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Today, advanced LED driver designs are being developed with electronic components that deliver higher luminescence and improved energy efficiency at lower cost. Current components are typically a fraction of the cost compared to five years ago. Newer technology also has an operational advantage of approximately half the cost of halogen or Xenon. But the foremost feature is the flexibility and “cool” look that enhances the vehicle’s design and increases customer demand. These products enable manufacturers to develop higher-power LED headlight clusters that perform well at elevated current in a smaller footprint. Specific inductors support a more advanced LED driver design that handles higher voltages and a wider array of high-power LEDs that can operate “bend light” and dimming functions to improve roadway safety.
Eaton has a broad range of inductors that are technologically advanced to handle higher temperatures (up to +155 °C) and higher power density. The footprint can be decreased by as much as half with the newer inductors. A popular inductor used to require 12.5 mm x 12.5 mm on the board. Today’s version requires just 8 mm x 8.5 mm with the equivalent performance of several years ago. This competitive pricing generates significant opportunities for distributors to sell into manufacturers. Applications are becoming more and more sophisticated, trending well beyond two or three LED drivers per car. Today, full LED lighting solutions specifying 20 power inductors per board and 40 per car are not unrealistic. It should be noted that the solutions discussed in this document are not commodity products. They must be designed into various automotive applications. In order to successfully optimize their designs, LED designers demand strong support from suppliers, distributors, and Eaton.
A Single-Ended Primary Inductor Converter (SEPIC) allows the output voltage to be greater than, less than, or equal to the input voltage in DC-DC conversion.
Typical vehicular applications include daytime running lights (DRLs) and, more recently, full LED headlights, which supports all of the lighting options of low-beam, high-beam, fog and turning indicator lights using a single SEPIC driver circuit. This single circuit is able to output the optimal LED driver voltage and currents based on the actual number of light features turned on. Eaton’s off-the-shelf AEC-Q200 Grade1 coupled inductors (DRAQ family) may power SEPIC drives of up to 40 W, which is sufficient for a standard LED headlamp. SEPIC drives make complete LED headlights affordable to the general public, not just luxury car drivers.
Figure 1.
SEPIC circuit
Boost and Buck circuits are used for the most sophisticated LED headlights, providing sufficient power to drive multiple light features all the way up to 120 W per lamp. This type of circuit topology includes a powerful boost converter which normally boosts the battery voltage to a maximum 60 V. This elevated voltage is then bucked down to the required voltage level to power different LED strings of the headlight.
The different light strings may be composed of a matrix of uniform LEDs (normally 32-1024 pixels) or strings of power LEDs and some standalone power LEDs. These complex headlight units can control the light intensity based on the road conditions, driving speed, steering wheel position and upcoming traffic sensed by the Advanced Driver Assistance System (ADAS). The complex LED drivers adjust the light intensity and focus automatically for ride enhancing safety on the road, whether day or night.
Some laser LED diodes may illuminate all the way up to 600 meters, allowing high-speed driving during the evening. These drivers require robust inductors with high power density and 10-20 pieces per lamp to properly manage the various voltage and current requirements. When selecting components, it is important to choose those with high efficiency, high temperature capability, high heat dissipation capability and stable operation at all temperatures ranging from -40 °C to +125 °C ambient. Eaton’s HCM(1)A inductor product line is designed specifically to take this challenge with a wide variety of inductances and size options.
Figure 2.
Boost and buck circuit
It is critical for manufacturers to work with suppliers who can deliver automotive-grade, high power inductors that offer low electromagnetic interference (EMI) and higher operating temperature, which are essential for obtaining efficient DC-DC conversion. These robust inductors are designed to withstand harsh environmental, electrical, and mechanical conditions. Many of the more recent applications demand that the inductors perform at temperatures from -40 °C to +155 °C, representing the same inductance roll-off characteristics across the entire temperature range. Tight thermal coupling can ensure effective heat dissipation under high current conditions. Utilizing a variety of sizes and higher inductance values allows automotive designers to operate at higher voltages needed to drive multiple high-power LED arrays for headlights and daytime running lights.
With the rapid increase of automotive electronics components in vehicles, maintaining a low EMI is essential. Inductors are recommended to be magnetically shielded, making them suitable for virtually all applications throughout the vehicle. This gives automotive engineers design flexibility. Additionally, these inductors should be AEC-Q200 Grade-1 qualified and appropriate to operate in temperatures of up to +165 °C, making them popular for engine compartment applications including electric motors, pumps, and engine control modules, as well as for lighting body and security systems.
DRA
Employing time-tested technology, the DRA remains the most efficient solution on the market today. The high-temperature ferrite-based DRA features the lowest DCR, high lsat current, and enhanced shock and vibration performance, optimized for peak current operation. With its shielded drum core construction, the DRA can be manufactured to support up to 1000 uH inductance. That makes this inductor ideal for most automotive applications including LED lighting, powertrain control module (PCU), engine control unit (ECU), transmission control unit (TCU), and hybrid electric vehicle (HEV) inverter controller/charger.
DRAQ
The DRAQ inductor features two closely coupled windings with 200 VAC winding isolation, and enhanced shock and vibration performance, which is optimized for best peak current operation. DRAQ is designed to function at +125 °C ambient and +165 °C total temperature operation. Typical applications include LED DRL, ADAS, Infotainment, radar power, and any SEPIC converters.
HCM(1)A
The HCM(1)A high-power-density inductors from Eaton boasts a lower core loss than other powdered iron solutions. It also possesses higher Isat, lower DCR, and soft roll-off characteristics. Using HCM(1)A inductors instead of DRAs helps to reduce the required PCB footprint to half since the HCM(1)A has higher power density and the performance is stable at all temperatures, allowing no derating at high temperature operations, which was a common practice using ferrite inductors. It is magnetically shielded to reduce EMI. The HCMA operates at +85 °C ambient and the HCM1A operates at +125 °C ambient with a maximum total temperature of +125 °C and +155 °C respectively. It is optionally fully coated externally to provide 100 percent corrosion protection for harsh environments. Common applications include ECU, infotainment systems, TCU, LED lighting, water, fuel, and oil pumps, engine cooling fans, and HVAC units.
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