Auto Power Supply Applications and Efficiency

Due to recent automotive electrification such as ADAS and Stop-Start Systems, maximizing power efficiency is critical for automotive design consideration. This webcast explains an overview of power supply application including the concept of power efficiency, system power supply topologies, and design considerations.

Transcript

00:00:01 welcome to this on Semiconductor webcast in this webcast will discuss some challenges in the automotive industry as it relates to power supplies and expose you to some innovative solutions to solve these challenges the complexity is associated with power management modules for the automotive industry continue to grow not only duty via traditional challenges like the ability to handle

00:00:23 higher current situations low dumps double battery jumps in the need to draw minimal current conditions but also due to increased demands of automobiles automotive electronics engineers have additional challenges like increasing electronics module content within vehicles driven by customer desire convenience needs safety requirements and the move from mechanical components

00:00:46 to the mechatronics world some of these challenges include falling digital component supply voltages rising currents within digital components growing governmental regulations for co2 emissions and increasing miles per gallon requirements the drive to maximize power efficiency has been one of the core objectives of design thermodynamically energy transfer of

00:01:12 real-world system is not perfect that is input power can never be equal to the output power due to factors like heat dissipation and other system losses this is measured by power efficiency defined as the ratio of the output power divided by the input power hence the losses and form of heat dissipation is manifested in the fraction of the output power generated by a system compared to the

00:01:37 input power let's discuss this concept of power efficiency as it relates to linear and switch mode power supplies as you can see both linear and switch mode power supplies in this example have 2.5 watt power ratings with 5 volt output voltage and 0.5 amp output current but linear the linear regulator has an efficiency of 41% it says it takes six watts of an input power to generate 2.5

00:02:08 watts of output power this loss of power is attributed to heat dissipation across the voltage regulator hence making it a poor choice of a regulator similarly the switch mode regulator on the other hand has an efficiency of 90% saying it takes 2.8 watts of power input power to generate the 2.5 watts of output power power efficiency is a system challenge due to issues like

00:02:35 following supply voltages due to digital components and excessive power dissipation especially in the case of linear regulators this is an overview of system power supply topologies highlighting the evolution of automotive power supplies the pure linear solution in Figure 1 is where the LDO is directly connected to the battery be a non ignition switch length as you can see

00:02:59 the output is from the post lvl this configuration is useful for low power applications in Figure 2 as you can see the buck regulator is connected to the battery-powered Elio when the ignition is switched the buck regulator helps with the switching hence making this configuration an ideal fit for high power applications like advanced driver assistance systems or a

00:03:22 TAS obligations figure 3 shows the addition of a start/stop pre booster which turns on and off on the ignition the boost controller is added for low voltage cranking compliance to meet iso:175 Oh - this configuration is useful for start/stop applications figure 4 is an evolution of the configuration found in figure 3 where the battery powered LDO

00:03:50 has been replaced by the lock we assume current buck and boost controllers this architecture is used for a driver system application for designers it's imperative to understand the considerations of moving from linear to switching regulation and what impact it might have on their designs as discussed earlier linear regulators have poor efficiency due to

00:04:14 excessive heat dissipation and other system losses however advantages of a linear approach include good noise performance a flexible differential voltage range and lower external component count hence consuming less PCB area a switch mode approach fundamentally has higher efficiency as compared to the linear approach however disadvantages include

00:04:38 poor noise performance primarily due to a switching nature a complex feedback loop and a higher external component count that consumes more PCB area let's discuss some design considerations for switch mode power supplies and ways to mitigate their disadvantages one of the first design considerations to consider is electromagnetic interference which can be mitigated by optimizing the PCB

00:05:04 layout and reducing loop areas you can also avoid susceptible frequencies especially those imposed by regulators or by the system environment and you can reduce pick peak emissions by employing techniques like spread spectrum modulation shaping spectral contents and decoupling methods another consideration is the external component count which varies the power consumption of each

00:05:31 application integrated power switches provide a flexible approach to reduce the PCB layout size with low power consumption as compared to out of board power switches the third consideration is the PCB area increasing the switching frequency is achieved by decreasing the size of the inductor and capacitor hence reducing the overall PCB consumption area reducing the PCB area also has the

00:06:00 effect of minimizing conduction and switching losses a fourth design consideration is feedback loop design frequency compensation is achieved by choosing single pole response control schemes you should also select a suitable negative input resistance for post regulators matching the output impedance to avoid oscillations effective use of

00:06:25 simulation tools to understand frequency compensation in the frequency domain will also aid in the development of your design here we will expose you with the increasing demand of start/stop systems in the market due to fuel economy standards and regulated co2 emissions protocols challenges faced by engineers and designers due to the importance of reducing the operating time of an engine

00:06:54 during idle mode to reduce fuel consumption has become the top priority in the upcoming slides we'll discuss this concept of start/stop systems and further detail cranking an engine allows the vehicle's engine to turn on battery power without actually allowing the engine to start when you insert the key for ignition and turn the switch to on a signal is sent to the car's battery upon

00:07:20 receiving this signal the car's battery delivers electrical power to the starter for cranking the engine this leads to severe voltage drop during this cranking mode high-power centralized multi-phase boost and distributed low-power signal phase boost are mainly used to address this problem information communication and entertainment both in and with the vehicle are an integral part of

00:07:48 automotive development the only way to implement today's large choice of navigation entertainment telematics and driver assistance systems is by using high-performance interfaces companies are continually growing their system integration competence and using it to develop smart solutions for integrating and connecting all kinds of different vehicle functions using graphic using a

00:08:11 graphic processor unit single and multi-phase switch mode power supplies with dynamic voltage scaling are used in driver assistance systems which is a great challenge for engineers advanced driver assistance systems our safety and convenience systems developed to provide safer driver experience by assisting a driver in the complex process of controlling a vehicle a Dass

00:08:39 provides features like adaptive cruise control blind spot monitoring lane departure warning night vision lane keeping assist in collision warning systems with automatic steering and braking intervention advancement in these technologies or require high precision and customizable individual power modules and power supplies a test systems require the integration of

00:09:07 various sections of the vehicle like camera GPS radar and rotary encoder all into one module this is achieved by successfully connecting each section using communication techniques like Ethernet ADA systems should comply with ISO 26262 by implementing functional safety of the overall vehicle in safer driver experience ADIS offers a specialized service to the

00:09:33 power supply section by providing watchdog function capability monitoring power supply redundancy and voltage monitoring as you can see from the block diagram from a power supply view for an ADA system this architecture provides a noose numerous advantages such as low noise performance for radar in GPS applications growth and light-duty 48 volt system

00:09:59 sales will continue through the end of the current decade mainly because of the most aggressive campaign and implementing fuel economy and emissions regulations the German luxury vehicle manufacturers like BMW have collaborated to develop a 48 volt system that sets the foundation for more capable start/stop systems that will enable other electrification features 40th volt

00:10:23 configuration combines a dual voltage step up with the well-known advantages of start/stop technology it more effectively captures a vehicle's braking energy provides power for a growing list of electrical loads and simultaneously boosts fuel efficiency possibly by as much as 15% some of the key advantages of 40 in bold architecture are that it provides increased power efficiency

00:10:52 reduces the current delivered to the load and reduces the weight of the wiring harness it also increases efficiency in switch mode power supplies and increasing increases miles per gallon the 48 volt configuration marries with the conventional 12 or 14 volt network using a lead acid battery like those employed in most conventional vehicles

00:11:18 along with a 48 volt lithium-ion battery with the separate 48 volt Network the 12 Wharton 12 volt Network handles traditional loads lighting ignition entertainment audio systems and electronic modules while the 48 volt system supports active chassis systems air conditioning compressors and regenerative braking in addition to this the 48 volt lithium ion battery has more

00:11:43 charging capability making it a better candidate for capturing regenerative braking energy for more information about on semiconductor automotive application solutions contact your local on semiconductor sales representative or authorized distributor or visit us on the web at WWE