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PQ Flat Wire Inductor-The Core Magnetic Component of High-Power Power Supply
2026-07-07
What is the PQ flat wire inductor? The core magnetic components of high-power power supplies
In the current era where switching power supplies are undergoing rapid iterations towards higher frequencies, smaller sizes, and greater power densities, traditional round wire winding power inductors are gradually revealing their shortcomings: high skin loss at high frequencies, excessive temperature rise, low utilization rate of winding space, and insufficient saturation capacity under high current conditions. These issues have made them unable to meet the stringent design requirements of server power supplies, vehicle power supplies, photovoltaic inverters, and gallium nitride fast charging power supplies. Against this backdrop, PQ flat wire inductors, thanks to their dual innovations in core structure and winding process, have become the mainstream choice for the new generation of high-power power supply solutions. Many hardware engineers, when developing high-density power supplies, will prioritize this component. Its function may seem simple: energy storage, filtering, and suppression of electromagnetic interference. However, different types of inductors vary greatly in performance and application.
- The Basic Definition and Internal Structure of PQ Flat Wire Inductors
Most traditional inductors use circular enameled wire for winding, while PQ flat wire inductors adopt a combined design of flat copper wire and PQ-type ferrite cores as the framework. The windings are wound using rectangular copper strips (flat enameled copper wire), undergo insulation treatment, and are encapsulated and cured to form a power energy storage inductor. We can understand the name by splitting it into two core units.
PQ cores belong to a closed ferrite core structure, with a square central column and a fully encapsulated shell. The magnetic circuit is complete and the magnetic flux path is short, with leakage flux far lower than E-type, EC-type, and ETD-type cores. Its greatest feature is that the utilization rate of the winding window is extremely high, the internal space of the core is regular, and it is very suitable for multi-layer close winding; the closed shell has a natural shielding effect, reducing external electromagnetic radiation, and making it easier to pass EMC electromagnetic compatibility tests. Common industry specifications include PQ2016, PQ2620, PQ3225, PQ3530, etc., covering current ratings from tens of amps to hundreds of amps, and are standard magnetic core types for industrial power supplies and communication power supplies.
The flat wire winding is the next part. Traditional inductors generally use circular enameled copper wire, while PQ flat wire inductors switch to thin and wide rectangular copper conductors. The flat copper strip can be arranged in a single layer closely, with almost no gaps between turns, and the winding filling rate can be increased by more than 30%. At the same time, the surface area of the flat conductor is larger, and the current distribution is more uniform, which can significantly reduce the skin effect and proximity effect under high-frequency conditions, which is also the key reason why it has lower high-frequency loss than ordinary round wire inductors.
The overall device consists of PQ zinc-manganese ferrite cores, flat copper windings, high-temperature resistant insulating films, pin terminals, and epoxy resin curing layers. The windings are tightly wound around the central column of the core, and after the core is molded, a complete closed magnetic circuit is formed. The ends of the winding are directly welded to metal pins, which can be made into through-hole packaging or processed into surface mount DIP structure, suitable for automated SMT production lines, with extremely high production consistency. From the working principle, it still relies on electromagnetic induction to complete the conversion of electrical energy and magnetic energy, and in DC-DC converters and LLC resonant power supplies, it plays a core role in energy storage, current continuation, and smoothing of current ripple, but after structural optimization, its performance has achieved a leapfrog upgrade.
- Five core advantages of PQ flat-wire inductors over traditional round-wire inductors
1. Significantly reduced high-frequency losses, resulting in a substantial improvement in the overall power supply efficiency
Modern switching power supplies typically increase the switching frequency to 500kHz - 2MHz to reduce the overall size of the device. When high-frequency alternating current flows through the wire, the skin effect occurs, causing the current to flow only on the surface of the conductor. The effective conductive area of the round copper wire will sharply decrease, resulting in a significant increase in AC resistance. The flat copper wire thickness can precisely match the skin depth at high frequencies, allowing the current to be evenly distributed across the entire cross-section of the conductor, effectively suppressing AC resistance ACR. At the same time, the single-layer flat winding reduces the magnetic coupling between turns, and the additional losses caused by proximity effects are effectively controlled. Experimental data shows that at a 1MHz switching frequency, the total copper loss of the same specification PQ flat-wire inductor is more than 40% lower than that of the ordinary round-wire inductor, and the power supply's overall conversion efficiency can be increased by 0.5% - 1.5%. Long-term continuous operation can save a significant amount of electricity, especially suitable for uninterruptible power supplies in data centers that operate around the clock.
Modern switching power supplies typically increase the switching frequency to 500kHz - 2MHz to reduce the overall size of the device. When high-frequency alternating current flows through the wire, the skin effect occurs, causing the current to flow only on the surface of the conductor. The effective conductive area of the round copper wire will sharply decrease, resulting in a significant increase in AC resistance. The flat copper wire thickness can precisely match the skin depth at high frequencies, allowing the current to be evenly distributed across the entire cross-section of the conductor, effectively suppressing AC resistance ACR. At the same time, the single-layer flat winding reduces the magnetic coupling between turns, and the additional losses caused by proximity effects are effectively controlled. Experimental data shows that at a 1MHz switching frequency, the total copper loss of the same specification PQ flat-wire inductor is more than 40% lower than that of the ordinary round-wire inductor, and the power supply's overall conversion efficiency can be increased by 0.5% - 1.5%. Long-term continuous operation can save a significant amount of electricity, especially suitable for uninterruptible power supplies in data centers that operate around the clock.
2. Stronger current-carrying capacity and better anti-current saturation characteristics
The flat conductor has a larger cross-sectional area, with extremely low DC resistance DCR, resulting in smaller voltage drop under high current, and less tendency to heat saturation. For two inductors of the same size, the saturation current of the PQ flat-wire product can be more than double. Ordinary round-wire inductors are prone to rapid demagnetization under large impact currents, with the inductance dropping sharply, leading to an increase in power supply output ripple; while the PQ closed magnetic core combined with the flat winding can have a uniform magnetic flux density distribution, stronger anti-dc bias ability, and even when working under large current conditions, can maintain stable inductance parameters and will not easily enter the saturation state. In new energy vehicle DC-DC and high-power energy storage inverters, the instantaneous impact current is very large. Only the PQ flat-wire structure can stably hold the peak current, ensuring that the circuit does not experience runaway protection.
The flat conductor has a larger cross-sectional area, with extremely low DC resistance DCR, resulting in smaller voltage drop under high current, and less tendency to heat saturation. For two inductors of the same size, the saturation current of the PQ flat-wire product can be more than double. Ordinary round-wire inductors are prone to rapid demagnetization under large impact currents, with the inductance dropping sharply, leading to an increase in power supply output ripple; while the PQ closed magnetic core combined with the flat winding can have a uniform magnetic flux density distribution, stronger anti-dc bias ability, and even when working under large current conditions, can maintain stable inductance parameters and will not easily enter the saturation state. In new energy vehicle DC-DC and high-power energy storage inverters, the instantaneous impact current is very large. Only the PQ flat-wire structure can stably hold the peak current, ensuring that the circuit does not experience runaway protection.
3. Excellent heat dissipation conditions, lower device temperature rise
Heat has always been a pain point in the design of high-power magnetic components. The round copper wire is stacked layer by layer, and the heat accumulates inside the winding, making it difficult to dissipate outward; while the flat copper tape is laid flat for winding, the large-area conductor directly adheres to the magnetic core frame, and the heat can be quickly conducted to the magnetic core shell, then through the PCB solder pad to dissipate outward. The winding is not densely stacked, and the internal air circulation is better, preventing local heat accumulation. Under the same power load conditions, the surface temperature rise of the PQ flat-wire inductor is 15℃ - 25℃ lower than that of the traditional winding inductor, the aging speed of the insulation layer is significantly slowed down, and the device service life is multiplied, perfectly solving the thermal design problems in high-density sealed power supplies.
Heat has always been a pain point in the design of high-power magnetic components. The round copper wire is stacked layer by layer, and the heat accumulates inside the winding, making it difficult to dissipate outward; while the flat copper tape is laid flat for winding, the large-area conductor directly adheres to the magnetic core frame, and the heat can be quickly conducted to the magnetic core shell, then through the PCB solder pad to dissipate outward. The winding is not densely stacked, and the internal air circulation is better, preventing local heat accumulation. Under the same power load conditions, the surface temperature rise of the PQ flat-wire inductor is 15℃ - 25℃ lower than that of the traditional winding inductor, the aging speed of the insulation layer is significantly slowed down, and the device service life is multiplied, perfectly solving the thermal design problems in high-density sealed power supplies.
4. Higher power density, helping to miniaturize and make devices thinner
Current industrial power supplies and server module power supplies are constantly reducing their structural dimensions. The PQ magnetic core itself has high window utilization, and combined with the flat winding without extra gaps, the winding filling coefficient is significantly increased. To achieve the same inductance and current-carrying capacity, the overall volume of the PQ flat-wire inductor can be 35% - 45% smaller than that of the round-wire inductor, and the thickness can also be made thinner. Previously, a 40A power inductor required 45mm × 45mm of PCB space; by using the PQ32 series flat-wire product, the size can be compressed to within 33mm × 33mm, Free up abundant layout space for other components on the circuit board, perfectly aligning with the industry trend of miniaturized power supplies.
Current industrial power supplies and server module power supplies are constantly reducing their structural dimensions. The PQ magnetic core itself has high window utilization, and combined with the flat winding without extra gaps, the winding filling coefficient is significantly increased. To achieve the same inductance and current-carrying capacity, the overall volume of the PQ flat-wire inductor can be 35% - 45% smaller than that of the round-wire inductor, and the thickness can also be made thinner. Previously, a 40A power inductor required 45mm × 45mm of PCB space; by using the PQ32 series flat-wire product, the size can be compressed to within 33mm × 33mm, Free up abundant layout space for other components on the circuit board, perfectly aligning with the industry trend of miniaturized power supplies.
5. Less EMI interference， reducing the difficulty of overall electromagnetic correction On one hand, the PQ all-inclusive closed magnetic core forms a complete magnetic shield, confining the internal magnetic field firmly within the magnetic circuit, with very little leakage magnetic flux, which will not interfere with the surrounding MOS transistors, driver chips, and sampling circuits. On the other hand, the flat wire winding arrangement is regular, and the inter-winding parasitic capacitance is smaller, resulting in lower high-frequency harmonic noise. Many engineers often encounter radiation exceed the standard problems when using ordinary winding inductors， and need to add a large number of filtering devices. However， the PQ flat wire inductor, with its low leakage magnetic flux and low parasitic parameters, can suppress electromagnetic noise from the source, shorten the power supply EMC debugging cycle， and save development costs.
- Main Application Scenarios of PQ Flat Wire Inductors
With its comprehensive performance of low loss, high current capacity, small size, and low EMI, this inductor has gradually penetrated into various high-power electrical fields from mid-to-high-end communication power supplies, becoming a necessary component.
First, data centers and server power supplies. VRM multi-phase buck modules, redundant power supplies, and rack-mounted switching power supplies have extremely high requirements for efficiency, current ripple, and continuous operation stability. The PQ series flat wire inductors are the preferred solution for multi-phase energy storage inductors, ensuring that servers operate at full load without overheating or losing efficiency.
Second, electric control systems of new energy vehicles. Vehicle OBC chargers, high and low voltage DC-DC converters have large working currents and harsh vibration environments. The vehicle-level PQ flat wire inductors have wide temperature characteristics, maintaining parameter stability within the -40°C to 125°C temperature range, and are resistant to vibration and temperature changes, suitable for the harsh conditions of vehicle applications.
Third, photovoltaic energy storage and industrial inverters. String inverters and energy storage bidirectional converters have high switching frequencies and intense current fluctuations. The flat wire inductors can effectively control high-frequency losses, reduce the overall temperature rise, and improve the power conversion efficiency of photovoltaic equipment.
Fourth, high-frequency fast charging power supplies. GaN high-power industrial fast charging and high-power DC charging station pre-regulation circuits commonly adopt high-frequency solutions. The PQ flat wire PFC inductors can maintain high efficiency while reducing volume, resolving the contradiction between miniaturization and heat generation in fast charging power supplies.
In addition, industrial frequency converters, medical equipment power supplies, rail transit auxiliary power supplies, 5G communication base station power supplies are all replacing traditional round wire inductors with PQ flat wire structure products in large quantities.
- Key Parameters for Selection and Design Considerations
When selecting hardware, one should not only consider the inductance value but also take into account multiple parameters. First, determine the core size and select the corresponding model based on the rated current and saturation current; second, verify the DC resistance (DCR), as the smaller the resistance, the lower the copper loss and the better the temperature rise control; third, strictly test the DC bias curve to ensure that the attenuation amplitude of the inductor does not exceed 20% under the maximum peak current; finally, confirm the packaging form and temperature resistance level. For industrial and vehicle applications, priority should be given to using 150°C high-temperature insulation materials, and select a fully encapsulated core structure to ensure the shielding effect.
In the winding process, single-layer flat winding is superior to multi-layer winding. The more layers, the more obvious the proximity effect loss. During design, prioritize reducing the number of winding turns to increase the utilization of the core magnetic flux, balance the inductance value and high-frequency loss. During installation layout, place the inductor away from sensitive analog circuits. Use a closed magnetic core to isolate magnetic field interference and further optimize the EMI indicators.
- Industry Development Trends
With the widespread adoption of the third-generation semiconductor devices, the operating frequency of switching power supplies will continue to increase. The performance gap of traditional wound inductors will be further exacerbated, and the market demand for PQ flat wire inductors will continue to surge. The two main technological directions in the future are quite clear: One is the development of flat and ultra-thin designs, creating short PQ magnetic cores to further reduce the thickness of the components and meet the requirements of ultra-thin module power supplies; the other is material upgrading, combining high magnetic permeability and low-loss nano-crystalline magnetic cores to reduce the high-frequency iron loss to an even lower level. At the same time, the continuous popularization of automated integrated winding equipment has led to a continuous decrease in the production cost of flat wire inductors, with their cost-performance steadily improving. They will gradually move from high-end customized products to standardized mass production, fully replacing traditional high-power wound inductors.
The PQ flat wire inductor is essentially a new generation of power magnetic component born through the combination of optimized magnetic core structure and innovative winding technology. The sealed PQ magnetic core provides high space utilization and low leakage magnetic shielding environment. The flat copper winding overcomes the three industry pain points of high-frequency skin effect loss, poor heat dissipation, and insufficient current carrying capacity. It integrates high efficiency, large current, small size, low temperature rise, and low electromagnetic interference, precisely solving the design bottleneck of modern high-frequency high-power power supplies. In the context of data center computing construction, the popularization of new energy vehicles, and the expansion of photovoltaic energy storage industry, the PQ flat wire inductor is no longer a niche high-end component. It has become an indispensable core component in the high-density solutions of hardware power supply engineers, continuously driving the switching power supply to steadily advance towards higher power density and higher energy efficiency levels.
If you are an electronic design engineer or are interested in new energy power supplies, understanding and mastering the characteristics of PQ flat-line inductors will be an indispensable part of future selection. Shenzhen CXWON Technology Co., Ltd. was established in 2012 and focuses on the research and development, design, production and sales of inductor components, dedicated to providing one-stop inductor customization services. The company has passed ISO9001 and IATF16949 quality system certifications and possesses the ability for independent research and development as well as a complete production and testing system. The products are dedicated to flat design, small size, high power, high voltage resistance, and comply with consumer, industrial and automotive standards, and are widely used in automotive electronics, communication equipment, new energy, artificial intelligence, industrial control, medical equipment and other fields.
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