The core difference between general-purpose MOSFET and high-voltage MOSFET. Although these two devices have the same core working principle (both use gate voltage to control channel conduction between source and drain), there are significant differences in design goals, structures, performance parameters, and application scenarios, mainly reflected in the following aspects:
Design Objectives and Core Challenges:
Universal MOSFET: The main design goal is to achieve the lowest possible on resistance, high switching speed, and good cost-effectiveness in a lower voltage range (usually<250V). The core challenge is to optimize the balance between conduction loss and switching loss.
High voltage MOSFET: The main design goal is to safely and reliably block high voltages (usually ≥ 500V, up to 1000V or even higher). The core challenge is how to minimize conduction resistance and manage switch losses while withstanding high voltage. High voltage blocking capability is the primary rigid requirement.
Internal structural differences (key source of differentiation):
Drift zone: This is the most fundamental structural difference. High voltage MOSFETs require a longer and lower doping concentration drift region to withstand high voltages (according to 'V=E L', the voltage V is determined by the electric field strength E and length L, and the material's ability to withstand E is limited, so it can only increase L). This long and low doped drift region determines many characteristics of high-voltage MOSFETs.
Epitaxial layer: High voltage MOSFETs typically grow a thick and high resistivity epitaxial layer on a low resistance substrate, which is the main body of the drift region and is used to withstand high voltage. The epitaxial layer of a general-purpose MOSFET is relatively thin and has low resistivity.
Differences in key electrical parameters:
On resistance:
Universal type: Rds (on) is very low (milliohm level). This is its core advantage, with low conduction loss and high efficiency.
High voltage type: Rds (on) is significantly higher than the universal type of the same size (possibly several ohms or even higher). This is mainly caused by the resistance contributed by the long and low doped drift region. `Rds (on) increases exponentially with the increase of withstand voltage level (approximate relationship Rds (on) ∝ Vbr ^ 2.4~2.6), which is the biggest challenge faced by high-voltage MOSFETs.
Parasitic capacitance:
Universal type: The input capacitor, output capacitor, and reverse transmission capacitor are relatively small.
High voltage type: Due to the need for a larger area and longer drift region, its parasitic capacitance (Ciss, Coss, Crss) is significantly larger. This directly affects the switching speed.
Switching speed:
Universal type: Fast switching speed (short opening and closing time). The small capacitance and low gate charge make it suitable for high-frequency switching applications.
High voltage type: The switching speed is relatively slow. Large capacitors require longer charging and discharging time, which limits their maximum operating frequency. The switch loss is also greater (Psw ∝ 0.5 Vds Ids (tr+tf) fsw, where tr/tf is larger).
Reverse recovery feature:
Universal type: The reverse recovery charge and recovery time of its body diode are usually not the main focus.
High voltage type: The reverse recovery characteristics (Qrr, trr) of its body diode become very important, especially in bridge topologies (such as half bridge, full bridge), improper recovery may lead to direct current and efficiency decline. Often needs to be used in parallel with fast recovery or Schottky diodes, or with specially optimized devices.
Application scenarios:
Universal MOSFET:
Low voltage DCDC converters (such as motherboard VRM, POL converters)
Power management for battery powered devices such as mobile phones and laptops
Low voltage motor drive (such as fans, small drones)
Load switch
Logic level control circuit
High voltage MOSFET:
Primary side switch of offline switch mode power supply (SMPS) (such as PC power supply, adapter, LED driver)
Power factor correction circuit
Industrial motor drive (such as frequency converter)
High voltage DCDC converter
Induction heating
Electric welding machine
Automotive high-voltage systems (such as OBC, DCDC)
Cost and process:
Universal type: usually manufactured using more mature and cost optimized processes, with relatively lower costs.
High voltage type: requires more complex processes (such as thick epitaxial growth), larger chip area to meet voltage requirements, and greater yield management challenges, so the cost is usually higher than that of general-purpose MOSFETs of the same current level.
Summary:
|Features | Universal MOSFET | High Voltage MOSFET (≥ 500V)|
|Core objective | Low conduction loss at low voltage, high switching speed, low cost | Safe blocking of high voltage|
|Key structure | Relatively thin and highly doped drift region | Long and low doped drift region (thick epitaxial layer)|
|On resistance | very low (milliohm level) | significantly high (exponentially increasing with withstand voltage)|
|Parasitic capacitance | small | significantly large|
|Switching speed | fast, suitable for high frequency | slow, high switching loss|
|Body diode recovery | usually not important | very important (Qrr, trr)|
|Typical withstand voltage |<250V (commonly 30V, 60V, 100V) | ≥ 500V (commonly 600V, 650V, 800V, 1000V+)|
|Main applications | Low voltage DCDC, battery management, load switch, small motor | Offline SMPS primary side PFC、 Industrial motor drive, high-voltage converter|
|Relative cost | lower | higher|
Simple metaphor:
Compare current to water flow and voltage to water pressure.
A general-purpose MOSFET is like a short and thick water pipe, with low water flow resistance (low Rds (on)) and fast response (fast switching speed) when opening and closing valves (gates) under low to medium water pressure.
High voltage MOSFET is like a long and thick walled water pipe, specially designed to withstand extremely high water pressure. Although the water flow resistance is greater (high Rds (on)), and opening and closing valves is more laborious and slow (slow opening and closing speed), its core value lies in the ability to safely block high-pressure water flow.
Understanding these differences is crucial for making the right choices in circuit design. High voltage applications must use high-voltage MOSFETs to ensure safety and reliability, even if sacrificing some efficiency and speed; In low-voltage and high-efficiency applications, general-purpose MOSFETs are a better and more economical choice.