the series components. An auxiliary winding supply
shows this variation caused by the HBC output.
6.3.3.3
Voltage variations by auxiliary winding position: primary side component
Due to a less optimal position of the auxiliary winding, the voltage for SNSOUT/PFCON
and/or SUPIC can contain a certain amount of undesired primary voltage component. This
can seriously endanger the feasibility of the SNSOUT/PFCON sensing function.
To avoid a primary voltage component on the auxiliary voltage, the coupling of the
auxiliary winding with the primary winding should be as small as possible. To obtain this,
the auxiliary winding should be placed on the secondary winding(s) and as physically
remote as possible from the primary winding. See the differences in the results provided
by the comparison on a secondary side position in
Fig 7.
Position the auxiliary winding for good output coupling
001aal020
secondary side
primary side
V
aux
V
aux
V
aux.new
V
aux.new
V
O
V
O
V
O
Bad coupling V
aux
to V
O
at high
output current
Good coupling
V
aux.new
to V
O
at
high output current
