The two letters at the front of a high-frequency transformer's code decide more about a power supply than its wattage does. EE, EFD, EP, PQ, ER, EC, ETD, EF and EL are core-and-bobbin families, and each one trades winding window against height, footprint and thermal path.

What the core code tells you

The letters name the geometry the winding sits in; the number that follows is the nominal leading dimension in millimetres. EE13, EE19, EFD15, EF20, EL19, PQ3230 and ETD34 therefore already tell a designer roughly how much board the part will occupy before a datasheet is opened. The families split by job rather than by size alone: EE and EFD for general isolated flyback and forward duty, EP and small EE for miniature current sensing and signal isolation, PQ and ETD for low-profile power conversion where the winding window matters, and ER, EC, EF and EL for the shapes that a constrained board or enclosure forces.

Family choice is usually forced by one constraint. Where height is the limit, the catalogue offers low-profile and horizontal direct-insertion types; where the winding window is the limit - a high step-up ratio, for example - the EC and EFD families carry the step-up and pulse duty, from 12 V to 300 V on the EC35 upward. Where the board itself is the limit, the SMD EE5.0 part removes the through-hole pins entirely, and where a design needs a current-sensing stage rather than a power stage, the miniature EP13 covers that job instead of a power transformer.

The nine families in the line

The high-frequency group holds 90 of the store's 720 live products, alongside 175 audio transformers, 89 low-frequency transformers and 76 inductors and coils, across 37 product groups. These are the families the twenty listings below fall into.

How to read a listing

ZXY's listings publish the four numbers a buyer actually needs - core family, FOB range, minimum order quantity and the voltage or inductance the part was wound for - and they publish them per part, because each part is wound to order. The table below is drawn from twenty live listings in the high-frequency transformer group.

Roughly two thirds of the twenty name the application in the title - switching power supply, LED power supply, charger adapter, inverter - and the rest name the electrical result: 0.9 mH and 1.25 mH on the EL19, 1.1 mH on the EE19, 5 W at AC 220 V input on the ETD34. Neither column replaces a datasheet, so treat a listing as a shortlist rather than a specification.

Price and order size

Order size is set per part, not per family: this group spans a one-piece minimum on the EE10 and the EFD20 and a 1,000-piece minimum on thirteen of the twenty listings, from US$0.17 to US$7.00 a piece across those thirteen.

Reading price and order size together is what makes a quote cheap to obtain. The cheapest family here is not the smallest: EE10 lands at US$0.15-0.18 a piece and EE13 at US$0.17-0.22, while the miniature EP13 current transformer and the EL19 sit at US$0.60-0.80. The spread inside a single part can be wider than the spread between parts - the PQ2014 is listed from US$0.80 to US$7.00, because the winding and the output voltage move the price, not the core.

For a first order, the sample points to the three parts published below a 500-piece minimum: the EE10, the EFD20 and the EC35, which is enough to build and test a converter before committing to a production quantity.

Inside the line: twenty products from the live catalogue

All twenty photographs below are product images from ZXY's live Alibaba.com high-frequency transformer listings, retrieved on September 15, 2026. Product IDs are printed with each image, and every price and order quantity quoted in this guide is the value published on that listing on that date.

What to send with a request for quotation

Because the price moves with the winding, a request travels faster when it carries the electrical brief rather than a part number: input and output voltage, output power, topology, switching frequency, isolation requirement and the board area available. ZXY lists custom winding on the EE2213, custom turn ratios and OEM/ODM programmes on the EE22 platform, and 12 V to 300 V step-up windings on the EC35, so the same core appears in several configurations.