TOP242-250
In addition to using a minimum number of components,
TOPSwitch-GX provides many technical advantages in this
type of application:
the switch and subsequent bouncing of the switch has no
effect. If necessary, the microprocessor could implement
the switch debouncing in software during turn-off, or a filter
capacitor can be used at the switch status input.
1. Extremely low power consumption in the off mode: 80 mW
typical at 110 VAC and 160 mW typical at 230 VAC. This
is because, in the remote OFF mode, the TOPSwitch-GX
consumes very little power and the external circuitry does
not consume any current (either M, Lor X pin is open) from
the high voltage DC input.
4. No external current limiting circuitry is needed for the
operation of the U4 optocoupler output due to internal
limiting of M pin current.
5. No high voltage resistors to the input DC voltage rail are
requiredtopowertheexternalcircuitryintheprimary. Even
the LED current for U3 can be derived from the CONTROL
pin. This not only saves components and simplifies layout,
but also eliminates the power loss associated with the high
voltage resistors in both ON and OFF states.
2. A very low cost, low voltage/current, momentary contact
switch can be used.
3. No debouncing circuitry for the momentary switch is
required. During turn-on, the start-up time of the power
supply (typically 10 ms to 20 ms) plus the microprocessor
initiation time act as a debouncing filter, allowing a turn-on
only if the switch is depressed firmly for at least the above
delay time. During turn-off, the microprocessor initiates
the shutdown sequence when it detects the first closure of
6. Robust design: There is no ON/OFF latch that can be
accidentally triggered by transients. Instead, the power
supply is held in the ON-state through the secondary-side
microprocessor.
M
12/04
25
POWERINT [ Power Integrations ]
