VIPER26

Power section

Doc ID 17736 Rev 2

13/25

7

Power section

The power section is implemented with an n-channel power MOSFET with a breakdown

a virtually lossless current sensing and the thermal sensor.

The gate driver of the power MOSFET is designed to supply a controlled gate current during

both turn-ON and turn-OFF in order to minimize common mode EMI. During UVLO

conditions, an internal pull-down circuit holds the gate low in order to ensure that the power

MOSFET cannot be turned ON accidentally.

8

High voltage current generator

The high voltage current generator is supplied by the DRAIN pin. At the first start up of the

converter, it is enabled when the voltage across the input bulk capacitor reaches the

high voltage current generator is turned OFF. The VIPer26 is powered by the external

source. After the start-up, the auxiliary winding or the diode connected to the output voltage

on page 6). During the switching, the internal current source is disabled and the

consumptions are minimized. In case of fault the switching is stopped and the device is self

see

Figure 22 on page 13.

Figure 22.

Power on and power off

I

DD

V

DD

V

DRAIN

V

DDon

time

V

IN

V

DRAIN_START

Power-on

Power-off

Normal operation

regulation is lost here

V

HV startup is no more activated

V

DDCSon

V

DDoff

I

DDch1

I

DDch2

time

time

time