Your quoted paragraph is trying to cover rechargable battery operated equipment with external AC/DC convertors such as laptops, and integrated AC/DC convertors (can't think of an example): A product with a 20V DC input voltage is not is scope of LVD, but accompanying AC-DC convertor is. Having part of a system within the LVD (PSU) and part outside (VDU) doesn't really help you as the VDU still has to be "safe" so there isn't much benefit in considering under the GPSR rather than under the LVD
However....and its a big HOWEVER, there are a number of things that you should consider:
The EU guidance is "guidance" - it is not law.
Directives are implemented into the laws of the individual member states by their national goverments. The ONLY place that will give you a definitive answer as to whether something complies is a court.
You do not have a "CE approved" power supply - you have a power supply onto which someone has put a CE mark - there is no such thing as "CE approved".
You are reliant on the DC output voltage remaining safe under normal and single-fault conditions.
I strongly advise you ONLY to use a power supply that is:
- NRTL listed by someone such as UL, CSA, and current listing verified against UL/CSA certification database.
- Or, is certified by TUV, VDE, Nemko or other similar European mark and accompanied by a CB certificate or appears on their certification database.
Depending on the classification of the output voltage of the PSU, your LCD panel and its components will need to be assessed for a number of things including flamability, protection of user to hazardous voltages inside, component temperature rise, mechanical hazards.
Spend a few punds more and get a proper, "3rd party approved" PSU - e.g. MeanWell GS220A20-R7B , RS 679-6886, which is certified/recognised by UL and VDE: UL recognition QQGQ.E183223
- 5th line down...Switching Mode Power Supply, Model(s) GS220AX ( X = 12, 15, 20, 24, 48 )