Panasonic M12H power supply - power circuit - circuit diagram - Huaqiang Electronic Network

The color TVs utilizing the Panasonic M12H module include models such as the Panasonic TC-230H, TC-2030DHN, TC-830D, and TC-840D.

Oscillation Process

Approximately 300V DC voltage appears across C836. This voltage passes through the P801 and P2 windings of T801 and is applied to the collector of the internal switch of IC1 (pin 1). It is then transferred to the base of the internal switch of IC801 (pin 2) via R803. The transistor begins to conduct, allowing current to flow from the emitter (pin 4) of IC801. The current in the P1 and P2 windings of T801 increases, generating an induced voltage that couples into the windings of F2 and F3. At this point, the induced voltage polarity of the F2 and F3 windings is positive at F2 and negative at F3. This voltage is fed back to IC801 via C806 and R804 (pins 2 and 4), further increasing the switching transistor's current. Strong positive feedback causes the switching transistor to rapidly saturate.

Once the switching transistor reaches saturation, the voltage across the primary winding of T801 increases linearly. A 113V DC voltage forms at pin 4 of IC801, while T801 stores magnetic field energy. As C806 continues to charge, the voltage at pin 2 of IC801 drops continuously until the internal switch is pulled out of saturation.

When the switch exits saturation, the current in the P1 and P2 windings of T801 decreases, reversing the polarity of the induced voltage in each winding of T801. The voltage of the F2 and F3 windings is sent to IC801 via C806 and R804 (pins 2 and 4), reducing the current of the switching transistor even further. This cycle causes the switch to turn off quickly.

After the switch turns off, the voltage of the S1 and S2 windings of T801 turns on D801, establishing a 16V voltage across C810. The F1 and F3 windings also turn on D804, releasing the magnetic field energy stored in T801 to the 113V load through D804. The F2 and F3 windings of T801 discharge through C806, R804, D806, and T801 itself. Additionally, the 300V voltage is reverse-charged to C806 via R803, raising the voltage at pin 2 of IC801. A reverse pulse is also sent to pin 2 of IC801 via D805 and R805, turning on the IC801 in advance to initiate another oscillation cycle.

Regulator Circuit

The voltage regulation circuit is automatically handled internally by the STR456A.

Protection Circuit

If the 113V voltage rises, D837 turns on after being triggered by R842 and R843. This action turns on the thyristor Q833, shorting the 220V AC supply, and ultimately burning the fuse.