What Is a Coupled Inductor?
A coupled inductor is a magnetic component that shares a single core between two or more windings, allowing energy transfer and magnetic coupling between circuits. It is a key building block in multiphase buck converters, flyback converters, and power factor correction circuits where size reduction and improved transient response are critical.
Working Principle
When current flows through the primary winding, the magnetic flux links both windings. The coupling coefficient k defines how much flux is shared. In multiphase converters, coupled inductors cancel the ripple current in the steady state while allowing fast dynamic response during load steps, reducing core loss and output capacitance requirements.
Key Specifications Table
| Parameter | Typical Value | Note |
|---|---|---|
| Inductance per phase | 0.1 – 100 µH | Application dependent |
| Coupling coefficient | 0.3 – 0.95 | Adjustable by core geometry |
| Saturation current | 1 – 100 A | Core material dependent |
| Core materials | Ferrite / powder / nanocrystalline | Loss vs. cost trade-off |
| DCR | 0.5 – 50 mΩ | Copper loss factor |
| Operating temperature | -40 to +150 °C | Thermal design |
Market Trends
The coupled inductor market is growing with the expansion of AI servers, data center power supplies, electric vehicle DC-DC converters, and multiphase VRM designs. The global coupled inductor market is expected to grow at a CAGR of around 6-8% driven by higher power density requirements in computing and EV applications.
Selection Steps
Step 1: Determine the number of phases and coupling polarity. Step 2: Calculate required inductance and saturation current. Step 3: Select core material and geometry for the target coupling coefficient. Step 4: Optimize winding for DCR and AC resistance. Step 5: Verify thermal performance in the worst-case operating point.
Applications
Coupled inductors are used in multiphase buck converters for CPUs and GPUs, automotive DC-DC converters, LED drivers, interleaved PFC stages, and isolated power modules.
Sirui Technology Coupled Inductors
Shaanxi SiRui Technology Co., Ltd. offers custom coupled inductors with precise coupling coefficient control, ISO9001 certified manufacturing, and RoHS / REACH / SGS / CTI compliance. Contact sales@sirui-tech.com for your custom design.
FAQ
Q: Can you design a coupled inductor for a 12-phase VRM? A: Yes, we design multi-phase coupled inductors with custom coupling coefficients. Q: What is the minimum order quantity? A: MOQ is negotiable for new designs, samples available in 7-10 days.