Electric Vehicle Technologies

Dynex has developed a number of technologies specifically for EV applications. These include double sided cooled IGBT modules with a wire-bondless design and active gate driver technologies. All technology has been designed and tested to meet automotive qualifications and embrace the demands of ISO26262 for functional safety.

Double Sided Cooling Technology

In today’s industry standard industrial power modules only single sided cooling is utilised where the IGBT and parallel diode silicon devices are soldered to a ceramic substrate which, in turn, is soldered to a metal baseplate for attachment to the cooling system. The electrical connections from the top of the silicon chip are made with wire-bonds that connect down to the substrate. Clearly, it can be observed that heat is only removed from the back side of the silicon that is soldered down.

In contrast to this, the wire-bond process is eliminated and replaced by another substrate that is soldered to the top of the silicon chip. This, in turn, attaches to a second cooling plate. The difference in cooling effectiveness is very clear in that the surface area of the silicon in contact with a cooling system is almost doubled.

The construction of the power module utilises high-performance materials and processes to further improve the performance. These include Aluminium Nitride (AlN) substrates and advanced solders and processes.

Silicon Device Choices

A new IGBT and diode chip technology has been developed specifically for these automotive applications. This new silicon family introduces the following features:

Feature Benefit
Low VCE(on) Trench IGBT Technology Reduced conduction losses
Increased voltage from the industry standard 650V to 750V High voltage allows faster-switching speed for increased efficiency and improved energy consumption.
Optimised balance of switching losses and conduction losses Overall efficiency is a combination of switching and conduction losses and there can be a trade-off between the two aspects of the design of the silicon.
New Solderable top metal process Normal silicon devices have aluminium top metal that is suitable for wire bonding. This new construction has required the development of a top metal process suitable for soldering.

 

Silicon Carbide (SiC)

Dynex is actively developing a new family of Silicon Carbide products which can be considered for application in the automotive products. Both SiC diodes and MOSFETs are under development. In addition, Dynex can also use die from other companies to use in the power module designs.

DSC Advantages

Double-sided cooling together with the planar construction has a number of advantages over traditional approaches:

Feature Benefit
Decreased thermal resistance (approx. -30%) through double-sided cooling Increased power output for the area of silicon and volume of the power assembly
Increased reliability through wire-bonds being replaced by the planar construction resulting in increased power cycle capability Lifetime and reliability are increased
Reduced inductance of the power path through the planar construction Lower inductance allows the power devices to be switched faster which reduces energy consumption
Improved thermal gradient across all silicon Improved system reliability and lifetime
Ultrasonically bonded busbar terminals Enhanced reliability
Parasitic power emitter inductance sensing Extra power path monitoring terminals allow the gate driver part of the system to actively control the switching transitions that result in improved efficiency.

 

Active IGBT Gate Driver

State of the art power inverters include IGBT power semiconductors as the active devices. The losses that these devices exhibit are a combination of the losses while they are conducting the power and extra losses that occur as they switch. Typically in modern automotive motor inverters, the switching frequency is around 10kHz and this is chosen as a compromise between efficiency and accurate control of the motor.

A traditional voltage source resistor based gate driver has to be optimised to control the switching as a compromise to all these aspects. Dynex’s new active driver technology can decouple these events to allow more control over individual aspects of the switching transition.

In a traditional gate driver, the resistor is chosen to give the required parameters at the worst point. The new Dynex technology allows the system to give the desired dI/dt or dV/dt at any point. This creates a number of significant system advantages:

Feature Benefit
High-Performance Active Gate Driver Technology

Active dI/dt control

  • Control of turn-off overvoltage spike
  • Control of diode peak current at turn-on
This translates to improved reliability and efficiency in switching through better use of the power device safe operating area.
Active dV/dt control Limit of maximum dV/dt further optimises losses but also potentially allows relaxing of motor filter requirements for reliability. Control of EMC emissions.
No active clamp requirement Many gate drivers incorporate an active voltage clamp to protect the IGBTs from the turn-off overvoltage spike. This limits turn off switching speed and also the maximum DC bus that can be used. The dI/dt control system means that this protection is not required and the product can operate over a wider range.

Comprehensive protection strategies

  • Controlled dI/dt under short circuit conditions
  • Fast over current detection technology
  • All power supplies and gate drive levels monitored
Improved reliability and safety under adverse operating conditions and during failure modes

 

Dynex Integrated Power Unit (IPU)

The Dynex IPU is characterised by a high degree of integration through the use of new bonding technology, bespoke module packaging and double side cooling structure thereby meeting the harsh requirements of HEV/EV.

Further information on the Dynex Integrated Power Unit (IPU) head to the Dynex IPU product page here.

Dynex Highly Integrated Power Assembly (HIPA) 

Dynex’s Highly integrated Power Assembly (HIPA) is a three phase IGBT module with double side cooling plates resulting in compact size and high performance for EV/HEV applications.

Further information on the Dynex Highly Integrated Power Assembly (HIPA) head to the Dynex HIPA product page here

Custom Electric Vehicle Systems

The IPM and IPU products represent a demonstration of the Dynex core EV technologies and for the majority of electric vehicle applications, these technologies are customised. These technology platforms are inherently designed to be scalable in power and features to meet the requirements of a particular OEM project. Some examples of scalable features include:

  • Power output. Inverters from 20kW to 300kW are already in development.
  • IGBT voltage rating. Initial platforms are based on 650/750V IGBT but 1200V can also be implemented for 800V DC bus applications.
  • Switching frequency. Standard products are based on PWM frequencies of 10-14kHz but other developments can address special motors that require 20kHz+ frequencies.
  • Control algorithms. Dynex implements their own advanced motor control algorithms but understands that some OEMs want to apply their own proprietary technology. The Dynex inverter hardware platform can be used to embed the customer’s own control IP.

Capabilities

Test & Verification Capabilities

Dynex has invested in a dedicated test and verification facility for EV product development.

  • E-Motor Emulator
  • E-Storage Emulator
  • HALT/HASS Testing Chamber
  • Thermal Shock Testing Chamber
  • Mentor Graphics Power Tester 600A—Real-Time Failure Diagnostics for Multiple Automotive IGBTs
  • Stratasys 3D-Printer

Manufacturing Capabilities

Dynex employs cutting edge manufacturing processes in the range of EV power products:

  • Busbar Ultrasonic Welding

  • Silver Sintering

  • Planar Bonding

For further information of any of the Dynex capabilities please contact us.