FSFR1800HSL データシートの表示（PDF） - Unspecified

部品番号

コンポーネント説明

メーカー

FSFR1800HSL

FSFR-HS Series — Advanced Fairchild Power Switch (FPS™) for Half-Bridge Resonant Converters

Unspecified 

CFilter can be used to reduce some noise induced from

transformer or switching transition. Generally, hundreds

of pico-farad to tens of nano-farad is adequate,

depending on the quantity of noise.

The start and stop input-voltage can be calculated as:

Vdc−link ,STOP

=

VLINE

×

R1 + R2

R2

[V ]

(6)

Vdc−link,START = Vdc−link,STOP + I LINE × R1 [V ]

(7)

Cr

Np

Ns

Control

IC

VCS

CS

SG

PG

Rsense

IDS

Ns

I DS

V CS

Figure 27. Half-Wave Sensing

IDS

Figure 25. Half-Wave Sensing

7. Simple Remote-On/Off: The power stage can be

shutdown with optional Auto-Restart Mode, as shown in

Figure 26.

To configure an external protection with Auto-Restart

Mode, an opto-coupler and the LS pin are used. When

the voltage on the LS pin is pulled below VLINE (2.5 V),

the IC stops during the status holds. However, the opto-

coupler stops pulling down and the IC can perform the

auto-restart operation itself.

Figure 26. External Protection Circuits

8. Current-Sensing Methods: FSFR-HS series employs

negative voltage sensing to detect the drain current of

MOSFET, which allows a low-noise resistive sensing

using a filter with low time-constant and capacitive

sensing method.

8.1 Resistive Sensing Method: The IC can sense

drain current as a negative voltage, as shown in Figure

27 and Figure 28. Half-wave sensing allows low power

dissipation in the sensing resistor; while full-wave

sensing has less switching noise in the sensing signal.

For a time constant range for the filter, 3/100~1/10 of

the operating frequency is reasonable.

V CS

Control

IC

VCS

CS

Cr

Np

Ns

SG

PG

Rsense

Ns

IDS

Figure 28. Full-Wave Sensing

8.2 Capacitive Sensing Method: The drain current

can be sensed using an additional capacitor parallel

with the resonant capacitor, as shown in Figure 29.

During the low-side switch turn on, the current, iCB

through CB, makes VSENSE across RSENSE. The iCB is

scale-down of ip by the impedance ratio of Cr and CB.

Generally, 1/100~1/1000 is adequate for the ratio of CB

against Cr. RD is used as a damper for reducing noise

generated by switching transition. Several hundreds of

ohm to a few of kilo-ohms can be normally used.

VSENSE can be estimated as;

Vsense

=

I Cr

pk

CB

Cr

⋅

Rsense [V ]

(8)

© 2011 Fairchild Semiconductor Corporation

FSFR1800 / FSFR1700-HS • Rev.1.0.1

12

www.fairchildsemi.com

Share Link: