Power Integrations has a reference design for an 85%-efficient, 15W PAR38 downlight driver that it claims will deliver flicker-free dimming without the use of electrolytic bulk capacitors.

Based around the firm’s LNK405EG LED driver IC, it is designed to provide flicker-free performance across a broad range of triac dimmers.

Typical TRIAC dimmers were designed for incandescent lights that use an order of magnitude more power than LED lights of equivalent lumen output.

According to the supplier, the low current requirement of LED lights, especially when dimmed, can cause triacs to switch off unexpectedly or oscillate, creating an annoying flickering effect.

This can be addressed by storing energy in an electrolytic bulk capacitor, with bulb lifetime implications, or by allowing a continuous flow of current into the bulb, wasting energy and thereby defeating the main benefit of LED lighting.

The DER-281 reference design provides an alternative approach without the need for electrolytic bulk capacitors.