Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.
When Sm is changed to off, current trough L1 still wants to flow, but there is not path. As a result L1 voltage will be increased. Because output voltage is constant (regulator) , voltage at the emitter of Sm is going down until it is limited by something. In this case for emiter voltage of -Vd diode d12 is on.
When Sa or Sm conducts, there are a path and L1 starts charging. but when Sa or Sm stop conducting, there are no path but L1 opposes to changes in the flux of current so it needs a path for it. D12 is to provide a path for L1 when Sa and Sm doesn't work.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.