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Technical Paper

Power Module Design Verification for xEV Application Under Extreme Conditions

2017-03-28
2017-01-1246
Power modules play a key role in traction inverters for vehicle electrification applications. The harsh automotive operating environment is a big challenge for power modules. The paper highlights the challenges for power modules usage in electrified vehicles (xEVs), and proposes a design verification procedure for such application in order to ensure the reliable operation under all conditions. First, power modules operate in all climate zones and are exposed to a wide ambient temperature range underhood from -40°C to 105°C. A typical automotive power module should therefore withstand a junction temperature from -40°C to up to 175°C without exceeding its safe operating area (SOA), e.g. avalanche breakdown voltage, maximum current, and thermal limit. Second, an inductive induced high voltage spike could be generated during the power semiconductor fast switching at high voltage and high current conditions.
Technical Paper

Traction Inverter Design with a Direct Bypass to Boost Converter

2017-03-28
2017-01-1247
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.
Technical Paper

Switching Frequency Optimization of Boost Converter for HEV Applications

2017-03-28
2017-01-1236
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.
Journal Article

A Smart Gate Driver with Active Switching Speed Control for Traction Inverters

2017-03-28
2017-01-1243
The IGBTs are dominantly used in traction inverters for automotive applications. Because the Si-based device technology is being pushed to its theoretical performance limit in such applications during recent years, the gate driver design is playing a more prominent role to further improve the traction inverter loss performance. The conventional gate driver design in traction inverter application needs to consider worst case scenarios which adversely limit the semiconductor devices' switching speed in its most frequent operation regions. Specifically, when selecting the gate resistors, the IGBT peak surge voltage induced by fast di/dt and stray inductance must be limited below the device rated voltage rating under any conditions. The worst cases considered include both highest dc bus voltage and maximum load current. However, the traction inverter operates mainly in low current regions and at bus voltage much lower than the worst case voltage.
Technical Paper

Enhanced Gate Driver Control Circuit for Vehicle Traction Inverter

2019-04-02
2019-01-0608
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 results in high switching loss to 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 microcontroller 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.
Technical Paper

Design of a SiC Based Variable Voltage Converter for Hybrid Electric Vehicle

2019-04-02
2019-01-0605
Variable Voltage Converter (VVC) or generally called Boost Converter is adopted in Power-Split structure of hybrid electric vehicles (HEVs) to optimize the Electric-Drive (e-Drive) system design and improve system performance. The power semiconductor, usually the Silicon (Si) IGBT and diode as the key component, impacts the VVC and the whole vehicle performance. The development of new type of semiconductor, Silicon Carbide (SiC) MOSFET, brings the new opportunities to VVC for further design optimization and performance improvement. First of all, SiC MOSFET has lower conduction loss (especially at low current range) and switching loss than traditional Si IGBT, leading to the loss reduction of TBD% at wide VVC power range. In addition, SiC MOSFET is expected to be operated at higher switching frequency due to its fast switching speed and low switching loss, which helps to increase VVC switching frequency without sacrificing efficiency.
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