FSFR2000 Просмотр технического описания (PDF) - Fairchild Semiconductor

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FSFR2000

Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converter

Fairchild Semiconductor 

5.3 Overload Protection (OLP): Overload is defined as

the load current exceeding its normal level due to an

unexpected abnormal event. In this situation, the

protection circuit should trigger to protect the power

supply. However, even when the power supply is in the

normal condition, the overload situation can occur during

the load transition. To avoid premature triggering of

protection, the overload protection circuit should be

designed to trigger only after a specified time to

determine whether it is a transient situation or a true

overload situation. Figure 27 shows a typical overload

protection circuit. By sensing the resonant capacitor

voltage on the control pin, the overload protection can be

implemented. Using RC time constant, shutdown delay

can be also introduced. The voltage obtained on the

control pin is given as:

VCON

=

2(CB

CB

+ Csense

)

VCr

p

−

p

(7)

where VCrp-p is the amplitude of the resonant capacitor

voltage.

5.4 Over-Voltage Protection (OVP): When the LVcc

reaches 23V, OVP is triggered. This protection is used

when auxiliary winding of the transformer to supply VCC

to FPS is utilized.

5.5 Thermal Shutdown (TSD): The MOSFETs and the

control IC in one package makes it easy for the control

IC to detect the abnormal over-temperature of the

MOSFETs. If the temperature exceeds approximately

130°C, the thermal shutdown triggers.

© 2007 Fairchild Semiconductor Corporation

FSFR2100 • 1.0.0

12

www.fairchildsemi.com

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