12 Volts to 9 Volts DC Converter

This compact circuit efficiently converts a 12V DC input to a stable 9V DC output using a Zener diode and a transistor regulator stage.

The main components are:

• ECG184 (or equivalent NPN power transistor) – acts as the series pass transistor, regulating current flow to maintain output voltage stability.
• 9.1V Zener diode – provides a reference voltage to control the transistor’s base, ensuring the output remains close to 9V even with input fluctuations.

When 12V is applied, the Zener diode conducts and biases the transistor to regulate the output voltage. The circuit offers good load regulation, low ripple, and adequate current capability for small electronic devices operating at 9V.

This converter is ideal for powering radios, small amplifiers, or battery chargers from a 12V source such as a car or solar system.