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53 Threads found on Turnoff
Sure. But how you'd do it, will depend on details of what you want from this. You could cut power (a load switch IC or two) and this would save a fair bit of current from the quiet VCO supply. But there are issues with the turnon and turnoff behaviors, are there chirps and pops on audio or radio (whatever the application might be)? How long doe
Appears that both supplies have an externally asserted, hard turnoff (maybe the battery-drop, but maybe some other "feature" of the power supply controller(s). A question right off the top is, when you add the "large capacitor" does the discharge ramp look like dV/dt=Ioperating/Cbigfat, or is it getting jammed to ground by some external, much l
The B-E shunt resistor is responsible (or partly so) for turnoff speed as a saturated switch. Do you care about LH risetime at the collector node? If so, characterize or find data for max temp, max "on" base drive, min Vce(sat) switching w.r.t. the base network impedance.
The problem is not the control circuit, it's the hard chop at turnon (turnoff ought to be zero current / voltage -ish). Since heater is probably not very fussy about how the power comes, maybe you could get to a "pulse skip" mode where you turn on "right after" zero crossing, ride the half-cycle up and back down until quench, then either do it
No, switching speed at turnoff goes directly to how much magnetizing energy is left in the inductor to produce the flyback pulse Theoretically, yes. In practice, the ignition coil SRF (plus an connected external capacitor) sets a limit to current and respective voltage speed of change. As long as the switch is acting faster, the
Have you connected the transformer drain ? If not it may sense as no feedback. If yes check the feedback section in the LM324. transformer drain means connected to the transformer , Yes connected ,And works for one or more second and goes the error "No feedback " then the output will turnoff. I checked LM324 s
About losses in the transitions: do you need to meet given rise and fall times? Maybe resistors to the MOS gate are too high. I think just reducing R9 from 30 to 10k will still give adequate Vgs to turn the transistor on, but its turnoff time will be reduced by speeding up Cgs discharge.
Your first circuit is very weak, 9.1Kohms is way out of line for anything but a small signal FET. Also the collector resistance in the opto will limit swing to half the supply and you will likely saturate the opto BJT leading to large turnoff delay. In both cases the FET Cdg (Miller) will make drain transitions very slow. Solve Vsupply/(9.1K/2)=
A few options to consider - - for turnon, consider emitter-denegerating the NPN (say, with 100 ohms - making 3.3V drive produce a bit under 30mA DC). Could supplement with a shunt cap for a high peak turnon current but still a limited steady state, which the zener could tolerate. But if you ratio the emitter resistor and the FET gate shunt resis
Undervoltage lockout being tickled by weak mains, poor socket connection or a PFC front end problem? Thermal protection toggling due to a die or board level heat issue? Control loop instability? Noise issue w/ current mode control at low duty cycles is often a problem, with the turnoff edge coming close to turnon the switch "ringing tail" ma
What you probably want, is to measure each shunt at two timepoints, one where the result is "zero" (like, switch is off, right before next turnon) and then another where the voltage is significant and most stable (dead quiet in a switcher, ain't gonna happen - but pick the best, perhaps right before switch turnoff). There exist integrated shunt-a
I think you may want to look at transformer styles and not just the classical boost (inductor) type. Boost efficiency suffers badly at high ratios of VOUT/VIN. To operate at such low voltage you also will likely oversize your FET and its added C steals from inductor current delivery at turnoff. If you make your voltage gain using windings ratio yo
Most DC fans are brushless with an internal control IC and their behavior may or may not be inductive at turnoff; depends on the controller behavior. I'd suggest trying to measure the response, and make the fan's power and ground have as little as possible to do with the uC's power and ground (the ground, especially; the regulator for uC ought t
"Can"? Sure. Especially in an amplifier that happens to be close to its ideal Vio but within a wider spec window, on competing defects these "features" can exhibit differing tempcos individually and in sum. Autozeroed amplifiers that use charge storage to null the front end, can see drifts in the zeroing from drifts in the switch timing and char
I don't believe, offhand, that putting the switch in any particular place will eliminate pedestal errors. These come in right at the time where you are breaking the loop (in a THA) and they relate to gate charge imbalance (and, where the gate charge displacement currents go, as you choke off the channels). Things like the amount of gate turnoff ov
If you don't have access to the optocoupler base then a Baker or Schottky clamp can't do anything for you. You might want to determine whether the turnoff is due to internal saturation of the opto, to the simple gate RC and distance-to-fall of the PMOS gate load, etc. and maybe that will guide you. Sizing the PMOS, using a small signal fast PNP
The capacitor in parallel with the Triac/coil is not damped (it doesn't have a series resistor) Therefore you have a large-Q tank circuit, which will oscillate wildly at turnoff. This could exceed the internal clamp ratings. I know that the datasheet indicates that no external snubbing or clamping is necessary. But desperate problems require desp
Do not combine the solenoid power with the MOSFET power, this is irrelevant to everyone except the source power supply. Your cases are four: "off" - Ileak*Vsupply "on" - (Vsupply/Rcoil)^2*Rds(on) - assume Vds close enough to zero "turnon" - integral power of Id*Vds across the turnon transition, against pulsed peak power for single edge and ag
My best guess is the strange shape of Vds is due to the nature of that particular GaN FET. Its datasheet shows a turnoff delay of 33ns, and the Coss is incredibly nonlinear. This means the rise of Vds should be somewhat sluggish. Hard to tell if it's reasonable since you don't show the time axis in your waveforms.
I designd a AC-DC converter 12v, 2Amps. connected to battery(12v, 1.3Ah). Once if its charge completely it should be auto turnoff and reccharge again for a period of some time. help me out.