As a classic electronic component, the through-hole power inductor continues to hold a significant position in modern electronic circuits, thanks to its unique structural advantages and electrical performance. Despite the increasing popularity of surface-mount technology (SMT), through-hole packaging remains indispensable for applications requiring high current, high power, and high reliability.
I. Packaging Structure and Features
Plug-in power inductors are typically secured by soldering their leads through the through-holes of a printed circuit board (PCB). Their core structure generally consists of a magnetic core (such as ferrite, silicon steel sheets, or nanocrystalline alloy), windings (enameled copper wire), and leads. Common configurations include I-core (or “dog-bone”), toroidal, and cylindrical shapes.
1. High mechanical strength: The pins are inserted into the PCB and soldered, creating a robust physical connection with excellent shock resistance; some products can withstand shocks of up to 50G, making them suitable for environments with intense vibration.
2. Excellent heat dissipation performance: Compared to surface-mount (SMD) inductors, leaded inductors are larger in size and have a greater surface area, which facilitates heat dissipation; furthermore, their leads can serve directly as heat dissipation paths, enabling them to withstand higher power losses.
3. High current-carrying capacity: Due to the use of thicker wire and larger cores, leaded inductors typically feature higher saturation and temperature-rise current ratings, making them suitable for high-power applications.
4. Limitations: They occupy more PCB space and are unsuitable for miniaturized devices requiring high-density integration; additionally, automated insertion is slightly more challenging compared to surface-mount processes.
II. Main Application Areas
Due to their high power, low impedance, and high reliability, plug-in power inductors are widely used in the following areas:
1. Power Management and Conversion Circuits
DC-DC Converters: Serve as energy-storage inductors in Boost, Buck, and Buck-Boost circuits, utilizing high saturation characteristics to stabilize output voltage.
Switched-Mode Power Supplies (SMPS): Used for input/output filtering to smooth current ripple and improve power efficiency.
Industrial UPS and PV Inverters: In high-power industrial power supplies, toroidal or large I-core leaded inductors are commonly used for line-frequency filtering to ensure the stability of the power system.
2. Electromagnetic Interference (EMI) Suppression
Differential Mode Inductor: Plug-in I-type inductors (such as VC type and PK type) are commonly used in EMI filtering circuits at the power supply input to suppress high-frequency noise interference and meet electromagnetic compatibility standards.
Chokes: These utilize their high impedance to AC signals to block the passage of high-frequency noise while allowing DC or low-frequency signals to pass through unimpeded.
3. Automotive Electronics
Automotive DC/DC Modules: In 48V mild-hybrid systems and the electronic systems of conventional internal combustion engine vehicles, leaded inductors must withstand high temperatures (e.g., 125°C) and severe vibration within the engine compartment. AEC-Q200 compliant, automotive-grade leaded inductors are widely used in this application.
Motor Drives: Used to suppress voltage spikes caused by motor back-EMF, thereby protecting control circuits.
4. Industrial Control and Communication Equipment
Variable Frequency Drives (VFDs): Used at the output stage for filtering and absorbing voltage spikes, thereby protecting motor insulation.
LED Driver Power Supplies: Provide stable current output, ensuring the longevity and luminous efficacy of lighting equipment.
RF and Signal Processing: Certain high-frequency plug-in inductors are used in LC resonant circuits to perform functions such as frequency selection and impedance matching.
III. Key Parameters for Selection
In practical applications, when selecting plug-in power inductors, the following parameters need to be comprehensively considered:
Inductance (L): Determined based on the circuit’s operating frequency and ripple current requirements; the typical range is 1.0 μH to 100 mH.
Rated Current: Both saturation current (the current at which inductance drops by 30%) and temperature-rise current (the current causing a 40°C temperature rise) must be considered; in design, the lower of the two values is typically selected, with a margin of at least 20% included.
DC Resistance (DCR): Lower is better to minimize copper loss and heat generation.
Package Dimensions: Includes pin pitch (e.g., 5mm, 7.5mm, 10mm, etc.) as well as core diameter and height; must match the available space on the PCB layout.
Operating Temperature Range: Standard products typically range from -20°C to 80°C, while industrial or automotive-grade products can withstand -40°C to 125°C or even higher.
IV. Development Trends
As electronic devices trend toward higher frequencies and miniaturization, leaded power inductors are also continuously evolving. The application of new magnetic materials has reduced core losses at high frequencies, while improvements in manufacturing processes—such as integrated molding technology—have enhanced product consistency and reliability. Although surface-mount inductors dominate the market for low-power portable devices, leaded power inductors will continue to play a pivotal role in sectors requiring high power and high reliability—such as new energy, industrial automation, and automotive electronics—thanks to their superior electrical performance and mechanical strength.
