The proportion of cars and fleets using vehicle tracking systems is rising. The modern tracker has been reduced in size and features have been enhanced to support active data transfer for real-time tracking. In addition, backup capabilities and lower voltages are required to power the system GPRS chipset.
background knowledgeThe vehicle tracking system is ideal for monitoring a single car or an entire fleet. The tracking system consists of automatic tracking hardware and data acquisition software (and data transfer if needed). The global fleet management market is $8 billion in 2015 and is expected to exceed $22 billion by 2022, with a compound annual growth rate of more than 20% from 2016 to 2023 (source: Global Market Insights). The growing demand for commercial vehicles in 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 slows the process. In addition, the size of the vehicle tracking market in the Asia-Pacific region is expected to increase significantly during the forecast period, with Japan, India and China being the main drivers. These emerging markets have huge potential, mainly because they have a large number of commercial vehicles.
Active and passive trackersActive and passive trackers collect data in the same way and are equally accurate. The main difference between the two types is related to time. Active trackers are also known as real-time trackers because they transmit data over satellite or cellular networks and instantly indicate where the vehicle is located. This way, the computer screen can display its motion in real time. This makes proactive tracking the best choice for companies interested in improving delivery efficiency and monitoring employee driving. The active tracker also has a geofencing feature (which 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 to retrieve stolen vehicles. Of course, active GPS tracking devices are more expensive than passive and require a monthly service fee.
Passive trackers, on the other hand, are less expensive, smaller, and easier to hide. The downside is that data storage is limited. Information is stored on the device instead of transferring the data to a remote location. To view any of these information, the tracker must be removed from the vehicle and inserted into the computer. Such systems are suitable for those who record miles for work purposes or for businesses that intend to reduce vehicle abuse. In addition, they are often chosen to monitor human behavior (think of detective work). Passive trackers are a good choice if you don't need immediate feedback and have a plan to check device data regularly.
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. Since higher automotive system voltages and currents are required to charge the battery (usually a single-cell Li-Ion battery), the switch mode charger is more efficient to charge than the linear battery charging IC, and the heat generated by the power loss Less, so it is a better choice. In general, embedded automotive applications have input voltages of up to 30 V, and some even higher. In these GPS tracking systems, the ideal charger is a 12 V to single-cell Li-Ion battery (typically 3.7 V) with additional protection against higher input voltages (when the battery is out of control for voltage transients), and Some sort of backup capability.
Battery charging IC design problemTraditional 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-chemical charging, high charging efficiency (very low heat generation, fast charging), and wide operating voltage range. Of course, the drawbacks always exist. Some of the disadvantages of switching chargers include: relatively high cost, more complex inductor-based designs, possible noise generation, and larger solution sizes. Due to these advantages, modern lead-acid, wireless power, energy harvesting, solar charging, remote sensors, and embedded automotive applications primarily 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, making it a truly compact solution. Therefore, the early tracking system is not very compact in appearance. A typical application for tracking systems is the use of car batteries and single-cell Li-Ion batteries for storage and power backup.
So why does the tracking system require a more integrated power management solution? The main reason is that the size of the tracker itself needs to be reduced, and the market is as small as possible. In addition, it is necessary to safely charge the battery, protect the IC from voltage transients, back up the power system to prevent system power loss or failure, 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:
â— High efficiency synchronous buck topology
â— Wide input voltage range to accommodate a variety of input power sources with protection against high voltage transients
â— Appropriate battery charging voltage to support GPRS chipset
â— Simple autonomous operation with onboard charge termination (no microcontroller required)
â— PowerPath control, can seamlessly switch between input power and backup power when a power failure event occurs; if an input short circuit occurs, it also needs to provide reverse blocking
â— When the input does not exist or a fault occurs, the system load is supplied through the backup battery.
â— Due to space constraints, the size and thickness of the solution should be small
â— Advanced packaging to improve heat dissipation and space efficiency
To meet these specific needs, Analog Devices recently introduced the LTC4091, a complete backup lithium-ion battery management system that keeps the 3.45 V to 4.45 V rail active during long mains failures. The LTC4091 uses a 36 V monolithic buck converter with adaptive output control to power the system load and deliver high-efficiency battery charging through the buck output. When external power is available, the device delivers up to 2.5 A total output current and up to 1.5 A for a single 4.1 V or 4.2 V Li-Ion battery. If the main input supply fails and can no longer supply power to the load, the LTC4091 will supply up to 4 A from the standby Li-Ion battery for the system output load through the internal diode; if an external diode transistor is used, the LTC4091 can provide unlimited (relatively speaking) The current. To protect sensitive back-end loads, the maximum output load voltage is 4.45 V. During a power failure, the device's PowerPath control seamlessly switches between input and backup power 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 a built-in 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 standby Li-Ion battery applications: standard 4.2 V and optional 4.1 V, which increases the number of charge/discharge cycles by reducing battery run time . Other features include soft-start and frequency foldback to control output current during startup and overload, trickle charge, automatic recharge, low charge precharge, charge timing termination, thermal regulation, and thermistor for temperature-demand charging Pin.
The LTC4091 is available in a low profile (0.75 mm) 22-lead 3 mm & TImes; 6 mm DFN package with a metal pad on the substrate for excellent thermal performance. The device operates over the -40°C to +125°C temperature range. Figure 1 shows a typical application schematic.
Figure 1. Typical application schematic of the LTC4091.
Thermal regulation protectionTo protect the IC or surrounding devices from thermal damage, the internal thermal feedback loop automatically reduces the programmed charging current when the die temperature rises to approximately 105 °C. Thermal regulation protects the LTC4091 from over-temperature effects caused by high-power operation or high ambient temperature conditions and allows the user to increase the power handling capability limits 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 the worst-case setting, and the battery charger will automatically reduce the current in the worst case.
Car cold start running process
In automotive applications, the supply voltage drops significantly. For example, during a cold start, this can cause the high-voltage switching regulator to lose its regulation capability, causing the VC voltage to be too high, which in turn causes the output overshoot to be very large when VIN is restored. To prevent overshoot from recovering from a cold start event, 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 a power-down condition and resets the RUN/SS pin, re-enabling the soft-start feature to prevent output overshoot from causing damage.
Figure 2. Cold start crossing circuit.
in conclusionThe proportion of cars and fleets using vehicle tracking systems is rising. The modern tracker has been reduced in size and features have been enhanced to support active data transfer for real-time tracking. In addition, backup capabilities and lower voltages are required to power the system GPRS chipset. ADI's LTC4091 is a high voltage, high current step-down battery charger and PowerPath backup power manager with thermal regulation and other comprehensive protection features to provide a single-chip, compact, powerful and flexible solution for vehicle tracking applications. To make the designer's task easier and easier.
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