Transformerless power supply FET

The circuit shows a diagram of a simple transformerless power supply for transistor BUZ41A. Through the inclusion of the common-drain transistor VT1 NW capacitor charging to a voltage of about 3 smaller than the zener voltage of VD4. An alternating voltage with a phase shift, determined by the capacity of the capacitor C1, transistor opens VT2, which stops the charge capacitor NW at the beginning of each positive half-wave supply voltage.

Parts list :
R1 : 470 K
R2 : 100 K
R3 : 560 K
R4 : 6,6 ohm
C1 : 33nF
C2 : 100nF/400 V
C3 : 1000uF/16V
VD1, VD2, VD3 : 1N4007
VD4 : 15V