Snubber experiments

Don't take anything here as being 100% correct. Ask questions if you want me to explain anything. Snubbers protect the swithcing element by taking the power that usually dissipated on the element and dissipating it elsewhere. Turn-on snubber: 100uH and diode (with a 100Ohm series resistor) This circuit delays the current going into the NMOS until the voltage Vds becomes low (no / little current = low dissipated power on the NMOS). Turn-off snubber: Diode + capacitor + 100um mosfet When turning the mosfet off, the diode + capacitor help keep the Vds voltage to a low value (low Vds and high current = low dissipated power). The 100um mosfet is there just to reset the cap when resuming the cycle, it's cheaper to put a resistor there. The power will now dissipate on the 100Ohm resistor and the 100um mosfet, not on the switching element (the 1mm nMOS). So, any point on the upper right of the XY scope = high power = bad. Points in the lower left = low power = good. The RC lowpass in the switching element's gate is there only for simulation reasons, so we can see a smooth waveform.

published 11 years ago