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

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

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 (C pole) of the internal switch of IC1 (pin 1). It's then passed to the base (B pole) of the internal switch of IC801 (pin 2) via R803. This triggers the conduction of the transistor, allowing current to flow from pin 4 of IC801. The current in the P1 and P2 windings of T801 increases, generating an induced voltage that couples to the windings of F2 and F3. At this point, the polarity of the induced voltage in the F2 and F3 windings is positive at F2 and negative at F3. This voltage is applied to IC801 through C806 and R804 (pins 2 and 4), increasing the switching transistor current further, creating a strong positive feedback loop that rapidly saturates the transistor.

Once the switching transistor is saturated, the voltage across the primary winding of T801 increases linearly. A 113V DC voltage is formed at pin 4 of IC801, and T801 stores magnetic field energy. As C806 continues to charge, the voltage at pin 2 of IC801 decreases continuously, eventually pulling the internal switch out of saturation.

When the switching transistor 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 from 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, and the cycle repeats, causing the transistor to turn 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 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 R804, D806, and T801, while the 300V voltage is reverse-charged to C806 via R803, raising the voltage at pin 2 of IC801. The reverse pulse is also sent to pin 2 of IC801 via D805 and R805, turning on the IC801 ahead of time to initiate another oscillation cycle.

Regulator Circuit

The voltage regulator circuit is automatically completed internally by the STR456A.

Protection Circuit

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