TOP246F- View Datasheet(PDF) - Power Integrations, Inc

Part Name

Description

Manufacturer

TOP246F-

TOPSwitch-GX Family Extended Power, Design Flexible, EcoSmart, Integrated Off-line Switcher

Power Integrations, Inc 

TOP242-250

A High Efficiency, 250 W, 250-380 VDC Input Power Supply

The circuit shown in Figure 43 delivers 250 W (48 V @

5.2 A) at 84% efficiency using a TOP249 from a 250 VDC to

380 VDC input. DC input is shown, as typically at this power

level a p.f.c. boost stage would preceed this supply, providing the

DC input (C1 is included to provide local decoupling). Flyback

topology is still usable at this power level due to the high output

voltage, keeping the secondary peak currents low enough so

that the output diode and capacitors are reasonably sized.

In this example, the TOP249 is at the upper limit of its power

capability and the current limit is set to the internal maximum

by connecting the X pin to SOURCE. However, line sensing

is implemented by connecting a 2 MΩ resistor from the L pin

to the DC rail. If the DC input rail rises above 450 VDC, then

TOPSwitch-GX will stop switching until the voltage returns to

normal, preventing device damage.

Due to the high primary current, a low leakage inductance

transformer is essential. Therefore, a sandwich winding with

a copper foil secondary was used. Even with this technique,

the leakage inductance energy is beyond the power capability

of a simple Zener clamp. Therefore, R2, R3 and C6 are added

in parallel to VR1. These have been sized such that during

normal operation, very little power is dissipated by VR1,

the leakage energy instead being dissipated by R2 and R3.

However, VR1 is essential to limit the peak drain voltage

during start-up and/or overload conditions to below the 700 V

rating of the TOPSwitch-GX MOSFET.

The secondary is rectifed and smoothed by D2 and C9, C10 and

C11. Three capacitors are used to meet the secondary ripple

current requirement. Inductor L2 and C12 provide switching

noise filtering.

A simple Zener sensing chain regulates the output voltage.

The sum of the voltage drop of VR2, VR3 and VR4 plus the

LED drop of U2 gives the desired output voltage. Resistor R6

limits LED current and sets overall control loop DC gain.

Diode D4 and C14 provide secondary soft-finish, feeding

current into the CONTROL pin prior to output regulation and

thus ensuring that the output voltage reaches regulation at start-

up under low line, full load conditions. Resistor R9 provides a

discharge path for C14. Capacitor C13 and R8 provide control

loop compensation and are required due to the gain associated

with such a high output voltage.

Sufficient heat sinking is required to keep the TOPSwitch-GX

device below 110 °C when operating under full load, low line

and maximum ambient temperature. Airflow may also be

required if a large heatsink area is not acceptable.

+250-380

VDC

R2

R3

VR1

P6KE200

68 kΩ

2W

68 kΩ

2W

C6

4.7 nF

1 kV

C7

2.2 nF Y1

D2

MUR1640CT

C10

560 µF

63 V

C11

560 µF

63 V

L2

3 µH 8A

48 V@

5.2 A

C9

560 µF

63 V

C12

68 µF

63 V

R1

2 MΩ

1/2 W

D1

BYV26C

D2

1N4148

T1

C1

22 µF

400 V

TOPSwitch-GX

PERFORMANCE SUMMARY

Output Power:

250 W

D

L

TOP249Y

U1

CONTROL

C

Line Regulation:

± 1%

Load Regulation:

Efficiency:

± 5%

≥ 85%

S

Ripple:

< 100 mV pk-pk

No Load Consumption: ≤ 1.4 W (300 VDC)

XF

C3

0.1 µF

50 V

R4

6.8 Ω

C3

47 µF

10 V

C4

1 µF

50 V

U2

LTV817A

R6

100 Ω

C13

150 nF

63 V

VR2 22 V

BZX79B22

VR3 12 V

BZX79B12

VR4 12 V

BZX79B12

RTN

R9

10 kΩ

D4

1N4148

R8

56 Ω

C14

22 µF

63 V

0V

All resistor 1/8 W 5% unless

otherwise stated.

PI-2692-081204

Figure 43. 250 W, 48 V Power Supply using TOP249.

22 M

12/04

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