I'm designing a digital lab power supply for the sake of learning and also because I need one lol. I'm planning to use a simple 50Hz transformer with a Buck converter (I know this brings switching noise and that a linear solution would be much cleaner in terms of noise but I don't want big heatsinks) so I will be implementing a PID controller with a dsPIC sampling at about 1MSPS.
The dsPIC only has 10 bit ADC which also isn't the best ADC and I would like to have a resolution in the output voltage of 10mV or 5mV so for this I would need a higher resolution and better external ADC like a 16 or 14 bit ADC. The problem with this ADCs is that they are really slow (1 to 10KSPS) so I can't implement my control loop with this.
How is this done on commercial power supplies?
- They use a lower resolution and faster ADC to implement the control loop to prevent over-shoot and then when the output is settled read from the high resolution ADC which is also the voltage displayed to the user?
- They just use a low speed ADC and the over-shoot/oscillations are compensated with passive components?
- The control loop is implemented with analog components and the ADC are only to the display the voltage to the user?
- They use an expensive high resolution and fast ADC?