Outdoor Signage Power Supply: 7 Specs That Decide Lifespan

Efficiency is the number everyone compares and the number that matters least. Going from 90% to 93% on a 200 W sign running 12 hours a day saves about 26 kWh a year — under $5 in most markets. Meanwhile a 200 mV difference in output ripple can pull LED lumen depreciation forward by three years. One of these shows up on the datasheet’s front page; the other is buried on page four.

Here are the seven specs that actually separate a two-year driver from a ten-year one.

1. Output Ripple (mV p-p)

Ripple is the AC residue riding on your DC output. It heats output capacitors from the inside and accelerates LED phosphor degradation.

• Under 150 mV p-p: acceptable for signage.
• 150–300 mV: expect shortened capacitor life.
• Over 300 mV: cheap design, usually a single-stage topology with undersized output caps.

Measure it with a Keysight DSOX1102G or any 100 MHz scope with the probe in ×10 and the ground spring attached — not the alligator lead, which adds enough loop inductance to double your reading.

2. Surge Rating and Repetition Tolerance

Look for 4 kV differential / 6 kV common mode per IEC 61000-4-5. Then ask the question the datasheet will not answer: how many 2 kV hits?

Outdoor signage sees dozens of small induced surges a year from nearby strikes and grid switching. A MOV that survives one 6 kV event and fails on the twentieth 2 kV event is worse than a properly sized one rated 4 kV with a documented 50-hit repetition test. This number is almost never printed — ask for it in the RFQ.

3. Inrush Current

A single 200 W driver can pull 40–60 A for 2–5 ms at cold start. Put thirty of them behind one contactor and you will weld the contacts or nuisance-trip the breaker within a season.

Specify inrush in the RFQ and either stagger switch-on with a time-delay relay or specify a soft-start (NTC thermistor) version.

4. Potting Depth and Compound

Potting keeps water out. Below 3 mm depth, thermal cycling opens micro-channels at sharp component edges where the compound debonds.

More important than depth is thermal conductivity: unfilled silicone is around 0.8–1.0 W/m·K; alumina-filled compounds reach 1.5–2.5 W/m·K. On a 200 W design that gap is worth roughly 6°C at the hotspot, which by the 10°C rule is worth roughly 40% of your capacitor life.

5. Capacitor Brand and Temperature Rating

Electrolytic capacitors are the first component to fail in a switching power supply — by a wide margin. Ask for brand and rating:

• 105°C / 10,000 h rated: what you want.
• 105°C / 2,000 h: consumer grade, will not see year five outdoors.
• 85°C rated: walk away.

The price difference between a Japanese 105°C/10,000 h capacitor and an unbranded equivalent is about $0.60 on a 200 W unit. That is the cheapest insurance available in this entire list. A factory using generic caps can quote 15% lower and still lose you five years of service life.

6. Operating Ambient Range, Not Storage Range

Datasheets sometimes quote storage temperature (-40 to +85°C) where you expected operating temperature. The operating range is what governs derating. Our standard outdoor units run -40°C to +70°C operating.

Watch cold start specifically: at -40°C, electrolytic ESR roughly triples, and a driver that starts fine at 25°C may hiccup or fail to start. If you are installing in Scandinavia, Canada or northern China, test a cold-start sample.

7. Warranty and RMA Terms

A “3-year warranty” means nothing without the RMA mechanics. Ask three questions: who pays freight, what is the response time to issue a replacement, and does the warranty start at shipment or at installation?

Ours is 3 years from shipment, replacement shipped within 48 hours of claim approval.

The Specs Nobody Prints

Four things you will have to ask for directly:

1. Repetition tolerance on surge (above)
2. Capacitor brand and hour rating
3. Potting compound thermal conductivity
4. Measured — not calculated — MTBF, and the standard it was derived from (MIL-HDBK-217F vs Telcordia SR-332 give very different numbers for the same circuit)

Three Things to Do on Delivery

1. Thermal image one unit at full load after 60 minutes. A Fluke TiS75+ will show you the hotspot. If the housing exceeds 70°C at 25°C ambient, the derating curve is optimistic.
2. Measure ripple on one unit with a scope.
3. Open one unit. Check potting coverage at the corners and the capacitor brand.

Download the spec template — a one-page RFQ sheet with all seven specs as fill-in fields, so every supplier quotes the same thing. → Get the template · See the full IP67 buyer’s guide