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Date: 03-01-17

DC power supply circuits

From simple LED light to embedded boards all need clean regulated DC power supply. Here we give few schematic diagrams to build power supply circuits from simple to complex types. If power consumption is a critical factor go for switching only.

Here is one most popular, old, reliable and simple circuit for fixed DC power supply. These are ideal for circuits with an average current requirement of less than 1.00 amp.

5V/9V/12V fixed power supply (Positive) at 1 Ampere current rating

Circuit Diagram (Schematic Diagram)-1


L1 = Step down transformer with i/p of 230 AC 50 Hz and output of (XX ) - 0- (XX)) volts(rms).
XX  = Required DC output voltage.


Here is the table for different voltages

Output voltage (DC Volts) Transformer rating (rms Volts)
5 230: 5-0-5
9 230:9-0-9
12 230:12-0-12
15 230:15-0-15

 

The current rating has to be more than 1 Amp.

D1, D2 = Diodes 1N4003
D3 = Diode 1N4003/ 1N4001 (optional)
C1 = 1000 Micro Farad aluminum electrolytic capacitor (For loads less than 100mA you can sustitute with 220 microfards capacitor), Voltage rating = 2.5 times of Output Voltage.
C2 = 10 Micro Farad aluminum electrolytic capacitor
IC1 = 7805 for + 5V DC output
       =7809 for +9V DC output
       =7812 for +12V DC output
       =7815 for +15V DC output

 

 

5V/9V/12V fixed power supply (Negative) at 1 Ampere current rating

Circuit Diagram (Schematic Diagram)-2

L1 = Step down transformer with i/p of 230 AC 50 Hz and output of (XX ) - 0- (XX)) volts(rms).
XX  = Required DC output voltages.

 

Output voltage (DC Volts) Transformer rating (rms Volts)
5 230: 5-0-5
9 230:9-0-9
12 230:12-0-12
15 230:15-0-15

The current rating has to be more than 1 Amp.


D1, D2 = Diodes 1N4003
D3 = Diode 1N4003/ 1N4001 (optional)
C1 = 1000 Micro Farad aluminum electrolytic capacitor(For loads less than 100mA you can sustitute with 220 microfards capacitor). Voltage rating = 2.5 times of Output Voltage.
C2 = 10 Micro Farad aluminum electrolytic capacitor
IC1 = 7905 for -5V DC output
       =7909 for -9V DC output
       =7912 for -12V DC output
       =7915 for -15V DC output

Datasheet link: 1N4003 - www.fairchildsemi.com/ds/1N/1N4007.pdf

                             78XX - www.fairchildsemi.com/ds/LM%2FLM7805.pdf (more circuits can be found in this datasheet)

                             79XX- www.fairchildsemi.com/ds/LM%2FLM7905.pdf

Additional note: It's safer to put one heat sink to 78XXX and 79XX IC for safeguarding the IC from overheating
In case you are using both the power supplies the ground connection of both positive and negative power supplies can be shorted.

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