A PSU certified to 60950-1 passes HIPOT test at 2121 V DC between PRI and earth. When it is used in an end product to be certified to 62368-1, does it need to withstand the end product HIPOT test that could be more than 2121 VDC, e.g., 2500 V DC?
Generally, no, as a Type test. Per 4.1.1 of IEC 62368-1, components complying with IEC 60950-1 are acceptable without further evaluation other than to give consideration to the appropriate use of the component in the end product.
Therefore, while there is the need to determine the need for an electric strength (Type) test per 22.214.171.124 on the end product if the end product contains any solid insulation designated Basic, Supplementary or Reinforced insulation, solid insulation in the PSU complying with the relevant requirements of 60950-1 is not required to be reassessed via Type test and brought into compliance with the 62368-1.
Please note that the electric strength test per 126.96.36.199 of 62368-1 is the Type Test for solid insulation. Therefore, the test requirements do not apply in general to insulation through the air, i.e., gaps complying with clearance and creepage distance requirements. There is no general “HIPOT test at 2121 V DC between PRI and earth” that is performed as a Type test in 62368-1, although there typically is a Production Line (Routine) test (at reduced ES test values) required per (EN) “IEC 62911, Audio, video and information technology equipment – Routine electrical safety testing in production,” and as a certification requirement of individual certifiers, including UL. These production line tests typically check for gross manufacturing defects, including miswiring errors, rather than recheck all specific insulation properties originally qualified via Type tests.
IEC TC108 interpretation panel question of 108/698/INF gives a guidance for component acceptance per 4.1.1 with some examples in various situations. Although this particular question was not addressed exactly, it will be helpful for further understanding of the application of 4.1.1, and the document is available through IECEE website - https://decisions.iecee.org/iecee/SearchCMC.nsf/de_h.xsp?v=iectc .
Finally, it should be noted that since the 4.1.1 provision for acceptance of components and subassemblies complying with the legacy standards was adopted for the purpose of smooth transition to the 62368-1 standard, and since EN 60065 and EN 60950-1 will be withdrawn in Europe as of December 20, 2020, legacy components as discussed above should be given consideration to be reassessed for compliance with the EN 62368-1 requirements within the given transition period (by the DOW of 2020-12-20 associated with EN 62368-1:2014). EN 60065 and EN 60950-1 no longer will be active EN standards as of this date.