AN10907
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Application note
Rev. 1 — 28 December 2010
58 of 82
NXP Semiconductors
AN10907
TEA1613T resonant power supply control IC
9.9.4 Audible noise during mode transition
Because of the above mentioned interactions, a stable situation can occur during the
following operating modes, alternating in time:
•
Resonant burst with short burst time without PFC burst (time too short to start)
•
Resonant burst with long burst time and PFC burst
•
Normal operation for resonant and PFC bursts
Transitions between modes and variations within a certain mode have a corresponding
effect on audible noise.
9.10 Design guidelines for burst mode operation
Design for a stable PFC (nominal) output voltage during burst mode. When the PFC is
operating in simultaneous burst mode, the issues mentioned in
are important.
Best efficiency is achieved when the number of cycles for each burst is kept to a minimum
(only a few cycles).
Best efficiency is achieved by resistively tuning the comparator circuit to preset the
SNSFB burst level and hysteresis.
System and component tolerances play a significant role in performance variations during
production.
The regulation feedback loop can be optimized for normal mode and any additional
filtering can be done in the comparator circuit see
. However, this should be
used moderately so that control of the situation can be maintained during burst mode
operation.
9.11 Enable/disable burst mode
In microcontroller operated applications such as TV, a clear separation is made between
normal operation and standby operation. To avoid the resonant converter going into burst
during short periods of low load during normal operation, an enable/disable function can
be added. This can be implemented by an extra enable/disable switch function in the
comparator circuit.
9.12 Hold HBC and PFC
By switching the SNSBURST input below 3.5 V, the switching of HBC and PFC (by
SNSOUT/PFCON) can be stopped immediately. Releasing the pin voltage resumes the
operation (without soft-start) on the regulation point of that moment. For certain external
protection procedures, this hold-function can be useful.
9.13 Unused burst mode
By connecting SNSBURST to a fixed voltage higher than 3.5 V (but below the limiting
value of +12 V), the burst mode function is not activated. For example, SNSBURST can
be connected to SUPREG.
