Single Power Supply with Soft Start

This  Single power supply with soft start circuit which presented here has a simple concept, small power, smooth voltage. This power supply voltage is actually used for control kit K8003 © VELLEMAN, which allows to smooth ignition the exterior halogen spotlights (500 Watt) or interior spotlights (bathroom lighting  for example), blackout is instantaneous. You must mount this circuit in the housing fully insulated and waterproof.

The circuit is based on the LM317, it is possible to varying the voltage between 1.25 V to 27 V depending on the voltage applied to the input (input voltage must be greater than 3 volts from the output circuit).

Increasing the value of the components (R and / or C) resulted in an increase in the rise time of 1.25 V to a preset voltage with P1. By the number shown in the component list, the time is ± 3 seconds for 10 V Usort.

Soft start power supply Parts List :

BR1 = Bridge Rectifier 50V 1A (or more)
C1 = 470 uF 40V
C2 = 47 uF 40V
C3, C4 = 0.1 uF MKT
R1 = 220 Ohms
R2 = 4K7
R3 = 1K (to be adapted according to the output voltage)
D1, D2 = 1N4001
LED = LED
IC1 = LM317T
Linear potentiometer P1 = 2K5

SW1 = single switch or jumper (on / off timer)
T1 = BC557 (B or C)
TR1 = 1 V 12 VA transformer (to be adapted depending on the voltage and current output)