Absolutely usable switching power supply: Panasonic M12H power supply

Color TVs using Panasonic M12H movement include: Panasonic TC-230H, TC-2030DHN, TC-830D, TC-840D, etc.

During the oscillation process
, the DC voltage of about 300V on C836 is added to the C pole of the internal switch tube of pin (1) of IC801 through the P1 and P2 windings of T801, and at the same time, it is added to the B pole of the internal switch tube of pin (2) of IC801 via R803. , the switch tube begins to conduct, and the E pole current flows out from pin (4) of IC801. The current of the P1 and P1 windings of T801 increases, generating an induced voltage, which is coupled to the F2 and F3 windings. At this time, the polarity of the induced voltage of the F2 and F3 windings is F2 positive and F3 negative. This voltage is added to the IC801 (2 ), (4) pin, thereby further increasing the switch tube current, and the strong positive feedback causes the switch tube to quickly saturate.
After the switch tube is saturated, the voltage of the primary winding of T801 increases linearly. On the one hand, a 113V DC voltage is formed at pin (4) of IC801, and at the same time, T801 stores magnetic field energy. As C806 continues to be charged, the voltage of IC801 (2) pin continues to decrease, and finally the internal switch tube exits the saturation state.
Once the switching tube exits the saturated state, the current of the P1 and P2 windings of T801 will decrease, the polarity of the induced voltage of each winding of T801 will be reversed, and the voltage of the F2 and F3 windings will be sent to (2) and (4) of IC801 through C806 and R804. ) pin, the current of the switch tube is further reduced, and this cycle makes the switch tube cut off quickly.
After the switch is turned off, the voltage of the S1 and S2 windings of T801 turns on D801, establishing a 16V voltage on C810; the F1 and F3 windings turn on D804, and the magnetic field energy stored in T801 is released to the 113V load through D804, while C806 passes through The F2 and F3 windings of R804, D806, and T801 are discharged, and the 300V voltage is reversely charged to C806 through R803, causing the voltage of pin (2) of IC801 to rise, and the reverse pulse is also sent to pin (2) of IC801 through D805 and R805. Make IC801 conduct in advance and start another oscillation cycle.

Voltage stabilizing circuit
The voltage stabilizing circuit is automatically completed internally by STR456A.

Protection circuit
If the 113V voltage rises, D837 will be turned on after being divided by R842 and R843, and the thyristor Q833 will be turned on. The 220V AC will be short-circuited and the fuse will burn out.