Abstract
Automotive industry requires integrated circuits with both low cost, to maintain product competitiveness, and high efficiency, moving towards solutions as green as possible. Each electronic device within the car needs for a regulator to provide a steady supply to ensure correct and safe operation. Among all regulator, DC/DC Converters are the most valid solution to achieve a high efficiency-price ratio. The DC/DC Converter needs for a control loop to monitor the load operation. The basic control loop topologies are well known in the state-of-the-art. The paper presents a DC/DC Buck Converter for automotive applications designed in low cost technology with an upgraded version of the Peak Current Mode Control which uses a constant off-time. For chip area reduction, an n-channel power-DMOS is chosen as power transistor. The design of each block composing the circuit is presented. To guarantee DC-DC Buck converters high-efficiency and low cost (in terms of external components) increasing switching frequency is mandatory. A 1.5 MHz switching frequency has been chosen to reduce external components size. The device is optimized by design to be able to achieve 94.4% efficiency using a 3V 3A load. The post-layout simulations of the system are shown, confirming the expected circuit behavior also including the presence of wiring parasites. A PCB is also designed to test the packaged die to ultimately demonstrate the chip’s robustness and suitability in a real automotive application.
Highlights
Nowadays, thanks to their higher efficiency-price ratio, the switching DC/DC converters are covering almost all automotive applications, replacing the conventional converters
To keep the cost of such systems competitive, integrated circuits are required, which integrate external components as much as possible, or which work with smaller external components
In many DC-DC converters applications there is an external diode to charge the bootstrap capacitor and an external power transistor to supply the load [8, 9]. These external components affect the size of the PCB
Summary
Thanks to their higher efficiency-price ratio, the switching DC/DC converters are covering almost all automotive applications, replacing the conventional converters. In many DC-DC converters applications there is an external diode to charge the bootstrap capacitor and an external power transistor to supply the load [8, 9] These external components affect the size of the PCB. To reduce the size of the external components it is necessary to improve the gate driver and level shifter design, minimizing the problems related to the switching speed. These blocks require the development of new solutions. The proposed gate driver, bootstrap circuit and level shifter are designed for a load that requires a constant current of 3 A with an input voltage range between 4.5 V and 27 V. The choice of the power-DMOS is based on the switching frequency and losses [10]
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