An Introduction to A number of Generally used AFEs and their Schemes

Courtesy: Infineon

This text will introduce you to the event of recent vitality automobiles and vitality storage business, a number of methods of cell assortment options, and give attention to Infineon’s new AFE acquisition chip TLE9018DQK in addition to its use and technical traits.

When it comes to passenger automobiles, lately, with the emergence of a brand new spherical of scientific and technological revolution and industrial transformation, the brand new vitality car business has entered a stage of accelerated growth. China’s new vitality car business, after years of steady efforts, the technical degree has been considerably improved, the economic system has been improved, and the competitiveness of enterprises has been enormously enhanced, exhibiting a great scenario of “double enchancment” of market scale and growth high quality.

When it comes to vitality storage, electrochemical vitality storage, because the quickest rising vitality storage technique lately, has quickly elevated from 3.7% in 2018 to 7.5% in 2020. Lithium-ion battery vitality storage has excessive vitality density, large industrial utility, declining unit price, and mature know-how, so lithium-ion battery vitality storage has grow to be the hegemon of world electrochemical vitality storage. In keeping with the info, by the top of 2020, lithium-ion batteries accounted for 92% of the put in capability of electrochemical vitality storage, and sodium-sulfur batteries and lead-acid batteries accounted for 3.6% and three.5%, respectively. At current, lithium-ion vitality storage primarily makes use of lithium iron phosphate battery know-how.

2. Introduction to the gathering plan

(1) Cell assortment realized by AD chip

Whether or not it’s new vitality passenger automobiles or vitality storage, new necessities and requirements have been put ahead for the BMS business. A key know-how in BMS know-how is the gathering and safety of cell parameters, the so-called AFE know-how. Within the early days, there have been no AFE chips, and the gathering of battery cells was principally collected one after the other with AD chips. The digital change is used to realize the aim of sequential switching. The scheme is roughly as follows:

As proven within the determine above, its precept is to make use of 2 digital switches, on the similar time, the higher change strobe a method, and the decrease change strobe a method, (the digital change adopts TI’s MUX5081DR, and which one gated is configured by 3 addresses). Throughout the switching course of, be certain that the strobe of the higher change and the decrease change are adjoining to one another, and the strobe of the higher change is the excessive place. The gated two-way knowledge is collected differentially by ADI’s ADS1113IDGSR and transformed into an I2C sign for MCU communication.

The acquisition charge and accuracy of this assortment technique are usually not very excessive, and the overall acquisition accuracy should attain 14 bits to satisfy the necessities of cell assortment. This assortment technique is presently used within the assortment of some particular cells, resembling nickel-chromium, nickel-metal hydride, and lead-acid batteries. As a result of many of the cells on this focus seem in teams. Most of us use this group as a cell to take care of, and the voltage of this group will usually be better than 5V, such because the 12V of the lead-acid group that we’re acquainted with. That is the place this strategy is required to realize partial stress harvesting.

(2) Cell safety achieved by a single-cell cell safety chip

There’s additionally a easy single-cell assortment scheme available on the market, which options that every cell is independently protected by a single chip. As proven within the determine under:

The chip HY2112-BB can understand the safety of over-voltage and over-under-voltage, charging detection and charge-discharge management. The operation mode is especially realized by driving the exterior MOS with the drive pin of the output.

(3) Cell safety realized by multi-cell cell safety chips

There are primarily 4 strings, 7 strings, 8 strings, 12 strings, 14 strings, and 16 strings of multi-cell acquisition chips available on the market. Amongst them, 12 strings and 14 strings are the bulk. Typical examples are ADI’s LTC6803HG and NXP’s MC33771A.

As proven within the determine under:
Determine 3 exhibits BYD’s 4-string BM3451 acquisition chip scheme. Determine 4 exhibits ADI’s 12-string LTC6803HG acquisition scheme, and Determine 5 exhibits NXP’s 14-string MC33771 acquisition scheme.

Along with cell voltage acquisition, noise filtering, self-function monitoring, and built-in inner equalization MOS, these two kinds of acquisition even have multi-channel temperature acquisition, and MC33771 additionally comes with inner present measurement, simplifying the BMS present acquisition loop.

3. Infineon’s new TLE9018DQK AFE acquisition answer

Infineon’s AFE acquisition answer is especially TLE9012 within the early stage, and in contrast with different chips, crucial characteristic of this chip is the built-in stress and temperature compensation perform. This perform permits the chip to take care of good acquisition accuracy in particular environments. The primary drawback is that the variety of strings is comparatively small, and there are limitations within the mixture of strings and mixtures. The TLE9018DQK is developed on the idea of TLE9012, and its purposeful traits are primarily as follows:

1. It could monitor 18 strings of batteries on the similar time.
2. The utmost voltage can attain 120V, with sturdy ESD perform. It could help frontal scorching swapping with out exterior safety (as a consequence of its excessive stand up to voltage worth and inner safety).
3. Built-in stress sensor and temperature compensation with digital compensation algorithm. Its merchandise can keep excessive acquisition accuracy in a wide range of complicated environments.
4. Built-in 8 temperature acquisition channels.
5. The utmost passive equalization circuit can attain 300mA.
6. Assist capacitive coupling and transformer coupling in communication.
7. It has a number of wake-up sources, so it might probably get up the chip in a wide range of methods.
8. With automated no-load detection perform.

The peripheral pinout diagram appears to be like like this:

TLE9018DQK is appropriate for HEV, PHEV, BEV, vitality storage and different product functions. The bundle kind is: PG-FQLP-64. The utmost permissible temperature vary is –40-150°C. The comparability of TLE9018 with different chip technical parameters might be referred to the next determine:

Right here, for TLE9018DQK, a set of cell assortment schemes is made, as proven within the determine under.

As a result of the TLE9018DQK has its personal passive balancing MOS, the exterior balancing circuit solely must be linked to the current-limiting resistor, and contemplating the resistor energy drawback underneath the utmost balancing present, two 82R, bundle 2512 energy resistors are linked in parallel to enhance reliability. The 8-channel temperature measurement is delivered to the MCU with a 3.3K current-limiting resistor. Exterior 100K NTC temperature sensor for temperature assortment. If the temperature sensor shouldn’t be used a lot, the unused pins should be pulled all the way down to the bottom finish.
IFL_L, IFL_H, IFH_L, IFH_H, and 4 pins are externally linked to Infineon’s remoted communication chip TLE9015, which may understand multi-level collection daisy-chain communication.

The ERR pin is linked on to the MCU and may feed again the present state of the chip to the MCU.

The chip comes with 4 GPIO pins, which may management exterior indicators, alarms, and so forth., which aren’t used right here in the intervening time, so they’re immediately pulled all the way down to floor.