The hottest intelligent battery system based on ps

  • Detail

PS50 can be divided into two intelligent battery systems based on its functions, digital display and microcomputer control. 1 Introduction

ps501 is an intelligent battery management chip launched by American microchip technology company. It is suitable for 2-4 lithium ion and lithium polymer battery packs, or 6-12 nickel hydrogen and nickel cadmium battery packs. It can accurately calculate the remaining capacity and full charge capacity of the battery pack, As well as predict the running time of the battery and the time required to complete charging, provide battery monitoring function to ensure safe use, and advanced battery balancing function can prolong the battery life and working time. Its communication protocol conforms to SMBus 1.1 and sbdata 1.1 smart battery instruction set

features and pin description

● features

· support 2 ~ 4 lithium batteries and 6 ~ 12 nickel batteries

· field programmable lithium ion/lithium polymer/nickel battery power metering chip based on Pic18F MCU core

· follow SMBus 1.1 and sbdata 1.1

· precision 16 bit Δ-Σ A/d conversion, current measurement accuracy is less than 1mA

· 18V maximum input voltage, and the voltage measuring end can be directly connected with the battery cell

· programmable i/o is used for LED drive, charge and discharge protection and secondary safety protection

· for different battery cells, users can configure different battery models

· the measurement error of battery capacity is less than 1%

· advanced end of discharge (EOD) judgment method

· 16kb flash memory and 256byte EEPROM

· high precision internal oscillator

· extremely low power consumption, with power consumption of 200 during operation μ A. 100 in sampling mode μ A. Only 0.5 during sleep μ A。

· enhanced ESD protection capability

· 12 general programmable i/o ports, of which 2 are high voltage (up to 18V) open drain outputs

· integrated and external temperature sensors to realize the temperature detection function of two positions

· built in battery balance circuit with maximum balance current of 8.4ma and external battery balance control function

● pin description

ps501 adopts tssop28 lead-free package, which meets the Rosh of the European Union and the environmental protection requirements of various countries. Its pin arrangement is shown in Figure 1. Ultra small tssop package (7.85mm × 10.2mm) can save PCB space and be conveniently installed in battery packs of different sizes, as shown in Figure 2

Figure 1 ps501 pin diagram Figure 2 intelligent battery pack based on ps501

ps501 pin function introduction

ps501 internal structure and working principle

● ps501 internal structure

see Figure 3 for the internal structure of ps501

Figure 3 ps501 internal structure diagram

● processor core/memory

ps501 adopts PIC18 8-bit RISC MCU core, and its memory resources include 16kb flash memory and 256byte EEPROM, which are used to store programs/data and parameters respectively. These two kinds of memories can be reprogrammed through the SMBus Interface without special programming interface. Each ps501 has burned the boot loader program before leaving the factory. For different types of electrical equipment, battery cells with different characteristics, and configuration information such as different capacities, users can use the powertool500 software to generate different firmware, and download the firmware at the production site of the battery pack, so that the manufacturer of the battery pack can easily and quickly change the firmware for battery cells with different characteristics and different upper computer devices, There is no need to change the hardware circuit

● a/d converter

ps501 uses high-precision a/d converter to accurately measure current, voltage and temperature. A/d can eliminate gain error and offset error after calibration. During the production process of battery pack management PCBA based on ps501 chip, in addition to downloading firmware on site, it also needs to calibrate the a/d conversion circuit and silicon clock oscillator. The calibration contents include: battery pack voltage sampling, voltage sampling of each string of battery cells, external and internal temperature sampling, current sampling, and silicon clock oscillator. Therefore, the cumulative errors caused by component accuracy and PCB design can be corrected to the greatest extent through calibration, so as to ensure that the sampling of physical quantities by each PCBA is accurate, and the whole process takes only 15s, and the whole process is carried out automatically without manual intervention

● powermart firmware/battery model

flash memory is solidified with battery management firmware developed by powermart. The firmware adopts proprietary algorithm and precise three-dimensional battery model, which contains more than 250 parameters and can compensate for self discharge, temperature and other factors. In addition, the ps501 also performs a number of capacity correction and error reduction operations during the charge/discharge cycle to improve accuracy, coulometer and charging control performance. The above functions can ensure accurate battery capacity reporting and real-time prediction with an error of less than 1%. The reprogrammability of flash memory makes it possible to quickly upgrade firmware and generate user versions without changing the silicon chip design. Ps501 can be easily customized according to the chemical properties of the battery for specific applications

powermart provides various standard configuration files, which can be used to configure various popular rechargeable batteries and battery pack applications. Figure 4 and table 1 are an example of the 3D model of discharge end voltage and ps501 internal table parameters at different temperatures and discharge rates

Figure 4 3D model of discharge end voltage at different temperatures and discharge rates

Table 1 lithium battery discharge end voltage lookup table

● SMBus Interface/sbdata command

ps501 includes an SMBus communication engine that conforms to the SMBus v1.1 protocol. At present, the communication between all notebook computers and notebook batteries follows this communication protocol. SMBus is a subset of I2C communication protocol. Using a processor with I2C communication interface or using software to simulate I2C communication interface, you can easily read the sbdata of ps501 and apply it to different electronic products

● accurate integrated time base

ps501 is equipped with a high-precision silicon oscillator, which can carry out accurate timing of self discharge timing and capacity calculation without external clock oscillator. This internal silicon oscillator can be calibrated by the user during the production of the battery pack

● temperature detection

when the ps501 is close to the monitored battery, the on-chip integrated temperature sensor can be used to reduce the number of devices, and the user can also choose to monitor the temperature through the pin external thermistor provided by the device. At the same time, ps501 can support internal and external sensors to sample respectively, monitor the temperature of two different places, and make temperature protection under different conditions through GPIO

● general i/o

ps501 provides 12 programmable digital input/output pins. Among them, 8 pins can be used as LED output to display the state of charge (SOC), or directly control the external charging circuit, or provide additional safety protection for lithium-ion battery pack. Of course, they can also be used as general-purpose input/output pins. Among these pins, two i/os are open drain output pins, so they can be used to directly drive FET or other high voltage applications

when the maximum 8.4ma balance current provided inside the ps501 is not enough to meet the balance function needs of high-capacity battery pack, the ps501 can control the external balance circuit through general i/o to realize the balance current control of user-defined size. In addition, general i/o can also be used to drive the buzzer for low battery sound prompt when the battery is working at low capacity

working mode

ps501 has four working modes: operation mode, sampling mode, low voltage sleep mode and idle sleep mode. Each mode has specific entry and exit conditions, and the power consumption of the four modes is different

● operation mode: ps501 works in this mode when the battery pack is charging or discharging

operation mode is the working mode with the largest power consumption. In the operation mode, all measurements and calculations are carried out once in a measurement cycle. In each measurement cycle, the current, voltage and temperature are measured in turn. For example, when the laptop is working or charging, the working current of ps501 is 200 μ A。

● sampling mode: ps501 performs sampling mode when the battery pack is neither charged nor powered

in the sampling mode, the calculation of charge state, SMBus request and other operations will still be carried out according to the frequency of the normal operation mode, except that the measurement is carried out every multiple sampling periods. The total power consumption of the device is significantly reduced. For example, when the laptop is turned off, the working current of ps501 is 100 μ A。

● low voltage sleep mode: when the measured voltage of the battery pack is lower than the preset value of the user, the device enters the sleep mode

ps501 in sleep mode will no longer be measured and calculated. The electricity meter display does not work, and the communication on the SMBus is ignored. The device can exit the sleep mode only when the wake-up conditions are met. Sleep mode is one of the lowest power consumption modes. It is used to save battery energy after the battery is completely discharged. At this time, the working current of ps501 can be as low as 1 μ A。

● idle sleep mode: for battery packs that need long-term storage, idle sleep mode can be adopted

in this mode, ps501 will enter low-power sleep mode regardless of the voltage value. The SMBus command enables the device to enter this mode. At this time, the typical power consumption of ps501 can be as low as 1 μ A。 When SMBus bus has pull-up level, exit this mode. This mode is used to save power in the process of long-term storage and transportation of battery packs. For example, the ps501 can be set to work in this mode from the production of laptop battery to the first use of the user

battery balance

● necessity of battery balance function

when the capacity of battery cells in a series battery pack is different from that of other series battery chips, it will be reflected in the different voltage between the series battery cells when the battery pack is full or discharged. In this case, during the charging process of the battery pack, the battery cell with too high voltage triggers the overcharge protection of the battery pack in advance, while during the discharge process, the battery cell with too low voltage causes the overcharge protection of the battery pack, which significantly reduces the overall capacity of the battery pack. The capacity reflected by the whole battery pack is the capacity of the battery cell with the worst performance in the battery pack

● internal balance function of ps501

ps501 has battery balance load, which is used to draw excess current from the battery with higher voltage, consume excess power, and realize battery balance. According to the different battery voltage, the internal multiple 500 Ω resistors will draw a maximum of 8.4ma current from each battery. The battery balance algorithm will monitor the voltage of a single battery and the voltage difference between them. For the battery pack with small capacity and good performance and consistency of battery cells, you can choose to use the internal balance function

● external balance control function of ps501

when the capacity of the battery pack is large and the performance and consistency of the battery cell are poor, the balance circuit in ps501 chip cannot effectively balance the battery. In this case, the programmable i/o of ps501 can be used to realize the battery balance function of high current through simple components outside the chip. Refer to figure 5 for application battery. In this way, by changing the resistance value of shunt resistance, different balance currents can be easily realized, which is usually set to more than 100mA in some applications. This function is especially suitable for electric vehicles, electric tools, external battery packs and other applications using domestic high-capacity battery cells

Figure 5 ps501 external battery balance circuit

ps501 typical application circuit

ps501 typical application circuit see

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