Hitachi np8c switching power supply circuit diagram

As shown in FIG Hitachi np8c switching power supply circuit, Hitachi NP8C power models are: Hitachi CTP236, CEP320D, CRP350D, 450D, Furi HFC-236,450, Venus C37-401, C46-1, C563
Hitachi np8c switching power supply circuit diagram - schematic

, etc., the Chinas color TV power supply in the early and wide application. Oscillation 300V DC voltage by R911, R907, R908 is added to the B pole switch Q901, Q901 begins to conduct, T901 primary winding current starts to flow through, while the induced voltage on the positive polarity is negative, so this winding also induced voltage, with positive and negative polarity is lower, the voltage through R902, R909, C908 to Q901 B pole, so that further Q901 is turned on, a strong positive feedback Q901 rapid saturation. During Q901 saturated, D906, D907 off, T901 stored energy, while the positive feedback voltage to the C908 constantly charged with the C908 has been continuously charged, Q901 B-voltage falling, can not be maintained until saturation Q901, Q901 will be out of saturation. Q901 Once out of saturation, T901 each winding induced voltage polarity reversal of all, but also a strong positive feedback Q901 rapidly closing. During Q901 off, D906, D907 conduction, based on the C909, C910 108V and 54V DC voltage, and turned D905, C908 through R902, R909, T901 feedback windings discharge circuit, at the same time, 300V voltage by R911, R907, R908 reverse charging to C908, so B voltage Q901 continues to rise until the Q901 is turned on again, then go to the next oscillation. Regulator circuit Regulator circuit consists CP901, Q902, Q903 composition. CP901 (4) feet for the Q902s E pole reference voltage, the size of the output voltage can affect the level of conduction of Q902, Q903 thus affecting the conductivity of the same level, which can control the oscillation frequency Q901, also stabilized output voltage size. In addition, Q901 oscillation frequency is also affected by the line frequency control, the right line flyback pulse C912 introduced by the line frequency to control the oscillation frequency of the Q901, it is possible to obtain a stable output voltage.

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