SSL21081AT Datasheet, PDF (6/22 Pages) NXP Semiconductors – Compact non-dimmable LED driver IC

NXP Semiconductors
SSL21082AT
Mains dimmable LED driver IC
8. Functional description
8.1 Introduction
The SSL21082AT is a controller IC solution for small form factor mains phase-cut
dimmable LED lamps in isolated and non-isolated applications.
8.2 Converter operation
The converter in the SSL21082AT is a Boundary Conduction Mode (BCM), peak current
controlled system. See Figure 3 for the basic application diagram. See Figure 4 for
relevant the waveforms.
This converter type operates at the boundary between continuous and discontinuous
mode. Energy is stored in inductor L each period that the switch is on. The inductor
current I_L is zero when the MOSFET is switched on. The amplitude of the current build-up
in L is proportional to the voltage drop over the inductor and the time that the MOSFET
switch is on. When the MOSFET is switched off, the energy in the inductor is released
towards the output. The current then falls at a rate proportional to the value of V_O. The
LED current I_LED depends on the peak current through the inductor (SSL21082AT
controlled) and on the dimmer angle while it is optimized for a high-power factor. A new
cycle is started once the inductor current I_L is zero. This quasi-resonant operation results
in higher efficiency.
5LQUXVK

9_L
/

72102'

+9 _
9&& _
'9'7

,&
 
*1'
17&
'5$,1


6285&(
17& 5VHQVH
Fig 3. SSL21082AT basic application diagram

/('V 9_R

DDD
SSL21082AT
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 6 — 3 October 2013
© NXP B.V. 2013. All rights reserved.
6 of 21