Protection Modes: OCP, OVP and What Happens After a Fault

Nearly every datasheet lists over-current, over-voltage and over-temperature protection, and it is easy to read that as a box ticked. The useful question is not whether a supply protects itself, but what it does once the fault goes away — because that is what decides whether your equipment comes back on its own at three in the morning.

The three trips

• OCP (over-current) — the output is drawing more than the supply will deliver, usually set somewhere around 105–150 % of rated current.
• OVP (over-voltage) — the output has risen above a safe ceiling, typically 115–135 % of nominal. This is the one protecting your load rather than the supply.
• OTP (over-temperature) — the internal heatsink or transformer has exceeded its limit, often because airflow is blocked or the unit is being run hard in still air.

Recovery is the part that bites

Three behaviours are common, and the words appear on the datasheet if you look for them:

• Hiccup — the supply shuts down, waits, and retries continuously. Clear the fault and it restarts by itself, with very little heating while it waits. This is usually what you want in unattended kit.
• Constant current or foldback — the output holds up but the voltage sags to whatever the load will take. It rides through brief overloads without dropping out, at the cost of dissipating real power for as long as the fault lasts.
• Latch-off — the supply shuts down and stays down until the mains is recycled. Safe and unambiguous, and thoroughly inconvenient if the unit is up a mast or in a locked cabinet.

Where it catches people out

A large capacitive load looks like a short at switch-on, so a supply in hiccup mode can retry indefinitely and never start — the symptom is a healthy unit that ticks quietly and never comes up. OVP is almost always latching, so a nuisance trip needs a mains cycle. And OTP that keeps re-tripping is telling you about the enclosure, not the supply.

Browse the AC/DC range or ask us which protection behaviour a given model uses.