Parallel DC regulated power supply circuit

Shown is a parallel DC regulated power supply circuit. The 220V power supply is stepped down by a transformer, followed by full-wave bridge rectification, capacitor filtering,
voltage stabilization and tube stabilization, and the output DC voltage is supplied to the load. The output current voltage is equal
to 0.9 times the secondary side voltage of the power transformer. Due to its simple circuit, this power
supply is used in less demanding situations. ,
    the mains power U1 (Ul -220rD is stepped down by the transformer to obtain the AC voltage
U2 (UZ "UI N2 /N,). The AC voltage U2 is passed through the single-phase bridge rectifier circuit
to obtain the DC voltage U (Uz≈l.2?L2 ), in order to prevent sudden voltage
changes in the circuit, the capacitor and the load resistor must be
connected in parallel through the filter circuit to absorb the pulsating current and keep the output voltage stable. The output voltage after going through the
rectifier filter circuit and The DC voltage we seek is still quite far away. In order to obtain a more stable DC power supply,
we need to stabilize the voltage through the voltage stabilizing circuit after the rectifier and filter circuit, thus obtaining the DC voltage we seek.