108/757/DC For IEC use only 2021-07-16 INTERNATIONAL ELECTROTECHNICAL COMMISSION TECHNICAL COMMITTEE NO. 108: SAFETY OF ELECTRONIC EQUIPMENT WITHIN THE FIELD OF AUDIO/VIDEO, INFORMATION TECHNOLOGY AND COMMUNICATION TECHNOLOGY TC 108/WG HBSDT proposed draft IEC 62368-2, Ed. 4. _____________________________ Comments / proposals should be submitted using the IEC Electronic voting system by the National Committees. (See AC/3/2011). Comments/ proposals to be returned by 2021-09-24 – 2 – 108/757/DC 1 CONTENTS 2 0 Principles of this product safety standard ...................................................................... 14 3 0.5.1 General ......................................................................................................... 14 4 0.5.7 Equipment safeguards during skilled person service conditions ..................... 16 5 0.10 Thermally-caused injury (skin burn) ............................................................... 16 6 1 Scope ................................................................................................................................ 16 7 2 Normative references ......................................................................................................... 17 8 3 Terms, definitions and abbreviations .................................................................................. 17 9 4 General requirements ........................................................................................................ 20 10 4.1.1 Application of requirements and acceptance of materials, components 11 and subassemblies ........................................................................................ 21 12 4.1.5 Constructions and components not specifically covered ................................. 22 13 4.1.6 Orientation during transport and use .............................................................. 22 14 4.1.8 Liquids and liquid filled components (LFC) ............................................................ 22 15 4.2 Energy source classifications ................................................................................ 22 16 4.2.1 Class 1 energy source ................................................................................... 22 17 4.2.2 Class 2 energy source ................................................................................... 23 18 4.2.3 Class 3 energy source ................................................................................... 23 19 4.3.2 Safeguards for protection of an ordinary person ............................................ 23 20 4.3.3 Safeguards for protection of an instructed person .......................................... 24 21 4.3.4 Safeguards for protection of a skilled person ................................................. 24 22 4.4.2 Composition of a safeguard ........................................................................... 25 23 4.4.3 Safeguard robustness .................................................................................... 25 24 4.6 Fixing of conductors .............................................................................................. 26 25 4.7 Equipment for direct insertion into mains socket-outlets ........................................ 27 26 4.8 Equipment containing coin / button cell batteries ................................................... 27 27 4.9 Likelihood of fire or shock due to entry of conductive objects ................................ 27 28 4.10.3 Power supply cords .............................................................................................. 27 29 5 Electrically-caused injury ................................................................................................... 27 30 5.2.1 Electrical energy source classifications .......................................................... 29 31 5.3.2 Accessibility to electrical energy sources and safeguards .............................. 37 32 5.4 Insulation materials and requirements ................................................................... 38 33 5.4.2 Clearances .................................................................................................... 41 34 5.4.3 Creepage distances ....................................................................................... 53 35 5.4.4 Solid insulation .............................................................................................. 54 36 5.4.5 Antenna terminal insulation............................................................................ 57 37 5.4.6 Insulation of internal wire as a part of a supplementary safeguard ................. 57 38 5.4.7 Tests for semiconductor components and for cemented joints ....................... 58 39 5.4.8 Humidity conditioning .................................................................................... 58 40 5.4.9 Electric strength test ...................................................................................... 58 41 5.4.10 Safeguards against transient voltages from external circuits .......................... 59 42 5.4.11 Separation between external circuits and earth .............................................. 62 43 5.5 Components as safeguards ................................................................................... 62 44 5.5.6 Resistors ....................................................................................................... 65 45 5.5.7 SPDs ............................................................................................................. 65 46 5.5.8 Insulation between the mains and an external circuit consisting of a 47 coaxial cable ................................................................................................. 65 – 3 – 108/757/DC 48 5.6 Protective conductor ............................................................................................. 66 49 5.6.1 General ......................................................................................................... 66 50 5.6.3 Requirements for protective earthing conductors ........................................... 67 51 5.6.4 Requirements for protective bonding conductors ........................................... 67 52 5.6.5 Terminals for protective conductors ............................................................... 67 53 5.6.7 Reliable connection of a protective earthing conductor .................................. 67 54 5.7 Prospective touch voltage, touch current and protective conductor current............ 67 55 5.7.3 Equipment set-up, supply connections and earth connections ........................ 68 56 5.7.5 Earthed accessible conductive parts .............................................................. 68 57 5.7.6 Requirements when touch current exceeds ES2 limits ................................... 68 58 5.7.7 Prospective touch voltage and touch current associated with external 59 circuits ........................................................................................................... 69 60 5.7.8 Summation of touch currents from external circuits ........................................ 70 61 5.8 Backfeed safeguard in battery backed up supplies ................................................ 72 62 6 Electrically-caused fire ...................................................................................................... 74 63 6.2 Classification of power sources (PS) and potential ignition sources (PIS) ............. 74 64 6.2.2 Power source circuit classifications ............................................................... 74 65 6.2.3 Classification of potential ignition sources ..................................................... 77 66 6.3 Safeguards against fire under normal operating conditions and abnormal 67 operating conditions .............................................................................................. 78 68 6.3.1 Requirements ................................................................................................ 81 69 6.3.2 Compliance criteria ........................................................................................ 82 70 6.4 Safeguards against fire under single fault conditions............................................. 83 71 6.4.1 General ......................................................................................................... 83 72 6.4.2 Reduction of the likelihood of ignition under single fault conditions in 73 PS1 circuits ................................................................................................... 90 74 6.4.3 Reduction of the likelihood of ignition under single fault conditions in 75 PS2 circuits and PS3 circuits ......................................................................... 90 76 6.4.4 Control of fire spread in PS1 circuits .............................................................. 92 77 6.4.5 Control of fire spread in PS2 circuits .............................................................. 94 78 6.4.6 Control of fire spread in a PS3 circuit ............................................................ 96 79 6.4.7 Separation of combustible materials from a PIS ............................................. 97 80 6.4.8 Fire enclosures and fire barriers .................................................................... 99 81 6.5.1 General requirements .................................................................................. 105 82 6.5.2 Requirements for interconnection to building wiring ..................................... 106 83 6.6 Safeguards