microcontroller How does this power supply circuit work? (MCU + LM317)


Posted on Feb 5, 2014

The filter R1, R2 and C1 integrate the PWM waveform. But what is the point of the op-amp It looks like a non-inverting amplifier to me, with the gain set by R6 and R7 - if I`m not mistaken. But why does the integrated DC voltage need amplification Perhaps, I don`t understand that part because I don`t understand how the Lm317 is working in conjunction with the MCU.


microcontroller How does this power supply circuit work? (MCU + LM317)
Click here to download the full size of the above Circuit.

I understand that LM317 drops a reference 1. 25V between the OUT and ADJ pin (which should be across R5 in reference to the circuit) and the Vout is defined as 1. 25(1 + R2/R5) + I(adj. ) * R2. (from datasheet) Since the only variable is I(adj) in the above equation, am I correct in my understanding that the integrated DC voltage is actually changes the current and hence the output voltage




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