UM10526
TEA1792TS GreenChip synchronous rectifier controller
add-on board
Rev. 1 — 26 June 2012
User manual
Document information
Info
Keywords
Abstract
Content
TEA1792TS, Synchronous Rectifier (SR) driver, high efficiency, TSOP6,
flyback converter, TEA1792DB1074 add-on board
This user manual describes how the TEA1792TS add-on board can be
used in a flyback converter. The add-on board contains a TEA1792TS SR
controller in TSOP-6 package. Besides the add-on board also contains a
power MOSFET, as well as a charge pump circuit to generate the supply
voltage for the SR controller. The add-on board replaces the rectifier diode
at the secondary side of the flyback converter. It is intended for high-side
applications, but with minor modifications it can also be used for low-side
applications.
NXP Semiconductors
UM10526
TEA1792TS GreenChip synchronous rectifier controller add-on board
Revision history
Rev
v.1
Date
20120626
Description
first issue
Contact information
For more information, please visit:
http://www.nxp.com
For sales office addresses, please send an email to:
salesaddresses@nxp.com
UM10526
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1 — 26 June 2012
2 of 22
NXP Semiconductors
UM10526
TEA1792TS GreenChip synchronous rectifier controller add-on board
1. Introduction
This document describes the TEA1792TS add-on board. A functional description and a
set of measurements illustrate the performance of the TEA1792TS add-on board. The
add-on board also contains a charge pump circuit, capable of delivering the supply
voltage for the SR controller. The charge pump circuit eliminates the auxiliary transformer
winding in the flyback convertor.
A flyback converter board in which the secondary part (diode) can be replaced by the
add-on board is required to use the add-on board correctly.
2. Safety Warning
WARNING
Lethal voltage and fire ignition hazard
The non-insulated high voltages that are present when operating this product, constitute a
risk of electric shock, personal injury, death and/or ignition of fire.
This product is intended for evaluation purposes only. It shall be operated in a designated test
area by personnel qualified according to local requirements and labor laws to work with
non-insulated mains voltages and high-voltage circuits. This product shall never be operated
unattended.
The complete add-on board application is AC mains voltage powered. Avoid touching the
board when power is applied. An isolated housing is obligatory when used in uncontrolled,
non-laboratory environments. Always provide galvanic isolation of the mains phase using
a variable transformer. The following symbols identify isolated and non-isolated devices.
019aab173
019aab174
a. Isolated.
Fig 1.
Isolated and non-isolated symbols
b. Non-isolated
UM10526
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1 — 26 June 2012
3 of 22
NXP Semiconductors
UM10526
TEA1792TS GreenChip synchronous rectifier controller add-on board
3. TEA1792TS SR controller
The TEA1792TS is a member of the new generation of Synchronous Rectifier (SR)
controller ICs for switched mode power supplies. Its high level of integration allows the
design of a cost-effective power supply with a very low number of external components.
The IC provides synchronous rectification on the secondary side for discontinuous
conduction mode and quasi-resonant mode flyback converters.
It is a successor to the TEA1791T synchronous rectifier controller IC. The TEA1792TS
provides improved performance, a smaller package option (TSOP6) and two different
selectable regulation levels.
An efficient control algorithm built into the IC determines when a MOSFET is switched on
or off. After a negative voltage lower than V
act(drv)
(220 mV typical) is sensed on the
SRSENSE pin, the driver output voltage is driven HIGH. Then the external MOSFET is
switched on. When V
SRSENSE
rises to V
reg(drv)
(42 mV/30 mV), the driver output voltage
is regulated to maintain the V
reg(drv)
on the SRSENSE pin. When the SRSENSE voltage is
above the V
deact(drv)
level (12 mV typical), the driver output is pulled to ground.
After switch-on of the SR MOSFET, the input signal on the SRSENSE pin is blanked
during the t
act(sr)(min)
(1.8
s
typical). This action eliminates false switch-off due to high
frequency ringing at the start of the secondary stroke.
When the secondary current is reduced until the SRSENSE voltage is V
ref
, the internal
control loop maintains the V
reg(drv)
level across the MOSFET. Maintaining V
reg(drv)
in this
instance is achieved when the V
DRIVER
voltage is decreased. This reduction enables the
external power switch to be switched off quickly when the current through the switch
reaches zero. The zero current is detected by sensing a V
deact(drv)
(12 mV typical) level
on the SRSENSE pin.
The TEA1792TS stops performing synchronous rectification for short pulses which
removes the need for a separate Standby mode to maintain high efficiency at low-loads.
SRSENSE
1
6
DRIVER
GND
2
TEA1792TS
5 n.c.
V
CC
3
aaa-001385
4
SELREG
Fig 2.
Pin configuration TEA1792TS (TSOP6)
UM10526
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1 — 26 June 2012
4 of 22
NXP Semiconductors
UM10526
TEA1792TS GreenChip synchronous rectifier controller add-on board
4. General application of the TEA1792TS
General application diagrams of high-side and low-side rectification are given in
Figure 3
and
Figure 4.
See
Figure 2
for the relevant pin numbers.
TR
auxillary
winding
Qsec
V
o
V
IN
primary
winding
secondary
winding
Qprim
C
VCC
GND
RDRIVER
RSRSENSE
SELREG DRIVER
Cout
PRIMARY
SIDE
CONTROLLER
V
CC
TEA1792
SRSENSE
aaa-003677
Fig 3.
Application diagram for high-side rectification
V
IN
primary
winding
TR
secondary
winding
V
o
SRSENSE
V
CC
PRIMARY
SIDE
CONTROLLER
Qprim Qsec
RSRSENSE
RDRIVER
TEA1792
DRIVER
SELREG
GND
Cout
aaa-003678
Fig 4.
Application diagram for low-side rectification
In high-side rectification (Figure
3),
the supply voltage for the TEA1792TS is normally
derived from an auxiliary winding on the transformer secondary side.
In low-side rectification (Figure
4),
the output voltage V
OUT
is used in most cases as the
TEA1792TS supply.
High-side rectification is the preferred application for the best EMI performance.
4.1 Add-on board set-up
The add-on board is designed for incorporation into existing flyback power supplies by
replacing the secondary rectifier diode. Although the add-on board was designed for
high-side rectifier applications, it is also possible to replace the rectifier diode in low-side
applications.
The add-on board consists of:
•
the TEA1792TS in TSOP-6 package
•
a MOSFET with a typical R
ON
of 7 m
•
a charge pump circuit capable of delivering the SR controller supply voltage
UM10526
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
User manual
Rev. 1 — 26 June 2012
5 of 22
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