Selecting power supplies and LED drivers

What this guide covers

A power supply or LED driver becomes part of another product. Its selection therefore depends on the host product as much as on the electrical load. This guide sets out the decisions in a typical order and the information each one needs. It prepares a design-in discussion; it does not confirm a design, which is agreed only after feasibility review and validation.

Constant current or constant voltage

A constant-current (CC) output holds a set current and lets the voltage follow the load. It suits LED modules and other loads whose current must be controlled. A constant-voltage (CV) output holds a set voltage and lets the current follow the load. It suits electronic loads and LED strips with their own current control.

CC/CV and custom power supplies are typically 10–600 W, with constant-voltage, constant-current or combined CC+CV outputs, typically 12–48 V DC. LED drivers are typically 10–200 W: constant-current drivers for LED modules, with output currents typically 0.35–3.5 A, and constant-voltage drivers at 12, 24 or 48 V DC for LED strips.

Define the load exactly

For an LED load, give the module current and the forward-voltage range of the LED string across temperature and production spread. The driver's output voltage window must cover the whole range; a driver that is correct at the nominal voltage can fall out of regulation at a cold start or with a different LED batch. State how many modules each driver feeds and whether they are in series or parallel.

For other loads, give the steady current, any peak or start-up current, and how the load behaves when it is switched or disconnected.

Input supply

Typical inputs are 100–240 V AC, 50/60 Hz. Where the product will be used on supplies that vary widely, run from generators, or sit at the end of long outdoor cable runs, say so: these conditions affect input protection and surge withstand.

Dimming and control

If the product needs dimming or control, name the interface the host product uses, the dimming range and the behaviour expected at low levels. Interfaces such as 0–10 V or 1–10 V, DALI, PWM and phase-cut are available on selected LED driver variants, and only the interface stated for a variant is supported. The interface is agreed during the design-in review; it should not be assumed from a general description.

Thermal and mechanical fit

Most early failures of power electronics come from heat. State where the supply or driver will sit, the space available, and how heat leaves the product. The ambient at the driver position inside a luminaire or enclosure is usually higher than the room ambient. Power supply formats include enclosed metal-case, open-frame, DIN-rail and potted designs; LED drivers are built-in, independent or sealed. LED drivers carry a marked case-temperature (tc) point, typically rated at 70–90 °C, which is the value to check in the luminaire. If the product is used outdoors or in damp areas, state the ingress protection the host product needs.

Approvals and responsibilities

State which approvals the end product needs and who will hold them. Agree early who owns product-level validation and integration, which samples are needed, and how the approved configuration will be controlled in production. These questions decide the programme as much as the technical design.

Volumes and continuity

Give expected volumes, the timing of prototype, pilot and production stages, and how long the product is expected to remain in production. This affects component choices and change notification.

Next step

Use the power supply and LED driver enquiry checklist and send the requirement through the enquiry form. The review records the requirement baseline, states any assumptions or departures, and proposes the next stage, usually a sample and validation plan.