Umm ! I could not decide a better title .
The Picture shows a part of PSU I designed. It's a CC, CV one. 0-35V @ 10mA to 2A continues. 3 Amps peak.
I do not have a problem with the circuit. Just a basic question about the ADC part.
As you can see I am using Low side sensing for the current limiter and measuring the current from high side was not accomplished since I cannot get the component I wanted.
The output GND is not the same as the Main GND, due to low side CS resistor. And the PIC ADC negative reference is the main GND.
The V, I sensing is buffered by the BB OPAMPS.
The Current buffer IC5 is used with gain as the CS voltage drop is lower. I needed 5V output at 3A. That part is done.
Now since the -Vref is at GND, ADC (v+), which measures the output Voltage, varies as load current varies even thought the Main Output remains stable. The Variation is in mV which is the result of current sense resistor drop. So I decide to measure the difference between Vout and CS voltage drop. When simulated the voltage is constant.
I decide not use a differential amp ( to minimize components and board space, which is limited), instead use 2 ADC to measure the difference. Which resulted in ADC (V+) and ADC (V-).
I believe this will work with extra coding.
My Question is,
When to convert the ADC values to voltage ?
Should I first Subtract raw ADC(V+) from ADC(V-) and convert them to Voltage to be displayed or Convert the 2 ADC values to Voltage and do the subtraction and send to LCD?
Never done this before so I am asking around which method is better.
The Picture shows a part of PSU I designed. It's a CC, CV one. 0-35V @ 10mA to 2A continues. 3 Amps peak.
I do not have a problem with the circuit. Just a basic question about the ADC part.
As you can see I am using Low side sensing for the current limiter and measuring the current from high side was not accomplished since I cannot get the component I wanted.
The output GND is not the same as the Main GND, due to low side CS resistor. And the PIC ADC negative reference is the main GND.
The V, I sensing is buffered by the BB OPAMPS.
The Current buffer IC5 is used with gain as the CS voltage drop is lower. I needed 5V output at 3A. That part is done.
Now since the -Vref is at GND, ADC (v+), which measures the output Voltage, varies as load current varies even thought the Main Output remains stable. The Variation is in mV which is the result of current sense resistor drop. So I decide to measure the difference between Vout and CS voltage drop. When simulated the voltage is constant.
I decide not use a differential amp ( to minimize components and board space, which is limited), instead use 2 ADC to measure the difference. Which resulted in ADC (V+) and ADC (V-).
I believe this will work with extra coding.
My Question is,
When to convert the ADC values to voltage ?
Should I first Subtract raw ADC(V+) from ADC(V-) and convert them to Voltage to be displayed or Convert the 2 ADC values to Voltage and do the subtraction and send to LCD?
Never done this before so I am asking around which method is better.