SSC2006SA datasheet(13/23 Pages) SANKEN

13 / 23 page

SSC2006SA

SSC2006SA - DSJ Rev.1.6

SANKEN ELECTRIC CO.,LTD.

Aug.11, 2015

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

frequency becomes higher with lowering the input

voltage. The frequency at the peak of the AC line

waveform, fSW(SET) should be set more than frequency

of 20 kHz.

The tON(SET)MAX at fSW(SET) is calculated by Equation

(4). The tON(MAX) described in “8.4 Maximmum

on-time setting” should be set above tON(SET)MAX.

OUT

)

SET

(

)

MIN

(

ACRMS

OUT

MAX

)

SET

(







(s)

(4)

where,

VOUT : Output voltage (V)

VACRMS(MIN) : Maximum AC input voltage rms value (V)

3) Inductance, LP

Substituting both minimum and maximum of AC

input voltage to VACRMS, choose a smaller one as LP

value. LP is calculated as follows:









OUT

)

SET

(

OUT

ACRMS

OUT

ACRMS











(H)

(5)

where,

VACRMS: Maximum or minimum AC input voltage rms

value (V)

POUT: Output Power (W)

fSW(SET): Minimum operational frequency at the peak

of the AC line waveform (kHz)

η: Efficiency of PFC

(In general, the range of η is 0.90 to 0.97, depending

on on-resistance of power MOSFET RDS(ON) and

forward voltage drop of rectifier diode VF.)

4) Inductor peak current, ILP

ILP is peak current at the minimum of AC input

voltage waveform. ILP calculated as follows:

)

MIN

(

ACRMS

OUT









(A)

(6)

9.1.2

Auxiliary Winding D

Figure 9-1 shows the polarity of boost winding P and

auxiliary winding D.

Given the number of windings of each winding as NP

and ND, the turn ratio ND/NP is set satisfying following

conditions. The condition of ND/NP making ZCD pin

voltage above VZCD(H) = 1.5 V after power MOSFET

turns off is expressed as follows:

)

MAX

(

ACRMS

OUT

)

(

ZCD







(7)

where,

NP: The number of turns of boost winding P (turns)

ND: The number of turns of auxiliary winding D

(turns)

VOUT: Output voltage (V)

VACRMS(MAX): Maximum AC input voltage rms value

(turns)

VOUT

GND

OUT

DFW

ZCD

RRT

RCS

Figure 9-1 ZCD Peripheral circuit

When power supply of VCC pin is suplied from

auxiliary winding as shown in Figure 9-2, the condition

of ND/NP is necessary to satisfy both Equation (7) and

following Equation (11).

DVCC

RCS

RST

VCC

GND

CVCC

CCP

DZVCC

DFW

VOUT

LINE

GND

VAC

VIN

VFVCC

VFZVCC

VFFW

Figure 9-2 VCC pin peripheral circuit

(Power supply from auxiliary winding)

When switching operation starts, the current is

supplied by auxiliary winding as follows:

Auxiliary winding voltage in ON state and OFF state

of Q1 are given as VB and VD, respectively. The forward

voltages of Diode (DZVCC and DVCC) are given as VFZVCC

and VFVCC.

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