[Current Regulator] Working « prototype » (en)


I have a working prototype of the current regulator. If you took a look at the previous post, I implemented a totem pole because of some stability problem on the Mosfet switching. It’s always a good idea to drive Power Mosfet with this kind of circuitry if you use an uC. But in that case it was not a Gate capacitance problem. It was a simple problem of decoupling capacitors… I forgot to put some caps on the Vcc rail, on the first switching the current was too high to keep a stable 5V Vcc, you can imagine…

+5V -> Switch -> Reset -> +5V -> Switch -> Reset

Without Totem-Pole

First Pic \o/

For the moment I don’t have wired the Operationnal Amplifier. I just implemented the PWM part (for the pic18 and dspic version).  For information here is the Voltage ripple measure with this version (no totem-pole).

Blue Line: Vout A.C. Coupling

Yellow Line: Mosfet Gate

The rise time is about 800 ns with some ripple on the Vout (200mV approx.)

With Totem-Pole

I didn’t take a picture for this version, it’s a really messy bunch of wires ;) But here is the schematic (you can find the ltspice on my repository).

This one is working too with decoupling capacitors, if you don’t put them there will be some transient problem and the uC will sometimes be stuck in the reset loop of hell.

The scale is different but you can see, the ripple is less present and the rising edge of the PWM is clean without ringing in the top side.

Next Step

PCB etching seems to be a good idea \o/
There will be an integration in the XPLDuino project ! Take a look we are waiting for the new mainboard ;)

If you want all the data for this project you can get files here.

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