FSFR1600 データシートの表示（PDF） - Fairchild Semiconductor

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FSFR1600

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

Fairchild Semiconductor 

Cr

Np

Ns

Control

IC

VCS

CS

SG

PG

Rsense

Ids

Ns

Ids

VCS

Figure 24. Half-Wave Sensing

Ids

VCS

Control

IC

VCS

CS

Cr

Np

Ns

SG

PG

Rsense

Ns

Ids

Figure 25. Full-Wave Sensing

Current Sensing Using Resonant Capacitor Voltage:

For high-power applications, current sensing using a

resistor may not be available due to the severe power

dissipation in the resistor. In that case, indirect current

sensing using the resonant capacitor voltage can be a

good alternative because the amplitude of the resonant

capacitor voltage (Vcrp-p) is proportional to the resonant

current in the primary side (Ipp-p) as:

V p−p

Cr

=

I p− p

p

2π fsCr

(6)

To minimize power dissipation, a capacitive voltage

divider is generally used for capacitor voltage sensing, as

shown in Figure 26.

Ip

VCr

VCrp-p

Vsense

V pk

sense

=

CB

V p− p

Cr

Csense + CB

V pk

sense

2

= VCON

VCON

Tdelay = Rd Cd

Vsensepk

Vsensepk

Figure 26. Current Sensing Using Resonant

Capacitor Voltage

5. Protection Circuits: The FSFR-series has several

self-protective functions, such as Overload Protection

(OLP), Over-Current Protection (OCP), Abnormal Over-

Current Protection (AOCP), Over-Voltage Protection

(OVP), and Thermal Shutdown (TSD). OLP, OCP, and

OVP are auto-restart mode protections; while AOCP and

TSD are latch-mode protections, as shown in Figure 27.

Auto-restart Mode Protection: Once a fault condition is

detected, switching is terminated and the MOSFETs

remain off. When LVCC falls to the LVCC stop voltage of

11.3V, the protection is reset. The FPS resumes normal

operation when LVCC reaches the start voltage of 14.5V.

© 2007 Fairchild Semiconductor Corporation

FSFR series Rev.1.0.9

12

www.fairchildsemi.com

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