SSC2016S datasheet(12/22 Pages) SANKEN

12 / 22 page

SSC2016S

SSC2016S - DSJ Rev.1.3

SANKEN ELECTRIC CO.,LTD.

Jul. 22, 2016

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

OSC

VOUT

GND

1.40V

/0.70V

OUT

DFW

ZCD

RCS

Figure 8-9.

ZCD Pin Peripheral Circuit

OUT pin voltage

Primary winding P

voltage, VP

Auxiliary winding D

voltage, VD 　

ZCD pin voltage

Drain to Source

voltage, VDS

Drain current, ID

Inductor current,

Turn-on point

Turn-on

delay time

VZCD(H)

VZCD(L)

Figure 8-10.

Zero Current Detection Waveform

tDLY

Bottom-on

Free oscillation

Delay time is short.

Make R1 or C6 value larger.

Delay time is Long.

Make R1 or C6 value smaller.

Proper delay time

Figure 8-11.

VDS Turn On Timing

8.6

Maximum Switching Frequency

Limitation Function

In the CRM operation, the switching frequency of a

power MOSFET is varied in a period of sinusoidal AC

input voltage. The switching frequency is lowest in the

peak of AC input voltage and is high as getting close to

the bottom of it. In addition, when output load decreases,

the switching frequency increases entirely. In order to

reduce the switching loss, the IC has the Maximum

Switching Frequency Limitation Function that limits the

switching frequency to fMAX of 300 kHz.

8.7

Overcurrent Protection (OCP)

Figure 8-12 shows the CS pin peripheral circuit and

internal circuit. The inductor current, IL is detected by

the detection resistor, RCS. The detection voltage, VRCS,

is fed into CS pin. As shown in Figure 8-12, the CS pin

is connected to capacitor-resistor filter (R5 and C5).

The IC has two Overcurrent Protection (OCP)

threshold voltages.

● OCP1

When VRCS increases VCS(OCP1) = 0.500 V or more, the

output

the

OUT

becomes

Low

pulse-by-pulse.

● OCP2

OCP2 is activated by malfunctions such as the short

of a boost diode, DFW. If the instantaneous large

current flows to a power MOSFET and the CS pin

voltage increases to VCS(OSP2) = 1.50 V or more and

this operation continues seven times, the output of

OUT pin is latched to low level.

Releasing the latched state is done by turning off the

input voltage and by dropping VCC pin voltage below

VCC(OFF).

VOUT

GND

OUT

DFW

RCS

VCS(OCP1)

= 0.500V

OCP1

VRCS

VCS(OCP2)

= 1.5V

OCP2

Figure 8-12.

The CS Pin Peripheral Circuit

and Internal Circuit.

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