SSC9522S datasheet(13/21 Pages) SANKEN

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SSC9522S

SSC9522S - DSE Rev.1.3

SANKEN ELECTRIC CO.,LTD.

Jan.07, 2016

http://www.sanken-ele.co.jp/en

8.3

Soft Start Function

Figure 8-15 shows the waveform of the CSS pin in the

startup operation.

The IC has Soft Start Function to reduce stress of

peripheral component and prevent the capacitive mode

operation. During the soft start operation, C6 connected

to the CSS pin is charged by the CSS Pin Charge

Current, ICSS(C) = − 0.18 mA. The oscillation frequency is

varied by the CSS pin voltage. The oscillation frequency

becomes gradually low with the increasing CSS pin

voltage. At same time, output power increases. When

the output voltage increases, the IC is operated with an

oscillation frequency controlled by feedback.

If the overcurrent protection activates as soon as the

IC starts and the CSS pin voltage is under the CSS Pin

Threshold Voltage (2), VCSS(2) = 0.59 V, the IC stops

switching operation. Since the period of the high peak

current of primary windings becomes short, the stress of

peripheral components is reduced.

When the IC becomes any of the following conditions,

C6 is discharged by the CSS Pin Reset Current,

ICSS(R) = 1.8 mA.

● VCC pin voltage ≤ V

CC(OFF)= 9.8 V

● VSEN pin voltage ≤ V

SEN(OFF)= 1.16 V

● When the latched shutdown is operated by External

Latched Shutdown Function or some protection (OVP,

OLP and TSD)

time

CSS pin

voltage

time

Soft start

peropd

OCP

operation

period

Oscillation frequency is

controlled by feedback current

Primary

winding

current

C6 is charged by -0.18mA

About 5.5V

VCSS(2)=0.59V

Limited by

OCP

Figure 8-15 Soft start operation waveforms

8.4

High-side Driver

Figure 8-16 shows a bootstrap circuit. The bootstrap

circuit is for driving to Q(H) and is made by D1, R8 and

C10 between the REG pin and the VS pin.

When Q(H) is OFF state and Q(L) is ON state, the VS

pin voltage becomes about ground level and C10 is

charged from the REG pin.

When the voltage of between the VB pin and the VS

pin, VB-S, increases to VBUV(ON) = 7.3 V or more, an

internal high-side drive circuit starts operation. When

VB-S decreases to VBUV(OFF) = 6.4 V or less, its drive

circuit stops operation.

In case the both ends of C10 are short, the IC is

protected by VBUV(OFF).

D1 should use a fast recovery diode that is short

recovery time and low leakage current.

AG01A

(Vrm = 600 V, Sanken product) is recommended when

the maximum input voltage is 265V AC.

C10 should use film or ceramic capacitor that is the

low ESR and the low leakage current.

C10

VGL

VGH

COM

REG

GND

Bootstrap circuit

High- side

Driver

Q(H)

Q(L)

Figure 8-16 Bootstrap circuit

8.5

Constant Output Voltage Control

Figure 8-17 shows the FB pin peripheral circuit. The

FB pin is sunk the feedback current by the photo-coupler,

PC1, connected to FB pin. As a result, since the

oscillation frequency is controlled by the FB pin, the

output voltage is controlled to constant voltage (in

inductance area).

When the FB pin current decreases to the FB Pin

Source current at Burst Mode Start, ICONT(1) = − 2.5 mA

or less at light load, the IC stops switching operation.

This operation reduces switching loss, and prevents the

increasing of the secondary output

voltage. The

photo-coupler

the

secondary

side

should

considered about the secular change of CTR and its

current ability for control should be set ICONT(2) = − 3.7

mA (min.) or less. The recommend value of R6 is

560 Ω.

GND

PC1

Figure 8-17 FB pin peripheral circuit

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