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?

  1. 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?
  2. They just use a low speed ADC and the over-shoot/oscillations are compensated with passive components?
  3. The control loop is implemented with analog components and the ADC are only to the display the voltage to the user?
  4. They use an expensive high resolution and fast ADC?
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    \$\begingroup\$ "How is this done on commercial power supplies" - They don't use ADCs - get into the real world of switch mode power supplies and the analogue world LOL. OK then, number (3) in your question is the answer having re-read the question. \$\endgroup\$ – Andy aka Sep 23 '16 at 23:41
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    \$\begingroup\$ microchip.com/design-centers/intelligent-power/… \$\endgroup\$ – Bruce Abbott Sep 24 '16 at 2:18
  • \$\begingroup\$ "I would like to have a resolution in the output voltage of 10mV or 5mV" - why? \$\endgroup\$ – Bruce Abbott Sep 24 '16 at 2:19
  • \$\begingroup\$ I think many commercial units either don't care about the price of high end ADCs (why would they? Industry has deep pockets). But equally likely, is that the ADCs and DACs are used only as references, while opamps take care of the high speed control. Here's a simple opamp regulator - Vref goes to your DAC while Vout goes to your load and your ADC i.imgur.com/3I8izRo.png \$\endgroup\$ – Sam Sep 24 '16 at 6:47
  • \$\begingroup\$ Normally, (3). But like the idea of a digitally controlled solution. You could use a fast (but low resolution) ADC for the I and D terms, and a slow but high res one for the I term. \$\endgroup\$ – Brian Drummond Sep 24 '16 at 9:54

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