Panasonic L15 power supply

Relevant key device information applied in this article: SRT51213 D973 C1573 C1685 AN7812 TV models using Panasonic M15L movement include: TC2171, TC2173, TC2185, TC2186, TC-D21, TC-D25, etc. The main switching power supply is composed of STR50213, which is a series regulated power supply. The DC voltage of nearly 300V on the oscillation circuit C847 is added to the C pole of the internal switch tube of IC801 (3) through the primary windings P1 and P2 of the energy storage transformer, and at the same time, it is added to the B pole of the internal switch tube of IC802 (2) via R803. on, thus causing the switch tube to turn on. In this way, the voltage of the P1 and P2 windings is coupled to the F2 and F3 windings, and the generated positive feedback voltage is added to the (2) and (4) pins of IC801 (i.e., the B and E pins of the internal switch tube) through C806 and R804, causing the switch to The tube saturates rapidly. During the saturation of the switch tube, current flows out from pin (4) of IC801, establishing a DC voltage of 113V on C808, and T801 stores magnetic energy at the same time. At this time, because the feedback capacitor C806 is constantly being charged, the voltage of the internal switch tube at IC801 (2) pin is getting lower and lower. When it drops to the point where it cannot maintain the saturation of the switch tube, the switch tube will exit the saturation state and the C pole current will decrease. As a result, the polarity of the induced voltage in each winding of T801 is completely reversed, and the voltage on the F2 and F3 windings passes through C806 and R804 to quickly cut off the switching tube. After the switch tube is turned off, C806 discharges through the windings of R805, D806, F3, and F2. At the same time, the 300V voltage reversely charges C806 through R803, causing the potential of pin (2) of IC801 to rise. At the same time, the reverse pulse is sent to the ((2)) of IC801 through D805. 2) Pin, the cut-off period of the switching tube ends, and it enters the saturated state again after positive feedback, thus forming an oscillation. Voltage stabilizing circuit The voltage stabilizing circuit is completed internally in STR50213. Protection 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 short-circuited, and the switching power supply stops oscillating. Q851 is a 12V short-circuit protection circuit. If 12V is short-circuited, Q851 will be turned on and Q814 will be turned off. This is equivalent to remote control shutdown. The M15L movement also has several protection channels, which are all for the (42) pin of IC601, and will not be discussed here. When the auxiliary power supply and remote control shutdown circuit are turned on normally, pin (6) of the CPU outputs a high level, turning on Q814. At this time, Q810, Q811, Q812, and Q813 are all cut off, and the auxiliary power supply does not work. In standby, pin (6) of the CPU outputs a low level, which turns off Q814 and turns on Q811. Pin (5) of IC801 is grounded through R853, and the main power circuit stops working. On the other hand, the 300V DC voltage passes through R809 and R810. Provide bias current to the Q810B pole, Q810 is turned on, the current of Q810 flows through R815, D813 indicator light, and D814 generates a 5V DC voltage on C811, which is used as the power supply voltage of the CPU. Q813 is a voltage stabilizing circuit for 5V power supply. It consists of R812 and D810 to form a 4.3V reference circuit, which provides a 4.3V reference voltage to the E pole of Q813. The B pole of Q813 is provided with a 5V sampling voltage by R811, and D811 is a 10V voltage regulator tube.