How to simplify lithium ion energy storage equipment in energy acquisition design

　　Author ：Iflowpower – Portable Power Station Supplier

Lithium-ion batteries provide effective treatment for oversupply to meet the peak power requirements in energy collection. However, keeping battery health carefully pays attention to voltage levels during charging and discharging operations. By using a suitable IC, including CyMbetCorPoration, Linertechnology, MaximIntegrated, SeikoinStruments, STMicroelectronics, and Texastruction, STMicroelectronics, and Texastruments, engineers can simplify the use of lithium-ion energy storage equipment in energy acquisition design.

The storage device is still a desired part of the energy collection, and the fluctuations of fluctuating energy are not subject to fluctuations. In a typical energy acquisition design (Fig. 1), the load circuit obtains additional power from the lithium ion storage device, including thin film batteries such as Cymbetnerchip series, FDKML series, PanasonicML and VL series, etc.

, charging button batteries and Seiko MS series. By storing excess energy during low power, the rechargeable device is prepared when the power requires a peak during a low environmental energy, periodically, periodic wireless transmission, and other power-intensive system states. Figure 1: Lithium ion film and rechargeable battery for wireless MCU supply continued to supply power, meet the needs of wireless MCU, such as SiliconLabsezradiopro wireless MCU series (supplied by SiliconLabs) These lithium-based storage devices depending on the narrow windows Strictly maintain the charging voltage (Figure 2).

Voltage outside the work range can cause battery deterioration. In fact, even if the charging voltage that is close to the safe operating range limit can result in the final loss of the battery capacity (Figure 3). Therefore, the charging management circuit is related to ensuring the best output and life of these storage devices.

Figure 2: Lithium ion battery to use a charging voltage within a narrower operating range (courtesy plus). Figure 3: Even if the charging voltage close to the limit of this range is also caused by the capacity of the capacity (the picture is supplied by Cymbet) even within the safe operating range of the lithium-ion battery. The charging management process method Li-Ion battery management circuit usually rely on constant pressure sources to maintain the best charging voltage, and load the circuit to prevent the over-discharge of the lithium-ion battery.

Although lithium ion batteries can use constant current and constant voltage charging, lithium-ion battery manufacturers typically propose to charge constant pressure charging. Therefore, suitable charging circuitry can simply include linear regulators and diodes, reverse discharge in alert (Fig. 4).

Circuit designers have many options to achieve load break function. Designers can compare battery outputs with low-power voltage reference sources, such as Texas Instruments LM4051 and MaximintegratedMAX6037, which supplies output voltages within lithium ion operating ranges. When the battery voltage is lower than the reference voltage, the circuit can use the FET switch (such as DioDesIndSincortedzxMN2F30FH or FAIRCHILDSEMICONDUCTS8434) to disconnect the battery.

Similarly, engineers can control the load break opening switch using a power supply that is supplied with a number of regulator ICs and undervoltage locking (UVLO) signals. Figure 4: The simplest charging circuit lithium-ion battery is a linear regulator for maintaining an appropriate charging voltage, the diode has a very low reverse bias leak, with a counter battery by power supply (picture by Cymbet). Lithium ion charging management IC integrates key charging and protection circuitry required for lithium-ion batteries, and supplies extensive functions required to optimize battery output and life.

For example, Lingllet's LTC4071 only needs an external resistance to supply complete lithium-ion battery management (Figure 5). When the input power is removed and the battery voltage is lower than the high battery output threshold, the battery consumption of the LTC 4071 is only 550 nA, thereby reducing the power consumption requirements in power restricted energy collection usage. Figure 5: Lithium Ion Battery Management IC, such as Lineral LTC4071, integrated charging and protection circuitry, only a minimum of extra components can be supplied to the complete lithium-ion battery management method (supplied by Linertechnology).

In the LTC4071, if the external lithium ion battery voltage is lower than the low battery disconnect (VLBD) voltage level set by the engineer, the internal PFET (MP1) is disconnected from the VCC to protect the battery from load over-discharge to VCC. Or even the static current connected to the LTC4071 itself. In the disconnect mode, even in the high end of the operating temperature range, the battery leakage current is also below 0.

1na. In order to protect the external lithium ion battery from overcharge, the LTC 4071 reduces the charging current by shunting up to 50 mA to reduce the charging current when the battery voltage is close to the floating voltage, away from the battery. Although it supplies three programmable floating voltages (4.

0, 4.1 or 4.2V) using integrated three-level decoders, the LTC 4071 uses NTC thermistors to test high temperatures and automatically reduce battery floating voltage.

A wide range of functions, such as MaximIntegratedMAX 1737 and SeikoinStrumentSS-8261 for controlling the output of the external FET device gate, served as a charging current source or cutoff switch. Components related to MAX1737, MaximIntegrated are designed with external dual N-channel MOSFETs as switch and synchronous regulators, supply charging current or voltage. SEIKOS-8261 uses separate external FETs to overcharge and over-discharge protection.

Here, when the external lithium ion battery voltage exceeds the predetermined overcharge test voltage level, the device closed the charging control FET to stop charging. Similarly, when the battery voltage is lower than the specified over-discharge test voltage, the device closed discharge control FET. S-8261 uses test delay on time for each case, triggered by alert.

In addition to the above equipment, engineers can also find lithium-ion charging management devices with extensive functions and meet various functions and performance. Require. For example, CymbetcBC3105 combines thin film energy storage and on-chip power management functions in a single integrated device.

MaximIntegratedMax8601 and other devices such as STMicroelectronicSL6924 and L6924D have advanced power management features to support USB port charging, but can still be used as a valid processing method for collecting use of power restrictions. These dedicated lithium-ion charge management devices are used for energy collection, engineers can use specialized energy acquisition ICs, which also support lithium ion charge management and protection. Highly integrated ICs, such as Texas Instruments BQ25504 and MaximintegratedMAX17710, extending its integrated energy collection function through the full set of functions required for lithium ion charge management.

TIBQ25504 integrates an efficient DC / DC boost converter with special energy collection functions, such as maximum power point tracking (MPPT), optimizes the power output of environmental energy. In addition, the device also supports battery charging and protection, has a programmable threshold for undervoltage and overvoltage protection (Fig. 6).

Figure 6: TIBQ25504 has three programmable threshold voltage output, which can be used to emit undervoltage, overvoltage, and good voltage signals - showing the voltage threshold settings used in typical solar energy (Texas Instruments). The MaximIntegratedMAX17710 is designed for various environmental energy and integrates independent features, which can be charged for external batteries through overcharge protection, and adjust the battery output by over-discharge protection. Confused, the device uses internal linear regulators to maintain the charging voltage at 4.

125V. If the charging power supply exceeds 4.15V, the device begins to limit the current.

If the charging power supply exceeds 5.3V, the device can be divided into 50mA ground, with alert overvoltage operation. For the output, the MAX17710 uses internal low pressure difference (LDO) regulators to adjust the battery output voltage.

If the unit is over-discharge, the UVLO circuit disables the LDO regulator when the LDO regulator is working, or if it has been disabled, the LDO regulator will start. The MAX17710 handles environmental energy levels when the environmental source and lithium ions can cause system voltage crash. Storage can supply sufficient power to maintain support for load.

In this case, the energy collection circuit can enter the power system to keep trying to support the load but crash - only repeat the attempt and repeatedly failed. When using the MAX17710, if it is powered off in this way, the device disables the load output to restart attempts with a non-use load, and protect the unit from excessive discharge. The device remains disabled until it is tested to the system that has been connected to the specified voltage level.

Conclusion The rechargeable lithium-ion battery can supply power for peak load, and the level of energy output is lower than this value. However, in order to maximize battery life and output, engineers should ensure that the battery voltage level remains within a narrow limit. Designers can easily integrate lithium-ion battery management capabilities using dedicated charging management ICs, or reliance on battery charging and protection functions integrated in dedicated energy collection devices.