Faster, simpler switch controls
A demonstration board for CogniPower's patent-pending switch controls was shown for the
first time at the APEC Conference in February, 2009. We achieve
faster switching speeds for better efficiency, and use only marginally more than
the theoretic minimum power required for gate drive. Snubbing requirements can
be greatly reduced or even eliminated. Absence of overshoot allows lower voltage
switches to be employed for a given working voltage. Lower voltage parts are
smaller, faster, less expensive and more efficient. CogniPower switch controls
incorporate the power supplies, so no separate high-side supply is necessary.
The demonstration board pictured above can drive a totem pole switch built of
FETs or IGBTs. With FETs capable of 50 volts at 12 amps, the screen shot below
shows rise and fall times faster than 5000 volts per microsecond.
1 kW totem pole output swinging between 0 and 40 volts at 200 kHz without snubbing.
(1 µs/div, 10 V/div)
Another view of the waveform from the previous image, with the timescale set to
20 ns/div. Transition time is 7 ns and overshoot is less than 2%.
The negative transition time is 9 ns and undershoot is minimal.
More pictures of the totem pole switch