This is next circuit switching converter. This converter reduces the voltage from 12V to 3.3V with very popular DC/DC converter MC34063. The coil was calculated on the 22uA, but the efficiency was very low. The coil is 470uH/3A because other coil wasn’t to available. A efficiency is 73.086%. In the datasheet is efficiency 80%. The switching converter was designed for 500mA with max ripple 100mV. When measuring ripple was the current drawn 550mA. Frequency of switching was 68KHz.
PCB for using laser printer toner transfer:
The graph of output voltage depending on the output current:
The graph of efficiency depending on the output current:
Ripple of output voltage (for 550mA):
Pictures:
