Constant Voltage or Constant Current? 4 Parameters That Decide Your LED Driver Choice

Flicker, dead units, failures within six months — eight times out of ten the root cause is not driver quality but a wrong choice made at selection stage.

No theory, no formulas. This guide covers the four parameters you must lock down before ordering, backed by live data from the 47 models we currently stock. Work through them in order.

1. Constant voltage or constant current: read the luminaire nameplate

One-sentence rule: if the nameplate states a voltage (e.g. DC24V), you need a CV driver; if it states a current (e.g. 700mA), you need a CC driver.

• Constant voltage (CV): fixed output (12V / 24V / 48V), current determined by the load. LED strips, tape light, signage modules and most finished luminaires. 46 of our 47 models are CV.
• Constant current (CC): fixed output current, voltage self-adjusts across a range. Bare emitters — spotlights, track lights, COB modules — must use CC, or the LEDs will over-current and burn. Our H19 is a CC model.

The most common mistake is wiring a CV driver straight to a bare emitter. With no current-limiting circuit on board, current runs away. If you cannot see a driver module or PCB inside the luminaire, assume CC.

2. Voltage and wattage: prefer 24V, rate at 80%

Our current output-voltage spread: 24V (44 models), 12V (32 models), 48V (6 models). The choice is not arbitrary:

• Prefer 24V. At equal power, 24V draws half the current of 12V, so voltage drop along the run is far smaller. A 10-metre strip on 12V is often "bright at the head, dim at the tail" — the same strip on 24V stays even.
• 48V suits very large installations that need current pushed even lower — we carry 6 models.
• Always leave power headroom: divide total luminaire wattage by 0.8. A 240W strip load calls for a 300W driver.

Why 80%? A driver running continuously at full load runs hot, and electrolytic capacitor life is extremely sensitive to temperature — full-load operation shortens it noticeably. Inrush current at power-on can also trip protection on a marginally rated unit. Every YFX datasheet states "keep load within 80% of rated output". That is not conservatism; it is cheaper maintenance.

But bigger is not better either. Below 30% load, both efficiency and power factor drop. The ideal operating window is 50–80% of rated power.

3. Dimming protocol: the change-order king — fix it before renovation

This is the most overlooked, most expensive item in real projects. The wall is closed, the ceiling is finished — and only then does the panel turn out not to match the driver. At that point you either chase walls or give up dimming.

The protocols we support, and where each fits:

• Triac / phase-cut (8 models): works directly with traditional wall dimmers — ideal for retrofits where rewiring is not an option. Typical models: K01, H01.
• 0-10V (14 models): the workhorse of commercial projects — moderate cost, rock-stable, needs one extra pair of low-voltage wires. Offices, retail chains, shops.
• DALI (13 models): the only protocol with individual addressing — every fixture has its own address, enabling grouping, scenes and building-management integration. Hotels, exhibition halls and premium commercial spaces almost always specify it. Typical models: H01, H02, H03.
• PWM (5 models): PWM dimming, a good fit for dimmable LED strip scenes.
• Bluetooth / ZigBee (1 model): wireless, for finished spaces where no new cabling is possible.

One-line guidance: new-build hotel or premium commercial — specify DALI up front. Retrofit or residential — first confirm what is already in the wall. Chain retail — 0-10V is usually the best value.

4. IP rating: IP20 indoors, IP65+ wherever it rains

First digit = dust, second digit = water. Read both, not just the number:

• IP20: dry indoor locations (cove lighting, wardrobes, above ceilings). We stock 30 models.
• IP44: splash-proof — bathrooms, kitchens, balconies and other semi-exposed spots.
• IP65 / IP67: the starting point for anything outdoors. IP65 withstands water jets; IP67 survives temporary immersion. We carry 12 outdoor models, e.g. H03 and X04 (200–1000W, façade and architectural lighting) and S06 (600–1000W, common in landscape and garden projects).

One warning: IP54 is not jet-proof. Many budget "waterproof" products carry IP54, which only handles splashes — driving rain or hosing down a façade will get water inside. For outdoor architectural lighting, always confirm the first digit.

Outdoor installations also need heat dissipation room. A frequent failure mode: the driver sealed inside a fully enclosed metal box that hits 70°C in summer. Potted IP65 units dissipate heat worse than indoor models — step up one power class rather than cooking it in a small box.

5. The one-minute pre-order checklist

1. Does the luminaire nameplate state V or mA? → CV or CC
2. Total load? ÷ 0.8 = the wattage to order
3. Dimming required? Can the wall carry the wires? → protocol
4. Where does it mount? Will it get rained on? → IP rating

Once these four are settled, power class, dimensions and packing are all negotiable details. The expensive mistake is buying drivers first and reworking the plan afterwards.

If you have a fixture list or site photos, call / WhatsApp +86 138 2356 2421 — we will match model, wattage and protocol for every channel in one pass, so you do not have to go back and forth.