SSC2016S datasheet(16/22 Pages) SANKEN

16 / 22 page

SSC2016S

SSC2016S - DSJ Rev.1.3

SANKEN ELECTRIC CO.,LTD.

Jul. 22, 2016

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

RCS is calculated using the following Equation (11),

where

Overcurrent

Protection

Threshold

Voltage

VCS(OCP) is 0.500 V and ILP is calculated using Equation

(5).

RCS≤�VCS(OCP)�ILP(Ω)

(11)

The loss PRCS at RCS is calculated by Equation (13)

using Equation (12).

IDRMS= 2√2×POUT

η×VACRMS(MIN)

×�16−4√2×VACRMS(MIN)

9×π×VOUT (A) (12)

PRCS=IDRMS2×RCS(W)

(13)

Where

IDRMS: RMS Drain current (A)

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

VOUT: Output voltage (V)

POUT: Output power (W)

η: Efficiency of PFC

The CR filter (R5 and C5) is connected to CS pin.

CR filter (R5 and C5) prevents IC from responding to

the drain current surge at MOSFET turn-on and avoids

the unstable operation of the IC.

R5 value of approximately 47

Ω is recommended,

since the CS Pin Source Current affects the accuracy of

OCP detection.

C5 value is reccommended to be calculated by using

following formula in which cut-off frequency of CR

filter (C5 and R5) is approximately 0.5 MHz to 3.0MHz.

C5= 1

2π×1×106×R5(F)

(14)

If R5 value is 47

Ω, C5 value is approximately

1000 pF to 6800 pF. C5 value should adjust based on

actual operation in application.

9.2.5

ZCD Pin Peripheral Circuit, R1 and

R1 is for the limiting of the input and output current

to ZCD pin. The value of resistor R1 is determined so

that the ZCD pin current is smaller than the absolute

maximum rating. The recommended value of ZCD pin

current is less than 3 mA.

The R1 value is chosen to satisfy both Equation (15)

and Equation (16). In addition, the bottom-on timing is

set by C6 and R1 (See Section 8.5).

1) Limiting of ZCD pin source current (at Q1 ON

state)

R1>√2×VACRMS(MAX)×NDNP

3×10−3(A) (Ω)

(15)

Where

VACRMS(MAX): Maximum AC input voltage rms value

(V)

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

ND: The number of turns of auxiliary winding D (turns)

2) Limiting of ZCD pin sink current (at Q1 OFF

state)

R1> VOUT×NDNP

3×10−3(A) (Ω)

(16)

Where

VOUT: Output voltage (V)

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

ND: The number of turns of auxiliary winding D (turns)

9.2.6

OUT Pin Peripheral Circuit (Gate

Drive Circuit)

The OUT pin is the gate drive output that can drive

the external power MOSFET directly.

The maximum output voltage of OUT pin is the VCC

pin voltage. The maximum current is −500 mA for

source and 1000 mA for sink, respectively.

R3 is for source current limiting. Both R2 and D1 are

for

sink

current

limiting.

The

values

these

components are adjusted to decrease the ringing of Gate

pin voltage and the EMI noise. The reference value is

several ohms to several dozen ohms.

R4 is used to prevent malfunctions due to steep dv/dt

at turn-off of the power MOSFET, and the resistor is

connected near the MOSFET, between the gate and

source. The reference value of R4

is from 10 kΩ to 100

kΩ. R2, R3, D1 and R4 are affected by the printed

circuit board trace layout and the power MOSFET

capacitance. Thus, the optimal values should be adjusted

under actual operation of the application.

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