Panasonic L15 power supply - power circuit - circuit diagram - Huaqiang Electronic Network

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TV models using the Panasonic M15L movement are: TC2171, TC2173, TC2185, TC2186, TC-D21, TC-D25, etc. The main switching power supply is composed of STR50213, which belongs to the series type regulated power supply.

Oscillation circuit

The DC voltage of nearly 300V on C847 is applied to the C pole of the internal switch of IC801(3) through the primary windings P1 and P2 of the energy storage transformer, and is added to the B pole of the internal switch of IC802(2) via R803. Thereby the switch tube is turned on. Thus, the voltages of the P1 and P2 windings are coupled to the F2 and F3 windings, and the generated positive feedback voltage is applied to the (2) and (4) pins of the IC801 via C806 and R804 (ie, the B and E pins of the internal switch). The tube is rapidly saturated.

During the saturation of the switch, current flows from the (4) pin of IC801, establishing a DC voltage of 113V on C808, while T801 stores magnetic energy. At this time, since the feedback capacitor C806 is continuously charged, the voltage of the internal switch tube of the IC801(2) pin is getting lower and lower. When it falls to the saturation of the switch tube, the switch tube will exit the saturation state and the C-pole current will decrease. The polarity of the induced voltage of each winding of T801 is reversed, and the voltage on the windings of F2 and F3 is quickly cut off by C806 and R804.

After the switch is turned off, C806 is discharged through the windings of R805, D806, F3, and F2, and the voltage of 300V is reversely charged to C806 via R803, so that the potential of (2) of IC801 rises, and the pulse of reverse stroke is sent to IC801 via D805 ( 2) The foot ends the cut-off period of the switch tube and enters the saturated state after positive feedback, thus forming an oscillation.

Regulator circuit

The voltage regulator circuit is internally implemented by the STR50213.

protect the circuit

Q834 is a 113V overvoltage protection circuit. When 113V is normal, Q834 is cut off. If 113V is too high, Q834 is turned on, 113V is shorted, and the switching power supply stops.

Q851 is a 12V short-circuit protection circuit. If 12V is short-circuited, Q851 is turned on and Q814 is turned off. This is equivalent to remote shutdown.

The M15L movement also has several protections, which are for the (42) foot of the IC601 and will not be discussed here.

Auxiliary power supply and remote shutdown circuit

When the power is turned on normally, the (6) pin of the CPU outputs a high level, which makes Q814 turn on. At this time, Q810, Q811, Q812, and Q813 are all turned off, and the auxiliary power supply does not work.

During standby, the (6) pin of the CPU outputs a low level, which causes Q814 to be turned off, Q811 is turned on, and the (5) pin of IC801 is grounded via R853, and the main power circuit stops working. On the other hand, 300V DC voltage passes through R809 and R810. The Q810B pole is supplied with a bias current, the Q810 is turned on, the Q810 current flows through the R815, D813 indicator, and the D814 generates a 5V DC voltage on the C811 as the CPU supply voltage. Q813 is a voltage regulator circuit for 5V power supply. It consists of R812 and D810 to form a 4.3V reference circuit. It provides a 4.3V reference voltage to the E pole of Q813. The B pole of Q813 provides 5V sampling voltage from R811, and D811 is 10V voltage regulator.