MS1003SH datasheet(22/41 Pages) SHINDENGEN

22 / 41 page

MS1003SH･MS1004SH

Application Note Ver.2.2

SHINDENGEN ELECTRIC MFG. CO. , LTD

22/41

5.4.1 Variables in formulas

The diagram to the right shows switching waveform models,

including numbers of troughs to skip and tq.

For other symbols, see Section 5.3 and the specification.

5.4.2 Formulas for obtaining trough skip start power

ON range

)

(

)

(

)

(

ip_start)

(bottom_sk

ton



















[s]

OFF range

ton

toff





ip_start)

(bottom_sk

[s]

Main SW device peak

current

ton





[A]

Trough skip start power

ip_start)

(bottom_sk

ton







[W]

If the trough skip start power obtained by the formulas above is greater than the trough skip end power

obtained in Section 5.4.3, the hysteresis is insufficient; redesign the transformer.

5.4.3 Formulas for obtaining trough skip end power

The trough skip function ends when either Condition 1 or Condition 2 is met. The trough skip end power

will be the “trough skip end power 1 of the formula 25 of Condition 1” or the “trough skip end power 2 of

the formula 30 or the trough skip end power 3 of the formula 34 of Condition 2,” whichever is smaller.

(Depending on the input voltage you want to calculate, compare either the trough skip end power 2 or 3 of

Condition 2 to trough skip end power 1.)

The chart below shows model curves of trough skip start and end power levels relative to input voltage.

Description

Symbol

Unit

DC input voltage setting

[V]

ON range under each condition

ton

[s]

OFF range under each condition

toff

[s]

Main SW device peak current under

each condition

IDP

[A]

Output power under each condition

[W]

Primary current detection resistance

R(ocl)

[Ω]

OCL pin auto burst threshold voltage

Vburst

[V]

OCL pin current detection threshold

voltage

Vth(ocl)

[V]

オフ幅

オン幅

動作周期

谷飛び0回

谷飛び1回

谷飛び2回

谷飛び0回

ｽｲｯﾁﾝｸﾞ波形ﾓﾃﾞﾙ図

Operating cycle

Switching waveform model

OFF range

ON range

Skipping no trough

Skipping

1 trough

Skipping

1 trough

Skipping no trough

Skipping

2 troughs

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