NE555 DCDC 12V->19V Regulated

Here is a schema of a DCDC Boost based on NE555 with regulated around 20V (most of laptops).

Pro:
This is regulated by a zener and NE555 only.
Most of the component can be easily replaced by others.
The input voltage can drop under 9V.
You can wire the inductance by hand (DIY)

Cons:
The output is rising to 31V when the output is open circuit. (and I don't know how long this situation can keep going until a component will fail).
Some information on the schematic are in french.
There is no safety except a fuse at input.
The converter is buzzing a little bit.