Power Supply Hold-Up Time: Define What Must Keep Running

Start with the equipment outcome

“Must survive a brief power interruption” is a useful project goal, but it leaves a supplier guessing about the actual requirement. Does the equipment need to continue its normal task, preserve a transaction long enough to stop, or restart in a controlled way after input power returns?

Ask the equipment owner and engineer to agree that outcome before purchasing compares power supplies. Record which functions must remain active and which may stop. A display remaining lit is not, by itself, evidence that the complete equipment met its operating requirement.

This guide helps buyers prepare a review brief. It supplies no universal interruption duration and makes no hold-up performance claim for a Voltivo Power model.

Separate hold-up time from the rest of the timing sequence

TDK-Lambda explains hold-up time as the short period during which the DC output remains regulated after an AC input interruption, using stored capacitor energy. Its examples show that the output load affects how long that energy lasts.

TDK-Lambda also distinguishes output timing characteristics, including turn-on delay, output rise and fall, and hold-up. Its discussion identifies input voltage, load, temperature and measurement criteria as relevant conditions.

Use these distinctions when reading a quotation. Ask the supplier to identify the beginning and end of the stated interval. Do not substitute a no-load observation or an output fall-time figure for the required loaded hold-up interval. The references explain principles and their own examples; their numbers are not specifications for another manufacturer's product.

Write a short interruption brief

Input event

Describe whether the requirement concerns complete input loss or a voltage dip. Have engineering specify duration, input conditions and the applicable event definition.

Essential load

List the circuits that must stay active and their load during the event. Identify any planned change in equipment mode.

Acceptable output

State the voltage range the equipment must receive and the point at which it is evaluated, using the equipment engineer's requirements.

Required outcome

Define whether normal operation, a controlled stop or another explicit behavior is required, and how the evaluator will recognize success.

Return of power

Describe the required recovery behavior and whether a reset or operator action is acceptable.

Keep unknowns marked for review. If several equipment variants have different essential loads, provide separate rows rather than averaging them. Include the normal configuration, cable arrangement and installation context so the proposal can be tied to a specific use.

Turn an ambiguous request into a reviewable one

Consider an illustrative terminal project. The initial request says that the terminal must not lose a transaction during a short interruption. Before choosing a supply, the team needs to decide whether the screen and accessories must keep operating or whether only a defined transaction-completion function must remain active.

The purchasing brief should capture the agreed choice, the associated load and the required interval supplied by engineering. Ask the supplier to respond against that brief, identify any exceptions and reference evidence for the proposed model. This is a planning example, not a customer case or a claim that a particular adapter can support either outcome.

If the proposal cannot meet the brief, request an engineering review of the power arrangement. Do not assume that choosing a higher wattage label alone resolves the requirement. Any alternative arrangement should be assessed as a complete proposal, with its configuration, cost and evaluation needs visible.

Close the evidence gap before ordering

Separate a datasheet commitment from a typical curve and from a result on one sample. Ask which conditions the supplied evidence covers, and which requested conditions still need evaluation. Have the responsible engineer agree the sample test plan and the equipment-level acceptance criteria.

Record the evaluated supply, load configuration, brief revision and decision together. If a future equipment revision adds an accessory or changes the required recovery behavior, route that change back for review instead of carrying forward the earlier acceptance automatically.

For a Voltivo Power discussion, send the output requirements, interruption brief, destination markets and estimated quantity. Include any required evidence or evaluation milestones. Hold-up capability, available documentation and the suitability of the proposed configuration must be confirmed during review.