What Are Transformers?
Transformers transfer electrical energy between circuits through electromagnetic induction, providing voltage conversion, electrical isolation, and impedance matching. Types include power transformers (mains to low voltage), pulse transformers (for switching converters), signal/audio transformers, current sense transformers, and Ethernet/LAN transformers (magnetics). LCSC stocks 8,000+ transformer SKUs from 100+ manufacturers.
Transformers — Definition and Sub-Categories
A transformer consists of two or more wire coils (windings) wound around a shared magnetic core. When alternating current flows through the primary winding, it creates a changing magnetic field that induces a voltage in the secondary winding(s). The voltage ratio equals the turns ratio between primary and secondary windings.
|
Sub-Category |
Function |
Key Parameters |
SKUs at LCSC |
|
Power Transformers |
Mains voltage step-down for linear power supplies |
Primary voltage, secondary voltage/current, VA rating |
2,000+ |
|
Switching/Pulse Transformers |
Energy transfer in SMPS and isolated DC-DC converters |
Turns ratio, inductance, isolation voltage, frequency |
2,000+ |
|
LAN/Ethernet Transformers |
Isolation and impedance matching for Ethernet ports |
IEEE standard, port count, isolation voltage, package |
1,500+ |
|
Current Sense Transformers |
Non-invasive AC current measurement |
Turns ratio, accuracy, frequency range, burden resistance |
500+ |
|
Audio Transformers |
Impedance matching and isolation for audio signals |
Impedance ratio, frequency response, distortion |
300+ |
How to Choose: Transformers Selection Guide
For AC-DC linear power supplies, select power transformers by VA rating (must exceed load power by 20–30%), primary voltage (115V/230V or dual), and secondary voltage. For switching power supplies, choose pulse transformers designed for your switching frequency and topology (flyback, forward, push-pull). For Ethernet connectivity, use integrated LAN transformers that match your PHY chip’s requirements. Always verify safety isolation ratings (reinforced insulation for mains-connected applications).
Transformers Comparison
|
Transformer Type |
Frequency Range |
Isolation |
Typical Size |
Application |
|
Mains Power (EI core) |
50/60 Hz |
2–4 kV |
Medium–Large |
Linear power supplies |
|
Switching (ferrite) |
20 kHz–1 MHz |
3–5 kV |
Small |
SMPS, flyback converters |
|
LAN Magnetics |
1–100 MHz |
1.5 kV typical |
Small SMD |
Ethernet ports |
|
Current Sense |
50 Hz–100 kHz |
4 kV |
Small toroid |
Non-invasive current measurement |
Why Source Transformers from LCSC Electronics
LCSC stocks 8,000+ transformer SKUs from 100+ manufacturers including Wurth, Pulse, Halo, and Asian transformer specialists. The catalog covers everything from tiny SMD LAN magnetics to larger mains-frequency power transformers, enabling complete power supply BOM sourcing.
Frequently Asked Questions
Q: What is the difference between a power transformer and a switching transformer?
Power transformers operate at mains frequency (50/60 Hz) and are larger and heavier. Switching transformers operate at high frequencies (20 kHz–1 MHz) in SMPS circuits and are much smaller for the same power rating due to the higher frequency. Switching transformers use ferrite cores; mains transformers use laminated steel cores.
Q: What is an Ethernet/LAN transformer?
A LAN transformer (also called Ethernet magnetics) provides galvanic isolation and impedance matching between the Ethernet PHY chip and the RJ45 connector. It’s required by the Ethernet standard for safety isolation and common-mode noise rejection. Some RJ45 connectors include integrated magnetics.
Q: How do I size a power transformer?
Calculate total load power in VA (volt-amperes). Add 20–30% margin for startup inrush and losses. Verify secondary voltage under load (transformer voltage drops under load due to regulation). For linear supplies, the secondary AC voltage should be approximately 1.4× the desired DC output plus diode drops.
Q: What is transformer isolation rating?
Isolation rating (in volts, tested for 1 minute) indicates the maximum voltage difference the transformer can safely withstand between primary and secondary windings. Reinforced isolation (typically 3–4 kV) is required for mains-connected applications to meet safety standards.