tea1713lt NXP Semiconductors, tea1713lt Datasheet - Page 20

• Manufacturer Part Number: tea1713lt
• Description: Resonant Power Supply Control Ic With Pfc
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TEA1713LT
Product data sheet
7.8.4.2 Capacitive mode
The time required for the HB transition depends on the amplitude of the resonant current
at the instant of switching. There is a complex relationship between this amplitude, the
frequency, the boost voltage and the output voltage. Ideally the IC should switch the
MOSFET on as soon as the HB transition has been completed. If it waits any longer, the
HP voltage may swing back, especially at high output loads. The advanced adaptive
non-overlap time function takes care of this timing, so that it’s not necessary to chose a
fixed dead time (which is always a compromise). This saves on external components.
Adaptive non-overlap time sensing measures the HB slope after one MOSFET has been
switched off. Normally, the HB slope starts immediately (the voltage starts rising or falling).
Once the transition at the HB node is complete, the slope ends (the voltage stops
rising/falling). This is detected by the ANO time sensor and the other MOSFET is switched
on. In this way the non-overlap time is optimized automatically, minimizing switching
losses, even if the HB transition cannot be fully completed.
operation of the adaptive non-overlap time function in Inductive mode.
The non-overlap time depends on the HB slope, but has upper and lower limits.
An integrated minimum non-overlap time, t
under any circumstances.
The maximum non-overlap time is limited to the oscillator charge time. If the HB slope
lasts longer than the oscillator charge time (=
forced to switch on. In this case the MOSFET is not soft switching. This limitation ensures
that, at very high switching frequencies, the MOSFET on-time is at least
switching period.
The description above holds for normal operation with a switching frequency above the
resonance frequency. When an error condition occurs (e.g. output short, load pulse too
high) the switching frequency can be lower than the resonance frequency. The resonant
tank then has a capacitive impedance. In Capacitive mode, the HB slope does not start
after the MOSFET has switched off. Switching on the other MOSFET is not recommended
in this situation. The absence of soft switching increases dissipation in the MOSFETs. In
Fig 10. Adaptive non-overlap time function (normal inductive operation)
GATEHS
GATELS
V
Boost
HB
0
All information provided in this document is subject to legal disclaimers.
fast HB slope
Rev. 1 — 24 June 2011
Resonant power supply control IC with PFC
no(min)
slow HB slope
1
⁄
4
, prevents cross conduction occurring
of HB switching period) the MOSFET is
Figure 10
TEA1713LT
incomplete HB slope
illustrates the
© NXP B.V. 2011. All rights reserved.
1
⁄
4
of the HB
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t