STR-A6000MZ datasheet(16/26 Pages) SANKEN

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STR-A6000MZ/HZ Series

STR-A6000MZ/HZ - DS Rev.1.2

SANKEN ELECTRIC CO.,LTD.

Mar.13, 2015

Neglecting the effect of input resistance is zero, the

reference effective value of AC input voltage when the

Brown-In and Brown-Out Function is activated is

calculated as follows:





















)

(

RMS

)

(

(5)

where,

VAC(OP)RMS : The effective value of AC input voltage

when the Brown-In and Brown-Out

Function is activated

VBR(TH)

: Any one of threshold voltage of the BR

pin (see Table 9-1)

RA, RB, RC and C4 should be selected based on actual

operation in the application.

9.10 Overcurrent Protection (OCP)

Overcurrent Protection (OCP) detects each drain peak

current level of a power MOSFET on pulse-by-pulse

basis, and limits the output power when the current level

reaches to OCP threshold voltage.

During the Leading Edge Blanking Time, the OCP

threshold voltage becomes VOCP(LEB) = 1.69 V which is

higher than the normal OCP threshold voltage as shown

in Figure 9-14. Changing to this threshold voltage

prevents the IC from responding to the surge voltage in

turning-on the power MOSFET. This function operates

as protection at the condition such as output windings

shorted or unusual withstand voltage of secondary-side

rectifier diodes.

When the power MOSFET turns on, the surge voltage

width of the S/OCP pin should be less than tBW, as shown

in Figure 9-14. In order to prevent surge voltage, pay

extra attention to ROCP trace layout (refer to Section

10.2).

In addition, if a C (RC) damper snubber of Figure 9-15

is used, reduce the capacitor value of damper snubber.

Surge pulse voltage width at turning-on

tBW

VOCP(LEB)

VOCP’

Figure 9-14 S/OCP pin voltage

D51

ROCP

C51

C（RC）

Damper snubber

7, 8

D/ST

S/OCP

C（RC）

Damper snubber

Figure 9-15 Damper snubber

< Input Compensation Function >

ICs with PWM control usually have some propagation

delay time. The steeper the slope of the actual drain

current at a high AC input voltage is, the larger the

detection voltage of actual drain peak current is,

compared to VOCP. Thus, the peak current has some

variation depending on the AC input voltage in OCP

state. In order to reduce the variation of peak current in

OCP

state,

the

incorporates

built-in

Input

Compensation

Function.

The

Input

Compensation

Function is the function of correction of the OCP

threshold voltage depending with AC input voltage, as

shown in Figure 9-16.

When AC input voltage is low (ON Duty is broad), the

OCP threshold voltage is controlled to become high. The

difference of peak drain current become small compared

with the case where the AC input voltage is high (ON

Duty is narrow).

ON Duty (%)

DDPC=36%

VOCP(L)

DMAX=75%

100

VOCP(H)

0.5

1.0

Figure 9-16 Relationship between ON Duty and Drain

Current Limit after compensation

The compensation signal depends on ON Duty. The

relation between the ON Duty and the OCP threshold

voltage after compensation VOCP' is expressed as

Equation (6). When ON Duty is broader than 36 %, the

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