ST AN1246 Application note

AN1246

Application note

VIPower: auxiliary BIAS

power supply using VIPer20A-E

Introduction

This application note describes a bias power supply to meet the needs of powering up Power MOSFETs as well as providing standby power when the main unit is off.

The VIPer20ADIP-E, a part of STMicroelectronics proprietary VIPower (Vertical Intelligent Power), is a current mode PWM with a 700 V avalanche rugged Power MOSFET. It uses a fabrication process which allows the integration of analog control circuits with a vertical power device on the same chip. It can provide an output of 10 W power capability for wide range input, or 20 W for single input voltage range.

October 2007 Rev 4 1/8

www.st.com

Contents AN1246

Contents

1 Key features of the VIPer20ADIP-E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 General circuit description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

3 Connecting the demoboard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4 Layout considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

5 Burst mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

6 Performance and cost consideration . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

7 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

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AN1246 Key features of the VIPer20ADIP-E

1 Key features of the VIPer20ADIP-E

■ Adjustable switching frequency up to 200 kHz

■ Current mode control

■ Burst mode operation in standby mode, meets “Blue Angel” standards

■ Undervoltage lock-out with hysteresis

■ Integrated start-up supply

■ Avalanche rugged

■ Overtemperature protection

■ Primary or secondary regulation general circuit description

2 General circuit description

This demo board (see schematic in Figure 1) is a 110 to 375 VDC input discontinuous flyback, working at 100 kHz. The output can deliver 12 V at 0.5 A continuous. This circuit can be powered from the main bulk capacitors of an off-line power supply, power factor correction output stage, or the AC line with the addition of a low current bridge rectifier. It benefits from the EMI filter present in a typical power supply. The output uses a Schottky diode for better efficiency. C7 is a low ESR capacitor which manages the ripple current. IC2 provides the reference and the feedback to tightly regulate the output. CS5, CS6, and RS3 form the feedback loop compensation to optimize stability during transients. The demoboard can be tested with convection air. Depending on the final application, air flow might be needed to keep the VIPer20ADIP-E under the thermal shutdown limit.

Figure 1. Schematic

CON

2 1

0.5 A Pico Fuse

3.9

C12

220pF

1KV

BYT11-600

C10

RS14

220pF

82K

1KV

RS4

DS3

1.6

LL4148

4.7uF

400V

C3 120uF

16V

IC1

RS10 nu

drain

VIPer20ADIP-E

source

osc

vdd

compdrain

Cramer Coil CSM 1608-027

128T

3 2

14T

RS2

4.99K

CS4

3.9nF

2.2n

Y cap

CS5

33n

DS2

STPS1H100A

16T

CS6

.47u

RS3

5.1k

680uF

16V

150

IC3

H11A817A

IC2

TL431

A C

10uH

1.2k

5.23k

CS11

47n

RS5

1.37k

C8 330uF

16V

1 2

R11

CON

2.7k

3/8

General circuit description AN1246

Table 1. Electrical specification from measured results

Parameter Results

Input voltage range J1 110 to 375 V

Output J2 12 V from 0 to 0.5 A

Load regulation (0 to 0.5 A) from setpoint +/-25 mV or +/-0.2%

Line regulation (at max load) +/-1 mV

Efficiency 84% at 120 V

and 79% at 375 V

Output ripple voltage 35 mV MAX

Input power at no load 0.65 W MAX

Transient response, 50% load step +/-60 mV typical

Figure 2. PC board top legend bottom foil and surface mount components

Table 2. Component list

Quantity Reference Description Value

1 C2 F4.7 µF 400 V

1 C3 120 µF 16 V (low ESR)

1 CS4 3.9 nF 50 V

1 CS5 33 nF 50 V

1 CS6 47 µF 25 V

1 C7 680 µF 16 V (low ESR)

1 C8 330 µF 16 V (low ESR)

1 C9 Y1 Rated safety cap 2.2 nF

1 C10 220 pF 1 KV

1 CS11 47 µF 50 V

1 C12 220 pF 1 KV

1 D1 BYT11-600

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(1)

600 V 1 A Ultrafast

AN1246 General circuit description

Table 2. Component list (continued)

Quantity Reference Description Value

1 DS2 STPS1H100A

1 DS3 LL4148

1 F1 fuse 0.5 A pico

1 IC1 VIPer20ADIP-E

1 IC2 TL431

1 IC3 H11A817A (optocoupler)

1 J1 Connector terminal

1 J2 Connector terminal

1 L2 Coilcraft PCH-27-103 10 µH

1 RS2 4.99 KΩ 1% 1/8 W

1 RS3 5.1 KΩ 1/8 W

1 RS4 1.6 Ω 1/8 W

1 RS5 1.37 Ω 1% 1/8 W

1 R6 150 Ω 1/4 W

1 R7 5.23 KΩ 1% 1/4 W

(1)

100 V 1 A Schottky

(1)

1 R8 1.2 KΩ 1/4 W

1 R9 3.9 Ω 1/4 W

1 R11 2.7 KΩ 1/4 W

1 RS14 82 KΩ 1/4 W

1 T1 Cramer Coil CSM 1608-027

1. Parts available from STMicroelectronics. “S” in legend denotes a surface mount part.

Table 3. Transformer specification

Parameter Value

Primary inductance 1.65 mH

Core C40 EE16

Figure 3. Cross section of the transformer

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Connecting the demo board AN1246

3 Connecting the demo board

This demo board has two connectors. Connect a DC voltage source capable of delivering up to 400 volts DC to connector J1. Be sure to connect the positive source to the + terminal of J1 and the negative to the terminal before turning on the input power. The minimum voltage to operate this demo board is 110 V

. Connect an electronic load or resistive load to J2.

4 Layout considerations

Some simple rules to improve performance and minimize noise should be followed:

1. Minimize power loops. The switched power current paths inner loop area must be as small as possible. This can be accomplished by careful layout of the printed circuit board and the use of surface mount components. This avoids radiated and conducted EMI noise, and improves the efficiency by eliminating parasitic inductance, thus reducing or eliminating the need for snubbers and EMI filtering.

2. Use separate tracks for low level signal and power traces carrying fast switching pulses. This can be seen on the VIPer20ADIP-E pin 3 on the printed circuit lay out. When signal paths share the same trace as a power path, instabilities may result. The compensation components, CS6, RS3, and CS4 are on a separate trace connected directly to the source of the device.

5 Burst mode

When the output current is too low, the burst mode operation takes over automatically. This results in missing cycles as shown on the following scope waveform (Figure 4). V V

DC IOUT

As can be seen, there is one pulse out of ten pulses to reduce power consumption. The output ripple is negligible.

is at no load.

is 375

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AN1246 Revision history

Figure 4. Burst mode waveform

6 Revision history

Table 4. Document revision history

Date Revision Changes

04-Jan-2004 3 Minor text changes

18-Oct-2007 4

– Document reformatted no content change – VIPer20A replaced by VIPer20A-E – VIPer20ADIP replaced by VIPer20ADIP-E

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AN1246

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