TOP257YN datasheet(24/50 Pages) POWERINT

24 / 50 page

Rev. M 12/21

TOP252-262

www.power.com

A High Efficiency, 65 W, Universal Input Power Supply

The circuit shown in Figure 44 delivers 65 W (19 V @ 3.42 A) at

88% efficiency using a TOP260EN operating over an input

voltage range of 90 VAC to 265 VAC.

Capacitors C1 and C6 and inductors L1 and L2 provide

common mode and differential mode EMI filtering. Capacitor C2

is the bulk filter capacitor that ensures low ripple DC input to the

flyback converter stage. Capacitor C4 provides decoupling for

switching currents reducing differential mode EMI.

In this example, the TOP260EN is used at reduced current limit

to improve efficiency.

Resistors R5, R6 and R7 provide power limiting, maintaining

relatively constant overload power with input voltage. Line

sensing is implemented by connecting a 4 M

W impedance from

the V pin to the DC rail. Resistors R3 and R4 together form the

4 M

W line sense resistor. If the DC input rail rises above

450 VDC, then TOPSwitch-HX will stop switching until the

voltage returns to normal, preventing device damage.

This circuit features a high efficiency clamp network consisting

of diode D1, zener VR1, capacitor C5 together with resistors R8

and R9. The snubber clamp is used to dissipate the energy of

the leakage reactance of the transformer. At light load levels,

very little power is dissipated by VR1 improving efficiency as

compared to a conventional RCD clamp network.

The secondary output from the transformer is rectified by diode

D2 and filtered by capacitors C13 and C14. Ferrite Bead L3 and

capacitors C15 form a second stage filter and effectively reduce

the switching noise to the output.

Output voltage is controlled using a LM431 reference IC.

Resistor R19 and R20 form a potential divider to sense the

output voltage. Resistor R16 limits the optocoupler LED current

and sets the overall control loop DC gain. Control loop

compensation is achieved using C18 and R21. The components

connected to the control pin on the primary side C8, C9 and

R15 set the low frequency pole and zero to further shape the

control loop response. Capacitor C17 provides a soft finish

during startup. Optocoupler U2 is used for isolation of the

feedback signal.

Diode D4 and capacitor C10 form the bias winding rectifier and

filter. Should the feedback loop break due to a defective

component, a rising bias winding voltage will cause the Zener

VR2 to break down and trigger the over voltage protection

which will inhibit switching.

An optional secondary side over voltage protection feature

which offers higher precision (as compared to sensing via the

bias winding) is implemented using VR3, R18 and U3. Excess

voltage at the output will cause current to flow through the

optocoupler U3 LED which in turn will inject current in the V-pin

through resistor R13, thereby triggering the over voltage

protection feature.

Figure 44. 65 W, 19 V Power Supply Using TOP260EN.

PI-4998-021408

R16

Ω

R21

1 k

Ω

R20

10 k

Ω

R19

68.1 k

Ω

R18

Ω

R16

680

Ω

LM431

VR3

BZX79-C22

22 V

DL4937

1N4148

BAV19WS

VR2

1N5248B

18 V

VR1

BZY97C180

180 V

R13

5.1

Ω

R14

100

Ω

R12

5.1 k

Ω

R11

2 M

Ω

2.2 M

Ω

2.2 M

Ω

R15

6.8

Ω

R10

73.2 k

Ω

100

Ω

1 k

Ω

U3B

PC357A

U3A

PC357A

U2B

LTY817C

U2A

LTY817C

Ferrite

Bead

12 mH

Ferrite Bead

TOP260EN

µF

16 V

C16

µF

50 V

C17

µF

35 V

C18

100 nF

C11

100

50 V

C10

µF

50 V

D4 BAV19WS

MBR20100CT

100 nF

50 V

100 nF

400 V

3KBP08M

BR1

C13

470

µF

25 V

C14

470

µF

25 V

C15

µF

25 V

C12

1 nF

100 V

RM10 FL1

FL2

2.2 nF

250 VAC

330 nF

275 VAC

4 A

TOPSwitch-HX

19 V, 3.42 A

RTN

120

µF

400 V

470 pF

250 VAC

100 nF

25 V

2.2 nF

1 kV

90 - 265

VAC

CONTROL

2.0 M

Ω

5.1 M

Ω

2.0 M

Ω

15 k

Ω

6.8 M

Ω

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