TEA1731TS
GreenChip SMPS control IC
Rev. 1 — 15 February 2012
Objective data sheet
1. General description
The TEA1731TS is a low cost Switched Mode Power Supply (SMPS) controller IC
intended for flyback topologies. The TEA1731TS operates in peak current and frequency
control mode. Frequency jitter has been implemented to reduce ElectroMagnetic
Interference (EMI). Slope compensation is integrated for Continuous Conduction Mode
(CCM) operation.
The TEA1731TS IC features OverPower Protection (OPP). The controller accepts an
overpower situation for a limited amount of time.
One pin is reserved for protection purposes. OverTemperature Protection (OTP) can be
implemented with a minimal number of external components.
At low-power levels, the primary peak current is set to 25 % of the maximum peak current.
The switching frequency is reduced to limit the switching losses. The combination of fixed
frequency operation at high output power and frequency reduction at low output power
provides high efficiency over the total load range.
The TEA1731TS makes the design of low cost, highly efficient and reliable supplies for
power requirements up to 75 W easier by requiring a minimum number of external
components.
2. Features and benefits
SMPS controller IC enabling low-cost applications
Large input voltage range (12 V to 30 V)
Integrated OverVoltage Protection (OVP) on VCC
Very low supply current during start-up and restart (10
A
typical)
Low supply current during normal operation (0.58 mA typical without load)
Internal overpower time-out
Overpower or high/low line compensation (NXP patent: 81421271EP01)
Fixed switching frequency with frequency jitter to reduce EMI
Frequency reduction at medium power operation to maintain high efficiency
Frequency reduction with fixed minimum peak current to maintain high efficiency at
low output power levels
Frequency increase at peak power operation
Slope compensation for CCM operation
Adjustable soft start
Low and adjustable OverCurrent Protection (OCP) trip level
NXP Semiconductors
TEA1731TS
GreenChip SMPS control IC
Protection input (for external OTP and external OVP)
IC overtemperature protection
3. Applications
All applications that require an efficient and cost-effective power supply solution up to
75 W.
4. Ordering information
Table 1.
Ordering information
Package
Name
TEA1731TS
TSOP6
Description
plastic surface-mounted package; 6 leads
Version
SOT457
Type number
5. Block diagram
VCCstart
21 V
VCC
1
2.5 mA
5.4 V
restart
S
Q
RESTART
CONTROL
Vcc sink
power-down
TEMPERATURE
PROTECTION
OTP
12 V
VCCstop
R
4.5 V
Vcc sink
GND
2
latch
latch reset
set
5.4 V
OSCILLATOR
MODULATION
7 kΩ
30 V
driver
δ
max
COUNT OVP
TO 4
frequency reduction
V
ctrl(Ipeak)
overload
60 msec
delay
V
ctrl(Ipeak)
400 mV
ANALOG
CONTROL
SLOPE
COMPENSATION
4
CTRL
δ
max
prot
6
DRV
Q
R
S
set
stop
δ
max
restart
driver
BLANK
LEB
OCP
stop
latch
Q
R
OVERPOWER
COMPENSATION
V
ctrl(Ipeak)
restart
S
Q
R
soft start
COUNT
TO 8
δ
max
DRIVER
δ
max
prot
overload
VCCstart
power-down
protlow
prothigh
0.80 V
32
μA
3
PROTECT
protlow
55
μA
0.50 V
107
μA
soft start
latch
S
latch reset
ISENSE
5
OTP
prothigh
protlow
OVP
DIGITAL CONTROL
aaa-001693
Fig 1.
Block diagram
TEA1731TS
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Objective data sheet
Rev. 1 — 15 February 2012
2 of 18
NXP Semiconductors
TEA1731TS
GreenChip SMPS control IC
6. Pinning information
6.1 Pinning
VCC 1
6 DRIVER
GND 2
TEA1731TS
5 ISENSE
PROTECT 3
aaa-001694
4 CTRL
Fig 2.
Pin configuration
6.2 Pin description
Table 2.
Symbol
VCC
GND
PROTECT
CTRL
ISENSE
DRIVER
Pin description
Pin
1
2
3
4
5
6
Description
supply voltage
ground
general-purpose protection input
control input
current sense input
gate driver output
TEA1731TS
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Objective data sheet
Rev. 1 — 15 February 2012
3 of 18
NXP Semiconductors
TEA1731TS
GreenChip SMPS control IC
7. Functional description
7.1 General control
The TEA1731TS contains a controller for a flyback circuit. A typical configuration is shown
in
Figure 3.
C1
D1
S1
R4
D3
C5
R5
T1
Z1
C4
VCC
GND
R1
1
6
DRIVER
ISENSE
CTRL
O1
R3
2
TEA1731TS
5
3
4
PROTECT
O1
R6
C3
R2
C2
D2
R7
aaa-001695
Fig 3.
Typical configuration
7.2 Start-up and UnderVoltage LockOut (UVLO)
Initially, the capacitor on the VCC pin, C3, is charged from the high-voltage mains via
resistor R1.
As long as VCC is below V
startup
, the IC current consumption is low (10
A
typical). When
VCC reaches V
startup
, the IC first waits for the PROTECT pin to reach the V
det(PROTECT)(L)
voltage. When V
det(PROTECT)(L)
is reached, the IC charges the ISENSE pin to the V
start(soft)
level and then starts switching. In a typical application, the auxiliary winding of the
transformer takes over the supply voltage.
If a protection is triggered, the controller stops switching. Depending on the protection
triggered, it either causes a restart or latches the converter to an off-state.
A restart protection disables the switching of the IC. The supply voltage of the IC drops to
the UVLO level. When the UVLO level is reached, the IC switches to Power-down mode,
where it consumes a low supply current (10
A
typical). The VCC capacitor is recharged
via R1 until the VCC start-up level is reached. A delayed restart is performed to lower the
input power during a fault condition. Depending on the cause of the restart protection, the
restart sequence that discharges and recharges the VCC capacitor is performed once or
repeated three times, before switching recommences (See
Figure 4).
When a latched protection is triggered, the TEA1731TS immediately enters Power-down
mode. The VCC pin is clamped to a voltage just above the latch protection reset voltage
(V
rst(latch)
+ 0.9 V).
TEA1731TS
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Objective data sheet
Rev. 1 — 15 February 2012
4 of 18
NXP Semiconductors
TEA1731TS
GreenChip SMPS control IC
V
startup
V
th(UVLO)
V
CC
soft start
ISENSE
soft start
V
det(H)(PROTECT)
PROTECT
V
det(L)(PROTECT)
maximum load
Output load
Output voltage
charging VCC
capacitor
starting
converter
normal
restart
operation
delay
overpower
time-out
restart
aaa-001697
Fig 4.
Start-up sequence, normal operation and restart sequence
When the voltage on pin VCC drops below the V
th(UVLO)
level during normal operation, the
controller stops switching. The TEA1731TS waits for the rectified mains to charge the
VCC pin using resistor R1.
7.3 Supply management
All internal reference voltages are derived from a temperature compensated on-chip band
gap circuit. Internal reference currents are derived from a trimmed and temperature
compensated current reference circuit.
7.4 Overvoltage protection (pin VCC)
An OverVoltage Protection (OVP) circuit is connected to the VCC pin. When the V
CC
exceeds V
th(OVP)
(30 V typical) for four consecutive switching cycles, the IC triggers the
latched protection. When V
CC
drops below V
th(OVP)
before count = 4 is reached, the
counter is reset to zero.
If a lower over voltage protection level is needed, a Zener diode can be connected
between pins VCC and PROTECT.
7.5 Protection input (pin PROTECT)
Pin PROTECT is a general-purpose input pin, which can be used to switch off the
converter (latched protection). The converter is stopped when the voltage on this pin is
pulled above V
det(H)(PROTECT)
(0.8 V typical) or below V
det(L)(PROTECT)
(0.5 V typical) for
four consecutive converter strokes. A current of 32
A
(typical) flows out of the chip when
the pin voltage is V
det(L)(PROTECT)
. A current of 107
A
(typical.) flows into the chip when
the pin voltage is V
det(H)(PROTECT)
.
The PROTECT input can be used for creating an (additional) overvoltage detection and
an external OverTemperature Protection (OTP) function.
TEA1731TS
All information provided in this document is subject to legal disclaimers.
© NXP B.V. 2012. All rights reserved.
Objective data sheet
Rev. 1 — 15 February 2012
5 of 18
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