LNK501P datasheet(6/20 Pages) POWERINT

Part #	LNK501P

Description	LinkSwitch Family Energy Efficient, CV/CC Switcher for Very Low Cost Chargers and Adapters

Download	20 Pages

Scroll/Zoom	100%

Manufacturer	POWERINT [Power Integrations, Inc.]

Direct Link	http://www.powerint.com

Logo

6 / 20 page

6 I2/05

LNK501

However, in laboratory bench tests, it is often more convenient

to test the power supply output characteristic starting from a

low output current and gradually increasing the load. In this

case,theoptocouplerfeedbackregulatestheoutputvoltageuntil

the peak output power curve is reached as shown in Figure 8.

Under these conditions, the output current will continue to rise

until the peak power point is reached and the optocoupler turns

off. Once the optocoupler is off, the CONTROL pin feedback

current is determined only by R1 and R3 and the output current

therefore folds back to the inherent CC characteristic as shown.

Since this type of load transition does not normally occur in a

batterycharger,theoutputcurrentneverovershootstheinherent

constant current value in the actual application.

In some applications it may be necessary to avoid any output

currentovershoot,independentofthedirectionof loadvariation.

To achieve this goal, the minimum voltage feedback threshold

should be set at V

O(MAX). This will ensure that the voltage at the

CC to CV transition point of the inherent characteristic will

alwaysoccurbelowthevoltagefeedbackthreshold.However,the

outputvoltagetoleranceisthenincreased,sincetheinherentCV

characteristic tolerance below V

O(MAX) is added to the tolerance

of the optocoupler feedback circuit.

Applications Example

The circuit shown in Figure 9 shows a typical implementation

of an approximate constant voltage / constant current (CV/CC)

charger using LinkSwitch. This design delivers 2.75 W with

a nominal peak power point voltage of 5.5 V and a current of

500 mA. Efﬁciency is greater than 70% over an input range

of 85 VAC to 265 VAC.

The bridge rectiﬁer, BR1, rectiﬁes the AC input. Resistor RF1

is a fusible type providing protection from primary side short

circuits. The rectiﬁed AC is smoothed by C1 and C2 with

inductor L1 forming a pi-ﬁlter in conjunction with C1 and C2

to ﬁlter conducted EMI. The switching frequency of 42 kHz

allows such a simple EMI ﬁlter to be used without the need for

a Y capacitor while still meeting international EMI standards.

When power is applied, high voltage DC appears at the DRAIN

pin of LinkSwitch (U1). The CONTROL pin capacitor C3 is

then charged through a switched high voltage current source

connected internally between the DRAIN and CONTROL pins.

When the CONTROL pin reaches approximately 5.6 V relative

to theSOURCEpin,the internalcurrent source is turned off. The

internalcontrolcircuitryisactivatedandthehighvoltageMOSFET

starts to switch, using the energy in C3 to power the IC.

When the MOSFETis on, the high voltage DC bus is connected

to one end of the transformer primary, the other end being

connected to primary return. As the current ramps in the

primary of ﬂyback transformer T1, energy is stored. This

energy is delivered to the output when the MOSFET turns off

each switching cycle.

The secondary of the transformer is rectiﬁed and ﬁltered by D6

and C5 to provide the DC output to the load.

LinkSwitch

dramatically simpliﬁes the secondary side by

controllingboththeconstantvoltageandconstantcurrentregions

entirely from the primary side. This is achieved by monitoring

the primary-side V

OR (voltage output reﬂected).

Diode D5 and capacitor C4 form the primary clamp network.

Thisbothlimitsthepeakdrainvoltageduetoleakageinductance

and provides a voltage across C4, which is equal to the V

OR plus

an error due to the parasitic leakage inductance. Resistor R2

ﬁlters the leakage inductance spike and reduces the error in the

valueoftheV

OR. Resistor R1 converts this voltage into a current

that is fed into the CONTROL pin to regulate the output.

During CV operation the output is regulated through control of

the duty cycle. As the current into the CONTROL pin exceeds

approximately 2 mA, the duty cycle begins to reduce, reaching

30% at a CONTROL pin current of 2.3 mA.

Under light or no-load conditions, when the duty cycle reaches

approximately 4%, the switching frequency is reduced to lower

energy consumption.

If the output load is increased beyond the peak power point

(deﬁned by 0.5·L

P·ILIM

2

·f), the output voltage and V

OR falls.

The reduced CONTROL pin current will lower the internal

LinkSwitch

current limit (current limit control) providing an

approximately constant current output characteristic. If the

load is increased and the CONTROL pin current falls below

approximately 1 mA, the CONTROL pin capacitor C3 will

discharge and the supply enters auto-restart.

Current limit control removes the need for any secondary side

current sensing components (sense resistor, transistor, opto

coupler and associated components). Removing the secondary

sense circuit dramatically improves efﬁciency, giving the

associated beneﬁt of reduced enclosure size.

Key Application Considerations

Design Output Power

Table 1 (front page) shows the maximum continuous output

power that can be obtained under the following conditions:

1. The minimum DC input bus voltage is 90 V or higher.

This corresponds to a ﬁlter capacitor of 3 µF/W for

universal input and 1 µF/W for 230 VAC or 115 VAC

input with doubler input stage.

2. Design is a discontinuous mode ﬂyback converter, with

nominal primary inductance value and a V

OR in the range

40 V to 60 V. Continuous mode designs can result in loop

instability and are therefore not recommended.

Similar Part No. - LNK501P

Manufacturer	Part #	Datasheet	Description
Power Integrations, Inc...	LNK501P	155Kb / 20P	Energy Efficient, CV/CC Switcher for Very Low Cost Chargers and Adapters
	LNK501P	419Kb / 23P	2.2W Cell Phone Charger
	LNK501P	419Kb / 23P	2.2W Cell Phone Charger

More results

Similar Description - LNK501P

Manufacturer	Part #	Datasheet	Description
Power Integrations, Inc...	LNK501GN	817Kb / 10P	Energy Efficient, CV/CC Switcher for Very Low Cost Chargers and Adapters
	LNK501	155Kb / 20P	Energy Efficient, CV/CC Switcher for Very Low Cost Chargers and Adapters
	LNK520	1Mb / 20P	Energy Efficient, CV or CV/CC Switcher for Very Low Cost Chargers and Adapters September 2016
	LNK500	505Kb / 20P	Energy Efficient, CV or CV/CC Switcher for Very Low Cost Adapters and Chargers
	LNK520	847Kb / 20P	Energy Efficient, CV or CV/CC Switcher for Very Low Cost Adapters and Chargers
	LNK500GN	835Kb / 10P	Energy Efficient, CV or CV/CC Switcher for Very Low Cost Adapters and Chargers
	LNK605PG	883Kb / 18P	Energy-Efficient, Accurate CV/CC Switcher for Adapters and Chargers
	LNK604PG	883Kb / 18P	Energy-Efficient, Accurate CV/CC Switcher for Adapters and Chargers
	LNK603	2Mb / 18P	Energy-Efficient, Accurate CV/CC Switcher for Adapters and Chargers October 2020
	LNK603	883Kb / 18P	Energy-Efficient, Accurate CV/CC Switcher for Adapters and Chargers

More results

LNK501P Datasheet(PDF) 6 Page - Power Integrations, Inc.

LNK501P Datasheet(HTML) 6 Page - Power Integrations, Inc.

Similar Part No. - LNK501P

Similar Description - LNK501P

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Datasheet Download

Link URL