NXP Semiconductors
TEA19362T
GreenChip SMPS primary side control IC with fixed frequency operation
TEA19362T All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2016. All rights reserved.
Product data sheet Rev. 1 — 9 August 2016
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8 Functional description
8.1 Supply management
The chip is supplied by high-voltage mains via the HV pin during start-up and protection
mode. When the system starts switching, the auxiliary windings take over the supply.
The IC has two supply pins, the VCCH and VCCL pins. The lower pin (VCCL) supplies
the IC directly. The higher supply pin (VCCH) is connected to the VCCL pin via an
internal voltage regulator. When used in an application, which supports multiple output
voltages, a pair of auxiliary transformer windings can be used to supply the IC efficiently
at all output levels. To supply the IC at higher output voltages, the winding with fewer
turns can be connected to the VCCL pin. At the lower output voltages, the winding
with more turns can supply the IC via the VCCH pin. The voltage capability of these
pins is chosen such that applications with an output voltage range from 3 V to 20 V are
supported optimally. When the voltage on the VCCL pin drops to below V
integd(VCCL)
, the
regulator between the VCCH and VCCL pins turns on.
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.
8.2 Start-up and UnderVoltage LockOut (UVLO)
Initially, the capacitor on the VCCL pin is charged from the high-voltage mains using the
HV pin. The voltage on the VCCH pin follows (via an internal diode) the voltage on VCCL
pin. In this way, the capacitor on the VCCH pin is charged. As long as V
CC
(the voltage
on pin VCCL) is below V
startup
, the IC current consumption is minimized. When V
CC
reaches the V
startup
level, the control logic activates the internal circuitry. The IC waits
for the PROTECT pin to reach V
det(PROTECT)
+ V
det(hys)PROTECT
and the mains voltage
to increase to above the brownin level. Meanwhile, the internal power-control signal
(which depends on the current at the CTRL pin) also increases to its maximum value.
When all these conditions are met, the system starts switching with soft start. In a typical
application, the auxiliary winding of the transformer takes over the supply.
During the start-up period, the VCC pin is continuously regulated to the V
startup
level
using the HV charge current. The pin is regulated until the output voltage is at its
regulation level, which is detected via the CTRL pin. In this way, the VCC capacitor
value can be limited. Due to the limited current capability from the HV pin mains voltage
dependent, the voltage on pin VCC can still drop slightly during the start-up period.
