With the rapid development of smart wireless devices and electric vehicles,
The market demand for lithium batteries is getting wider and wider.
Production efficiency is also getting higher and higher,
Due to the need for energy saving and emission reduction,
Lithium battery formation is also taking a large number of forms of energy feedback.
Realize energy saving and environmental protection.
Want to know how to perform a more accurate component test?
TI FAE takes you to an in-depth analysis!
In order to obtain the capacity of the lithium battery more accurately, the error requirement for the current and voltage measurement of the charge and discharge of the lithium battery is also significantly improved, and many customers need to achieve an error precision of 5 to 1 in 10,000, so that the entire measurement control The error requirements of the amplifier, ADC, and DAC in the circuit are also increased accordingly.
In general, a complete energy feedback type lithium battery component test equipment is divided into three levels of structure. As shown below:
The first stage is a bidirectional converter with 220, 380V AC to 400-500V DC , the second stage is a bidirectional converter of 400V DC to 12V DC, and the third stage is a bidirectional converter of 12V DC to 5V DC. Discharge. The specific power depends on the size of the battery charge and discharge and the number of batteries. With TI's C2000 TMS320F280XX, it is easy to implement the functions of the first and second levels, and the first and second levels can be combined to directly implement the 220V AC to 12V DC mode, further reducing Chen Ben.
For the third-pole 12V DC to 5VDC bidirectional converter, usually use the analog loop control scheme, continue to look down, we will introduce you to a C2000 digital solution introduction.
The above figure is TI's analog loop control scheme reference design , which is also a cost-effective discrete device solution adopted by most customers. The TL594 implements PWM control, the LM5106 is driven by a half-bridge MOSFET , and the LM5060 is a battery anti-reverse control . High precision current voltage acquisition and loop regulation, mainly implemented by INA225 and OPA180 . The INA225 is TI's dedicated current-sense amplifier that integrates an external gain resistor to provide a fixed gain output that provides excellent temperature drift while simplifying the circuit. Moreover, the INA225 automates bidirectional current sensing without additional control signals. It is very convenient to use.
OPA180 is self-stabilizing, low temperature floating operation, doing PID regulation and CV, CC control. External ADC The ADS1248 is a 24-bit DS ADC that collects the charge and discharge voltage and current and does not participate in loop control. An ADS1248 can simultaneously measure the current and voltage of the 4-channel battery charge and discharge. If the external switch is switched, more can be measured to achieve better cost performance.
The DAC80004 is a 16-bit DAC that is used to set the charge and discharge voltage and current. The zero point error is less than 2mV, which enables a lower charge current threshold setting.
The key to this reference design is the control of the temperature drift. The amplifier with low temperature drift characteristics is especially important. TI's INA225 and INA240 are very good low-temperature drift current detection amplifiers , and the temperature error of the gain error is less than 2.5ppm. Moreover, the temperature drift of the sampling resistor also directly determines the temperature drift performance of the system. The sampling resistance of 20ppm is already very good. When sampling current, the resistance is a power heat source, which will significantly cause the temperature rise of the surrounding PCB and worsen the temperature. The impact, therefore, the PCB layout of the sampling resistor is very important .
If you would like to know more about the PMP40182 reference design and test data, please click to read the original text for more information!
With the popularity of TI's C2000 DSP, more and more engineers are also trying to use C2000 to achieve 12V to 5V, 10A bi-directional battery charge and discharge control , thus achieving the entire link, from 220V AC to 5V DC full digital bidirectional conversion .
The following is a schematic diagram of the C2000's 12V to 5VDC bidirectional DC-DC. Using TI's latest TMS320F2837X, CC, CV loop control is implemented by C2000 software, F2837X's high-precision PWM (HRPWM) can achieve high-precision (>16-bit) DAC+PWM function, no external DAC required; F2837X also internal Integrated multi-channel 16-bit ADCs also require no external ADC and require only external current sensing and amplification. With the F2837X design, the circuit design can be greatly simplified, providing higher reliability and temperature drift characteristics. A single F2837X may be more expensive, but one F2837X can support the charging and discharging of multiple batteries, so the average cost per channel is very low.
In general, TI can provide an end-to-end complete solution for modern battery-integrated test equipment, helping customers solve related technical problems in the development process and bring the product to market as quickly as possible.
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