12W Dimmer with Soft Start for 12V LEDs
The circuit presented here is a LED dimmer with a soft-start function. The board can drive a LED up to 12W and the circuit can manage a load up to 1A continuous with 12Vsupply. The circuit is built using SG3525 PWM IC and the IRFR120 MOSFET, SG3525 generates the PWM, and IRFR120 MOSFET drives the 12W max load. BC847 is used to invert the PWM signal from SG3525 and create a soft-start circuit. SG3525 has a soft-start function and the soft-start timing can be slowed down by increasing the capacitor C2 value to 22uF/16V. Trimmer pot PR1 provided to adjust the PWM frequency from 210 Hz to 6.5Khz. Keeping PWM frequency lower is advisable for LED load.
12W Dimmer with Soft Start for 12V LEDs – [Link]