Questions for a power-supply supplier before validation

Validating a power supply inside a new product costs time: thermal runs, EMC tests, safety assessment, reliability checks and field trials. If the chosen supply later turns out to be wrong, or changes without notice after launch, that work has to be repeated. A structured set of questions before validation starts reduces that risk.

The questions below apply to standard and custom power supplies and to LED drivers supplied to an original equipment manufacturer (OEM).

Electrical fit

1. What are the input voltage range and frequency, and how does the unit behave at the edges of that range?
2. What is the output: constant voltage, constant current or both, and with what regulation and ripple at the load?
3. What is the inrush current at switch-on, and how many units can share one breaker?
4. What is the hold-up time if the input drops briefly?
5. What are the efficiency and power factor at the actual operating load, not only at full load?
6. Which protections are included: overcurrent, short circuit, overvoltage, over-temperature, and how does the unit recover from each?

Mechanical and thermal fit

1. What are the dimensions, mounting points and connector types, and are drawings controlled by revision?
2. What is the rated ambient temperature, and what is the derating curve above it?
3. Where is the case temperature measurement point, and what is its limit?
4. What cooling does the rating assume: free air, a heat-sink plate, or forced air?
5. What ingress protection is required for the installation?

Compliance

Ask which safety and electromagnetic compatibility standards the design is intended to meet for the target market, which tests have been carried out by whom, and which reports can be shared. Treat company-level certificates and product-level test reports separately: only the second applies to the unit being validated. For LED control gear in India, IS 15885 is a common reference; for other markets, the applicable standards differ.

Samples and validation status

• Are the samples from production tooling and processes, or from a prototype build?
• What has the supplier already verified, and under which conditions?
• Which results will the OEM need to repeat in its own product?

A sample built by hand can behave differently from a production unit. Validation results apply to the revision that was tested.

Production consistency

• How is each unit tested at the end of the line, and which parameters are recorded?
• How are units identified, and can a field unit be traced to its production batch and test record?
• Which critical components are single-sourced, and what happens if one becomes unavailable?

Change control

A power supply that changes after validation can change the OEM product's behaviour. Ask:

• What counts as a change requiring notification: components, suppliers, firmware, process, factory location?
• How much notice is given before a change, and are samples of the changed design provided for re-validation?
• How are revisions identified on the unit and in the documentation?

Agree these terms in writing before validation, not after the first change arrives.

Lifecycle and supply

• What is the expected production life of the design?
• What notice is given before a design is discontinued, and is a last-time buy offered?
• How are field failures analysed, and how are findings reported back?

Application support

• Who reviews the OEM's electrical and mechanical integration, and at which stage?
• Can the supplier review thermal measurements taken in the OEM product and comment on them?
• How are application questions and field issues raised, and how are answers recorded?

Clear routes for technical questions during validation avoid decisions made on assumptions.

Using the answers

Record the answers against the revision of the supply being validated. If an answer is not yet known, record that too, with an owner and a date. A supplier who can answer most of these questions in writing at the start is easier to validate and easier to live with in production.

Where to go next

• CC/CV & Custom Power Supplies
• LED Drivers
• OEM power solutions
• Start a design-in discussion: share the electrical, mechanical and validation requirements.