LNK6663E(2014) Ver la hoja de datos (PDF) - Power Integrations, Inc

Número de pieza

componentes Descripción

Fabricante

LNK6663E
(Rev.:2014)

Energy Effcient, High-Power Off-Line Switcher with Accurate Primary-Side Regulation (PSR)

Power Integrations, Inc 

LinkSwitch-HP

Applications Example

30 W, 12 V Universal Adapter

The circuit shown in Figure 11 is a high efficiency universal input

30 W, 12 V output adapter using the LNK6766E.

The supply uses primary winding coupled sensing for the

following features: output regulation, line undervoltage lockout,

input and output OVP. With primary winding sense there is no

need for an external secondary referenced error amplifier such

as a TL431 and optocoupler. The winding sense of bus voltage

also eliminates the need for direct input voltage sensing which

requires more components and is more dissipative than winding

sense method.

Output regulation is ±5%, active-on efficiency is 86% and

no-load input power is less than 30 mW.

The rectified and filtered input voltage is applied to the primary

winding of T1. The other side of the primary is driven by the

integrated power MOSFET in U1. Diode D1, C3, R2, R3 and

VR1 comprise the clamp circuit, limiting the leakage inductance

turn-off voltage spike to safe value. Zener diode VR1 also helps

to reduce input power consumption during no-load conditions.

Start-up of the power supply is initiated by sensing the forward

negative pulse current from feedback winding through R19 into

the FEEDBACK pin. This sensing is accomplished by periodically

turning on the power MOSFET to sense input voltage condition

with very short low frequency sampling pulses. During the

forward pulse sampling time the FEEDBACK pin is held to zero

volts by an internal clamp. When negative forward pulse current

exceeds 250 mA, LinkSwitch-HP for two consecutive switching

cycles will initiate start-up with a soft-start sequence that reduces

component stress and allows the output to rise in a smooth

monotonic manner. The desired input voltage for start-up is

determined by the turns ratio of primary winding to feedback

winding and the value of R19.

Regulation is accomplished by sampling the feedback winding

during flyback period through the resistor divider R19 and R20

through FEEDBACK pin. This sampled voltage is compared to

an internal error amplifier threshold of 2 V. The value of R19 is

already determined by the line undervoltage function so the

output regulation point is determined by setting the proper

value for R20.

The loop compensation is provided by the network from

COMPENSATION pin to ground. In the case above, a low

frequency to mid frequency gain of 20 dB for the error amplifier

is established by R7 and C7. Capacitor C8 functions essentially

as a noise filter and is typically 100 pF. There is also an internal

16 kHz filter within the device. It is advised to limit R7 to no

greater than 260 kW to avoid stability and noise sensitivity.

BR2

DF206ST-G

600 V

L4

10 mH

C14

150 nF

275 VAC

C2

68 µF

400 V

R3

3 kΩ

VR1

BZG03C130

130 V

C3

10 nF

630 V

R2

100 Ω

1/2 W

D1

DL4937

C18

2.2 nF

250 VAC

9

FL1

FL2

7

6

8

T1

RM8

C13 R13

680 pF 20 Ω

100 V 1/8 W

D8

STPS30100ST

L5

100 µH

12 V, 2.5 A

J3

C12

1000 µF

16 V

R28

27 kΩ

C22

10 µF

16 V

D2

BAV21WS-

7-F

R19

41.2 kΩ

1%

C6

22 µF

16 V

R9

4.3 kΩ

1%

1/8 W

RTN

J4

R29 R30

3.3 MΩ 3.3 MΩ

F1

2A

90 - 265

VAC

J1

J2

D

LinkSwitch-HP

U1

LNK6766E

S

BP

CONTROL

FB

PD CP

C20

4.7 nF

50 V

R8

23.2 kΩ

1%

1/8 W

R7

100 kΩ

1/8 W

C7

100 nF

25 V

C23

10 pF

50 V

C8

100 pF

50 V

Figure 11. Schematic of a Universal Input 30 W, 12 V, 2.5 A Adapter.

8

Rev. C 03/14

R20

10.2 kΩ

1%

C5

470 nF

50 V

PI-6844-120312

www.powerint.com

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