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

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Doc ID 18376 Rev 1

         

In 

 the 5 V standby output voltage ripple has been captured during operation at 

115 Vac of the standby converter only. Ripple and noise measured at full load are very 
limited.

 shows the waveforms during the startup of the standby converter only, at 115 Vac 

and full load. At Viper27LN power-on the Vcc capacitor is charged by the internal startup 
current source until its voltage reaches the turn-on threshold. At this point the Viper27LN 
starts operating and the output voltage rises to reach the nominal value. During the 
converter startup, the Viper27LN internal digital fixed time-based (8.5 ms) soft-start 
gradually increases the drain current to its maximum value. In this way the stress on the 
secondary diode is considerably reduced and transformer saturation is prevented. The 
brownout circuit prevents the Viper27LN from starting up during abnormal mains conditions.

         

         

CH1: DRAIN (pin #8)
CH3: CONT (pin #3)

CH2: V

DD

 (pin #2)

CH4: FB (pin #4)

CH3: PIV D22

CH4: PIV D18

         

         

CH3: + 5 V standby ripple voltage

CH1: DRAIN (pin #8)

CH2: +5 V standby

CH3: BO (pin #5)

CH4: V

DD

 (pin #2)