Adjustable Power Supply

What is an Adjustable Power Supply?

An adjustable power supply is a device that can supply high amounts of power (W) through means of an adjustable voltage (V). This way, power can be supplied to a variety of devices without the need of individual power supplies (but you may need a new connector!).

Watch my new video that shares a simple way to think about adjustable power supplies! Well talk about…

– The two main devices involved

– Testing the devices

– Other considerations + my DIY

Circuit Schematics:

Adjustable Power Supply:

Falstad Circuit Embed

12V Power Supply:

Falstad Circuit Embed

A typical 12v power supply turns the 120VAC (rms) from an outlet into a steady 12VDC. If we were to break this device down even further, the blocks would be as follows:

– Transformer to turn 120VAC (rms) into 12VAC (rms)

– Full Bridge Rectifier to turn 12VAC into 16.9VDC (peak of AC signal)

– 12v Voltage Regulator (not shown) to turn 16.9VDC to a steady 12VDC.

Buck-Boost Converters:

Falstad Circuit Embed

A typical Buck_Boost Converter turns the 12VDC from the input into an DC Voltage within a range (ex. 1VDC – 30VDC). If we were to break this device down even further, there are two operations to highlight:

1. Switch (MOSFET) is closed (ON)

– Due to the diode blocking current flow, the inductor begins to steadily increase in current. This current in the inductor contributes to stored energy in its magnetic field. This continues to build until the switch is opened (MOSFET is turned off).

2. Switch (MOSFET)is opened (OFF)

– The inductor, with its stored energy, wants to keep the current flowing, but now the switch is open creating an open circuit. So, it starts pulling current from the diode-resistor loop. This creates a voltage across the resistor (the load!), which is what is desired. The capacitor will help to smooth out the changes in current so that the voltage across the resistor is niceeee and smoothhh.

By varying how fast the switch opens and closes (frequency) and the on/off time of the switch (Duty Cycle), we can adjust the voltage at the output to be GREATER or LESS than the input voltage!