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PDF ( 数据手册 , 数据表 ) TEA18361LT

零件编号 TEA18361LT
描述 GreenChip SMPS control IC
制造商 NXP Semiconductors
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TEA18361LT 数据手册, 描述, 功能
TEA18361LT
GreenChip SMPS control IC
Rev. 2 — 12 December 2013
Product data sheet
1. General description
The TEA18361LT is a controller IC for low-cost Switched Mode Power Supplies (SMPS).
It is intended for flyback topologies. The built-in green functions provide high efficiency at
all power levels.
At high power levels the flyback operates in Quasi-Resonant (QR) mode. At lower power
levels, the controller switches to Frequency Reduction (FR) or Discontinuous Conduction
Mode (DCM) and limits the peak current to approximately 25 % of the maximum peak
current. Valley switching is used in all operating modes.
At low power levels, when the flyback switching frequency drops below 25 kHz, the
flyback converter switches to burst mode. A special burst mode has been integrated
which reduces the opto current to a minimum level, ensuring high efficiency at low power
and excellent no load power performance. As the switching frequency in this mode has a
minimum value of 25 kHz while the burst frequency is below 800 Hz, the frequencies are
outside the audible range. During the non-switching phase of the burst mode, the internal
IC supply current is minimized for further efficiency optimization.
The TEA18361LT includes an accurate OverPower Protection (OPP). The OPP enables
the controller to operate in overpower situations for a limited amount of time. If the output
is shorted, the system switches to low-power mode where the output power is limited to a
lower level.
The TEA18361LT is manufactured in a high-voltage Silicon-On-Insulator (SOI) process.
The SOI process combines the advantages of a low-voltage process (accuracy,
high-speed protection, functions, and control), while maintaining the high-voltage
capabilities (high-voltage start-up, low standby power, and an integrated X-capacitor
discharge function).
The TEA18361LT enables low-cost, highly efficient and reliable supplies for power
requirements up to 75 W to be designed with a minimum number of external components.
All values mentioned in this data sheet are typical values, unless otherwise specified.







TEA18361LT pdf, 数据表
NXP Semiconductors
TEA18361LT
GreenChip SMPS control IC
7.4 Mains voltage measuring
In a typical application, the mains input voltage is measured using the HV pin.
Once per ms the mains voltage is measured by pulling down the HV pin to ground and
measuring its current. This current then reflects the input voltage.
The system determines if the mains voltage exceeds the brownin level or it is
disconnected using an analog-to-digital converter and digital control (see Figure 1).
Once the mains is above the brownin level, the system is allowed to start switching
(see Figure 6).
If the mains voltage is continuously below the brownout level for a period of at least
30 ms, a brownout is detected and the system immediately stops switching. This period is
required to avoid that the system stops switching due to the zero crossings of the mains or
during a short mains interruption.
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Fig 6. Mains voltage measuring
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When the mains voltage is measured by pulling the HV pin to ground, the digital control
calculates if there is a positive dV/dt at the mains. A positive dV/dt implies that a mains is
connected.
Once a mains is detected, the measuring of the mains input voltage is stopped for a
period of 6 ms to improve efficiency. In burst mode this waiting period is enlarged to 97 ms
to improve efficiency.
A positive dV/dt is measured when succeeding samples cross the brownin level (Ibi(HV)) or
the mains high level (IIH(HV); see Figure 7).
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Fig 7. Detecting mains connection by +dV/dt
DDD
TEA18361LT
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 12 December 2013
© NXP B.V. 2013. All rights reserved.
8 of 29







TEA18361LT equivalent, schematic
NXP Semiconductors
TEA18361LT
GreenChip SMPS control IC
7.8 Soft start-up (ISENSE pin)
To prevent audible noise during start-up or a restart condition, a soft start feature is
implemented. Before the converter starts, the soft start capacitor CSS on the ISENSE pin
is charged. When the converter starts switching, the primary peak current slowly
increases as the soft start capacitor discharges through the soft start resistor RSS
(see Figure 3).
The soft start time constant is set by the external soft start capacitor and the parallel
resistor values.
7.9 Driver (DRIVER pin)
The driver circuit to the gate of the power MOSFET has a current sourcing capability of
300 mA and a current sink capability of 750 mA. These capabilities allow a fast turn-on
and turn-off of the power MOSFET for efficient operation.
The maximum driver output is limited to 10.5 V. The DRIVER output pin can be connected
to the gate of a MOSFET directly or via a resistor.
7.10 Power-down mode
To achieve extremely low no-load standby power, the IC can be forced to power-down
mode using an external signal on the PROTECT pin (see Figure 14).
When the voltage on the PROTECT pin is pulled below Vth(pd)PROTECT, the system enters
the power-down mode. The voltage on the CTRL pin is lowered to 0 V. The IC
automatically runs in burst mode with the voltage on pin VCC regulated at the Vrestart
level. The primary and secondary opto current is saved. The current out of the PROTECT
pin is reduced from 74 A to 47 A to save current consumption (See Figure 15).
To avoid that the latched protection is accidentally triggered when the system enters or
comes out of the power-down mode, the latched protection is blocked when the voltage
on the PROTECT pin is lower than Vth(pd)PROTECT.
TEA18361LT
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 2 — 12 December 2013
© NXP B.V. 2013. All rights reserved.
16 of 29










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