AN10881
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© NXP B.V. 2011. All rights reserved.
Application note
Rev. 2 — 26 September 2011
74 of 102
NXP Semiconductors
AN10881
TEA1713 resonant power supply control IC with PFC
10.3.1 OverVoltage Protection (OVP) output
The TEA1713 has an overvoltage protection intended for monitoring the HBC output
voltage. It is one of the functions that is combined on the SNSOUT pin.
10.3.1.1
Auxiliary winding
When dealing with a mains insulated converter, the HBC output voltage can be measured
via the auxiliary winding of the resonant transformer. A special transformer construction is
required to accurately measure the secondary voltage of the primary circuit auxiliary
winding.
It is important that this winding has a good coupling with the secondary winding(s) and a
minimum coupling with the primary winding. In this way, a good representation of the
output voltage situation is obtained (see
).
Triple insulated wire can be used to meet the mains insulation requirements.
10.3.1.2
Principle of operation
The voltage is sensed at the SNSOUT pin via an external rectifier and resistive divider.
Overvoltage is detected when the SNSOUT voltage exceeds 3.5 V. After detecting OVP
the TEA1713 enters the latched protection shutdown state.
10.3.1.3
Connecting external measurement circuits
When latched protection is needed for other detection circuits, it can be added to
SNSOUT with a series diode.
10.3.2 UnderVoltage Protection (UVP) output
The TEA1713 has an undervoltage protection intended for monitoring the HBC output
voltage. It is one of the functions that is combined on the SNSOUT pin.
10.3.2.1
Auxiliary winding
When dealing with a mains insulated converter, the HBC output voltage can be measured
via the auxiliary winding of the resonant transformer. A special transformer construction is
required to accurately measure the secondary voltage of the primary circuit auxiliary
winding.
It is important that this winding has a good coupling with the secondary winding(s) and a
minimum coupling with the primary winding to obtain a good representation of the output
voltage situation (see
).
Triple insulated wire can be used to meet the mains insulation requirements.
10.3.2.2
Principle of operation
The voltage is sensed at the SNSOUT pin via an external rectifier and resistive divider.
Undervoltage is detected when the SNSOUT voltage drops below 2.35 V. When detecting
UVP the TEA1713 starts the protection timer by charging it with 100
A.
When the undervoltage state remains until the timer reaches the protection level, the
controller stops and then the restart timer restarts it.
