No electronics can run without power, to be precise a low voltage DC power, and a power supply unit is a device which is specifically meant for fulfilling this purpose.
Main Components of a Power Supply Circuit
- Rectifier (Diode)
- Filter (Capacitor)
- Voltage Regulator
The voltage regulator provides the regulated output. There are many voltage regulator ICs available in the market. For 5V dc output we can use LM7805, for 9 V dc power supply we can use LM7809 and for 12V dc power supply LM7812 can be used.
- Using Single Diode
- Using Two Diodes
- Using 4 Diodes
Power Supply Circuit Using Single Diode
However, the above configuration cannot be considered an efficient power supply design due to its crude half wave rectification and limited output conditioning capabilities.
Power Supply Circuit Using Two Diodes
This results in poor core saturation and unnecessary heating of the transformer, making this type of power supply configuration less efficient and ordinary design.
Power Supply Circuit Using Four Diodes
The clever use of four diodes makes things very simple, only a single secondary winding is all that is required, the core saturation is perfectly optimized resulting in an efficient AC to DC conversion.
Moreover, these configurations does not include a variable voltage and current control features. However the above problems can be overcome through the use of a single IC and a few other passive components in those designs.
9 V regulator using 7809
Here is the circuit diagram of 9 V regulator using popular 7809 IC.
If a current of 300 mA or above is required, fit a proper heat sink to the IC 7809. If 1A bridge is not available, make one using four 1N 4007 diodes.