How to select diodes suitable for high-voltage energy systems?

一, Technical classification and core characteristics of high-voltage diodes
1. Classify by material and structure
Silicon based high-voltage diode: the mainstream choice, with a withstand voltage of several thousand volts and a long reverse recovery time (microsecond level), suitable for power frequency rectification.
Silicon carbide (SiC) high-voltage diode: with a withstand voltage exceeding 3300V, the reverse recovery time is shortened to nanoseconds, and excellent high-temperature performance (junction temperature can reach 200 ℃), suitable for high-frequency switching scenarios.
Glass passivated (GPP) diode: By firing a glass layer on the surface of the PN junction, the voltage stability and moisture resistance are improved, with a typical voltage resistance of 600V-1200V.
2. Classify by function
Rectifying diode: converts AC to DC, with core parameters of maximum rectified current (IF) and reverse recovery time (Trr).
Fast Recovery Diode (FRD): Trr ≤ 50ns, suitable for high-frequency scenarios such as switching power supplies and inverters.
Schottky diode (SBD): forward voltage reduction (0.3-0.5V), no reverse recovery time, but limited withstand voltage (usually ≤ 200V), requiring series connection to increase withstand voltage.
Transient voltage suppression diode (TVS): response time ≤ 1ns, precise clamping voltage, used for lightning protection and overvoltage protection.
二, Six core parameters for selecting high-voltage diodes
1. Voltage resistance (VRRM/VBR)
Definition: The maximum reverse repetitive peak voltage (VRRM) should be 1.5-2 times higher than the maximum system voltage to avoid breakdown caused by voltage fluctuations.
Selection principle:
DC side of photovoltaic inverter: A 1500V system requires a 1700V diode (such as the Taike Tianrun G3S170 series).
Rail transit traction system: The 3300V system requires a 3300V SiC diode (such as the Taike Tianrun G3S330 series).
2. Flow Capacity (IF/IFSM)
Definition: The average rectified current (IF) must be 1.5 times higher than the system average current; The peak surge current (IFSM) needs to withstand the instantaneous impact during startup or short circuit.
Selection principle:
Industrial motor drive: Choose IF ≥ 2 times rated current, IFSM ≥ 10 times rated current.
Photovoltaic inverter: Select IF ≥ 1.5 times the maximum output current, IFSM ≥ 20kA (8/20 μ s waveform).
3. Switching speed (Trr/Ton/Off)
Definition: The reverse recovery time (Trr) determines the switching loss in high-frequency scenarios; The Ton/Off time affects the system response speed.
Selection principle:
Switching power supply (>10kHz): Select fast recovery diodes with Trr ≤ 50ns (such as ASEMI MUR1660AC, Trr=35ns).
Silicon carbide inverter: Select SiC diodes with Trr ≤ 10ns (such as Taike Tianrun G3S170 series, Trr=8ns).
4. Positive voltage drop (VF)
Definition: When conducting, the voltage at both ends directly affects the system efficiency.
Selection principle:
Low voltage and high current scenarios (such as 48V DC systems): Priority should be given to selecting Schottky diodes with VF ≤ 0.5V.
High voltage scenarios (such as above 1000V): Choose SiC diodes with VF ≤ 2.5V, which can improve efficiency by 3-5% compared to silicon diodes.
5. Thermal performance (TjM/Rth)
Definition: The maximum junction temperature (TjM) should be lower than the device limit value (150 ℃ for silicon tubes, 200 ℃ for SiC tubes); The thermal resistance (Rth) determines the heat dissipation efficiency.
Selection principle:
High density power module: Select TO-247 packaged devices with Rth ≤ 0.5 ℃/W.
Closed environment application: Select devices with TjM ≥ 175 ℃ and reserve derating space.
6. Reliability certification
Key criteria:
Safety certification: UL (North America), TUV (Germany), CQC (China).
Lifetime Test: Tested for 1000 hours using HTRB (High Temperature Reverse Bias).
Packaging reliability: Avoid using axial plug-in packaging and prioritize selecting SMT packaging (such as DFN8 × 8).
三, High voltage diode selection process and case analysis
1. Selection process
Requirement analysis: Clarify system parameters such as voltage, current, frequency, and ambient temperature.
Device classification: Select rectifier, fast recovery, TVS and other types according to functional requirements.
Parameter matching: Screen candidate devices based on core parameters (voltage resistance, current flow, speed).
Derating design: voltage derating by 1.5-2 times, current derating by 1.2-1.5 times.
Reliability verification: Verify the robustness of the device through HALT (High Acceleration Life Test).
2. Typical application cases
Case 1: DC side protection of photovoltaic inverter
Requirement: A 1500V system is required to withstand a surge current of 20kA with an efficiency of ≥ 98%.
Selection plan:
Main rectifier: Taike Tianrun 1700V/50A SiC diode (G3S750P), VF=1.7V, Trr=8ns.
Surge protection: Toshiba HN1D05FE TVS diode (VR=400V, IPP=20kA).
Effect: System efficiency improved by 2%, surge protection response time ≤ 1ns.
Case 2: Rail Transit Traction Converter
Requirement: 3300V system, switching frequency 5kHz, required to withstand 100kA short-circuit current.
Selection plan:
Rectification module: Taike Tianrun 3300V/50A SiC diode (G3S33050P), IFSM=100kA.
Fast recovery diode: ASEMI MUR3060PT (600V/30A, Trr=35ns).
Effect: The system volume is reduced by 30%, and switch losses are reduced by 40%.
四, Future Trends in High Voltage Diode Selection
1. Popularization of wide bandgap semiconductors
SiC diodes have a withstand voltage exceeding 3300V and a forward voltage drop reduced to 1.5V, making them suitable for medium voltage distribution systems above 10kV.
Gallium nitride (GaN) diodes have entered the high-voltage field, with reverse recovery time reduced to less than 1ns.
2. Intelligent selection tool
The supplier provides an online simulation platform (such as Taike Tianrun SiC selector), which automatically recommends device combinations after inputting system parameters.
Digital twin technology is used to predict the lifespan and failure modes of devices under extreme operating conditions.
3. Modularization and Integration
Diode and IGBT/MOSFET are integrated into a single module (such as Infineon EasyPACK series), simplifying system design.
Press Pack packaging enhances the shock resistance and heat dissipation efficiency of high-voltage devices.