ST VIPer12A-E User Manual

November 2007 Rev 4 1/17
AN2544
Application note
Designing a low cost power supply using a
VIPer12/22A-E in a buck configuration
Introduction
Many appliances today use nonisolated power supply to furnish low output power required
to run a micro, LED display, and a few relays or AC switches. This type of power supply has
a single rectifier so as to reference the neutral to output ground in order to fire TRIACs or AC
switches. This article describes the use of the VIPer12A-E and the VIPer22A-E which are
pin-for-pin compatible and can supply power for many applications. This paper provides an
off-line, nonisolated power supply evaluation board based on the VIPer12/22A-E. Four
different examples are covered. The VIPer12A-E is used for 12 V at 200 mA and 16 V at 200
mA. The VIPer22A-E is used for 12 V at 350 mA and 16 V at 350 mA. The same board can
be used for any output voltage from 10 V to 35 V. For outputs less than 16 V, D6 and C4 are
populated and W1 is omitted. For outputs greater than 16 V, D6 and C4 are omitted and W1
is populated. For more design detail, see AN1357 "VIPower: low cost power sullies using
the VIPer12A-E in nonisolated application." The objective of this application note is to
familiarize the end user with this reference design and to quickly modify it for different
voltage output. This design gives:
■ Lowest possible component count
■ Integrated thermal overload protection
■ About 200 mW at no-load consumption
■ Efficiency measured between 70% to 80% at full load
■ Integrated Short circuit protection
Figure 1. Evaluation board (STEVAL-ISA035V1)
Table 1. Operating conditions for the four samples
Board version (with changes) Output voltage and current
Input voltage range 85 V
ac
to 264 V
ac
Input voltage frequency range 50/60 Hz
Output version 1 VIPer22ADIP-E 12 V at 350 mA 4.2 W
Output version 2 VIPer12ADIP-E 12 V at 200 mA 2.4 W
Output version 3 VIPer22ADIP-E 16 V at 350 mA 5.6 W
Output version 4 VIPer12ADIP-E 16 V at 200 mA 3.2 W
www.st.com

ST VIPer12A-E Specifications

General

Max Output Current	0.4 A
Input Voltage Range	9 V to 38 V
Switching Frequency	60 kHz
Operating Temperature	-40°C to 150°C
Topology	Flyback
Output Voltage	Adjustable
Package	SO-8
Output Power	Up to 8W
Protection Features	Overload, Overvoltage

Summary

Circuit Operation

Input Line Rectification and Filter

Describes input line rectification and EMI filtering for the converter.

Startup Circuit Operation

Explains the VIPer's startup sequence, Vdd capacitor charging, and shutdown thresholds.

Inductor Selection

Provides a formula for selecting the inductor for discontinuous mode operation.

Design Example

Illustrates circuit configuration for 12V and 16V outputs using the evaluation board.

Design Hints and Trade-offs

Discusses inductor value selection and its impact on peak current and losses.

Board Layout

Details the physical layout of the double-sided evaluation board.

Burst Mode Operation

Explains operation at light loads where pulses are skipped for regulation.

Short Circuit Behavior

Describes the VIPer's pulse-by-pulse current limit and behavior during a short circuit.

Performance Metrics

Presents regulation, ripple, and efficiency data for different operating conditions.

EMI Conducted Testing

Details EMI testing results for the different circuit versions.

Conclusion

Revision History