240v @13A A.C. =( 120v, 13A)=(120/5 USB @13A or (120/5@ 13x4)= 24x4 USB @ 3.1A . So power supplies need to get a lot more efficient.

 

Hi Yen,
Do you have a question?

Moderation

 

I agree, if you have designed a power supply that draws 13A at 240V and outputs 120/5 V at 13A, you do need to improve the efficiency.

 

Power supply efficiency should always be improving. But that does not relate to the first sentence in post #1, as I see it. One more comment is that as far as I see it, USB powering stuff is usually less efficient BECAUSE of the voltage drop in the skinny wire used. In addition, usually the primary goal in the USB supplies zi see is #1 Minimum cost to produce #2 is the smallest possible size. Neither of those goals coincide with best efficiency.

 

You need to compare watts, not amp or voltage.

240 V x 13 A = 3120 W

What are you doing that draws 3 kW?

 

UK outlets uses 230V 13amp sockets, they come with a fuse in the plug,

 

IT certainly looks like the TS IS NOT an engineer with any understanding of electrical laws and relationships. Nor much of an understanding about power.
Perhaps the TS will return and explain what is attempting to be communicated in that first post.

 

I think he might be under the impression that anything powered by a 240 outlet rated at 13A will always use 13A x 240V = 3120W.

 

I think he might be under the impression that anything powered by a 240 outlet rated at 13A will always use 13A x 240V = 3120W.

It must confuse him that generally there are about a dozen 13A sockets wired to a single 32A breaker.

 

power supplies need to get a lot more efficient.

No, they don't.

You are equating the max current allowed with the current actually drawn. This is incorrect. A USB wall wart supplying 5 V / 1 A to a device does not draw 13 A from the mains.

ak

 

Actually, improving the efficiency of power supplies is often good. Probably the term "NEED" is a bit excessive.
Consider all if those who show up here deeply concerned that their 5 amp supply will damage a device that only requires one amp. Certainly there is a shortcoming in our education at an early level.