MS1003SH datasheet(27/41 Pages) SHINDENGEN

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MS1003SH･MS1004SH

Application Note Ver.2.2

SHINDENGEN ELECTRIC MFG. CO. , LTD

27/41

5.5 Pin design

5.5.1 Design procedure for the Z/C pin (Pin 1)

The operating mode switching circuit described in this section incorporates a photocoupler that receives

signals from the secondary side. For the secondary circuit configuration, see 6. Example circuit diagram.

(1) Basic circuit

This is the simplest circuit configuration for

designs requiring only normal mode. Since

auto burst mode is available, it is the easiest

design for a power supply featuring standby

mode.

(2) Circuit for using super standby mode

The diagram to the right shows the basic

circuit for using super standby mode. A

photocoupler is added to switch the Z/C pin

between high and low levels. If the

photocoupler activates, the circuit operates in

normal mode. If the photocoupler deactivates,

the circuit operates in super standby mode.

The photocoupler current must be carefully set so that the Z/C pin voltage falls sufficiently low.

 Protection for this circuit configuration

Protect with a zener diode if the insulation

appears likely to break down between the

photocoupler PH102 and the primary or

secondary side, as shown to the right.

(3) Circuit for operating the photocoupler at low

current

This circuit uses less power to operate the

PH102 in auto burst mode, thereby slightly

enhancing efficiency in auto burst mode

compared to circuit (2).

C108

R106

R105

D102

PH102

DZ301

MS1003SH

MS1004SH

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