Datasheet

Operations VIPer22ADIP/ VIPer22AS - E
8/20 Rev1
■ 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
regulation up whatever the output voltage is.The V
DD
pin voltage may vary as much as
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
The Power MOSFET delivers a sense current I
s
which is proportional to the main current Id.
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=