Design of a new super capacitor module charging po

Design of a new super capacitor module charging power supply

Lishui University Students' innovative practice space, researchers from jiangsuguo Automatic Control Technology Co., Ltd. Wang Ye, Jiang Wandong, ye Jiahong, Ren Hongzheng, Chi Yuguo, wrote in the 5th issue of electrical technology in 2017, designed and implemented a new super capacitor module charging power supply and its control method

its functions: 1) aiming at the different requirements of various supercapacitor modules for charging voltage and charging current, the supercapacitor module is charged by the way of constant current first and then constant voltage, and 4. Protection function: the charging current and charging voltage can be adjusted; 2) The charging power supply and its control method can provide thermal protection for the super capacitor. During the charging process, the absolute temperature and temperature rise of the super capacitor module are monitored by the temperature sensor. If the absolute temperature or temperature rise of the super capacitor module is too high, the charging process will be automatically shut off

supercapacitors (ultracapacitors), different from traditional chemical power supply, is a kind of power supply with special performance between traditional capacitors and batteries, which mainly relies on double-layer and oxidation-reduction false capacitor charge to store electric energy. However, there is no chemical reaction in the process of energy storage, which is reversible, and it is precisely because this supercapacitor can be repeatedly charged and discharged hundreds of thousands of times [1]

according to the characteristics of positive and negative pulses and charging voltage fluctuation of battery, a fast charging method of positive and negative pulses with energy feedback is proposed in literature []. Reference [4] proposed a design method of capacitor module charging based on the interconnection of electric vehicles and energy. Literature [] points out that the preparation and performance optimization of supercapacitor monomers by chemical methods can improve the charging efficiency of capacitors. Reference [] introduces the capacity configuration, energy management and service life of super capacitor modules. The conclusions are of great significance to the design of charging power supply for capacitor modules

the energy storage principle of super capacitor is different from that of battery, and its capacity state during charging and discharging has its own characteristics. Supercapacitors are affected by charge and discharge current, temperature, charge and discharge cycle times and other factors, of which charge and discharge current is the most important factor. This design mainly analyzes the characteristics of supercapacitors under constant current charging conditions. The method of constant current and voltage limiting charging is to control the maximum voltage Umax, and turn to constant voltage floating charge after constant current charging until the super capacitor is full

the advantages of this charging method are: in the first stage, the new melt blown polypropylene is successfully used on the latest high-speed machine for mass production, and a large current is used to save charging time. In the later stage, the constant voltage charging can achieve a small current charging before the end of charging, which can not only ensure full charging, but also avoid the high temperature inside the super capacitor affecting the capacity characteristics of the super capacitor

this paper uses advanced microelectronics technology, MCU and power electronics technology to design and implement a new type of charging power supply for super capacitor modules after one year, including adjustable constant current charging and constant voltage charging circuit design, constant current and constant voltage conversion control circuit design, high-frequency transformer design and selection, power MOSFET selection, etc. The design of this project can effectively solve the problem that the charging voltage is not adjustable. At the same time, the adjustable charging current design can make the power supply adapt to the supercapacitor modules of different manufacturers and capacities

1 design of hardware circuit of charging power supply for super capacitor module

the framework diagram of charging power supply for super capacitor module is shown in Figure 1, which is mainly divided into six parts. They are: 1) EMC processing circuit; 2) Charging regulation circuit; 3) Charging control circuit; 4) Temperature acquisition circuit; 5) Power supply; 6) Status indication circuit

Figure 1 internal/external schematic diagram of super capacitor module charging power supply

1) EMC processing circuit

this circuit is mainly used to suppress the common mode interference and differential mode interference of charging power supply. For common mode interference, cy capacitor and common mode inductance L are used to suppress it. CX capacitor is used to suppress differential mode interference

2) charging regulation circuit

the regulation circuit is mainly to adjust the charging current and charging voltage. The adjustment circuit is adjusted by an adjustable potentiometer, and the adjusted partial voltage is divided into ADC_ I and ADC_ U. Two voltages enter the internal ADC in the microcontroller. The program samples the two partial voltage voltages to obtain the corresponding charging current setting value and charging voltage setting value

3) charging control circuit

the control part is mainly composed of MOSFET Power Tube Q, high-frequency converter T, corresponding square wave generator and voltage comparator. Resistors R1 and R2 sample the DC output voltage and compare it with the voltage setting signal output by microcontroller pwm1. If the DC output voltage exceeds the voltage setting value, turn off Q1 and stop charging the capacitor

resistance Rs samples the charging current, and the sampled voltage is compared with the pwm2 output current setting signal output by the microcontroller. If the charging current exceeds the set value, turn off Q1 and stop charging the capacitor. At the same time, the microprocessor collects either the supercapacitor temperature or the charging circuit temperature, and the microcontroller outputs t_ CTL signal, turn off Q1, stop charging the capacitor, and realize temperature protection

4) the temperature acquisition part

mainly has three temperature sensors T1, th, TC. T1 mainly collects the high-frequency transformer of the charging circuit, th collects the ambient temperature, and TC collects the temperature of the supercapacitor module for the external temperature sensor. The three temperature sensors adopt SPI data interface, and the microprocessor directly reads the temperature data. When the temperature exceeds the limit, the microprocessor outputs t_ CTL signal, turn off Q1, stop charging the capacitor, and realize temperature protection

5) the power supply part

is mainly composed of ac/dc module and LDO linear power supply. Ac/dc adopts wide input power module, which should have strong EMC resistance of bare metal. Because the ac/dc output voltage has a certain ripple, it cannot be directly supplied to the microprocessor for direct use. Therefore, a linear power supply is used to reduce the voltage and reduce the ripple of the power supply

6) the status indication part

is mainly composed of four light-emitting diodes, which respectively indicate the operation status of the power microprocessor, the charging status of the super capacitor, the overheating of the power supply or the external super capacitor, the overload of the power supply during charging, and other information

2 software function realization of super capacitor module charging power supply

Figure 2 software function realization main logic block diagram

the realization of the software function of this design is shown in Figure 2, which is divided into four parts: 1) data reading and parameter setting conversion logic; 2) Super capacitor temperature and temperature rise current control logic; 3) Capacitor charging control and overload protection; 4) Status indication control logic

Figure 3 block diagram of temperature and temperature rise current control

to protect the super capacitor during charging, as shown in Figure 3, this design calculates the temperature rise TWS of the super capacitor through the read super capacitor temperature TC and ambient temperature th. If the super capacitor temperature rise TWS has exceeded the working temperature rise tmaxw of the super capacitor limit, stop charging the super capacitor and directly set temphflag to 1. If the absolute temperature Tc of the super capacitor exceeds the maximum working temperature of the super capacitor, the charging of the super capacitor is also stopped, and temphflag is set to 1

if the temperature rise TWS and absolute temperature Tc are within the safe range, read the supercapacitor temperature rise current curve built into MCU through TWS, and read out the corresponding rechargeable current ITWS. If the set charging limit current icset is greater than the temperature rise current value ITWS, set icset to ITWS for charging, so as to prevent the life damage of super capacitor caused by excessive charging current

Figure 4 block diagram of capacitor charging and overload protection

as shown in Figure 4, this design first determines whether tempflag is 1. When tempflag is 1, it indicates that the data of temperature sensor has been read. Secondly, judge whether temphflag is 1. If temphflag is 1, it indicates that the absolute temperature or temperature rise of the super capacitor has exceeded the working limit of the super capacitor, and it cannot be charged at this time

then judge whether the charging control circuit is overloaded. The judgment of overload is mainly based on the temperature TK measured by the temperature sensor T1. If TK is greater than the built-in set value tkset, it indicates that the charging control circuit is overheated, and continued charging will cause damage to the charging circuit. At this time, set the overload flag to 1, indicating that the charging control circuit is overloaded and stops charging

after the above conditions are all OK, the logic again determines whether the setting parameters are read. If the parameter reading flag is normal, the pwm2 will be controlled to output a voltage according to icset to compare with the current of the charging circuit. The comparison process is completed by the voltage comparator A2 in part (c) of Figure 1

control pwm1 to output a voltage according to ucset to compare with the voltage of the charging circuit. The comparison process is completed by the voltage comparator A1 in part (c) of Figure 1 After the two settings are completed, part (c) of Figure 1 will automatically complete the current and voltage limiting charging process of charging, and set the charging flag chargeflag to 1 at the same time, so as to achieve a good effect. It is a very important problem that the super capacitor bank is being charged at this time

control t when charging is prohibited_ CTL directly turns off the and gate control signal in part (c) of Figure 1, so that the switch tube Q stops working, and the charging flag is 0

3 technical indicators of charging power supply design of super capacitor module

technical indicators of charging power supply design of super capacitor module and comparison with existing charging power supply schemes are shown in the table:

table 1 Technical target parameters of charging power supply of super capacitor module

Table 2 Comparison between the design of charging power supply of super capacitor module and the existing technical solutions

4 the advantages of charging power supply of super capacitor module

the advantages of charging power supply design of super capacitor module are as follows:

1) the charging voltage and charging current are adjustable, which can be applied to super capacitor banks with different capacity and voltage requirements, and the adjustable charging current is suitable for occasions with different charging time requirements for different super capacitor banks

2) fully consider the possible overload of the charging circuit, provide overheating self-protection, and avoid overload damage of the charging circuit caused by excessive charging current or frequent charging

3) the charging process takes into account the temperature characteristics of the super capacitor. The temperature rise current curve of the super capacitor is used to limit the charging. At the same time, monitor the super capacitor for excessive temperature rise and absolute temperature and stop charging, so as to avoid the rapid reduction of the service life of the super capacitor or explosion caused by the increase of temperature limit caused by continuous charging

5 conclusion

this design realizes the adjustable constant current charging and constant voltage charging circuit, realizes the automatic conversion function of constant current and constant voltage, and realizes the system protection function of capacitor module, which solves the problem that the general charging voltage of super capacitor module charging power supply in the market is designed as a fixed mode and cannot be adjusted

at the same time, due to the different capacity of different supercapacitor modules, the manufacturer's technical parameters are different, and the tolerance value of charging current is also different. Therefore, this design adopts the adjustable charging current design, which can make the power supply adapt to the supercapacitor modules of different manufacturers and different capacities

for the current super capacitor charging power supply is unable to charge the super capacitor in time? During charging, the temperature of the capacitor is too high due to too high ambient temperature, or the charging current is too large, resulting in the damage of the super capacitor. This design supports the temperature collection of the super capacitor module