Various aspects of home brew inverters

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dreamth Newbie Joined: 03/11/2017 Location: Romania Posts: 2	Posted: 12:35pm 04 Nov 2017         Warpspeed said   I just placed a short across R27, the C30 capacitor I suspect, is just there to block any high frequency noise. Its not critical, and could be removed. With R27 bridged, the Ifb now instantly turns off the IR driver chip, and when Ifb falls below the threshold the PWM soft starts via software, its not C30 providing the soft start action. It soft starts very gently just as it normally does at initial power up. With R27 removed, Ifb only works on the enable pin of the IR driver chip, and its a very sudden and violent all or nothing on/off action. I have no idea why R27 was removed. The way I have done it, is to use the SCR latching circuit others here are using that turns off the PWM pretty fast. Then wire a normally open push button directly across the SCR as an over current reset button. When reset is pushed, the system soft starts, but only if R27 is bridged. Pushing this reset button at any time instantly shuts down the PWM, and it soft starts back up again. Many ways to skin the Ifb cat... I think that , if you place r27 you still have some time constants given by r27/r10/c30 on one side and r4/c19/r26. c19 is missing on some boards, has values spread between 1nf to 10nf on various schematics along with different values for r4. one of my boards has 2nf, the other nothing , the same r4 and r26 (100k)is there to speed up the op-amp comparator that shuts down the IR2013. Maybe IR2113 is supposed to be on/off very quickly,but c19 should tame it or just keep it clean . I understand now that when ifb voltage at pin 14 is up due to high current , eg8010 stops suddenly, maybe even faster than IR2113 as there's another op-amp in between the ifb signal and SD pins of IR2113. If R27 would be there, spwm could have several restarts as there's no histerezis on the U4b op-amp that gives the spwm signal with a short r27 and no meaningfull value for c30 and anyway that would mean aditional delay to the internal delay of spwm. So they completly removed that r27 and saved the cat. I think either i will go with no IFB , pin 6 of u4 grounded through that 1k of R7 resitor and power up and down straight from 5v power supply, either i would use the ifb or tfb to power up/down and keep the IFB out of the system. TFB has it's own delay while Ifb allows it. For 60ma there should be no other problem, but accidental overvoltage and a transformer separatin should save me some boards.So i'm looking now how to better separate the drive from the output. Edited by dreamth 2017-11-05