Build a Low Power Variable Voltage Converter

Using electronic diagram below can be made a voltage converter that allows laps positive voltage of existing power sources, or convert it into a negative voltage.

New supply is electrically isolated from the source through the ferrite transformer wound on a torus G2-3FT12. Primary winding consists of 30 turns. Number of turns in the secondary, n, is calculated using the equation: n = 30 Uo / Ui, where Uo is the desired voltage and Ui is the input voltage. Add to compensate pieriderior 20.05.10 turns. If the output voltage is higher, it can always reduce Pi. Both coil windings can be enamelled copper wire with a diameter of 0.3 mm.

 Low Power Variable Voltage Converter Circuit Diagram:

Converter Circuit Diagram

The transformer is controlled by a gate CMOS Schmitt trigger and Do with transformed into a rectangular signal generator R1 and C1.

Additional current to charge C1 is provided by R2 and Pi, which controls the duty cycle of the rectangular signal. The signal frequency is about 220 kHz and fill factor or should be less than 0.5.

When T1 is opened, some of the energy is transferred to the secondary winding and some is stored in the magnetic circuit. When T1 conduction ceases, the magnetic field energy transfer in the secondary winding.

The current through Q1 will increase dangerously if secondary task is too big. Average current through the primary should not exceed 150. The report gave the scheme, secondary task can not be less than 80 ohms.
Besides excessive loads should also avoid working without load.

Converter efficiency at a supply voltage of 15 V is about 65%. The low current load, it decreases to about 50%. Efficiency also decreases when the supply voltage is lower than indicated. The current drawn from the source of 15 V for a load of 80 ohms is about 165 mA.

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