AN10952_15 Datasheet, PDF (13/40 Pages) NXP Semiconductors – SSL2103 flexible, mains-dimmable LED driver

NXP Semiconductors
AN10952
SSL2103 flexible, mains-dimmable LED driver
6. Step-by-step design procedure
Remark: All components referred to in the text can be located on Figure 9 “Typical flyback
application using the SSL2103” and switches can be found on Figure 2 “Basic flyback
converter” and Figure 3 “Flyback equivalent circuits and waveforms (DCM mode)”.
This sections provides a step-by-step guide to designing a basic flyback converter
application incorporating the SSL2103. It should be noted that the derivation of the
formulas applied is beyond the scope of this application note. Where values used in
formulas are application specific, reasonable estimates have been made. Recommended
component values were achieved through extensive testing with a range of commercially
available dimmers.
6.1 Basic configuration
A circuit for a typical flyback application driving a single LED chain is shown in Figure 9.
The mains voltage is rectified, buffered and filtered in the input section and connected to
the primary winding of the transformer. In the output section, the transferred energy is
stored in a capacitor (C5) and filtered (L3) before driving the LED chain. A clamp is added
across the primary winding of the transformer to prevent a high voltage overshoot on the
DRAIN pin of the SSL2103, at the moment the external power MOS transistor is switched
off. A dimming detection circuit divides and filters the mains rectified voltage to provide
input for the generation of the dimming curve.
The following functional blocks can be identified in the SSL2103 application and they will
be discussed separately (refer to Figure 9):
1. LED output current circuit
2. Oscillator
3. External power switch
4. Snubber
5. V_CC generation
6. A/B bleeder settings
7. Dimming detection
8. Mains buffer
9. Input circuit
AN10952
Application note
All information provided in this document is subject to legal disclaimers.
Rev. 1 — 24 December 2010
© NXP B.V. 2010. All rights reserved.
13 of 40