Various type of power supply circuit like fixed regulated, variable power supply, stabilized power supply circuit is already published in bestengineeringproject.com. Most of us hear about universal power supply, it is a power supply unit which provides almost all standard power supply. How’s that if we combine universal power supply and a digital control technology. Here, the innovative group of Dreamlover Technology design 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 universal digital power supply circuit
The circuit of universal digital power supply comprises 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 bridge rectifier build using diode D1 through D4 parallel connected capacitor C1 through C4 is for bypass undesired spikes and provide smooth and function-free power. For extra filter and eliminate ripple capacitor C5 and C13 is 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 multivibtator 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 RC network build by resistor R3 and capacitor C8. IC2 is a decade ring counter IC and utilize all the to outputs switch SW3 is connected to reset pin 15 and is pressed to reset IC2. The output of IC2 is connected to base of transistor T1 through T10 through resistor R6 through R11 respectively present 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 volt (-12v) DC is obtained at the output of IC3 and is indicated by LED2. IC3 is a fixed 3-terminal negative voltage regulator and produce regulated -12V DC.
IC4 is a adjustable voltage regulator and its output voltage obtained is dependent upon reference voltage between its output and the adjustable terminal. IC4 develops 1.25V normal reference voltage and is appears across through R16. The output at pin 4 of IC4 is calculated by using formula Vout=1.25(1+VRset/R16).
Where VRset is present VR1 through VR9. Adjust present VR1 through VR9 to get desired output. The collector of transistor T 5 is directly connected to 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 proper calibrated digital multi-meter you can easily adjust the present 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 is off.
Glowing LED1 is used to indicate mains ‘on’. Use proper heat sink for voltage regulator IC (IC3 and IC4). Since pin configuration these ICS are different so never fix single heat sink for both ICs.
PARTS LIST OF UNIVERSAL DIGITAL POWER SUPPLY CIRCUIT
Resistor (all ¼-watt, ± 5% Carbon)
R1, R7 – R15, R17 = 1 KΩ
R2 = 22 KΩ
R3 = 560 Ω
R4, R5 = 8.2 KΩ
R6 = 10 KΩ
R16 = 220 Ω
VR1 = 100 Ω
VR2 – VR4 = 1 KΩ
VR5 – VR7 = 2.2 KΩ
VR8, VR9 = 4.7 KΩ
C1, C4 = 47 nF (Ceramic Capacitors)
C5, C13 = 2200 µF/25V (Electrolytic Capacitors)
C6 = 10 µF/25V (Electrolytic Capacitors)
C7 = 0.01 µF (Ceramic Capacitors)
C8, C9, C12 = 0.1 µF (Ceramic Capacitors)
C10 = 1 µF/25V (Electrolytic Capacitors)
C11 = 0.22 µF (Ceramic Capacitors)
IC1 = NE555
IC2 = CD4017
IC3 = LM7912
IC4 = LM317
T1 – T10 = BC548
D1 – D4 = 1N4007
LED1 = RED LED
LED2 = YELLOW LED
LED3 – LED11 = GREEN
SW1 = ON/OFF Switch
SW2, SW3 = Push-to-on Switch
F1 = 1A Fuse
X1 = 220V AC Primary to 12V – 0 – 12V, 1A Secondary transformer