It is time to report on the Inductor saturation tester project. I have built a new version.
Duh ... ok, this is a bit of embarrassing
, I'm the who started this thread still haven't started anything yet, while you already built your 2nd one.
Low voltage operation, long pulse operation. The voltage applied to bridge was 0.7V
This ... exactly as I was expecting, with the low voltage, the trace is not straight anymore and becoming more like a curve, thanks a lot for this particular scope shot.
Also this makes me to put a note when designing the pcb to add a reserve space for more additional bulk caps just in case I will be doing lots of low voltage testing.
High speed 1us pulse. You see that one side of the bridge is delayed by about 300ns. For this screen shot 30V was applied to the bridge.
This one is interesting, but to be honest I'm lost, are you saying that when at the ON time, the lower fet was turned off late about 300ns compared to upper one ? A quick scratch on that shot using ms paint job to explain it if not troubling you too much.
JDB, as the pulse generator, my plan is to use the 555 as the oscillator (with pot for freq adj.) which generates a triangle, then this signal will serve as SYNC signal to the scope and also to a 311 comparator with pot for duty cycle adjustment. The noob question is, does the 311 output (with pull up resistor say 1 K) beefy enough to be connected to the input (R14) ? R13 will be omitted since its no longer needed.
R8 is going to dissipate a lot of power when your two-transistor over-curent SCR fires. You'd be better off using the SCR to pull the collector of Q4 low.
How much power is that ? As my EE wannabe calculation, that R8 (22 Ohm) should not dissipate more than 0.3 watt, CMIIW.
@PA4TIM
The one that JDB made here returns the rest of the inductor's energy back to the voltage source (bulk caps), so overall the circuit it self will consume quite low current as JDB previous post to proof that, of course with the exception of charging those bulk caps when powering them for the 1st time.
As strange as it sounds, like Janne said, this circuit is like a boost circuit but boosting it back to it self.