AC stabilized power supply circuit suitable for upper limit voltage stabilization

This circuit only stabilizes the voltage at the upper limit, that is, when the grid voltage exceeds the specified value (such as 220V),
the voltage is stabilized, but when it is lower than the specified value, the voltage cannot be stabilized .
    The voltage adjustment is completed by the thyristor V; the equivalent single-junction transistor is composed of triodes VT3 and VT4;
the trigger circuit is composed of capacitors C, VT3, VTt and resistors R8, R9; the voltage dividing circuit composed of R8 and Rg makes VT3 The base potential
rises in proportion to the input voltage.