TEA1713T_11 NXP [NXP Semiconductors], TEA1713T_11 Datasheet - Page 28

• Manufacturer Part Number: TEA1713T_11
• Description: Resonant power supply control IC with PFC
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
TEA1713T
Product data sheet
7.8.10.1 Boost voltage compensation
7.8.10 HBC overcurrent regulation and protection, OCR and OCP
7.8.9 HBC high-frequency protection, HFP-HBC (pin RFMAX)
Normally the converter will not operate continuously at maximum frequency because it will
sweep down to much lower values. Certain error conditions, such as a disconnected
transformer, could cause the converter to operate continuously at maximum frequency. If
zero-voltage switching conditions are no longer present, the MOSFETs can overheat. The
TEA1713 features High-Frequency Protection (HFP) for the HBC controller to protect it
from being damaged in such circumstances.
HFP senses the voltage at pin RFMAX. This voltage indicates the current frequency.
When the frequency is higher than 75 % of the soft start frequency range, the protection
timer is started. The 75 % level corresponds to an RFMAX voltage of V
(typ. 1.83 V).
(pin SNSCURHBC)
The HBC controller is protected against overcurrent in two ways:
A boost voltage compensation function is included to reduce the variation in the output
current protection level.
The primary current, also known as the resonant current, is sensed via pin SNSCURHBC.
It senses the momentary voltage across an external current sense resistor R
use of the momentary current signal allows for fast overcurrent protection and simplifies
the stabilizing of overcurrent regulation. The OCR and OCP comparators compare
V
For the same output power, the primary current is higher when the boost voltage is low. A
boost compensation is included to reduce the dependency of the protected output current
level on the boost voltage. The boost compensation sources and sinks a current from the
SNSCURHBC pin. This current creates a voltage drop across the series resistor R
The amplitude of the current depends linearly on the boost voltage. At nominal boost
voltage the current is zero and the voltage V
also present at the SNSCURHBC pin. At the UVP-boost start level V
current is at a maximum. The direction of the current, sink or source, depends on the
active gate signal. The voltage drop created across R
pin, resulting in a higher effective current protection level. The amount of compensation is
set by the value of R
artificial current signal. The sinking compensation current only flows when V
positive because of the circuit implementation.
SNSCURHBC
•
•
Overcurrent regulation (OCR-HBC) which increases the frequency slowly; the
protection timer is also started.
Overcurrent protection (OCP-HBC) which steps to maximum frequency.
with the maximum positive and negative values.
All information provided in this document is subject to legal disclaimers.
curcmp
Rev. 2 — 9 February 2011
.
Figure 17
shows how the boost compensation works for an
Resonant power supply control IC with PFC
Cur(HBC)
across the current sense resistor is
curcmp
reduces the amplitude at the
TEA1713T
uvp(SNSBOOST)
hfp(RFMAX)
© NXP B.V. 2011. All rights reserved.
SNSCURHBC
cur(HBC)
, the
curcmp
28 of 47
. The
is
.