Foreword

In power supply design, high-voltage MOSFETs are the core switching devices for achieving efficient energy conversion. With technological evolution, the manufacturing processes and characteristics of high-voltage MOSFETs have become increasingly diverse. How to strike a balance among low RDS (on), low thermal resistance, and fast switching speed has become the key for power supply engineers to optimize efficiency, cost, and reliability. Drawing on years of industry experience, Hekotai deciphers the selection logic of high-voltage MOSFETs for you.

Core Manufacturing Processes of High-Voltage MOSFETs: Planar vs. Charge Balance

The performance differences of high-voltage MOSFETs essentially stem from variations in manufacturing processes:

• Traditional Planar Process: It features core advantages of stability and durability, making it ideal for scenarios with stringent reliability requirements such as industrial power supplies and medical equipment. However, its drawbacks are also evident—under the same breakdown voltage and chip area, its on-resistance (RDS (on)) is significantly higher than that of devices manufactured with the advanced charge balance technology.
• Charge Balance Technology: By optimizing the internal charge distribution of the chip, it achieves lower RDS (on) with a smaller chip area, making it the top choice for high-frequency and high-efficiency power supplies. For instance, at the 600V rating, when the RDS (on) of a device made with the traditional planar process is 1Ω, that of a device using charge balance technology can be reduced to below 0.25Ω. Nevertheless, it is crucial to note that RDS (on) should not be the sole criterion for device selection.

A MOSFET chip consists of two parts: the active region, which contributes to RDS (on) and serves as the core area for switching functions; and the edge termination, a protective structure surrounding the active region that prevents voltage breakdown at the chip edge. For high-voltage MOSFETs, a smaller chip size leads to a larger proportion of the edge termination area. While this does not affect RDS (on), it significantly increases the junction-to-case thermal resistance. A smaller chip implies poorer thermal conductivity, causing junction temperature to rise easily. This, in turn, increases RDS (on) and the reverse recovery loss of the parasitic diode, ultimately reducing system efficiency.

Junction Temperature and Thermal Resistance: Invisible Constraints on Reliability

Junction temperature is a core indicator of MOSFET reliability—exceeding the maximum junction temperature will result in device failure. According to the junction temperature calculation formula, total power consumption consists of two components: conduction loss and switching loss. Conduction loss is determined by RDS (on), while switching loss is governed by switching speed.

The key impact of thermal resistance lies in its direct correlation with chip size. A larger chip has lower θJC, better thermal conductivity, and more manageable junction temperature, but comes with higher RDS (on). Conversely, a smaller chip offers lower RDS (on) but higher θJC, poorer thermal conductivity, and a greater tendency for junction temperature to rise.

Therefore, it is essential to balance RDS (on) and thermal resistance during device selection. Opting for an excessively small chip in pursuit of low RDS (on) may lead to elevated junction temperature due to high thermal resistance, which instead increases overall losses.

Selection Logic: A "Three-Dimensional Balance" Tailored to Applications

Based on the core requirements of specific application scenarios, Hekotai provides targeted selection guidelines:

1. High-Reliability ScenariosFor applications with extremely high reliability requirements, MOSFETs manufactured with the traditional planar process are the superior choice. Their advantages include low thermal resistance and a mature edge termination design, which enable the device to operate at low temperatures and avoid increased losses caused by excessive junction temperature. They are suitable for scenarios free from parasitic diode recovery loss, such as PFC and flyback topologies.
2. High-Frequency and High-Efficiency ScenariosIf low RDS (on) and fast switching speed are required, MOSFETs based on charge balance technology are the ideal fit. They deliver low RDS (on) with a compact chip size, feature a gate charge as low as 15nC, and reduce switching loss by 25% compared to planar process devices. They are well-suited for high-frequency flyback, resonant topologies, and other similar applications, capable of boosting efficiency to over 92%.
3. Cost-Efficiency Balanced ScenariosFor applications that demand a balance between cost and efficiency, hybrid technology MOSFETs serve as an optimal compromise. Combining the stability of the planar process with the low RDS (on) characteristic of charge balance technology, they offer moderate thermal resistance and cost 15% less than planar process devices. They are ideal for general-purpose power supplies, LED drivers, and related applications.

Conclusion: Selection is the Art of System-Level Balance

Selecting a high-voltage MOSFET is essentially a process of achieving system-level balance among efficiency, cost, and reliability. Selection should be driven by application scenarios, with comprehensive consideration of RDS (on), thermal resistance, switching characteristics, and cost, rather than focusing on a single parameter. As a professional discrete device manufacturer, Hekotai not only offers cost-effective medium-and-low voltage MOSFETs and industrial-grade MOSFETs, but also provides full-process support from device selection to application implementation through its team of senior FAE experts, helping you quickly deploy efficient and reliable power supply solutions.

Company Profile

Founded in 1992, Hekotai is a high-tech and specialized, sophisticated, and innovative enterprise integrating R&D, design, production, and sales of electronic components. We specialize in providing cost-effective component supply and customization services to meet the R&D needs of enterprises.

Product Range: We offer a comprehensive portfolio covering discrete devices and passive components such as chip resistors, including MOSFETs, TVS diodes, Schottky diodes, zener diodes, fast recovery diodes, bridge rectifiers, diodes, triodes, resistors, and capacitors.

Two Smart Manufacturing Centers: Our manufacturing hubs in South China and Southwest China (Huizhou: 75,000 ㎡; Nanchong: 35,000 ㎡) are equipped with over 3,000 sets of advanced production and testing equipment. In 2024, we added three semiconductor material subsidiaries to control production capacity and delivery efficiency from the source.

OEM Packaging and Testing Services: We support sample customization and small-batch trial production. Backed by more than 100 patented technologies and compliance with ISO9001 and IATF16949 certification systems, we ensure that "quality first" is implemented throughout every stage from R&D to delivery.

Adhering to the core philosophy of "customer-centric, innovation-driven", Hekotai is committed to providing stable and reliable components for enterprises.

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