Series regulated power supply circuit protection circuit 2

It uses photoelectric coupler B
as the protection control component. This circuit has current-cutting protection and current-limiting protection
functions. When there is no resistor Ri in the figure, when the output is short-circuited
, U. . ≈o, the photoelectric coupler B does not work, the transistor VTz
is cut off, and the adjustment tube VTi is cut off, thus playing a current-cutting protection role
; when there is a resistor Ri, when the output is short-circuited, although B
is cut off, the base of VT2 is cut off due to Ri. There is a certain current, so that
VTi still has a certain current output. As long as the resistance value of Ri is appropriately selected
, a certain output current can be obtained, thus playing
the role of current limiting protection.