Mean Well LRS-350-5 Power Supply
5V 60A · 300W rated · fan cooled · 215 × 115 × 30mm · UL 62368-1 · 3.35M hour MTBF

What the “350” in LRS-350-5 Actually Means: 5V 60A Is a 300W Supply

Most sourcing mistakes on this part happen before anyone opens a datasheet. The model number reads like a power rating, so a buyer assumes an LRS-350-5 is a 350W power supply, orders it for a screen that needs 340W, and finds out at commissioning that the supply is rated 300W. The confusion is baked into the naming: LRS-350 is the series, and the number after the dash is the output voltage, not the wattage.

The rated power of every model in the series, straight from the MEAN WELL specification table, shows why the “350” only holds at the top of the voltage range:

Every model in the series shares one 60A current ceiling at the low-voltage end. Power is current multiplied by voltage, so the same 60A that produces 350W at 48V produces only 300W at 5V. Nothing is defective or derated — that is simply how a constant-current-limited supply behaves across a voltage range.

How Many LED Modules Can One LRS-350-5 Power?

There is no single correct answer to this, and any supplier who quotes one without asking about your module is guessing. The answer depends on three numbers: the maximum power rating of your LED module (from the module datasheet, not from a marketing page), the number of modules on the supply, and the headroom you choose to leave.

Sizing runs in four steps:

1. Start from the supply’s real rating. 300W at 5V, which is 60A. Not 350W.
2. Apply a load ceiling. A common planning rule in LED cabinet builds is to keep continuous load at or below about 80% of the supply’s rated output — roughly 240W, or 48A, on an LRS-350-5. This is an engineering convention rather than a requirement published by MEAN WELL, so treat it as a starting point and confirm it against your project’s own thermal and warranty conditions.
3. Divide by the module’s maximum power. Use the maximum figure from the module datasheet, because a full-white test pattern is exactly the condition a screen is commissioned under.
4. Check the current path, not just the total. 48A has to leave through the terminal block and reach the modules. Confirm the wire gauge, the terminal rating and the number of feeds, then confirm the total against the cabinet’s own power distribution design.

Worked as an Illustrative Example — substitute your own module figures, these numbers are for the arithmetic only:

If the screen outgrows one supply, the usual approach is to split the cabinet into independently supplied sections rather than to parallel two LRS units — parallel operation is not a function this model provides. For the control and signal side of the same cabinet, the LED control system collection covers how sending cards, receiving cards and processors are powered and wired alongside the supplies.

Fan Cooling, Derating and Why 70°C Is Not a Working Target

Unlike the fanless UHP series, the LRS-350-5 is force-cooled. The datasheet specifies a fan on/off control function that switches the fan on at a heatsink temperature of 50°C or above and off again at 40°C or below. That hysteresis is deliberate: it keeps the fan from cycling on and off every few seconds around a single threshold.

In a display cabinet, that behaviour has a practical consequence worth planning for. The fan only runs when the supply is genuinely hot, which means a lightly loaded LRS-350-5 in a ventilated cabinet may run its fan rarely or not at all — and a screen that is silent at low brightness may spin up audibly when it goes full white. On a screen mounted in a quiet interior space, that is a specification the buyer should know about before installation, not after.

Reading the derating curve correctly

The working temperature range is −25 to +70°C, but the range is not flat. The published derating curve reduces the allowable output load as ambient temperature rises, and the curve is specified for horizontal mounting. Three things follow from that:

• Read the curve at your worst case, not your average. A cabinet in direct summer sun can sit well above the ambient the rest of the year. Size the supply at the curve’s value for the hottest condition the screen will actually see.
• Mount it the way the curve assumes. A supply installed on its side has a different thermal path than the horizontal orientation the curve is drawn for; do not assume the curve transfers unchanged.
• Derate again for altitude. The datasheet requires an additional ambient derating of 5°C per 1,000m for operation above 2,000m.

When the LRS-350-5 Is the Wrong Power Supply

A page that cannot tell you when not to buy something is a catalogue entry, not advice. The LRS-350-5 is the right answer for a large share of 5V LED cabinet work, and clearly wrong in the following cases:

Where the power supply is the wrong component to be choosing at all, the constraint is usually elsewhere in the system — module efficiency, cabinet thermal design or control architecture. On the indoor product side, pages such as the Mini COB LED display and the P3.91 rental LED display set out the module-level specifications those decisions start from.

LRS-350-5 Troubleshooting: No Output, Hiccup Mode and Fan Faults

Because three of this supply’s protections are hiccup-mode with automatic recovery, the same visible symptom — the screen blanks and comes back — can have several unrelated causes. Work through them in the order below; each step separates one cause from the others.

No output at all, and the fan does not run

• Possible cause: no mains reaching the supply, or the input voltage selector set for the wrong range.
• How to check: measure AC voltage across pins 1 and 2 at the terminal block. Then confirm the 115/230V switch position against the site voltage.
• Fix: correct the switch position, restore mains, and check the input fuse feeding the cabinet. If mains is present at the terminals and the selector is correct, the unit has failed and should be replaced rather than repaired in the field.

Output shuts down and recovers on its own, repeatedly

• Possible cause: overload (110–140% of rated power), over-voltage, or over-temperature protection engaging. All three use hiccup mode with auto-recovery, so all three look identical from the outside.
• How to check: measure the actual DC current with the screen at full white. Feel or measure the supply case and cabinet ambient temperature. A clamp meter plus a thermometer usually identifies which protection is firing.
• Fix: if the current is above the planning ceiling, split the load across an additional supply. If the cabinet is hot, fix the airflow — the supply is doing what it was designed to do, and a bigger supply in the same sealed box will simply get hot later.

Screen brightness drops or pixels discolour at the far end of a run

• Possible cause: voltage drop along the DC path, not a supply fault. At 5V, cable resistance takes a proportionally large bite out of the delivered voltage.
• How to check: measure voltage at the supply terminals and again at the input of the last module on the run. The difference is the drop.
• Fix: shorten the run, increase the conductor cross-section, or split the feed. Then trim the ADJ. potentiometer so the module input reads its specified 5V under load — not so the supply terminal reads 5V.

Fan runs constantly, or is unexpectedly loud

• Possible cause: sustained high load or high cabinet ambient keeping the heatsink above the fan’s on-threshold.
• How to check: confirm the datasheet behaviour — the fan is specified to switch on at RTH ≥50°C and off at ≤40°C. A fan that never stops means the unit is never getting back below 40°C.
• Fix: treat it as a thermal signal. Improve cabinet ventilation and confirm the load is inside the derating curve for the real ambient. Do not disconnect the fan; the over-temperature protection will shut the screen down instead.

Mean Well LRS-350-5: Frequently Asked Questions