AN2359

VIPerX2 description

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1

VIPerX2 description

The proposed converters are based on The VIPerX2A family, which is a range of smart

power devices with current mode PWM controller, start-up circuit and protections integrated

in a monolithic chip using VIPower M0 Technology.

The VIPerX2A family includes:

–

VIPer12, with a 0.4A peak drain current limitation and 730V breakdown voltage;

–

VIPer22, with a 0.7A peak drain current limitation and 730V breakdown voltage.

The switching frequency is internally fixed at 60kHz by the integrated oscillator of the

VIPerX2.

The internal control circuit offers the following benefits:

–

Large input voltage range on the V DD pin accommodates changes in supply

voltage;

–

Automatic burst mode in low load condition;

–

Overload protection in hiccup mode.

The feedback pin FB is sensitive to current and controls the operation of the device.

2

Output voltage selection

Two converters with different output voltage are introduced in this paper. The main

specifications are listed in Table 1.

This imposes, for the two solutions, a different design of the output inductor in terms of turns

ratio, i.e. n=1.4 for the –12V solution, against n=3.8 for the –24V solution (even if it could be

necessary to tune the turn ratio for proper output voltage).

Some disadvantage are related to the –12V solution:

–

The parasitic capacitance effect between the two windings is increased, compared

to the second one. This will bring about higher switching losses in turn-on (see

Figure 10. and Figure 11.) and, consequently, a worsening in terms of efficiency;

–

A higher voltage diode is needed to supply the VIPer;

–

Therefore, a –24V/-5V solution can be suitably used for all those applications where

efficiency and cost are important and, in general, in all the designs where a –24V output

voltage does not impact on the cost of the relays and drivers.

Table 1.

Proposed converters

Output 1

Output 2

-12V/150mA

-5V/300mA

3.3W

-24V/100mA

-5V/300mA

3.9W