Absolutely usable switching power supply: Sanyo 83P power supply

Oscillation process:
The voltage of about 300V at the positive end of C310 is added to the B pole of the switching tube BG311 through R311 and R312. At the same time, it is added to the C pole of BG311 through the (4) and (6) windings of the switching transformer B301. The switching tube begins to conduct. The (2) and (3) windings of B301 generate (2) positive (3) negative positive feedback voltages, which are added to the B pole of BG311 through R335, D335, and C333, and BG311 quickly saturates.
After BG311 is saturated, the current in the (4) and (6) windings of B301 increases linearly, and B301 stores magnetic field energy. The E pole current of BG311 flows through R330, generating a linearly increasing sawtooth wave voltage on R330. This voltage is sent to pin (2) of A301 through C330, causing the two control tubes inside pin (2) to conduct. (3) Pin shunts the current of the B pole of the switch tube BG311. At the same time, the voltage at the negative terminal of C330 is also added to the B pole of BG311 through the (2) and (3) pins of A301, finally causing BG311 to exit the saturation state.
Once BG311 exits the saturated state, the polarity of the induced voltages in each winding of B301 will all reverse. The voltages of the windings B301 (2) and (3) will be fed back by R335 and C333, causing BG311 to quickly cut off.
During the cut-off period of BG311, D351, D353, D361, and D371 are all turned on, and the magnetic field energy stored in B301 is converted into electrical energy and released, thereby establishing four voltage groups of 180V, 130V, 16V, and 26V.
After BG311 cuts off, the (4) and (6) windings of B301 and C308, C309 and C310 produce free oscillation. After half a cycle, the 300V voltage charges C333 through R311 and R312. After a period of time, the cutoff period of BG311 ends, and the Enter the next cycle of oscillation.

Voltage stabilization process:
The voltage of the (1) and (3) windings of B301 is rectified by D332 to generate a DC voltage of about 30V on C327 and C328. The size of this voltage reflects the size of the output voltage. This voltage is rectified by A301. Pins (7) and (10) are sent to the internal sampling circuit to control the current of BG1, which also controls the conduction degree of BG2 and BG3, and ultimately controls the conduction time of switch tube BG311. This also controls the size of the output voltage.