SG1842L View Datasheet(PDF) - Microsemi Corporation

Part Name

Description

Manufacturer

SG1842L

Current Mode PWM Controller

Microsemi Corporation 

Typical Application Circuits

AC

INPUT

4.7Ω 1W

673-3

+ 220µF

250V

56kΩ

1W

0.01pF

400V

1N3613

1N3613

16V

20kΩ

SG1842

VCC

VFB

0.01 µF

+

10µF

20V

150kΩ

COMP

3.6kΩ

100 pF

VREF

0.01 µF

10kΩ

RT /CT

0.0047µF

OUT

CUR

SEN

GND

27Ω

20kΩ

1kΩ

470 pF

820pF

2.5kΩ

0.85Ω

T1

USD735

+

+

4700µF

10V

5V

2 – 5A

-

T1: Coilcraft E - 4140 – b

Primary - 97 turns

single AWG 24

Secondary - 4 turns

4 parallel AWG 22

Control - 9 turns

3 parallel AWG 28

ISOLATION

BOUNDARY

Figure 27 · Off-line Flyback Regulator

SPECIFICATIONS

Input line voltage:

90VAC to 130VAC

Input frequency:

50 or 60Hz

Switching frequency:

40kHz ±10%

Output power:

25W maximum

Output voltage:

5V +5%

Output current:

2 to 5A

Line regulation:

0.01%/V

Load regulation:

8%/A*

Efficiency @ 25 Watt:

VIN = 90VAC: 70%

VIN = 130VAC: 65%

Output short-circuit current: 2.5 A average

*This circuit uses a low-cost feedback scheme in which the DC voltage developed from the primary-side

control winding is sensed by the SG1842 error amplifier. Load regulation is therefore dependent on the

coupling between secondary and control windings, and on transformer leakage inductance.

19

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