How to Connect a Zener Diode to Regulate a Power Supply

Regulated power supplies typically convert an alternating current (AC) voltage to a specified direct current (DC) voltage. A regulated power supply requires the AC electrical energy to be rectified, and for the rectified voltage to be “smoothed out” of any power surges called ripple voltage.

One reliable way to reduce the effects of ripple voltage is to use an active electronic component called a Zener diode. A Zener diode assists the electronic circuit by providing a constant voltage level despite changes in electrical current.

Things You'll Need

• 12V AC power supply
• Rectifier pack
• Dielectric (non-polarized) capacitor
• Zener diode (such as a 1N4742 diode)
• Electrical wire
• Electrical pliers
• Soldering iron
• Electronic (rosin core) solder
• Two ring terminals

Instructions

1. Cut six lengths of wire, and strip each end of 1/2 inch of insulation. Connect one end of the first wire to one of the AC leads on the rectifier pack, and solder the connection. Connect the other end of this wire to one of the power supply terminals. Connect one end of the second wire to the other AC lead on the rectifier pack, and solder the connection. Connect the other end of this wire to the unconnected power supply terminal.

2. Connect one end of the third wire to the positive (+) lead on the rectifier pack and solder the connection. Connect the free end of the third wire jointly to the Zener diode cathode (which is marked with a line on the diode body) lead and to one of the capacitor leads. Solder this connection.

3. Connect one end of the fourth wire to the negative (-) lead on the rectifier pack, and solder the connection. Connect the other end of the fourth wire jointly to the free capacitor lead, and to the Zener diode anode. Solder this connection.

4. Slip one ring terminal over one end of the fifth wire, and solder the terminal to the wire. Attach the other end of the fifth wire to the diode cathode lead, and solder the connection. Slip the remaining ring terminal over one end of the sixth wire, and solder the terminal to the wire. Attach the sixth wire to the diode anode lead, and solder the connection.

Tips & Warnings

• When wired as above, this circuit should show a consistent voltage within 5 percent of 12 Volts DC across the ring terminals.

References

• Rectifier/Filter Circuit
• Electronic Devices; Thomas Floyd; 1996
• Zener Diodes

Resources

• Chenyi Electronics: 1N4728 Thru 1N4764 1W Silicon Planar Zener Diodes (PDF)