AN2929 datasheet(23/32 Pages) STMICROELECTRONICS

No. de pieza	AN2929

Descripción Electrónicos	In consumer applications such as LCD or plasma TVs

PDF	32 Pages

Scroll/Zoom	100%

Fabricante Electrónico	STMICROELECTRONICS [STMicroelectronics]

Página de inicio	http://www.st.com

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23 / 32 page

AN2929

Testing the board

Doc ID 15333 Rev 2

23/32

Figure 23.

2nd OCP tripping

In Figure 23 when the board was working in full-load condition with an input voltage of

115 VAC, the secondary winding was shorted. The short on the secondary winding leads to

a high drain current. After two switching cycles, the system stops and continuous running

with high currents in the primary as well as in the secondary windings and through the

power section of the VIPER27LN is avoided. Figure 24 shows the situation when a

permanent short-circuit is applied on the secondary windings. Most of the time the power

section of the VIPER27LN is off, eliminating any risk of overheating.

Figure 24.

Operating with secondary winding shorted - restart mode

Ch1 = VOUT

Ch2 = VFB

Ch4 = IDRAIN

Test condition:

Vin = 230VAC

Full load before

short

Ch3 = VDD

Ch4 = IDRAIN

Test condition

Vin=230VAC

Secondary winding

shorted

AN2929 Datasheet(PDF) 23 Page - STMicroelectronics