Mornsun IGBT/SiC Gate Driver Power Supplies

Gate driver isolation is required because IGBT/SiC emitters/source switch between ground and high voltage (up to 1000V+). Control circuits operate at low voltage (3.3V/5V) and must be isolated from the power stage for safety. Isolation also provides switching noise immunity by preventing high dv/dt noise from coupling to control circuits. Bootstrap supplies have limitations in duty cycle and startup, while isolated supplies provide continuous power. Key parameters include isolation voltage exceeding system voltage, low isolation capacitance (<10pF) to minimize common-mode current, and high CMTI (50-100kV/us) to withstand switching transients.

Always use isolated supplies for high-side gate drivers and when safety isolation is required. Choose based on system voltage and switching speed.

Common Mode Transient Immunity (CMTI) is the ability of an isolated component to maintain correct operation during rapid common-mode voltage transients, measured in kV/us. CMTI is critical for gate drivers because SiC MOSFETs switch in <50ns with dv/dt up to 50-100kV/us. High system voltages (600V to 1700V) and rapid switching create stress on the isolation barrier. CMTI events can cause false triggering or damage to power devices. IGBT applications typically need 15-30kV/us, while SiC MOSFET applications require 50-100kV/us. Higher switching frequencies require higher CMTI ratings.

Choose supplies with CMTI rating at least 2x your application's maximum dv/dt. SiC applications need 50kV/us or higher.

Use IGBT supplies (QA151C3) for standard industrial motor drives with IGBT devices, switching frequency below 20kHz, DC bus voltage below 600V, and dv/dt below 20kV/us. Use SiC supplies (QA-R4G0315T) for SiC MOSFET devices, switching frequency above 20kHz, DC bus voltage above 600V, and dv/dt above 20kV/us. Key differences: SiC supplies have 6000V vs 3000V isolation, 100kV/us vs 15kV/us CMTI, 10pF vs 15pF capacitance, and +15V/-4V vs +15V/-8V output voltage. SiC supplies are higher cost but necessary for high-performance applications.

Use QA151C3 for IGBT drives to optimize cost. Use QA-R4G0315T for SiC drives or when highest reliability is required.

Isolation capacitance is the capacitance between the isolated input and output sides of the power supply. Low capacitance (<10pF) is important because high dv/dt on the power side can couple common-mode current through the capacitance to the control side. This can cause noise, false triggering, or EMI issues. Lower capacitance means better noise immunity and less common-mode current. QA-R series has 10pF typical, while QA series has 15pF typical. For high dv/dt SiC applications, ultra-low capacitance is critical.

Choose lowest capacitance for high dv/dt applications. SiC applications need <15pF, preferably <10pF.

PCB layout guidelines for gate driver supplies: Maintain creepage and clearance distances per safety standards. Use slots or barriers to increase creepage. Keep high-voltage and low-voltage circuits well separated. On input side, keep traces short and wide, place input capacitor close to pins, connect to control ground. On output side, place output capacitors close to pins, connect to gate driver IC ground, minimize loop area, keep away from high-voltage nodes. Use 4-layer PCB with ground planes. Follow manufacturer layout recommendations.

Maintain proper isolation spacing, minimize trace inductance, and follow manufacturer layout guidelines for reliable operation.