ST AN1344 Application note

AN1344

Application note

VIPower: 108 W power supply using VIPer100A-E

Introduction

The VIPer100A-E is designed to deliver 100 W for the upper voltage range or 50 W for universal input. This application note describes a power supply that delivers over 100 W for both voltage ranges using a voltage doubler in the front end. The VIPer100A-E combines a state-of-the-art PWM circuit along with an optimized 700 V avalanche rugged Vertical Power MOSFET. It is part of STMicroelectronics’ proprietary VIPower, (Vertical Intelligent Power). It uses a fabrication process, which allows the integration of analog control circuits with vertical power device on the same chip.

This document covers the implementation and results for achieving 18 V at 6 A power supply that runs from both European and domestic mains. (90-132 Vac and 180264 Vac, 47-63 Hz).

October 2007

Rev 2

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Contents	AN1344

Contents

1	Key features of the VIPer100A-E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		. 3
2	General circuit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		4
	2.1	Transformer construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .	6
3	Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		9
4	Burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		9
5	Thermal consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		11
6	Overcurrent limiting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		11
7	Transient response 50% step change . . . . . . . . . . . . . . . . . . . . . . . . . .		12
8	Output ripple . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		12
9	EMI consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		12
10	Performance and cost consideration . . . . . . . . . . . . . . . . . . . . . . . . . .		12
11	Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		12
12	Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .		13

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AN1344	Key features of the VIPer100A-E

1Key features of the VIPer100A-E

■Adjustable switching frequency up to 20 kHz

■Current mode control

■Burst mode operation in standby mode, meets "Blue Angel"

■Undervoltage lock-out with hysteresis

■Integrated start-up supply

■Avalanche rugged

■Overtemperature protection

■Primary or secondary regulation

Figure 1. Board layout

The power supply has low ripple voltage, good transient response, and be able to current limit by power limiting and cycling on and off during a hard short. One use of this application is to replace a bulky 60 Hz transformer with a lighter, better regulated, more efficient alternative for an audio or entertainment system.

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General circuit description	AN1344

2 General circuit description

The power supply has been designed for the upper voltage range. The lower voltage range utilizes a voltage doubler to raise the bulk voltage to 2 times the peak of the input line voltage. In the doubling mode, the current charges one capacitor for each phase of the line, therefore doubling the voltage. When SW1 is open, both capacitors are charged in series resulting in a bulk voltage equal to the peak of the line input.

A wire jumper can be installed at production for units destined for countries using the lower range. The switching frequency operates at 100 kHz. The output can deliver 18 V from no load to 6 A continuous. The mode of operation ranges from discontinuous at high line minimum load to continuous at low line max load. This mode of operation was chosen to minimize the high peak currents of the discontinuous mode of operation.

The VIPer100A-E can be regulated in secondary mode with an optocoupler giving excellent regulation or in the primary mode. Primary regulation works by regulating the Vdd pin at the output of the auxiliary winding. Depending on the coupling of the transformer, a 15% regulation can be achieved. In this application, by taking advantage of the dual regulation, a current limit scheme is obtained. This VIPer100A-E advantage, along with the transformer design, constitutes the overcurrent circuit. The transformer is designed for a turn ratio of operation for a universal input and an inductance to run in continuous conduction mode at one-half the output load. The coupling between the secondary to auxiliary winding along with the VIPer100A-E dual regulation plays an important part in the current limit.

Under typical operation, the output is tightly regulated through U2 and U3, the optocoupler and TL431 respectively. As the output current increases, it causes the voltage at the auxiliary output to increase. R4 is selected to trim the voltage at Vdd to reach 13 V when the output current exceeds the maximum limit. At this point, primary regulation takes over and the output starts to fold-back.

The output uses an STMicroelectronics 100 V Schottky diode for better efficiency. C9 and C10 are low ESR capacitors which manage the ripple current. U3 provides the reference and the feedback to tightly regulate the output. C7, C8, and R6 form the feed back loop compensation to optimize stability during transients.

Table 1.	Electrical specification
	Parameter	Results
	Input voltage	90-132 VAC with jumper in, 180 - 264 VAC no jumper
	Output voltage J2
Load regulation (0.6 to 6 A) from set point		+/- 0.6%
Line regulation (at max load)		+/- 0.05%
	Efficiency	86% @120 VDC and 87% @ 375 VDC
	Output ripple voltage	15 mV max
	Input power at no load	1.5 W typical
Transient response, 50% load step		+/- 350 mV, +/- 1.9%, 200 µs settling time
	EMI	EN55022 and FCC class B

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AN1344

.2 Table

2 Figure

factor)(alratingInductance

inductanceleakagePrimary

inductancePrimary

specificationTransformer

.

Note

Core

Parameter

3

3

.1uF

C17

2

BRIDGE

1N4148

8.2

R13

C16

schematicElectrical

22

.5W

.001uf 1KV

TX1

18 V @ 6A

Cramer Coil

D3

E34351E

L4

5

9

.

.

1

STPS20H100C

10uH

BR1

R3

7

CON2

F2

.

T

D5

200

C4 100pF

2W

2

1KV

BZW50-180

C10

1

4

3

1800uF

C11

C2

2

1

4

.

C9

25V

470uF

J2

FUSE

330uF

D1

2

1800uF

25V

.

2.5A

200V

600V

STTA106

25V

J1

5X20mm

R12

2

1

ST

1

3

470k

1

1

3

C1

600V 2A

D2

R4

.

2

2

X CAP

.1uF

R0

C14

R5

CON

X CAP

4.22K

2

4

1%

0

2.2nF

R1

6

SW1

HS

Y1 cap

33

L1

1

2

1

U1

Thermistor

2 X 6mH

SW SPST

OSC

VIPer100A-E

2

Close for 120Vac

VDD

R8

3

DRAIN

C20

10

4

SOURCE

330uf

C6

5

COMP

C8

R9

R11

200V

4.7nF

1uF

R7

1k

20K

50V

50V

220

1%

Split

C5

R00

R14

180uF

C15

0 ohms

4

1

16V

.1uF

R6

U2

50V

470k

D4

C7

6.2K

H11A817A

3

2

5/14

coregapped-primary

nH/T329

ETD34

µH9.7

µH525

Value

NU

22nF

descriptioncircuitGeneral

50V

C12

3

U3

.1uF

50V

TL431

1

2

R10

3.16K

1%