Amplifiers – With semiconductor amplifying device – Including class d amplifier
Reexamination Certificate
1999-11-16
2001-07-17
Lee, Benny (Department: 2817)
Amplifiers
With semiconductor amplifying device
Including class d amplifier
C330S20700P
Reexamination Certificate
active
06262632
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
Cross reference is made to the commonly assigned copending patent application entitled “Modulation Scheme for Filterless Operation of Switching Amplifiers”, the teaching of which are incorporated herein by reference.
FIELD OF THE INVENTION
The present invention is generally related to amplifier circuits, and more particularly to Class-D switching amplifiers.
BACKGROUND OF THE INVENTION
One method to achieve filterless Class-D switching amplifier operation, increased efficiency, and reduced cost is to deliver current to the load only when needed, and once delivered, maintain the current without decaying or wasting energy in removing the current. This can be accomplished by using a ternary modulation scheme implemented in an H-bridge configuration having four states of operation as shown in
FIG. 1
,
FIG. 2
, FIG.
3
and
FIG. 4
as disclosed in commonly assigned copending patent application entitled “Modulation Scheme for Filterless Switching Amplifiers”, filed herewith, the teachings of which are incorporated herein by reference. Voltage and current waveforms are shown in FIG.
5
and
FIG. 6
for analog input into the amplifier.
In the presence of an input signal, the waveforms change as shown in
FIG. 6
in view of FIG.
5
. The edges of the OUTP waveform
12
move away from each other, and the edges of the OUTN waveform
14
move towards each other. The voltage difference of these two signals
12
and
14
, which appears across a load shown as L
1
, generate narrow pulses as shown at
15
of waveform
16
. These pulses
15
also have the desired affect of doubling the single-ended PWM frequency. Current does decay as the speaker as a load and MOSFETS are lossy, as shown as waveform
18
. If the polarity of the input signal is reversed, the edges of OUTN (
14
) move away from each other and the edges of OUTP (
12
) move towards each other.
There is desired a signal processing scheme for the signals just described above.
SUMMARY OF THE INVENTION
The present invention achieves technical advantages as a signal processing circuit adapted for use within a Class-D amplifier that introduces a time-delay in control signals to move a susceptible crosstalk point away from a zero-crossing point to a higher power level.
One circuit and method provides circuitry that adds a time delay to one ramp waveform processed by a first comparator, while providing an non-delayed ramp waveform to a second comparator for processing. In this manner, switching of one-half the circuit will not couple disturbances into the output of the other half of the circuit, thereby making sure that signals generated do not trip circuitry prior to an expected zero crossing point.
The present invention achieves technical advantages in situations where zero-crossing of audio signals are smallest and are most likely to exist.
REFERENCES:
patent: 3946273 (1976-03-01), Goddard
patent: 4162455 (1979-07-01), Birt
patent: 4356432 (1982-10-01), Vinarub
patent: 4949048 (1990-08-01), Tokumo et al.
patent: 5014016 (1991-05-01), Anderson
patent: 5307407 (1994-04-01), Wendt et al.
Arcudia Kenneth
Chen Wayne Tien-Feng
Corsi Marco
Jones, III Roy Clifton
Mavencamp Dan
Brady III Wade James
Choe Henry
Lee Benny
Neerings Ronald O.
Telecky , Jr. Frederick J.
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