LED news and insight from our technology editor Steve Bush, who has been messing with LED lighting for more years than he would care to remember.
Single chip for LED bulbs that dim to lower CCT
Called iW3640, it is a 25W 2-channel mains-powered LED driver that needs no external microcontroller, and is intended for 75-150W-equivalent A19 and PAR bulbs, as well as 20-45W commercial dimmable external lighting ballasts.
There is a lot more iW3640 information on Electronics Weekly’s main news site.
It works by producing a PWM signal that gradually increases its duty-cycle as output current is reduced. A set of white LEDs is fed directly from the converter output (see diagrams below) while a set of amber LEDs is fed from the same output, but modulated by the PWM signal via a mosfet. In this way, the light output becomes more amber as the light is dimmed.
Tags: CCT, colour temperature, LED bulbs