TOP267(2010) Ver la hoja de datos (PDF) - Power Integrations, Inc

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TOP267
(Rev.:2010)

Integrated Off-Line Switcher with EcoSmart® Technology for Highly Effcient Power Supplies

Power Integrations, Inc 

TOP264-271

Application Example

Low No-load, High Efficiency, 65 W, Universal Input

Adapter Power Supply

The circuit shown in Figure 24 shows a 90 VAC to 265 VAC

input, 19 V, 3.42 A output power supply, designed for operation

inside a sealed adapter case type. The goals of the design were

highest full load efficiency, highest average efficiency (average of

25%, 50%, 75% and 100% load points), and very low no-load

consumption. Additional requirements included latching output

overvoltage shutdown and compliance to safety agency limited

power source (LPS) limits. Measured efficiency and no-load

performance is summarized in the table shown in the schematic

which easily exceed current energy efficiency requirements.

In order to meet these design goals the following key design

decisions were made.

PI Part Selection

• One device size larger selected than required for power

delivery to increase efficiency

The current limit programming feature of TOPSwitch-JX allows

the selection of a larger device than needed for power delivery.

This gives higher full load, low line efficiency by reducing the

MOSFET conduction losses (IRMS2 × RDS(ON)) but maintains the

overload power, transformer and other components size as if a

smaller device had been used.

For this design one device size larger than required for power

delivery (as recommended by the power table) was selected.

This typically gives the highest efficiency. Further increases in

device size often results in the same or lower efficiency due to

the larger switching losses associated with a larger MOSFET.

Line Sense Resistor Values

• Increasing line sensing resistance from 4 MΩ to 10.2 MΩ to

reduce no-load input power dissipation by 16 mW

Line sensing is provided by resistors R3 and R4 and sets the

line undervoltage and overvoltage thresholds. The combined

value of these resistors was increased from the standard 4 MΩ

to 10.2 MΩ. This reduced the resistor dissipation, and therefore

contribution to no-load input power, from ~26 mW to ~10 mW. To

compensate the resultant change in the UV (turn-on) threshold

resistor R20 was added between the CONTROL and VOLTAGE-

MONITOR pins. This adds a DC current equal to ~16 µA into the

V pin, requiring only 9 µA to be provided via R3 and R4 to reach

the V pin UV (turn-on) threshold current of 25 µA and setting the

UV threshold to 95 VDC.

This technique does effectively disable the line OV feature as

the resultant OV threshold is raised from ~450 VDC to ~980 VDC.

However in this design there was no impact as the value of

input capacitance (C2) was sufficient to allow the design to

withstand differential line surges greater than 2 kV without the

peak drain voltage reaching the BVDSS rating of U1.

Specific guidelines and detailed calculations for the value of

R20 may be found in the TOPSwitch-JX Application Note (AN-47).

Clamp Configuration – RZCD vs RCD

• An RZCD (Zener bleed) was selected over an RCD clamp to

give higher light load efficiency and lower no-load consumption

Input Voltage (VAC)

90 115 230

Full Power Efficiency (%) 86.6 88.4 89.1

Average Efficiency (%)

89.8 89.5

No-load Input Power (mW) 57.7 59.7 86.7

D1

GBU8J

600 V

L3

12 mH

R1 R2

2.2 MΩ 2.2 MΩ

C1

330 nF

275 VAC

L4

200 µH

F1

4A

L

90 - 265

VAC

N

R3

R7

5.1 MΩ 10 MΩ

C2

120 µF

400 V

R4

R8

5.1 MΩ 10 MΩ

R9

11 kΩ

1%

C11

1 nF

250 VAC

C12

1 nF R15

100 V 33 Ω

R11

300 Ω

VR2

SMAJ250A

R5

300 Ω

C4

1000 pF

630 V

R6

R28

150 Ω 300 Ω

C5

2.2 nF

1 kV

R29

300 Ω

D2

RS1K

T1

3 RM10 FL1

FL2

1

5

D4

BAV21WS-

4 7-F

D5

V30100C

C10

56 µF

35 V

R24

2.2 Ω

Q1

MMBT4403

D3

BAV19WS

C9

220 nF

25 V

R20

191 kΩ

1%

D

TOPSwitch-JX

U1

TOP269EG

S

V

CONTROL

C

XF

C6

100 nF

50 V

R14

20 Ω

C15

470 pF

50 V

R10

100 Ω

R12

4.7 kΩ

U3B

PS2501-

1-H-A

VR1

ZMM5244B-7

Q2

R25 MMBT3904

20 Ω

1/8 W

R13

6.8 Ω

1/8 W

C7

47 µF

16 V

C13 C14

470 µF 470 µF

25 V 25 V

R16

20 kΩ

U3A

PS2501-

1-H-A

19 V, 3.42 A

C21

10 nF

50 V

RTN

R22

1.6 kΩ

C19

6.8 nF

50 V

R17

147 kΩ

1%

R27

10 kΩ

C22

100 nF

50 V

C16

22 nF

50 V

R19

20 kΩ

U2

LMV431AIMF

1%

R18

10 kΩ

1%

PI-5667-030810

Figure 24. Schematic of High Efficiency 19 V, 65 W, Universal Input Flyback Supply With Low No-load.

www.powerint.com

15

Rev. B 03/10

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