By Why Device Selection Deserves Care
The power device is the most consequential component in a converter. It sets the voltage class, the losses, the heatsink size and, in many cases, the reliability of the whole product. Choosing the wrong device late in a project costs time and money, which is why a structured selection process pays for itself. This guide walks through a repeatable method for selecting a Silan device, using IGBT discretes, IGBT modules, SiC MOSFETs and IPM as the candidate set.
Step 1: Fix the Voltage Class
Start with the DC bus. A 380 to 480 V AC supply rectifies to roughly 560 to 680 V, and switching overshoot adds more, so a 1200 V device provides the necessary margin. Lower-voltage systems may use a 600 V or 650 V class. Never choose the voltage class from the nominal bus alone; include the switching overshoot you expect, because the device must survive the peak, not the average.
Overshoot and Margin
The commutation loop inductance and the switching speed set the overshoot. A module or IPM shrinks the loop compared with discretes, which reduces overshoot, but the DC-link layout and capacitor placement still matter. Leave at least fifteen percent margin between the worst-case peak and the device's blocking voltage, and measure overshoot at the device terminals during validation.
Step 2: Set the Current
Continuous current plus overload current sets the current rating. A motor drive may draw 150 percent of rated current for several seconds during acceleration, and welding equipment draws large repetitive pulses. Choose a device whose rated current covers the worst case at the expected case temperature, then verify junction temperature with the thermal path. Current ratings are specified at a case temperature, so a hot environment requires derating.
Switching Frequency
Switching frequency is the next filter. Below about 15 kHz, conduction loss dominates, so a low saturation voltage silicon IGBT is efficient. Above that, switching loss grows quickly, and a SiC MOSFET becomes attractive because it switches fast with far lower loss. This is the single most important decision between silicon and silicon carbide.
Step 3: Choose the Integration Level
Silan offers three levels of integration. A discrete IGBT or SiC MOSFET gives the most circuit flexibility. An IGBT module integrates multiple switches and diodes in one package, reducing parts and assembly. An IPM goes further and adds the gate drive, the protection and the inverter bridge, so a microcontroller drives it directly. The right choice depends on current level, board space, production volume and how much gate-drive work you want to own.
Discrete, Module or IPM
Use discretes when you need full control of the topology, modules when you want integration with a custom gate drive, and IPM when you want the simplest, most compact power stage. Many designs combine a module or discrete bridge with an IPM for an auxiliary axis.
Step 4: Confirm the Thermal Design
Thermal design decides reliability. Begin from the datasheet junction-to-case thermal resistance, add the interface and heatsink resistance, and verify junction temperature at worst-case current and ambient. Use a thin, uniform thermal interface material and mount the device flat with the specified torque. For SiC, use the hot on-resistance value, not the 25 C figure.
Step 5: Validate on the Bench
Before committing to volume, build a prototype and measure gate waveforms, turn-off overshoot and case temperature under load. Compare the measured loss with the datasheet estimate and adjust the gate resistor, dead time and heatsink as needed. Measured data removes the guesswork and prevents late-stage surprises. BeiLuo's FAE team can support this validation and compare candidate devices on your operating point.
Documentation and Supply
Every Silan device BeiLuo ships is factory-traceable and includes an import declaration, a certificate of origin and a RoHS compliance file. Mainstream devices are held in regional stock, so a validated design moves smoothly from prototype to production. Selecting the right device is the first step; keeping it supplied is the second, and BeiLuo supports both.