Schmitt to throttle 555 timer based boost circuit

[mikeinfodoc]

I have a simple/typical DC-DC switch-mode Boost circuit. (with typical inductor, switch, diode and cap)

It uses a 555 for its switching.

I wanted to limit the output voltage of this boost circuit to a defined range, by adding a inverting schmitt to the reset pin of the 555 timer.  (so the schmitt would serve as the "feedback" to the 555 timer via the reset pin)


Such that:
    when the 555 boost circuit output exceeds a certain HIGH threshold voltage, the schmitt forces the 555 reset pin low.
    when the 555 boost circuit output becomes lower than a certain LOW threshold voltage, the schmitt forces the 555 reset pin high.

Therefore, any Vout within the defined voltage output range (aka: the schmitt "hysteresis") would keep the 555 reset pin unchanged.

In other words,
   if the boost output goes too HIGH, the astable 555 stops switching.
   if the boost output goes too LOW, the astable 555 starts switching.



Before I submit my schematic, I want to see if this makes sense, from a conceptual standpoint.

Thank you for any "feedback."

[boostbuck]

Here's my minimal part count 555-based boost for a 12v battery.  It has served well as supply for various jobs.  Changing the zener alters the output voltage.  Not very regulated, but follow it with a 317 to clean it up if necessary.

[boostbuck]

My typo:  R4 is 150R not 1K5

[T3sl4co1l]

Yikes, no current limiting!  No input filtering!

If you MUST use a 555, use it this way: https://www.seventransistorlabs.com/Images/555%20Boost.pdf

But much preferable to use a UC3843.  Just as many components, but it's actually safe to use.

Tim