TOP246P Просмотр технического описания (PDF) - Power Integrations, Inc

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TOP246P

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

Power Integrations, Inc 

increase efficiency. This design delivers 70 W at 19 V, from an

85 VAC to 265 VAC input, at an ambient of 40 °C, in a small

sealed adapter case (4” x 2.15” x 1”). Full load efficiency is

85% at 85 VAC rising to 90% at 230 VAC input.

Due to the thermal environment of a sealed adapter, a TOP249Y

is used to minimize device dissipation. Resistors R9 and R10

externally program the current limit level to just above the

operating peak DRAIN current at full load and low line. This

allows the use of a smaller transformer core size without

saturation during startup or output load transients. Resistors

R9 and R10 also reduce the current limit with increasing line

voltage, limiting the maximum overload power at high input

line voltage, removing the need for any protection circuitry on

the secondary. Resistor R11 implements an under-voltage and

overvoltage sense as well as providing line feed-forward for

reduced output line frequency ripple. With resistor R11 set at

2 MΩ, the power supply does not start operating until the DC

rail voltage reaches 100 VDC. On removal of the AC input,

the UV sense prevents the output glitching as C1 discharges,

turning off the TOPSwitch-GX when the output regulation is

lost or when the input voltage falls to below 40 V, whichever

occurs first. This same value of R11 sets the OV threshold to

450 V. If exceeded, for example during a line surge,

TOPSwitch-GX stops switching for the duration of the surge,

extending the high voltage withstand to 700 V without device

damage. Capacitor C11 has been added in parallel with VR1 to

TOP242-250

reduce Zener clamp dissipation. With a switching frequency of

132 kHz, a PQ26/20 core can be used to provide 70 W. To

maximize efficiency, by reducing winding losses, two output

windings are used each with their own dual 100 V Schottky

rectifier (D2 and D3). The frequency reduction feature of the

TOPSwitch-GX eliminates any dummy loading to maintain

regulation at no load and reduces the no-load consumption of

the power supply to only 520 mW at 230 VAC input. Frequency

jittering provides conducted EMI meeting the CISPR 22

(FCC B) / EN55022B specification, using simple filter components

(C7, L2, L3 and C6), even with the output earth grounded.

To regulate the output, an optocoupler (U2) is used with a

secondary reference sensing the output voltage via a resistor

divider (U3, R4, R5, R6). Diode D4 and C15 filter and smooth

the output of the bias winding. Capacitor C15 (1 µF) prevents

the bias voltage from falling during zero to full load transients.

Resistor R8 provides filtering of leakage inductance spikes,

keeping the bias voltage constant even at high output loads.

Resistor R7, C9 and C10 together with C5 and R3 provide

loop compensation.

Due to the large primary currents, all the small signal control

components are connected to a separate source node that is

Kelvin connected to the SOURCE pin of the TOPSwitch-GX.

For improved common-mode surge immunity, the bias winding

common returns directly to the DC bulk capacitor (C1).

C13 C12 C11

0.33 µF 0.022 µF 0.01 µF

400 V 400 V 400 V

BR1

RS805

8A 600 V

C7 2.2 nF

Y1 Safety

VR1

P6KE-

200

D1

UF4006

D2

MBR20100

D3

MBR20100

PERFORMANCE SUMMARY

Output Power:

Regulation:

Efficiency:

Ripple:

No Load Consumption:

70 W

± 4%

≥ 84%

≤ 120 mV pk-pk

< 0.52 W @ 230 VAC

C3

820 µF

25 V

L1

200 µH

C14

0.1 µF

50 V

19 V

@ 3.6 A

L2

820 µH

2A

C6

0.1 µF

X2

RT1

10 Ω t°

1.7 A

F1

J1 3.15 A

L

C1

150 µF

400 V

L3

75 µH

2A

N

D

R9

13 MΩ

S

R10

20.5 kΩ

C2

R11

D4

1N4148

820 µF

25 V

2 MΩ

1/2 W

T1

R8

4.7 Ω

U2

PC817A

C15

L TOPSwitch-GX

CONTROL

C

TOP249Y

U1

1 µF

50 V

C4

R1

820 µF

270 Ω

25 V

R4

31.6 kΩ

1%

R2

1 kΩ

R5

562 Ω

C9

1%

4.7 nF 50 V

RTN

XF

C8

0.1 µF

50 V

R3

6.8 Ω

C5

47 µF

16 V

U3

TL431

R7

56 kΩ

C10

0.1 µF

50 V

R6

4.75 kΩ

1%

All resistors 1/8 W 5% unless otherwise stated.

PI-2691-042203

Figure 42. 70 W Power Supply using Current Limit Reduction with Line and Line Sensing for UV and OV.

21 M

12/04

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