ST UM0920 User manual

May 2012 Doc ID 17220 Rev 2 1/14
UM0920
User manual
4 W non-isolated, wide input-voltage range SMPS demonstration
board based on the VIPer16
Introduction
The purpose of this document is to provide information for the STEVAL-ISA071V2 switched
mode power supply (SMPS) demonstration board. The STEVAL-ISA071V2 is a non-isolated
SMPS capable of delivering a 4 W output over a wide input voltage range, and is designed
for a mains application requiring -5 V and +7 V, referred to neutral. The basic concepts used
in this design can also be applied for higher power outputs or different voltage ranges.
The SMPS generates outputs of 5 V and 12 V, referred to the output marked -5 V. The 5 V is
dedicated to supplying an MCU. This configuration allows the use of the MCU to directly
drive a Triac (referred to neutral). The 12 V output is used to supply additional circuits
(relays, OA, etc.).
This document contains a fundamental technical description of the demonstration board
(schematic diagram, PCB details and bill of materials) and basic measurements (load
regulation, efficiency, standby behavior and EMI data).
Figure 1. STEVAL-ISA071V2 board
www.st.com
Downloaded from Arrow.com.

Contents UM0920
2/14 Doc ID 17220 Rev 2
Contents
1 Main characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2 Board connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3 Board details . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1 Schematic diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.2 Description of main components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3 Transformer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.4 PCB details and layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.5 Bill of materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4 Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
5 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Downloaded from Arrow.com.Downloaded from Arrow.com.

UM0920 List of figures
Doc ID 17220 Rev 2 3/14
List of figures
Figure 1. STEVAL-ISA071V2 board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Figure 2. Input/output connection of SMPS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Figure 3. STEVAL-ISA071V2 circuit schematic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 4. PCB layout - top layer, bottom SMD layer and bottom copper layer . . . . . . . . . . . . . . . . . . 9
Figure 5. Efficiency at 120 VAC and 230 VAC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 6. Load characteristics of 12 V output at 120 VAC and 230 VAC. . . . . . . . . . . . . . . . . . . . . . 11
Figure 7. EMI measurement for EN55022 Class B - AVG detector . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 8. EMI measurement for EN55022 Class B - peak detector. . . . . . . . . . . . . . . . . . . . . . . . . . 12
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

Main characteristics UM0920
4/14 Doc ID 17220 Rev 2
1 Main characteristics
●Input:
–V
IN: 85 - 264 VRMS
– f: 45 - 66 Hz
●Output:
– 12 VDC ± 10% (referred to -5 V), 160 mA
– -5 VDC ± 4%, 400 mA
– Max output power: 4 W (range is up to 6 W for EU)
●Standby power: 35 mW at 230 VAC
●Short-circuit protected
●PCB data:
– Single-sided, 35 µm FR4
– 33 x 45 mm (effective size of SMPS circuitry)
●Isolation: non-isolated, N connected to output GND
●EMI: compliant with EN55022 Class B
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

UM0920 Board connections
Doc ID 17220 Rev 2 5/14
2 Board connections
The STEVAL-ISA071V2 demonstration board is pictured in Figure 2 below, with input and
output locations.
Figure 2. Input/output connection of SMPS
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

Board details UM0920
6/14 Doc ID 17220 Rev 2
3 Board details
3.1 Schematic diagram
A schematic diagram of the non-isolated flyback converter board prototype based on the
VIPer16 is provided in Figure 3 below.
Figure 3. STEVAL-ISA071V2 circuit schematic
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

UM0920 Board details
Doc ID 17220 Rev 2 7/14
3.2 Description of main components
The complete converter application consists of an input section and the flyback converter
itself.
The input section contains:
– Single diode rectifier (D3, D6)
The single diode rectifier is selected to allow simple connection of neutral to GND
and reduce components count.
– Inrush current limiter (R1)
This component reduces the inrush current caused by connection of the SMPS to
mains (charging current of bulk capacitors) or by surge pulses.
– EMI filter (L1, C4, C5)
This basic EMI filter using bulk capacitors and a simple inductor can be applied
due to the single rectifier.
– Input bulk capacitors (C4, C5)
These capacitors store energy when the input AC voltage is low.
The flyback converter consists of:
– VIPer16 (U1)
This device integrates a controller and high voltage power MOSFET in one
package. The controller works in current mode with a fixed frequency, in
discontinuous mode. Thanks to the built-in error amplifier, the VIPer16 can directly
sense the output voltage via a voltage divider. Mandatory components for proper
operation of the VIPer16 are VDD capacitor C10 and compensation network R4,
C8 and C9. Diode D1 is not mandatory but it connects the output voltage to VCC of
the Viper16, reducing standby consumption.
–Peak clamp (D5, R2, R7, C2)
This circuit absorbs energy from the voltage spike present after MOSFET turn-off.
This spike is generated by leakage inductance of the transformer.
– Secondary side (D2, D4, C1, C7)
This consists of two rectifiers and capacitors for each output. The -5 V output is
used for feedback regulation. The main benefit of this solution is the connection of
the source of the VIPer16 to -5 V. This allows direct sensing of -5 V from the output
and simplifies the circuit. Another benefit of this method is the possibility to supply
the VIPer16 from 12 V secondary winding (7 V to -5 V). This configuration results
in a significant reduction in component count and, thanks to the internal error
amplifier, permits reaching a low tolerance of -5 V. The special feature of this
configuration is the fact that the current flowing from the input bulk capacitor
through the primary side of the transformer and power MOSFET is closed back to
the input capacitor via secondary side capacitor C7, and this capacitor is partly
discharged during the ON time. Due to this effect, the use of a low ESR capacitor
for C7 is highly recommended.
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

Board details UM0920
8/14 Doc ID 17220 Rev 2
3.3 Transformer
The transformer was developed in cooperation with EPCOS and is available through order
number T5684-51-01. The transformer specification is as follows:
– E16/8/5 - 60 kHz, voltage range 85 VAC - 264 VAC
– Core shape E16/8/5
– Core material N87
– Core Al 100 nH (0.29 mm gap)
– Bobbin 8-pin - B66308 - B663080A1108T001
3.4 PCB details and layout
The layout of PCB is based on a one-sided FR4, with a 35 µm thickness. The total size of
the PCB is 41 x 58 mm, and the PCB space occupied by electronic circuitry is 33 x 45 mm.
The layout of the PCB is provided in Figure 4.
Table 1. Transformer windings
Layer Start pin Stop pin Number
of turns
Wire
number
Wire
diameter
Wire
material Inductance Position
1 1 2 157 1 0.2 Cu2l 2450 µH Primary
2 8 4 16 1 0.3 Cu2 26 µH Out +7 V
3 4 7 13 1 0.3 Cu2 17 µH Out –5 V
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

UM0920 Board details
Doc ID 17220 Rev 2 9/14
Figure 4. PCB layout - top layer, bottom SMD layer and bottom copper layer
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

Board details UM0920
10/14 Doc ID 17220 Rev 2
3.5 Bill of materials
Table 2. Bill of materials
Number Quantity Ref. Value / generic part
number Package / class Manufacturer
1 1 R1 22 Ω/ 2 W / 5%
2 2 R2, R7 200 kΩ/ 5% 1206
3 1 R3 4.7 kΩ/ 1% / 0.1 W 0805
4 1 R4 4.7 kΩ / 5% / 0.1 W 0805
5 1 R6 9.1 kΩ / 1% / 0.1 W 0805
6 2 C1, C7 100 µF / 25 V / 105 °C D8 RM 5 Rubycon
7 1 C2 1 nF / 500 V 1206
8 2 C4, C5 10 µF / 400 V / 105 °C D10 x 20 RM 5
9 1 C8 1 nF / 50 V 0805
10 1 C9 100 nF / 50 V 0805
11 1 C10 10 µF / 35 V / 105 °C
12 1 L1 2.2 mH / 80 mA
13 1 T1 EF16 T5684-51-01 EPCOS
14 1 D1 TMMBAT41 SOD80
15 1 D2 STPS1H100 SMA STMicroelectronics
16 2 D3, D6 SMD 1N4007 MELF / SMA
17 1 D4 STPS1L60 SMA STMicroelectronics
18 1 D5 STTH1L06 SMA STMicroelectronics
19 1 U1 VIPER16 DIP-7 STMicroelectronics
20 1 J1 Screw terminal 2 pos. RM 5 mm
21 1 J2 Screw terminal 3 pos. RM 5 mm
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

UM0920 Measurements
Doc ID 17220 Rev 2 11/14
4 Measurements
The basic measurements for efficiency, load characteristics and conductive EMI are shown
in Figure 5, Figure 6, Figure 7 and Figure 8.
Figure 5. Efficiency at 120 VAC and 230 VAC
Figure 6. Load characteristics of 12 V output at 120 VAC and 230 VAC
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00
POUT (W)
Efficiency (%)
Standby at 120 VAC: 20 mW
AM00898
Efficiency (%)
0.00
10.00
20.00
30.00
40.00
50.00
60.00
70.00
80.00
90.00
0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 4.00
POUT (W)
Standby at 230 VAC: 35 mW
10
11
12
13
14
15
16
0 20 40 60 80 100 120 140 160 180
IOUT (mA)
VOUT (V)
5 V / 50 mA
AM00899
10
11
12
13
14
15
16
020406080100120140160180
IOUT (mA)
VOUT (V)
5 V / 50 mA
5 V / 100 mA
5 V / 200 mA
5 V / 400 mA
5 V / 100 mA
5 V / 200 mA
5 V / 400 mA
120 VAC 230 VAC
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

Measurements UM0920
12/14 Doc ID 17220 Rev 2
Figure 7. EMI measurement for EN55022 Class B - AVG detector
Figure 8. EMI measurement for EN55022 Class B - peak detector
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

UM0920 Revision history
Doc ID 17220 Rev 2 13/14
5 Revision history
Table 3. Document revision history
Date Revision Changes
28-Jun-2010 1 Initial release.
03-May-2012 2
Replaced STEVAL-ISA071V1 by STEVAL-ISA071V2, updated
Figure 1 to Figure 4 and Disclaimer, minor text corrections
throughout document.
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.

UM0920
14/14 Doc ID 17220 Rev 2
Please Read Carefully:
Information in this document is provided solely in connection with ST products. STMicroelectronics NV and its subsidiaries (“ST”) reserve the
right to make changes, corrections, modifications or improvements, to this document, and the products and services described herein at an
y
time, without notice.
All ST products are sold pursuant to ST’s terms and conditions of sale.
Purchasers are solely responsible for the choice, selection and use of the ST products and services described herein, and ST assumes no
liability whatsoever relating to the choice, selection or use of the ST products and services described herein.
No license, express or implied, by estoppel or otherwise, to any intellectual property rights is granted under this document. If any part of this
document refers to any third party products or services it shall not be deemed a license grant by ST for the use of such third party products
or services, or any intellectual property contained therein or considered as a warranty covering the use in any manner whatsoever of such
third party products or services or any intellectual property contained therein.
UNLESS OTHERWISE SET FORTH IN ST’S TERMS AND CONDITIONS OF SALE ST DISCLAIMS ANY EXPRESS OR IMPLIED
WARRANTY WITH RESPECT TO THE USE AND/OR SALE OF ST PRODUCTS INCLUDING WITHOUT LIMITATION IMPLIED
WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE (AND THEIR EQUIVALENTS UNDER THE LAWS
OF ANY JURISDICTION), OR INFRINGEMENT OF ANY PATENT, COPYRIGHT OR OTHER INTELLECTUAL PROPERTY RIGHT.
UNLESS EXPRESSLY APPROVED IN WRITING BY TWO AUTHORIZED ST REPRESENTATIVES, ST PRODUCTS ARE NOT
RECOMMENDED, AUTHORIZED OR WARRANTED FOR USE IN MILITARY, AIR CRAFT, SPACE, LIFE SAVING, OR LIFE SUSTAINING
APPLICATIONS, NOR IN PRODUCTS OR SYSTEMS WHERE FAILURE OR MALFUNCTION MAY RESULT IN PERSONAL INJURY,
DEATH, OR SEVERE PROPERTY OR ENVIRONMENTAL DAMAGE. ST PRODUCTS WHICH ARE NOT SPECIFIED AS "AUTOMOTIVE
GRADE" MAY ONLY BE USED IN AUTOMOTIVE APPLICATIONS AT USER’S OWN RISK.
Resale of ST products with provisions different from the statements and/or technical features set forth in this document shall immediately void
any warranty granted by ST for the ST product or service described herein and shall not create or extend in any manner whatsoever, any
liability of ST.
ST and the ST logo are trademarks or registered trademarks of ST in various countries.
Information in this document supersedes and replaces all information previously supplied.
The ST logo is a registered trademark of STMicroelectronics. All other names are the property of their respective owners.
© 2012 STMicroelectronics - All rights reserved
STMicroelectronics group of companies
Australia - Belgium - Brazil - Canada - China - Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan -
Malaysia - Malta - Morocco - Philippines - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States of America
www.st.com
Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.Downloaded from Arrow.com.