2 Watt Switching Power Supply: Build Your Own Circuit

In this miniature power supply, a Schmitt trigger circuit is employed to manage a switching transistor, which then provides power to a smaller inductor. Magnetic energy accumulates within the inductor during the transistor’s conduction phase and is subsequently discharged into the load circuit upon the transistor’s transition to a non-conducting state. The output voltage is intrinsically linked to the load resistance and is constrained by a zener diode, effectively terminating the oscillation when the voltage reaches approximately 14 volts. Adjustments to the voltage divider supplying the zener diode enable variations in the resultant voltage levels. The system exhibits an efficiency of around 80% thanks to the utilization of a high Q inductor.

Schmitt Trigger

A Schmitt trigger is an electronic component that exhibits hysteresis, a characteristic where the output state changes depending on whether the input signal is rising or falling. This hysteresis provides stability to the oscillator circuit. The trigger ensures the oscillator remains stable and prevents unwanted oscillations due to noise. It acts as a comparator, switching between two distinct states based on the input signal’s polarity.

Zener Diode

A zener diode is a specially designed semiconductor diode that operates in reverse breakdown region. It maintains a relatively constant voltage across its terminals when reverse bias is applied, providing a stable reference voltage. This property makes it useful for voltage regulation, clipping, and protection circuits. Typical zener diodes are rated for a specific breakdown voltage, commonly 14 volts in this example, ensuring the output circuit operates within a predefined range.

Circuit diagram