In order to achieve energy-saving and environmental protection, lithium-ion battery changes, is the difference test method?

　　Author ：Iflowpower – Hordozható erőmű szállítója

With the rapid development of mobile phones, smart wireless devices and electric vehicles, the market demand of lithium batteries is getting wider and more, and the production efficiency of lithium batteries is getting higher and higher. At the same time, due to the need for energy saving and emission reduction, the lithium battery is chemically made, the charge, discharge, and a large number of energy feedback, the discharge energy of the lithium battery, feedback back to the power supply, and the other batteries to achieve energy saving and environmental protection. In order to more accurately obtain the capacity of the lithium battery, the error requirements of the current voltage measurement of the charge and discharge of the lithium battery are also significantly improved, and many customers need to reach 50% of the error accuracy, so that the entire measurement control is controlled.

The error requirements of the amplifier, ADC, and DAC in the circuit also improve. In general, a complete energy feedback type lithium battery is divided into 3-level structure. As shown below: The first level is 220, 380VAC to 400-500VDC two-way converter, the second level is a two-way converter of 400VDC to 12VDC, the third-level 12VDC to 5VDC two-way converter, charge and discharge the battery directly.

The specific power depends on the battery charge and discharge magnitude and the number of batteries. With TI's C2000TMS320F280XX, it is easy to implement the first and second levels of functionality, and the first level and second level can be merged, and the 220VAC to 12VDC can be achieved directly, further reduce Chen Ben. For the two-way converters of the third poles 12VDC to 5VDC, the simulation loop control scheme is usually adopted, and we will also introduce a C2000 digital program introduction.

The above figure is Ti's simulated loop control scheme reference design, and it is also a discrete device program that is currently cost-effective than most customers. TL594 implements PWM control, LM5106 is half-bridge MOSFET drive. LM5060 is battery anti-reverse control.

High-precision current voltage collection and loop adjustment, mainly INA225 and OPA180 implementation. INA225 is a dedicated current detector amplifier integrated with external gain resistors, providing fixed gain output, providing very good temperature floating characteristics while simplifying circuits; and INA225 is automatic implementation of two-way current detection without additional control signals It is very convenient to use. OPA180 is self-stable, low temperature floating, do PID adjustment and CV, CC control.

External ADCADS1248 is 24-bit D-SADC for collecting voltage currents of charge and discharge, not participating in loop control. A ADS1248 can measure the current voltage of 4-channel battery charges, if adding external switching, you can measure more, achieve better cost performance. The DAC80004 is 16-bit DAC to set the voltage current of the charge and discharge.

Its zero error is less than 2mV, which can achieve lower charging current threshold settings. The key to this reference design is a warm control. The magnitude of the low-temperature floating characteristics is especially important.

Ti's INA225, INA240 are very good low temperature drift detection special amplifiers, and the gain error is less than 2.5ppm. Moreover, the temperature of the sampling resistor also directly determines the temperature of the system, 20 ppm sampling resistance has been very good.

When sampling current, the resistance is a power heat source, which will significantly cause the temperature rise of the surrounding PCB, more deteriorates the temperature. The impact, so the PCB plate plate of sampling resistors is very important. TI's reference design - PMP40182's data and test data have been put on the Internet, there is a need to go to Ti's official website to download.

With the popularity of Ti's C2000DSP, more and more engineers have also tried to use C2000 to achieve two-way battery charge and discharge control of 12V to 5V, 10A, thereby achieving the entire link, from 220VAC to 5VDC full digital two-way conversion. A schematic diagram of the 12V to 5VDC bidirectional DC-DC of C2000. The latest TMS320F2837X, CC, CV loop control is implemented by Ti, which is implemented by C2000 software.

The high-precision PWM (HRPWM) of F2837X can achieve high-precision (> 16 bits) of DAC + PWM function, no external DAC; F2837X still Integrated multiple 16-bit ADCs, there is also no external ADC, only external current detection and magnification. With F2837X design, it can greatly simplify circuit design, providing higher reliability and temperature floating characteristics. A single F2837X may be high, but a F2837X can support the charge and discharge of multiple batteries, which is very low on each channel.

In general, TI can provide end-to-end full set of solutions for modern battery-based components to help customers solve the relevant technical issues in research and development, and push products to the market at the fastest speed.