Operations

VIPer22ADIP/ VIPer22AS - E

8/20

Rev1

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As soon as the device starts switching, it immediately receives some energy from the

auxiliary winding. C5 can be therefore reduced and a small ceramic chip (100nF) is

sufficient to insure the filtering function. The total start up time from the switch on of input

voltage to output voltage presence is dramatically decreased.

■

The output current characteristic can be maintained even with very low or zero output

voltage. Since the TSM101 is also supplied in forward mode, it keeps the current

the input voltage, that is to say with a ratio of about 4 for a wide range application.

4.3

Feedback Pin Principle of Operation

A feedback pin controls the operation of the device. Unlike conventional PWM control

circuits which use a voltage input (the inverted input of an operational amplifier), the FB pin

is sensitive to current. Figure 4. presents the internal current mode structure.

Figure 4.

Internal current control structure

R2 receives this current and the current coming from the FB pin. The voltage across R2 is

then compared to a fixed reference voltage of about 0.23V. The MOSFET is switched off

when the following equation is reached:

R

2

I

S

I

FB

+

()

⋅

0.23V

=