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Hardware Dead-Band (Compare Units only)
Motivation for Dead
Motivation for Dead
-
-
Band
Band
to motor phase
supply rail
Gate Signals are
Complementary PWM
♦ Transistor gates turn on faster than they shut off
♦ Short circuit if both gates are on at same time!
Dead-band control provides a convenient means of combating current shoot-through problems in
a power converter. Shoot-through occurs when both the upper and lower gates in the same phase
of a power converter are open simultaneously. This condition shorts the power supply and results
in a large current draw. Shoot-through problems occur because transistors open faster than they
close, and because high-side and low-side power converter gates are typically switched in a
complimentary fashion. Although the duration of the shoot-through current path is finite during
PWM cycling, (i.e. the closing gate will eventually shut), even brief periods of a short circuit
condition can produce excessive heating and over stress in the power converter and power supply.
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