This circuit regulates a DC power output. It has a very wide application range. It can be used to control the speed of a motor, a pump, a toy train, the brightness of a LED or lamp, etc. Practically, it can be used in any application that uses a regulated DC power with pulse width modulation (PWM).
It was originally used as a jumbo LED dimmer.
The circuit works this way: the A1 opamp functions as a square wave generator. At its non-inverting input is a by product triangle wave signal. The IC A2 following it functions as a simple comparator. A reference voltage is fed to the inverting input of the A2 IC via the potentiometer P1. The output of A2 is a square wave signal with a constant frequency of around 200 Hertz.
This signal has a variable pulse width from 0 to 100%.
The P1 sets the trigger point of the pulse. The transistor T1 works as the actual regulator by switching a relatively high current with a maximum of 5 amperes. The power supply voltage must be between 5 volts (minimum) and 30 volts (maximum). Take note that the lower the supply voltage is, the lower the efficiency of the dc regulator becomes.