How to change the component test to let lithium battery test energy saving?

With the rapid development of smart wireless devices and electric vehicles, the market demand for lithium batteries is becoming wider and wider, and the manufacturing efficiency is also getting higher and higher. Due to the need of energy saving and emission reduction, lithium battery formation is also taking a large form of energy feedback. Realize energy saving and environmental protection.

How to more accurately test the composition?

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, complete energy feedback type lithium battery component test equipment is divided into three levels of structure.

The first stage is a bidirectional converter of 220, 380 VAC to 400-500 VDC, the second stage is a bidirectional converter of 400 VDC to 12 VDC, and the third stage is a bidirectional converter of 12 VDC to 5 VDC, which directly charges and discharges the battery. The specific power depends on the size of the battery charge and discharge and the number of batteries. With TI's C2000TMS320F280XX, 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 220VAC to 12VDC mode, further reducing the cost.

For the third-pole 12VDC to 5VDC bidirectional converter, the analog loop control scheme is usually used. Let's 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. TL594 implements PWM control, LM5106 is driven by half-bridge MOSFET, and LM5060 is anti-reverse control of battery. 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 automatically implements 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. The external ADCADS1248 is a 24-bit D-SADC 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. Its zero error is less than 2mV, which enables a lower charge current threshold setting.

The key to this reference design is the temperature-controlled control. The amplifier with low-temperature 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 the current is sampled, the resistor 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.

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