TOP244PN View Datasheet(PDF) - Power Integrations, Inc

Part Name

Description

Manufacturer

TOP244PN

TOPSwitch-GX Family Extended Power, Design Flexible, EcoSmart, Integrated Off-line Switcher

Power Integrations, Inc 

TOP242-250

Processor Controlled Supply Turn On/Off

A low cost momentary contact switch can be used to turn

the TOPSwitch-GX power on and off under microprocessor

control, which may be required in some applications such as

printers. The low power remote OFF feature allows an

elegant implementation of this function with very few external

components, as shown in Figure 45. Whenever the push

button momentary contact switch P1 is closed by the user, the

optocoupler U3 is activated to inform the microprocessor of

this action. Initially, when the power supply is off (M pin is

floating), closing of P1 turns the power supply on by shorting

the M pin of the TOPSwitch-GX to SOURCE through a diode

(remote ON). When the secondary output voltage VCC is

established, the microprocessor comes alive and recognizes that

the switch P1 is closed through the switch status input that is

driven by the optocoupler U3 output. The microprocessor then

sends a power supply control signal to hold the power supply

in the on-state through the optocoupler U4. If the user presses

the switch P1 again to command a turn off, the microprocessor

detects this through the optocoupler U3 and initiates a shutdown

procedure that is product specific. For example, in the case of

the inkjet printer, the shutdown procedure may include safely

parking the print heads in the storage position. In the case of

products with a disk drive, the shutdown procedure may include

saving data or settings to the disk. After the shutdown procedure

is complete, when it is safe to turn off the power supply, the

microprocessor releases the M pin by turning the optocoupler

U4 off. If the manual switch and the optocouplers U3 and U4

are not located close to the M pin, a capacitor CM may be needed

to prevent noise coupling to the pin when it is open.

The power supply could also be turned on remotely through

a local area network or a parallel or serial port by driving the

optocoupler U4 input LED with a logic signal. Sometimes it is

easier to send a train of logic pulses through a cable (due to AC

coupling of cable, for example) instead of a DC logic level as

a wake up signal. In this case, a simple RC filter can be used

to generate a DC level to drive U4 (not shown in Figure 45).

This remote on feature can be used to wake up peripherals

such as printers, scanners, external modems, disk drives, etc.,

as needed from a computer. Peripherals are usually designed

to turn off automatically if they are not being used for a period

of time, to save power.

+

High Voltage

DC Input

27 kΩ

1N4148

U4

U3

DM

TOPSwitch-GX

CONTROL

C

CM S

P1 1 nF

F U1

47 µF

Figure 45. Remote ON/OFF using Microcontroller.

VCC

(+5 V)

External

Wake-up

Signal

MICRO-

Power

100 kΩ

PROCESSOR/ Supply

CONTROLLER ON/OFF

U2

Control

LOGIC LOGIC

INPUT OUTPUT

1N4148

6.8 kΩ

U3

P1 Switch

LTV817A Status

6.8 kΩ

U4

LTV817A

RETURN

PI-2561-081204

24 M

12/04

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