IEC Requirements for USB

Different countries have different reference standards for the rules of imported extension sockets. This article focuses on the IEC rules for extension sockets with USB power supply.

Late last year, the IEC published the standard IEC 60884-3-1:2021 "Plugs and sockets for household and similar uses - Part 3-1: Special requirements for sockets with USB power supply".

This requirement applies to fixed or portable sockets that are used for AC power only. It is important to note that this requirement is for AC power and does not apply to DC power sockets. In addition to the applicable requirements mentioned above, sockets need to be with or without earth contact, rated at a voltage greater than 50 V but not exceeding 440 V, rated at a current not exceeding 32 A, for indoor and outdoor, domestic and similar uses, with a USB power supply.

Attentions.

1. New clause 101 abnormal conditions:

In abnormal conditions, the USB power supply shall not create any danger. This means that there are safety requirements for USB power supplies under abnormal conditions.

The clause also has a numerical specification of the criteria for meeting the abnormal condition. That is, if the maximum consumption of the USB power supply does not exceed 0.5 W in the event of a fault, the requirements of the abnormal situation are deemed to be met.

Compliance is checked by means of the tests specified in 101.2 and 101.3. Note Clause 101 For these tests, additional specimens may be required. Compared to the previous tests, the new test requirements for the USB section require the supplier to confirm the number of test samples and prepare them in advance.

2. Temperature rise under abnormal conditions

• When a USB power supply is operated under abnormal conditions, no component can reach temperatures so high as to create a fire hazard to its surroundings.

• Compliance is checked by conducting a heating test on the USB power supply under fault conditions.

3. Fault condition test

• Short-circuit across creepage distance and clearance in other cases than those specified below. If they are less than the experimentally required values, the testing requirements requirements are met.

• Short-circuit across the insulating coating of the composition. These coatings are ignored when assessing creepage distances and clearances, e.g. lacquer or enamel.

• If a fault condition simulated in the test affects other fault conditions, all these fault conditions are applied simultaneously.

• Gaps, creepage distances and components providing reinforced or double insulation, such as double-insulated transformers, Y1 capacitors, optocouplers or similar, must not be short-circuited when applying abnormal conditions.

• If the temperature of the USB power supply is limited by the operation of an automatic protection device (including fuses), the temperature is measured after the device has been in operation for 2 minutes.

• If the temperature is limited by the automatic protection device or the fuse, in case of doubt the following additional test should be carried out: the fuse is short-circuited and the current under the relevant fault condition is measured.

New clause 102 Special requirements for USB power circuits.

According to the requirements listed in IEC 62368-1:2018 and lEC 62368-3:2017 in 102.3.2 and 102.3.3 respectively, USB power supply circuits shall comply with the following requirements:

Compliance is checked by subjecting new samples to the tests listed in IEC 62368-1:2018 and IEC 62368-3:2017, 102.3.2 and 102.3.3.

It is permitted to test the usb module or circuit separately before final assembly, if the insulation is damaged during the final assembly of the accessory. The given test voltage is the minimum test voltage to be applied. Higher voltages are permitted at the manufacturer's discretion if the insulation is not damaged by the excessive voltage applied. USB port poles (including earth) of live parts that could become dangerous together in the event of an insulation fault, e.g. due to incorrect assembly, faulty parts or similar results.

The test voltage is applied between the power terminals or module conductors connected together with the USB port poles (including ground) and may become a dangerous live part in the event of an insulation fault, e.g. due to incorrect assembly, faulty components or similar.

This new regulation issued by the International Electrotechnical Commission is a good reference standard for testing the quality of the increasingly popular mopboards with USB charging ports on the international market. For purchasers, they also need to pay attention to the supplier's corresponding product process improvements, laboratory tests, etc. when purchasing, so that the quality of imported products can be more assured.