MC34161 5V switching power supply

Using this circuit diagram can be made a very simple voltage converter, which produces an output voltage of about 5V. Voltage converter is built using the MC34161 chip manufactured by Motorola, and allows an input voltage between 9.5V and 24V. Because this converter voltage is a switching type, dissipate very low heat . Maximum steady state current is 250 mA, although it can cope with peaks up to 750 mA.
Internal comparison of IC1's pin 2 is connected to the converter output voltage divider R4-R5, to monitor the output voltage. The second comparator (pin 3) is used in the oscillator circuit and directly connected to pin 6 and pin 5 by means of R3-C3.

When connecting power, the converter output, and thus the voltage on pin 2, is 0 (oscillator functions normally). Transistor T1 charge capacitor C5 through L1. When T1 is blocked, L1 provide power for C5, through the D1. When the voltage across C5's reached a sufficiently high level, the comparator changes state at pin 2. Oscillator is controlled in the lock pin 6, so that T1 is blocked again.