Switched Mode Power Supply Voltage Control via PWM

A simple modification to a 36V 15A SMPS unit that enables output voltage control via PWM. The control range is about 14% to 110% (5V to 40V). In this video the maximum output is set at 35V.

The video shows the voltage and current going into a dummy load consisting of 9x 12v50W halogen bulbs connected as 3S3P. Also shown on an oscilloscope is the input PWM signal from an Arduino, and the output voltage.

The Arduino is outputting the control voltage using AnalogWrite, which has a frequency of 490Hz, and the output voltage can be seen modulated at this frequency. But using "proper" proper PWM at 5KHz, and 10 bit resolution would be much better, and the capacitors in the circuit could be reduced for quicker response time.

The circuit is here: https://imgur.com/xrqVH2C
The internal mods are shown here: https://imgur.com/WfakM1l