P06004: Air Surveillance Platform for CIS
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Power Supply

Table of Contents

A reliable and high-performance power supply is an essential component of any electronic system. This is especially true for a portable application that demands high-efficiency because a significant electrical system weight is the battery.

Power Requirements

Pareto analysis of power requirements

Pareto analysis of power requirements

The power requirements for the system are given to the right. The majority of the original system's power was to the synchronous DC motor that provided thrust for flight. The rest of the system is powered by a triple-output DC switching supply that meets the following requirements:
Power supply requirements
Targets Input voltage (V) Output voltage (V) Output current minimum (A)
Actuator 2.5-5 5 1.12
Avionics 2.5-5 5 2.12
Avionics 2.5-5 12 0.67

Single Supply Design

The final supply design, specified in the table below, has a very high overhead. This is designed to support the sponsor's demand for the ability to include more PC/104 interface boards (ADC, DAC, etc.) which demand much more current than more power-frugal digital-only circuits (such as the Lynx computer).
Power supply specifications
Targets Input voltage (V) Output voltage (V) Required current (A) Maximum current (A) Overhead (%)
5V Actuator 2.5-5 5 1.12 4.0 72
5V Avionics 2.5-5 5 2.12 7.0 70
12V Avionics 2.5-5 12 0.67 3.0 77

The schematic shown below is the final design for the triple-supply. It includes all necessary connectors to support a full, production-quality board. The three supplies are symmetric to allow minimum time-to-build for the board design. Each of the supplies used a Linear Technologies LTC1871 and a common set of power electronics and passive devices.

Final power supply schematic

Final power supply schematic

Layout and Fabrication

The layout was performed in the Cadsoft Eagle editor and the design files are available to anyone with guest access to this project. An image of the layout is given below.
Final power supply layout

Final power supply layout

The first board was constructed in the RIT CEMA Lab with the assistance of Mr. Jeff Lonneville. The populated board is shown below.

Partial fabrication of the first supply board

Partial fabrication of the first supply board

The board is missing the regulator chips, as the order hasn't come in as of the time of this writing.

Errata

There are a few issues encountered with the first design, these are: