Author
Angelo Fiorelli, Lineage Power Corp.
A power conversion device (PCD), although simple at first glance, is a complex device and a vital component of information technology and telecommunication products. Most original equipment manufacturers (OEMs) rely on the expertise of the PCD suppliers to provide the volts and amps required in making the products perform their intended function, but due to the technology used in switch mode power supply designs, the PCD can be the major contributor of emissions and can also be receptive to other forms of electromagnetic interferences (EMI).
Achieving system– level electromagnetic compatibility (EMC) compliance during the development process is critical for both the supplier and OEM, but what industry EMC guidelines does the PCD supplier need to meet in order to satisfy the OEMs qualification requirements? Historically, the OEMs created their own unique list of EMC specifications that the suppliers were required to meet, and since there has never been an industry-wide set of consistent requirements clearly defining the EMC objectives that the PCD manufacturer must adhere to, there has been confusion in the industry.
Beginning approximately two years ago, with the guidance of the Institute of Printed Circuits (IPC) organization, a group of top-tier OEM and PCD industry leaders teamed up to define a set of common requirements for power conversion devices. These efforts led to the creation of “IPC-9592 Requirements for Power Conversion Devices for the Computer and Telecommunications Industries”. This document was developed by the Power Conversion Devices Subcommittee (9-82) of the OEM Management Council Steering Committee (9-80) of IPC and was unveiled to the public on November 6, 2008 at a conference held in Irving, TX.
The intent of IPC standards is to “serve the public interest by eliminating misunderstandings between manufacturers and purchasers, facilitating interchangeability and improvement of products for his particular need.” [1]
The creation of the IPC-9592 document significantly reduces the communication gap between OEMs and suppliers, and for the first time standardizes and identifies the requirements for power conversion devices. IPC-9592 defines a set of consistent specifications and methods to assure suitability, quality, safety, and reliability for the electronic industry. It also sets the PCD’s requirements for the following criteria: 1) Design, 2) Qualification Testing, 3) Conformance Testing, 4) Manufacturing Quality / Reliability Process, and does not include the functional requirements of the specific equipment.
IPC-9592 contains seven sections and covers the following subject matter topics:
- Sections 1 and 2: Scope and Applicable Documents, Terms and Definitions
- Section 3: Product Specification and Documentation Requirements
- Section 4: Design and Reliability
- Section 5: Design and Qualification Testing
- Section 6: Quality Process
- Section 7: Manufacturing Conformance Testing
Although the IPC-9592 document includes many aspects of the PCD’s quality / reliability journey, this article will only address the EMC characterization of the PCD, and specifically focus on Section 5.3: “Electromagnetic Susceptibility (EMS) and other tests.”
A “power conversion device” refers to any ac to dc rectifier or dc to dc converters / embedded power and power supplies as defined within the IPC document. It is the first line of defense against many forms of electromagnetic interference (EMI) and must be designed as a robust component that serves as the heart of the system to which it is partnered. The PCD can be exposed to various electrical disturbances in the form of lightning, power line anomalies, transients, radio frequency disturbances, and ESD events. It can also be a source of electronic pollution in the form of conducted or radiated RF noise interference, including conducted power line harmonics. IPC-9592 has addressed these specifics by incorporating a list of EMI requirements to which each supplier must comply.
The document established two general classes of PCDs to help set evaluation test sample sizes and allow for different stress levels based upon the class of the PCD. The class types are identified as:
- Class 1: Includes general consumer computer, telecommunication products and peripherals which are designed to operate in controlled environments with up to five years of product life.
- Class 2: Centers around enhanced or dedicated systems such as carrier grade telecommunication equipment, network grade computers, sophisticated business machines and instruments where high performance and extended life are required. The product life cycle of a Class 2 device with limited excursions of uncontrolled levels and uninterrupted service is no less than five years and up to 15 years of service.
Three categories of PCD are further grouped and identified as:
- Category 1: Embedded PCDs with ac or dc input and dc output; a.k.a Packaged Power.
- Category 2: Board mounted dc to dc PCDs, either isolated or non-isolated.
- Category 3: Adapter or external PCDs with ac input and dc output.
Performance Levels of A through D, based upon the Test Severity Levels 1 through 4, are considered after the device has been tested. Listed below are descriptions of what performance levels A to D represent:
- Performance Level A: No effect. “Normal performance within limits specified by the manufacturer, requestor or purchaser.”
- Performance Level B: Temporary effect, self recovering. “Temporary loss of function or degradation of performance which ceases after the disturbance ceases, and from which the equipment under test (EUT) recovers its normal performance, without operator intervention.”
- Performance Level C: Needs help to recover. “Temporary loss of function or degradation of performance, the correction of which requires operator intervention.”
- Performance Level D: Damaged beyond recovery. “Loss of function or degradation of performance which is not recoverable, owing to damage of hardware, software, or loss of data.”[2]
IPC–9592 IMMUNITY REQUIREMENTS
One key instrumental decision that the committee made was to utilize existing International Electrical Commission (IEC) immunity documents rather that re-inventing new versions of the same test types. Section 5.3 is patterned after either EN 55024 or EN 300-386 and incorporates IEC 61000-4-XX series immunity documents as the methods and test levels for EMC compliance. Shown below is a listing of the immunity requirements for all Category 1 and 3 PCDs:
- IEC 61000-4-2: Electrostatic Discharge (ESD), (Packaged Power Devices)
- JESD22-A114: Electrostatic Discharge (ESD), (Board Mounted Devices (BMP), a.k.a Embedded Power)
- IEC 61000-4-3: Radiated Immunity (RI)
- IEC 61000-4-4: Electrical Fast Transient (EFT) Burst
- IEC 61000-4-5: Surge
- IEC 61000-4-6: Conducted Immunity (CI)
- IEC 61000-4-11: Voltage Dips, Short Interrupts & Voltage Variations
- IEC 61000-4-12: Ring Wave
The table below is a summary of the EMI immunity test types versus Category, Performance and Severity levels that are required for compliance with IPC-9592, Section 5.3.
IPC-9592 EMISSION REQUIREMENTS
All PCDs are subject to conducted and radiated emission analysis, and the test requirement for Category 1 and 3 devices is selected based upon the end user’s requirement, or AABUS. Although it was not identified as to what emission document to meet, the most logical standard is EN 55022. This would keep the theme for both immunity and emission analysis in line with internationally recognized and adopted EMI standards.
Category 2, dc to dc devices (BMP), are subject to meeting only conducted emission requirements per EN 55022 and the limit is again as agreed upon between user and supplier, AABUS.
Category 1, ac to dc PCDs, are subject to meet harmonic input current emissions and although the specific requirement is not defined, IEC 61000-3-2 (<16 A) or IEC 61000-3-12 (>16 A) is the inferred document to utilize for the harmonic analysis.
Table 2 is an overview of the EMI test requirements that have been included within the IPC-9592 document of Section 5.3. Most of these tests are already being performed by PCD manufacturers, but now there is a formal document written, so that during the OEM’s competitive selection process, only one document defines all the qualification requirements that the PCD manufacturers must meet.
Conclusion
IPC-9592 is a new and important standard for the PCD industry that covers various elements of the development, qualification, and quality processes for PCDs other than just the EMC aspect presented in this article. The initial release of the document utilizes IEC 61000-XX EMC standards and defines a consistent set of requirements that PCD suppliers must meet in order to aid the OEMs in making a comparative and educated decision during the supplier selection process.
Does this mean each supplier of PCDs will always meet the system-level EMC requirements of the OEMs? The answer is “No.” EMC engineers involved with the qualification process well know nothing is a sure bet when it comes to EMC compliance testing of a system. There will ultimately be minor set backs due to some unforeseen inherent problem between PCD and the system, but the document is an optimistic step in the right direction, and gives the OEMs an advantage at the start of their development process.
The IPC-9592 document is significant for both the OEM’s and suppliers because: 1) it finally defines a consistent set of PCD qualification evaluation criteria, including EMC, 2) it helps minimize the risk factor regarding EMC system level qualification testing, 3) suppliers can take pride in their product knowing that every effort was taken to provide a reliable component, 4) it simplifies the supplier selection process for the OEMs procuring department, 5) and it creates a bond of trust between OEMs and suppliers, which promotes open dialogue between each party and a future working relationship.
The theme communicated to everyone in attendance at the Irving, Texas conference was that IPC-9592 is a living document with the intent of starting with a seed, and growing this seed by input from industry leaders. The OEM team members that assisted in developing this document have already taken steps in implementing this new PCD qualification process, and the key to the future success of the document is to engage more talent to be part in the further refinement of IPC-9592. So that invitation is placed on the table for volunteers interested in getting involved and bringing the IPC document to the next level. Interested parties can contact Tom Newton at [email protected].
To purchase a copy of the IPC-9592 document, visit www.ipc.org
FOOTNOTE
Note (1): Taken from IPC-9592, Notice; document front page, inside cover.
Note (2): IPC-9592, page 5; Performance Level A, B, C, & D definition.
REFERENCES
IPC-9592 “Requirements for Power Conversion Devices for the Computer and Telecommunication Industries”, September 2008
Angelo Fiorelli holds a B.S degree in Electrical Engineering from Rochester Institute of Technology and has been working in the field of EMC for 30 years. He started with Spectrum Control Inc. in the capacity of an EMC Test Engineer, and later as EMC Laboratory Manager and custom EMI filter designer. He is currently working for Lineage Power (former divisions of Tyco Electronics and Lucent Technologies) in the capacity of EMC Qualification engineer. He can be reached by e-mail at [email protected].
