Digitally Controlled Adjustable Voltage Regulator Circuit

A Digitally Controlled Adjustable Voltage Regulator Circuit is made to provide a changeable output voltage that can be customized for different circuit needs.

One popular choice is the IC LM317 which is a common voltage regulator that can give an adjustable output from 1.25V to 37V.

In this circuit the IC LM317 works together with digitally controlled transistors allowing users to pick different output voltages.

This is super helpful when you need different voltage levels, like in systems that use microcontrollers, power supplies and testing equipment.

Circuit Working:

Parts List:

The IC LM317 is a special gadget that helps control voltage and has three important parts.

It works by keeping a steady reference voltage of 1.25V between its output and adjustment parts.

To get the voltage we want we use a group of resistors connected together with the output the adjustment pin and the ground.

In this design we have several resistors named R2, R3, R4, R5 and R6 that help create different voltage levels.

The transistors Q1, Q2, Q3 and Q4 act like little switches.

They help us choose which resistor to use in the voltage setup.

When we turn on a transistor it connects its resistor to the circuit changing the output voltage based on which resistor we picked.

You can figure out the output voltage using this formula for resistors R2 to R6:

V_out = 1.25V × (1 + (R_set / R3)) + I_adj × R_set

Formulas with Calculations:

Below mentioned are the formulas with calculations for Digitally Controlled Adjustable Voltage Regulator Circuit:

V_out = 1.25V × (1 + (R_set / R3)) + I_adj × R_set

In this formula:

• R_set is the resistor we have used from R2, R3, R4, R5 and R6
• R3 is a fixed resistor that is set to 240Ω in this circuit.
• I_adj is a tiny adjustment current that we usually ignore because it is so small.

Using the above formula:

V_out = 1.25V × (1 + (R_set / 240Ω))

For example, if R_set is 1kΩ than,

V_out = 1.25V × (1 + (1000Ω / 240Ω))

V_out = 6.46V

Similarly, different resistances will provide different output voltages depending on the selection.

How to Build:

To build a Digitally Controlled Adjustable Voltage Regulator Circuit follow the below mentioned steps:

• Assemble all the components as mentioned in the above circuit diagram
• Connect ADJ pin 1 of IC1 to the resistor divider network between resistor R5 and R6
• Connect OUTPUT pin 2 of IC1 to Vout regulated output voltage.
• Connect INPUT pin 3 of IC1 to Vin input voltage
• Connect transistor Q1 to Q4 collector pin connect to the voltage divider resistors R3 to R6 as per your adjustment through the mentioned formulas.
• Connect transistor Q1 to Q4 base to a digital control input A, B, C, D.
• Connect transistor Q1 to Q4 emitter to ground.
• Connect resistor R2 from the junction of resistor R3 and GND
• Connect resistor R1 one terminal from OUTPUT pin 2 and other terminal connect to resistor R6
• Connect capacitor C1 one terminal from INPUT pin 3 and other terminal connect to GND.
• Connect capacitor C2 positive from OUTPUT pin 2 and negative of capacitor connect to GND.

Conclusion:

This Digitally Controlled Adjustable Voltage Regulator Circuit features a voltage regulator that can be adjusted digitally with the help of an LM317.

Users can choose various output voltages by turning on different transistors, which makes it great for projects needing different voltage levels.

This method makes it easier to select voltages in embedded systems, testing tools and DIY power supply projects.

References:

Adjustable/Programmable Voltage Regulators – Linear, Low Drop Out (LDO) Regulators