I have changable dc voltage between 5 to 9 VDC I want to produce constant +15Vdc or Constant +24Vdc from my source(between 5 to 9 VDC ). Anybody have any idea or circuit.
This depends on the current you require in your application.
Easy solution is , for example, the LM2577 regulator ( **broken link removed** ).
So, how many AmPs. mAmps, µAmps dou you need?
Regards,
IanP