Thu. Oct 6th, 2022

[Introduction]On the last day of the PCIM Europe exhibition in Nuremberg, Germany, Power Integrations (PI) held a new product communication meeting online. Jason Yan, senior technical training manager of PI, explained an automotive-grade IGBT/SiC (silicon carbide) module driver series products— —SCALETM EV series gate driver board for Infineon EconoDUALTM modules.

He said the new driver board is equally suitable for original, knock-off and other new SiC-based derivative modules, with applications ranging from electric vehicles, hybrid and fuel cell vehicles (including buses and trucks) to large-scale construction, mining and agricultural equipment. Power cars and traction inverters.

Start with functional safety

First, what is functional safety? Jason Yan’s explanation is: “There is no unreasonable risk of hazards due to malfunctions of electrical and Electronic systems or unintended behavior”, such as when a powertrain fails, the vehicle should be brought to a gradual stop rather than abruptly locked up Braking disables control; neither should a power steering failure result in a complete loss of steering, the vehicle can still steer with effort.

He pointed out that the introduction of electronic systems into automotive applications has had a great impact on vehicle safety. The world’s major electric vehicle manufacturers are committed to ensuring functional safety, so that electric vehicles have higher safety and reliability, and avoid unreasonable risks caused by electrical and electronic system failures or hazards caused by unexpected behavior. Functional safety is defined as the level of risk of injury caused by electrical and electronic systems.

Although ISO 26262 is a functional safety standard requirement and is not mandatory, electric vehicles with functional safety must be safer. The Automotive Safety Integrity Level (ASIL) is a risk classification scheme defined by the automotive electronic equipment safety standard ISO 26262, which aims to confirm that system-forced failures occur in a benign (safe) manner. Functional safety generally covers the following vehicle systems.

How should the automotive-grade IGBT/SiC module driver be used?The first and only automotive silicon-qualified gate driver board simplifies design

In specific ways, the safety of technicians, passengers and emergency workers can be protected in emergency situations by active discharge. For example, when the electric vehicle encounters an emergency such as a collision on the highway, or the power steering fails, the DC bus capacitor voltage is discharged to a safe voltage (<60V safety extra-low voltage (SELV)) in the drive system to prevent DC The bus works at a potentially lethal voltage of 400-1200V; the emergency power supply (EPS) also needs to do the same.

For this purpose, active bleed or active short-circuit, as well as active discharge, are required. This may require the gate driver to provide a drive signal under abnormal conditions to create a short circuit (both switches in the half-bridge open) operating state to provide a discharge path. Under normal operating conditions, the upper and lower IGBT drivers are not allowed to execute the same switching command at the same time. In the case of active discharge operation, the driver can be used to adjust the driving signal to prevent the switch from being overheated and damaged during this operation.

In an emergency, the drive motor should be used for braking rather than accelerating the vehicle. Using the motor drive control to alter the timed commutation time of the drive windings to counteract the rotation of the motor can cause the motor to apply reverse torque to stop it (using the active short-circuit function to short-circuit the motor windings).

How should the automotive-grade IGBT/SiC module driver be used?The first and only automotive silicon-qualified gate driver board simplifies design

The first and only automotive-qualified gate driver board

According to Jason Yan, SCALE™ EV is the first and only automotive-grade certified gate drive board on the market, which integrates two enhanced gate drive channels, related power supply and monitoring and telemetry circuits. It helps manufacturers speed up the product development process and simplify product certification time. SCALE™ EV meets automotive-grade certification and ASIL safety requirements, including AEC Q100/101/200, ASIL-B certification (ISO 26262) for ASIL-C/D traction inverter designs.

For standard automotive power modules, SCALE™ EV also supports IGBT or SiC MOSFET module products with a withstand voltage of 1200V, suitable for traction inverters inside electric buses, electric trucks, agricultural and construction vehicles, and can also be used for hydrogen fuel Battery converters, battery energy storage or other applications that require higher reliability requirements for vehicle certification.

The red dotted line in the figure is the low-voltage part. The size of the drive board completely matches the shape of the module, so that the distance between the modules is not affected by the size of the drive board, which is suitable for the design of compact inverters. The insulation level between the high voltage and the low voltage on the driver board meets the reinforced insulation requirements.

How should the automotive-grade IGBT/SiC module driver be used?The first and only automotive silicon-qualified gate driver board simplifies design

Detailed interpretation of SCALE EV performance

The 1200V withstand voltage module driven by SCALE EV is suitable for 400V and 800V busbar systems, and supports both silicon carbide MOSFETs and silicon-based IGBT switches. Its design meets the 5500-meter altitude requirement, the creepage distance is wide enough, and the conformal coating service option is available to meet the technical cleanliness requirements.

Jason Yan said that the new product has obvious advantages in design, with complete advanced protection functions, integrated active short circuit, active discharge of the connected DC bus capacitor, overvoltage limit through active gate soft turn-off control, and gate monitoring , signal transmission monitoring and on-chip temperature monitoring and other diagnostic functions.

How should the automotive-grade IGBT/SiC module driver be used?The first and only automotive silicon-qualified gate driver board simplifies design

The first function of the driver board is to provide a drive signal to the switch, adjust the parameters of the components according to different power switches to achieve the required power switch characteristics, and meet the fault protection response time requirements of different power switches. Active short-circuit mode supports functional safety requirements with short-circuit and overcurrent response times of less than 1 microsecond for SiC MOSFET switches and less than 3 microseconds for IGBT switches. The above protection characteristics can be adjusted according to the different protection time of IGBT and MOS tube.

How should the automotive-grade IGBT/SiC module driver be used?The first and only automotive silicon-qualified gate driver board simplifies design

The second function of the driver board is isolation. The power module of Infineon has a withstand voltage of 1200 volts. This combination can also be used for higher vehicle certification applications such as hydrogen fuel cell converter battery energy storage. Automotive-grade certification can meet the needs of electric vehicle manufacturers to directly purchase inverter assemblies, especially the bus voltage of electric vehicles raised to 800 volts, which is very convenient to use.

The third function of the driver board is protection. Because the voltage of the power switch is relatively high and the current flowing through it is also very large, a protection signal must be provided as soon as possible in any fault condition. The device’s digital telemetry port can provide fault diagnosis and fault information. Through isolated NTC temperature measurement, gate signal inversion monitoring, the fault condition of the IGBT exiting the saturation region is transmitted to the main controller in a bit stream mode to determine how to deal with the fault. In addition, 50-100 peripheral components can be saved by utilizing the active discharge of the DC bus capacitance by the IGBT.

Jason Yan emphasized that the reason for using three half-bridge modules is to ensure the redundancy of faults. Even if one group is faulty, the other two groups can ensure that the DC bus voltage can be discharged. The inverter is usually composed of multiple half-bridges. The upper and lower tubes in the half-bridge are used to simultaneously turn on and discharge the DC bus voltage, which helps to achieve an effective active discharge function.

The interface connection of the SCALE EV board is simple and reliable, and the dual connectors support functional safety requirements. The two connectors are respectively connected to the upper tube and the lower tube drive. During normal operation, there are two connectors connecting the board, and even if one of the top-tube connectors is disconnected, the down-tube can continue to function without rendering the entire half-bridge functional, as the probability of both connectors failing is low .

How should the automotive-grade IGBT/SiC module driver be used?The first and only automotive silicon-qualified gate driver board simplifies design

PI provides comprehensive technical support for SCALE EV, including data sheets, CAD design files for driver board installation and crimping tools, RDHP-2250Q interface board, and matching PC driver board debugging software.

Can be customized for customers

Jason Yan finally said that there is currently only one available model for the SCALE EV solution – 2SP0215F2Q0C, which is suitable for general-purpose EconoDUAL™ modules. If the customer has special modules, such as power modules with integrated silicon carbide or other types of IGBT modules or SiC modules, the switching characteristics can also be adjusted according to their characteristics. It is even possible to redesign the driver board to the dimensions of the new module. The current SCALE EV product will enter full volume production in the fourth quarter of 2022.

Source: PSD power system design, author Liu Hong

The Links:   MT510LV4CN PD57018STR-E