Abstract
The VIPer12A is an integrated PWM and MOSFET
circuit for low power application in the 5W range,
typically in Cellular Phone Adapters. It is housed in
surface mount SO-8 and DIP8 packages.
With the availability of VIPer12A in SO-8 package
and the limited number of external components for
a real PWM operation, building a compact and
performant power supply becomes simple.
The travel adaptor design presented here, has
been made with the aim of minimising overall cost
for a secondary voltage and current regulated
adapter, topology widely used in Cellular Phone
Adapters.
The VIPer12A presents itself as the answer for
lower consumption in standby, like in home
appliances where it will be required to limit non
negligible "off the use" consumptions, as
recommended by the “European Commission of
Energy”. Today regulations demand less than 1
Watt. Thanks to VIPer12A low power consumption,
it is possible to achieve 100mW standby power in
a wide range of operations.

1.0 PRINCIPLE OF OPERATION
The circuit is a standard Flyback converter with
secondary current and voltage regulation driving
the VIPer12A feedback pin through an
optocoupler.

1.1 The VIPer12A
1.1.1 Start-up phase
VIPer12A, as any member of the VIPer family, has
an integrated high voltage current source to charge
C3 Vdd capacitor until it reaches its startup level
(15V). When Vdd gets to 15V, the VIPer switches,
supplied by the energy stored in C3, until it is
supplied through the auxiliary winding.
1.1.2 Auxiliary Supply
VIPer12A has a wide operating voltage range from
9V to 40V, respectively maximum and minimum
values for undervoltage and overvoltage
protections. This wide voltage supply range
simplifies the design of the VIPer12A supply but, to
ensure proper operation of the application in any
case, it is advised:
- in normal operation, to supply VIPer12A within its
operating range;
- in standby mode, to minimize auxiliary
consumption to achieve very low standby power;
- in short circuit, to limit output power by going into
an hiccup mode;
- in constant current mode, to ensure current
regulation below 2V before going into hiccup
mode.