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Insulated Gate Bipolar Transistors (IGBT) are widely used for the vehicle traction inverter. Switching characteristics of these devices contribute to the inverter total loss and inverter efficiency is affected by the energy loss during each switching event. Traditional gate driver circuits are usually designed to meet the worst-case scenario and result is high switching loss of the IGBTs. Gate driver turn on and turn off resistances are selected accordingly for the worst-case scenario and their purpose is to protect the device from overshoot voltage that can cause the avalanche breakdown of the device. The gate charge and discharge circuit is usually composed of one or two resistors and the loss during turn-on and turn-off time is not optimized for all of the vehicle-operating conditions. Since microprocessor (μP) monitors the dc-bus voltage, output current and torque command, it can also determine if the device switching speed needs to be changed under different operating conditions.

Direct bypass to DC-DC boost converter in traction inverter increases converter's capability and efficiency significantly by providing a lower loss path for power flow between the battery and DC-link terminal. A bypass using diode is an excellent solution to achieve this capability at low cost and system complexity. Bypass diode operates in the linear operating region (DC Q-point) when the battery discharges through the bypass diode to drive the electric motors. Therefore, thermal stress on the DC-link capacitor is shared between the input and DC-link capacitors through the bypass diode. On the other hand, inverters introduce voltage oscillation in the DC-link terminal which results in unwanted energy oscillation through the bypass diode during battery charging. Both of these phenomena have been explained in details.

A hybrid electric vehicle (HEV) can utilize the electromechanical path to optimize the ICE operation and implement the regenerative brake, the fuel economy of a vehicle therefore gets improved significantly. Bi-directional Boost converter is usually used in an electric drive system to boost the high voltage (HV) battery voltage to a higher dc-link voltage. The main advantages for a system with Boost converter is that the traction inverter is de-coupled from battery voltage variations causing it to be over-sized. When designing this Boost converter, the switching frequency is a key parameter for the converter design. Higher switching frequency will lead to higher switching loss of power device (IGBT +diode), moreover, it has significant impact on inductor ripple current, HV battery ripple current and input capacitor current. Therefore, the switching frequency is one of the most important parameters for the design and selection of both active and passive components.