Mar 062017
 

12VDC to 9VDC Converter

This 12VDC to 9VDC converter is very useful for powering 9VDC devices in a car that uses 12VDC battery. The maximum current consumption allowed by this circuit is 0.8 amps.

This 12VDC to 9VDC converter is implemented using a zener diode and a NPN bipolar transistor as shown in the circuit diagram.

To understand the operation of this circuit, the following article is recommended: Voltage regulator with zener diode.

How the 12VDC to 9VDC Converter works?

As in the voltage regulator with zener, from the suggested link above, a series resistor is used (on this case, R1 and R2 are used in parallel).

12VDC to 9VDC Converter Circuit

The output voltage of the circuit is the zener diode voltage plus the emitter – base voltage of transistor Q1. (Vout = Vz + Vbe). Vout = 8.2 – 0.7 = 8.9 volts. The NPN transistor allows a greater variation of current demand from the load, than when only the zener diode is used.

Notes:

  • Use a heatsink as large as possible for transistor Q1.
  • The converter input voltage must not exceed 14 Volts.

List of components for converter 12VDC to 9VDC

  • 1  TIP41C NPN bipolar transistor or similar (Q1)
  • 2  6.8 ohm resistors (5 watts or more) (R1, R2)
  • 1  8.2 volt zener diode 1N756 or similar (D)
  • 1 Heatsink for transistor Q1 (required)

Printed circuit for 12VDC to 9 VDC converter

The following diagrams shows a suggested printed circuit board (PCB) and an approximate view of the final circuit appearance.

12vdc to 9vdc Converter PCB

12vdc to 9vdc converter circuit PCB

  •  
  •  
  •  
  •  
  •  
  •  
  •  
  •  
 Circuit diagrams Tagged with: ,  Add comments

 Leave a Reply

(required)

(required)