NXP Semiconductors AN10907, Примечание к применению

Страница: 15 / 82

AN10907 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2010. All rights reserved.
Application note Rev. 1 — 28 December 2010 15 of 82
NXP Semiconductors
AN10907
TEA1613T resonant power supply control IC
6.3.3 Auxiliary winding on the HBC transformer
To obtain a supply voltage for SUPIC during operation, an auxiliary winding on the HBC
transformer can be used. As SUPIC has a wide operational voltage range (15 V to 38 V),
this is not a critical parameter.
Also note:
•
For low power consumption, the voltage on SUPIC should be low.
•
To use the voltage from the auxiliary winding for both the IC supply and the HBC
output voltage measurement (by SNSOUT/PFCON). The auxiliary supply must be
made accurately to represent the output voltage. To ensure good coupling, this
winding needs to be placed on the secondary (output) side.
•
When mains insulation is included in the HBC transformer, it can impact the
construction of the auxiliary winding. Triple insulated wire is needed when the
auxiliary winding is placed on the mains-insulated area of the transformer
construction.
6.3.3.1 SUPIC and SNSOUT/PFCON by auxiliary winding
The SNSOUT/PFCON input provides a combination of 3 functions:
•
Overvoltage protection: SNSOUT/PFCON > 3.5 V, latched
•
Undervoltage protection: SNSOUT/PFCON < 2.35 V, protection timer
•
During burst mode an internal switch makes this voltage level low during the time that
the HBC is not switching. This signal can be used to make a PFC burst
synchronously.
Remark: A more detailed discussion of the SNSOUT/PFCON functions can be found in
Section 9.1 “Burst mode implementation” , Section 10.3.1 “OverVoltage Protection (OVP)
output” and Section 10.3.2 “UnderVoltage Protection (UVP) output” .
Often, a circuit is used which combines SUPIC and the output voltage monitoring by
SNSOUT/PFCON, with one auxiliary winding on the HBC transformer. But an
independent construction for SUPIC and SNSOUT is also possible; for example when
SUPIC is supplied by a separate standby supply and an auxiliary winding is only used for
output voltage sensing. It is also possible not to use SNSOUT for output sensing.
SNSOUT can be used as a general purpose protection input. For more details on the
possibilities, refer to
Section 10.3.3 “OVP and UVP combinations” .
Fig 6. Auxiliary winding on primary side (left) and secondary side (right)
001aal019