Техническая Спецификация для STMicroelectronics 170 W power supply with PFC and standby supply for flat TV using the L6564, L6599A, and Viper27LN EVL EVL170W-FTV

Doc ID 18376 Rev 1

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 and 

 show the OVP response, observed opening the resonant stage feedback 

loop. Upon an overvoltage condition of either 24 V or 12 V output, the Zener diodes D16 and 
D17 are reverse-biased and conduct respectively, forcing Q10 on by the resulting base 
current, which causes Q9 to conduct shorting to ground the anode of the U5 optocoupler 
and the disappearance of V_C44. Therefore, the L6564 and the L6599A are not powered. 
The two transistors mentioned form a pnp-npn SCR structure that force the PFC and 
resonant converter to be latched off until the 5 V standby is removed by a mains voltage 
recycling. In the case of an open loop event, the 12 V and 24 V outputs reach 14.16 V and 
28.26 V respectively.

         

         

CH3: 24 V output

CH1: On/off signal

CH2: CSS (pin #1)
CH4: 12 V output

CH3: V_C44

CH1: HB voltage

CH2: PFC drain
CH4: On/off signal

         

         

CH3: V_C53

CH1: HB voltage

CH2: PFC drain
CH4: V_C44

CH3: V_C53

CH1: 24 V output

CH2: 12 V output
CH4: V_C44