Over Power/Load Protection (OPP/OLP)
Over Power Protection (OPP) and Over Load Protection (OLP) are two different names for the same thing. This is an optional protection that shuts down the power supply in the case the unit starts delivering more power than a configured trigger point.
On low-end power supplies based on the half-bridge topology this protection is performed by the PWM controller integrated circuit – as long as it supports it, of course. On power supplies with active PFC circuit, this protection is implemented on the PFC controller.
In both cases what the circuit is really monitoring the total current pulled by the power supply from the power grid. If it increases above a certain value, the protection kicks in, shutting down the power supply.
Short-Circuit Protection (SCP)
Short-circuit protection is probably the oldest form of protection available, being very easy to implement (it is usual
ly implemented outside the monitoring integrated circuit using a couple of transistors). This is a required protection that will shut down the power supply in the case of any output to “short-circuit,” i.e., to touch the ground line (black wire), either accidentally or in case a component from the computer somehow burns.
No-Load Operation (NLO)
No-load operation is a required protection that allows the power supply to turn on and work correctly even if there is no load on its outputs. This is not exactly a “protection” like the ones we’ve seen so far, but more like a design requirement.