Universal Digital Power Supply Circuit

Various types of power supply circuits like fixed regulated, variable power supply, and stabilized power supply circuits are already published on bestengineeringproject.com. Most of us hear about the universal power supply, it is a power supply unit that provides almost all standard power supply. How’s that if we combine a universal power supply and a digital control technology. Here, the innovative group of Dreamlover Technology designed and verified a universal power supply circuit with the facility of digital control. The unit universal digital power supply provides a variable, fluctuation-free and regulated output.

Circuit description of the universal digital power supply circuit

The circuit of the universal digital power supply comprises an adjustable 3-terminal positive voltage regulator IC (Lm317), decode counter IC (CD4017), timer IC (NE555), and a fixed-negative-voltage regulator (Lm7912). The input AC of 220V is steeped down by using transformer 12V-0-12V, 1A secondary. The step-down voltage is rectified using a bridge rectifier built using diode D₁ through D₄ parallel-connected capacitor C₁ through C₄ is for bypassing undesired spikes and providing smooth and function-free power.

For extra filter and to eliminate ripple capacitors C₅ and C₁₃ are used. Here both positive and negative power supply is utilized and fluctuation-free output is obtained. Timer IC NESS (IC₁) is wired as an astable multivibrator and generates clock pulse when switch SW₂ is pressed switch SW₂ is also used as voltage selector. The output of IC₁ from pin 3 is given to clock pin 14 of IC₂ through the RC network built by resistor R₃ and capacitor C₈. IC₂ is a decade ring counter IC and utilizes all the outputs switch SW₃ is connected to reset pin 15 and is pressed to reset IC₂.

The output of IC₂ is connected to the base of transistor T₁ through T₁₀ through resistor R₆ through R₁₁ respectively preset VR₁ through VR₉ is connected to the collector of transistor T₂ through T₁₀ respectively for voltage adjustment LED₃ to LED₁₁ is used to indicate 1.5V, 3V, 4.5V, 5V, 6V, 7.5V, 9V, 10.5V, 12V DC respectively. Negative 12 volts (-12v) DC is obtained at the output of IC₃ and is indicated by LED₂. IC₃ is a fixed 3-terminal negative voltage regulator and produces regulated -12V DC.

IC₄ is an adjustable voltage regulator and its output voltage obtained is dependent upon the reference voltage between its output and the adjustable terminal. IC₄ develops a 1.25V normal reference voltage and appears across R₁₆. The output at pin 4 of IC₄ is calculated by using the formula V_out=1.25(1+VR_set/R₁₆).

Where VRset is preset VR₁ through VR₉. Adjust preset VR₁ through VR₉ to get desired output. The collector of transistor T _­5 is directly connected to the ADJ terminal (pin 1) of IC₄, so the output voltage of IC₄ will be the voltage across fixed resistor R₁₆ which is equal to 1.25V. By using a properly calibrated digital multi-meter you can easily adjust the presets to obtain 1.5V to 12V. Where IC₂ is reset by using switch SW₃ the output voltage at pin 4 of IC₄ is 1.2V and all the voltage-indication LEDs are off.

Glowing LED₁ is used to indicate mains ‘on’. Use proper heat sink for the voltage regulator IC (IC₃ and IC₄). Since pin configuration these ICS are different so never fix a single heat sink for both ICs.

Check out other power supply circuit posted on bestengineeringprojects.com

1. Adjustable Ripple-Regulated Power Supply Using 741
2. Variable Switching Power Supply
3. Arduino Controlled Variable Power Supply
4. Stabilized Power Supply With Short-Circuit Indication
5. Short Proof Variable Power Supply
6. Adjustable Bipolar Voltage Regulator Circuit Using LM337
7. Self Switching-off Power Supply
8. Dual Polarity 5v from 9v Battery
9. 3.7V to 5V, 5.3V and 6V Converter Circuit

PARTS LIST OF UNIVERSAL DIGITAL POWER SUPPLY CIRCUIT