HV Products Integral to Auto Sector

By Fairchild Semiconductor

While the debate on EV/HEV tax credits, battery technology, and infrastructure has been a constant over the last few decades, high voltage technology for Automobiles remains a key enabler for advanced applications. Electric Vehicles in particular still face infrastructure hurdles. Both HEV and EV platforms are challenged by battery costs and reliability. While Hybrid Electric and Electric Vehicles face competition from advances in ICE efficiency (i.e. Direct Injection), high voltage has many application opportunities across platforms. Regardless of which vehicle technologies are broadly accepted by the consumer, and which become niche markets, the use of high voltage semiconductor components will continue to increase on the world market.

ICE Ignition

The oldest and often overlooked application of high voltage semiconductor devices in vehicles is for ignition. The basic principle of using a coil or magneto, and a switch to interrupt current has not changed. The use of IGBT switches saw rapid increases as distributorless ignition systems became manifest decades ago. With the demise of coil packs and ignition wires being replaced by individual coils, the market again expanded. With individual coils, with and without integrated electronics, there are as many switches as there are cylinders.

Technical innovation continues, especially in ignition products for Direct Injection engines. Smart ignition products include features such as auto peak current detect, maximum dwell protection, multispark control, and soft shutdown. Fairchild has a leading position in this market, and offers a full array of both standard and custom product. The core IGBT EcoSPARK^® technology delivers best in class voltage drop and current density for optimal designs. Fairchild Ignition IGBT solutions are available as packaged devices with and without smart controls and passives, and in die form.

Power Conversion and Accessory Power

Boost Converter - The HEV and EV electrical architectures have multiple DC-to-DC conversion needs. In most powertrain architectures, a main boost converter steps up the widely varying battery pack voltage, to a constant high voltage rail used to power the Traction Drive. The input voltage is usually between 180V to 350V depending on the battery state of charge, and the topology of the stack. The output voltage is 450V and up. High Current devices are required for this, as the power output can be 100kW+. These designs use either packaged devices, or large scale die assembled onto a thermal shelf. Liquid cooling is nearly universal.

12V Step-Down Converter - The battery voltage also must be stepped down to drive traditional accessories, and in HEVs to provide for engine starting. Converters can be powered directly from the battery, or from the more stable traction drive power rail. These normally range from 1.5kW to 3kW, replacing the output of the traditional alternator. Step Down converters normally use HV Power MOSFETs or High current IGBTs. IGBTs with co-packaged diodes can provide additional benefits in bidirectional converters.

Fairchild provides a family of High Current packaged IGBTs in the 50 to 70A range that are AECQ101 Qualified for these applications.

Traction Drive

Traction Drive requires large scale high voltage silicon, compatible with special thermal mounting. There is little standardization, as each design is highly proprietary. Silicon suppliers must create unique devices to meet each application specific design. Generally, very large 600V die IGBTs are used, with future systems possibly using 1200V. Fairchild is engaged in this segment, with Trench IGBT technology.

Accessory Drive

The benefits, or even necessity, in removing belt-powered accessories from the engine drives a need for AC or Brushless DC motor drives of all sizes. Electric Power Steering is a prime example, providing benefits in reduced fuel consumption in both traditional ICE and HEV platforms. While systems today are low voltage for the most part, operating at 12V, future solutions include both medium (48V) and high voltage.

Basic functions for engine operation such as Fuel Pumps, Transmission Pumps, Oil Pumps, Cooling Fans, and Coolant Pumps also benefit from electrically powered operation. Again, low voltage solutions today have future cousins that will operate from higher voltages. EV’s in particular have high voltage accessory heating and circulation equipment already in the field.

Fairchild has discrete products in the Medium and High Voltage MOSFET and IGBT tool kit to aid today’s designers. Further, modular solutions that provide a complete system solution for 3 phase motor drive are available from the Automotive APM (Smart Automotive Power Module) family up to 600V.

Figure 1: Bank of batteries in an electric vehicle

Charging Systems

Charging systems for EV’s and Plug-in Hybrids can be both off-board and on-board. High charge rate systems that are off-board can require Power Factor Correction. For compactness, PFC and DC-to-DC conversion are often done at frequencies beyond the capability of IGBT technology. High Voltage, high performance MOSFETs are required that minimize losses and control EMI. Fairchild SuperFET^® devices and SuperFET 2 devices, with AECQ101 rating are available in various packages for different size charging systems to meet customer needs.

Additionally, High Current, High Voltage Gate Drivers are available with AECQ100 rating to drive Fairchild high voltage MOSFETs.

AC Power Inverter

The need for power of consumer portable devices with vehicles has rapidly grown. OEM installed power inverters from 150 to 250W are becoming common. Larger inverters for work trucks are offered in the 400W+ range for charging portable batteries for tools and running small equipment.

Fairchild has high voltage MOSFETs and Rectifiers specific to this market. SuperFET 2 high voltage MOSFETs include the EasyDrive family that includes a series gate resistance to reduce gate ringing, and lower EMI in systems operating in the tens of kilohertz range common for true sine wave inverters.

HVIC Half Bridge Gate Drivers with AECQ100 rating are available to drive the secondary high voltage output stages.

Fairchild Applications Web Pages

Fairchild has introduced a new series of Automotive Applications web pages to help designers understand our product offerings for the latest Automotive Electrical architectures. From power conversion to motor drive, these pages can aid designers in understanding Fairchild’s solutions capability.

Featured Products include:

• IGBTs for Motor Drive Applications up to 70A
• Automotive Smart Power Modules from 12V to 600V
• High Voltage SuperFET MOSFETs and SuperFET 2 MOSFETs
• High Voltage Rectifiers – Single and Dual from 4A to 30A in DPak, D2Pak and TO247
• High Voltage Gate Drivers – High Side and Half Bridge HVICs from 300mA to 4.5Amps
• Customer Die for Traction Drive and Inverter Applications
• EcoSPARK devices, EcoSPARK 2 devices and Smart Ignition IGBTs