GreenChip SMPS control IC
Fig 3. TEA1732LTS 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
As long as VCC is below Vstartup, the IC current consumption is low (10 A typical). When
VCC reaches Vstartup, the IC first waits for the mains voltage to exceed the brownin level,
and the PROTECT pin to reach the Vdet(PROTECT)(L) voltage. When both conditions are
met, the IC starts switching. An internal soft-start time of 3.5 ms allows the ISENSE peak
voltage to increase gradually to prevent audible noise. 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.
The brownout and maximum duty cycle protections cause a save restart. The OPP,
UVLO, OVP, external OTP and internal OTP protections latch 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
average 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 TEA1732LTS immediately enters Power-down
mode. The VCC pin is clamped to a voltage just above the latch protection reset voltage
(Vrst(latch) + 0.9 V).
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 18 March 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
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