amount. Class-I uses symmetrical interleaved PWM, meaning both the leading edges and trailing edges of the pulse are varied according to the amplitude of the signal, and the spacing between pulse centers remains constant. Both the positive and negative switch pulses remain aligned on-center, and the net output current is positive.
Class-I Switches, Positive Signal
Likewise, to produce a negative output signal, the output of the negative switching device is increased in duty while the positive switching device is decreased by the same amount. Again, both switch pulses remain aligned on-center, and the net output current is negative.
Class-I Switches, Negative Signal
The result of using interleaved PWM is that by operating the switching devices at 250 kHz, the signal is effectively modulated at 500 kHz since both the leading and trailing edges of each pulse contribute to the output ripple current. This arrangement further increases efficiency, since switching losses are effectively halved by operat- ing the switching devices at 250 kHz, rather than at 500 kHz as would be necessary with class-D designs to achieve the same effective sampling of the waveform.
Class-I amplifiers also have all of the nearly ideal power converter attributes of class-D PWM amplifiers, in that reactive loudspeaker loads are easily driven. The reac-
tive energy returned from the loudspeaker to the ampli- fier is reabsorbed and output again to the loudspeaker with little loss. Non-switching, dissipative amplifiers are forced to dissipate all of the returned energy and more in the form of heat. This means class-I amplifiers are louder than other amplifiers with comparible power specs, yet they stay much cooler, and can be lighter since they don’t need nearly as much mass for heat dissipation.
Class-I Amplifier
Reactive Energy
Dissipative Amplifier
Reactive Energy
Reactive Energy Returned to Amplifier
From Loudspeaker
With it’s rock-solid reliability, high quality audio repro- duction and unmatched efficiency, Crown’s patented class-I technology creates a totally new paradigm for amplifier design that represents the future of profes- sional amplifiers.
Crown Audio, Inc.
P.O. Box 1000
Elkhart, IN 46515-1000
TEL: 219-294-8200
FAX:219-294-8FAX
www.crownaudio.com
Trademark Notice:
Crown® and BCA® are registered trademarks of Crown International. Printed in U.S.A.
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