Microcontroller 12-volt programming power supply made of MC34063

Generally, microcontroller programmers require two power supplies, 5 volts and 12 volts. The 12 volt power supply is used for Flash programming. The 5-volt power supply can be obtained directly from the USB interface, and the 12-volt power supply can be made with MC34063, with an input of 5 volts and an output of 12 volts. The circuit is simple, no debugging is required, and the stability is good. My homemade programmer uses this method and it works very well. The electrical schematic diagram is as follows:

The inductor has a great influence on the performance of the power supply. It can be purchased as a finished product or wound on an I-shaped magnetic core with 0.1 enameled wire. The inductance is about 120 microhenries. If the rectifier diode D1 does not have a Schottky diode, an ordinary diode can also be used. The resistance values ​​of the voltage dividing resistors R3 and R4 must be accurate. They determine the size of the output voltage. If the output voltage is inaccurate, the size of resistor R4 can be fine-tuned. There are no special requirements for other components. Generally, if the circuit and components are correct, they can work normally without debugging. This circuit can output tens of milliamperes of current, which can fully meet the needs of the programmer.