Comprehensive introduction of vehicle tracking system

The proportion of vehicles and fleets using vehicle tracking systems is increasing. The modern tracker has been reduced in size and features have been enhanced to support the active transmission of data for real-time tracking. In addition, backup capacity and lower voltage are needed to power the system GPRS chipset.

The vehicle tracking system is ideal for monitoring single vehicles or entire fleets. The tracking system consists of automatic tracking hardware and data acquisition software (and data transfer if needed). The global fleet management market in 2015 is US$8 billion, and is expected to exceed US$22 billion by 2022, with an average CAGR of more than 20% from 2016 to 2023 (source: Global Market Insights). The growing demand for commercial vehicles in regions such as Latin America, the Middle East, and Africa is also a potential growth opportunity. In developed regions such as Europe and North America, the integration of Internet of Things (IoT) technology in vehicles is expected to increase the adoption rate of vehicle tracking systems, although the high cost of integration has slowed this process. In addition, the size of the vehicle tracking market in the Asia-Pacific region is expected to increase significantly during the forecast period. Japan, India, and China are the main driving countries. The potential for these emerging markets is huge, mainly because they have a large number of commercial vehicles.

Active and passive trackers collect the data in the same way and with the same accuracy. The main difference between these two types is related to time. Active trackers are also called real-time trackers because they transmit data over satellite or cellular networks and can instantly indicate where the vehicle is located. In this way, the computer screen can display its motion in real time. This makes active tracking the best choice for companies that are interested in improving delivery efficiency and monitoring employee driving. The active tracker also has a geofence function (this feature can be thought of as a mandatory field) that provides an alert when the vehicle enters or leaves a predetermined location. Such systems also help prevent theft and help recover stolen vehicles. Of course, active GPS tracking devices are more expensive than passive ones and require a monthly service fee.

On the other hand, passive trackers are cheaper, smaller, and easier to hide. The disadvantage is limited data storage. Information is stored on the device instead of transferring the data to a remote location. To view any of the information, the tracker must be removed from the vehicle and inserted into the computer. Such systems are suitable for people who record miles for work purposes or companies that are interested in reducing vehicle abuse. In addition, they are often chosen to monitor human behavior (think about detective work). If you don't need immediate feedback and there is a plan to regularly check your device data, passive trackers are a good choice.

Both types of trackers are inherently portable and have a relatively small form factor. Therefore, they require battery power and require backup capabilities to save data in the event of a power outage. Because higher automotive system voltages and currents are needed to charge the battery (usually a single-cell Li-Ion battery), compared to linear battery-charged ICs, switch-mode chargers charge more efficiently, and power losses generate heat. Less is therefore a better choice. In general, embedded automotive applications have input voltages up to 30 V, and some are even higher. In these GPS tracking systems, the ideal charger is a 12 V to 1-cell Li-Ion battery (typically 3.7 V) with additional protection to withstand higher input voltages (voltage transients when the battery runs out of control), and Some kind of backup capability.

Traditional linear topology battery chargers are often valued for their compact size, simplicity, and low cost. However, the conventional linear charger has the following disadvantages: the input and battery voltage range is limited, the relative current consumption is high, the power consumption (heat generation) is too large, the charge termination algorithm is limited, and the relative efficiency is low. Switch-mode battery chargers, on the other hand, are popular for their topological structure, flexibility, multi-chemistry charging, high charging efficiency (low heat generation, fast charge support), and wide operating voltage range. Of course, the drawbacks are always there. Some of the disadvantages of switching chargers include: relatively high cost, more complex inductor-based design, noise generation, and larger solution size. Due to the above advantages, modern lead-acid, wireless power, energy harvesting, solar charging, remote sensors, and embedded automotive applications mainly use switch-mode chargers.

Traditionally, the tracker's backup power management system consists of multiple ICs, high-voltage buck regulators, battery chargers, and discrete components and is not a truly compact solution. Therefore, the early tracking system is not very compact in appearance. A typical application of tracking systems is the use of car batteries and single-cell lithium-ion batteries for storage and power backup.

So, why do tracking systems require more integrated power management solutions? The main reason is that the size of the tracker itself needs to be reduced. The smaller the market is, the better. In addition, it is necessary to safely charge the battery, protect the IC from voltage transients, perform backup of the power supply system to prevent the system power supply from disappearing or failing, and provide a relatively low power supply for the General Packet Radio Service (GPRS) chipset. Voltage (about 4.45 V). Backup Power Manager

To achieve these goals, the integrated standby power manager and charger solution requires the following features:

● High efficiency synchronous buck topology

● Wide input voltage range to suit various input power supplies, with protection against high voltage transients

● Appropriate battery charging voltage to support GPRS chipset

● Simple autonomous operation with onboard charge termination (no microcontroller required)

● PowerPath control allows seamless switching between input and standby power supply in the event of a power failure; it also requires reverse blocking in the event of an input short circuit.

● Power supply to system load through backup battery when input does not exist or fails

● Due to space limitations, the size and thickness of the solution should be small

● Advanced packaging to improve thermal performance and space efficiency

To meet these specific needs, Analog Devices recently introduced the LTC4091, a complete spare Li-Ion battery management system that keeps the rails from 3.45 V to 4.45 V active during long periods of main power failure. The LTC4091 uses a 36 V monolithic buck converter with adaptive output control to power the system load and achieve high efficiency battery charging through the buck output. When external power is available, the device can deliver up to 2.5 A of total output current and up to 1.5 A of charge current for a single 4.1 V or 4.2 V Li-Ion battery. If the main input power fails and the load can no longer be powered, the LTC4091 will supply up to 4 A from the backup Li-Ion battery to the system output load through an internal diode; the LTC4091 can provide unlimited power if an external diode transistor is used (relatively ) The current. To protect sensitive back-end loads, the maximum output load voltage is 4.45 V. During power failures, the device's PowerPath control seamlessly switches between input and standby power supplies and reverses blocking when the input is shorted. Typical applications for the LTC4091 include fleet and asset tracking, automotive GPS data loggers and telematics systems, security systems, communications and industrial backup systems.

The LTC4091 has an internal 60 V absolute maximum input overvoltage protection that protects the IC from high input voltage transients. The LTC4091's battery charger provides two pin-selectable charging voltages optimized for stand-alone Li-Ion battery applications: standard 4.2 V voltage and optional 4.1 V voltage, which increases charge/discharge cycle times by reducing battery run time . Other features include soft-start and frequency foldback to control output current during start-up and overload, trickle charge, automatic recharge, low battery precharge, end of charge timer, thermal regulation, and thermistor for temperature-dependent charging Pin.

The LTC4091 is packaged in a thin (0.75 mm) 22-pin 3 mm & 6mm DFN package with a metal pad for excellent thermal performance. The device's operating temperature range is -40°C to +125°C. Figure 1 shows its typical application schematic.

Figure 1. Typical application schematic of the LTC4091.

To prevent thermal damage to the IC or peripheral devices, the internal thermal feedback loop automatically reduces the programmed charge current when the die temperature rises to approximately 105°C. Thermal regulation protects the LTC4091 from overtemperature effects caused by high-power operation or high ambient temperature conditions, and allows the user to increase the power handling capabilities of a given board design without damaging the LTC4091 or external components. The advantage of the thermal regulation loop is that the charging current can be set according to the actual situation, rather than setting according to the worst case, and the battery charger guarantees to automatically reduce the current in the worst case.

Car cold start operation process

In automotive applications, the supply voltage will drop significantly. For example, during a cold start, this can cause the high voltage switching regulator to lose its regulation capability, making the VC voltage too high, which in turn causes the output overshoot to be very large when VIN is restored. To prevent overshoot from a cold start event recovery, the soft start circuit of the LTC4091 must be reset via the RUN/SS pin. Figure 2 below shows a simple circuit example that automatically detects power-down conditions and resets the RUN/SS pin to re-enable the soft-start feature to prevent damage from output overshoot.

Figure 2. Cold boot through the circuit.

The proportion of vehicles and fleets using vehicle tracking systems is increasing. The modern tracker has been reduced in size and features have been enhanced to support the active transmission of data for real-time tracking. In addition, backup capacity and lower voltage are needed to power the system GPRS chipset. ADI's LTC4091 is a high voltage, high current buck battery charger and PowerPath standby power manager with thermal regulation and other comprehensive protection features, providing a single-chip, compact, powerful, and flexible solution for vehicle tracking applications , which makes the designer's task easier and easier.