How joule thief circuit works and demonstration this!
The circuit is an arrangement of a power source, a resistor, a transistor and a ferrite toroid core wrapped with two wires coming from the positive terminal of the power source, one through a resistor. A magnetic field is created around the ferrite toroid because of the current that passes through the wires. The extra current causes the transistor to switch off and power
to the ferrite toroid is cut off. As a result, the magnetic field is converted into electrical energy which is given as output. Once the magnetic field no longer exists(the pulse ends), the transistor is switched on again and conducts electricity to create the magnetic field again. This process occurs rapidly enough to provide a somewhat constant power output. The frequency of
voltage spikes generated by the Joule Thief circuit is over 5KHz.The inductance in the Joule Thief circuit is determined by the loops around the ferrite toroid. The more the number of loops, the greater the inductance. An increase in inductance generally decreases the current flowing through the circuit and an increase in the duty cycle(on time%). This suggests that an
increase in inductance increases the efficiency of the circuit. However, too much inductance is not good either. Trial and error can help find the sweet spot of the circuit where the least current is drawn. Increasing or decreasing one loop at a time will help find the number of loops a certain circuit requires for maximum efficiency.