VIPER22ADIP-E Datasheet VIPER22AS-E, VIPER22ASTR-E, VIPER22ADIP-E | P7-P9

VIPer22A-E, VIPer22ADIP-E, VIPer22AS-E Operations

Doc ID 12050 Rev 2 7/21

4 Operations

4.1 Rectangular U-I output characteristics

Figure 4. Rectangular U-I output characteristics for battery charger

A complete regulation scheme can achieve combined and accurate output characteristics.

Figure 4. presents a secondary feedback through an optocoupler driven by a TSM101. This

device offers two operational amplifiers and a voltage reference, thus allowing the regulation

of both output voltage and current. An integrated OR function performs the combination of

the two resulting error signals, leading to a dual voltage and current limitation, known as a

rectangular output characteristic. This type of power supply is especially useful for battery

chargers where the output is mainly used in current mode, in order to deliver a defined

charging rate. The accurate voltage regulation is also convenient for Li-ion batteries which

require both modes of operation.

C10

Vref

Vcc

GND

TSM101

R10

ISO1

VDD DRAIN

SOURCE

CONTROL

VIPerX2A

AC IN

DCOUT

GND

Operations VIPer22A-E, VIPer22ADIP-E, VIPer22AS-E

8/21 Doc ID 12050 Rev 2

4.2 Wide range of V

voltage

The V

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 V

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

VIPer22A-E, VIPer22ADIP-E, VIPer22AS-E Operations

Doc ID 12050 Rev 2 9/21

The Power MOSFET delivers a sense current I

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 0.23 V. The MOSFET is switched off

when the following equation is reached:

By extracting I

Using the current sense ratio of the MOSFET G

The current limitation is obtained with the FB pin shorted to ground (V

= 0 V). This leads

to a negative current sourced by this pin, and expressed by:

By reporting this expression in the previous one, it is possible to obtain the drain current

limitation I

Dlim

In a real application, the FB pin is driven with an optocoupler as shown on Figure 5. which

acts as a pull up. So, it is not possible to really short this pin to ground and the above drain

current value is not achievable. Nevertheless, the capacitor C is averaging the voltage on

the FB pin, and when the optocoupler is off (start up or short circuit), it can be assumed that

the corresponding voltage is very close to 0 V.

For low drain currents, the formula (1) is valid as long as IFB satisfies I

< I

FBsd

, where

FBsd

is an internal threshold of the VIPer22A. If I

exceeds this threshold the device will

stop switching. This is represented on

Figure 12 on page 14, and I

FBsd

value is specified in the

PWM COMPARATOR SECTION. Actually, as soon as the drain current is about 12 % of

Idlim, that is to say 85 mA, the device will enter a burst mode operation by missing switching

cycles. This is especially important when the converter is lightly loaded.

+()⋅ 0.23V=

0.23V

--------------- - I

–=

⋅ G

0.23V

--------------- - I

–

⎝⎠

⎛⎞

⋅==

0.23V

--------------- -–=

Dlim

0.23V

------ -

------ -+

⎝⎠

⎛⎞

⋅⋅=

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P21

VIPER22ADIP-E

Mfr. #:

Buy VIPER22ADIP-E

Manufacturer:

STMicroelectronics

Description:

AC/DC Converters Low Power OFF-Line SMPS

Lifecycle:

New from this manufacturer.

Delivery:

DHL FedEx Ups TNT EMS

Payment:

T/T Paypal Visa MoneyGram Western Union

VIPER22ADIP-E

VIPER22ADIP-E

Products related to this Datasheet