System hardware design

This article via:System hardware design.
Master Control Unit design and implementation: Master Control Unit is microcontroller PIC16F873 and keyboard controller chip ZLG7289A composition. The main task is responsible for communicating with the different costs today, and the processing of user input and LCD display information. The keyboard controller chip in here for six buttons and 12 LED control. ZLG7289A with a microcontroller through the SPI bus between the two-way communication. Main control unit charge per check every time unit, to obtain information about the current charging unit, as there is no battery, battery properties, the battery voltage. Followed by the LCD module to the user.
Design and Implementation of Charging Unit, LTC4002 Li-Ion Battery Charge Controller: LTC4002 is a high efficiency switching independent lithium-ion battery controller. The manager has two versions of 4.2V and 8.4V. LTC4002-8, 4 has a 500kHz switching frequency, is a high efficiency current mode PWM controller. This is an external P-channel MOSFET drives, it can provide 4A of current costs, while the efficiency can be as high as 90%. Output voltage is set at 8.4V, the final drive voltage with 1% accuracy, while the 5% charge accuracy. Furthermore, the handset can be 9V ~ 22V wide variety of wall adapter to run. In comparison with the hysteretic topology chargers, LTC4002-8, 4 of the fast operating frequency and current mode architecture to enable the use of small capacitors and inductor / capacitor combinations.
Lithium-ion / Ni-Cd battery loading unit of the overall design of the dual use: LTC4002 the face of an analysis of the past can see, the chip is for the lithium-ion battery controller, the nickel-cadmium batteries need to address the following issues: First, LTC4002 to monitor the battery voltage to ensure that the battery voltage does not exceed 8.4V. But for nickel-cadmium battery pack, charging cut-off voltages up to 9.2V. Secondly, the nickel-cadmium batteries come to an end, the need for batteries in the normal current 30% and 10% of the droplet charge. Thus, the second problem to be solved is how the size of the constant current charge current control. Moreover, nickel-cadmium batteries to charge pulse mode. Namely, 1s cycle, 95% of the time to 1% of the time charged the remaining time for the output is not paid leave. Finally, the court that a lithium-ion battery battery or nickel-cadmium batteries, lithium-ion batteries because if the miscarriage of justice for the nickel-cadmium batteries, will charge voltage higher than 8.4V, this lithium-ion batteries is very dangerous, but will nickel-cadmium batteries for lithium-ion battery miscarriage of justice, it may lead to insufficient battery loading. Therefore, we must ensure that a very low false positive rate.
The LTC4002 works partially based on the design of both the lithium-ion battery constant current - constant voltage load, they can nickel-cadmium battery pulse charging system. Charging the unit’s overall functional block diagram shown in Figure 2. Among them, signal-conditioning circuitry to both charger for 8.4V lithium battery load, but also may be 9.2V Ni-Cd battery load, but also play a role in controlling the size of the load current. LTC4002 use of micro-manager control work state, with the redundancy circuit that nickel-cadmium battery charger can be off loaded from pols run. Micro-controller through a certain communication protocols (HDQ16) and intelligent battery communication, to determine their capacity, the chemical nature of the key parameters.
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