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 V 47-63 Hz).

and 180- 264 Vac,

October 2007 Rev 2 1/14

www.st.com

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

1 Key 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 V 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.

pin at the

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 V

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 V

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 V

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

with jumper in, 180 - 264 VAC no jumper

and 87% @ 375 VDC

EMI EN55022 and FCC class B

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AN1344 General circuit description

STPS20H100C

C14

2.2nF

Y1 cap

Thermistor

R14

470k

CON2

BZW50-180

.1uF

X CAP

100pF

1KV

Close for 120Vac

330uF

200V

C20

330uf

200V

4.7nF

50V

R12

470k

C15

.1uF

50V

FUSE

2.5A

5X20mm

CON

123

C10

1800uF

25V

4.22K

200

BR1

600V 2A

BRIDGE

4 3

R11

20K

C16

.001uf 1KV

R13

22 .5W

STTA106

600V

H11A817A

1N4148

SW1

SW SPST

1 2

18 V @ 6A

22nF

50V

2 X 6mH

8.2

10uH

C11

470uF

25V

220

C12

.1uF

50V

C17

.1uF

X CAP

1uF

50V

E34351E

TX1

Cramer Coil

394

...

180uF

16V

241

VDD

SOURCE

OSC

DRAIN

COMP

TL431

R10

3.16K

6.2K

1800uF

25V

R00

0 ohms

VIPer100A-E

Figure 2. Electrical schematic

Table 2. Transformer specification

Primary inductance 525 µH

Primary leakage inductance 7.9 µH

Inductance rating (al factor) 329 nH/T

Parameter Value

Core ETD34

Note Split primary - gapped core

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