AC/DC Power Supplies – 12 V and 24 V

12 V or 24 V power supply: rectified or switch-mode?

An AC/DC power supply – also called an AC/DC converter or a DC power supply transformer – turns 230 V AC mains into direct current. Our range uses two technologies, and the right one depends on what you are powering.

• Rectified power supplies combine a single-phase transformer, which steps the 230 V down, with a bridge rectifier mounted on a heat sink. The output is DC but unfiltered. These 100 to 1,000 VA units cope well with short overloads and generate little high-frequency interference, which makes them suitable for motors, electromagnets, solenoid valves, automation or battery charging through a charge controller.
• Regulated switch-mode power supplies hold their output voltage whatever the load (12 V within ±3 to 5%). They are the choice for LED strips, cameras and sensitive electronics: a compact 60 to 200 W 12 V DC power supply, or an IP67 waterproof version from 60 to 300 W.

A key point with rectified models: their voltage depends on the current drawn. With no load, a 230 V to 12 V power supply reads about 17 to 18 V and a 230 V to 24 V power supply about 34 to 36 V; the voltage falls to 12 V or 24 V at rated power. If your equipment needs a strictly constant voltage, choose a switch-mode unit.

How much power do you need?

Start from the current: equipment power in watts ÷ voltage = current in amps. Then add headroom:

• +20% for ordinary loads;
• at least +30% for motors and inductive loads, allowing for the inrush current at start-up;
• for a switch-mode LED power supply, running it at about 80% of its rating extends its service life.

Example: a 300 W, 12 V motor draws 300 ÷ 12 = 25 A. With headroom, the 400 VA (33 A) model gives a comfortable margin. The rectified 12 V range has seven ratings from 100 VA (8 A) to 1,000 VA (84 A); the 24 V range runs from 100 VA (4 A) to 1,000 VA (42 A). Avoid heavily oversizing a rectified unit, though: at part load its voltage stays above nominal.

IP00, IP23, IP54 or IP67: where will it be installed?

• IP00 (rectified): transformer and bridge rectifier on a heat sink, no enclosure, screw-terminal outputs. For a control cabinet or a protected workshop.
• IP23 (rectified): protected against solid objects over 12.5 mm and against rain up to 60° from the vertical; screw-terminal outputs. For a plant room.
• IP54 (rectified): metal case or resin-moulded housing depending on the rating, protected against dust and splashing water, with H07RN-F cable outputs. For sheltered outdoor or industrial sites.
• IP67 (waterproof 12 V power supply): dust-tight and protected against temporary immersion, finned aluminium housing. For outdoor use.

Every digit is explained in our guide to protection ratings.

Connecting an AC/DC power supply safely

Isolate the supply before any work and have the 230 V mains connection made by a qualified person, following the wiring diagram on the product page. On the output side, observe the + / − polarity of the load. Size the conductors for the current and the cable run: at 12 V the currents are high (84 A for 1,000 VA), and too small a cross-section causes voltage drop. We also sell flexible H07RN-F cable by the metre, from 2 x 1 to 2 x 4 mm².

12 V, 24 V, 48 V and higher ratings

12 V and 24 V cover most applications: lighting, gate automation, motorhomes and boats, small motors. For indoor lighting, see our LED power supplies; to step one DC voltage down to another, our DC/DC converters. A rectified 230 V to 48 V power supply is also available, from 100 to 1,000 VA.

Above 1,000 VA, or for a specific voltage, ask for a quote: we reply within 48 hours. Business customers get 5% off the whole site with a pro account, with prices shown excluding VAT.

By voltage: 230 V to 12 V transformers and 230 V to 24 V transformers.