SSL1750_1

© NXP B.V. 2008. All rights reserved.

Product data sheet

Rev. 01 — 15 September 2008

15 of 29

NXP Semiconductors

SSL1750

SMPS control IC for LED drivers

7.3.3 Current mode control (pin FBSENSE)

Current mode control is used for the flyback converter for its good line regulation.

The primary current is sensed by pin FBSENSE across an external resistor and compared

with an internal control voltage.The internal control voltage is proportional to the voltage

on pin FBCTRL.

(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.

Fig 10. Signals for valley switching

drain

secondary

stroke

014aaa027

secondary

ringing

primary

stroke

valley

(2)

(1)

secondary

stroke

oscillator