Abstract
KEYWORDS:
automotive, power systems, supply voltage regulation, interleaving technique
ABSTRACT:
Increasing use of electrical power to drive automobile subsystems is seen trend in advanced automotive power systems. The automotive industry is faced with increasingly strict environmental regulations, which require that automotive module
designs include real-time monitoring and off-line fault isolation. As a result, new designs have been developed to significantly improve reliability and durability of these key components. Advances in manufacturing and process technology are what will enable companies to produce increase performance in microcontrolers at affordable prices. The next generation of automotive microprocessors will operate at significantly lower voltage that implies higher currents. Also, these microprocessors will require a higher accurate supply voltage regulation comparative with stabilization obtained by a centralized power system. The voltage regulator module (VRM) is playing an
increasingly important role in power supply vehicle systems. Power supply circuitry is
usually less complex than the circuitry being powered. The voltage rating of automotive power electronics is predominantly determined by the transient immunity requirement, which considerably exceeds the maximum operating voltages of 12V and 24V automotive power systems, and imposes a large cost penalty. In contrast, the
emerging 42V systems require a much improved bus voltage regulation to maintain system affordability.
This paper analyses a VRM supplying power from a 12 V / 42 V to a 1,5 V, max 45 A load and a current slew rate of min 40 A/ms. For a max 15 A current load a good solution, which maximize performance/cost coefficient it is represented by buck converter structure. If we will try to use this structure for 45 A current load at imposed
parameters the size of the VRM would increase because a large amount of the output filter would be required. Using the interleaving technique the VRM size remains in reasonable limits. The interleaving technique is implemented by paralleling a number of converter power cells which are controlled by phase-shifting (interleaving).
For improve the VRM transient response without sacrificing stability by keeping the control loop gain low during steady-state normal operation a simple control scheme was proposed: interleaving control with limited ramp (ICLR). The benefits of ICLR are: a very good load current distribution among interleaved phases compared with conventional interleaved control (CIC), interleaving control with constant slope ramp
(ICCSR) and interleaving control with variable slope ramp (ICVSR), which reduces the output voltages for a step up load current, have a limitations for a step down load current compared with ICLR.
Design consideration for 12 V (42 V)/ 1,5 V, max 45 A, ICLR VRM are presented in full paper. A model is used in simulating the current/voltage response and calculates the efficiency and current sharing error among three interleaved phases.