VIPER22-LED-EV データシートの表示（PDF） - STMicroelectronics

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VIPER22-LED-EV

Low power OFF-line SMPS primary switcher

STMicroelectronics 

Operations

VIPer22A-E, VIPer22ADIP-E, VIPer22AS-E

4.2

Wide range of VDD voltage

The VDD pin voltage range extends from 9 V to 38 V. This feature offers a great flexibility in

design to achieve various behaviors. In Figure 4 on page 7 a forward configuration has been

chosen to supply the device with two benefits:

● 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 (100 nF) 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 VDD 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 5. presents the internal current mode structure.

Figure 5. Internal current control structure

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Doc ID 12050 Rev 2

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