How to design a constant current source controller using the C8051FF330D microcontroller

      In the rapidly developing electronic and telecommunication technology systems, the quality of the power supply determines the performance and life of telecommunication equipment to a certain extent. Although the digital control constant voltage technology on the market is relatively mature, digital control voltage source products have also developed towards the trend of intelligence and miniaturization, and the price is getting cheaper and cheaper.

Tools/Raw Materials

• C8051FF330D microcontroller, JTAG interface, LED digital tube, circuit diagram, keyboard
   

Steps/Methods

1. The overall structure of the system: The 10-bit current-type digital-to-analog converter and current/voltage conversion circuit inside the C8051FF330D microcontroller are used to output an analog value of 0 to 4 V, and then this voltage signal is used to control the output current of the constant current source so that it changes according to a given value.
    
2. Output interface circuit: The 0-1 mA current signal output by the digital-to-analog converter in the internal circuit of C8051F330D is converted into a 0-2 V voltage signal through a reference resistor, and then converted into a 0-4 V standard signal output through an amplifier circuit. The analog output signal conversion circuit is shown in the figure.
   
   
    
3. Power-off protection circuit: To prevent the system from powering off, this design uses FM24CL04 as a non-volatile memory to protect system parameters and other intermediate data. Unlike EEPROM, FM24CL04 can be written at bus speed. It uses an industrial standard two-wire I2C interface. Figure 3 shows the power-off data protection circuit included with this power system.
    
4. Keyboard and display circuit; Using ZLG7290B dedicated chip can also simplify circuits and programs, and reduce the debugging burden of circuits. Moreover, as an industrial-grade display driver chip, ZLG7290B also has strong anti-interference ability. Figure 4 shows the schematic diagram of the keyboard and display driver circuit composed of C8051F330D microcontroller and ZLG7290B dedicated display driver chip.
    
5. Main program design: C language is used for software design to realize various functions of the system. The system application adopts modular structure design, mainly including main program, parameter call modification subroutine, DAC0 initialization program, etc. Figure 5 shows the main program flow chart.
    
6. Module function programming:
   Void DAC_Init (void)
   　　{
   　　REF0CN =0X30; /*Internal bias generator and voltage reference buffer work, reference is output from VREF pin*,
   　　ID0CB =0XF2;
   　　}
   　　The memory write function is as follows:
   　　Viod EEPROM_ByteWrite ( uchar i2caddr,uchar addr, uchar dat )
   　　{
   　　While (smb_busy)
   　　Smb_busy = 1;
   　　Target = i2caddr;
   　　Smb_w =write;
   　　Smb_sendwordaddr = 1;
   　　Smb_randomread = 0;
   　　Smb_ackpoll =1;
   　　Word_addr = addr;
   　　Smb_singlebyte_out = dat;
   　　Psmb_data_out =&smb_singlebyte_out;
   　　Smb_data_len =1;
   　　Sta = 1;
   　　}
   　　……
   
    

Precautions

• Be sure to follow the above steps during the production and configuration process
   
• After the final success, some debugging is still required