UC3842 Просмотр технического описания (PDF) - Philips Electronics

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UC3842

Current-mode PWM controller

Philips Electronics 

Philips Semiconductors Linear Products

Current-mode PWM controller

Product specification

UC3842

OFF-LINE FLYBACK REGULATOR

AC

INPUT

4.7 1W

673-3

220µF

250V

56k

1W

4.7k

4W

1N3613

0.01µF

400V

1N3613

T1 USD735

4700µF

10V

+

DC

OUT

(5V

2–5A)

–

20k

3.6k

0.01µF

16V

UC3842

VCC 7

0.01µF

150k

2

VFB

1

COMP

100pF

8

VREF

10k

4

RT/CT

0.0047µF

6

27

OUT

3

CUR

SEN

470pF

GND 5

10µF

20V

20k

1k

820pF

2.5k

UFN432

0.85

NOTES:

T1: Coilcraft E-4140-B

Primary – 97 turns

single AWG24

Secondary – 4 turns

4 parallel

AWG22

control – 9 turns

–3 parallel AWG28

ISOLATION

BOUNDARY

SPECIFICATIONS

Input line voltage:

Input frequency:

Switching frequency:

Output power:

Output voltage:

Output current:

Line regulation:

Load regulation:

Efficiency @ 25 W,

VIN=90VAC:

VIN=130VAC:

Output short-circuit current:

90VAC to 130VAC

50 or 60Hz

40kHz±10%

25W maximum

5V±5%

2 to 5A

0.01%/V

8%/A*

70%

65%

2.5A average

NOTE:

This circuit uses a low-cost feedback scheme in which the DC

voltage developed from the primary-side control winding is sensed

by the UC3842 error amplifier. Load regulation is therefore

dependent on the coupling between secondary and control

windings, and on transformer leakage inductance. For applications

requiring better load regulation, a UC1901 Isolated Feedback

Generator can be used to directly sense the output voltage.

August 31, 1994

1106

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