The ability to sell external power supplies or led drivers types, around the world depends on meeting the relevant safety standards that apply in those territories. These standards are defined and administered by national or international agencies with various government-recognized testing laboratories able to certify compliance with such statutory regulations.

The primary goal of safety standards for power supplies used in electrical equipment is to protect against fire, electric shock and injury. Products meeting these requirements may be identified by a safety mark from the associated standards organization or by a mark indicating compliance with local legislation, within a defined economic area or trading zone.

SAFETY STANDARD TERMINOLOGY

Classes of Equipment

Safety standards identify different classes of equipment depending on how their power supplies, especially mains units, isolate secondary circuits and accessible parts from dangerous ac mains voltages:

Class I

Equipment achieves electric shock protection through basic insulation and protective earth grounding. This requires all conductive parts that could assume a hazardous voltage in the event of basic insulation failure to be connected to a protective earth conductor.

Class II

Equipment provides protection using double or reinforced insulation and hence no ground is required.

Class III

Equipment operates from a SELV (Safety Extra Low Voltage) supply circuit, which means it inherently protects against electric shock, as it is impossible for hazardous voltages to be generated within the equipment.

Understanding safety standards and the above classes of equipment requires a clear understanding of circuit definitions, types of insulation and other terminology used in relation to power supplies.

MAJOR SAFETY STANDARDS

The International Electrotechnical Commission (IEC) and the associated International Organization for Standardization (ISO) are the principle agencies responsible for electrical safety standards. Agencies such as Underwriters Laboratories (UL) and Canadian Standards Association (CSA) provide certification in North America, while similar bodies in Europe are Verband der Elektrotechnik (VDE), Technischer Überwachungs-Verein (TUV) and British Standards Institution (BSI). A product meeting an IEC standard such as IEC 60950 or the newer 62368-1 standard may be identified with the standard’s number prefixed instead by UL, CSA or EN (European Norm) to indicate the country where it is certified e.g. UL 1310 or EN 62368-1. Standards like these with the same numbers but different prefixes are sometimes referred to as “harmonized standards”. But while the IEC continues to pursue harmonization, regional differences remain and consequently products intended for multiple markets will need to show all of the required certifications.

UL/IEC/EN 62368-1

Audio/Video, Information and Communication Technology Equipment

The UL/IEC/EN 62368-1 safety standards represent an important transition from the 60065 and 60950-1 standards that currently govern companies marketing audio-visual products or computing/communications equipment in North America and the EU. As the distinctions between AV and ICT equipment become increasingly blurred with new technologies and markets, UL/IEC/EN 62368-1 is a unified replacement for the previous two standards. However, this transition is more significant than a simple merger or name change as UL/IEC/EN 62368-1 adopts fundamentally different engineering principles and terminologies, but like its predecessors, 62368-1 applies to both the end-user as well as to components and subsystems such as power supplies.

UL/IEC/EN 62368-1 ultimately aims to give designers more flexibility in product design and evaluation by implementing Hazard Based Safety Engineering (HBSE) principles that replace the traditional prescriptive approach. These HBSE principles seek to identify potential hazards as energy sources capable of causing pain or injury to others, while finding ways to prevent such energy transfer. This will support the introduction of new and innovative technologies without the standards first needing to be amended, and at the same time minimizing differences between national/regional variations of the standard.

The 2nd edition of UL/IEC/EN 62368-1 is the latest revision that has been accepted by the US, Canada, and EU. This new standard currently coexists with 60950-1 and 60065 to aid designers in the transition and includes several clauses to help companies manage legacy inventory of subsystems and components. However, the official adoption of 62368-1 remains on an uncertain timeline as the EU recently pushed its go live date from June 2019 to December 2020. As a result, UL has also pushed back its adoption timeline to December 2020 to harmonize with the EU. These changing timelines make it imperative for companies to continue to monitor the latest updates and news surrounding 62368-1, while beginning to familiarize themselves with the subtleties and differences between the new and legacy standards. By certifying products to 62368-1 now, companies can further their understanding of the current voluntary standards and avoid the rush to certify their products as the deadline inches closer.

UL/IEC/EN 60950-1

Safety of Information Technology Equipment

IEC 60950-1 consolidates the 2005 2nd edition of this standard with its first and second amendments (from 2009 and 2013 respectively). The standard is applicable to mains, or battery-powered information technology (IT) equipment and office machines with a rated voltage not exceeding 600 V. It is intended to prevent injury and damage to persons and property from such hazards as electric shock, fire, dangerous temperatures and mechanical instability. Note that in Germany this standard is also referenced as DIN EN 60950-1 and as VDE 0805.

UL/IEC/EN 60065

Safety of Audio, Video and Similar Electronic Apparatus

UL/IEC/EN 60065 is intended to protect against fire, electric shock and injury, this time in respect to audio, video and similar equipment, including such examples as video projectors and electronic flash units for photographic purposes. As with the standards already discussed, not all of the protective measures are applicable to power supplies but those that relate to shock and fire require similar precautions with respect to insulation, isolation, limiting voltage and/or current, and measures to increase resistance to fire. IEC 60065 references other standards such as: UL/IEC/EN 60950-1 for SELV voltage limits, TNV (Telecommunication Network Voltages) for equipment that is not connected to the mains and UL/IEC/EN 60695-11-10 for component flammability categories.

IEC 60601-1

Safety of Medical Electrical Equipment

IEC 60601-1, which covers the basic safety and essential performance applicable to medical electrical equipment including surgical, monitoring and hospital devices, has a long history with a number of revisions. The standards follow the same general requirements established in IEC 60950-1, but with increased levels of protection for insulation/isolation, creepage, clearance, and leakage current.

Introduced in 1988, the 2nd edition of IEC 60601-1 focused on safety within a 6-foot radius of the patient known as “patient vicinity” and developed three guidelines of increasing severity. This was followed by the 3rd edition in 2005 which looked at different “means of protection” (MOP) for patients and equipment operators. Edition 3.1, introduced in 2012, made over 500 changes and clarifications to the 3rd edition to address ambiguities arising from evolving medical technology. Most recently, in 2014, the 4th edition of collateral standard IEC 60601-1-2, “Electromagnetic disturbances – Requirements and tests,” was published.

IEC 60335

Safety of Electrical/Electronic Household Appliances and Similar Applications

IEC 60335-1 is part 1 of an international standard that covers the safety requirements for devices with rated voltages up to 250 V for single phase and up to 480 V for multi-phase, that are intended for household appliances and similar applications. In addition to the general requirements of part 1, there is a part 2 of the standard which sets additional requirements for some specific device types. Due to the variety of appliances that may be found in a household, over 100 device types have been called out in part 2.

In North America, IEC 60335-1 has been used as the basis for a tri-national standard between the United States (UL 60335-1), Canada (CAN/CSA-C22.2 No. 60335-1), and Mexico (NMX-J-521/1-ANCE). In the US, UL 60335-1, which is in its 6th edition, is harmonized to IEC 60335-1 as part of its participation in the HOUS category of the IECEE CB Scheme. However, the United States does not recognize all of the part 2 standards. The part 2 requirements take precedence over the general requirements laid out in part 1.

The European standard is EN 60335-1 and defines how appliances may comply with European directives, such as the low voltage directive. Unlike the United States, the EU recognizes most, if not all, of the 100+ part 2 standards related to specific products.

IEC/EN 61558

Safety of transformers, reactors, power supply units and combinations thereof - Part 1: General requirements and tests

IEC 61558-1 is also available as IEC 61558-1:2017 which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.

IEC 61558-1 deals with safety aspects of transformers, reactors, power supply units and combinations thereof such as electrical, thermal and mechanical safety. This document covers the following independent or associated stationary or portable types of dry-type transformers, power supply units, including switch mode power supply units, reactors and combinations thereof in the field of safety. The windings can be encapsulated or non-encapsulated. They are not forming a part of the distribution network. This third edition cancels and replaces the second edition published in 2005 and Amendment 1:2009. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:

a. fully insulated winding wires (FIW), new tables and aging tests for FIW constructions,

b. overvoltage categories 1, 2, 3 and 4 for clearances and dielectric strength tests (new tables) are included,

c. development of new symbols for the different overvoltage categories,

d. symbol for maximum altitudes, if higher than 2 000 m,

e. symbol for plug in power supply units, if the pins are damaged (tumbling barrel test),

f. symbol for minimum temperature (even during the transportation),

g. alternative temperature measurement, simulated load and back to back method according to IEC 60076-11,

h. short circuit and overload protection, simulated load and back to back method according to IEC 60076-11,

i. adjustment of temperatures in Table 2 according to CENELEC Guide 29,

j. establishing partial discharge test above 750 V for FIW constructions,

k. requirements for toroidal core constructions, division for basic and for supplementary isolation,

l. modification of protection indexes for enclosures (IP-code),

m. dimensioning of rectangular cross section connectors for transformers,

n. repetition test, 80% of required dielectric strength test voltage of Table 14,a.

o. vibration test for vehicles and railway applications,

p. two Y1 Capacitors for working voltages above 250 V and not exceeding 500 V with overvoltage category 3.

It has the status of a group safety publication in accordance with IEC Guide 104.

UL 1310

Safety Requirements for Class 2 Power Units

UL 1310 specifies requirements covering indoor and outdoor use Class 2 power supplies and battery chargers in applications such as lighting systems, machinery and other appliances installed in residential and industrial environments. These units utilize an isolating transformer and other components to provide either ac or dc outputs, subject to a maximum rating of 42.4 Vac peak or 60 Vdc. The standard is aimed at products that primarily power low voltage, electrically operated devices including:

Portable or semi-permanent direct plug-in units with 15 A blade connections for use on nominal 120 or 240 Vac mains circuits.

Cord and plug-connected units with a 15 or 20 A plug for 120/240 Vac mains supply.

Units permanently connected to an input supply nominally of 600 Vac or less.

Direct plug-in and cord-connected units also include dc powered supplies operating from a vehicle battery via a cigarette lighter or equivalent dc connector or from a data port associated with information technology equipment. These units are also limited to a maximum input power of 600 W.

The safety requirements of UL 1310 are defined in terms of:

Enclosure strength and rigidity to resist likely abuses.

Built-in over current and over-temperature protection devices.

A maximum potential of 42.4 Vac peak / 60 Vdc for exposed wires / terminals.

Protection from “backfeed” voltage.

Other aspects covered by the standard include: packaging, corrosion, switches, weight, dc cabling, mounting, connections, strain relief, operating temperature, humidity and environment (indoor and outdoor).

UL 8750

Light Emitting Diode (LED) Equipment for Use in Lighting Products

1.1 These requirements cover LED equipment that is an integral part of a luminaire or other lighting equipment. These requirements cover components including LED drivers, controllers, arrays (modules), and packages as defined within this standard.

1.1.0 LED equipment covered by this standard are intended for operation in the visible light spectrum between 400 - 700 nm. Coherent light sources (e.g. laser sources) are not covered by this standard.

Exception No. 1: LED packages as described in Supplement SD may have applications other than general illumination and may operate outside of the visible light spectrum.

Exception No. 2: Special Use LED arrays as described in Supplement SJ have intended applications other than general illumination and may operate outside of the visible light spectrum.

1.1.3 These requirements do not cover LED controllers within the scopes of the following standards:

a) Standard for Safety for Plug-In Locking Type Photocontrols for Use with Area Lighting, UL 773, or

b) Standard for Safety for Solid-State Dimming Controls, UL 1472.

1.2 These lighting products are intended for installation on branch circuits of 600 V nominal or less in accordance with the National Electrical Code (NEC), ANSI/NFPA 70, and for connection to isolated (non-utility connected) power sources such as generators, batteries, fuel cells, solar cells, and the like.

1.3 LED equipment is utilized in lighting products that comply with the end-product standards listed below. The requirements in this standard are intended to supplement those in other end-product standards. Included are:

a) Electric Signs, UL 48,

b) Portable Electric Luminaires, UL 153,

c) Underwater Luminaires and Submersible Junction Boxes, UL 676,

d) Emergency Lighting and Power Equipment, UL 924,

e) Stage and Studio Luminaires and Connector Strips, UL 1573,

f) Track Lighting Systems, UL 1574,

g) Luminaires, UL 1598,

h) Direct Plug-In Nightlights, UL 1786,

i) Low Voltage Landscape Lighting Systems, UL 1838,

j) Self-Ballasted Lamps and Lamp Adapters, UL 1993,

k) Luminous Egress Path Marking Systems, UL 1994, and

l) Low Voltage Lighting Systems, UL 2108.

1.4 The requirements in this standard do not anticipate additional construction, performance and marking considerations for the following end-applications: LED equipment subject to weather (outdoor use), LED equipment installed in air handling spaces or in other environmental air spaces (plenums), LED equipment intended for Emergency Lighting and Power Equipment, LED equipment with integral batteries (and battery packs), and LED equipment used in fire rated installations. LED equipment with such end-applications is subject to additional evaluation per applicable standards.

IEC/EN 61347

Lamp controlgear - Part 1: General and safety requirements

IEC 61347-1:2015 is available as IEC 61347-1:2015 RLV which contains the International Standard and its Redline version, showing all changes of the technical content compared to the previous edition.

IEC 61347-1:2015 specifies general and safety requirements for lamp controlgear for use on d.c. supplies up to 250 V and/or a.c. supplies up to 1 000 V at 50 Hz or 60 Hz. This third edition cancels and replaces the second edition published in 2007, Amendment 1:2010 and Amendment 2:2012. This edition constitutes a technical revision. This edition includes the following significant technical changes with respect to the previous edition:

a) additional marking requirements;

b) additional requirements for creepage distances and clearances:

- for working voltages with operating frequencies up to 30 kHz;

- for working voltages with higher operating frequencies than 30 kHz;

- for impulse and resonance voltages ignition;

- for basic, supplementary and reinforced insulation;

- for insulation between circuits;

- for coated or potted controlgear;

c) modification of definition of ELV and FELV;

d) modification of schematic drawing, showing the different controlgear classification and insulation requirements;

e) scope extension;

f) new Annex A: test to establish whether a conductive part is a live part which may cause an electric shock;

g) new Annex M: creepage distances and clearances for controlgear where a higher degree of availability (impulse withstand category III) may be requested;

h) new Annex Q: example for Up calculation;

i) new Annex P: creepage distances and clearances and distance through isolation (DTI) for lamp controlgear which are protected against pollution by the use of coating or potting;

j) new Annex R: concept of creepage distances and clearances.

For more information on Switching Power Supplies/LED Drivers and Efficiency Standards for External Power Supplies/LED Drivers, welcome to contact KSPOWER sales representative power15@szzhpower.com>.