FAN7532 Ver la hoja de datos (PDF) - Fairchild Semiconductor

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FAN7532

Ballast Control IC

Fairchild Semiconductor 

7. Protection Modes

The FAN7532 has two types of protection modes.

1) Over-Voltage Protection (OVP) Mode

The OVP pin is normally connected to the external

components that detect lamp voltage between a lamp’s

cathodes. This voltage is always maintained under 2V in

normal operation. If the lamp enters the end-lamp-life or

abnormal condition, the lamp does not turn-on even if

there is enough voltage supplied between two cathodes.

Normally, this condition means that one of the cathodes

is broken, deactivated, or the lamp is deeply blackened

around the cathodes. In this state, the ballast constantly

generates very high voltage between two cathodes to

ignite according to a specific procedure in the control IC.

When the voltage of OVP pin exceeds 2V, the IC

instantly enters the protection mode. To exit this mode,

the VCC must be recycled below the UVLO low

threshold.

VCC

15.6V

VUVLO+

VUVLO-

VCPH

5V

2.9V

FREQ

fPH

fOSC

OVP

VLAMP

Ignition fail

Ignition fail level

Preheating

Ignition Latched UVLO

shutdown

Preheating Ignition Run

Latched shutdown mode is removed

after VCC goes down to the UVLO-

FAN7532 Rev. 00

Figure 18. Timing Diagram (OVP Mode)

© 2006 Fairchild Semiconductor Corporation

FAN7532 Rev. 1.0.2

11

www.fairchildsemi.com

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