J
Jonathan Westhues
- Jan 1, 1970
- 0
Aubrey McIntosh said:Why not use a zener instead of R1, R2, DZ1? The only thing I noticed
when simulating with LTSPICE was the power dissipation at R3 at 5V.
How would you connect it? If I understand correctly then DZ1 is not being
used as a shunt regulator. As soon as the voltage at the connection of R2
and R3 goes above Vref, the TL431 turns on all the way and Q1 snaps on. The
TL431 is either all the way on or all the way off, never in between.
That means that the overvoltage trigger point is insensitive to the Vbe of
Q1. It also means that M2 will be either on all the way or off all the way,
instead of turning off slowly as Vin goes above the limit.
Jonathan
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