TEA1751LT/N1 NXP Semiconductors, TEA1751LT/N1 Datasheet - Page 13

• Manufacturer Part Number: TEA1751LT/N1
• Description: AC-DC, PFC, FLYBACK, CNTRL, 16SOIC
• Manufacturer: NXP Semiconductors

Specifications of TEA1751LT/N1

• Input Voltage: 276V
• Output Current: 1.2A
• Output Voltage: 11V
• No. Of Outputs: 2
• Power Dissipation Pd: 600mW
• Voltage Regulator Case Style: SOIC
• No. Of Pins: 16
• Operating Temperature Range: -40°C To
• Supply Voltage Range: 21V To 23V
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

NXP Semiconductors
TEA1751T_LT_2
Product data sheet
7.3.2 Valley switching (HV pin)
Refer to
on-time (determined by the FBSENSE voltage and the FBCTRL voltage), the MOSFET is
switched off and the secondary stroke starts. After the secondary stroke, the drain voltage
shows an oscillation with a frequency of approximately
the primary self-inductance of the flyback transformer and C
drain node.
As soon as the internal oscillator voltage is high again and the secondary stroke has
ended, the circuit waits for the lowest drain voltage before starting a new primary stroke.
Figure 9
oscillator signal.
Valley switching allows high frequency operation as capacitive switching losses are
reduced, see
magnetics possible.
⎛
⎝
Fig 8.
P
=
1
-- -
2
×
switching frequency
Figure
shows the drain voltage, valley signal, secondary stroke signal and the internal
C
Frequency control of flyback part
d
×
Equation
V
f
2
9. A new cycle starts when the external MOSFET is activated. After the
sw(fb)max
×
f
⎞
⎠
Rev. 02 — 23 December 2009
1. High frequency operation makes small and cost-effective
frequency
reduction
PFC off
1.5 V
TEA1751T; TEA1751LT
PFC on
discontinuous
with valley
switching
V
FBCTRL
-------------------------------------------------- -
(
2
GreenChip III SMPS control IC
×
π
d
is the capacitance on the
×
quasi resonant
1
(
L
p
×
C
© NXP B.V. 2009. All rights reserved.
d
)
)
014aaa159
where L
13 of 29
p
is
(1)