AN10881
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2011. All rights reserved.
Application note
Rev. 2 — 26 September 2011
44 of 102
NXP Semiconductors
AN10881
TEA1713 resonant power supply control IC with PFC
8. HBC
functions
8.1 HBC UVP boost
The TEA1713 begins operation when the input voltage is higher than approximately 90 %
of the nominal boost voltage to ensure proper working of the HBC.
The voltage on the SNSBOOST pin is sensed continuously. When the voltage on
SNSBOOST drops below 1.6 V, switching of the HBC is stopped when the low-side
MOSFET is on. The HBC (re)starts when the SNSBOOST voltage exceeds the start level
of 2.3 V.
8.2 HBC switch control
The internal control for the MOSFET drivers, determines when the MOSFETs are
switched on and off. It uses the input from several functions.
1. An internal divider is used to provide the alternating switching of high-side and
low-side MOSFET for every oscillator cycle.
2. The adaptive non-overlap (see
) sensing on HB determines the switch-on
moment.
3. The oscillator (see
) determines the switch-off moment.
4. Several protection and enable functions determine if the resonant converter is allowed
to switch.
8.3 HBC adaptive non-overlap
8.3.1 Inductive mode (normal operation)
The high efficiency of a resonant converter is the result of Zero-Voltage Switching (ZVS)
of the power MOSFETs, also called soft-switching. A small non-overlap time (also called
dead time) is required between the on-time of the high-side MOSFET and low-side
MOSFET to allow soft-switching. During this non-overlap time, the primary resonant
current (dis)charges the capacitance of the half-bridge between ground and boost voltage.
After the (dis)charge, the body diode of the MOSFET starts conducting and because the
voltage across the MOSFET is zero, there are no switching losses.
This mode of operation is called Inductive mode because the switching frequency is
above the resonance frequency and the resonant tank has an inductive impedance.