FSQ510 datasheet(9/15 Pages) FAIRCHILD

Part #	FSQ510

Description	Green Mode Fairchild Power Switch

Download	15 Pages

Scroll/Zoom	100%

Manufacturer	FAIRCHILD [Fairchild Semiconductor]

Direct Link	http://www.fairchildsemi.com

Logo

9 / 15 page

www.fairchildsemi.com

FSQ510, FSQ510H, and FSQ510M • Rev. 1.3.0

9

Functional Description

1. Startup:

At startup, an internal high-voltage current

source supplies the internal bias and charges the

external capacitor (Ca) connected to the VCC pin, as

illustrated in Figure 13. When VCC reaches 8.7V, the

FPS begins switching and the internal high-voltage

current source is disabled. The FPS continues normal

switching operation and the power is supplied from the

auxiliary transformer winding unless VCC goes below the

stop voltage of 6.7V.

6.7V/

8.7V

5

V

ref

Internal

Bias

V

CC

8

V

str

I

CH

V

CC good

V

DC

C

a

Figure 13. Startup Block

2. Feedback Control

: This device employs current-

mode control, as shown in Figure 14. An opto-coupler

(such as the FOD817) and shunt regulator (such as the

KA431) are typically used to implement the feedback

network. Comparing the feedback voltage with the

voltage across the Rsense resistor makes it possible to

control the switching duty cycle. When the reference pin

voltage of the shunt regulator exceeds the internal

reference voltage of 2.5V, the opto-coupler LED current

increases, pulling down the feedback voltage and

reducing the drain current. This typically occurs when the

input voltage is increased or the output load is decreased.

2.1 Pulse-by-Pulse Current Limit

: Because current-

mode control is employed, the peak current through the

SenseFET is limited by the inverting input of PWM

comparator (VFB*), as shown in Figure 14. Assuming

that the 225µA current source flows only through the

internal resistor (6R + R=12.6k

Ω), the cathode voltage

of diode D2 is about 2.8V. Since D1 is blocked when

the feedback voltage (VFB) exceeds 2.8V, the maximum

voltage of the cathode of D2 is clamped at this voltage,

clamping VFB*. Therefore, the peak value of the current

through the SenseFET is limited.

2.2 Leading-Edge Blanking (LEB)

: At the instant the

internal SenseFET is turned on, a high-current spike

usually occurs through the SenseFET, caused by

primary-side capacitance and secondary-side rectifier

reverse recovery. Excessive voltage across the Rsense

resistor would lead to incorrect feedback operation in

the current mode VS-PWM control. To counter this

effect, the FPS employs a leading-edge blanking

(LEB) circuit to inhibit the VS-PWM comparator for a

short time (tLEB) after the SenseFET is turned on.

OSC

V

ref

I

delay

I

FB

VSD

R

6R

Gate

driver

OLP

D1

D2

+

V

fb

*

-

V

fb

KA431

OB

V

O

FOD817

R

sense

SenseFET

V

ref

VS signal

3

Figure 14. Valley Switching Pulse-Width

Modulation (VS-PWM) Circuit

3. Synchronization

: The FSQ510 (H or M) employs a

valley-switching technique to minimize the switching

noise and loss. The basic waveforms of the valley

switching converter are shown in Figure 15. To

minimize the MOSFET switching loss, the MOSFET

should be turned on when the drain voltage reaches its

minimum value, as shown in Figure 15. The minimum

drain voltage is indirectly detected by monitoring the

V

B

CC

B

winding voltage, as shown in Figure 15.

V

DC

V

RO

V

RO

V

DS

t

F

0.7V

V

Sync

200ns Delay

0.1V

MOSFET

Gate

ON

Figure 15. Valley Switching Waveforms

Similar Part No. - FSQ510

Manufacturer	Part #	Datasheet	Description
Fairchild Semiconductor	FSQ510	707Kb / 15P	Green Mode Fairchild Power Switch (FPS) for Quasi-Resonant Converter - Low EMI and High Efficiency
	FSQ510	534Kb / 15P	Green Mode Fairchild Power Switch (FPS) for Valley Switching Converter - Low EMI and High Efficiency
	FSQ510	1Mb / 14P	Green Mode Fairchild Power Switch (FPS) for Valley Switching Converter - Low EMI and High Efficiency
	FSQ510H	707Kb / 15P	Green Mode Fairchild Power Switch (FPS) for Quasi-Resonant Converter - Low EMI and High Efficiency
	FSQ510H	534Kb / 15P	Green Mode Fairchild Power Switch (FPS) for Valley Switching Converter - Low EMI and High Efficiency

More results

Similar Description - FSQ510

Manufacturer	Part #	Datasheet	Description
Fairchild Semiconductor	FSCM0465R	450Kb / 20P	Green Mode Fairchild Power Switch
	FSQ100	741Kb / 12P	Green Mode Fairchild Power Switch
	FSL127H	1Mb / 15P	Green Mode Fairchild Power Switch
	FSQ0765RQ	3Mb / 19P	Green-Mode Fairchild Power Switch
	FSDM0465RE	519Kb / 21P	Green Mode Fairchild Power Switch
	FSDH321	510Kb / 20P	Green Mode Fairchild Power Switch
	FSBH0170	944Kb / 16P	Green Mode Fairchild Power Switch
	FSBH0F70A	801Kb / 16P	Green Mode Fairchild Power Switch
	FSGM0465RB	927Kb / 18P	Green-Mode Fairchild Power Switch
	FSGM0765R	823Kb / 18P	Green-Mode Fairchild Power Switch
	FSL137H	1Mb / 15P	Green Mode Fairchild Power Switch

More results

FSQ510 Datasheet(PDF) 9 Page - Fairchild Semiconductor

FSQ510 Datasheet(HTML) 9 Page - Fairchild Semiconductor

Similar Part No. - FSQ510

Similar Description - FSQ510

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

Datasheet Download

Link URL