Step-down MC34063 – 12-3.3V/500mA

Articles2015-12-05
Auhtor: Petr Šrámek

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.

Block diagram of converter:

Schema:

PCB for using laser printer toner transfer:

Table of measured values:

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:




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