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Gallium nitride fast charging imposes extremely high requirements on high power high frequency transformer
2026-07-23
Why is it necessary to use high-frequency transformers for high-power gallium nitride fast charging?
Gallium Nitride (GaN) fast charging, with its core advantages of high frequency, low conduction loss and miniaturization, has already completely replaced traditional silicon-based adapters and become the mainstream solution for multi-port high-power fast charging. From 65W and 100W portable chargers to 140W and 240W high-power GaN chargers for laptops and gaming laptops, the industry generally pursues smaller size, higher power density, lower temperature rise, and synchronous stable output for multiple ports. Many manufacturers believe that as long as they use GaN power tubes, they can achieve high-performance fast charging. However, they overlook the decisive role of the high-frequency transformer as the core of energy conversion. A large number of low-priced GaN fast chargers have shown common problems such as overheating of the body, imbalance in power distribution for multiple ports,whining noise during charging, skipping of fast charging steps, insufficient charging, and performance degradation over a long period of use.
At its core, the gallium nitride chip is merely a switching control unit, while the high-frequency transformer is responsible for the core tasks of voltage isolation, energy transmission, power distribution, and stable output. The working frequency of gallium nitride devices is much higher than that of traditional silicon solutions, generally reaching the ultra-high frequency range of 100kHz to 2MHz. This places extremely strict requirements on the material of the transformer core, winding process, leakage inductance control, insulation temperature resistance, power margin, and loss balance. Ordinary low-cost transformers that are compatible with silicon power supplies simply cannot match the high-frequency conditions of gallium nitride, and will directly nullify all the advantages of gallium nitride itself. To fully realize the core value of gallium nitride's fast charging, which includes small size, high power, low temperature rise, and stable output across multiple ports, it is necessary to support customized high-performance high-frequency transformers.
- The ultra-high working frequency of gallium nitride fast charging imposes extremely strict requirements on transformer losses.
The traditional silicon MOS fast charging operates at frequencies ranging from 30kHz to 60kHz, and the high-frequency losses of the magnetic core and windings are relatively small. However, the switching losses of gallium nitride devices are extremely low. The circuit design will actively increase the working frequency to reduce the volume of the magnetic core and capacitors, achieving high-density miniaturization. The frequency of high-power gallium nitride fast charging generally exceeds 150kHz, and high-end models even reach above 500kHz. The high-frequency alternating magnetic field will simultaneously amplify the eddy current losses, hysteresis losses of the magnetic core, as well as the skin effect and proximity effect losses of the windings.
If an ordinary low-specification transformer is used in combination, a double loss collapse will occur:
First, the high-frequency loss of the ordinary manganese-zinc magnetic core will sharply increase. The conventional PC40 magnetic core is only suitable for low-frequency silicon power supplies. In the case of gallium nitride ultra-high-frequency operation, the eddy current loss increases exponentially, converting a large amount of electrical energy into heat, directly causing the gallium nitride fast-charging device to abnormally overheat. Gallium nitride itself has extremely low heat generation, and the entire temperature rise of the device is dominated by the loss of the inferior transformer, losing the core advantage of low temperature rise of gallium nitride.
Second, the loss of the ordinary loose-winding winding doubles. At high frequencies, the current will concentrate on the surface of the wire. The fine wires and loosely wound transformers have a severe skin effect, and the equivalent internal resistance of the winding increases significantly. When delivering full-load high-power output, the copper loss surges. Especially in multi-port gallium nitride fast-charging, multiple paths are simultaneously delivering full-load output, and the winding continuously works under a large current, causing the temperature to accumulate continuously. It triggers the power supply to overheat and reduce power, resulting in problems such as automatic speed reduction during fast charging, switching to slow charging, and insufficient power distribution among multiple ports.
High-quality high-frequency transformers are specifically designed to match the high-frequency characteristics of gallium nitride: they use PC95 and PC97 ultra-high-frequency low-loss magnetic cores, with fine-grained magnetic domain processing, which significantly reduces high-frequency eddy currents and magnetic hysteresis losses; they employ multiple layers of Litz wires connected in parallel for winding, which mitigates the skin effect and reduces the loss of high-frequency windings. Only such customized transformers can match the ultra-high-frequency working environment of gallium nitride, controlling the overall loss and temperature rise within the designed range, and truly leveraging the energy-saving and low-temperature rise advantages of gallium nitride.
- High-power multi-port power dynamic allocation, relying on precise coupling of transformers and low leakage inductance characteristics
The current mainstream high-power gallium nitride fast charging devices all adopt multi-output designs. Devices with 100W and 140W power ratings typically come with 2C1A, dual Type-C interfaces, and support single-port full-power fast charging and multi-port dynamic intelligent power allocation. The device will adjust the output power in real time based on the number of connected devices and charging requirements, with frequent changes in load and significant fluctuations in instantaneous current. The stability of this dynamic power allocation mechanism entirely depends on the leakage inductance control of the high-frequency transformer, the symmetry of the windings, and the output voltage adjustment rate.
Common low-cost transformers have problems such as loose winding, asymmetric windings, large primary-secondary coupling gap, and extremely high leakage inductance. During high-frequency and dynamic load switching with gallium nitride, the leakage inductance will cause a significant inductive voltage drop, leading to three major serious issues:
1. When a single port is fully loaded, the voltage drop is severe, unable to maintain the constant voltage range of the fast charging standard. Mobile phones and laptops cannot recognize the fast charging protocol and directly switch to 5V slow charging.
2. When multiple ports are simultaneously connected to loads, each output channel interferes with each other. When one device starts fast charging, the voltage of another channel fluctuates significantly, resulting in insufficient charging or phantom power consumption.
3. During instantaneous load switching, high-frequency voltage spikes are generated, impacting the gallium nitride switching tubes and the rear-end capacitors. Long-term use shortens the lifespan of components and even triggers overvoltage protection and disconnection.
1. When a single port is fully loaded, the voltage drop is severe, unable to maintain the constant voltage range of the fast charging standard. Mobile phones and laptops cannot recognize the fast charging protocol and directly switch to 5V slow charging.
2. When multiple ports are simultaneously connected to loads, each output channel interferes with each other. When one device starts fast charging, the voltage of another channel fluctuates significantly, resulting in insufficient charging or phantom power consumption.
3. During instantaneous load switching, high-frequency voltage spikes are generated, impacting the gallium nitride switching tubes and the rear-end capacitors. Long-term use shortens the lifespan of components and even triggers overvoltage protection and disconnection.
The high-frequency transformer designed for high-power fast charging with gallium nitride features a sandwich symmetrical three-layer winding process. The primary and secondary windings are closely and alternately arranged to maximize the magnetic coupling area, and the leakage inductance is strictly controlled within a very small range. The multiple output windings are evenly and symmetrically arranged, with consistent internal resistance and coupling coefficient for each path. During dynamic load switching, the voltage drop is minimal and cross-interference is extremely low. Whether it is a single-port full power or simultaneous charging of multiple ports, it can stably maintain the standard output voltage, ensuring the continuous effectiveness of fast charging protocols such as PD and QC, and achieving intelligent power distribution. This is a performance that ordinary transformers cannot achieve.
- GaN aims for extreme miniaturization and high density, The transformer must also balance high power density and heat dissipation space.
One of the core selling points of GaN fast charging is "half the volume at the same power". The internal cavity is extremely compact, and the component layout is dense. The heat dissipation environment is extremely demanding. Traditional large-volume, high-loss transformers cannot fit into the narrow body, while inferior miniaturized transformers often have insufficient power margin and magnetic core saturation problems, unable to sustain continuous high-power output.
For ordinary small-sized transformers, in order to reduce costs, the cross-sectional area of the magnetic core is reduced, the wire diameter of the windings is thinned, and the magnetic flux density is designed to approach the saturation threshold. In a high-power continuous output environment of gallium nitride and a sealed environment with high temperatures in summer, the magnetic core is prone to enter a magnetic saturation state, resulting in a sudden drop in flux transmission capacity, a significant reduction in output power, and a sharp increase in harmonics and noise. Moreover, there is no extra space for heat dissipation inside the compact casing, and the heat generated by the transformer saturation cannot be dissipated, forming a vicious cycle of high temperatures. In the mild cases, the fast charging power drops, while in severe cases, overheating protection causes the machine to stop.
A high-frequency transformer specially designed for GaN fast charging, with high-density optimization in terms of magnetic core and winding structure: using a high-saturation flux, low-loss ultra-thin magnetic core, it can carry a larger continuous power under the same volume; reasonably optimizing the working magnetic flux density, leaving sufficient saturation margin, and will not enter the saturation range under long-term full-load and high-temperature conditions; combined with layered sparse winding and vacuum impregnation and curing process, a small micro-channel for heat dissipation is reserved inside the winding, and the heat can be quickly conducted to the magnetic core and the casing. It balances power, loss and heat dissipation within a very small volume, perfectly meeting the structural requirements of high-density miniaturization of GaN fast charging, and will not have the performance drawback of "not enough space for large power" in a small body.
- Ultra-high frequency conditions amplify vibration and noise defects, High-quality transformers are the core guarantee for silent fast charging.
The characteristics of the GaN fast charging high-frequency switch will amplify the whistling and buzzing noises caused by the winding and core of the transformer. The slight winding vibration of the low-frequency silicon power supply will be transformed into high-frequency noises that are clearly audible to the human ear at frequencies above 100kHz. In quiet office environments at night, these noises are particularly irritating and seriously affect the user experience.
Low-cost transformers usually have defects such as loose wiring, uneven tension, and no epoxy curing during the manufacturing process. The high-frequency alternating electromagnetic force causes the wires to vibrate continuously at the micron level. The magnetic core's magnetostriction vibration is superimposed, resulting in a continuous humming sound. The higher the frequency of gallium nitride fast charging, the more obvious the vibration noise becomes. There is a slight abnormal sound when the device is idle, and the noise becomes harsh when it is charging at full power. Many manufacturers attempt to alleviate the vibration noise by increasing the buffer capacitor and optimizing the circuit loop for noise reduction, but this can only achieve a minor improvement and cannot eliminate the vibration source at its root.
The high-performance gallium nitride-based matching high-frequency transformer adopts fully automatic constant-tension precision winding. The windings and layers are closely packed without any gaps, and the primary and secondary windings are symmetrically wound to achieve balanced electromagnetic attraction. After production, it undergoes a complete vacuum pressure impregnation process, where the windings and the magnetic core are solidified into a rigid whole, completely eliminating the vibration space. At the same time, high-end magnetic cores with low magnetostriction coefficients are selected. This inhibits the vibration of the magnetic core at the material level, enabling silent operation in all working conditions such as no-load, single-port full-load, and simultaneous charging of multiple ports, thus solving the problem of high-frequency humming in fast-charging of gallium nitride.
- High Voltage Isolation and Long-Term Durability, the Safety Bottom Line of GaN Fast Charging Relies on Transformer Insulation System
The high-power GaN fast charging input is 220V AC from the mains, and the output is a low-voltage high current. The electrical isolation between high and low voltages is entirely dependent on the insulation structure of the high-frequency transformer. This is the core safety barrier for the entire device to prevent leakage, breakdown, and fire. Under the high-frequency operation of GaN, the winding layers and the primary and secondary coils will continuously withstand high-frequency pulse voltage impacts. The requirements for the insulation material's temperature resistance, voltage resistance, and aging resistance are much higher than those of traditional silicon power supplies.
Low-cost transformers use thin ordinary insulating paper and low-temperature-resistant enameled wires, resulting in insufficient creepage distance. Under long-term high-temperature and high-frequency pulse impact conditions, the insulation layer gradually carbonizes and deteriorates, posing significant safety hazards such as leakage, inter-turn short circuits, and fire of the entire device. The internal temperature of the compact gallium nitride body is even higher, accelerating insulation aging and shortening the lifespan of the charger.
High-frequency transformers compatible with gallium nitride fast charging adopt a complete multi-level insulation structure: 200-level high-temperature-resistant thick enamel-coated copper enameled wires, double-layer composite isolation insulating paper, strictly meeting the creepage distance and electrical clearance requirements of safety standards; vacuum impregnated insulating paint fills all gaps, isolating moisture and dust, and maintaining stable insulation performance without attenuation under high temperatures. Even under long-term high-power continuous charging and in a summer high-temperature environment, the insulation system will not fail, firmly establishing the safety bottom line for the long-term use of gallium nitride fast charging and avoiding safety accidents such as leakage, bulging, and burning.
Gallium nitride power transistors are merely switching control components, determining the switching loss; while the high-frequency transformer is the energy transmission core of the entire fast charging system, directly determining the temperature rise, the stability of fast charging, the power distribution among multiple ports, the noise level, and the safety and durability. The unique working conditions of gallium nitride with ultra-high operating frequency, large power, and miniaturization, as well as multi-port dynamic load, have significantly raised the design and manufacturing standards for high-frequency transformers. Ordinary transformers that are adapted to traditional silicon power supplies will completely nullify the advantages of gallium nitride's small size, high efficiency, and low temperature rise, resulting in overheating, sudden disconnection of fast charging, high noise, insufficient charging, and safety hazards.
To create a truly high-performance, stable and durable high-power gallium nitride fast charger, a customized high-performance high-frequency transformer must be matched: Select ultra-high-frequency low-loss magnetic cores to reduce high-frequency losses, precisely symmetrical winding to strictly control leakage inductance to ensure dynamic power stability, sufficient magnetic density margin to adapt to miniaturized and high-density body designs, and solidification process to eliminate high-frequency humming, and high-grade insulation system to maintain the long-term safety bottom line.
With the continuous increase in fast charging power and the popularity of portable multi-output GaN in the market, high-frequency transformers are no longer just simple accessory components. Instead, they have become the core key that determines the experience, quality and safety of GaN fast charging products. To fully leverage the advantages of GaN technology, and achieve a complete product experience of small size, high power, low temperature rise, quiet operation and stable fast charging, it is necessary to use high-quality high-frequency transformers.
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