tea1753lt NXP Semiconductors, tea1753lt Datasheet - Page 15

• Manufacturer Part Number: tea1753lt
• Description: Tea1753lt Greenchip Iii Smps Control Ic
• Manufacturer: NXP Semiconductors

NXP Semiconductors
TEA1753LT
Objective data sheet
7.3.3 Current mode control (FBSENSE pin)
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 10
oscillator signal.
Valley switching allows high frequency operation as capacitive switching losses are
reduced, see
magnetics possible.
Current mode control is used for the flyback converter for its good line regulation.
The primary current is sensed by the FBSENSE pin across an external resistor and
compared with an internal control voltage.The internal control voltage is proportional to
the FBCTRL pin voltage, see
The FBSENSE pins outputs a current of 3 A. This current runs through the resistors from
the FBSENSE pin to the sense resistor and creates an offset voltage. The minimum peak
current of the flyback is adjusted using this offset voltage. Adjusting the minimum peak
current level, will change the frequency reduction slope. (see
P
Fig 10. Signals for valley switching
=
1
-- -
2
(1) Start of new cycle at lowest drain voltage.
(2) Start of new cycle in a classical Pulse Width Modulation (PWM) system without valley detection.

C
shows the drain voltage, valley signal, secondary stroke signal and the internal
d

V
Equation
secondary
2
oscillator
All information provided in this document is subject to legal disclaimers.

stroke
valley
drain
f
4. High frequency operation makes small and cost-effective
Rev. 01 — 4 March 2011
primary
stroke
Figure
secondary
stroke
11.
secondary
ringing
GreenChip III SMPS control IC
Figure
(2)
TEA1753LT
014aaa027
8)
© NXP B.V. 2011. All rights reserved.
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