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Digitally controlled DCDC converter
1 Introduction :
This design is a digital control DCDC converter . MCU is used to control the output voltage of the DCDC converter to achieve the purpose of digital control . Considering the time and cost , finished modules are used for verification . This design idea has the advantages of simplicity, reliability, low cost and high flexibility .
The function to be realized is to control the output voltage of the DCDC module by pressing buttons , and digitally display the voltage and current values .
Use the modules as follows :
Main control MCU: GD32E231start development board .
DCDC module : XL6009 buck-boost module .
Current measurement : MAX471 current measurement module .
Button : TTP224 capacitive touch button module .
Display : TM1638 digital tube module .
2 System Block Diagram :
3 Explanation of each part :
Because this design uses modules and the circuits are rarely modified , no PCB board is made during the design and verification stage . The circuit diagram is not drawn . If the performance and accuracy need to be improved later , the PCB will be made as needed .
The figure below shows the load , voltage 4.88V, current 1.007A.
1) Main control MCU: GD32E231 is selected , a new domestic product with high main frequency , low power consumption m23 core , rich peripherals and resources , and simple and easy-to-use development software . It has a very high cost performance . In this design , the CH2 channel PWM function of the MCU 's timer2 is used to generate a PWM wave on the PB0 pin . After filtering by resistors and capacitors , it is loaded to the FB end of the XL6009 on the DCDC module to change the FB voltage . The XL6009 adjusts the DCDC and changes the output voltage so that the FB end is stabilized at the FB potential again , thus achieving the purpose of digital control to adjust the output voltage . Because most DCDC chips adjust the output through FB , this method can be used with a wide range of DCDC chips . However, since the PWM is not clean after RC filtering , it is not conducive to the stability of the DCDC output .
2) DCDC: Select XL6009 finished module to form a sepic circuit , which has the ability to step up and down , a wide input and output range , input 5~20V, output to 3~21V. Because it is a sepic mode , there is no need to consider whether the input and output are step-up or step-down . Its performance efficiency is not very good , but the cost is very low and the structure is simple , which is very suitable for verification of this design .
3) Measurement : For voltage measurement, just use a voltage divider resistor and enter the MCU 's ADC for sampling . Current measurement is divided into high-side and low-side measurement . The low side needs to split the ground line and debug the op amp. In fact , it is more suitable for GD32E231 because it has a built-in op amp , but the problem is that it shares pins with the SWD debug port , so I dare not use it for the time being . I have a common MAX471 current measurement module on hand . This is a high-side amplifier with a wide range of applicable voltages and built-in sampling resistors , and its performance is guaranteed .
4) Display : Considering the simplicity and low cost , the TM1638 digital tube module is used . It is simple and convenient to use . The first four digits of the eight digital tubes display the voltage value , and the last four digits display the current value . The voltage value takes two decimal places , and the current value takes three decimal places. 3.3V voltage can also drive well .
5) Buttons : The ordinary buttons that come with the TM1638 module are not used , otherwise it can be considered cost optimization . The TTP224 touch button module is selected , which is very simple to use and low cost .
4 Videos :
Link : https://training.eeworld.com.cn/video/20784
5Source code and documentation :
Development software IAR, source code :
数控DCDC转换器.zip
(6.51 MB, downloads: 2054)
Document :
数控DCDC转换器.doc
(718.03 KB, downloads: 17)
6 Feelings :
1) GD32E231 has powerful performance , rich resources , easy to use , and the firmware library is also simple and easy to use , with a very good cost performance . Due to time and energy constraints , this design did not take much time , but it was successfully implemented and verified . There were no major problems during the development process .
2) The design does not pursue good performance , but focuses on cost control and considers productization later .
3) The performance issues are mainly voltage accuracy and stability , which depends on the performance of the DCDC chip . On the other hand , using PWM for control will introduce ripples into FB, which is very unfavorable for output stability . Therefore, it may be necessary to use an op amp to actively filter the PWM wave .
4) If the low-side current is used , the built-in op amp is used , the cost is more optimized , but unfortunately it will affect SWD debugging , which is not good in the design stage and requires careful testing .
5) XL6009 is a commonly used DCDC chip , which verifies that this solution is feasible , but the current and efficiency are not too high . Therefore, XL6019 or a four-tube buck-boost chip can be used , but the cost will also increase .
In short , I would like to thank eeworld and GigaDevice for hosting this design competition. I am very happy to have the opportunity to try out new domestic products . Due to time constraints , there are still many details and performances in the design that need to be improved . I will continue to improve them in the future .
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变色卡
千斤顶
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